third_party: Add libunwind (#1053)

Added libunwind from LLVM 17.0.6.
The library includes functions required for C++ exception handling.

Makefile

@@ -328,6 +328,7 @@ include third_party/python/BUILD.mk
 include tool/build/BUILD.mk
 include tool/curl/BUILD.mk
 include third_party/qemu/BUILD.mk
+include third_party/libunwind/BUILD.mk
 include examples/BUILD.mk
 include examples/pyapp/BUILD.mk
 include examples/pylife/BUILD.mk

third_party/BUILD.mk

@@ -17,6 +17,7 @@ o/$(MODE)/third_party:				\
 	o/$(MODE)/third_party/hiredis		\
 	o/$(MODE)/third_party/less		\
 	o/$(MODE)/third_party/libcxx		\
+	o/$(MODE)/third_party/libunwind		\
 	o/$(MODE)/third_party/linenoise		\
 	o/$(MODE)/third_party/lua		\
 	o/$(MODE)/third_party/lz4cli		\

third_party/libunwind/AddressSpace.hpp

@@ -0,0 +1,697 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// Abstracts accessing local vs remote address spaces.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __ADDRESSSPACE_HPP__
+#define __ADDRESSSPACE_HPP__
+
+#include "libc/isystem/stdint.h"
+#include "libc/stdio/stdio.h"
+#include "libc/stdlib.h"
+#include "libc/isystem/string.h"
+
+#include "third_party/libunwind/include/libunwind.h"
+#include "third_party/libunwind/config.h"
+#include "third_party/libunwind/dwarf2.h"
+#include "third_party/libunwind/EHHeaderParser.hpp"
+#include "third_party/libunwind/Registers.hpp"
+
+#ifndef _LIBUNWIND_USE_DLADDR
+  #if !(defined(_LIBUNWIND_IS_BAREMETAL) || defined(_WIN32) || defined(_AIX))
+    #define _LIBUNWIND_USE_DLADDR 1
+  #else
+    #define _LIBUNWIND_USE_DLADDR 0
+  #endif
+#endif
+
+#if _LIBUNWIND_USE_DLADDR
+#include <dlfcn.h>
+#if defined(__ELF__) && defined(_LIBUNWIND_LINK_DL_LIB)
+#pragma comment(lib, "dl")
+#endif
+#endif
+
+#if defined(_LIBUNWIND_ARM_EHABI)
+struct EHABIIndexEntry {
+  uint32_t functionOffset;
+  uint32_t data;
+};
+#endif
+
+#if defined(_AIX)
+namespace libunwind {
+char *getFuncNameFromTBTable(uintptr_t pc, uint16_t &NameLen,
+                             unw_word_t *offset);
+}
+#endif
+
+#ifdef __APPLE__
+
+  struct dyld_unwind_sections
+  {
+    const struct mach_header*   mh;
+    const void*                 dwarf_section;
+    uintptr_t                   dwarf_section_length;
+    const void*                 compact_unwind_section;
+    uintptr_t                   compact_unwind_section_length;
+  };
+
+  // In 10.7.0 or later, libSystem.dylib implements this function.
+  extern "C" bool _dyld_find_unwind_sections(void *, dyld_unwind_sections *);
+
+namespace libunwind {
+  bool findDynamicUnwindSections(void *, unw_dynamic_unwind_sections *);
+}
+
+#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
+
+// When statically linked on bare-metal, the symbols for the EH table are looked
+// up without going through the dynamic loader.
+
+// The following linker script may be used to produce the necessary sections and symbols.
+// Unless the --eh-frame-hdr linker option is provided, the section is not generated
+// and does not take space in the output file.
+//
+//   .eh_frame :
+//   {
+//       __eh_frame_start = .;
+//       KEEP(*(.eh_frame))
+//       __eh_frame_end = .;
+//   }
+//
+//   .eh_frame_hdr :
+//   {
+//       KEEP(*(.eh_frame_hdr))
+//   }
+//
+//   __eh_frame_hdr_start = SIZEOF(.eh_frame_hdr) > 0 ? ADDR(.eh_frame_hdr) : 0;
+//   __eh_frame_hdr_end = SIZEOF(.eh_frame_hdr) > 0 ? . : 0;
+
+extern char __eh_frame_start;
+extern char __eh_frame_end;
+
+#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
+extern char __eh_frame_hdr_start;
+extern char __eh_frame_hdr_end;
+#endif
+
+#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
+
+// When statically linked on bare-metal, the symbols for the EH table are looked
+// up without going through the dynamic loader.
+extern char __exidx_start;
+extern char __exidx_end;
+
+#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_WIN32)
+
+#include <windows.h>
+#include <psapi.h>
+
+#elif defined(_LIBUNWIND_USE_DL_ITERATE_PHDR) ||                               \
+      defined(_LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX)
+
+#include <link.h>
+
+#endif
+
+namespace libunwind {
+
+/// Used by findUnwindSections() to return info about needed sections.
+struct UnwindInfoSections {
+#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) ||                                \
+    defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND) ||                              \
+    defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
+  // No dso_base for SEH.
+  uintptr_t       dso_base;
+#endif
+#if defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
+  size_t          text_segment_length;
+#endif
+#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+  uintptr_t       dwarf_section;
+  size_t          dwarf_section_length;
+#endif
+#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
+  uintptr_t       dwarf_index_section;
+  size_t          dwarf_index_section_length;
+#endif
+#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
+  uintptr_t       compact_unwind_section;
+  size_t          compact_unwind_section_length;
+#endif
+#if defined(_LIBUNWIND_ARM_EHABI)
+  uintptr_t       arm_section;
+  size_t          arm_section_length;
+#endif
+};
+
+
+/// LocalAddressSpace is used as a template parameter to UnwindCursor when
+/// unwinding a thread in the same process.  The wrappers compile away,
+/// making local unwinds fast.
+class _LIBUNWIND_HIDDEN LocalAddressSpace {
+public:
+  typedef uintptr_t pint_t;
+  typedef intptr_t  sint_t;
+  uint8_t         get8(pint_t addr) {
+    uint8_t val;
+    memcpy(&val, (void *)addr, sizeof(val));
+    return val;
+  }
+  uint16_t         get16(pint_t addr) {
+    uint16_t val;
+    memcpy(&val, (void *)addr, sizeof(val));
+    return val;
+  }
+  uint32_t         get32(pint_t addr) {
+    uint32_t val;
+    memcpy(&val, (void *)addr, sizeof(val));
+    return val;
+  }
+  uint64_t         get64(pint_t addr) {
+    uint64_t val;
+    memcpy(&val, (void *)addr, sizeof(val));
+    return val;
+  }
+  double           getDouble(pint_t addr) {
+    double val;
+    memcpy(&val, (void *)addr, sizeof(val));
+    return val;
+  }
+  v128             getVector(pint_t addr) {
+    v128 val;
+    memcpy(&val, (void *)addr, sizeof(val));
+    return val;
+  }
+  uintptr_t       getP(pint_t addr);
+  uint64_t        getRegister(pint_t addr);
+  static uint64_t getULEB128(pint_t &addr, pint_t end);
+  static int64_t  getSLEB128(pint_t &addr, pint_t end);
+
+  pint_t getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
+                     pint_t datarelBase = 0);
+  bool findFunctionName(pint_t addr, char *buf, size_t bufLen,
+                        unw_word_t *offset);
+  bool findUnwindSections(pint_t targetAddr, UnwindInfoSections &info);
+  bool findOtherFDE(pint_t targetAddr, pint_t &fde);
+
+  static LocalAddressSpace sThisAddressSpace;
+};
+
+inline uintptr_t LocalAddressSpace::getP(pint_t addr) {
+#if __SIZEOF_POINTER__ == 8
+  return get64(addr);
+#else
+  return get32(addr);
+#endif
+}
+
+inline uint64_t LocalAddressSpace::getRegister(pint_t addr) {
+#if __SIZEOF_POINTER__ == 8 || defined(__mips64)
+  return get64(addr);
+#else
+  return get32(addr);
+#endif
+}
+
+/// Read a ULEB128 into a 64-bit word.
+inline uint64_t LocalAddressSpace::getULEB128(pint_t &addr, pint_t end) {
+  const uint8_t *p = (uint8_t *)addr;
+  const uint8_t *pend = (uint8_t *)end;
+  uint64_t result = 0;
+  int bit = 0;
+  do {
+    uint64_t b;
+
+    if (p == pend)
+      _LIBUNWIND_ABORT("truncated uleb128 expression");
+
+    b = *p & 0x7f;
+
+    if (bit >= 64 || b << bit >> bit != b) {
+      _LIBUNWIND_ABORT("malformed uleb128 expression");
+    } else {
+      result |= b << bit;
+      bit += 7;
+    }
+  } while (*p++ >= 0x80);
+  addr = (pint_t) p;
+  return result;
+}
+
+/// Read a SLEB128 into a 64-bit word.
+inline int64_t LocalAddressSpace::getSLEB128(pint_t &addr, pint_t end) {
+  const uint8_t *p = (uint8_t *)addr;
+  const uint8_t *pend = (uint8_t *)end;
+  uint64_t result = 0;
+  int bit = 0;
+  uint8_t byte;
+  do {
+    if (p == pend)
+      _LIBUNWIND_ABORT("truncated sleb128 expression");
+    byte = *p++;
+    result |= (uint64_t)(byte & 0x7f) << bit;
+    bit += 7;
+  } while (byte & 0x80);
+  // sign extend negative numbers
+  if ((byte & 0x40) != 0 && bit < 64)
+    result |= (-1ULL) << bit;
+  addr = (pint_t) p;
+  return (int64_t)result;
+}
+
+inline LocalAddressSpace::pint_t
+LocalAddressSpace::getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
+                               pint_t datarelBase) {
+  pint_t startAddr = addr;
+  const uint8_t *p = (uint8_t *)addr;
+  pint_t result;
+
+  // first get value
+  switch (encoding & 0x0F) {
+  case DW_EH_PE_ptr:
+    result = getP(addr);
+    p += sizeof(pint_t);
+    addr = (pint_t) p;
+    break;
+  case DW_EH_PE_uleb128:
+    result = (pint_t)getULEB128(addr, end);
+    break;
+  case DW_EH_PE_udata2:
+    result = get16(addr);
+    p += 2;
+    addr = (pint_t) p;
+    break;
+  case DW_EH_PE_udata4:
+    result = get32(addr);
+    p += 4;
+    addr = (pint_t) p;
+    break;
+  case DW_EH_PE_udata8:
+    result = (pint_t)get64(addr);
+    p += 8;
+    addr = (pint_t) p;
+    break;
+  case DW_EH_PE_sleb128:
+    result = (pint_t)getSLEB128(addr, end);
+    break;
+  case DW_EH_PE_sdata2:
+    // Sign extend from signed 16-bit value.
+    result = (pint_t)(int16_t)get16(addr);
+    p += 2;
+    addr = (pint_t) p;
+    break;
+  case DW_EH_PE_sdata4:
+    // Sign extend from signed 32-bit value.
+    result = (pint_t)(int32_t)get32(addr);
+    p += 4;
+    addr = (pint_t) p;
+    break;
+  case DW_EH_PE_sdata8:
+    result = (pint_t)get64(addr);
+    p += 8;
+    addr = (pint_t) p;
+    break;
+  default:
+    _LIBUNWIND_ABORT("unknown pointer encoding");
+  }
+
+  // then add relative offset
+  switch (encoding & 0x70) {
+  case DW_EH_PE_absptr:
+    // do nothing
+    break;
+  case DW_EH_PE_pcrel:
+    result += startAddr;
+    break;
+  case DW_EH_PE_textrel:
+    _LIBUNWIND_ABORT("DW_EH_PE_textrel pointer encoding not supported");
+    break;
+  case DW_EH_PE_datarel:
+    // DW_EH_PE_datarel is only valid in a few places, so the parameter has a
+    // default value of 0, and we abort in the event that someone calls this
+    // function with a datarelBase of 0 and DW_EH_PE_datarel encoding.
+    if (datarelBase == 0)
+      _LIBUNWIND_ABORT("DW_EH_PE_datarel is invalid with a datarelBase of 0");
+    result += datarelBase;
+    break;
+  case DW_EH_PE_funcrel:
+    _LIBUNWIND_ABORT("DW_EH_PE_funcrel pointer encoding not supported");
+    break;
+  case DW_EH_PE_aligned:
+    _LIBUNWIND_ABORT("DW_EH_PE_aligned pointer encoding not supported");
+    break;
+  default:
+    _LIBUNWIND_ABORT("unknown pointer encoding");
+    break;
+  }
+
+  if (encoding & DW_EH_PE_indirect)
+    result = getP(result);
+
+  return result;
+}
+
+#if defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
+
+// The ElfW() macro for pointer-size independent ELF header traversal is not
+// provided by <link.h> on some systems (e.g., FreeBSD). On these systems the
+// data structures are just called Elf_XXX. Define ElfW() locally.
+#if !defined(ElfW)
+  #define ElfW(type) Elf_##type
+#endif
+#if !defined(Elf_Half)
+  typedef ElfW(Half) Elf_Half;
+#endif
+#if !defined(Elf_Phdr)
+  typedef ElfW(Phdr) Elf_Phdr;
+#endif
+#if !defined(Elf_Addr)
+  typedef ElfW(Addr) Elf_Addr;
+#endif
+
+struct _LIBUNWIND_HIDDEN dl_iterate_cb_data {
+  LocalAddressSpace *addressSpace;
+  UnwindInfoSections *sects;
+  uintptr_t targetAddr;
+};
+
+#if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
+#include "third_party/libunwind/FrameHeaderCache.hpp"
+
+// Typically there is one cache per process, but when libunwind is built as a
+// hermetic static library, then each shared object may have its own cache.
+static FrameHeaderCache TheFrameHeaderCache;
+#endif
+
+static bool checkAddrInSegment(const Elf_Phdr *phdr, size_t image_base,
+                               dl_iterate_cb_data *cbdata) {
+  if (phdr->p_type == PT_LOAD) {
+    uintptr_t begin = image_base + phdr->p_vaddr;
+    uintptr_t end = begin + phdr->p_memsz;
+    if (cbdata->targetAddr >= begin && cbdata->targetAddr < end) {
+      cbdata->sects->dso_base = begin;
+      cbdata->sects->text_segment_length = phdr->p_memsz;
+      return true;
+    }
+  }
+  return false;
+}
+
+static bool checkForUnwindInfoSegment(const Elf_Phdr *phdr, size_t image_base,
+                                      dl_iterate_cb_data *cbdata) {
+#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
+  if (phdr->p_type == PT_GNU_EH_FRAME) {
+    EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
+    uintptr_t eh_frame_hdr_start = image_base + phdr->p_vaddr;
+    cbdata->sects->dwarf_index_section = eh_frame_hdr_start;
+    cbdata->sects->dwarf_index_section_length = phdr->p_memsz;
+    if (EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
+            *cbdata->addressSpace, eh_frame_hdr_start, phdr->p_memsz,
+            hdrInfo)) {
+      // .eh_frame_hdr records the start of .eh_frame, but not its size.
+      // Rely on a zero terminator to find the end of the section.
+      cbdata->sects->dwarf_section = hdrInfo.eh_frame_ptr;
+      cbdata->sects->dwarf_section_length = SIZE_MAX;
+      return true;
+    }
+  }
+  return false;
+#elif defined(_LIBUNWIND_ARM_EHABI)
+  if (phdr->p_type == PT_ARM_EXIDX) {
+    uintptr_t exidx_start = image_base + phdr->p_vaddr;
+    cbdata->sects->arm_section = exidx_start;
+    cbdata->sects->arm_section_length = phdr->p_memsz;
+    return true;
+  }
+  return false;
+#else
+#error Need one of _LIBUNWIND_SUPPORT_DWARF_INDEX or _LIBUNWIND_ARM_EHABI
+#endif
+}
+
+static int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo,
+                                    size_t pinfo_size, void *data) {
+  auto cbdata = static_cast<dl_iterate_cb_data *>(data);
+  if (pinfo->dlpi_phnum == 0 || cbdata->targetAddr < pinfo->dlpi_addr)
+    return 0;
+#if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
+  if (TheFrameHeaderCache.find(pinfo, pinfo_size, data))
+    return 1;
+#else
+  // Avoid warning about unused variable.
+  (void)pinfo_size;
+#endif
+
+  Elf_Addr image_base = pinfo->dlpi_addr;
+
+  // Most shared objects seen in this callback function likely don't contain the
+  // target address, so optimize for that. Scan for a matching PT_LOAD segment
+  // first and bail when it isn't found.
+  bool found_text = false;
+  for (Elf_Half i = 0; i < pinfo->dlpi_phnum; ++i) {
+    if (checkAddrInSegment(&pinfo->dlpi_phdr[i], image_base, cbdata)) {
+      found_text = true;
+      break;
+    }
+  }
+  if (!found_text)
+    return 0;
+
+  // PT_GNU_EH_FRAME and PT_ARM_EXIDX are usually near the end. Iterate
+  // backward.
+  bool found_unwind = false;
+  for (Elf_Half i = pinfo->dlpi_phnum; i > 0; i--) {
+    const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i - 1];
+    if (checkForUnwindInfoSegment(phdr, image_base, cbdata)) {
+      found_unwind = true;
+      break;
+    }
+  }
+  if (!found_unwind)
+    return 0;
+
+#if defined(_LIBUNWIND_USE_FRAME_HEADER_CACHE)
+  TheFrameHeaderCache.add(cbdata->sects);
+#endif
+  return 1;
+}
+
+#endif  // defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
+
+
+inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
+                                                  UnwindInfoSections &info) {
+#ifdef __APPLE__
+  dyld_unwind_sections dyldInfo;
+  if (_dyld_find_unwind_sections((void *)targetAddr, &dyldInfo)) {
+    info.dso_base                      = (uintptr_t)dyldInfo.mh;
+ #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+    info.dwarf_section                 = (uintptr_t)dyldInfo.dwarf_section;
+    info.dwarf_section_length          = (size_t)dyldInfo.dwarf_section_length;
+ #endif
+    info.compact_unwind_section        = (uintptr_t)dyldInfo.compact_unwind_section;
+    info.compact_unwind_section_length = (size_t)dyldInfo.compact_unwind_section_length;
+    return true;
+  }
+
+  unw_dynamic_unwind_sections dynamicUnwindSectionInfo;
+  if (findDynamicUnwindSections((void *)targetAddr,
+                                &dynamicUnwindSectionInfo)) {
+    info.dso_base = dynamicUnwindSectionInfo.dso_base;
+#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+    info.dwarf_section = (uintptr_t)dynamicUnwindSectionInfo.dwarf_section;
+    info.dwarf_section_length = dynamicUnwindSectionInfo.dwarf_section_length;
+#endif
+    info.compact_unwind_section =
+        (uintptr_t)dynamicUnwindSectionInfo.compact_unwind_section;
+    info.compact_unwind_section_length =
+        dynamicUnwindSectionInfo.compact_unwind_section_length;
+    return true;
+  }
+
+#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
+  info.dso_base = 0;
+  // Bare metal is statically linked, so no need to ask the dynamic loader
+  info.dwarf_section_length = (size_t)(&__eh_frame_end - &__eh_frame_start);
+  info.dwarf_section =        (uintptr_t)(&__eh_frame_start);
+  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
+                             (void *)info.dwarf_section, (void *)info.dwarf_section_length);
+#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
+  info.dwarf_index_section =        (uintptr_t)(&__eh_frame_hdr_start);
+  info.dwarf_index_section_length = (size_t)(&__eh_frame_hdr_end - &__eh_frame_hdr_start);
+  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: index section %p length %p",
+                             (void *)info.dwarf_index_section, (void *)info.dwarf_index_section_length);
+#endif
+  if (info.dwarf_section_length)
+    return true;
+#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
+  // Bare metal is statically linked, so no need to ask the dynamic loader
+  info.arm_section =        (uintptr_t)(&__exidx_start);
+  info.arm_section_length = (size_t)(&__exidx_end - &__exidx_start);
+  _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
+                             (void *)info.arm_section, (void *)info.arm_section_length);
+  if (info.arm_section && info.arm_section_length)
+    return true;
+#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_WIN32)
+  HMODULE mods[1024];
+  HANDLE process = GetCurrentProcess();
+  DWORD needed;
+
+  if (!EnumProcessModules(process, mods, sizeof(mods), &needed)) {
+    DWORD err = GetLastError();
+    _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: EnumProcessModules failed, "
+                               "returned error %d", (int)err);
+    (void)err;
+    return false;
+  }
+
+  for (unsigned i = 0; i < (needed / sizeof(HMODULE)); i++) {
+    PIMAGE_DOS_HEADER pidh = (PIMAGE_DOS_HEADER)mods[i];
+    PIMAGE_NT_HEADERS pinh = (PIMAGE_NT_HEADERS)((BYTE *)pidh + pidh->e_lfanew);
+    PIMAGE_FILE_HEADER pifh = (PIMAGE_FILE_HEADER)&pinh->FileHeader;
+    PIMAGE_SECTION_HEADER pish = IMAGE_FIRST_SECTION(pinh);
+    bool found_obj = false;
+    bool found_hdr = false;
+
+    info.dso_base = (uintptr_t)mods[i];
+    for (unsigned j = 0; j < pifh->NumberOfSections; j++, pish++) {
+      uintptr_t begin = pish->VirtualAddress + (uintptr_t)mods[i];
+      uintptr_t end = begin + pish->Misc.VirtualSize;
+      if (!strncmp((const char *)pish->Name, ".text",
+                   IMAGE_SIZEOF_SHORT_NAME)) {
+        if (targetAddr >= begin && targetAddr < end)
+          found_obj = true;
+      } else if (!strncmp((const char *)pish->Name, ".eh_frame",
+                          IMAGE_SIZEOF_SHORT_NAME)) {
+        info.dwarf_section = begin;
+        info.dwarf_section_length = pish->Misc.VirtualSize;
+        found_hdr = true;
+      }
+      if (found_obj && found_hdr)
+        return true;
+    }
+  }
+  return false;
+#elif defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) && defined(_WIN32)
+  // Don't even bother, since Windows has functions that do all this stuff
+  // for us.
+  (void)targetAddr;
+  (void)info;
+  return true;
+#elif defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
+  // The traceback table is used for unwinding.
+  (void)targetAddr;
+  (void)info;
+  return true;
+#elif defined(_LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX)
+  int length = 0;
+  info.arm_section =
+      (uintptr_t)dl_unwind_find_exidx((_Unwind_Ptr)targetAddr, &length);
+  info.arm_section_length = (size_t)length * sizeof(EHABIIndexEntry);
+  if (info.arm_section && info.arm_section_length)
+    return true;
+#elif defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)
+  // Use DLFO_STRUCT_HAS_EH_DBASE to determine the existence of
+  // `_dl_find_object`. Use _LIBUNWIND_SUPPORT_DWARF_INDEX, because libunwind
+  // support for _dl_find_object on other unwind formats is not implemented,
+  // yet.
+#if defined(DLFO_STRUCT_HAS_EH_DBASE) & defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
+  // We expect `_dl_find_object` to return PT_GNU_EH_FRAME.
+#if DLFO_EH_SEGMENT_TYPE != PT_GNU_EH_FRAME
+#error _dl_find_object retrieves an unexpected section type
+#endif
+  // We look-up `dl_find_object` dynamically at runtime to ensure backwards
+  // compatibility with earlier version of glibc not yet providing it. On older
+  // systems, we gracefully fallback to `dl_iterate_phdr`. Cache the pointer
+  // so we only look it up once. Do manual lock to avoid _cxa_guard_acquire.
+  static decltype(_dl_find_object) *dlFindObject;
+  static bool dlFindObjectChecked = false;
+  if (!dlFindObjectChecked) {
+    dlFindObject = reinterpret_cast<decltype(_dl_find_object) *>(
+        dlsym(RTLD_DEFAULT, "_dl_find_object"));
+    dlFindObjectChecked = true;
+  }
+  // Try to find the unwind info using `dl_find_object`
+  dl_find_object findResult;
+  if (dlFindObject && dlFindObject((void *)targetAddr, &findResult) == 0) {
+    if (findResult.dlfo_eh_frame == nullptr) {
+      // Found an entry for `targetAddr`, but there is no unwind info.
+      return false;
+    }
+    info.dso_base = reinterpret_cast<uintptr_t>(findResult.dlfo_map_start);
+    info.text_segment_length = static_cast<size_t>(
+        (char *)findResult.dlfo_map_end - (char *)findResult.dlfo_map_start);
+
+    // Record the start of PT_GNU_EH_FRAME.
+    info.dwarf_index_section =
+        reinterpret_cast<uintptr_t>(findResult.dlfo_eh_frame);
+    // `_dl_find_object` does not give us the size of PT_GNU_EH_FRAME.
+    // Setting length to `SIZE_MAX` effectively disables all range checks.
+    info.dwarf_index_section_length = SIZE_MAX;
+    EHHeaderParser<LocalAddressSpace>::EHHeaderInfo hdrInfo;
+    if (!EHHeaderParser<LocalAddressSpace>::decodeEHHdr(
+            *this, info.dwarf_index_section, info.dwarf_index_section_length,
+            hdrInfo)) {
+      return false;
+    }
+    // Record the start of the FDE and use SIZE_MAX to indicate that we do
+    // not know the end address.
+    info.dwarf_section = hdrInfo.eh_frame_ptr;
+    info.dwarf_section_length = SIZE_MAX;
+    return true;
+  }
+#endif
+  dl_iterate_cb_data cb_data = {this, &info, targetAddr};
+  int found = dl_iterate_phdr(findUnwindSectionsByPhdr, &cb_data);
+  return static_cast<bool>(found);
+#endif
+
+  return false;
+}
+
+inline bool LocalAddressSpace::findOtherFDE(pint_t targetAddr, pint_t &fde) {
+  // TO DO: if OS has way to dynamically register FDEs, check that.
+  (void)targetAddr;
+  (void)fde;
+  return false;
+}
+
+inline bool LocalAddressSpace::findFunctionName(pint_t addr, char *buf,
+                                                size_t bufLen,
+                                                unw_word_t *offset) {
+#if _LIBUNWIND_USE_DLADDR
+  Dl_info dyldInfo;
+  if (dladdr((void *)addr, &dyldInfo)) {
+    if (dyldInfo.dli_sname != NULL) {
+      snprintf(buf, bufLen, "%s", dyldInfo.dli_sname);
+      *offset = (addr - (pint_t) dyldInfo.dli_saddr);
+      return true;
+    }
+  }
+#elif defined(_AIX)
+  uint16_t nameLen;
+  char *funcName = getFuncNameFromTBTable(addr, nameLen, offset);
+  if (funcName != NULL) {
+    snprintf(buf, bufLen, "%.*s", nameLen, funcName);
+    return true;
+  }
+#else
+  (void)addr;
+  (void)buf;
+  (void)bufLen;
+  (void)offset;
+#endif
+  return false;
+}
+
+} // namespace libunwind
+
+#endif // __ADDRESSSPACE_HPP__

third_party/libunwind/BUILD.mk

@@ -0,0 +1,88 @@
+#-*-mode:makefile-gmake;indent-tabs-mode:t;tab-width:8;coding:utf-8-*-┐
+#── vi: set noet ft=make ts=8 sw=8 fenc=utf-8 :vi ────────────────────┘
+
+PKGS += THIRD_PARTY_LIBUNWIND
+
+THIRD_PARTY_LIBUNWIND_ARTIFACTS += THIRD_PARTY_LIBUNWIND_A
+THIRD_PARTY_LIBUNWIND = $(THIRD_PARTY_LIBUNWIND_A_DEPS) $(THIRD_PARTY_LIBUNWIND_A)
+THIRD_PARTY_LIBUNWIND_A = o/$(MODE)/third_party/libunwind/libunwind.a
+
+THIRD_PARTY_LIBUNWIND_A_INCS =						\
+	third_party/libunwind/include/unwind_arm_ehabi.h		\
+	third_party/libunwind/include/unwind_itanium.h			\
+	third_party/libunwind/AddressSpace.hpp				\
+	third_party/libunwind/FrameHeaderCache.hpp			\
+	third_party/libunwind/RWMutex.hpp				\
+	third_party/libunwind/UnwindCursor.hpp
+
+THIRD_PARTY_LIBUNWIND_A_HDRS =						\
+	third_party/libunwind/include/mach-o/compact_unwind_encoding.h	\
+	third_party/libunwind/include/__libunwind_config.h		\
+	third_party/libunwind/include/libunwind.h			\
+	third_party/libunwind/include/unwind.h				\
+	third_party/libunwind/config.h					\
+	third_party/libunwind/cet_unwind.h				\
+	third_party/libunwind/dwarf2.h					\
+	third_party/libunwind/libunwind_ext.h				\
+	third_party/libunwind/CompactUnwinder.hpp			\
+	third_party/libunwind/DwarfInstructions.hpp			\
+	third_party/libunwind/DwarfParser.hpp				\
+	third_party/libunwind/EHHeaderParser.hpp			\
+	third_party/libunwind/Registers.hpp				\
+	third_party/libunwind/Unwind-EHABI.h
+
+THIRD_PARTY_LIBUNWIND_A_SRCS_CC =					\
+	third_party/libunwind/libunwind.cc
+
+THIRD_PARTY_LIBUNWIND_A_SRCS_C =					\
+	third_party/libunwind/Unwind-sjlj.c				\
+	third_party/libunwind/UnwindLevel1-gcc-ext.c			\
+	third_party/libunwind/UnwindLevel1.c
+
+THIRD_PARTY_LIBUNWIND_A_SRCS =						\
+	$(THIRD_PARTY_LIBUNWIND_A_SRCS_C)				\
+	$(THIRD_PARTY_LIBUNWIND_A_SRCS_CC)
+
+THIRD_PARTY_LIBUNWIND_A_OBJS =						\
+	$(THIRD_PARTY_LIBUNWIND_A_SRCS_C:%.c=o/$(MODE)/%.o)		\
+	$(THIRD_PARTY_LIBUNWIND_A_SRCS_CC:%.cc=o/$(MODE)/%.o)
+
+THIRD_PARTY_LIBUNWIND_A_CHECKS =					\
+	$(THIRD_PARTY_LIBUNWIND_A).pkg					\
+	$(THIRD_PARTY_LIBUNWIND_A_HDRS:%=o/$(MODE)/%.okk)
+
+THIRD_PARTY_LIBUNWIND_A_DIRECTDEPS =					\
+	LIBC_CALLS							\
+	LIBC_INTRIN							\
+	LIBC_STDIO							\
+	THIRD_PARTY_LIBCXX
+
+THIRD_PARTY_LIBUNWIND_A_DEPS :=						\
+	$(call uniq,$(foreach x,$(THIRD_PARTY_LIBUNWIND_A_DIRECTDEPS),$($(x))))
+
+$(THIRD_PARTY_LIBUNWIND_A):						\
+		third_party/libunwind/					\
+		$(THIRD_PARTY_LIBUNWIND_A).pkg				\
+		$(THIRD_PARTY_LIBUNWIND_A_OBJS)
+
+$(THIRD_PARTY_LIBUNWIND_A).pkg:						\
+		$(THIRD_PARTY_LIBUNWIND_A_OBJS)				\
+		$(foreach x,$(THIRD_PARTY_LIBUNWIND_A_DIRECTDEPS),$($(x)_A).pkg)
+
+$(THIRD_PARTY_LIBUNWIND_A_OBJS): private				\
+		CXXFLAGS +=						\
+			-ffunction-sections				\
+			-fdata-sections					\
+			-D_LIBUNWIND_USE_DLADDR=0
+
+THIRD_PARTY_LIBUNWIND_LIBS = $(foreach x,$(THIRD_PARTY_LIBUNWIND_ARTIFACTS),$($(x)))
+THIRD_PARTY_LIBUNWIND_SRCS = $(foreach x,$(THIRD_PARTY_LIBUNWIND_ARTIFACTS),$($(x)_SRCS))
+THIRD_PARTY_LIBUNWIND_HDRS = $(foreach x,$(THIRD_PARTY_LIBUNWIND_ARTIFACTS),$($(x)_HDRS))
+THIRD_PARTY_LIBUNWIND_INCS = $(foreach x,$(THIRD_PARTY_LIBUNWIND_ARTIFACTS),$($(x)_INCS))
+THIRD_PARTY_LIBUNWIND_CHECKS = $(foreach x,$(THIRD_PARTY_LIBUNWIND_ARTIFACTS),$($(x)_CHECKS))
+THIRD_PARTY_LIBUNWIND_OBJS = $(foreach x,$(THIRD_PARTY_LIBUNWIND_ARTIFACTS),$($(x)_OBJS))
+
+.PHONY: o/$(MODE)/third_party/libunwind
+o/$(MODE)/third_party/libunwind: \
+	$(THIRD_PARTY_LIBUNWIND_CHECKS)	\
+	$(THIRD_PARTY_LIBUNWIND_A)

third_party/libunwind/CompactUnwinder.hpp

@@ -0,0 +1,698 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Does runtime stack unwinding using compact unwind encodings.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __COMPACT_UNWINDER_HPP__
+#define __COMPACT_UNWINDER_HPP__
+
+#include "libc/isystem/stdint.h"
+#include "libc/isystem/stdlib.h"
+
+#include "third_party/libunwind/include/libunwind.h"
+#include "third_party/libunwind/include/mach-o/compact_unwind_encoding.h"
+
+#include "third_party/libunwind/Registers.hpp"
+#include "third_party/libunwind/libunwind_ext.h"
+
+#define EXTRACT_BITS(value, mask)                                              \
+  ((value >> __builtin_ctz(mask)) & (((1 << __builtin_popcount(mask))) - 1))
+
+namespace libunwind {
+
+#if defined(_LIBUNWIND_TARGET_I386)
+/// CompactUnwinder_x86 uses a compact unwind info to virtually "step" (aka
+/// unwind) by modifying a Registers_x86 register set
+template <typename A>
+class CompactUnwinder_x86 {
+public:
+
+  static int stepWithCompactEncoding(compact_unwind_encoding_t info,
+                                     uint32_t functionStart, A &addressSpace,
+                                     Registers_x86 &registers);
+
+private:
+  typename A::pint_t pint_t;
+
+  static void frameUnwind(A &addressSpace, Registers_x86 &registers);
+  static void framelessUnwind(A &addressSpace,
+                              typename A::pint_t returnAddressLocation,
+                              Registers_x86 &registers);
+  static int
+      stepWithCompactEncodingEBPFrame(compact_unwind_encoding_t compactEncoding,
+                                      uint32_t functionStart, A &addressSpace,
+                                      Registers_x86 &registers);
+  static int stepWithCompactEncodingFrameless(
+      compact_unwind_encoding_t compactEncoding, uint32_t functionStart,
+      A &addressSpace, Registers_x86 &registers, bool indirectStackSize);
+};
+
+template <typename A>
+int CompactUnwinder_x86<A>::stepWithCompactEncoding(
+    compact_unwind_encoding_t compactEncoding, uint32_t functionStart,
+    A &addressSpace, Registers_x86 &registers) {
+  switch (compactEncoding & UNWIND_X86_MODE_MASK) {
+  case UNWIND_X86_MODE_EBP_FRAME:
+    return stepWithCompactEncodingEBPFrame(compactEncoding, functionStart,
+                                           addressSpace, registers);
+  case UNWIND_X86_MODE_STACK_IMMD:
+    return stepWithCompactEncodingFrameless(compactEncoding, functionStart,
+                                            addressSpace, registers, false);
+  case UNWIND_X86_MODE_STACK_IND:
+    return stepWithCompactEncodingFrameless(compactEncoding, functionStart,
+                                            addressSpace, registers, true);
+  }
+  _LIBUNWIND_ABORT("invalid compact unwind encoding");
+}
+
+template <typename A>
+int CompactUnwinder_x86<A>::stepWithCompactEncodingEBPFrame(
+    compact_unwind_encoding_t compactEncoding, uint32_t functionStart,
+    A &addressSpace, Registers_x86 &registers) {
+  uint32_t savedRegistersOffset =
+      EXTRACT_BITS(compactEncoding, UNWIND_X86_EBP_FRAME_OFFSET);
+  uint32_t savedRegistersLocations =
+      EXTRACT_BITS(compactEncoding, UNWIND_X86_EBP_FRAME_REGISTERS);
+
+  uint32_t savedRegisters = registers.getEBP() - 4 * savedRegistersOffset;
+  for (int i = 0; i < 5; ++i) {
+    switch (savedRegistersLocations & 0x7) {
+    case UNWIND_X86_REG_NONE:
+      // no register saved in this slot
+      break;
+    case UNWIND_X86_REG_EBX:
+      registers.setEBX(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_ECX:
+      registers.setECX(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_EDX:
+      registers.setEDX(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_EDI:
+      registers.setEDI(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_ESI:
+      registers.setESI(addressSpace.get32(savedRegisters));
+      break;
+    default:
+      (void)functionStart;
+      _LIBUNWIND_DEBUG_LOG("bad register for EBP frame, encoding=%08X for  "
+                           "function starting at 0x%X",
+                            compactEncoding, functionStart);
+      _LIBUNWIND_ABORT("invalid compact unwind encoding");
+    }
+    savedRegisters += 4;
+    savedRegistersLocations = (savedRegistersLocations >> 3);
+  }
+  frameUnwind(addressSpace, registers);
+  return UNW_STEP_SUCCESS;
+}
+
+template <typename A>
+int CompactUnwinder_x86<A>::stepWithCompactEncodingFrameless(
+    compact_unwind_encoding_t encoding, uint32_t functionStart,
+    A &addressSpace, Registers_x86 &registers, bool indirectStackSize) {
+  uint32_t stackSizeEncoded =
+      EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_SIZE);
+  uint32_t stackAdjust =
+      EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_ADJUST);
+  uint32_t regCount =
+      EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_REG_COUNT);
+  uint32_t permutation =
+      EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION);
+  uint32_t stackSize = stackSizeEncoded * 4;
+  if (indirectStackSize) {
+    // stack size is encoded in subl $xxx,%esp instruction
+    uint32_t subl = addressSpace.get32(functionStart + stackSizeEncoded);
+    stackSize = subl + 4 * stackAdjust;
+  }
+  // decompress permutation
+  uint32_t permunreg[6];
+  switch (regCount) {
+  case 6:
+    permunreg[0] = permutation / 120;
+    permutation -= (permunreg[0] * 120);
+    permunreg[1] = permutation / 24;
+    permutation -= (permunreg[1] * 24);
+    permunreg[2] = permutation / 6;
+    permutation -= (permunreg[2] * 6);
+    permunreg[3] = permutation / 2;
+    permutation -= (permunreg[3] * 2);
+    permunreg[4] = permutation;
+    permunreg[5] = 0;
+    break;
+  case 5:
+    permunreg[0] = permutation / 120;
+    permutation -= (permunreg[0] * 120);
+    permunreg[1] = permutation / 24;
+    permutation -= (permunreg[1] * 24);
+    permunreg[2] = permutation / 6;
+    permutation -= (permunreg[2] * 6);
+    permunreg[3] = permutation / 2;
+    permutation -= (permunreg[3] * 2);
+    permunreg[4] = permutation;
+    break;
+  case 4:
+    permunreg[0] = permutation / 60;
+    permutation -= (permunreg[0] * 60);
+    permunreg[1] = permutation / 12;
+    permutation -= (permunreg[1] * 12);
+    permunreg[2] = permutation / 3;
+    permutation -= (permunreg[2] * 3);
+    permunreg[3] = permutation;
+    break;
+  case 3:
+    permunreg[0] = permutation / 20;
+    permutation -= (permunreg[0] * 20);
+    permunreg[1] = permutation / 4;
+    permutation -= (permunreg[1] * 4);
+    permunreg[2] = permutation;
+    break;
+  case 2:
+    permunreg[0] = permutation / 5;
+    permutation -= (permunreg[0] * 5);
+    permunreg[1] = permutation;
+    break;
+  case 1:
+    permunreg[0] = permutation;
+    break;
+  }
+  // re-number registers back to standard numbers
+  int registersSaved[6];
+  bool used[7] = { false, false, false, false, false, false, false };
+  for (uint32_t i = 0; i < regCount; ++i) {
+    uint32_t renum = 0;
+    for (int u = 1; u < 7; ++u) {
+      if (!used[u]) {
+        if (renum == permunreg[i]) {
+          registersSaved[i] = u;
+          used[u] = true;
+          break;
+        }
+        ++renum;
+      }
+    }
+  }
+  uint32_t savedRegisters = registers.getSP() + stackSize - 4 - 4 * regCount;
+  for (uint32_t i = 0; i < regCount; ++i) {
+    switch (registersSaved[i]) {
+    case UNWIND_X86_REG_EBX:
+      registers.setEBX(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_ECX:
+      registers.setECX(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_EDX:
+      registers.setEDX(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_EDI:
+      registers.setEDI(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_ESI:
+      registers.setESI(addressSpace.get32(savedRegisters));
+      break;
+    case UNWIND_X86_REG_EBP:
+      registers.setEBP(addressSpace.get32(savedRegisters));
+      break;
+    default:
+      _LIBUNWIND_DEBUG_LOG("bad register for frameless, encoding=%08X for "
+                           "function starting at 0x%X",
+                           encoding, functionStart);
+      _LIBUNWIND_ABORT("invalid compact unwind encoding");
+    }
+    savedRegisters += 4;
+  }
+  framelessUnwind(addressSpace, savedRegisters, registers);
+  return UNW_STEP_SUCCESS;
+}
+
+
+template <typename A>
+void CompactUnwinder_x86<A>::frameUnwind(A &addressSpace,
+                                         Registers_x86 &registers) {
+  typename A::pint_t bp = registers.getEBP();
+  // ebp points to old ebp
+  registers.setEBP(addressSpace.get32(bp));
+  // old esp is ebp less saved ebp and return address
+  registers.setSP((uint32_t)bp + 8);
+  // pop return address into eip
+  registers.setIP(addressSpace.get32(bp + 4));
+}
+
+template <typename A>
+void CompactUnwinder_x86<A>::framelessUnwind(
+    A &addressSpace, typename A::pint_t returnAddressLocation,
+    Registers_x86 &registers) {
+  // return address is on stack after last saved register
+  registers.setIP(addressSpace.get32(returnAddressLocation));
+  // old esp is before return address
+  registers.setSP((uint32_t)returnAddressLocation + 4);
+}
+#endif // _LIBUNWIND_TARGET_I386
+
+
+#if defined(_LIBUNWIND_TARGET_X86_64)
+/// CompactUnwinder_x86_64 uses a compact unwind info to virtually "step" (aka
+/// unwind) by modifying a Registers_x86_64 register set
+template <typename A>
+class CompactUnwinder_x86_64 {
+public:
+
+  static int stepWithCompactEncoding(compact_unwind_encoding_t compactEncoding,
+                                     uint64_t functionStart, A &addressSpace,
+                                     Registers_x86_64 &registers);
+
+private:
+  typename A::pint_t pint_t;
+
+  static void frameUnwind(A &addressSpace, Registers_x86_64 &registers);
+  static void framelessUnwind(A &addressSpace, uint64_t returnAddressLocation,
+                              Registers_x86_64 &registers);
+  static int
+      stepWithCompactEncodingRBPFrame(compact_unwind_encoding_t compactEncoding,
+                                      uint64_t functionStart, A &addressSpace,
+                                      Registers_x86_64 &registers);
+  static int stepWithCompactEncodingFrameless(
+      compact_unwind_encoding_t compactEncoding, uint64_t functionStart,
+      A &addressSpace, Registers_x86_64 &registers, bool indirectStackSize);
+};
+
+template <typename A>
+int CompactUnwinder_x86_64<A>::stepWithCompactEncoding(
+    compact_unwind_encoding_t compactEncoding, uint64_t functionStart,
+    A &addressSpace, Registers_x86_64 &registers) {
+  switch (compactEncoding & UNWIND_X86_64_MODE_MASK) {
+  case UNWIND_X86_64_MODE_RBP_FRAME:
+    return stepWithCompactEncodingRBPFrame(compactEncoding, functionStart,
+                                           addressSpace, registers);
+  case UNWIND_X86_64_MODE_STACK_IMMD:
+    return stepWithCompactEncodingFrameless(compactEncoding, functionStart,
+                                            addressSpace, registers, false);
+  case UNWIND_X86_64_MODE_STACK_IND:
+    return stepWithCompactEncodingFrameless(compactEncoding, functionStart,
+                                            addressSpace, registers, true);
+  }
+  _LIBUNWIND_ABORT("invalid compact unwind encoding");
+}
+
+template <typename A>
+int CompactUnwinder_x86_64<A>::stepWithCompactEncodingRBPFrame(
+    compact_unwind_encoding_t compactEncoding, uint64_t functionStart,
+    A &addressSpace, Registers_x86_64 &registers) {
+  uint32_t savedRegistersOffset =
+      EXTRACT_BITS(compactEncoding, UNWIND_X86_64_RBP_FRAME_OFFSET);
+  uint32_t savedRegistersLocations =
+      EXTRACT_BITS(compactEncoding, UNWIND_X86_64_RBP_FRAME_REGISTERS);
+
+  uint64_t savedRegisters = registers.getRBP() - 8 * savedRegistersOffset;
+  for (int i = 0; i < 5; ++i) {
+    switch (savedRegistersLocations & 0x7) {
+    case UNWIND_X86_64_REG_NONE:
+      // no register saved in this slot
+      break;
+    case UNWIND_X86_64_REG_RBX:
+      registers.setRBX(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R12:
+      registers.setR12(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R13:
+      registers.setR13(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R14:
+      registers.setR14(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R15:
+      registers.setR15(addressSpace.get64(savedRegisters));
+      break;
+    default:
+      (void)functionStart;
+      _LIBUNWIND_DEBUG_LOG("bad register for RBP frame, encoding=%08X for "
+                           "function starting at 0x%llX",
+                            compactEncoding, functionStart);
+      _LIBUNWIND_ABORT("invalid compact unwind encoding");
+    }
+    savedRegisters += 8;
+    savedRegistersLocations = (savedRegistersLocations >> 3);
+  }
+  frameUnwind(addressSpace, registers);
+  return UNW_STEP_SUCCESS;
+}
+
+template <typename A>
+int CompactUnwinder_x86_64<A>::stepWithCompactEncodingFrameless(
+    compact_unwind_encoding_t encoding, uint64_t functionStart, A &addressSpace,
+    Registers_x86_64 &registers, bool indirectStackSize) {
+  uint32_t stackSizeEncoded =
+      EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_SIZE);
+  uint32_t stackAdjust =
+      EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_ADJUST);
+  uint32_t regCount =
+      EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT);
+  uint32_t permutation =
+      EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_REG_PERMUTATION);
+  uint32_t stackSize = stackSizeEncoded * 8;
+  if (indirectStackSize) {
+    // stack size is encoded in subl $xxx,%esp instruction
+    uint32_t subl = addressSpace.get32(functionStart + stackSizeEncoded);
+    stackSize = subl + 8 * stackAdjust;
+  }
+  // decompress permutation
+  uint32_t permunreg[6];
+  switch (regCount) {
+  case 6:
+    permunreg[0] = permutation / 120;
+    permutation -= (permunreg[0] * 120);
+    permunreg[1] = permutation / 24;
+    permutation -= (permunreg[1] * 24);
+    permunreg[2] = permutation / 6;
+    permutation -= (permunreg[2] * 6);
+    permunreg[3] = permutation / 2;
+    permutation -= (permunreg[3] * 2);
+    permunreg[4] = permutation;
+    permunreg[5] = 0;
+    break;
+  case 5:
+    permunreg[0] = permutation / 120;
+    permutation -= (permunreg[0] * 120);
+    permunreg[1] = permutation / 24;
+    permutation -= (permunreg[1] * 24);
+    permunreg[2] = permutation / 6;
+    permutation -= (permunreg[2] * 6);
+    permunreg[3] = permutation / 2;
+    permutation -= (permunreg[3] * 2);
+    permunreg[4] = permutation;
+    break;
+  case 4:
+    permunreg[0] = permutation / 60;
+    permutation -= (permunreg[0] * 60);
+    permunreg[1] = permutation / 12;
+    permutation -= (permunreg[1] * 12);
+    permunreg[2] = permutation / 3;
+    permutation -= (permunreg[2] * 3);
+    permunreg[3] = permutation;
+    break;
+  case 3:
+    permunreg[0] = permutation / 20;
+    permutation -= (permunreg[0] * 20);
+    permunreg[1] = permutation / 4;
+    permutation -= (permunreg[1] * 4);
+    permunreg[2] = permutation;
+    break;
+  case 2:
+    permunreg[0] = permutation / 5;
+    permutation -= (permunreg[0] * 5);
+    permunreg[1] = permutation;
+    break;
+  case 1:
+    permunreg[0] = permutation;
+    break;
+  }
+  // re-number registers back to standard numbers
+  int registersSaved[6];
+  bool used[7] = { false, false, false, false, false, false, false };
+  for (uint32_t i = 0; i < regCount; ++i) {
+    uint32_t renum = 0;
+    for (int u = 1; u < 7; ++u) {
+      if (!used[u]) {
+        if (renum == permunreg[i]) {
+          registersSaved[i] = u;
+          used[u] = true;
+          break;
+        }
+        ++renum;
+      }
+    }
+  }
+  uint64_t savedRegisters = registers.getSP() + stackSize - 8 - 8 * regCount;
+  for (uint32_t i = 0; i < regCount; ++i) {
+    switch (registersSaved[i]) {
+    case UNWIND_X86_64_REG_RBX:
+      registers.setRBX(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R12:
+      registers.setR12(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R13:
+      registers.setR13(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R14:
+      registers.setR14(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_R15:
+      registers.setR15(addressSpace.get64(savedRegisters));
+      break;
+    case UNWIND_X86_64_REG_RBP:
+      registers.setRBP(addressSpace.get64(savedRegisters));
+      break;
+    default:
+      _LIBUNWIND_DEBUG_LOG("bad register for frameless, encoding=%08X for "
+                           "function starting at 0x%llX",
+                            encoding, functionStart);
+      _LIBUNWIND_ABORT("invalid compact unwind encoding");
+    }
+    savedRegisters += 8;
+  }
+  framelessUnwind(addressSpace, savedRegisters, registers);
+  return UNW_STEP_SUCCESS;
+}
+
+
+template <typename A>
+void CompactUnwinder_x86_64<A>::frameUnwind(A &addressSpace,
+                                            Registers_x86_64 &registers) {
+  uint64_t rbp = registers.getRBP();
+  // ebp points to old ebp
+  registers.setRBP(addressSpace.get64(rbp));
+  // old esp is ebp less saved ebp and return address
+  registers.setSP(rbp + 16);
+  // pop return address into eip
+  registers.setIP(addressSpace.get64(rbp + 8));
+}
+
+template <typename A>
+void CompactUnwinder_x86_64<A>::framelessUnwind(A &addressSpace,
+                                                uint64_t returnAddressLocation,
+                                                Registers_x86_64 &registers) {
+  // return address is on stack after last saved register
+  registers.setIP(addressSpace.get64(returnAddressLocation));
+  // old esp is before return address
+  registers.setSP(returnAddressLocation + 8);
+}
+#endif // _LIBUNWIND_TARGET_X86_64
+
+
+
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+/// CompactUnwinder_arm64 uses a compact unwind info to virtually "step" (aka
+/// unwind) by modifying a Registers_arm64 register set
+template <typename A>
+class CompactUnwinder_arm64 {
+public:
+
+  static int stepWithCompactEncoding(compact_unwind_encoding_t compactEncoding,
+                                     uint64_t functionStart, A &addressSpace,
+                                     Registers_arm64 &registers);
+
+private:
+  typename A::pint_t pint_t;
+
+  static int
+      stepWithCompactEncodingFrame(compact_unwind_encoding_t compactEncoding,
+                                   uint64_t functionStart, A &addressSpace,
+                                   Registers_arm64 &registers);
+  static int stepWithCompactEncodingFrameless(
+      compact_unwind_encoding_t compactEncoding, uint64_t functionStart,
+      A &addressSpace, Registers_arm64 &registers);
+};
+
+template <typename A>
+int CompactUnwinder_arm64<A>::stepWithCompactEncoding(
+    compact_unwind_encoding_t compactEncoding, uint64_t functionStart,
+    A &addressSpace, Registers_arm64 &registers) {
+  switch (compactEncoding & UNWIND_ARM64_MODE_MASK) {
+  case UNWIND_ARM64_MODE_FRAME:
+    return stepWithCompactEncodingFrame(compactEncoding, functionStart,
+                                        addressSpace, registers);
+  case UNWIND_ARM64_MODE_FRAMELESS:
+    return stepWithCompactEncodingFrameless(compactEncoding, functionStart,
+                                            addressSpace, registers);
+  }
+  _LIBUNWIND_ABORT("invalid compact unwind encoding");
+}
+
+template <typename A>
+int CompactUnwinder_arm64<A>::stepWithCompactEncodingFrameless(
+    compact_unwind_encoding_t encoding, uint64_t, A &addressSpace,
+    Registers_arm64 &registers) {
+  uint32_t stackSize =
+      16 * EXTRACT_BITS(encoding, UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK);
+
+  uint64_t savedRegisterLoc = registers.getSP() + stackSize;
+
+  if (encoding & UNWIND_ARM64_FRAME_X19_X20_PAIR) {
+    registers.setRegister(UNW_AARCH64_X19, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X20, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X21_X22_PAIR) {
+    registers.setRegister(UNW_AARCH64_X21, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X22, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X23_X24_PAIR) {
+    registers.setRegister(UNW_AARCH64_X23, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X24, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X25_X26_PAIR) {
+    registers.setRegister(UNW_AARCH64_X25, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X26, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X27_X28_PAIR) {
+    registers.setRegister(UNW_AARCH64_X27, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X28, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+
+  if (encoding & UNWIND_ARM64_FRAME_D8_D9_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V8,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V9,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_D10_D11_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V10,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V11,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_D12_D13_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V12,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V13,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_D14_D15_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V14,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V15,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+
+  // subtract stack size off of sp
+  registers.setSP(savedRegisterLoc);
+
+  // set pc to be value in lr
+  registers.setIP(registers.getRegister(UNW_AARCH64_LR));
+
+  return UNW_STEP_SUCCESS;
+}
+
+template <typename A>
+int CompactUnwinder_arm64<A>::stepWithCompactEncodingFrame(
+    compact_unwind_encoding_t encoding, uint64_t, A &addressSpace,
+    Registers_arm64 &registers) {
+  uint64_t savedRegisterLoc = registers.getFP() - 8;
+
+  if (encoding & UNWIND_ARM64_FRAME_X19_X20_PAIR) {
+    registers.setRegister(UNW_AARCH64_X19, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X20, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X21_X22_PAIR) {
+    registers.setRegister(UNW_AARCH64_X21, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X22, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X23_X24_PAIR) {
+    registers.setRegister(UNW_AARCH64_X23, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X24, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X25_X26_PAIR) {
+    registers.setRegister(UNW_AARCH64_X25, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X26, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_X27_X28_PAIR) {
+    registers.setRegister(UNW_AARCH64_X27, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setRegister(UNW_AARCH64_X28, addressSpace.get64(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+
+  if (encoding & UNWIND_ARM64_FRAME_D8_D9_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V8,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V9,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_D10_D11_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V10,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V11,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_D12_D13_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V12,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V13,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+  if (encoding & UNWIND_ARM64_FRAME_D14_D15_PAIR) {
+    registers.setFloatRegister(UNW_AARCH64_V14,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+    registers.setFloatRegister(UNW_AARCH64_V15,
+                               addressSpace.getDouble(savedRegisterLoc));
+    savedRegisterLoc -= 8;
+  }
+
+  uint64_t fp = registers.getFP();
+  // fp points to old fp
+  registers.setFP(addressSpace.get64(fp));
+  // old sp is fp less saved fp and lr
+  registers.setSP(fp + 16);
+  // pop return address into pc
+  registers.setIP(addressSpace.get64(fp + 8));
+
+  return UNW_STEP_SUCCESS;
+}
+#endif // _LIBUNWIND_TARGET_AARCH64
+
+
+} // namespace libunwind
+
+#endif // __COMPACT_UNWINDER_HPP__

third_party/libunwind/DwarfInstructions.hpp

@@ -0,0 +1,924 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Processor specific interpretation of DWARF unwind info.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __DWARF_INSTRUCTIONS_HPP__
+#define __DWARF_INSTRUCTIONS_HPP__
+
+#include "libc/isystem/stdint.h"
+#include "libc/stdio/stdio.h"
+#include "libc/isystem/stdlib.h"
+
+#include "third_party/libunwind/DwarfParser.hpp"
+#include "third_party/libunwind/Registers.hpp"
+#include "third_party/libunwind/config.h"
+#include "third_party/libunwind/dwarf2.h"
+#include "third_party/libunwind/libunwind_ext.h"
+
+
+namespace libunwind {
+
+
+/// DwarfInstructions maps abstract DWARF unwind instructions to a particular
+/// architecture
+template <typename A, typename R>
+class DwarfInstructions {
+public:
+  typedef typename A::pint_t pint_t;
+  typedef typename A::sint_t sint_t;
+
+  static int stepWithDwarf(A &addressSpace, pint_t pc, pint_t fdeStart,
+                           R &registers, bool &isSignalFrame, bool stage2);
+
+private:
+
+  enum {
+    DW_X86_64_RET_ADDR = 16
+  };
+
+  enum {
+    DW_X86_RET_ADDR = 8
+  };
+
+  typedef typename CFI_Parser<A>::RegisterLocation  RegisterLocation;
+  typedef typename CFI_Parser<A>::PrologInfo        PrologInfo;
+  typedef typename CFI_Parser<A>::FDE_Info          FDE_Info;
+  typedef typename CFI_Parser<A>::CIE_Info          CIE_Info;
+
+  static pint_t evaluateExpression(pint_t expression, A &addressSpace,
+                                   const R &registers,
+                                   pint_t initialStackValue);
+  static pint_t getSavedRegister(A &addressSpace, const R &registers,
+                                 pint_t cfa, const RegisterLocation &savedReg);
+  static double getSavedFloatRegister(A &addressSpace, const R &registers,
+                                  pint_t cfa, const RegisterLocation &savedReg);
+  static v128 getSavedVectorRegister(A &addressSpace, const R &registers,
+                                  pint_t cfa, const RegisterLocation &savedReg);
+
+  static pint_t getCFA(A &addressSpace, const PrologInfo &prolog,
+                       const R &registers) {
+    if (prolog.cfaRegister != 0)
+      return (pint_t)((sint_t)registers.getRegister((int)prolog.cfaRegister) +
+             prolog.cfaRegisterOffset);
+    if (prolog.cfaExpression != 0)
+      return evaluateExpression((pint_t)prolog.cfaExpression, addressSpace,
+                                registers, 0);
+    assert(0 && "getCFA(): unknown location");
+    __builtin_unreachable();
+  }
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+  static bool getRA_SIGN_STATE(A &addressSpace, R registers, pint_t cfa,
+                               PrologInfo &prolog);
+#endif
+};
+
+template <typename R>
+auto getSparcWCookie(const R &r, int) -> decltype(r.getWCookie()) {
+  return r.getWCookie();
+}
+template <typename R> uint64_t getSparcWCookie(const R &, long) {
+  return 0;
+}
+
+template <typename A, typename R>
+typename A::pint_t DwarfInstructions<A, R>::getSavedRegister(
+    A &addressSpace, const R &registers, pint_t cfa,
+    const RegisterLocation &savedReg) {
+  switch (savedReg.location) {
+  case CFI_Parser<A>::kRegisterInCFA:
+    return (pint_t)addressSpace.getRegister(cfa + (pint_t)savedReg.value);
+
+  case CFI_Parser<A>::kRegisterInCFADecrypt: // sparc64 specific
+    return (pint_t)(addressSpace.getP(cfa + (pint_t)savedReg.value) ^
+           getSparcWCookie(registers, 0));
+
+  case CFI_Parser<A>::kRegisterAtExpression:
+    return (pint_t)addressSpace.getRegister(evaluateExpression(
+        (pint_t)savedReg.value, addressSpace, registers, cfa));
+
+  case CFI_Parser<A>::kRegisterIsExpression:
+    return evaluateExpression((pint_t)savedReg.value, addressSpace,
+                              registers, cfa);
+
+  case CFI_Parser<A>::kRegisterInRegister:
+    return registers.getRegister((int)savedReg.value);
+  case CFI_Parser<A>::kRegisterUndefined:
+    return 0;
+  case CFI_Parser<A>::kRegisterUnused:
+  case CFI_Parser<A>::kRegisterOffsetFromCFA:
+    // FIX ME
+    break;
+  }
+  _LIBUNWIND_ABORT("unsupported restore location for register");
+}
+
+template <typename A, typename R>
+double DwarfInstructions<A, R>::getSavedFloatRegister(
+    A &addressSpace, const R &registers, pint_t cfa,
+    const RegisterLocation &savedReg) {
+  switch (savedReg.location) {
+  case CFI_Parser<A>::kRegisterInCFA:
+    return addressSpace.getDouble(cfa + (pint_t)savedReg.value);
+
+  case CFI_Parser<A>::kRegisterAtExpression:
+    return addressSpace.getDouble(
+        evaluateExpression((pint_t)savedReg.value, addressSpace,
+                            registers, cfa));
+  case CFI_Parser<A>::kRegisterUndefined:
+    return 0.0;
+  case CFI_Parser<A>::kRegisterInRegister:
+#ifndef _LIBUNWIND_TARGET_ARM
+    return registers.getFloatRegister((int)savedReg.value);
+#endif
+  case CFI_Parser<A>::kRegisterIsExpression:
+  case CFI_Parser<A>::kRegisterUnused:
+  case CFI_Parser<A>::kRegisterOffsetFromCFA:
+  case CFI_Parser<A>::kRegisterInCFADecrypt:
+    // FIX ME
+    break;
+  }
+  _LIBUNWIND_ABORT("unsupported restore location for float register");
+}
+
+template <typename A, typename R>
+v128 DwarfInstructions<A, R>::getSavedVectorRegister(
+    A &addressSpace, const R &registers, pint_t cfa,
+    const RegisterLocation &savedReg) {
+  switch (savedReg.location) {
+  case CFI_Parser<A>::kRegisterInCFA:
+    return addressSpace.getVector(cfa + (pint_t)savedReg.value);
+
+  case CFI_Parser<A>::kRegisterAtExpression:
+    return addressSpace.getVector(
+        evaluateExpression((pint_t)savedReg.value, addressSpace,
+                            registers, cfa));
+
+  case CFI_Parser<A>::kRegisterIsExpression:
+  case CFI_Parser<A>::kRegisterUnused:
+  case CFI_Parser<A>::kRegisterUndefined:
+  case CFI_Parser<A>::kRegisterOffsetFromCFA:
+  case CFI_Parser<A>::kRegisterInRegister:
+  case CFI_Parser<A>::kRegisterInCFADecrypt:
+    // FIX ME
+    break;
+  }
+  _LIBUNWIND_ABORT("unsupported restore location for vector register");
+}
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+template <typename A, typename R>
+bool DwarfInstructions<A, R>::getRA_SIGN_STATE(A &addressSpace, R registers,
+                                               pint_t cfa, PrologInfo &prolog) {
+  pint_t raSignState;
+  auto regloc = prolog.savedRegisters[UNW_AARCH64_RA_SIGN_STATE];
+  if (regloc.location == CFI_Parser<A>::kRegisterUnused)
+    raSignState = static_cast<pint_t>(regloc.value);
+  else
+    raSignState = getSavedRegister(addressSpace, registers, cfa, regloc);
+
+  // Only bit[0] is meaningful.
+  return raSignState & 0x01;
+}
+#endif
+
+template <typename A, typename R>
+int DwarfInstructions<A, R>::stepWithDwarf(A &addressSpace, pint_t pc,
+                                           pint_t fdeStart, R &registers,
+                                           bool &isSignalFrame, bool stage2) {
+  FDE_Info fdeInfo;
+  CIE_Info cieInfo;
+  if (CFI_Parser<A>::decodeFDE(addressSpace, fdeStart, &fdeInfo,
+                               &cieInfo) == NULL) {
+    PrologInfo prolog;
+    if (CFI_Parser<A>::parseFDEInstructions(addressSpace, fdeInfo, cieInfo, pc,
+                                            R::getArch(), &prolog)) {
+      // get pointer to cfa (architecture specific)
+      pint_t cfa = getCFA(addressSpace, prolog, registers);
+
+      (void)stage2;
+      // __unw_step_stage2 is not used for cross unwinding, so we use
+      // __aarch64__ rather than LIBUNWIND_TARGET_AARCH64 to make sure we are
+      // building for AArch64 natively.
+#if defined(__aarch64__)
+      if (stage2 && cieInfo.mteTaggedFrame) {
+        pint_t sp = registers.getSP();
+        pint_t p = sp;
+        // AArch64 doesn't require the value of SP to be 16-byte aligned at
+        // all times, only at memory accesses and public interfaces [1]. Thus,
+        // a signal could arrive at a point where SP is not aligned properly.
+        // In that case, the kernel fixes up [2] the signal frame, but we
+        // still have a misaligned SP in the previous frame. If that signal
+        // handler caused stack unwinding, we would have an unaligned SP.
+        // We do not need to fix up the CFA, as that is the SP at a "public
+        // interface".
+        // [1]:
+        // https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#622the-stack
+        // [2]:
+        // https://github.com/torvalds/linux/blob/1930a6e739c4b4a654a69164dbe39e554d228915/arch/arm64/kernel/signal.c#L718
+        p &= ~0xfULL;
+        // CFA is the bottom of the current stack frame.
+        for (; p < cfa; p += 16) {
+          __asm__ __volatile__(".arch armv8.5-a\n"
+                               ".arch_extension memtag\n"
+                               "stg %[Ptr], [%[Ptr]]\n"
+                               :
+                               : [Ptr] "r"(p)
+                               : "memory");
+        }
+      }
+#endif
+      // restore registers that DWARF says were saved
+      R newRegisters = registers;
+
+      // Typically, the CFA is the stack pointer at the call site in
+      // the previous frame. However, there are scenarios in which this is not
+      // true. For example, if we switched to a new stack. In that case, the
+      // value of the previous SP might be indicated by a CFI directive.
+      //
+      // We set the SP here to the CFA, allowing for it to be overridden
+      // by a CFI directive later on.
+      newRegisters.setSP(cfa);
+
+      pint_t returnAddress = 0;
+      constexpr int lastReg = R::lastDwarfRegNum();
+      static_assert(static_cast<int>(CFI_Parser<A>::kMaxRegisterNumber) >=
+                        lastReg,
+                    "register range too large");
+      assert(lastReg >= (int)cieInfo.returnAddressRegister &&
+             "register range does not contain return address register");
+      for (int i = 0; i <= lastReg; ++i) {
+        if (prolog.savedRegisters[i].location !=
+            CFI_Parser<A>::kRegisterUnused) {
+          if (registers.validFloatRegister(i))
+            newRegisters.setFloatRegister(
+                i, getSavedFloatRegister(addressSpace, registers, cfa,
+                                         prolog.savedRegisters[i]));
+          else if (registers.validVectorRegister(i))
+            newRegisters.setVectorRegister(
+                i, getSavedVectorRegister(addressSpace, registers, cfa,
+                                          prolog.savedRegisters[i]));
+          else if (i == (int)cieInfo.returnAddressRegister)
+            returnAddress = getSavedRegister(addressSpace, registers, cfa,
+                                             prolog.savedRegisters[i]);
+          else if (registers.validRegister(i))
+            newRegisters.setRegister(
+                i, getSavedRegister(addressSpace, registers, cfa,
+                                    prolog.savedRegisters[i]));
+          else
+            return UNW_EBADREG;
+        } else if (i == (int)cieInfo.returnAddressRegister) {
+            // Leaf function keeps the return address in register and there is no
+            // explicit instructions how to restore it.
+            returnAddress = registers.getRegister(cieInfo.returnAddressRegister);
+        }
+      }
+
+      isSignalFrame = cieInfo.isSignalFrame;
+
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+      // If the target is aarch64 then the return address may have been signed
+      // using the v8.3 pointer authentication extensions. The original
+      // return address needs to be authenticated before the return address is
+      // restored. autia1716 is used instead of autia as autia1716 assembles
+      // to a NOP on pre-v8.3a architectures.
+      if ((R::getArch() == REGISTERS_ARM64) &&
+          getRA_SIGN_STATE(addressSpace, registers, cfa, prolog) &&
+          returnAddress != 0) {
+#if !defined(_LIBUNWIND_IS_NATIVE_ONLY)
+        return UNW_ECROSSRASIGNING;
+#else
+        register unsigned long long x17 __asm("x17") = returnAddress;
+        register unsigned long long x16 __asm("x16") = cfa;
+
+        // These are the autia1716/autib1716 instructions. The hint instructions
+        // are used here as gcc does not assemble autia1716/autib1716 for pre
+        // armv8.3a targets.
+        if (cieInfo.addressesSignedWithBKey)
+          asm("hint 0xe" : "+r"(x17) : "r"(x16)); // autib1716
+        else
+          asm("hint 0xc" : "+r"(x17) : "r"(x16)); // autia1716
+        returnAddress = x17;
+#endif
+      }
+#endif
+
+#if defined(_LIBUNWIND_IS_NATIVE_ONLY) && defined(_LIBUNWIND_TARGET_ARM) &&    \
+    defined(__ARM_FEATURE_PAUTH)
+      if ((R::getArch() == REGISTERS_ARM) &&
+          prolog.savedRegisters[UNW_ARM_RA_AUTH_CODE].value) {
+        pint_t pac =
+            getSavedRegister(addressSpace, registers, cfa,
+                             prolog.savedRegisters[UNW_ARM_RA_AUTH_CODE]);
+        __asm__ __volatile__("autg %0, %1, %2"
+                             :
+                             : "r"(pac), "r"(returnAddress), "r"(cfa)
+                             :);
+      }
+#endif
+
+#if defined(_LIBUNWIND_TARGET_SPARC)
+      if (R::getArch() == REGISTERS_SPARC) {
+        // Skip call site instruction and delay slot
+        returnAddress += 8;
+        // Skip unimp instruction if function returns a struct
+        if ((addressSpace.get32(returnAddress) & 0xC1C00000) == 0)
+          returnAddress += 4;
+      }
+#endif
+
+#if defined(_LIBUNWIND_TARGET_SPARC64)
+      // Skip call site instruction and delay slot.
+      if (R::getArch() == REGISTERS_SPARC64)
+        returnAddress += 8;
+#endif
+
+#if defined(_LIBUNWIND_TARGET_PPC64)
+#define PPC64_ELFV1_R2_LOAD_INST_ENCODING 0xe8410028u // ld r2,40(r1)
+#define PPC64_ELFV1_R2_OFFSET 40
+#define PPC64_ELFV2_R2_LOAD_INST_ENCODING 0xe8410018u // ld r2,24(r1)
+#define PPC64_ELFV2_R2_OFFSET 24
+      // If the instruction at return address is a TOC (r2) restore,
+      // then r2 was saved and needs to be restored.
+      // ELFv2 ABI specifies that the TOC Pointer must be saved at SP + 24,
+      // while in ELFv1 ABI it is saved at SP + 40.
+      if (R::getArch() == REGISTERS_PPC64 && returnAddress != 0) {
+        pint_t sp = newRegisters.getRegister(UNW_REG_SP);
+        pint_t r2 = 0;
+        switch (addressSpace.get32(returnAddress)) {
+        case PPC64_ELFV1_R2_LOAD_INST_ENCODING:
+          r2 = addressSpace.get64(sp + PPC64_ELFV1_R2_OFFSET);
+          break;
+        case PPC64_ELFV2_R2_LOAD_INST_ENCODING:
+          r2 = addressSpace.get64(sp + PPC64_ELFV2_R2_OFFSET);
+          break;
+        }
+        if (r2)
+          newRegisters.setRegister(UNW_PPC64_R2, r2);
+      }
+#endif
+
+      // Return address is address after call site instruction, so setting IP to
+      // that does simulates a return.
+      newRegisters.setIP(returnAddress);
+
+      // Simulate the step by replacing the register set with the new ones.
+      registers = newRegisters;
+
+      return UNW_STEP_SUCCESS;
+    }
+  }
+  return UNW_EBADFRAME;
+}
+
+template <typename A, typename R>
+typename A::pint_t
+DwarfInstructions<A, R>::evaluateExpression(pint_t expression, A &addressSpace,
+                                            const R &registers,
+                                            pint_t initialStackValue) {
+  const bool log = false;
+  pint_t p = expression;
+  pint_t expressionEnd = expression + 20; // temp, until len read
+  pint_t length = (pint_t)addressSpace.getULEB128(p, expressionEnd);
+  expressionEnd = p + length;
+  if (log)
+    fprintf(stderr, "evaluateExpression(): length=%" PRIu64 "\n",
+            (uint64_t)length);
+  pint_t stack[100];
+  pint_t *sp = stack;
+  *(++sp) = initialStackValue;
+
+  while (p < expressionEnd) {
+    if (log) {
+      for (pint_t *t = sp; t > stack; --t) {
+        fprintf(stderr, "sp[] = 0x%" PRIx64 "\n", (uint64_t)(*t));
+      }
+    }
+    uint8_t opcode = addressSpace.get8(p++);
+    sint_t svalue, svalue2;
+    pint_t value;
+    uint32_t reg;
+    switch (opcode) {
+    case DW_OP_addr:
+      // push immediate address sized value
+      value = addressSpace.getP(p);
+      p += sizeof(pint_t);
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_deref:
+      // pop stack, dereference, push result
+      value = *sp--;
+      *(++sp) = addressSpace.getP(value);
+      if (log)
+        fprintf(stderr, "dereference 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_const1u:
+      // push immediate 1 byte value
+      value = addressSpace.get8(p);
+      p += 1;
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_const1s:
+      // push immediate 1 byte signed value
+      svalue = (int8_t) addressSpace.get8(p);
+      p += 1;
+      *(++sp) = (pint_t)svalue;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)svalue);
+      break;
+
+    case DW_OP_const2u:
+      // push immediate 2 byte value
+      value = addressSpace.get16(p);
+      p += 2;
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_const2s:
+      // push immediate 2 byte signed value
+      svalue = (int16_t) addressSpace.get16(p);
+      p += 2;
+      *(++sp) = (pint_t)svalue;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)svalue);
+      break;
+
+    case DW_OP_const4u:
+      // push immediate 4 byte value
+      value = addressSpace.get32(p);
+      p += 4;
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_const4s:
+      // push immediate 4 byte signed value
+      svalue = (int32_t)addressSpace.get32(p);
+      p += 4;
+      *(++sp) = (pint_t)svalue;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)svalue);
+      break;
+
+    case DW_OP_const8u:
+      // push immediate 8 byte value
+      value = (pint_t)addressSpace.get64(p);
+      p += 8;
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_const8s:
+      // push immediate 8 byte signed value
+      value = (pint_t)addressSpace.get64(p);
+      p += 8;
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_constu:
+      // push immediate ULEB128 value
+      value = (pint_t)addressSpace.getULEB128(p, expressionEnd);
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_consts:
+      // push immediate SLEB128 value
+      svalue = (sint_t)addressSpace.getSLEB128(p, expressionEnd);
+      *(++sp) = (pint_t)svalue;
+      if (log)
+        fprintf(stderr, "push 0x%" PRIx64 "\n", (uint64_t)svalue);
+      break;
+
+    case DW_OP_dup:
+      // push top of stack
+      value = *sp;
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "duplicate top of stack\n");
+      break;
+
+    case DW_OP_drop:
+      // pop
+      --sp;
+      if (log)
+        fprintf(stderr, "pop top of stack\n");
+      break;
+
+    case DW_OP_over:
+      // dup second
+      value = sp[-1];
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "duplicate second in stack\n");
+      break;
+
+    case DW_OP_pick:
+      // pick from
+      reg = addressSpace.get8(p);
+      p += 1;
+      value = sp[-(int)reg];
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "duplicate %d in stack\n", reg);
+      break;
+
+    case DW_OP_swap:
+      // swap top two
+      value = sp[0];
+      sp[0] = sp[-1];
+      sp[-1] = value;
+      if (log)
+        fprintf(stderr, "swap top of stack\n");
+      break;
+
+    case DW_OP_rot:
+      // rotate top three
+      value = sp[0];
+      sp[0] = sp[-1];
+      sp[-1] = sp[-2];
+      sp[-2] = value;
+      if (log)
+        fprintf(stderr, "rotate top three of stack\n");
+      break;
+
+    case DW_OP_xderef:
+      // pop stack, dereference, push result
+      value = *sp--;
+      *sp = *((pint_t*)value);
+      if (log)
+        fprintf(stderr, "x-dereference 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_abs:
+      svalue = (sint_t)*sp;
+      if (svalue < 0)
+        *sp = (pint_t)(-svalue);
+      if (log)
+        fprintf(stderr, "abs\n");
+      break;
+
+    case DW_OP_and:
+      value = *sp--;
+      *sp &= value;
+      if (log)
+        fprintf(stderr, "and\n");
+      break;
+
+    case DW_OP_div:
+      svalue = (sint_t)(*sp--);
+      svalue2 = (sint_t)*sp;
+      *sp = (pint_t)(svalue2 / svalue);
+      if (log)
+        fprintf(stderr, "div\n");
+      break;
+
+    case DW_OP_minus:
+      value = *sp--;
+      *sp = *sp - value;
+      if (log)
+        fprintf(stderr, "minus\n");
+      break;
+
+    case DW_OP_mod:
+      svalue = (sint_t)(*sp--);
+      svalue2 = (sint_t)*sp;
+      *sp = (pint_t)(svalue2 % svalue);
+      if (log)
+        fprintf(stderr, "module\n");
+      break;
+
+    case DW_OP_mul:
+      svalue = (sint_t)(*sp--);
+      svalue2 = (sint_t)*sp;
+      *sp = (pint_t)(svalue2 * svalue);
+      if (log)
+        fprintf(stderr, "mul\n");
+      break;
+
+    case DW_OP_neg:
+      *sp = 0 - *sp;
+      if (log)
+        fprintf(stderr, "neg\n");
+      break;
+
+    case DW_OP_not:
+      svalue = (sint_t)(*sp);
+      *sp = (pint_t)(~svalue);
+      if (log)
+        fprintf(stderr, "not\n");
+      break;
+
+    case DW_OP_or:
+      value = *sp--;
+      *sp |= value;
+      if (log)
+        fprintf(stderr, "or\n");
+      break;
+
+    case DW_OP_plus:
+      value = *sp--;
+      *sp += value;
+      if (log)
+        fprintf(stderr, "plus\n");
+      break;
+
+    case DW_OP_plus_uconst:
+      // pop stack, add uelb128 constant, push result
+      *sp += static_cast<pint_t>(addressSpace.getULEB128(p, expressionEnd));
+      if (log)
+        fprintf(stderr, "add constant\n");
+      break;
+
+    case DW_OP_shl:
+      value = *sp--;
+      *sp = *sp << value;
+      if (log)
+        fprintf(stderr, "shift left\n");
+      break;
+
+    case DW_OP_shr:
+      value = *sp--;
+      *sp = *sp >> value;
+      if (log)
+        fprintf(stderr, "shift left\n");
+      break;
+
+    case DW_OP_shra:
+      value = *sp--;
+      svalue = (sint_t)*sp;
+      *sp = (pint_t)(svalue >> value);
+      if (log)
+        fprintf(stderr, "shift left arithmetic\n");
+      break;
+
+    case DW_OP_xor:
+      value = *sp--;
+      *sp ^= value;
+      if (log)
+        fprintf(stderr, "xor\n");
+      break;
+
+    case DW_OP_skip:
+      svalue = (int16_t) addressSpace.get16(p);
+      p += 2;
+      p = (pint_t)((sint_t)p + svalue);
+      if (log)
+        fprintf(stderr, "skip %" PRIu64 "\n", (uint64_t)svalue);
+      break;
+
+    case DW_OP_bra:
+      svalue = (int16_t) addressSpace.get16(p);
+      p += 2;
+      if (*sp--)
+        p = (pint_t)((sint_t)p + svalue);
+      if (log)
+        fprintf(stderr, "bra %" PRIu64 "\n", (uint64_t)svalue);
+      break;
+
+    case DW_OP_eq:
+      value = *sp--;
+      *sp = (*sp == value);
+      if (log)
+        fprintf(stderr, "eq\n");
+      break;
+
+    case DW_OP_ge:
+      value = *sp--;
+      *sp = (*sp >= value);
+      if (log)
+        fprintf(stderr, "ge\n");
+      break;
+
+    case DW_OP_gt:
+      value = *sp--;
+      *sp = (*sp > value);
+      if (log)
+        fprintf(stderr, "gt\n");
+      break;
+
+    case DW_OP_le:
+      value = *sp--;
+      *sp = (*sp <= value);
+      if (log)
+        fprintf(stderr, "le\n");
+      break;
+
+    case DW_OP_lt:
+      value = *sp--;
+      *sp = (*sp < value);
+      if (log)
+        fprintf(stderr, "lt\n");
+      break;
+
+    case DW_OP_ne:
+      value = *sp--;
+      *sp = (*sp != value);
+      if (log)
+        fprintf(stderr, "ne\n");
+      break;
+
+    case DW_OP_lit0:
+    case DW_OP_lit1:
+    case DW_OP_lit2:
+    case DW_OP_lit3:
+    case DW_OP_lit4:
+    case DW_OP_lit5:
+    case DW_OP_lit6:
+    case DW_OP_lit7:
+    case DW_OP_lit8:
+    case DW_OP_lit9:
+    case DW_OP_lit10:
+    case DW_OP_lit11:
+    case DW_OP_lit12:
+    case DW_OP_lit13:
+    case DW_OP_lit14:
+    case DW_OP_lit15:
+    case DW_OP_lit16:
+    case DW_OP_lit17:
+    case DW_OP_lit18:
+    case DW_OP_lit19:
+    case DW_OP_lit20:
+    case DW_OP_lit21:
+    case DW_OP_lit22:
+    case DW_OP_lit23:
+    case DW_OP_lit24:
+    case DW_OP_lit25:
+    case DW_OP_lit26:
+    case DW_OP_lit27:
+    case DW_OP_lit28:
+    case DW_OP_lit29:
+    case DW_OP_lit30:
+    case DW_OP_lit31:
+      value = static_cast<pint_t>(opcode - DW_OP_lit0);
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "push literal 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_reg0:
+    case DW_OP_reg1:
+    case DW_OP_reg2:
+    case DW_OP_reg3:
+    case DW_OP_reg4:
+    case DW_OP_reg5:
+    case DW_OP_reg6:
+    case DW_OP_reg7:
+    case DW_OP_reg8:
+    case DW_OP_reg9:
+    case DW_OP_reg10:
+    case DW_OP_reg11:
+    case DW_OP_reg12:
+    case DW_OP_reg13:
+    case DW_OP_reg14:
+    case DW_OP_reg15:
+    case DW_OP_reg16:
+    case DW_OP_reg17:
+    case DW_OP_reg18:
+    case DW_OP_reg19:
+    case DW_OP_reg20:
+    case DW_OP_reg21:
+    case DW_OP_reg22:
+    case DW_OP_reg23:
+    case DW_OP_reg24:
+    case DW_OP_reg25:
+    case DW_OP_reg26:
+    case DW_OP_reg27:
+    case DW_OP_reg28:
+    case DW_OP_reg29:
+    case DW_OP_reg30:
+    case DW_OP_reg31:
+      reg = static_cast<uint32_t>(opcode - DW_OP_reg0);
+      *(++sp) = registers.getRegister((int)reg);
+      if (log)
+        fprintf(stderr, "push reg %d\n", reg);
+      break;
+
+    case DW_OP_regx:
+      reg = static_cast<uint32_t>(addressSpace.getULEB128(p, expressionEnd));
+      *(++sp) = registers.getRegister((int)reg);
+      if (log)
+        fprintf(stderr, "push reg %d + 0x%" PRIx64 "\n", reg, (uint64_t)svalue);
+      break;
+
+    case DW_OP_breg0:
+    case DW_OP_breg1:
+    case DW_OP_breg2:
+    case DW_OP_breg3:
+    case DW_OP_breg4:
+    case DW_OP_breg5:
+    case DW_OP_breg6:
+    case DW_OP_breg7:
+    case DW_OP_breg8:
+    case DW_OP_breg9:
+    case DW_OP_breg10:
+    case DW_OP_breg11:
+    case DW_OP_breg12:
+    case DW_OP_breg13:
+    case DW_OP_breg14:
+    case DW_OP_breg15:
+    case DW_OP_breg16:
+    case DW_OP_breg17:
+    case DW_OP_breg18:
+    case DW_OP_breg19:
+    case DW_OP_breg20:
+    case DW_OP_breg21:
+    case DW_OP_breg22:
+    case DW_OP_breg23:
+    case DW_OP_breg24:
+    case DW_OP_breg25:
+    case DW_OP_breg26:
+    case DW_OP_breg27:
+    case DW_OP_breg28:
+    case DW_OP_breg29:
+    case DW_OP_breg30:
+    case DW_OP_breg31:
+      reg = static_cast<uint32_t>(opcode - DW_OP_breg0);
+      svalue = (sint_t)addressSpace.getSLEB128(p, expressionEnd);
+      svalue += static_cast<sint_t>(registers.getRegister((int)reg));
+      *(++sp) = (pint_t)(svalue);
+      if (log)
+        fprintf(stderr, "push reg %d + 0x%" PRIx64 "\n", reg, (uint64_t)svalue);
+      break;
+
+    case DW_OP_bregx:
+      reg = static_cast<uint32_t>(addressSpace.getULEB128(p, expressionEnd));
+      svalue = (sint_t)addressSpace.getSLEB128(p, expressionEnd);
+      svalue += static_cast<sint_t>(registers.getRegister((int)reg));
+      *(++sp) = (pint_t)(svalue);
+      if (log)
+        fprintf(stderr, "push reg %d + 0x%" PRIx64 "\n", reg, (uint64_t)svalue);
+      break;
+
+    case DW_OP_fbreg:
+      _LIBUNWIND_ABORT("DW_OP_fbreg not implemented");
+      break;
+
+    case DW_OP_piece:
+      _LIBUNWIND_ABORT("DW_OP_piece not implemented");
+      break;
+
+    case DW_OP_deref_size:
+      // pop stack, dereference, push result
+      value = *sp--;
+      switch (addressSpace.get8(p++)) {
+      case 1:
+        value = addressSpace.get8(value);
+        break;
+      case 2:
+        value = addressSpace.get16(value);
+        break;
+      case 4:
+        value = addressSpace.get32(value);
+        break;
+      case 8:
+        value = (pint_t)addressSpace.get64(value);
+        break;
+      default:
+        _LIBUNWIND_ABORT("DW_OP_deref_size with bad size");
+      }
+      *(++sp) = value;
+      if (log)
+        fprintf(stderr, "sized dereference 0x%" PRIx64 "\n", (uint64_t)value);
+      break;
+
+    case DW_OP_xderef_size:
+    case DW_OP_nop:
+    case DW_OP_push_object_addres:
+    case DW_OP_call2:
+    case DW_OP_call4:
+    case DW_OP_call_ref:
+    default:
+      _LIBUNWIND_ABORT("DWARF opcode not implemented");
+    }
+
+  }
+  if (log)
+    fprintf(stderr, "expression evaluates to 0x%" PRIx64 "\n", (uint64_t)*sp);
+  return *sp;
+}
+
+
+
+} // namespace libunwind
+
+#endif // __DWARF_INSTRUCTIONS_HPP__

third_party/libunwind/DwarfParser.hpp

@@ -0,0 +1,853 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Parses DWARF CFIs (FDEs and CIEs).
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __DWARF_PARSER_HPP__
+#define __DWARF_PARSER_HPP__
+
+#include "libc/isystem/inttypes.h"
+#include "libc/isystem/stdint.h"
+#include "libc/stdio/stdio.h"
+#include "libc/isystem/stdlib.h"
+
+#include "third_party/libunwind/include/libunwind.h"
+#include "third_party/libunwind/dwarf2.h"
+#include "third_party/libunwind/Registers.hpp"
+
+#include "third_party/libunwind/config.h"
+
+namespace libunwind {
+
+/// CFI_Parser does basic parsing of a CFI (Call Frame Information) records.
+/// See DWARF Spec for details:
+///    http://refspecs.linuxbase.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
+///
+template <typename A>
+class CFI_Parser {
+public:
+  typedef typename A::pint_t pint_t;
+
+  /// Information encoded in a CIE (Common Information Entry)
+  struct CIE_Info {
+    pint_t    cieStart;
+    pint_t    cieLength;
+    pint_t    cieInstructions;
+    uint8_t   pointerEncoding;
+    uint8_t   lsdaEncoding;
+    uint8_t   personalityEncoding;
+    uint8_t   personalityOffsetInCIE;
+    pint_t    personality;
+    uint32_t  codeAlignFactor;
+    int       dataAlignFactor;
+    bool      isSignalFrame;
+    bool      fdesHaveAugmentationData;
+    uint8_t   returnAddressRegister;
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+    bool      addressesSignedWithBKey;
+    bool      mteTaggedFrame;
+#endif
+  };
+
+  /// Information about an FDE (Frame Description Entry)
+  struct FDE_Info {
+    pint_t  fdeStart;
+    pint_t  fdeLength;
+    pint_t  fdeInstructions;
+    pint_t  pcStart;
+    pint_t  pcEnd;
+    pint_t  lsda;
+  };
+
+  enum {
+    kMaxRegisterNumber = _LIBUNWIND_HIGHEST_DWARF_REGISTER
+  };
+  enum RegisterSavedWhere {
+    kRegisterUnused,
+    kRegisterUndefined,
+    kRegisterInCFA,
+    kRegisterInCFADecrypt, // sparc64 specific
+    kRegisterOffsetFromCFA,
+    kRegisterInRegister,
+    kRegisterAtExpression,
+    kRegisterIsExpression
+  };
+  struct RegisterLocation {
+    RegisterSavedWhere location;
+    bool initialStateSaved;
+    int64_t value;
+  };
+  /// Information about a frame layout and registers saved determined
+  /// by "running" the DWARF FDE "instructions"
+  struct PrologInfo {
+    uint32_t          cfaRegister;
+    int32_t           cfaRegisterOffset;  // CFA = (cfaRegister)+cfaRegisterOffset
+    int64_t           cfaExpression;      // CFA = expression
+    uint32_t          spExtraArgSize;
+    RegisterLocation  savedRegisters[kMaxRegisterNumber + 1];
+    enum class InitializeTime { kLazy, kNormal };
+
+    // When saving registers, this data structure is lazily initialized.
+    PrologInfo(InitializeTime IT = InitializeTime::kNormal) {
+      if (IT == InitializeTime::kNormal)
+        memset(this, 0, sizeof(*this));
+    }
+    void checkSaveRegister(uint64_t reg, PrologInfo &initialState) {
+      if (!savedRegisters[reg].initialStateSaved) {
+        initialState.savedRegisters[reg] = savedRegisters[reg];
+        savedRegisters[reg].initialStateSaved = true;
+      }
+    }
+    void setRegister(uint64_t reg, RegisterSavedWhere newLocation,
+                     int64_t newValue, PrologInfo &initialState) {
+      checkSaveRegister(reg, initialState);
+      savedRegisters[reg].location = newLocation;
+      savedRegisters[reg].value = newValue;
+    }
+    void setRegisterLocation(uint64_t reg, RegisterSavedWhere newLocation,
+                             PrologInfo &initialState) {
+      checkSaveRegister(reg, initialState);
+      savedRegisters[reg].location = newLocation;
+    }
+    void setRegisterValue(uint64_t reg, int64_t newValue,
+                          PrologInfo &initialState) {
+      checkSaveRegister(reg, initialState);
+      savedRegisters[reg].value = newValue;
+    }
+    void restoreRegisterToInitialState(uint64_t reg, PrologInfo &initialState) {
+      if (savedRegisters[reg].initialStateSaved)
+        savedRegisters[reg] = initialState.savedRegisters[reg];
+      // else the register still holds its initial state
+    }
+  };
+
+  struct PrologInfoStackEntry {
+    PrologInfoStackEntry(PrologInfoStackEntry *n, const PrologInfo &i)
+        : next(n), info(i) {}
+    PrologInfoStackEntry *next;
+    PrologInfo info;
+  };
+
+  struct RememberStack {
+    PrologInfoStackEntry *entry;
+    RememberStack() : entry(nullptr) {}
+    ~RememberStack() {
+#if defined(_LIBUNWIND_REMEMBER_CLEANUP_NEEDED)
+      // Clean up rememberStack. Even in the case where every
+      // DW_CFA_remember_state is paired with a DW_CFA_restore_state,
+      // parseInstructions can skip restore opcodes if it reaches the target PC
+      // and stops interpreting, so we have to make sure we don't leak memory.
+      while (entry) {
+        PrologInfoStackEntry *next = entry->next;
+        _LIBUNWIND_REMEMBER_FREE(entry);
+        entry = next;
+      }
+#endif
+    }
+  };
+
+  static bool findFDE(A &addressSpace, pint_t pc, pint_t ehSectionStart,
+                      size_t sectionLength, pint_t fdeHint, FDE_Info *fdeInfo,
+                      CIE_Info *cieInfo);
+  static const char *decodeFDE(A &addressSpace, pint_t fdeStart,
+                               FDE_Info *fdeInfo, CIE_Info *cieInfo,
+                               bool useCIEInfo = false);
+  static bool parseFDEInstructions(A &addressSpace, const FDE_Info &fdeInfo,
+                                   const CIE_Info &cieInfo, pint_t upToPC,
+                                   int arch, PrologInfo *results);
+
+  static const char *parseCIE(A &addressSpace, pint_t cie, CIE_Info *cieInfo);
+};
+
+/// Parse a FDE into a CIE_Info and an FDE_Info. If useCIEInfo is
+/// true, treat cieInfo as already-parsed CIE_Info (whose start offset
+/// must match the one specified by the FDE) rather than parsing the
+/// one indicated within the FDE.
+template <typename A>
+const char *CFI_Parser<A>::decodeFDE(A &addressSpace, pint_t fdeStart,
+                                     FDE_Info *fdeInfo, CIE_Info *cieInfo,
+                                     bool useCIEInfo) {
+  pint_t p = fdeStart;
+  pint_t cfiLength = (pint_t)addressSpace.get32(p);
+  p += 4;
+  if (cfiLength == 0xffffffff) {
+    // 0xffffffff means length is really next 8 bytes
+    cfiLength = (pint_t)addressSpace.get64(p);
+    p += 8;
+  }
+  if (cfiLength == 0)
+    return "FDE has zero length"; // zero terminator
+  uint32_t ciePointer = addressSpace.get32(p);
+  if (ciePointer == 0)
+    return "FDE is really a CIE"; // this is a CIE not an FDE
+  pint_t nextCFI = p + cfiLength;
+  pint_t cieStart = p - ciePointer;
+  if (useCIEInfo) {
+    if (cieInfo->cieStart != cieStart)
+      return "CIE start does not match";
+  } else {
+    const char *err = parseCIE(addressSpace, cieStart, cieInfo);
+    if (err != NULL)
+      return err;
+  }
+  p += 4;
+  // Parse pc begin and range.
+  pint_t pcStart =
+      addressSpace.getEncodedP(p, nextCFI, cieInfo->pointerEncoding);
+  pint_t pcRange =
+      addressSpace.getEncodedP(p, nextCFI, cieInfo->pointerEncoding & 0x0F);
+  // Parse rest of info.
+  fdeInfo->lsda = 0;
+  // Check for augmentation length.
+  if (cieInfo->fdesHaveAugmentationData) {
+    pint_t augLen = (pint_t)addressSpace.getULEB128(p, nextCFI);
+    pint_t endOfAug = p + augLen;
+    if (cieInfo->lsdaEncoding != DW_EH_PE_omit) {
+      // Peek at value (without indirection).  Zero means no LSDA.
+      pint_t lsdaStart = p;
+      if (addressSpace.getEncodedP(p, nextCFI, cieInfo->lsdaEncoding & 0x0F) !=
+          0) {
+        // Reset pointer and re-parse LSDA address.
+        p = lsdaStart;
+        fdeInfo->lsda =
+            addressSpace.getEncodedP(p, nextCFI, cieInfo->lsdaEncoding);
+      }
+    }
+    p = endOfAug;
+  }
+  fdeInfo->fdeStart = fdeStart;
+  fdeInfo->fdeLength = nextCFI - fdeStart;
+  fdeInfo->fdeInstructions = p;
+  fdeInfo->pcStart = pcStart;
+  fdeInfo->pcEnd = pcStart + pcRange;
+  return NULL; // success
+}
+
+/// Scan an eh_frame section to find an FDE for a pc
+template <typename A>
+bool CFI_Parser<A>::findFDE(A &addressSpace, pint_t pc, pint_t ehSectionStart,
+                            size_t sectionLength, pint_t fdeHint,
+                            FDE_Info *fdeInfo, CIE_Info *cieInfo) {
+  //fprintf(stderr, "findFDE(0x%llX)\n", (long long)pc);
+  pint_t p = (fdeHint != 0) ? fdeHint : ehSectionStart;
+  const pint_t ehSectionEnd = (sectionLength == SIZE_MAX)
+                                  ? static_cast<pint_t>(-1)
+                                  : (ehSectionStart + sectionLength);
+  while (p < ehSectionEnd) {
+    pint_t currentCFI = p;
+    //fprintf(stderr, "findFDE() CFI at 0x%llX\n", (long long)p);
+    pint_t cfiLength = addressSpace.get32(p);
+    p += 4;
+    if (cfiLength == 0xffffffff) {
+      // 0xffffffff means length is really next 8 bytes
+      cfiLength = (pint_t)addressSpace.get64(p);
+      p += 8;
+    }
+    if (cfiLength == 0)
+      return false; // zero terminator
+    uint32_t id = addressSpace.get32(p);
+    if (id == 0) {
+      // Skip over CIEs.
+      p += cfiLength;
+    } else {
+      // Process FDE to see if it covers pc.
+      pint_t nextCFI = p + cfiLength;
+      uint32_t ciePointer = addressSpace.get32(p);
+      pint_t cieStart = p - ciePointer;
+      // Validate pointer to CIE is within section.
+      if ((ehSectionStart <= cieStart) && (cieStart < ehSectionEnd)) {
+        if (parseCIE(addressSpace, cieStart, cieInfo) == NULL) {
+          p += 4;
+          // Parse pc begin and range.
+          pint_t pcStart =
+              addressSpace.getEncodedP(p, nextCFI, cieInfo->pointerEncoding);
+          pint_t pcRange = addressSpace.getEncodedP(
+              p, nextCFI, cieInfo->pointerEncoding & 0x0F);
+          // Test if pc is within the function this FDE covers.
+          if ((pcStart < pc) && (pc <= pcStart + pcRange)) {
+            // parse rest of info
+            fdeInfo->lsda = 0;
+            // check for augmentation length
+            if (cieInfo->fdesHaveAugmentationData) {
+              pint_t augLen = (pint_t)addressSpace.getULEB128(p, nextCFI);
+              pint_t endOfAug = p + augLen;
+              if (cieInfo->lsdaEncoding != DW_EH_PE_omit) {
+                // Peek at value (without indirection).  Zero means no LSDA.
+                pint_t lsdaStart = p;
+                if (addressSpace.getEncodedP(
+                        p, nextCFI, cieInfo->lsdaEncoding & 0x0F) != 0) {
+                  // Reset pointer and re-parse LSDA address.
+                  p = lsdaStart;
+                  fdeInfo->lsda = addressSpace
+                      .getEncodedP(p, nextCFI, cieInfo->lsdaEncoding);
+                }
+              }
+              p = endOfAug;
+            }
+            fdeInfo->fdeStart = currentCFI;
+            fdeInfo->fdeLength = nextCFI - currentCFI;
+            fdeInfo->fdeInstructions = p;
+            fdeInfo->pcStart = pcStart;
+            fdeInfo->pcEnd = pcStart + pcRange;
+            return true;
+          } else {
+            // pc is not in begin/range, skip this FDE
+          }
+        } else {
+          // Malformed CIE, now augmentation describing pc range encoding.
+        }
+      } else {
+        // malformed FDE.  CIE is bad
+      }
+      p = nextCFI;
+    }
+  }
+  return false;
+}
+
+/// Extract info from a CIE
+template <typename A>
+const char *CFI_Parser<A>::parseCIE(A &addressSpace, pint_t cie,
+                                    CIE_Info *cieInfo) {
+  cieInfo->pointerEncoding = 0;
+  cieInfo->lsdaEncoding = DW_EH_PE_omit;
+  cieInfo->personalityEncoding = 0;
+  cieInfo->personalityOffsetInCIE = 0;
+  cieInfo->personality = 0;
+  cieInfo->codeAlignFactor = 0;
+  cieInfo->dataAlignFactor = 0;
+  cieInfo->isSignalFrame = false;
+  cieInfo->fdesHaveAugmentationData = false;
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+  cieInfo->addressesSignedWithBKey = false;
+  cieInfo->mteTaggedFrame = false;
+#endif
+  cieInfo->cieStart = cie;
+  pint_t p = cie;
+  pint_t cieLength = (pint_t)addressSpace.get32(p);
+  p += 4;
+  pint_t cieContentEnd = p + cieLength;
+  if (cieLength == 0xffffffff) {
+    // 0xffffffff means length is really next 8 bytes
+    cieLength = (pint_t)addressSpace.get64(p);
+    p += 8;
+    cieContentEnd = p + cieLength;
+  }
+  if (cieLength == 0)
+    return NULL;
+  // CIE ID is always 0
+  if (addressSpace.get32(p) != 0)
+    return "CIE ID is not zero";
+  p += 4;
+  // Version is always 1 or 3
+  uint8_t version = addressSpace.get8(p);
+  if ((version != 1) && (version != 3))
+    return "CIE version is not 1 or 3";
+  ++p;
+  // save start of augmentation string and find end
+  pint_t strStart = p;
+  while (addressSpace.get8(p) != 0)
+    ++p;
+  ++p;
+  // parse code alignment factor
+  cieInfo->codeAlignFactor = (uint32_t)addressSpace.getULEB128(p, cieContentEnd);
+  // parse data alignment factor
+  cieInfo->dataAlignFactor = (int)addressSpace.getSLEB128(p, cieContentEnd);
+  // parse return address register
+  uint64_t raReg = (version == 1) ? addressSpace.get8(p++)
+                                  : addressSpace.getULEB128(p, cieContentEnd);
+  assert(raReg < 255 && "return address register too large");
+  cieInfo->returnAddressRegister = (uint8_t)raReg;
+  // parse augmentation data based on augmentation string
+  const char *result = NULL;
+  if (addressSpace.get8(strStart) == 'z') {
+    // parse augmentation data length
+    addressSpace.getULEB128(p, cieContentEnd);
+    for (pint_t s = strStart; addressSpace.get8(s) != '\0'; ++s) {
+      switch (addressSpace.get8(s)) {
+      case 'z':
+        cieInfo->fdesHaveAugmentationData = true;
+        break;
+      case 'P':
+        cieInfo->personalityEncoding = addressSpace.get8(p);
+        ++p;
+        cieInfo->personalityOffsetInCIE = (uint8_t)(p - cie);
+        cieInfo->personality = addressSpace
+            .getEncodedP(p, cieContentEnd, cieInfo->personalityEncoding);
+        break;
+      case 'L':
+        cieInfo->lsdaEncoding = addressSpace.get8(p);
+        ++p;
+        break;
+      case 'R':
+        cieInfo->pointerEncoding = addressSpace.get8(p);
+        ++p;
+        break;
+      case 'S':
+        cieInfo->isSignalFrame = true;
+        break;
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+      case 'B':
+        cieInfo->addressesSignedWithBKey = true;
+        break;
+      case 'G':
+        cieInfo->mteTaggedFrame = true;
+        break;
+#endif
+      default:
+        // ignore unknown letters
+        break;
+      }
+    }
+  }
+  cieInfo->cieLength = cieContentEnd - cieInfo->cieStart;
+  cieInfo->cieInstructions = p;
+  return result;
+}
+
+
+/// "run" the DWARF instructions and create the abstract PrologInfo for an FDE
+template <typename A>
+bool CFI_Parser<A>::parseFDEInstructions(A &addressSpace,
+                                         const FDE_Info &fdeInfo,
+                                         const CIE_Info &cieInfo, pint_t upToPC,
+                                         int arch, PrologInfo *results) {
+  // Alloca is used for the allocation of the rememberStack entries. It removes
+  // the dependency on new/malloc but the below for loop can not be refactored
+  // into functions. Entry could be saved during the processing of a CIE and
+  // restored by an FDE.
+  RememberStack rememberStack;
+
+  struct ParseInfo {
+    pint_t instructions;
+    pint_t instructionsEnd;
+    pint_t pcoffset;
+  };
+
+  ParseInfo parseInfoArray[] = {
+      {cieInfo.cieInstructions, cieInfo.cieStart + cieInfo.cieLength,
+       (pint_t)(-1)},
+      {fdeInfo.fdeInstructions, fdeInfo.fdeStart + fdeInfo.fdeLength,
+       upToPC - fdeInfo.pcStart}};
+
+  for (const auto &info : parseInfoArray) {
+    pint_t p = info.instructions;
+    pint_t instructionsEnd = info.instructionsEnd;
+    pint_t pcoffset = info.pcoffset;
+    pint_t codeOffset = 0;
+
+    // initialState initialized as registers in results are modified. Use
+    // PrologInfo accessor functions to avoid reading uninitialized data.
+    PrologInfo initialState(PrologInfo::InitializeTime::kLazy);
+
+    _LIBUNWIND_TRACE_DWARF("parseFDEInstructions(instructions=0x%0" PRIx64
+                           ")\n",
+                           static_cast<uint64_t>(instructionsEnd));
+
+    // see DWARF Spec, section 6.4.2 for details on unwind opcodes
+    while ((p < instructionsEnd) && (codeOffset < pcoffset)) {
+      uint64_t reg;
+      uint64_t reg2;
+      int64_t offset;
+      uint64_t length;
+      uint8_t opcode = addressSpace.get8(p);
+      uint8_t operand;
+
+      ++p;
+      switch (opcode) {
+      case DW_CFA_nop:
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_nop\n");
+        break;
+      case DW_CFA_set_loc:
+        codeOffset = addressSpace.getEncodedP(p, instructionsEnd,
+                                              cieInfo.pointerEncoding);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_set_loc\n");
+        break;
+      case DW_CFA_advance_loc1:
+        codeOffset += (addressSpace.get8(p) * cieInfo.codeAlignFactor);
+        p += 1;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_advance_loc1: new offset=%" PRIu64 "\n",
+                               static_cast<uint64_t>(codeOffset));
+        break;
+      case DW_CFA_advance_loc2:
+        codeOffset += (addressSpace.get16(p) * cieInfo.codeAlignFactor);
+        p += 2;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_advance_loc2: new offset=%" PRIu64 "\n",
+                               static_cast<uint64_t>(codeOffset));
+        break;
+      case DW_CFA_advance_loc4:
+        codeOffset += (addressSpace.get32(p) * cieInfo.codeAlignFactor);
+        p += 4;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_advance_loc4: new offset=%" PRIu64 "\n",
+                               static_cast<uint64_t>(codeOffset));
+        break;
+      case DW_CFA_offset_extended:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        offset = (int64_t)addressSpace.getULEB128(p, instructionsEnd) *
+                 cieInfo.dataAlignFactor;
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_offset_extended DWARF unwind, reg too big");
+          return false;
+        }
+        results->setRegister(reg, kRegisterInCFA, offset, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_offset_extended(reg=%" PRIu64 ", "
+                               "offset=%" PRId64 ")\n",
+                               reg, offset);
+        break;
+      case DW_CFA_restore_extended:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_restore_extended DWARF unwind, reg too big");
+          return false;
+        }
+        results->restoreRegisterToInitialState(reg, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_restore_extended(reg=%" PRIu64 ")\n",
+                               reg);
+        break;
+      case DW_CFA_undefined:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_undefined DWARF unwind, reg too big");
+          return false;
+        }
+        results->setRegisterLocation(reg, kRegisterUndefined, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_undefined(reg=%" PRIu64 ")\n", reg);
+        break;
+      case DW_CFA_same_value:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_same_value DWARF unwind, reg too big");
+          return false;
+        }
+        // <rdar://problem/8456377> DW_CFA_same_value unsupported
+        // "same value" means register was stored in frame, but its current
+        // value has not changed, so no need to restore from frame.
+        // We model this as if the register was never saved.
+        results->setRegisterLocation(reg, kRegisterUnused, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_same_value(reg=%" PRIu64 ")\n", reg);
+        break;
+      case DW_CFA_register:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        reg2 = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_register DWARF unwind, reg too big");
+          return false;
+        }
+        if (reg2 > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_register DWARF unwind, reg2 too big");
+          return false;
+        }
+        results->setRegister(reg, kRegisterInRegister, (int64_t)reg2,
+                             initialState);
+        _LIBUNWIND_TRACE_DWARF(
+            "DW_CFA_register(reg=%" PRIu64 ", reg2=%" PRIu64 ")\n", reg, reg2);
+        break;
+      case DW_CFA_remember_state: {
+        // Avoid operator new because that would be an upward dependency.
+        // Avoid malloc because it needs heap allocation.
+        PrologInfoStackEntry *entry =
+            (PrologInfoStackEntry *)_LIBUNWIND_REMEMBER_ALLOC(
+                sizeof(PrologInfoStackEntry));
+        if (entry != NULL) {
+          entry->next = rememberStack.entry;
+          entry->info = *results;
+          rememberStack.entry = entry;
+        } else {
+          return false;
+        }
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_remember_state\n");
+        break;
+      }
+      case DW_CFA_restore_state:
+        if (rememberStack.entry != NULL) {
+          PrologInfoStackEntry *top = rememberStack.entry;
+          *results = top->info;
+          rememberStack.entry = top->next;
+          _LIBUNWIND_REMEMBER_FREE(top);
+        } else {
+          return false;
+        }
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_restore_state\n");
+        break;
+      case DW_CFA_def_cfa:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        offset = (int64_t)addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0("malformed DW_CFA_def_cfa DWARF unwind, reg too big");
+          return false;
+        }
+        results->cfaRegister = (uint32_t)reg;
+        results->cfaRegisterOffset = (int32_t)offset;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_def_cfa(reg=%" PRIu64 ", offset=%" PRIu64
+                               ")\n",
+                               reg, offset);
+        break;
+      case DW_CFA_def_cfa_register:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_def_cfa_register DWARF unwind, reg too big");
+          return false;
+        }
+        results->cfaRegister = (uint32_t)reg;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_def_cfa_register(%" PRIu64 ")\n", reg);
+        break;
+      case DW_CFA_def_cfa_offset:
+        results->cfaRegisterOffset =
+            (int32_t)addressSpace.getULEB128(p, instructionsEnd);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_def_cfa_offset(%d)\n",
+                               results->cfaRegisterOffset);
+        break;
+      case DW_CFA_def_cfa_expression:
+        results->cfaRegister = 0;
+        results->cfaExpression = (int64_t)p;
+        length = addressSpace.getULEB128(p, instructionsEnd);
+        assert(length < static_cast<pint_t>(~0) && "pointer overflow");
+        p += static_cast<pint_t>(length);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_def_cfa_expression(expression=0x%" PRIx64
+                               ", length=%" PRIu64 ")\n",
+                               results->cfaExpression, length);
+        break;
+      case DW_CFA_expression:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_expression DWARF unwind, reg too big");
+          return false;
+        }
+        results->setRegister(reg, kRegisterAtExpression, (int64_t)p,
+                             initialState);
+        length = addressSpace.getULEB128(p, instructionsEnd);
+        assert(length < static_cast<pint_t>(~0) && "pointer overflow");
+        p += static_cast<pint_t>(length);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_expression(reg=%" PRIu64 ", "
+                               "expression=0x%" PRIx64 ", "
+                               "length=%" PRIu64 ")\n",
+                               reg, results->savedRegisters[reg].value, length);
+        break;
+      case DW_CFA_offset_extended_sf:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_offset_extended_sf DWARF unwind, reg too big");
+          return false;
+        }
+        offset = addressSpace.getSLEB128(p, instructionsEnd) *
+                 cieInfo.dataAlignFactor;
+        results->setRegister(reg, kRegisterInCFA, offset, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_offset_extended_sf(reg=%" PRIu64 ", "
+                               "offset=%" PRId64 ")\n",
+                               reg, offset);
+        break;
+      case DW_CFA_def_cfa_sf:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        offset = addressSpace.getSLEB128(p, instructionsEnd) *
+                 cieInfo.dataAlignFactor;
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_def_cfa_sf DWARF unwind, reg too big");
+          return false;
+        }
+        results->cfaRegister = (uint32_t)reg;
+        results->cfaRegisterOffset = (int32_t)offset;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_def_cfa_sf(reg=%" PRIu64 ", "
+                               "offset=%" PRId64 ")\n",
+                               reg, offset);
+        break;
+      case DW_CFA_def_cfa_offset_sf:
+        results->cfaRegisterOffset =
+            (int32_t)(addressSpace.getSLEB128(p, instructionsEnd) *
+                      cieInfo.dataAlignFactor);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_def_cfa_offset_sf(%d)\n",
+                               results->cfaRegisterOffset);
+        break;
+      case DW_CFA_val_offset:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG(
+              "malformed DW_CFA_val_offset DWARF unwind, reg (%" PRIu64
+              ") out of range\n",
+              reg);
+          return false;
+        }
+        offset = (int64_t)addressSpace.getULEB128(p, instructionsEnd) *
+                 cieInfo.dataAlignFactor;
+        results->setRegister(reg, kRegisterOffsetFromCFA, offset, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_val_offset(reg=%" PRIu64 ", "
+                               "offset=%" PRId64 "\n",
+                               reg, offset);
+        break;
+      case DW_CFA_val_offset_sf:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_val_offset_sf DWARF unwind, reg too big");
+          return false;
+        }
+        offset = addressSpace.getSLEB128(p, instructionsEnd) *
+                 cieInfo.dataAlignFactor;
+        results->setRegister(reg, kRegisterOffsetFromCFA, offset, initialState);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_val_offset_sf(reg=%" PRIu64 ", "
+                               "offset=%" PRId64 "\n",
+                               reg, offset);
+        break;
+      case DW_CFA_val_expression:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0(
+              "malformed DW_CFA_val_expression DWARF unwind, reg too big");
+          return false;
+        }
+        results->setRegister(reg, kRegisterIsExpression, (int64_t)p,
+                             initialState);
+        length = addressSpace.getULEB128(p, instructionsEnd);
+        assert(length < static_cast<pint_t>(~0) && "pointer overflow");
+        p += static_cast<pint_t>(length);
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_val_expression(reg=%" PRIu64 ", "
+                               "expression=0x%" PRIx64 ", length=%" PRIu64
+                               ")\n",
+                               reg, results->savedRegisters[reg].value, length);
+        break;
+      case DW_CFA_GNU_args_size:
+        length = addressSpace.getULEB128(p, instructionsEnd);
+        results->spExtraArgSize = (uint32_t)length;
+        _LIBUNWIND_TRACE_DWARF("DW_CFA_GNU_args_size(%" PRIu64 ")\n", length);
+        break;
+      case DW_CFA_GNU_negative_offset_extended:
+        reg = addressSpace.getULEB128(p, instructionsEnd);
+        if (reg > kMaxRegisterNumber) {
+          _LIBUNWIND_LOG0("malformed DW_CFA_GNU_negative_offset_extended DWARF "
+                          "unwind, reg too big");
+          return false;
+        }
+        offset = (int64_t)addressSpace.getULEB128(p, instructionsEnd) *
+                 cieInfo.dataAlignFactor;
+        results->setRegister(reg, kRegisterInCFA, -offset, initialState);
+        _LIBUNWIND_TRACE_DWARF(
+            "DW_CFA_GNU_negative_offset_extended(%" PRId64 ")\n", offset);
+        break;
+
+#if defined(_LIBUNWIND_TARGET_AARCH64) || defined(_LIBUNWIND_TARGET_SPARC) || \
+    defined(_LIBUNWIND_TARGET_SPARC64)
+        // The same constant is used to represent different instructions on
+        // AArch64 (negate_ra_state) and SPARC (window_save).
+        static_assert(DW_CFA_AARCH64_negate_ra_state == DW_CFA_GNU_window_save,
+                      "uses the same constant");
+      case DW_CFA_AARCH64_negate_ra_state:
+        switch (arch) {
+#if defined(_LIBUNWIND_TARGET_AARCH64)
+        case REGISTERS_ARM64: {
+          int64_t value =
+              results->savedRegisters[UNW_AARCH64_RA_SIGN_STATE].value ^ 0x1;
+          results->setRegisterValue(UNW_AARCH64_RA_SIGN_STATE, value,
+                                    initialState);
+          _LIBUNWIND_TRACE_DWARF("DW_CFA_AARCH64_negate_ra_state\n");
+        } break;
+#endif
+
+#if defined(_LIBUNWIND_TARGET_SPARC)
+        // case DW_CFA_GNU_window_save:
+        case REGISTERS_SPARC:
+          _LIBUNWIND_TRACE_DWARF("DW_CFA_GNU_window_save()\n");
+          for (reg = UNW_SPARC_O0; reg <= UNW_SPARC_O7; reg++) {
+            results->setRegister(reg, kRegisterInRegister,
+                                 ((int64_t)reg - UNW_SPARC_O0) + UNW_SPARC_I0,
+                                 initialState);
+          }
+
+          for (reg = UNW_SPARC_L0; reg <= UNW_SPARC_I7; reg++) {
+            results->setRegister(reg, kRegisterInCFA,
+                                 ((int64_t)reg - UNW_SPARC_L0) * 4,
+                                 initialState);
+          }
+          break;
+#endif
+
+#if defined(_LIBUNWIND_TARGET_SPARC64)
+        // case DW_CFA_GNU_window_save:
+        case REGISTERS_SPARC64:
+          // Don't save %o0-%o7 on sparc64.
+          // https://reviews.llvm.org/D32450#736405
+
+          for (reg = UNW_SPARC_L0; reg <= UNW_SPARC_I7; reg++) {
+            if (reg == UNW_SPARC_I7)
+              results->setRegister(
+                  reg, kRegisterInCFADecrypt,
+                  static_cast<int64_t>((reg - UNW_SPARC_L0) * sizeof(pint_t)),
+                  initialState);
+            else
+              results->setRegister(
+                  reg, kRegisterInCFA,
+                  static_cast<int64_t>((reg - UNW_SPARC_L0) * sizeof(pint_t)),
+                  initialState);
+          }
+          _LIBUNWIND_TRACE_DWARF("DW_CFA_GNU_window_save\n");
+          break;
+#endif
+        }
+        break;
+
+#else
+        (void)arch;
+#endif
+
+      default:
+        operand = opcode & 0x3F;
+        switch (opcode & 0xC0) {
+        case DW_CFA_offset:
+          reg = operand;
+          if (reg > kMaxRegisterNumber) {
+            _LIBUNWIND_LOG("malformed DW_CFA_offset DWARF unwind, reg (%" PRIu64
+                           ") out of range",
+                           reg);
+            return false;
+          }
+          offset = (int64_t)addressSpace.getULEB128(p, instructionsEnd) *
+                   cieInfo.dataAlignFactor;
+          results->setRegister(reg, kRegisterInCFA, offset, initialState);
+          _LIBUNWIND_TRACE_DWARF("DW_CFA_offset(reg=%d, offset=%" PRId64 ")\n",
+                                 operand, offset);
+          break;
+        case DW_CFA_advance_loc:
+          codeOffset += operand * cieInfo.codeAlignFactor;
+          _LIBUNWIND_TRACE_DWARF("DW_CFA_advance_loc: new offset=%" PRIu64 "\n",
+                                 static_cast<uint64_t>(codeOffset));
+          break;
+        case DW_CFA_restore:
+          reg = operand;
+          if (reg > kMaxRegisterNumber) {
+            _LIBUNWIND_LOG(
+                "malformed DW_CFA_restore DWARF unwind, reg (%" PRIu64
+                ") out of range",
+                reg);
+            return false;
+          }
+          results->restoreRegisterToInitialState(reg, initialState);
+          _LIBUNWIND_TRACE_DWARF("DW_CFA_restore(reg=%" PRIu64 ")\n",
+                                 static_cast<uint64_t>(operand));
+          break;
+        default:
+          _LIBUNWIND_TRACE_DWARF("unknown CFA opcode 0x%02X\n", opcode);
+          return false;
+        }
+      }
+    }
+  }
+  return true;
+}
+
+} // namespace libunwind
+
+#endif // __DWARF_PARSER_HPP__

third_party/libunwind/EHHeaderParser.hpp

@@ -0,0 +1,170 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Parses ELF .eh_frame_hdr sections.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __EHHEADERPARSER_HPP__
+#define __EHHEADERPARSER_HPP__
+
+#include "third_party/libunwind/include/libunwind.h"
+
+#include "third_party/libunwind/DwarfParser.hpp"
+
+namespace libunwind {
+
+/// \brief EHHeaderParser does basic parsing of an ELF .eh_frame_hdr section.
+///
+/// See DWARF spec for details:
+///    http://refspecs.linuxbase.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
+///
+template <typename A> class EHHeaderParser {
+public:
+  typedef typename A::pint_t pint_t;
+
+  /// Information encoded in the EH frame header.
+  struct EHHeaderInfo {
+    pint_t eh_frame_ptr;
+    size_t fde_count;
+    pint_t table;
+    uint8_t table_enc;
+  };
+
+  static bool decodeEHHdr(A &addressSpace, pint_t ehHdrStart, pint_t ehHdrEnd,
+                          EHHeaderInfo &ehHdrInfo);
+  static bool findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
+                      uint32_t sectionLength,
+                      typename CFI_Parser<A>::FDE_Info *fdeInfo,
+                      typename CFI_Parser<A>::CIE_Info *cieInfo);
+
+private:
+  static bool decodeTableEntry(A &addressSpace, pint_t &tableEntry,
+                               pint_t ehHdrStart, pint_t ehHdrEnd,
+                               uint8_t tableEnc,
+                               typename CFI_Parser<A>::FDE_Info *fdeInfo,
+                               typename CFI_Parser<A>::CIE_Info *cieInfo);
+  static size_t getTableEntrySize(uint8_t tableEnc);
+};
+
+template <typename A>
+bool EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart,
+                                    pint_t ehHdrEnd, EHHeaderInfo &ehHdrInfo) {
+  pint_t p = ehHdrStart;
+  uint8_t version = addressSpace.get8(p++);
+  if (version != 1) {
+    _LIBUNWIND_LOG("unsupported .eh_frame_hdr version: %" PRIu8 " at %" PRIx64,
+                   version, static_cast<uint64_t>(ehHdrStart));
+    return false;
+  }
+
+  uint8_t eh_frame_ptr_enc = addressSpace.get8(p++);
+  uint8_t fde_count_enc = addressSpace.get8(p++);
+  ehHdrInfo.table_enc = addressSpace.get8(p++);
+
+  ehHdrInfo.eh_frame_ptr =
+      addressSpace.getEncodedP(p, ehHdrEnd, eh_frame_ptr_enc, ehHdrStart);
+  ehHdrInfo.fde_count =
+      fde_count_enc == DW_EH_PE_omit
+          ? 0
+          : addressSpace.getEncodedP(p, ehHdrEnd, fde_count_enc, ehHdrStart);
+  ehHdrInfo.table = p;
+
+  return true;
+}
+
+template <typename A>
+bool EHHeaderParser<A>::decodeTableEntry(
+    A &addressSpace, pint_t &tableEntry, pint_t ehHdrStart, pint_t ehHdrEnd,
+    uint8_t tableEnc, typename CFI_Parser<A>::FDE_Info *fdeInfo,
+    typename CFI_Parser<A>::CIE_Info *cieInfo) {
+  // Have to decode the whole FDE for the PC range anyway, so just throw away
+  // the PC start.
+  addressSpace.getEncodedP(tableEntry, ehHdrEnd, tableEnc, ehHdrStart);
+  pint_t fde =
+      addressSpace.getEncodedP(tableEntry, ehHdrEnd, tableEnc, ehHdrStart);
+  const char *message =
+      CFI_Parser<A>::decodeFDE(addressSpace, fde, fdeInfo, cieInfo);
+  if (message != NULL) {
+    _LIBUNWIND_DEBUG_LOG("EHHeaderParser::decodeTableEntry: bad fde: %s",
+                         message);
+    return false;
+  }
+
+  return true;
+}
+
+template <typename A>
+bool EHHeaderParser<A>::findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
+                                uint32_t sectionLength,
+                                typename CFI_Parser<A>::FDE_Info *fdeInfo,
+                                typename CFI_Parser<A>::CIE_Info *cieInfo) {
+  pint_t ehHdrEnd = ehHdrStart + sectionLength;
+
+  EHHeaderParser<A>::EHHeaderInfo hdrInfo;
+  if (!EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, ehHdrEnd,
+                                      hdrInfo))
+    return false;
+
+  if (hdrInfo.fde_count == 0) return false;
+
+  size_t tableEntrySize = getTableEntrySize(hdrInfo.table_enc);
+  pint_t tableEntry;
+
+  size_t low = 0;
+  for (size_t len = hdrInfo.fde_count; len > 1;) {
+    size_t mid = low + (len / 2);
+    tableEntry = hdrInfo.table + mid * tableEntrySize;
+    pint_t start = addressSpace.getEncodedP(tableEntry, ehHdrEnd,
+                                            hdrInfo.table_enc, ehHdrStart);
+
+    if (start == pc) {
+      low = mid;
+      break;
+    } else if (start < pc) {
+      low = mid;
+      len -= (len / 2);
+    } else {
+      len /= 2;
+    }
+  }
+
+  tableEntry = hdrInfo.table + low * tableEntrySize;
+  if (decodeTableEntry(addressSpace, tableEntry, ehHdrStart, ehHdrEnd,
+                       hdrInfo.table_enc, fdeInfo, cieInfo)) {
+    if (pc >= fdeInfo->pcStart && pc < fdeInfo->pcEnd)
+      return true;
+  }
+
+  return false;
+}
+
+template <typename A>
+size_t EHHeaderParser<A>::getTableEntrySize(uint8_t tableEnc) {
+  switch (tableEnc & 0x0f) {
+  case DW_EH_PE_sdata2:
+  case DW_EH_PE_udata2:
+    return 4;
+  case DW_EH_PE_sdata4:
+  case DW_EH_PE_udata4:
+    return 8;
+  case DW_EH_PE_sdata8:
+  case DW_EH_PE_udata8:
+    return 16;
+  case DW_EH_PE_sleb128:
+  case DW_EH_PE_uleb128:
+    _LIBUNWIND_ABORT("Can't binary search on variable length encoded data.");
+  case DW_EH_PE_omit:
+    return 0;
+  default:
+    _LIBUNWIND_ABORT("Unknown DWARF encoding for search table.");
+  }
+}
+
+}
+
+#endif

third_party/libunwind/FrameHeaderCache.hpp

@@ -0,0 +1,149 @@
+//===-FrameHeaderCache.hpp ------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// Cache the elf program headers necessary to unwind the stack more efficiently
+// in the presence of many dsos.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __FRAMEHEADER_CACHE_HPP__
+#define __FRAMEHEADER_CACHE_HPP__
+
+#include "third_party/libunwind/config.h"
+#include "libc/isystem/limits.h"
+
+#ifdef _LIBUNWIND_DEBUG_FRAMEHEADER_CACHE
+#define _LIBUNWIND_FRAMEHEADERCACHE_TRACE0(x) _LIBUNWIND_LOG0(x)
+#define _LIBUNWIND_FRAMEHEADERCACHE_TRACE(msg, ...)                            \
+  _LIBUNWIND_LOG(msg, __VA_ARGS__)
+#else
+#define _LIBUNWIND_FRAMEHEADERCACHE_TRACE0(x)
+#define _LIBUNWIND_FRAMEHEADERCACHE_TRACE(msg, ...)
+#endif
+
+// This cache should only be be used from within a dl_iterate_phdr callback.
+// dl_iterate_phdr does the necessary synchronization to prevent problems
+// with concurrent access via the libc load lock. Adding synchronization
+// for other uses is possible, but not currently done.
+
+class _LIBUNWIND_HIDDEN FrameHeaderCache {
+  struct CacheEntry {
+    uintptr_t LowPC() { return Info.dso_base; };
+    uintptr_t HighPC() { return Info.dso_base + Info.text_segment_length; };
+    UnwindInfoSections Info;
+    CacheEntry *Next;
+  };
+
+  static const size_t kCacheEntryCount = 8;
+
+  // Can't depend on the C++ standard library in libunwind, so use an array to
+  // allocate the entries, and two linked lists for ordering unused and recently
+  // used entries.  FIXME: Would the the extra memory for a doubly-linked list
+  // be better than the runtime cost of traversing a very short singly-linked
+  // list on a cache miss? The entries themselves are all small and consecutive,
+  // so unlikely to cause page faults when following the pointers. The memory
+  // spent on additional pointers could also be spent on more entries.
+
+  CacheEntry Entries[kCacheEntryCount];
+  CacheEntry *MostRecentlyUsed;
+  CacheEntry *Unused;
+
+  void resetCache() {
+    _LIBUNWIND_FRAMEHEADERCACHE_TRACE0("FrameHeaderCache reset");
+    MostRecentlyUsed = nullptr;
+    Unused = &Entries[0];
+    for (size_t i = 0; i < kCacheEntryCount - 1; i++) {
+      Entries[i].Next = &Entries[i + 1];
+    }
+    Entries[kCacheEntryCount - 1].Next = nullptr;
+  }
+
+  bool cacheNeedsReset(dl_phdr_info *PInfo) {
+    // C libraries increment dl_phdr_info.adds and dl_phdr_info.subs when
+    // loading and unloading shared libraries. If these values change between
+    // iterations of dl_iterate_phdr, then invalidate the cache.
+
+    // These are static to avoid needing an initializer, and unsigned long long
+    // because that is their type within the extended dl_phdr_info.  Initialize
+    // these to something extremely unlikely to be found upon the first call to
+    // dl_iterate_phdr.
+    static unsigned long long LastAdds = ULLONG_MAX;
+    static unsigned long long LastSubs = ULLONG_MAX;
+    if (PInfo->dlpi_adds != LastAdds || PInfo->dlpi_subs != LastSubs) {
+      // Resetting the entire cache is a big hammer, but this path is rare--
+      // usually just on the very first call, when the cache is empty anyway--so
+      // added complexity doesn't buy much.
+      LastAdds = PInfo->dlpi_adds;
+      LastSubs = PInfo->dlpi_subs;
+      resetCache();
+      return true;
+    }
+    return false;
+  }
+
+public:
+  bool find(dl_phdr_info *PInfo, size_t, void *data) {
+    if (cacheNeedsReset(PInfo) || MostRecentlyUsed == nullptr)
+      return false;
+
+    auto *CBData = static_cast<dl_iterate_cb_data *>(data);
+    CacheEntry *Current = MostRecentlyUsed;
+    CacheEntry *Previous = nullptr;
+    while (Current != nullptr) {
+      _LIBUNWIND_FRAMEHEADERCACHE_TRACE(
+          "FrameHeaderCache check %lx in [%lx - %lx)", CBData->targetAddr,
+          Current->LowPC(), Current->HighPC());
+      if (Current->LowPC() <= CBData->targetAddr &&
+          CBData->targetAddr < Current->HighPC()) {
+        _LIBUNWIND_FRAMEHEADERCACHE_TRACE(
+            "FrameHeaderCache hit %lx in [%lx - %lx)", CBData->targetAddr,
+            Current->LowPC(), Current->HighPC());
+        if (Previous) {
+          // If there is no Previous, then Current is already the
+          // MostRecentlyUsed, and no need to move it up.
+          Previous->Next = Current->Next;
+          Current->Next = MostRecentlyUsed;
+          MostRecentlyUsed = Current;
+        }
+        *CBData->sects = Current->Info;
+        return true;
+      }
+      Previous = Current;
+      Current = Current->Next;
+    }
+    _LIBUNWIND_FRAMEHEADERCACHE_TRACE("FrameHeaderCache miss for address %lx",
+                                      CBData->targetAddr);
+    return false;
+  }
+
+  void add(const UnwindInfoSections *UIS) {
+    CacheEntry *Current = nullptr;
+
+    if (Unused != nullptr) {
+      Current = Unused;
+      Unused = Unused->Next;
+    } else {
+      Current = MostRecentlyUsed;
+      CacheEntry *Previous = nullptr;
+      while (Current->Next != nullptr) {
+        Previous = Current;
+        Current = Current->Next;
+      }
+      Previous->Next = nullptr;
+      _LIBUNWIND_FRAMEHEADERCACHE_TRACE("FrameHeaderCache evict [%lx - %lx)",
+                                        Current->LowPC(), Current->HighPC());
+    }
+
+    Current->Info = *UIS;
+    Current->Next = MostRecentlyUsed;
+    MostRecentlyUsed = Current;
+    _LIBUNWIND_FRAMEHEADERCACHE_TRACE("FrameHeaderCache add [%lx - %lx)",
+                                      MostRecentlyUsed->LowPC(),
+                                      MostRecentlyUsed->HighPC());
+  }
+};
+
+#endif // __FRAMEHEADER_CACHE_HPP__

third_party/libunwind/LICENSE.TXT

@@ -0,0 +1,311 @@
+==============================================================================
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+
+---- LLVM Exceptions to the Apache 2.0 License ----
+
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+of this Software are embedded into an Object form of such source code, you
+may redistribute such embedded portions in such Object form without complying
+with the conditions of Sections 4(a), 4(b) and 4(d) of the License.
+
+In addition, if you combine or link compiled forms of this Software with
+software that is licensed under the GPLv2 ("Combined Software") and if a
+court of competent jurisdiction determines that the patent provision (Section
+3), the indemnity provision (Section 9) or other Section of the License
+conflicts with the conditions of the GPLv2, you may retroactively and
+prospectively choose to deem waived or otherwise exclude such Section(s) of
+the License, but only in their entirety and only with respect to the Combined
+Software.
+
+==============================================================================
+Software from third parties included in the LLVM Project:
+==============================================================================
+The LLVM Project contains third party software which is under different license
+terms. All such code will be identified clearly using at least one of two
+mechanisms:
+1) It will be in a separate directory tree with its own `LICENSE.txt` or
+   `LICENSE` file at the top containing the specific license and restrictions
+   which apply to that software, or
+2) It will contain specific license and restriction terms at the top of every
+   file.
+
+==============================================================================
+Legacy LLVM License (https://llvm.org/docs/DeveloperPolicy.html#legacy):
+==============================================================================
+
+The libunwind library is dual licensed under both the University of Illinois
+"BSD-Like" license and the MIT license.  As a user of this code you may choose
+to use it under either license.  As a contributor, you agree to allow your code
+to be used under both.
+
+Full text of the relevant licenses is included below.
+
+==============================================================================
+
+University of Illinois/NCSA
+Open Source License
+
+Copyright (c) 2009-2019 by the contributors listed in CREDITS.TXT
+
+All rights reserved.
+
+Developed by:
+
+    LLVM Team
+
+    University of Illinois at Urbana-Champaign
+
+    http://llvm.org
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
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+
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+      this list of conditions and the following disclaimers in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the names of the LLVM Team, University of Illinois at
+      Urbana-Champaign, nor the names of its contributors may be used to
+      endorse or promote products derived from this Software without specific
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+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+SOFTWARE.
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+==============================================================================
+
+Copyright (c) 2009-2014 by the contributors listed in CREDITS.TXT
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
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+in the Software without restriction, including without limitation the rights
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+all copies or substantial portions of the Software.
+
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+THE SOFTWARE.

third_party/libunwind/README.cosmo

@@ -0,0 +1,13 @@
+DESCRIPTION
+
+  libunwind - LLVM Unwinder
+
+ORIGIN
+
+  Obtained from the LLVM monorepo, release 17.0.6.
+
+  https://github.com/llvm/llvm-project/tree/llvmorg-17.0.6/libunwind
+  commit 6009708b4367171ccdbf4b5905cb6a803753fe18
+  Author: Tobias Hieta <tobias@hieta.se>
+  Date:   Tue, 28 Nov 2023 09:52:28 +0100
+

third_party/libunwind/RWMutex.hpp

@@ -0,0 +1,114 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// Abstract interface to shared reader/writer log, hiding platform and
+// configuration differences.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __RWMUTEX_HPP__
+#define __RWMUTEX_HPP__
+
+#if defined(_WIN32)
+#include <windows.h>
+#elif !defined(_LIBUNWIND_HAS_NO_THREADS)
+#include "libc/isystem/pthread.h"
+#if defined(__ELF__) && defined(_LIBUNWIND_LINK_PTHREAD_LIB)
+#pragma comment(lib, "pthread")
+#endif
+#endif
+
+namespace libunwind {
+
+#if defined(_LIBUNWIND_HAS_NO_THREADS)
+
+class _LIBUNWIND_HIDDEN RWMutex {
+public:
+  bool lock_shared() { return true; }
+  bool unlock_shared() { return true; }
+  bool lock() { return true; }
+  bool unlock() { return true; }
+};
+
+#elif defined(_WIN32)
+
+class _LIBUNWIND_HIDDEN RWMutex {
+public:
+  bool lock_shared() {
+    AcquireSRWLockShared(&_lock);
+    return true;
+  }
+  bool unlock_shared() {
+    ReleaseSRWLockShared(&_lock);
+    return true;
+  }
+  bool lock() {
+    AcquireSRWLockExclusive(&_lock);
+    return true;
+  }
+  bool unlock() {
+    ReleaseSRWLockExclusive(&_lock);
+    return true;
+  }
+
+private:
+  SRWLOCK _lock = SRWLOCK_INIT;
+};
+
+#elif !defined(LIBUNWIND_USE_WEAK_PTHREAD)
+
+class _LIBUNWIND_HIDDEN RWMutex {
+public:
+  bool lock_shared() { return pthread_rwlock_rdlock(&_lock) == 0;  }
+  bool unlock_shared() { return pthread_rwlock_unlock(&_lock) == 0; }
+  bool lock() { return pthread_rwlock_wrlock(&_lock) == 0; }
+  bool unlock() { return pthread_rwlock_unlock(&_lock) == 0; }
+
+private:
+  pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER;
+};
+
+#else
+
+extern "C" int __attribute__((weak))
+pthread_create(pthread_t *thread, const pthread_attr_t *attr,
+               void *(*start_routine)(void *), void *arg);
+extern "C" int __attribute__((weak))
+pthread_rwlock_rdlock(pthread_rwlock_t *lock);
+extern "C" int __attribute__((weak))
+pthread_rwlock_wrlock(pthread_rwlock_t *lock);
+extern "C" int __attribute__((weak))
+pthread_rwlock_unlock(pthread_rwlock_t *lock);
+
+// Calls to the locking functions are gated on pthread_create, and not the
+// functions themselves, because the data structure should only be locked if
+// another thread has been created. This is what similar libraries do.
+
+class _LIBUNWIND_HIDDEN RWMutex {
+public:
+  bool lock_shared() {
+    return !pthread_create || (pthread_rwlock_rdlock(&_lock) == 0);
+  }
+  bool unlock_shared() {
+    return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0);
+  }
+  bool lock() {
+    return !pthread_create || (pthread_rwlock_wrlock(&_lock) == 0);
+  }
+  bool unlock() {
+    return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0);
+  }
+
+private:
+  pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER;
+};
+
+#endif
+
+} // namespace libunwind
+
+#endif // __RWMUTEX_HPP__

third_party/libunwind/Unwind-EHABI.h

@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __UNWIND_EHABI_H__
+#define __UNWIND_EHABI_H__
+
+#include "third_party/libunwind/include/__libunwind_config.h"
+
+#if defined(_LIBUNWIND_ARM_EHABI)
+
+#include "libc/isystem/stdint.h"
+#include "third_party/libunwind/include/unwind.h"
+
+// Unable to unwind in the ARM index table (section 5 EHABI).
+#define UNW_EXIDX_CANTUNWIND 0x1
+
+static inline uint32_t signExtendPrel31(uint32_t data) {
+  return data | ((data & 0x40000000u) << 1);
+}
+
+static inline uint32_t readPrel31(const uint32_t *data) {
+  return (((uint32_t)(uintptr_t)data) + signExtendPrel31(*data));
+}
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr0(
+    _Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
+
+extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr1(
+    _Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
+
+extern _Unwind_Reason_Code __aeabi_unwind_cpp_pr2(
+    _Unwind_State state, _Unwind_Control_Block *ucbp, _Unwind_Context *context);
+
+#if defined(__cplusplus)
+} // extern "C"
+#endif
+
+#endif // defined(_LIBUNWIND_ARM_EHABI)
+
+#endif  // __UNWIND_EHABI_H__

third_party/libunwind/Unwind-sjlj.c

@@ -0,0 +1,528 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Implements setjump-longjump based C++ exceptions
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libunwind/include/unwind.h"
+
+#include "libc/isystem/inttypes.h"
+#include "libc/isystem/stdint.h"
+#include "libc/isystem/stdbool.h"
+#include "libc/isystem/stdlib.h"
+
+#include "third_party/libunwind/config.h"
+
+/// With SJLJ based exceptions, any function that has a catch clause or needs to
+/// do any clean up when an exception propagates through it, needs to call
+/// \c _Unwind_SjLj_Register at the start of the function and
+/// \c _Unwind_SjLj_Unregister at the end.  The register function is called with
+/// the address of a block of memory in the function's stack frame.  The runtime
+/// keeps a linked list (stack) of these blocks - one per thread.  The calling
+/// function also sets the personality and lsda fields of the block.
+
+#if defined(_LIBUNWIND_BUILD_SJLJ_APIS)
+
+struct _Unwind_FunctionContext {
+  // next function in stack of handlers
+  struct _Unwind_FunctionContext *prev;
+
+#if defined(__ve__)
+  // VE requires to store 64 bit pointers in the buffer for SjLj exception.
+  // We expand the size of values defined here.  This size must be matched
+  // to the size returned by TargetMachine::getSjLjDataSize().
+
+  // set by calling function before registering to be the landing pad
+  uint64_t                        resumeLocation;
+
+  // set by personality handler to be parameters passed to landing pad function
+  uint64_t                        resumeParameters[4];
+#else
+  // set by calling function before registering to be the landing pad
+  uint32_t                        resumeLocation;
+
+  // set by personality handler to be parameters passed to landing pad function
+  uint32_t                        resumeParameters[4];
+#endif
+
+  // set by calling function before registering
+  _Unwind_Personality_Fn personality;          // arm offset=24
+  uintptr_t                       lsda;        // arm offset=28
+
+  // variable length array, contains registers to restore
+  // 0 = r7, 1 = pc, 2 = sp
+  void                           *jbuf[];
+};
+
+#if defined(_LIBUNWIND_HAS_NO_THREADS)
+# define _LIBUNWIND_THREAD_LOCAL
+#else
+# if __STDC_VERSION__ >= 201112L
+#  define _LIBUNWIND_THREAD_LOCAL _Thread_local
+# elif defined(_MSC_VER)
+#  define _LIBUNWIND_THREAD_LOCAL __declspec(thread)
+# elif defined(__GNUC__) || defined(__clang__)
+#  define _LIBUNWIND_THREAD_LOCAL __thread
+# else
+#  error Unable to create thread local storage
+# endif
+#endif
+
+
+#if !defined(FOR_DYLD)
+
+#if defined(__APPLE__)
+#include <System/pthread_machdep.h>
+#else
+static _LIBUNWIND_THREAD_LOCAL struct _Unwind_FunctionContext *stack = NULL;
+#endif
+
+static struct _Unwind_FunctionContext *__Unwind_SjLj_GetTopOfFunctionStack() {
+#if defined(__APPLE__)
+  return _pthread_getspecific_direct(__PTK_LIBC_DYLD_Unwind_SjLj_Key);
+#else
+  return stack;
+#endif
+}
+
+static void
+__Unwind_SjLj_SetTopOfFunctionStack(struct _Unwind_FunctionContext *fc) {
+#if defined(__APPLE__)
+  _pthread_setspecific_direct(__PTK_LIBC_DYLD_Unwind_SjLj_Key, fc);
+#else
+  stack = fc;
+#endif
+}
+
+#endif
+
+
+/// Called at start of each function that catches exceptions
+_LIBUNWIND_EXPORT void
+_Unwind_SjLj_Register(struct _Unwind_FunctionContext *fc) {
+  fc->prev = __Unwind_SjLj_GetTopOfFunctionStack();
+  __Unwind_SjLj_SetTopOfFunctionStack(fc);
+}
+
+
+/// Called at end of each function that catches exceptions
+_LIBUNWIND_EXPORT void
+_Unwind_SjLj_Unregister(struct _Unwind_FunctionContext *fc) {
+  __Unwind_SjLj_SetTopOfFunctionStack(fc->prev);
+}
+
+
+static _Unwind_Reason_Code
+unwind_phase1(struct _Unwind_Exception *exception_object) {
+  _Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
+  _LIBUNWIND_TRACE_UNWINDING("unwind_phase1: initial function-context=%p",
+                             (void *)c);
+
+  // walk each frame looking for a place to stop
+  for (bool handlerNotFound = true; handlerNotFound; c = c->prev) {
+
+    // check for no more frames
+    if (c == NULL) {
+      _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): reached "
+                                 "bottom => _URC_END_OF_STACK",
+                                 (void *)exception_object);
+      return _URC_END_OF_STACK;
+    }
+
+    _LIBUNWIND_TRACE_UNWINDING("unwind_phase1: function-context=%p", (void *)c);
+    // if there is a personality routine, ask it if it will want to stop at this
+    // frame
+    if (c->personality != NULL) {
+      _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): calling "
+                                 "personality function %p",
+                                 (void *)exception_object,
+                                 (void *)c->personality);
+      _Unwind_Reason_Code personalityResult = (*c->personality)(
+          1, _UA_SEARCH_PHASE, exception_object->exception_class,
+          exception_object, (struct _Unwind_Context *)c);
+      switch (personalityResult) {
+      case _URC_HANDLER_FOUND:
+        // found a catch clause or locals that need destructing in this frame
+        // stop search and remember function context
+        handlerNotFound = false;
+        exception_object->private_2 = (uintptr_t) c;
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): "
+                                   "_URC_HANDLER_FOUND",
+                                   (void *)exception_object);
+        return _URC_NO_REASON;
+
+      case _URC_CONTINUE_UNWIND:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): "
+                                   "_URC_CONTINUE_UNWIND",
+                                   (void *)exception_object);
+        // continue unwinding
+        break;
+
+      default:
+        // something went wrong
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase1(ex_ojb=%p): _URC_FATAL_PHASE1_ERROR",
+            (void *)exception_object);
+        return _URC_FATAL_PHASE1_ERROR;
+      }
+    }
+  }
+  return _URC_NO_REASON;
+}
+
+
+static _Unwind_Reason_Code
+unwind_phase2(struct _Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p)",
+                             (void *)exception_object);
+
+  // walk each frame until we reach where search phase said to stop
+  _Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
+  while (true) {
+    _LIBUNWIND_TRACE_UNWINDING("unwind_phase2s(ex_ojb=%p): context=%p",
+                               (void *)exception_object, (void *)c);
+
+    // check for no more frames
+    if (c == NULL) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2(ex_ojb=%p): __unw_step() reached "
+          "bottom => _URC_END_OF_STACK",
+          (void *)exception_object);
+      return _URC_END_OF_STACK;
+    }
+
+    // if there is a personality routine, tell it we are unwinding
+    if (c->personality != NULL) {
+      _Unwind_Action action = _UA_CLEANUP_PHASE;
+      if ((uintptr_t) c == exception_object->private_2)
+        action = (_Unwind_Action)(
+            _UA_CLEANUP_PHASE |
+            _UA_HANDLER_FRAME); // tell personality this was the frame it marked
+                                // in phase 1
+      _Unwind_Reason_Code personalityResult =
+          (*c->personality)(1, action, exception_object->exception_class,
+                            exception_object, (struct _Unwind_Context *)c);
+      switch (personalityResult) {
+      case _URC_CONTINUE_UNWIND:
+        // continue unwinding
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase2(ex_ojb=%p): _URC_CONTINUE_UNWIND",
+            (void *)exception_object);
+        if ((uintptr_t) c == exception_object->private_2) {
+          // phase 1 said we would stop at this frame, but we did not...
+          _LIBUNWIND_ABORT("during phase1 personality function said it would "
+                           "stop here, but now if phase2 it did not stop here");
+        }
+        break;
+      case _URC_INSTALL_CONTEXT:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): "
+                                   "_URC_INSTALL_CONTEXT, will resume at "
+                                   "landing pad %p",
+                                   (void *)exception_object, c->jbuf[1]);
+        // personality routine says to transfer control to landing pad
+        // we may get control back if landing pad calls _Unwind_Resume()
+        __Unwind_SjLj_SetTopOfFunctionStack(c);
+        __builtin_longjmp(c->jbuf, 1);
+        // __unw_resume() only returns if there was an error
+        return _URC_FATAL_PHASE2_ERROR;
+      default:
+        // something went wrong
+        _LIBUNWIND_DEBUG_LOG("personality function returned unknown result %d",
+                      personalityResult);
+        return _URC_FATAL_PHASE2_ERROR;
+      }
+    }
+    c = c->prev;
+  }
+
+  // clean up phase did not resume at the frame that the search phase said it
+  // would
+  return _URC_FATAL_PHASE2_ERROR;
+}
+
+
+static _Unwind_Reason_Code
+unwind_phase2_forced(struct _Unwind_Exception *exception_object,
+                     _Unwind_Stop_Fn stop, void *stop_parameter) {
+  // walk each frame until we reach where search phase said to stop
+  _Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
+  while (true) {
+
+    // get next frame (skip over first which is _Unwind_RaiseException)
+    if (c == NULL) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2(ex_ojb=%p): __unw_step() reached "
+          "bottom => _URC_END_OF_STACK",
+          (void *)exception_object);
+      return _URC_END_OF_STACK;
+    }
+
+    // call stop function at each frame
+    _Unwind_Action action =
+        (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);
+    _Unwind_Reason_Code stopResult =
+        (*stop)(1, action, exception_object->exception_class, exception_object,
+                (struct _Unwind_Context *)c, stop_parameter);
+    _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
+                               "stop function returned %d",
+                               (void *)exception_object, stopResult);
+    if (stopResult != _URC_NO_REASON) {
+      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
+                                 "stopped by stop function",
+                                 (void *)exception_object);
+      return _URC_FATAL_PHASE2_ERROR;
+    }
+
+    // if there is a personality routine, tell it we are unwinding
+    if (c->personality != NULL) {
+      _Unwind_Personality_Fn p = (_Unwind_Personality_Fn)c->personality;
+      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
+                                 "calling personality function %p",
+                                 (void *)exception_object, (void *)p);
+      _Unwind_Reason_Code personalityResult =
+          (*p)(1, action, exception_object->exception_class, exception_object,
+               (struct _Unwind_Context *)c);
+      switch (personalityResult) {
+      case _URC_CONTINUE_UNWIND:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p):  "
+                                   "personality returned _URC_CONTINUE_UNWIND",
+                                   (void *)exception_object);
+        // destructors called, continue unwinding
+        break;
+      case _URC_INSTALL_CONTEXT:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
+                                   "personality returned _URC_INSTALL_CONTEXT",
+                                   (void *)exception_object);
+        // we may get control back if landing pad calls _Unwind_Resume()
+        __Unwind_SjLj_SetTopOfFunctionStack(c);
+        __builtin_longjmp(c->jbuf, 1);
+        break;
+      default:
+        // something went wrong
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
+                                   "personality returned %d, "
+                                   "_URC_FATAL_PHASE2_ERROR",
+                                   (void *)exception_object, personalityResult);
+        return _URC_FATAL_PHASE2_ERROR;
+      }
+    }
+    c = c->prev;
+  }
+
+  // call stop function one last time and tell it we've reached the end of the
+  // stack
+  _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): calling stop "
+                             "function with _UA_END_OF_STACK",
+                             (void *)exception_object);
+  _Unwind_Action lastAction =
+      (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK);
+  (*stop)(1, lastAction, exception_object->exception_class, exception_object,
+          (struct _Unwind_Context *)c, stop_parameter);
+
+  // clean up phase did not resume at the frame that the search phase said it
+  // would
+  return _URC_FATAL_PHASE2_ERROR;
+}
+
+
+/// Called by __cxa_throw.  Only returns if there is a fatal error
+_LIBUNWIND_EXPORT _Unwind_Reason_Code
+_Unwind_SjLj_RaiseException(struct _Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("_Unwind_SjLj_RaiseException(ex_obj=%p)",
+                       (void *)exception_object);
+
+  // mark that this is a non-forced unwind, so _Unwind_Resume() can do the right
+  // thing
+  exception_object->private_1 = 0;
+  exception_object->private_2 = 0;
+
+  // phase 1: the search phase
+  _Unwind_Reason_Code phase1 = unwind_phase1(exception_object);
+  if (phase1 != _URC_NO_REASON)
+    return phase1;
+
+  // phase 2: the clean up phase
+  return unwind_phase2(exception_object);
+}
+
+
+
+/// When _Unwind_RaiseException() is in phase2, it hands control
+/// to the personality function at each frame.  The personality
+/// may force a jump to a landing pad in that function, the landing
+/// pad code may then call _Unwind_Resume() to continue with the
+/// unwinding.  Note: the call to _Unwind_Resume() is from compiler
+/// generated user code.  All other _Unwind_* routines are called
+/// by the C++ runtime __cxa_* routines.
+///
+/// Re-throwing an exception is implemented by having the code call
+/// __cxa_rethrow() which in turn calls _Unwind_Resume_or_Rethrow()
+_LIBUNWIND_EXPORT void
+_Unwind_SjLj_Resume(struct _Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("_Unwind_SjLj_Resume(ex_obj=%p)",
+                       (void *)exception_object);
+
+  if (exception_object->private_1 != 0)
+    unwind_phase2_forced(exception_object,
+                         (_Unwind_Stop_Fn) exception_object->private_1,
+                         (void *)exception_object->private_2);
+  else
+    unwind_phase2(exception_object);
+
+  // clients assume _Unwind_Resume() does not return, so all we can do is abort.
+  _LIBUNWIND_ABORT("_Unwind_SjLj_Resume() can't return");
+}
+
+
+///  Called by __cxa_rethrow().
+_LIBUNWIND_EXPORT _Unwind_Reason_Code
+_Unwind_SjLj_Resume_or_Rethrow(struct _Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("__Unwind_SjLj_Resume_or_Rethrow(ex_obj=%p), "
+                       "private_1=%" PRIuPTR,
+                       (void *)exception_object, exception_object->private_1);
+  // If this is non-forced and a stopping place was found, then this is a
+  // re-throw.
+  // Call _Unwind_RaiseException() as if this was a new exception.
+  if (exception_object->private_1 == 0) {
+    return _Unwind_SjLj_RaiseException(exception_object);
+    // should return if there is no catch clause, so that __cxa_rethrow can call
+    // std::terminate()
+  }
+
+  // Call through to _Unwind_Resume() which distinguishes between forced and
+  // regular exceptions.
+  _Unwind_SjLj_Resume(exception_object);
+  _LIBUNWIND_ABORT("__Unwind_SjLj_Resume_or_Rethrow() called "
+                    "_Unwind_SjLj_Resume() which unexpectedly returned");
+}
+
+
+/// Called by personality handler during phase 2 to get LSDA for current frame.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) {
+  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+  _LIBUNWIND_TRACE_API("_Unwind_GetLanguageSpecificData(context=%p) "
+                       "=> 0x%" PRIuPTR,
+                       (void *)context, ufc->lsda);
+  return ufc->lsda;
+}
+
+
+/// Called by personality handler during phase 2 to get register values.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetGR(struct _Unwind_Context *context,
+                                          int index) {
+  _LIBUNWIND_TRACE_API("_Unwind_GetGR(context=%p, reg=%d)", (void *)context,
+                       index);
+  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+  return ufc->resumeParameters[index];
+}
+
+
+/// Called by personality handler during phase 2 to alter register values.
+_LIBUNWIND_EXPORT void _Unwind_SetGR(struct _Unwind_Context *context, int index,
+                                     uintptr_t new_value) {
+  _LIBUNWIND_TRACE_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%" PRIuPTR
+                       ")",
+                       (void *)context, index, new_value);
+  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+  ufc->resumeParameters[index] = new_value;
+}
+
+
+/// Called by personality handler during phase 2 to get instruction pointer.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
+  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+  _LIBUNWIND_TRACE_API("_Unwind_GetIP(context=%p) => 0x%" PRIu32,
+                       (void *)context, ufc->resumeLocation + 1);
+  return ufc->resumeLocation + 1;
+}
+
+
+/// Called by personality handler during phase 2 to get instruction pointer.
+/// ipBefore is a boolean that says if IP is already adjusted to be the call
+/// site address.  Normally IP is the return address.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
+                                              int *ipBefore) {
+  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+  *ipBefore = 0;
+  _LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p, %p) => 0x%" PRIu32,
+                       (void *)context, (void *)ipBefore,
+                       ufc->resumeLocation + 1);
+  return ufc->resumeLocation + 1;
+}
+
+
+/// Called by personality handler during phase 2 to alter instruction pointer.
+_LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *context,
+                                     uintptr_t new_value) {
+  _LIBUNWIND_TRACE_API("_Unwind_SetIP(context=%p, value=0x%" PRIuPTR ")",
+                       (void *)context, new_value);
+  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+  ufc->resumeLocation = new_value - 1;
+}
+
+
+/// Called by personality handler during phase 2 to find the start of the
+/// function.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetRegionStart(struct _Unwind_Context *context) {
+  // Not supported or needed for sjlj based unwinding
+  (void)context;
+  _LIBUNWIND_TRACE_API("_Unwind_GetRegionStart(context=%p)", (void *)context);
+  return 0;
+}
+
+
+/// Called by personality handler during phase 2 if a foreign exception
+/// is caught.
+_LIBUNWIND_EXPORT void
+_Unwind_DeleteException(struct _Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("_Unwind_DeleteException(ex_obj=%p)",
+                       (void *)exception_object);
+  if (exception_object->exception_cleanup != NULL)
+    (*exception_object->exception_cleanup)(_URC_FOREIGN_EXCEPTION_CAUGHT,
+                                           exception_object);
+}
+
+
+
+/// Called by personality handler during phase 2 to get base address for data
+/// relative encodings.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetDataRelBase(struct _Unwind_Context *context) {
+  // Not supported or needed for sjlj based unwinding
+  (void)context;
+  _LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)", (void *)context);
+  _LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
+}
+
+
+/// Called by personality handler during phase 2 to get base address for text
+/// relative encodings.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetTextRelBase(struct _Unwind_Context *context) {
+  // Not supported or needed for sjlj based unwinding
+  (void)context;
+  _LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)", (void *)context);
+  _LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
+}
+
+
+/// Called by personality handler to get "Call Frame Area" for current frame.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
+  _LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p)", (void *)context);
+  if (context != NULL) {
+    _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
+    // Setjmp/longjmp based exceptions don't have a true CFA.
+    // Instead, the SP in the jmpbuf is the closest approximation.
+    return (uintptr_t) ufc->jbuf[2];
+  }
+  return 0;
+}
+
+#endif // defined(_LIBUNWIND_BUILD_SJLJ_APIS)

third_party/libunwind/UnwindLevel1-gcc-ext.c

@@ -0,0 +1,351 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Implements gcc extensions to the C++ ABI Exception Handling Level 1.
+//
+//===----------------------------------------------------------------------===//
+
+#include "libc/isystem/inttypes.h"
+#include "libc/isystem/stdbool.h"
+#include "libc/isystem/stdint.h"
+#include "libc/stdio/stdio.h"
+#include "libc/isystem/stdlib.h"
+#include "libc/isystem/string.h"
+
+#include "third_party/libunwind/config.h"
+#include "third_party/libunwind/libunwind_ext.h"
+#include "third_party/libunwind/include/libunwind.h"
+#include "third_party/libunwind/Unwind-EHABI.h"
+#include "third_party/libunwind/include/unwind.h"
+
+#if defined(_AIX)
+#include <sys/debug.h>
+#endif
+
+#if defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
+
+#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
+#define PRIVATE_1 private_[0]
+#elif defined(_LIBUNWIND_ARM_EHABI)
+#define PRIVATE_1 unwinder_cache.reserved1
+#else
+#define PRIVATE_1 private_1
+#endif
+
+///  Called by __cxa_rethrow().
+_LIBUNWIND_EXPORT _Unwind_Reason_Code
+_Unwind_Resume_or_Rethrow(_Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API(
+      "_Unwind_Resume_or_Rethrow(ex_obj=%p), private_1=%" PRIdPTR,
+      (void *)exception_object, (intptr_t)exception_object->PRIVATE_1);
+
+  // If this is non-forced and a stopping place was found, then this is a
+  // re-throw.
+  // Call _Unwind_RaiseException() as if this was a new exception
+  if (exception_object->PRIVATE_1 == 0) {
+    return _Unwind_RaiseException(exception_object);
+    // Will return if there is no catch clause, so that __cxa_rethrow can call
+    // std::terminate().
+  }
+
+  // Call through to _Unwind_Resume() which distinguishes between forced and
+  // regular exceptions.
+  _Unwind_Resume(exception_object);
+  _LIBUNWIND_ABORT("_Unwind_Resume_or_Rethrow() called _Unwind_RaiseException()"
+                   " which unexpectedly returned");
+}
+
+/// Called by personality handler during phase 2 to get base address for data
+/// relative encodings.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetDataRelBase(struct _Unwind_Context *context) {
+  _LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)", (void *)context);
+#if defined(_AIX)
+  return unw_get_data_rel_base((unw_cursor_t *)context);
+#else
+  (void)context;
+  _LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
+#endif
+}
+
+/// Called by personality handler during phase 2 to get base address for text
+/// relative encodings.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetTextRelBase(struct _Unwind_Context *context) {
+  (void)context;
+  _LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)", (void *)context);
+  _LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
+}
+
+
+/// Scans unwind information to find the function that contains the
+/// specified code address "pc".
+_LIBUNWIND_EXPORT void *_Unwind_FindEnclosingFunction(void *pc) {
+  _LIBUNWIND_TRACE_API("_Unwind_FindEnclosingFunction(pc=%p)", pc);
+#if defined(_AIX)
+  if (pc == NULL)
+    return NULL;
+
+  // Get the start address of the enclosing function from the function's
+  // traceback table.
+  uint32_t *p = (uint32_t *)pc;
+
+  // Keep looking forward until a word of 0 is found. The traceback
+  // table starts at the following word.
+  while (*p)
+    ++p;
+  struct tbtable *TBTable = (struct tbtable *)(p + 1);
+
+  // Get the address of the traceback table extension.
+  p = (uint32_t *)&TBTable->tb_ext;
+
+  // Skip field parminfo if it exists.
+  if (TBTable->tb.fixedparms || TBTable->tb.floatparms)
+    ++p;
+
+  if (TBTable->tb.has_tboff)
+    // *p contains the offset from the function start to traceback table.
+    return (void *)((uintptr_t)TBTable - *p - sizeof(uint32_t));
+  return NULL;
+#else
+  // This is slow, but works.
+  // We create an unwind cursor then alter the IP to be pc
+  unw_cursor_t cursor;
+  unw_context_t uc;
+  unw_proc_info_t info;
+  __unw_getcontext(&uc);
+  __unw_init_local(&cursor, &uc);
+  __unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
+  if (__unw_get_proc_info(&cursor, &info) == UNW_ESUCCESS)
+    return (void *)(intptr_t) info.start_ip;
+  else
+    return NULL;
+#endif
+}
+
+/// Walk every frame and call trace function at each one.  If trace function
+/// returns anything other than _URC_NO_REASON, then walk is terminated.
+_LIBUNWIND_EXPORT _Unwind_Reason_Code
+_Unwind_Backtrace(_Unwind_Trace_Fn callback, void *ref) {
+  unw_cursor_t cursor;
+  unw_context_t uc;
+  __unw_getcontext(&uc);
+  __unw_init_local(&cursor, &uc);
+
+  _LIBUNWIND_TRACE_API("_Unwind_Backtrace(callback=%p)",
+                       (void *)(uintptr_t)callback);
+
+#if defined(_LIBUNWIND_ARM_EHABI)
+  // Create a mock exception object for force unwinding.
+  _Unwind_Exception ex;
+  memset(&ex, '\0', sizeof(ex));
+  strcpy((char *)&ex.exception_class, "CLNGUNW");
+#endif
+
+  // walk each frame
+  while (true) {
+    _Unwind_Reason_Code result;
+
+#if !defined(_LIBUNWIND_ARM_EHABI)
+    // ask libunwind to get next frame (skip over first frame which is
+    // _Unwind_Backtrace())
+    if (__unw_step(&cursor) <= 0) {
+      _LIBUNWIND_TRACE_UNWINDING(" _backtrace: ended because cursor reached "
+                                 "bottom of stack, returning %d",
+                                 _URC_END_OF_STACK);
+      return _URC_END_OF_STACK;
+    }
+#else
+    // Get the information for this frame.
+    unw_proc_info_t frameInfo;
+    if (__unw_get_proc_info(&cursor, &frameInfo) != UNW_ESUCCESS) {
+      return _URC_END_OF_STACK;
+    }
+
+    // Update the pr_cache in the mock exception object.
+    uint32_t *unwindInfo = (uint32_t *)frameInfo.unwind_info;
+    ex.pr_cache.fnstart = frameInfo.start_ip;
+    ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
+    ex.pr_cache.additional= frameInfo.flags;
+
+    struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
+    // Get and call the personality function to unwind the frame.
+    _Unwind_Personality_Fn handler = (_Unwind_Personality_Fn)frameInfo.handler;
+    if (handler == NULL) {
+      return _URC_END_OF_STACK;
+    }
+    if (handler(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, &ex, context) !=
+            _URC_CONTINUE_UNWIND) {
+      return _URC_END_OF_STACK;
+    }
+#endif // defined(_LIBUNWIND_ARM_EHABI)
+
+    // debugging
+    if (_LIBUNWIND_TRACING_UNWINDING) {
+      char functionName[512];
+      unw_proc_info_t frame;
+      unw_word_t offset;
+      __unw_get_proc_name(&cursor, functionName, 512, &offset);
+      __unw_get_proc_info(&cursor, &frame);
+      _LIBUNWIND_TRACE_UNWINDING(
+          " _backtrace: start_ip=0x%" PRIxPTR ", func=%s, lsda=0x%" PRIxPTR ", context=%p",
+          frame.start_ip, functionName, frame.lsda,
+          (void *)&cursor);
+    }
+
+    // call trace function with this frame
+    result = (*callback)((struct _Unwind_Context *)(&cursor), ref);
+    if (result != _URC_NO_REASON) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          " _backtrace: ended because callback returned %d", result);
+      return result;
+    }
+  }
+}
+
+
+/// Find DWARF unwind info for an address 'pc' in some function.
+_LIBUNWIND_EXPORT const void *_Unwind_Find_FDE(const void *pc,
+                                               struct dwarf_eh_bases *bases) {
+  // This is slow, but works.
+  // We create an unwind cursor then alter the IP to be pc
+  unw_cursor_t cursor;
+  unw_context_t uc;
+  unw_proc_info_t info;
+  __unw_getcontext(&uc);
+  __unw_init_local(&cursor, &uc);
+  __unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
+  __unw_get_proc_info(&cursor, &info);
+  bases->tbase = (uintptr_t)info.extra;
+  bases->dbase = 0; // dbase not used on Mac OS X
+  bases->func = (uintptr_t)info.start_ip;
+  _LIBUNWIND_TRACE_API("_Unwind_Find_FDE(pc=%p) => %p", pc,
+                  (void *)(intptr_t) info.unwind_info);
+  return (void *)(intptr_t) info.unwind_info;
+}
+
+/// Returns the CFA (call frame area, or stack pointer at start of function)
+/// for the current context.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  unw_word_t result;
+  __unw_get_reg(cursor, UNW_REG_SP, &result);
+  _LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p) => 0x%" PRIxPTR,
+                       (void *)context, result);
+  return (uintptr_t)result;
+}
+
+
+/// Called by personality handler during phase 2 to get instruction pointer.
+/// ipBefore is a boolean that says if IP is already adjusted to be the call
+/// site address.  Normally IP is the return address.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
+                                              int *ipBefore) {
+  _LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p)", (void *)context);
+  int isSignalFrame = __unw_is_signal_frame((unw_cursor_t *)context);
+  // Negative means some kind of error (probably UNW_ENOINFO), but we have no
+  // good way to report that, and this maintains backward compatibility with the
+  // implementation that hard-coded zero in every case, even signal frames.
+  if (isSignalFrame <= 0)
+    *ipBefore = 0;
+  else
+    *ipBefore = 1;
+  return _Unwind_GetIP(context);
+}
+
+#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+
+/// Called by programs with dynamic code generators that want
+/// to register a dynamically generated FDE.
+/// This function has existed on Mac OS X since 10.4, but
+/// was broken until 10.6.
+_LIBUNWIND_EXPORT void __register_frame(const void *fde) {
+  _LIBUNWIND_TRACE_API("__register_frame(%p)", fde);
+  __unw_add_dynamic_fde((unw_word_t)(uintptr_t)fde);
+}
+
+
+/// Called by programs with dynamic code generators that want
+/// to unregister a dynamically generated FDE.
+/// This function has existed on Mac OS X since 10.4, but
+/// was broken until 10.6.
+_LIBUNWIND_EXPORT void __deregister_frame(const void *fde) {
+  _LIBUNWIND_TRACE_API("__deregister_frame(%p)", fde);
+  __unw_remove_dynamic_fde((unw_word_t)(uintptr_t)fde);
+}
+
+
+// The following register/deregister functions are gcc extensions.
+// They have existed on Mac OS X, but have never worked because Mac OS X
+// before 10.6 used keymgr to track known FDEs, but these functions
+// never got updated to use keymgr.
+// For now, we implement these as do-nothing functions to keep any existing
+// applications working.  We also add the not in 10.6 symbol so that nwe
+// application won't be able to use them.
+
+#if defined(_LIBUNWIND_SUPPORT_FRAME_APIS)
+_LIBUNWIND_EXPORT void __register_frame_info_bases(const void *fde, void *ob,
+                                                   void *tb, void *db) {
+  (void)fde;
+  (void)ob;
+  (void)tb;
+  (void)db;
+ _LIBUNWIND_TRACE_API("__register_frame_info_bases(%p,%p, %p, %p)",
+                            fde, ob, tb, db);
+  // do nothing, this function never worked in Mac OS X
+}
+
+_LIBUNWIND_EXPORT void __register_frame_info(const void *fde, void *ob) {
+  (void)fde;
+  (void)ob;
+  _LIBUNWIND_TRACE_API("__register_frame_info(%p, %p)", fde, ob);
+  // do nothing, this function never worked in Mac OS X
+}
+
+_LIBUNWIND_EXPORT void __register_frame_info_table_bases(const void *fde,
+                                                         void *ob, void *tb,
+                                                         void *db) {
+  (void)fde;
+  (void)ob;
+  (void)tb;
+  (void)db;
+  _LIBUNWIND_TRACE_API("__register_frame_info_table_bases"
+                             "(%p,%p, %p, %p)", fde, ob, tb, db);
+  // do nothing, this function never worked in Mac OS X
+}
+
+_LIBUNWIND_EXPORT void __register_frame_info_table(const void *fde, void *ob) {
+  (void)fde;
+  (void)ob;
+  _LIBUNWIND_TRACE_API("__register_frame_info_table(%p, %p)", fde, ob);
+  // do nothing, this function never worked in Mac OS X
+}
+
+_LIBUNWIND_EXPORT void __register_frame_table(const void *fde) {
+  (void)fde;
+  _LIBUNWIND_TRACE_API("__register_frame_table(%p)", fde);
+  // do nothing, this function never worked in Mac OS X
+}
+
+_LIBUNWIND_EXPORT void *__deregister_frame_info(const void *fde) {
+  (void)fde;
+  _LIBUNWIND_TRACE_API("__deregister_frame_info(%p)", fde);
+  // do nothing, this function never worked in Mac OS X
+  return NULL;
+}
+
+_LIBUNWIND_EXPORT void *__deregister_frame_info_bases(const void *fde) {
+  (void)fde;
+  _LIBUNWIND_TRACE_API("__deregister_frame_info_bases(%p)", fde);
+  // do nothing, this function never worked in Mac OS X
+  return NULL;
+}
+#endif // defined(_LIBUNWIND_SUPPORT_FRAME_APIS)
+
+#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+
+#endif // defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)

third_party/libunwind/UnwindLevel1.c

@@ -0,0 +1,587 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// Implements C++ ABI Exception Handling Level 1 as documented at:
+//      https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
+// using libunwind
+//
+//===----------------------------------------------------------------------===//
+
+// ARM EHABI does not specify _Unwind_{Get,Set}{GR,IP}().  Thus, we are
+// defining inline functions to delegate the function calls to
+// _Unwind_VRS_{Get,Set}().  However, some applications might declare the
+// function protetype directly (instead of including <unwind.h>), thus we need
+// to export these functions from libunwind.so as well.
+#define _LIBUNWIND_UNWIND_LEVEL1_EXTERNAL_LINKAGE 1
+
+#include "libc/isystem/inttypes.h"
+#include "libc/isystem/stdint.h"
+#include "libc/isystem/stdbool.h"
+#include "libc/isystem/stdlib.h"
+#include "libc/stdio/stdio.h"
+#include "libc/isystem/string.h"
+
+#include "third_party/libunwind/cet_unwind.h"
+#include "third_party/libunwind/config.h"
+#include "third_party/libunwind/include/libunwind.h"
+#include "third_party/libunwind/libunwind_ext.h"
+#include "third_party/libunwind/include/unwind.h"
+
+#if !defined(_LIBUNWIND_ARM_EHABI) && !defined(__USING_SJLJ_EXCEPTIONS__)
+
+#ifndef _LIBUNWIND_SUPPORT_SEH_UNWIND
+
+// When CET is enabled, each "call" instruction will push return address to
+// CET shadow stack, each "ret" instruction will pop current CET shadow stack
+// top and compare it with target address which program will return.
+// In exception handing, some stack frames will be skipped before jumping to
+// landing pad and we must adjust CET shadow stack accordingly.
+// _LIBUNWIND_POP_CET_SSP is used to adjust CET shadow stack pointer and we
+// directly jump to __libunwind_Registers_x86/x86_64_jumpto instead of using
+// a regular function call to avoid pushing to CET shadow stack again.
+#if !defined(_LIBUNWIND_USE_CET)
+#define __unw_phase2_resume(cursor, fn)                                        \
+  do {                                                                         \
+    (void)fn;                                                                  \
+    __unw_resume((cursor));                                                    \
+  } while (0)
+#elif defined(_LIBUNWIND_TARGET_I386)
+#define __cet_ss_step_size 4
+#define __unw_phase2_resume(cursor, fn)                                        \
+  do {                                                                         \
+    _LIBUNWIND_POP_CET_SSP((fn));                                              \
+    void *cetRegContext = __libunwind_cet_get_registers((cursor));             \
+    void *cetJumpAddress = __libunwind_cet_get_jump_target();                  \
+    __asm__ volatile("push %%edi\n\t"                                          \
+                     "sub $4, %%esp\n\t"                                       \
+                     "jmp *%%edx\n\t" :: "D"(cetRegContext),                   \
+                     "d"(cetJumpAddress));                                     \
+  } while (0)
+#elif defined(_LIBUNWIND_TARGET_X86_64)
+#define __cet_ss_step_size 8
+#define __unw_phase2_resume(cursor, fn)                                        \
+  do {                                                                         \
+    _LIBUNWIND_POP_CET_SSP((fn));                                              \
+    void *cetRegContext = __libunwind_cet_get_registers((cursor));             \
+    void *cetJumpAddress = __libunwind_cet_get_jump_target();                  \
+    __asm__ volatile("jmpq *%%rdx\n\t" :: "D"(cetRegContext),                  \
+                     "d"(cetJumpAddress));                                     \
+  } while (0)
+#endif
+
+static _Unwind_Reason_Code
+unwind_phase1(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
+  __unw_init_local(cursor, uc);
+
+  // Walk each frame looking for a place to stop.
+  while (true) {
+    // Ask libunwind to get next frame (skip over first which is
+    // _Unwind_RaiseException).
+    int stepResult = __unw_step(cursor);
+    if (stepResult == 0) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase1(ex_obj=%p): __unw_step() reached "
+          "bottom => _URC_END_OF_STACK",
+          (void *)exception_object);
+      return _URC_END_OF_STACK;
+    } else if (stepResult < 0) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase1(ex_obj=%p): __unw_step failed => "
+          "_URC_FATAL_PHASE1_ERROR",
+          (void *)exception_object);
+      return _URC_FATAL_PHASE1_ERROR;
+    }
+
+    // See if frame has code to run (has personality routine).
+    unw_proc_info_t frameInfo;
+    unw_word_t sp;
+    if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase1(ex_obj=%p): __unw_get_proc_info "
+          "failed => _URC_FATAL_PHASE1_ERROR",
+          (void *)exception_object);
+      return _URC_FATAL_PHASE1_ERROR;
+    }
+
+#ifndef NDEBUG
+    // When tracing, print state information.
+    if (_LIBUNWIND_TRACING_UNWINDING) {
+      char functionBuf[512];
+      const char *functionName = functionBuf;
+      unw_word_t offset;
+      if ((__unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
+                               &offset) != UNW_ESUCCESS) ||
+          (frameInfo.start_ip + offset > frameInfo.end_ip))
+        functionName = ".anonymous.";
+      unw_word_t pc;
+      __unw_get_reg(cursor, UNW_REG_IP, &pc);
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase1(ex_obj=%p): pc=0x%" PRIxPTR ", start_ip=0x%" PRIxPTR
+          ", func=%s, lsda=0x%" PRIxPTR ", personality=0x%" PRIxPTR "",
+          (void *)exception_object, pc, frameInfo.start_ip, functionName,
+          frameInfo.lsda, frameInfo.handler);
+    }
+#endif
+
+    // If there is a personality routine, ask it if it will want to stop at
+    // this frame.
+    if (frameInfo.handler != 0) {
+      _Unwind_Personality_Fn p =
+          (_Unwind_Personality_Fn)(uintptr_t)(frameInfo.handler);
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase1(ex_obj=%p): calling personality function %p",
+          (void *)exception_object, (void *)(uintptr_t)p);
+      _Unwind_Reason_Code personalityResult =
+          (*p)(1, _UA_SEARCH_PHASE, exception_object->exception_class,
+               exception_object, (struct _Unwind_Context *)(cursor));
+      switch (personalityResult) {
+      case _URC_HANDLER_FOUND:
+        // found a catch clause or locals that need destructing in this frame
+        // stop search and remember stack pointer at the frame
+        __unw_get_reg(cursor, UNW_REG_SP, &sp);
+        exception_object->private_2 = (uintptr_t)sp;
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase1(ex_obj=%p): _URC_HANDLER_FOUND",
+            (void *)exception_object);
+        return _URC_NO_REASON;
+
+      case _URC_CONTINUE_UNWIND:
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase1(ex_obj=%p): _URC_CONTINUE_UNWIND",
+            (void *)exception_object);
+        // continue unwinding
+        break;
+
+      default:
+        // something went wrong
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase1(ex_obj=%p): _URC_FATAL_PHASE1_ERROR",
+            (void *)exception_object);
+        return _URC_FATAL_PHASE1_ERROR;
+      }
+    }
+  }
+  return _URC_NO_REASON;
+}
+extern int __unw_step_stage2(unw_cursor_t *);
+
+static _Unwind_Reason_Code
+unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
+  __unw_init_local(cursor, uc);
+
+  _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p)",
+                             (void *)exception_object);
+
+  // uc is initialized by __unw_getcontext in the parent frame. The first stack
+  // frame walked is unwind_phase2.
+  unsigned framesWalked = 1;
+#ifdef _LIBUNWIND_USE_CET
+  unsigned long shadowStackTop = _get_ssp();
+#endif
+  // Walk each frame until we reach where search phase said to stop.
+  while (true) {
+
+    // Ask libunwind to get next frame (skip over first which is
+    // _Unwind_RaiseException).
+    int stepResult = __unw_step_stage2(cursor);
+    if (stepResult == 0) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2(ex_obj=%p): __unw_step_stage2() reached "
+          "bottom => _URC_END_OF_STACK",
+          (void *)exception_object);
+      return _URC_END_OF_STACK;
+    } else if (stepResult < 0) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2(ex_obj=%p): __unw_step_stage2 failed => "
+          "_URC_FATAL_PHASE1_ERROR",
+          (void *)exception_object);
+      return _URC_FATAL_PHASE2_ERROR;
+    }
+
+    // Get info about this frame.
+    unw_word_t sp;
+    unw_proc_info_t frameInfo;
+    __unw_get_reg(cursor, UNW_REG_SP, &sp);
+    if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2(ex_obj=%p): __unw_get_proc_info "
+          "failed => _URC_FATAL_PHASE1_ERROR",
+          (void *)exception_object);
+      return _URC_FATAL_PHASE2_ERROR;
+    }
+
+#ifndef NDEBUG
+    // When tracing, print state information.
+    if (_LIBUNWIND_TRACING_UNWINDING) {
+      char functionBuf[512];
+      const char *functionName = functionBuf;
+      unw_word_t offset;
+      if ((__unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
+                               &offset) != UNW_ESUCCESS) ||
+          (frameInfo.start_ip + offset > frameInfo.end_ip))
+        functionName = ".anonymous.";
+      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p): start_ip=0x%" PRIxPTR
+                                 ", func=%s, sp=0x%" PRIxPTR ", lsda=0x%" PRIxPTR
+                                 ", personality=0x%" PRIxPTR,
+                                 (void *)exception_object, frameInfo.start_ip,
+                                 functionName, sp, frameInfo.lsda,
+                                 frameInfo.handler);
+    }
+#endif
+
+// In CET enabled environment, we check return address stored in normal stack
+// against return address stored in CET shadow stack, if the 2 addresses don't
+// match, it means return address in normal stack has been corrupted, we return
+// _URC_FATAL_PHASE2_ERROR.
+#ifdef _LIBUNWIND_USE_CET
+    if (shadowStackTop != 0) {
+      unw_word_t retInNormalStack;
+      __unw_get_reg(cursor, UNW_REG_IP, &retInNormalStack);
+      unsigned long retInShadowStack = *(
+          unsigned long *)(shadowStackTop + __cet_ss_step_size * framesWalked);
+      if (retInNormalStack != retInShadowStack)
+        return _URC_FATAL_PHASE2_ERROR;
+    }
+#endif
+    ++framesWalked;
+    // If there is a personality routine, tell it we are unwinding.
+    if (frameInfo.handler != 0) {
+      _Unwind_Personality_Fn p =
+          (_Unwind_Personality_Fn)(uintptr_t)(frameInfo.handler);
+      _Unwind_Action action = _UA_CLEANUP_PHASE;
+      if (sp == exception_object->private_2) {
+        // Tell personality this was the frame it marked in phase 1.
+        action = (_Unwind_Action)(_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME);
+      }
+       _Unwind_Reason_Code personalityResult =
+          (*p)(1, action, exception_object->exception_class, exception_object,
+               (struct _Unwind_Context *)(cursor));
+      switch (personalityResult) {
+      case _URC_CONTINUE_UNWIND:
+        // Continue unwinding
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase2(ex_obj=%p): _URC_CONTINUE_UNWIND",
+            (void *)exception_object);
+        if (sp == exception_object->private_2) {
+          // Phase 1 said we would stop at this frame, but we did not...
+          _LIBUNWIND_ABORT("during phase1 personality function said it would "
+                           "stop here, but now in phase2 it did not stop here");
+        }
+        break;
+      case _URC_INSTALL_CONTEXT:
+        _LIBUNWIND_TRACE_UNWINDING(
+            "unwind_phase2(ex_obj=%p): _URC_INSTALL_CONTEXT",
+            (void *)exception_object);
+        // Personality routine says to transfer control to landing pad.
+        // We may get control back if landing pad calls _Unwind_Resume().
+        if (_LIBUNWIND_TRACING_UNWINDING) {
+          unw_word_t pc;
+          __unw_get_reg(cursor, UNW_REG_IP, &pc);
+          __unw_get_reg(cursor, UNW_REG_SP, &sp);
+          _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p): re-entering "
+                                     "user code with ip=0x%" PRIxPTR
+                                     ", sp=0x%" PRIxPTR,
+                                     (void *)exception_object, pc, sp);
+        }
+
+        __unw_phase2_resume(cursor, framesWalked);
+        // __unw_phase2_resume() only returns if there was an error.
+        return _URC_FATAL_PHASE2_ERROR;
+      default:
+        // Personality routine returned an unknown result code.
+        _LIBUNWIND_DEBUG_LOG("personality function returned unknown result %d",
+                             personalityResult);
+        return _URC_FATAL_PHASE2_ERROR;
+      }
+    }
+  }
+
+  // Clean up phase did not resume at the frame that the search phase
+  // said it would...
+  return _URC_FATAL_PHASE2_ERROR;
+}
+
+static _Unwind_Reason_Code
+unwind_phase2_forced(unw_context_t *uc, unw_cursor_t *cursor,
+                     _Unwind_Exception *exception_object,
+                     _Unwind_Stop_Fn stop, void *stop_parameter) {
+  __unw_init_local(cursor, uc);
+
+  // uc is initialized by __unw_getcontext in the parent frame. The first stack
+  // frame walked is unwind_phase2_forced.
+  unsigned framesWalked = 1;
+  // Walk each frame until we reach where search phase said to stop
+  while (__unw_step_stage2(cursor) > 0) {
+
+    // Update info about this frame.
+    unw_proc_info_t frameInfo;
+    if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2_forced(ex_obj=%p): __unw_get_proc_info "
+          "failed => _URC_END_OF_STACK",
+          (void *)exception_object);
+      return _URC_FATAL_PHASE2_ERROR;
+    }
+
+#ifndef NDEBUG
+    // When tracing, print state information.
+    if (_LIBUNWIND_TRACING_UNWINDING) {
+      char functionBuf[512];
+      const char *functionName = functionBuf;
+      unw_word_t offset;
+      if ((__unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
+                               &offset) != UNW_ESUCCESS) ||
+          (frameInfo.start_ip + offset > frameInfo.end_ip))
+        functionName = ".anonymous.";
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2_forced(ex_obj=%p): start_ip=0x%" PRIxPTR
+          ", func=%s, lsda=0x%" PRIxPTR ", personality=0x%" PRIxPTR,
+          (void *)exception_object, frameInfo.start_ip, functionName,
+          frameInfo.lsda, frameInfo.handler);
+    }
+#endif
+
+    // Call stop function at each frame.
+    _Unwind_Action action =
+        (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);
+    _Unwind_Reason_Code stopResult =
+        (*stop)(1, action, exception_object->exception_class, exception_object,
+                (struct _Unwind_Context *)(cursor), stop_parameter);
+    _LIBUNWIND_TRACE_UNWINDING(
+        "unwind_phase2_forced(ex_obj=%p): stop function returned %d",
+        (void *)exception_object, stopResult);
+    if (stopResult != _URC_NO_REASON) {
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2_forced(ex_obj=%p): stopped by stop function",
+          (void *)exception_object);
+      return _URC_FATAL_PHASE2_ERROR;
+    }
+
+    ++framesWalked;
+    // If there is a personality routine, tell it we are unwinding.
+    if (frameInfo.handler != 0) {
+      _Unwind_Personality_Fn p =
+          (_Unwind_Personality_Fn)(intptr_t)(frameInfo.handler);
+      _LIBUNWIND_TRACE_UNWINDING(
+          "unwind_phase2_forced(ex_obj=%p): calling personality function %p",
+          (void *)exception_object, (void *)(uintptr_t)p);
+      _Unwind_Reason_Code personalityResult =
+          (*p)(1, action, exception_object->exception_class, exception_object,
+               (struct _Unwind_Context *)(cursor));
+      switch (personalityResult) {
+      case _URC_CONTINUE_UNWIND:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): "
+                                   "personality returned "
+                                   "_URC_CONTINUE_UNWIND",
+                                   (void *)exception_object);
+        // Destructors called, continue unwinding
+        break;
+      case _URC_INSTALL_CONTEXT:
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): "
+                                   "personality returned "
+                                   "_URC_INSTALL_CONTEXT",
+                                   (void *)exception_object);
+        // We may get control back if landing pad calls _Unwind_Resume().
+        __unw_phase2_resume(cursor, framesWalked);
+        break;
+      default:
+        // Personality routine returned an unknown result code.
+        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): "
+                                   "personality returned %d, "
+                                   "_URC_FATAL_PHASE2_ERROR",
+                                   (void *)exception_object, personalityResult);
+        return _URC_FATAL_PHASE2_ERROR;
+      }
+    }
+  }
+
+  // Call stop function one last time and tell it we've reached the end
+  // of the stack.
+  _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): calling stop "
+                             "function with _UA_END_OF_STACK",
+                             (void *)exception_object);
+  _Unwind_Action lastAction =
+      (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK);
+  (*stop)(1, lastAction, exception_object->exception_class, exception_object,
+          (struct _Unwind_Context *)(cursor), stop_parameter);
+
+  // Clean up phase did not resume at the frame that the search phase said it
+  // would.
+  return _URC_FATAL_PHASE2_ERROR;
+}
+
+
+/// Called by __cxa_throw.  Only returns if there is a fatal error.
+_LIBUNWIND_EXPORT _Unwind_Reason_Code
+_Unwind_RaiseException(_Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("_Unwind_RaiseException(ex_obj=%p)",
+                       (void *)exception_object);
+  unw_context_t uc;
+  unw_cursor_t cursor;
+  __unw_getcontext(&uc);
+
+  // Mark that this is a non-forced unwind, so _Unwind_Resume()
+  // can do the right thing.
+  exception_object->private_1 = 0;
+  exception_object->private_2 = 0;
+
+  // phase 1: the search phase
+  _Unwind_Reason_Code phase1 = unwind_phase1(&uc, &cursor, exception_object);
+  if (phase1 != _URC_NO_REASON)
+    return phase1;
+
+  // phase 2: the clean up phase
+  return unwind_phase2(&uc, &cursor, exception_object);
+}
+
+
+
+/// When _Unwind_RaiseException() is in phase2, it hands control
+/// to the personality function at each frame.  The personality
+/// may force a jump to a landing pad in that function, the landing
+/// pad code may then call _Unwind_Resume() to continue with the
+/// unwinding.  Note: the call to _Unwind_Resume() is from compiler
+/// generated user code.  All other _Unwind_* routines are called
+/// by the C++ runtime __cxa_* routines.
+///
+/// Note: re-throwing an exception (as opposed to continuing the unwind)
+/// is implemented by having the code call __cxa_rethrow() which
+/// in turn calls _Unwind_Resume_or_Rethrow().
+_LIBUNWIND_EXPORT void
+_Unwind_Resume(_Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("_Unwind_Resume(ex_obj=%p)", (void *)exception_object);
+  unw_context_t uc;
+  unw_cursor_t cursor;
+  __unw_getcontext(&uc);
+
+  if (exception_object->private_1 != 0)
+    unwind_phase2_forced(&uc, &cursor, exception_object,
+                         (_Unwind_Stop_Fn) exception_object->private_1,
+                         (void *)exception_object->private_2);
+  else
+    unwind_phase2(&uc, &cursor, exception_object);
+
+  // Clients assume _Unwind_Resume() does not return, so all we can do is abort.
+  _LIBUNWIND_ABORT("_Unwind_Resume() can't return");
+}
+
+
+
+/// Not used by C++.
+/// Unwinds stack, calling "stop" function at each frame.
+/// Could be used to implement longjmp().
+_LIBUNWIND_EXPORT _Unwind_Reason_Code
+_Unwind_ForcedUnwind(_Unwind_Exception *exception_object,
+                     _Unwind_Stop_Fn stop, void *stop_parameter) {
+  _LIBUNWIND_TRACE_API("_Unwind_ForcedUnwind(ex_obj=%p, stop=%p)",
+                       (void *)exception_object, (void *)(uintptr_t)stop);
+  unw_context_t uc;
+  unw_cursor_t cursor;
+  __unw_getcontext(&uc);
+
+  // Mark that this is a forced unwind, so _Unwind_Resume() can do
+  // the right thing.
+  exception_object->private_1 = (uintptr_t) stop;
+  exception_object->private_2 = (uintptr_t) stop_parameter;
+
+  // do it
+  return unwind_phase2_forced(&uc, &cursor, exception_object, stop, stop_parameter);
+}
+
+
+/// Called by personality handler during phase 2 to get LSDA for current frame.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) {
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  unw_proc_info_t frameInfo;
+  uintptr_t result = 0;
+  if (__unw_get_proc_info(cursor, &frameInfo) == UNW_ESUCCESS)
+    result = (uintptr_t)frameInfo.lsda;
+  _LIBUNWIND_TRACE_API(
+      "_Unwind_GetLanguageSpecificData(context=%p) => 0x%" PRIxPTR,
+      (void *)context, result);
+#if !defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
+  if (result != 0) {
+    if (*((uint8_t *)result) != 0xFF)
+      _LIBUNWIND_DEBUG_LOG("lsda at 0x%" PRIxPTR " does not start with 0xFF",
+                           result);
+  }
+#endif
+  return result;
+}
+
+
+/// Called by personality handler during phase 2 to find the start of the
+/// function.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetRegionStart(struct _Unwind_Context *context) {
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  unw_proc_info_t frameInfo;
+  uintptr_t result = 0;
+  if (__unw_get_proc_info(cursor, &frameInfo) == UNW_ESUCCESS)
+    result = (uintptr_t)frameInfo.start_ip;
+  _LIBUNWIND_TRACE_API("_Unwind_GetRegionStart(context=%p) => 0x%" PRIxPTR,
+                       (void *)context, result);
+  return result;
+}
+
+#endif // !_LIBUNWIND_SUPPORT_SEH_UNWIND
+
+/// Called by personality handler during phase 2 if a foreign exception
+// is caught.
+_LIBUNWIND_EXPORT void
+_Unwind_DeleteException(_Unwind_Exception *exception_object) {
+  _LIBUNWIND_TRACE_API("_Unwind_DeleteException(ex_obj=%p)",
+                       (void *)exception_object);
+  if (exception_object->exception_cleanup != NULL)
+    (*exception_object->exception_cleanup)(_URC_FOREIGN_EXCEPTION_CAUGHT,
+                                           exception_object);
+}
+
+/// Called by personality handler during phase 2 to get register values.
+_LIBUNWIND_EXPORT uintptr_t
+_Unwind_GetGR(struct _Unwind_Context *context, int index) {
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  unw_word_t result;
+  __unw_get_reg(cursor, index, &result);
+  _LIBUNWIND_TRACE_API("_Unwind_GetGR(context=%p, reg=%d) => 0x%" PRIxPTR,
+                       (void *)context, index, result);
+  return (uintptr_t)result;
+}
+
+/// Called by personality handler during phase 2 to alter register values.
+_LIBUNWIND_EXPORT void _Unwind_SetGR(struct _Unwind_Context *context, int index,
+                                     uintptr_t value) {
+  _LIBUNWIND_TRACE_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%0" PRIxPTR
+                       ")",
+                       (void *)context, index, value);
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  __unw_set_reg(cursor, index, value);
+}
+
+/// Called by personality handler during phase 2 to get instruction pointer.
+_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  unw_word_t result;
+  __unw_get_reg(cursor, UNW_REG_IP, &result);
+  _LIBUNWIND_TRACE_API("_Unwind_GetIP(context=%p) => 0x%" PRIxPTR,
+                       (void *)context, result);
+  return (uintptr_t)result;
+}
+
+/// Called by personality handler during phase 2 to alter instruction pointer,
+/// such as setting where the landing pad is, so _Unwind_Resume() will
+/// start executing in the landing pad.
+_LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *context,
+                                     uintptr_t value) {
+  _LIBUNWIND_TRACE_API("_Unwind_SetIP(context=%p, value=0x%0" PRIxPTR ")",
+                       (void *)context, value);
+  unw_cursor_t *cursor = (unw_cursor_t *)context;
+  __unw_set_reg(cursor, UNW_REG_IP, value);
+}
+
+#endif // !defined(_LIBUNWIND_ARM_EHABI) && !defined(__USING_SJLJ_EXCEPTIONS__)

third_party/libunwind/cet_unwind.h

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LIBUNWIND_CET_UNWIND_H
+#define LIBUNWIND_CET_UNWIND_H
+
+#include "third_party/libunwind/include/libunwind.h"
+
+// Currently, CET is implemented on Linux x86 platforms.
+#if defined(_LIBUNWIND_TARGET_LINUX) && defined(__CET__) && defined(__SHSTK__)
+#define _LIBUNWIND_USE_CET 1
+#endif
+
+#if defined(_LIBUNWIND_USE_CET)
+#include <cet.h>
+#include <immintrin.h>
+
+#define _LIBUNWIND_POP_CET_SSP(x)                                              \
+  do {                                                                         \
+    unsigned long ssp = _get_ssp();                                            \
+    if (ssp != 0) {                                                            \
+      unsigned int tmp = (x);                                                  \
+      while (tmp > 255) {                                                      \
+        _inc_ssp(255);                                                         \
+        tmp -= 255;                                                            \
+      }                                                                        \
+      _inc_ssp(tmp);                                                           \
+    }                                                                          \
+  } while (0)
+#endif
+
+extern void *__libunwind_cet_get_registers(unw_cursor_t *);
+extern void *__libunwind_cet_get_jump_target(void);
+
+#endif

third_party/libunwind/config.h

@@ -0,0 +1,245 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Defines macros used within libunwind project.
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifndef LIBUNWIND_CONFIG_H
+#define LIBUNWIND_CONFIG_H
+
+#include "libc/isystem/assert.h"
+#include "libc/stdio/stdio.h"
+#include "libc/isystem/stdint.h"
+#include "libc/isystem/stdlib.h"
+
+#include "third_party/libunwind/include/__libunwind_config.h"
+
+// Platform specific configuration defines.
+#ifdef __APPLE__
+  #if defined(FOR_DYLD)
+    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
+  #else
+    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+  #endif
+#elif defined(_WIN32)
+  #ifdef __SEH__
+    #define _LIBUNWIND_SUPPORT_SEH_UNWIND 1
+  #else
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+  #endif
+#elif defined(_LIBUNWIND_IS_BAREMETAL)
+  #if !defined(_LIBUNWIND_ARM_EHABI)
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+    #define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
+  #endif
+#elif defined(__BIONIC__) && defined(_LIBUNWIND_ARM_EHABI)
+  // For ARM EHABI, Bionic didn't implement dl_iterate_phdr until API 21. After
+  // API 21, dl_iterate_phdr exists, but dl_unwind_find_exidx is much faster.
+  #define _LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX 1
+#elif defined(_AIX)
+// The traceback table at the end of each function is used for unwinding.
+#define _LIBUNWIND_SUPPORT_TBTAB_UNWIND 1
+#else
+  // Assume an ELF system with a dl_iterate_phdr function.
+  #define _LIBUNWIND_USE_DL_ITERATE_PHDR 1
+  #if !defined(_LIBUNWIND_ARM_EHABI)
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+    #define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
+  #endif
+#endif
+
+#if defined(_LIBUNWIND_HIDE_SYMBOLS)
+  // The CMake file passes -fvisibility=hidden to control ELF/Mach-O visibility.
+  #define _LIBUNWIND_EXPORT
+  #define _LIBUNWIND_HIDDEN
+#else
+  #if !defined(__ELF__) && !defined(__MACH__) && !defined(_AIX)
+    #define _LIBUNWIND_EXPORT __declspec(dllexport)
+    #define _LIBUNWIND_HIDDEN
+  #else
+    #define _LIBUNWIND_EXPORT __attribute__((visibility("default")))
+    #define _LIBUNWIND_HIDDEN __attribute__((visibility("hidden")))
+  #endif
+#endif
+
+#define STR(a) #a
+#define XSTR(a) STR(a)
+#define SYMBOL_NAME(name) XSTR(__USER_LABEL_PREFIX__) #name
+
+#if defined(__APPLE__)
+#if defined(_LIBUNWIND_HIDE_SYMBOLS)
+#define _LIBUNWIND_ALIAS_VISIBILITY(name) __asm__(".private_extern " name);
+#else
+#define _LIBUNWIND_ALIAS_VISIBILITY(name)
+#endif
+#define _LIBUNWIND_WEAK_ALIAS(name, aliasname)                                 \
+  __asm__(".globl " SYMBOL_NAME(aliasname));                                   \
+  __asm__(SYMBOL_NAME(aliasname) " = " SYMBOL_NAME(name));                     \
+  _LIBUNWIND_ALIAS_VISIBILITY(SYMBOL_NAME(aliasname))
+#elif defined(__ELF__) || defined(_AIX)
+#define _LIBUNWIND_WEAK_ALIAS(name, aliasname)                                 \
+  extern "C" _LIBUNWIND_EXPORT __typeof(name) aliasname                        \
+      __attribute__((weak, alias(#name)));
+#elif defined(_WIN32)
+#if defined(__MINGW32__)
+#define _LIBUNWIND_WEAK_ALIAS(name, aliasname)                                 \
+  extern "C" _LIBUNWIND_EXPORT __typeof(name) aliasname                        \
+      __attribute__((alias(#name)));
+#else
+#define _LIBUNWIND_WEAK_ALIAS(name, aliasname)                                 \
+  __pragma(comment(linker, "/alternatename:" SYMBOL_NAME(aliasname) "="        \
+                                             SYMBOL_NAME(name)))               \
+  extern "C" _LIBUNWIND_EXPORT __typeof(name) aliasname;
+#endif
+#else
+#error Unsupported target
+#endif
+
+// Apple/armv7k defaults to DWARF/Compact unwinding, but its libunwind also
+// needs to include the SJLJ APIs.
+#if (defined(__APPLE__) && defined(__arm__)) || defined(__USING_SJLJ_EXCEPTIONS__)
+#define _LIBUNWIND_BUILD_SJLJ_APIS
+#endif
+
+#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__)
+#define _LIBUNWIND_SUPPORT_FRAME_APIS
+#endif
+
+#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__) ||        \
+    (!defined(__APPLE__) && defined(__arm__)) || defined(__aarch64__) ||       \
+    defined(__mips__) || defined(__riscv) || defined(__hexagon__) ||           \
+    defined(__sparc__) || defined(__s390x__) || defined(__loongarch__)
+#if !defined(_LIBUNWIND_BUILD_SJLJ_APIS)
+#define _LIBUNWIND_BUILD_ZERO_COST_APIS
+#endif
+#endif
+
+#ifndef _LIBUNWIND_REMEMBER_HEAP_ALLOC
+#if defined(_LIBUNWIND_REMEMBER_STACK_ALLOC) || defined(__APPLE__) ||          \
+    defined(__linux__) || defined(__ANDROID__) || defined(__MINGW32__) ||      \
+    defined(_LIBUNWIND_IS_BAREMETAL)
+#define _LIBUNWIND_REMEMBER_ALLOC(_size) alloca(_size)
+#define _LIBUNWIND_REMEMBER_FREE(_ptr)                                         \
+  do {                                                                         \
+  } while (0)
+#elif defined(_WIN32)
+#define _LIBUNWIND_REMEMBER_ALLOC(_size) _malloca(_size)
+#define _LIBUNWIND_REMEMBER_FREE(_ptr) _freea(_ptr)
+#define _LIBUNWIND_REMEMBER_CLEANUP_NEEDED
+#else
+#define _LIBUNWIND_REMEMBER_ALLOC(_size) malloc(_size)
+#define _LIBUNWIND_REMEMBER_FREE(_ptr) free(_ptr)
+#define _LIBUNWIND_REMEMBER_CLEANUP_NEEDED
+#endif
+#else /* _LIBUNWIND_REMEMBER_HEAP_ALLOC */
+#define _LIBUNWIND_REMEMBER_ALLOC(_size) malloc(_size)
+#define _LIBUNWIND_REMEMBER_FREE(_ptr) free(_ptr)
+#define _LIBUNWIND_REMEMBER_CLEANUP_NEEDED
+#endif
+
+#if defined(NDEBUG) && defined(_LIBUNWIND_IS_BAREMETAL)
+#define _LIBUNWIND_ABORT(msg)                                                  \
+  do {                                                                         \
+    abort();                                                                   \
+  } while (0)
+#else
+#define _LIBUNWIND_ABORT(msg)                                                  \
+  do {                                                                         \
+    fprintf(stderr, "libunwind: %s - %s\n", __func__, msg);                    \
+    fflush(stderr);                                                            \
+    abort();                                                                   \
+  } while (0)
+#endif
+
+#if defined(NDEBUG) && defined(_LIBUNWIND_IS_BAREMETAL)
+#define _LIBUNWIND_LOG0(msg)
+#define _LIBUNWIND_LOG(msg, ...)
+#else
+#define _LIBUNWIND_LOG0(msg) do {                                              \
+    fprintf(stderr, "libunwind: " msg "\n");                                   \
+    fflush(stderr);                                                            \
+  } while (0)
+#define _LIBUNWIND_LOG(msg, ...) do {                                          \
+    fprintf(stderr, "libunwind: " msg "\n", __VA_ARGS__);                      \
+    fflush(stderr);                                                            \
+  } while (0)
+#endif
+
+#if defined(NDEBUG)
+  #define _LIBUNWIND_LOG_IF_FALSE(x) x
+#else
+  #define _LIBUNWIND_LOG_IF_FALSE(x)                                           \
+    do {                                                                       \
+      bool _ret = x;                                                           \
+      if (!_ret)                                                               \
+        _LIBUNWIND_LOG("" #x " failed in %s", __FUNCTION__);                   \
+    } while (0)
+#endif
+
+// Macros that define away in non-Debug builds
+#ifdef NDEBUG
+  #define _LIBUNWIND_DEBUG_LOG(msg, ...)
+  #define _LIBUNWIND_TRACE_API(msg, ...)
+  #define _LIBUNWIND_TRACING_UNWINDING (0)
+  #define _LIBUNWIND_TRACING_DWARF (0)
+  #define _LIBUNWIND_TRACE_UNWINDING(msg, ...)
+  #define _LIBUNWIND_TRACE_DWARF(...)
+#else
+  #ifdef __cplusplus
+    extern "C" {
+  #endif
+    extern  bool logAPIs(void);
+    extern  bool logUnwinding(void);
+    extern  bool logDWARF(void);
+  #ifdef __cplusplus
+    }
+  #endif
+  #define _LIBUNWIND_DEBUG_LOG(msg, ...)  _LIBUNWIND_LOG(msg, __VA_ARGS__)
+  #define _LIBUNWIND_TRACE_API(msg, ...)                                       \
+    do {                                                                       \
+      if (logAPIs())                                                           \
+        _LIBUNWIND_LOG(msg, __VA_ARGS__);                                      \
+    } while (0)
+  #define _LIBUNWIND_TRACING_UNWINDING logUnwinding()
+  #define _LIBUNWIND_TRACING_DWARF logDWARF()
+  #define _LIBUNWIND_TRACE_UNWINDING(msg, ...)                                 \
+    do {                                                                       \
+      if (logUnwinding())                                                      \
+        _LIBUNWIND_LOG(msg, __VA_ARGS__);                                      \
+    } while (0)
+  #define _LIBUNWIND_TRACE_DWARF(...)                                          \
+    do {                                                                       \
+      if (logDWARF())                                                          \
+        fprintf(stderr, __VA_ARGS__);                                          \
+    } while (0)
+#endif
+
+#ifdef __cplusplus
+// Used to fit UnwindCursor and Registers_xxx types against unw_context_t /
+// unw_cursor_t sized memory blocks.
+#if defined(_LIBUNWIND_IS_NATIVE_ONLY)
+# define COMP_OP ==
+#else
+# define COMP_OP <=
+#endif
+template <typename _Type, typename _Mem>
+struct check_fit {
+  template <typename T>
+  struct blk_count {
+    static const size_t count =
+      (sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t);
+  };
+  static const bool does_fit =
+    (blk_count<_Type>::count COMP_OP blk_count<_Mem>::count);
+};
+#undef COMP_OP
+#endif // __cplusplus
+
+#endif // LIBUNWIND_CONFIG_H

third_party/libunwind/dwarf2.h

@@ -0,0 +1,239 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+
+/*
+   These constants were taken from version 3 of the DWARF standard,
+   which is Copyright (c) 2005 Free Standards Group, and
+   Copyright (c) 1992, 1993 UNIX International, Inc.
+*/
+
+#ifndef __DWARF2__
+#define __DWARF2__
+
+// DWARF unwind instructions
+enum {
+  DW_CFA_nop                 = 0x0,
+  DW_CFA_set_loc             = 0x1,
+  DW_CFA_advance_loc1        = 0x2,
+  DW_CFA_advance_loc2        = 0x3,
+  DW_CFA_advance_loc4        = 0x4,
+  DW_CFA_offset_extended     = 0x5,
+  DW_CFA_restore_extended    = 0x6,
+  DW_CFA_undefined           = 0x7,
+  DW_CFA_same_value          = 0x8,
+  DW_CFA_register            = 0x9,
+  DW_CFA_remember_state      = 0xA,
+  DW_CFA_restore_state       = 0xB,
+  DW_CFA_def_cfa             = 0xC,
+  DW_CFA_def_cfa_register    = 0xD,
+  DW_CFA_def_cfa_offset      = 0xE,
+  DW_CFA_def_cfa_expression  = 0xF,
+  DW_CFA_expression         = 0x10,
+  DW_CFA_offset_extended_sf = 0x11,
+  DW_CFA_def_cfa_sf         = 0x12,
+  DW_CFA_def_cfa_offset_sf  = 0x13,
+  DW_CFA_val_offset         = 0x14,
+  DW_CFA_val_offset_sf      = 0x15,
+  DW_CFA_val_expression     = 0x16,
+  DW_CFA_advance_loc        = 0x40, // high 2 bits are 0x1, lower 6 bits are delta
+  DW_CFA_offset             = 0x80, // high 2 bits are 0x2, lower 6 bits are register
+  DW_CFA_restore            = 0xC0, // high 2 bits are 0x3, lower 6 bits are register
+
+  // GNU extensions
+  DW_CFA_GNU_window_save              = 0x2D,
+  DW_CFA_GNU_args_size                = 0x2E,
+  DW_CFA_GNU_negative_offset_extended = 0x2F,
+
+  // AARCH64 extensions
+  DW_CFA_AARCH64_negate_ra_state      = 0x2D
+};
+
+
+// FSF exception handling Pointer-Encoding constants
+// Used in CFI augmentation by GCC
+enum {
+  DW_EH_PE_ptr       = 0x00,
+  DW_EH_PE_uleb128   = 0x01,
+  DW_EH_PE_udata2    = 0x02,
+  DW_EH_PE_udata4    = 0x03,
+  DW_EH_PE_udata8    = 0x04,
+  DW_EH_PE_signed    = 0x08,
+  DW_EH_PE_sleb128   = 0x09,
+  DW_EH_PE_sdata2    = 0x0A,
+  DW_EH_PE_sdata4    = 0x0B,
+  DW_EH_PE_sdata8    = 0x0C,
+  DW_EH_PE_absptr    = 0x00,
+  DW_EH_PE_pcrel     = 0x10,
+  DW_EH_PE_textrel   = 0x20,
+  DW_EH_PE_datarel   = 0x30,
+  DW_EH_PE_funcrel   = 0x40,
+  DW_EH_PE_aligned   = 0x50,
+  DW_EH_PE_indirect  = 0x80,
+  DW_EH_PE_omit      = 0xFF
+};
+
+
+// DWARF expressions
+enum {
+  DW_OP_addr               = 0x03, // constant address (size target specific)
+  DW_OP_deref              = 0x06,
+  DW_OP_const1u            = 0x08, // 1-byte constant
+  DW_OP_const1s            = 0x09, // 1-byte constant
+  DW_OP_const2u            = 0x0A, // 2-byte constant
+  DW_OP_const2s            = 0x0B, // 2-byte constant
+  DW_OP_const4u            = 0x0C, // 4-byte constant
+  DW_OP_const4s            = 0x0D, // 4-byte constant
+  DW_OP_const8u            = 0x0E, // 8-byte constant
+  DW_OP_const8s            = 0x0F, // 8-byte constant
+  DW_OP_constu             = 0x10, // ULEB128 constant
+  DW_OP_consts             = 0x11, // SLEB128 constant
+  DW_OP_dup                = 0x12,
+  DW_OP_drop               = 0x13,
+  DW_OP_over               = 0x14,
+  DW_OP_pick               = 0x15, // 1-byte stack index
+  DW_OP_swap               = 0x16,
+  DW_OP_rot                = 0x17,
+  DW_OP_xderef             = 0x18,
+  DW_OP_abs                = 0x19,
+  DW_OP_and                = 0x1A,
+  DW_OP_div                = 0x1B,
+  DW_OP_minus              = 0x1C,
+  DW_OP_mod                = 0x1D,
+  DW_OP_mul                = 0x1E,
+  DW_OP_neg                = 0x1F,
+  DW_OP_not                = 0x20,
+  DW_OP_or                 = 0x21,
+  DW_OP_plus               = 0x22,
+  DW_OP_plus_uconst        = 0x23, // ULEB128 addend
+  DW_OP_shl                = 0x24,
+  DW_OP_shr                = 0x25,
+  DW_OP_shra               = 0x26,
+  DW_OP_xor                = 0x27,
+  DW_OP_skip               = 0x2F, // signed 2-byte constant
+  DW_OP_bra                = 0x28, // signed 2-byte constant
+  DW_OP_eq                 = 0x29,
+  DW_OP_ge                 = 0x2A,
+  DW_OP_gt                 = 0x2B,
+  DW_OP_le                 = 0x2C,
+  DW_OP_lt                 = 0x2D,
+  DW_OP_ne                 = 0x2E,
+  DW_OP_lit0               = 0x30, // Literal 0
+  DW_OP_lit1               = 0x31, // Literal 1
+  DW_OP_lit2               = 0x32, // Literal 2
+  DW_OP_lit3               = 0x33, // Literal 3
+  DW_OP_lit4               = 0x34, // Literal 4
+  DW_OP_lit5               = 0x35, // Literal 5
+  DW_OP_lit6               = 0x36, // Literal 6
+  DW_OP_lit7               = 0x37, // Literal 7
+  DW_OP_lit8               = 0x38, // Literal 8
+  DW_OP_lit9               = 0x39, // Literal 9
+  DW_OP_lit10              = 0x3A, // Literal 10
+  DW_OP_lit11              = 0x3B, // Literal 11
+  DW_OP_lit12              = 0x3C, // Literal 12
+  DW_OP_lit13              = 0x3D, // Literal 13
+  DW_OP_lit14              = 0x3E, // Literal 14
+  DW_OP_lit15              = 0x3F, // Literal 15
+  DW_OP_lit16              = 0x40, // Literal 16
+  DW_OP_lit17              = 0x41, // Literal 17
+  DW_OP_lit18              = 0x42, // Literal 18
+  DW_OP_lit19              = 0x43, // Literal 19
+  DW_OP_lit20              = 0x44, // Literal 20
+  DW_OP_lit21              = 0x45, // Literal 21
+  DW_OP_lit22              = 0x46, // Literal 22
+  DW_OP_lit23              = 0x47, // Literal 23
+  DW_OP_lit24              = 0x48, // Literal 24
+  DW_OP_lit25              = 0x49, // Literal 25
+  DW_OP_lit26              = 0x4A, // Literal 26
+  DW_OP_lit27              = 0x4B, // Literal 27
+  DW_OP_lit28              = 0x4C, // Literal 28
+  DW_OP_lit29              = 0x4D, // Literal 29
+  DW_OP_lit30              = 0x4E, // Literal 30
+  DW_OP_lit31              = 0x4F, // Literal 31
+  DW_OP_reg0               = 0x50, // Contents of reg0
+  DW_OP_reg1               = 0x51, // Contents of reg1
+  DW_OP_reg2               = 0x52, // Contents of reg2
+  DW_OP_reg3               = 0x53, // Contents of reg3
+  DW_OP_reg4               = 0x54, // Contents of reg4
+  DW_OP_reg5               = 0x55, // Contents of reg5
+  DW_OP_reg6               = 0x56, // Contents of reg6
+  DW_OP_reg7               = 0x57, // Contents of reg7
+  DW_OP_reg8               = 0x58, // Contents of reg8
+  DW_OP_reg9               = 0x59, // Contents of reg9
+  DW_OP_reg10              = 0x5A, // Contents of reg10
+  DW_OP_reg11              = 0x5B, // Contents of reg11
+  DW_OP_reg12              = 0x5C, // Contents of reg12
+  DW_OP_reg13              = 0x5D, // Contents of reg13
+  DW_OP_reg14              = 0x5E, // Contents of reg14
+  DW_OP_reg15              = 0x5F, // Contents of reg15
+  DW_OP_reg16              = 0x60, // Contents of reg16
+  DW_OP_reg17              = 0x61, // Contents of reg17
+  DW_OP_reg18              = 0x62, // Contents of reg18
+  DW_OP_reg19              = 0x63, // Contents of reg19
+  DW_OP_reg20              = 0x64, // Contents of reg20
+  DW_OP_reg21              = 0x65, // Contents of reg21
+  DW_OP_reg22              = 0x66, // Contents of reg22
+  DW_OP_reg23              = 0x67, // Contents of reg23
+  DW_OP_reg24              = 0x68, // Contents of reg24
+  DW_OP_reg25              = 0x69, // Contents of reg25
+  DW_OP_reg26              = 0x6A, // Contents of reg26
+  DW_OP_reg27              = 0x6B, // Contents of reg27
+  DW_OP_reg28              = 0x6C, // Contents of reg28
+  DW_OP_reg29              = 0x6D, // Contents of reg29
+  DW_OP_reg30              = 0x6E, // Contents of reg30
+  DW_OP_reg31              = 0x6F, // Contents of reg31
+  DW_OP_breg0              = 0x70, // base register 0 + SLEB128 offset
+  DW_OP_breg1              = 0x71, // base register 1 + SLEB128 offset
+  DW_OP_breg2              = 0x72, // base register 2 + SLEB128 offset
+  DW_OP_breg3              = 0x73, // base register 3 + SLEB128 offset
+  DW_OP_breg4              = 0x74, // base register 4 + SLEB128 offset
+  DW_OP_breg5              = 0x75, // base register 5 + SLEB128 offset
+  DW_OP_breg6              = 0x76, // base register 6 + SLEB128 offset
+  DW_OP_breg7              = 0x77, // base register 7 + SLEB128 offset
+  DW_OP_breg8              = 0x78, // base register 8 + SLEB128 offset
+  DW_OP_breg9              = 0x79, // base register 9 + SLEB128 offset
+  DW_OP_breg10             = 0x7A, // base register 10 + SLEB128 offset
+  DW_OP_breg11             = 0x7B, // base register 11 + SLEB128 offset
+  DW_OP_breg12             = 0x7C, // base register 12 + SLEB128 offset
+  DW_OP_breg13             = 0x7D, // base register 13 + SLEB128 offset
+  DW_OP_breg14             = 0x7E, // base register 14 + SLEB128 offset
+  DW_OP_breg15             = 0x7F, // base register 15 + SLEB128 offset
+  DW_OP_breg16             = 0x80, // base register 16 + SLEB128 offset
+  DW_OP_breg17             = 0x81, // base register 17 + SLEB128 offset
+  DW_OP_breg18             = 0x82, // base register 18 + SLEB128 offset
+  DW_OP_breg19             = 0x83, // base register 19 + SLEB128 offset
+  DW_OP_breg20             = 0x84, // base register 20 + SLEB128 offset
+  DW_OP_breg21             = 0x85, // base register 21 + SLEB128 offset
+  DW_OP_breg22             = 0x86, // base register 22 + SLEB128 offset
+  DW_OP_breg23             = 0x87, // base register 23 + SLEB128 offset
+  DW_OP_breg24             = 0x88, // base register 24 + SLEB128 offset
+  DW_OP_breg25             = 0x89, // base register 25 + SLEB128 offset
+  DW_OP_breg26             = 0x8A, // base register 26 + SLEB128 offset
+  DW_OP_breg27             = 0x8B, // base register 27 + SLEB128 offset
+  DW_OP_breg28             = 0x8C, // base register 28 + SLEB128 offset
+  DW_OP_breg29             = 0x8D, // base register 29 + SLEB128 offset
+  DW_OP_breg30             = 0x8E, // base register 30 + SLEB128 offset
+  DW_OP_breg31             = 0x8F, // base register 31 + SLEB128 offset
+  DW_OP_regx               = 0x90, // ULEB128 register
+  DW_OP_fbreg              = 0x91, // SLEB128 offset
+  DW_OP_bregx              = 0x92, // ULEB128 register followed by SLEB128 offset
+  DW_OP_piece              = 0x93, // ULEB128 size of piece addressed
+  DW_OP_deref_size         = 0x94, // 1-byte size of data retrieved
+  DW_OP_xderef_size        = 0x95, // 1-byte size of data retrieved
+  DW_OP_nop                = 0x96,
+  DW_OP_push_object_addres = 0x97,
+  DW_OP_call2              = 0x98, // 2-byte offset of DIE
+  DW_OP_call4              = 0x99, // 4-byte offset of DIE
+  DW_OP_call_ref           = 0x9A, // 4- or 8-byte offset of DIE
+  DW_OP_lo_user            = 0xE0,
+  DW_OP_APPLE_uninit       = 0xF0,
+  DW_OP_hi_user            = 0xFF
+};
+
+
+#endif

third_party/libunwind/include/__libunwind_config.h

@@ -0,0 +1,205 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef ____LIBUNWIND_CONFIG_H__
+#define ____LIBUNWIND_CONFIG_H__
+
+#define _LIBUNWIND_VERSION 15000
+
+#if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) && \
+    !defined(__ARM_DWARF_EH__) && !defined(__SEH__)
+#define _LIBUNWIND_ARM_EHABI
+#endif
+
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_X86       8
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_X86_64    32
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_PPC       112
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_PPC64     116
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_ARM64     95
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_ARM       287
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_OR1K      32
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_MIPS      65
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_SPARC     31
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_SPARC64   31
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_HEXAGON   34
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_RISCV     64
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_VE        143
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_S390X     83
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER_LOONGARCH 64
+
+#if defined(_LIBUNWIND_IS_NATIVE_ONLY)
+# if defined(__linux__)
+#  define _LIBUNWIND_TARGET_LINUX 1
+# endif
+# if defined(__i386__)
+#  define _LIBUNWIND_TARGET_I386
+#  define _LIBUNWIND_CONTEXT_SIZE 8
+#  define _LIBUNWIND_CURSOR_SIZE 15
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_X86
+# elif defined(__x86_64__)
+#  define _LIBUNWIND_TARGET_X86_64 1
+#  if defined(_WIN64)
+#    define _LIBUNWIND_CONTEXT_SIZE 54
+#    ifdef __SEH__
+#      define _LIBUNWIND_CURSOR_SIZE 204
+#    else
+#      define _LIBUNWIND_CURSOR_SIZE 66
+#    endif
+#  else
+#    define _LIBUNWIND_CONTEXT_SIZE 21
+#    define _LIBUNWIND_CURSOR_SIZE 33
+#  endif
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_X86_64
+# elif defined(__powerpc64__)
+#  define _LIBUNWIND_TARGET_PPC64 1
+#  define _LIBUNWIND_CONTEXT_SIZE 167
+#  define _LIBUNWIND_CURSOR_SIZE 179
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_PPC64
+# elif defined(__powerpc__)
+#  define _LIBUNWIND_TARGET_PPC 1
+#  define _LIBUNWIND_CONTEXT_SIZE 117
+#  define _LIBUNWIND_CURSOR_SIZE 124
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_PPC
+# elif defined(__aarch64__)
+#  define _LIBUNWIND_TARGET_AARCH64 1
+#  define _LIBUNWIND_CONTEXT_SIZE 66
+#  if defined(__SEH__)
+#    define _LIBUNWIND_CURSOR_SIZE 164
+#  else
+#    define _LIBUNWIND_CURSOR_SIZE 78
+#  endif
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_ARM64
+# elif defined(__arm__)
+#  define _LIBUNWIND_TARGET_ARM 1
+#  if defined(__SEH__)
+#    define _LIBUNWIND_CONTEXT_SIZE 42
+#    define _LIBUNWIND_CURSOR_SIZE 80
+#  elif defined(__ARM_WMMX)
+#    define _LIBUNWIND_CONTEXT_SIZE 61
+#    define _LIBUNWIND_CURSOR_SIZE 68
+#  else
+#    define _LIBUNWIND_CONTEXT_SIZE 42
+#    define _LIBUNWIND_CURSOR_SIZE 49
+#  endif
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_ARM
+# elif defined(__or1k__)
+#  define _LIBUNWIND_TARGET_OR1K 1
+#  define _LIBUNWIND_CONTEXT_SIZE 16
+#  define _LIBUNWIND_CURSOR_SIZE 24
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_OR1K
+# elif defined(__hexagon__)
+#  define _LIBUNWIND_TARGET_HEXAGON 1
+// Values here change when : Registers.hpp - hexagon_thread_state_t change
+#  define _LIBUNWIND_CONTEXT_SIZE 18
+#  define _LIBUNWIND_CURSOR_SIZE 24
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_HEXAGON
+# elif defined(__mips__)
+#  if defined(_ABIO32) && _MIPS_SIM == _ABIO32
+#    define _LIBUNWIND_TARGET_MIPS_O32 1
+#    if defined(__mips_hard_float)
+#      define _LIBUNWIND_CONTEXT_SIZE 50
+#      define _LIBUNWIND_CURSOR_SIZE 57
+#    else
+#      define _LIBUNWIND_CONTEXT_SIZE 18
+#      define _LIBUNWIND_CURSOR_SIZE 24
+#    endif
+#  elif defined(_ABIN32) && _MIPS_SIM == _ABIN32
+#    define _LIBUNWIND_TARGET_MIPS_NEWABI 1
+#    if defined(__mips_hard_float)
+#      define _LIBUNWIND_CONTEXT_SIZE 67
+#      define _LIBUNWIND_CURSOR_SIZE 74
+#    else
+#      define _LIBUNWIND_CONTEXT_SIZE 35
+#      define _LIBUNWIND_CURSOR_SIZE 42
+#    endif
+#  elif defined(_ABI64) && _MIPS_SIM == _ABI64
+#    define _LIBUNWIND_TARGET_MIPS_NEWABI 1
+#    if defined(__mips_hard_float)
+#      define _LIBUNWIND_CONTEXT_SIZE 67
+#      define _LIBUNWIND_CURSOR_SIZE 79
+#    else
+#      define _LIBUNWIND_CONTEXT_SIZE 35
+#      define _LIBUNWIND_CURSOR_SIZE 47
+#    endif
+#  else
+#    error "Unsupported MIPS ABI and/or environment"
+#  endif
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_MIPS
+#elif defined(__sparc__) && defined(__arch64__)
+#define _LIBUNWIND_TARGET_SPARC64 1
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER                                      \
+  _LIBUNWIND_HIGHEST_DWARF_REGISTER_SPARC64
+#define _LIBUNWIND_CONTEXT_SIZE 33
+#define _LIBUNWIND_CURSOR_SIZE 45
+# elif defined(__sparc__)
+  #define _LIBUNWIND_TARGET_SPARC 1
+  #define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_SPARC
+  #define _LIBUNWIND_CONTEXT_SIZE 16
+  #define _LIBUNWIND_CURSOR_SIZE 23
+# elif defined(__riscv)
+#  define _LIBUNWIND_TARGET_RISCV 1
+#  if defined(__riscv_flen)
+#   define RISCV_FLEN __riscv_flen
+#  else
+#   define RISCV_FLEN 0
+#  endif
+#  define _LIBUNWIND_CONTEXT_SIZE (32 * (__riscv_xlen + RISCV_FLEN) / 64)
+#  if __riscv_xlen == 32
+#   define _LIBUNWIND_CURSOR_SIZE (_LIBUNWIND_CONTEXT_SIZE + 7)
+#  elif __riscv_xlen == 64
+#   define _LIBUNWIND_CURSOR_SIZE (_LIBUNWIND_CONTEXT_SIZE + 12)
+#  else
+#   error "Unsupported RISC-V ABI"
+#  endif
+# define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_RISCV
+# elif defined(__ve__)
+#  define _LIBUNWIND_TARGET_VE 1
+#  define _LIBUNWIND_CONTEXT_SIZE 67
+#  define _LIBUNWIND_CURSOR_SIZE 79
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_VE
+# elif defined(__s390x__)
+#  define _LIBUNWIND_TARGET_S390X 1
+#  define _LIBUNWIND_CONTEXT_SIZE 34
+#  define _LIBUNWIND_CURSOR_SIZE 46
+#  define _LIBUNWIND_HIGHEST_DWARF_REGISTER _LIBUNWIND_HIGHEST_DWARF_REGISTER_S390X
+#elif defined(__loongarch__)
+#define _LIBUNWIND_TARGET_LOONGARCH 1
+#if __loongarch_grlen == 64
+#define _LIBUNWIND_CONTEXT_SIZE 65
+#define _LIBUNWIND_CURSOR_SIZE 77
+#else
+#error "Unsupported LoongArch ABI"
+#endif
+#define _LIBUNWIND_HIGHEST_DWARF_REGISTER                                      \
+  _LIBUNWIND_HIGHEST_DWARF_REGISTER_LOONGARCH
+# else
+#  error "Unsupported architecture."
+# endif
+#else // !_LIBUNWIND_IS_NATIVE_ONLY
+# define _LIBUNWIND_TARGET_I386
+# define _LIBUNWIND_TARGET_X86_64 1
+# define _LIBUNWIND_TARGET_PPC 1
+# define _LIBUNWIND_TARGET_PPC64 1
+# define _LIBUNWIND_TARGET_AARCH64 1
+# define _LIBUNWIND_TARGET_ARM 1
+# define _LIBUNWIND_TARGET_OR1K 1
+# define _LIBUNWIND_TARGET_MIPS_O32 1
+# define _LIBUNWIND_TARGET_MIPS_NEWABI 1
+# define _LIBUNWIND_TARGET_SPARC 1
+# define _LIBUNWIND_TARGET_SPARC64 1
+# define _LIBUNWIND_TARGET_HEXAGON 1
+# define _LIBUNWIND_TARGET_RISCV 1
+# define _LIBUNWIND_TARGET_VE 1
+# define _LIBUNWIND_TARGET_S390X 1
+ #define _LIBUNWIND_TARGET_LOONGARCH 1
+# define _LIBUNWIND_CONTEXT_SIZE 167
+# define _LIBUNWIND_CURSOR_SIZE 204
+# define _LIBUNWIND_HIGHEST_DWARF_REGISTER 287
+#endif // _LIBUNWIND_IS_NATIVE_ONLY
+
+#endif // ____LIBUNWIND_CONFIG_H__

third_party/libunwind/include/mach-o/compact_unwind_encoding.h

@@ -0,0 +1,477 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// Darwin's alternative to DWARF based unwind encodings.
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifndef __COMPACT_UNWIND_ENCODING__
+#define __COMPACT_UNWIND_ENCODING__
+
+#include "libc/isystem/stdint.h"
+
+//
+// Compilers can emit standard DWARF FDEs in the __TEXT,__eh_frame section
+// of object files. Or compilers can emit compact unwind information in
+// the __LD,__compact_unwind section.
+//
+// When the linker creates a final linked image, it will create a
+// __TEXT,__unwind_info section.  This section is a small and fast way for the
+// runtime to access unwind info for any given function.  If the compiler
+// emitted compact unwind info for the function, that compact unwind info will
+// be encoded in the __TEXT,__unwind_info section. If the compiler emitted
+// DWARF unwind info, the __TEXT,__unwind_info section will contain the offset
+// of the FDE in the __TEXT,__eh_frame section in the final linked image.
+//
+// Note: Previously, the linker would transform some DWARF unwind infos into
+//       compact unwind info.  But that is fragile and no longer done.
+
+
+//
+// The compact unwind encoding is a 32-bit value which encoded in an
+// architecture specific way, which registers to restore from where, and how
+// to unwind out of the function.
+//
+typedef uint32_t compact_unwind_encoding_t;
+
+
+// architecture independent bits
+enum {
+    UNWIND_IS_NOT_FUNCTION_START           = 0x80000000,
+    UNWIND_HAS_LSDA                        = 0x40000000,
+    UNWIND_PERSONALITY_MASK                = 0x30000000,
+};
+
+
+
+
+//
+// x86
+//
+// 1-bit: start
+// 1-bit: has lsda
+// 2-bit: personality index
+//
+// 4-bits: 0=old, 1=ebp based, 2=stack-imm, 3=stack-ind, 4=DWARF
+//  ebp based:
+//        15-bits (5*3-bits per reg) register permutation
+//        8-bits for stack offset
+//  frameless:
+//        8-bits stack size
+//        3-bits stack adjust
+//        3-bits register count
+//        10-bits register permutation
+//
+enum {
+    UNWIND_X86_MODE_MASK                         = 0x0F000000,
+    UNWIND_X86_MODE_EBP_FRAME                    = 0x01000000,
+    UNWIND_X86_MODE_STACK_IMMD                   = 0x02000000,
+    UNWIND_X86_MODE_STACK_IND                    = 0x03000000,
+    UNWIND_X86_MODE_DWARF                        = 0x04000000,
+
+    UNWIND_X86_EBP_FRAME_REGISTERS               = 0x00007FFF,
+    UNWIND_X86_EBP_FRAME_OFFSET                  = 0x00FF0000,
+
+    UNWIND_X86_FRAMELESS_STACK_SIZE              = 0x00FF0000,
+    UNWIND_X86_FRAMELESS_STACK_ADJUST            = 0x0000E000,
+    UNWIND_X86_FRAMELESS_STACK_REG_COUNT         = 0x00001C00,
+    UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION   = 0x000003FF,
+
+    UNWIND_X86_DWARF_SECTION_OFFSET              = 0x00FFFFFF,
+};
+
+enum {
+    UNWIND_X86_REG_NONE     = 0,
+    UNWIND_X86_REG_EBX      = 1,
+    UNWIND_X86_REG_ECX      = 2,
+    UNWIND_X86_REG_EDX      = 3,
+    UNWIND_X86_REG_EDI      = 4,
+    UNWIND_X86_REG_ESI      = 5,
+    UNWIND_X86_REG_EBP      = 6,
+};
+
+//
+// For x86 there are four modes for the compact unwind encoding:
+// UNWIND_X86_MODE_EBP_FRAME:
+//    EBP based frame where EBP is push on stack immediately after return address,
+//    then ESP is moved to EBP. Thus, to unwind ESP is restored with the current
+//    EPB value, then EBP is restored by popping off the stack, and the return
+//    is done by popping the stack once more into the pc.
+//    All non-volatile registers that need to be restored must have been saved
+//    in a small range in the stack that starts EBP-4 to EBP-1020.  The offset/4
+//    is encoded in the UNWIND_X86_EBP_FRAME_OFFSET bits.  The registers saved
+//    are encoded in the UNWIND_X86_EBP_FRAME_REGISTERS bits as five 3-bit entries.
+//    Each entry contains which register to restore.
+// UNWIND_X86_MODE_STACK_IMMD:
+//    A "frameless" (EBP not used as frame pointer) function with a small
+//    constant stack size.  To return, a constant (encoded in the compact
+//    unwind encoding) is added to the ESP. Then the return is done by
+//    popping the stack into the pc.
+//    All non-volatile registers that need to be restored must have been saved
+//    on the stack immediately after the return address.  The stack_size/4 is
+//    encoded in the UNWIND_X86_FRAMELESS_STACK_SIZE (max stack size is 1024).
+//    The number of registers saved is encoded in UNWIND_X86_FRAMELESS_STACK_REG_COUNT.
+//    UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION contains which registers were
+//    saved and their order.
+// UNWIND_X86_MODE_STACK_IND:
+//    A "frameless" (EBP not used as frame pointer) function large constant
+//    stack size.  This case is like the previous, except the stack size is too
+//    large to encode in the compact unwind encoding.  Instead it requires that
+//    the function contains "subl $nnnnnnnn,ESP" in its prolog.  The compact
+//    encoding contains the offset to the nnnnnnnn value in the function in
+//    UNWIND_X86_FRAMELESS_STACK_SIZE.
+// UNWIND_X86_MODE_DWARF:
+//    No compact unwind encoding is available.  Instead the low 24-bits of the
+//    compact encoding is the offset of the DWARF FDE in the __eh_frame section.
+//    This mode is never used in object files.  It is only generated by the
+//    linker in final linked images which have only DWARF unwind info for a
+//    function.
+//
+// The permutation encoding is a Lehmer code sequence encoded into a
+// single variable-base number so we can encode the ordering of up to
+// six registers in a 10-bit space.
+//
+// The following is the algorithm used to create the permutation encoding used
+// with frameless stacks.  It is passed the number of registers to be saved and
+// an array of the register numbers saved.
+//
+//uint32_t permute_encode(uint32_t registerCount, const uint32_t registers[6])
+//{
+//    uint32_t renumregs[6];
+//    for (int i=6-registerCount; i < 6; ++i) {
+//        int countless = 0;
+//        for (int j=6-registerCount; j < i; ++j) {
+//            if ( registers[j] < registers[i] )
+//                ++countless;
+//        }
+//        renumregs[i] = registers[i] - countless -1;
+//    }
+//    uint32_t permutationEncoding = 0;
+//    switch ( registerCount ) {
+//        case 6:
+//            permutationEncoding |= (120*renumregs[0] + 24*renumregs[1]
+//                                    + 6*renumregs[2] + 2*renumregs[3]
+//                                      + renumregs[4]);
+//            break;
+//        case 5:
+//            permutationEncoding |= (120*renumregs[1] + 24*renumregs[2]
+//                                    + 6*renumregs[3] + 2*renumregs[4]
+//                                      + renumregs[5]);
+//            break;
+//        case 4:
+//            permutationEncoding |= (60*renumregs[2] + 12*renumregs[3]
+//                                   + 3*renumregs[4] + renumregs[5]);
+//            break;
+//        case 3:
+//            permutationEncoding |= (20*renumregs[3] + 4*renumregs[4]
+//                                     + renumregs[5]);
+//            break;
+//        case 2:
+//            permutationEncoding |= (5*renumregs[4] + renumregs[5]);
+//            break;
+//        case 1:
+//            permutationEncoding |= (renumregs[5]);
+//            break;
+//    }
+//    return permutationEncoding;
+//}
+//
+
+
+
+
+//
+// x86_64
+//
+// 1-bit: start
+// 1-bit: has lsda
+// 2-bit: personality index
+//
+// 4-bits: 0=old, 1=rbp based, 2=stack-imm, 3=stack-ind, 4=DWARF
+//  rbp based:
+//        15-bits (5*3-bits per reg) register permutation
+//        8-bits for stack offset
+//  frameless:
+//        8-bits stack size
+//        3-bits stack adjust
+//        3-bits register count
+//        10-bits register permutation
+//
+enum {
+    UNWIND_X86_64_MODE_MASK                         = 0x0F000000,
+    UNWIND_X86_64_MODE_RBP_FRAME                    = 0x01000000,
+    UNWIND_X86_64_MODE_STACK_IMMD                   = 0x02000000,
+    UNWIND_X86_64_MODE_STACK_IND                    = 0x03000000,
+    UNWIND_X86_64_MODE_DWARF                        = 0x04000000,
+
+    UNWIND_X86_64_RBP_FRAME_REGISTERS               = 0x00007FFF,
+    UNWIND_X86_64_RBP_FRAME_OFFSET                  = 0x00FF0000,
+
+    UNWIND_X86_64_FRAMELESS_STACK_SIZE              = 0x00FF0000,
+    UNWIND_X86_64_FRAMELESS_STACK_ADJUST            = 0x0000E000,
+    UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT         = 0x00001C00,
+    UNWIND_X86_64_FRAMELESS_STACK_REG_PERMUTATION   = 0x000003FF,
+
+    UNWIND_X86_64_DWARF_SECTION_OFFSET              = 0x00FFFFFF,
+};
+
+enum {
+    UNWIND_X86_64_REG_NONE       = 0,
+    UNWIND_X86_64_REG_RBX        = 1,
+    UNWIND_X86_64_REG_R12        = 2,
+    UNWIND_X86_64_REG_R13        = 3,
+    UNWIND_X86_64_REG_R14        = 4,
+    UNWIND_X86_64_REG_R15        = 5,
+    UNWIND_X86_64_REG_RBP        = 6,
+};
+//
+// For x86_64 there are four modes for the compact unwind encoding:
+// UNWIND_X86_64_MODE_RBP_FRAME:
+//    RBP based frame where RBP is push on stack immediately after return address,
+//    then RSP is moved to RBP. Thus, to unwind RSP is restored with the current
+//    EPB value, then RBP is restored by popping off the stack, and the return
+//    is done by popping the stack once more into the pc.
+//    All non-volatile registers that need to be restored must have been saved
+//    in a small range in the stack that starts RBP-8 to RBP-2040.  The offset/8
+//    is encoded in the UNWIND_X86_64_RBP_FRAME_OFFSET bits.  The registers saved
+//    are encoded in the UNWIND_X86_64_RBP_FRAME_REGISTERS bits as five 3-bit entries.
+//    Each entry contains which register to restore.
+// UNWIND_X86_64_MODE_STACK_IMMD:
+//    A "frameless" (RBP not used as frame pointer) function with a small
+//    constant stack size.  To return, a constant (encoded in the compact
+//    unwind encoding) is added to the RSP. Then the return is done by
+//    popping the stack into the pc.
+//    All non-volatile registers that need to be restored must have been saved
+//    on the stack immediately after the return address.  The stack_size/8 is
+//    encoded in the UNWIND_X86_64_FRAMELESS_STACK_SIZE (max stack size is 2048).
+//    The number of registers saved is encoded in UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT.
+//    UNWIND_X86_64_FRAMELESS_STACK_REG_PERMUTATION contains which registers were
+//    saved and their order.
+// UNWIND_X86_64_MODE_STACK_IND:
+//    A "frameless" (RBP not used as frame pointer) function large constant
+//    stack size.  This case is like the previous, except the stack size is too
+//    large to encode in the compact unwind encoding.  Instead it requires that
+//    the function contains "subq $nnnnnnnn,RSP" in its prolog.  The compact
+//    encoding contains the offset to the nnnnnnnn value in the function in
+//    UNWIND_X86_64_FRAMELESS_STACK_SIZE.
+// UNWIND_X86_64_MODE_DWARF:
+//    No compact unwind encoding is available.  Instead the low 24-bits of the
+//    compact encoding is the offset of the DWARF FDE in the __eh_frame section.
+//    This mode is never used in object files.  It is only generated by the
+//    linker in final linked images which have only DWARF unwind info for a
+//    function.
+//
+
+
+// ARM64
+//
+// 1-bit: start
+// 1-bit: has lsda
+// 2-bit: personality index
+//
+// 4-bits: 4=frame-based, 3=DWARF, 2=frameless
+//  frameless:
+//        12-bits of stack size
+//  frame-based:
+//        4-bits D reg pairs saved
+//        5-bits X reg pairs saved
+//  DWARF:
+//        24-bits offset of DWARF FDE in __eh_frame section
+//
+enum {
+    UNWIND_ARM64_MODE_MASK                     = 0x0F000000,
+    UNWIND_ARM64_MODE_FRAMELESS                = 0x02000000,
+    UNWIND_ARM64_MODE_DWARF                    = 0x03000000,
+    UNWIND_ARM64_MODE_FRAME                    = 0x04000000,
+
+    UNWIND_ARM64_FRAME_X19_X20_PAIR            = 0x00000001,
+    UNWIND_ARM64_FRAME_X21_X22_PAIR            = 0x00000002,
+    UNWIND_ARM64_FRAME_X23_X24_PAIR            = 0x00000004,
+    UNWIND_ARM64_FRAME_X25_X26_PAIR            = 0x00000008,
+    UNWIND_ARM64_FRAME_X27_X28_PAIR            = 0x00000010,
+    UNWIND_ARM64_FRAME_D8_D9_PAIR              = 0x00000100,
+    UNWIND_ARM64_FRAME_D10_D11_PAIR            = 0x00000200,
+    UNWIND_ARM64_FRAME_D12_D13_PAIR            = 0x00000400,
+    UNWIND_ARM64_FRAME_D14_D15_PAIR            = 0x00000800,
+
+    UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK     = 0x00FFF000,
+    UNWIND_ARM64_DWARF_SECTION_OFFSET          = 0x00FFFFFF,
+};
+// For arm64 there are three modes for the compact unwind encoding:
+// UNWIND_ARM64_MODE_FRAME:
+//    This is a standard arm64 prolog where FP/LR are immediately pushed on the
+//    stack, then SP is copied to FP. If there are any non-volatile registers
+//    saved, then are copied into the stack frame in pairs in a contiguous
+//    range right below the saved FP/LR pair.  Any subset of the five X pairs
+//    and four D pairs can be saved, but the memory layout must be in register
+//    number order.
+// UNWIND_ARM64_MODE_FRAMELESS:
+//    A "frameless" leaf function, where FP/LR are not saved. The return address
+//    remains in LR throughout the function. If any non-volatile registers
+//    are saved, they must be pushed onto the stack before any stack space is
+//    allocated for local variables.  The stack sized (including any saved
+//    non-volatile registers) divided by 16 is encoded in the bits
+//    UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK.
+// UNWIND_ARM64_MODE_DWARF:
+//    No compact unwind encoding is available.  Instead the low 24-bits of the
+//    compact encoding is the offset of the DWARF FDE in the __eh_frame section.
+//    This mode is never used in object files.  It is only generated by the
+//    linker in final linked images which have only DWARF unwind info for a
+//    function.
+//
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+//
+//  Relocatable Object Files: __LD,__compact_unwind
+//
+////////////////////////////////////////////////////////////////////////////////
+
+//
+// A compiler can generated compact unwind information for a function by adding
+// a "row" to the __LD,__compact_unwind section.  This section has the
+// S_ATTR_DEBUG bit set, so the section will be ignored by older linkers.
+// It is removed by the new linker, so never ends up in final executables.
+// This section is a table, initially with one row per function (that needs
+// unwind info).  The table columns and some conceptual entries are:
+//
+//     range-start               pointer to start of function/range
+//     range-length
+//     compact-unwind-encoding   32-bit encoding
+//     personality-function      or zero if no personality function
+//     lsda                      or zero if no LSDA data
+//
+// The length and encoding fields are 32-bits.  The other are all pointer sized.
+//
+// In x86_64 assembly, these entry would look like:
+//
+//     .section __LD,__compact_unwind,regular,debug
+//
+//     #compact unwind for _foo
+//     .quad    _foo
+//     .set     L1,LfooEnd-_foo
+//     .long    L1
+//     .long    0x01010001
+//     .quad    0
+//     .quad    0
+//
+//     #compact unwind for _bar
+//     .quad    _bar
+//     .set     L2,LbarEnd-_bar
+//     .long    L2
+//     .long    0x01020011
+//     .quad    __gxx_personality
+//     .quad    except_tab1
+//
+//
+// Notes: There is no need for any labels in the the __compact_unwind section.
+//        The use of the .set directive is to force the evaluation of the
+//        range-length at assembly time, instead of generating relocations.
+//
+// To support future compiler optimizations where which non-volatile registers
+// are saved changes within a function (e.g. delay saving non-volatiles until
+// necessary), there can by multiple lines in the __compact_unwind table for one
+// function, each with a different (non-overlapping) range and each with
+// different compact unwind encodings that correspond to the non-volatiles
+// saved at that range of the function.
+//
+// If a particular function is so wacky that there is no compact unwind way
+// to encode it, then the compiler can emit traditional DWARF unwind info.
+// The runtime will use which ever is available.
+//
+// Runtime support for compact unwind encodings are only available on 10.6
+// and later.  So, the compiler should not generate it when targeting pre-10.6.
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+//
+//  Final Linked Images: __TEXT,__unwind_info
+//
+////////////////////////////////////////////////////////////////////////////////
+
+//
+// The __TEXT,__unwind_info section is laid out for an efficient two level lookup.
+// The header of the section contains a coarse index that maps function address
+// to the page (4096 byte block) containing the unwind info for that function.
+//
+
+#define UNWIND_SECTION_VERSION 1
+struct unwind_info_section_header
+{
+    uint32_t    version;            // UNWIND_SECTION_VERSION
+    uint32_t    commonEncodingsArraySectionOffset;
+    uint32_t    commonEncodingsArrayCount;
+    uint32_t    personalityArraySectionOffset;
+    uint32_t    personalityArrayCount;
+    uint32_t    indexSectionOffset;
+    uint32_t    indexCount;
+    // compact_unwind_encoding_t[]
+    // uint32_t personalities[]
+    // unwind_info_section_header_index_entry[]
+    // unwind_info_section_header_lsda_index_entry[]
+};
+
+struct unwind_info_section_header_index_entry
+{
+    uint32_t        functionOffset;
+    uint32_t        secondLevelPagesSectionOffset;  // section offset to start of regular or compress page
+    uint32_t        lsdaIndexArraySectionOffset;    // section offset to start of lsda_index array for this range
+};
+
+struct unwind_info_section_header_lsda_index_entry
+{
+    uint32_t        functionOffset;
+    uint32_t        lsdaOffset;
+};
+
+//
+// There are two kinds of second level index pages: regular and compressed.
+// A compressed page can hold up to 1021 entries, but it cannot be used
+// if too many different encoding types are used.  The regular page holds
+// 511 entries.
+//
+
+struct unwind_info_regular_second_level_entry
+{
+    uint32_t                    functionOffset;
+    compact_unwind_encoding_t    encoding;
+};
+
+#define UNWIND_SECOND_LEVEL_REGULAR 2
+struct unwind_info_regular_second_level_page_header
+{
+    uint32_t    kind;    // UNWIND_SECOND_LEVEL_REGULAR
+    uint16_t    entryPageOffset;
+    uint16_t    entryCount;
+    // entry array
+};
+
+#define UNWIND_SECOND_LEVEL_COMPRESSED 3
+struct unwind_info_compressed_second_level_page_header
+{
+    uint32_t    kind;    // UNWIND_SECOND_LEVEL_COMPRESSED
+    uint16_t    entryPageOffset;
+    uint16_t    entryCount;
+    uint16_t    encodingsPageOffset;
+    uint16_t    encodingsCount;
+    // 32-bit entry array
+    // encodings array
+};
+
+#define UNWIND_INFO_COMPRESSED_ENTRY_FUNC_OFFSET(entry)            (entry & 0x00FFFFFF)
+#define UNWIND_INFO_COMPRESSED_ENTRY_ENCODING_INDEX(entry)        ((entry >> 24) & 0xFF)
+
+
+
+#endif
+

third_party/libunwind/include/unwind.h

@@ -0,0 +1,207 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// C++ ABI Level 1 ABI documented at:
+//   https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __UNWIND_H__
+#define __UNWIND_H__
+
+#include "third_party/libunwind/include/__libunwind_config.h"
+
+#include "libc/isystem/stdint.h"
+#include "libc/isystem/stddef.h"
+
+#if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__) && defined(_WIN32)
+#include <windows.h>
+#include <ntverp.h>
+#endif
+
+#if defined(__APPLE__)
+#define LIBUNWIND_UNAVAIL __attribute__ (( unavailable ))
+#else
+#define LIBUNWIND_UNAVAIL
+#endif
+
+typedef enum {
+  _URC_NO_REASON = 0,
+  _URC_OK = 0,
+  _URC_FOREIGN_EXCEPTION_CAUGHT = 1,
+  _URC_FATAL_PHASE2_ERROR = 2,
+  _URC_FATAL_PHASE1_ERROR = 3,
+  _URC_NORMAL_STOP = 4,
+  _URC_END_OF_STACK = 5,
+  _URC_HANDLER_FOUND = 6,
+  _URC_INSTALL_CONTEXT = 7,
+  _URC_CONTINUE_UNWIND = 8,
+#if defined(_LIBUNWIND_ARM_EHABI)
+  _URC_FAILURE = 9
+#endif
+} _Unwind_Reason_Code;
+
+typedef enum {
+  _UA_SEARCH_PHASE = 1,
+  _UA_CLEANUP_PHASE = 2,
+  _UA_HANDLER_FRAME = 4,
+  _UA_FORCE_UNWIND = 8,
+  _UA_END_OF_STACK = 16 // gcc extension to C++ ABI
+} _Unwind_Action;
+
+typedef struct _Unwind_Context _Unwind_Context;   // opaque
+
+#if defined(_LIBUNWIND_ARM_EHABI)
+#include "third_party/libunwind/include/unwind_arm_ehabi.h"
+#else
+#include "third_party/libunwind/include/unwind_itanium.h"
+#endif
+
+typedef _Unwind_Reason_Code (*_Unwind_Stop_Fn)
+    (int version,
+     _Unwind_Action actions,
+     _Unwind_Exception_Class exceptionClass,
+     _Unwind_Exception* exceptionObject,
+     struct _Unwind_Context* context,
+     void* stop_parameter);
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern uintptr_t _Unwind_GetRegionStart(struct _Unwind_Context *context);
+extern uintptr_t
+    _Unwind_GetLanguageSpecificData(struct _Unwind_Context *context);
+#ifdef __USING_SJLJ_EXCEPTIONS__
+extern _Unwind_Reason_Code
+    _Unwind_SjLj_ForcedUnwind(_Unwind_Exception *exception_object,
+                              _Unwind_Stop_Fn stop, void *stop_parameter);
+#else
+extern _Unwind_Reason_Code
+    _Unwind_ForcedUnwind(_Unwind_Exception *exception_object,
+                         _Unwind_Stop_Fn stop, void *stop_parameter);
+#endif
+
+#ifdef __USING_SJLJ_EXCEPTIONS__
+typedef struct _Unwind_FunctionContext *_Unwind_FunctionContext_t;
+extern void _Unwind_SjLj_Register(_Unwind_FunctionContext_t fc);
+extern void _Unwind_SjLj_Unregister(_Unwind_FunctionContext_t fc);
+#endif
+
+//
+// The following are semi-supported extensions to the C++ ABI
+//
+
+//
+//  called by __cxa_rethrow().
+//
+#ifdef __USING_SJLJ_EXCEPTIONS__
+extern _Unwind_Reason_Code
+    _Unwind_SjLj_Resume_or_Rethrow(_Unwind_Exception *exception_object);
+#else
+extern _Unwind_Reason_Code
+    _Unwind_Resume_or_Rethrow(_Unwind_Exception *exception_object);
+#endif
+
+// _Unwind_Backtrace() is a gcc extension that walks the stack and calls the
+// _Unwind_Trace_Fn once per frame until it reaches the bottom of the stack
+// or the _Unwind_Trace_Fn function returns something other than _URC_NO_REASON.
+typedef _Unwind_Reason_Code (*_Unwind_Trace_Fn)(struct _Unwind_Context *,
+                                                void *);
+extern _Unwind_Reason_Code _Unwind_Backtrace(_Unwind_Trace_Fn, void *);
+
+// _Unwind_GetCFA is a gcc extension that can be called from within a
+// personality handler to get the CFA (stack pointer before call) of
+// current frame.
+extern uintptr_t _Unwind_GetCFA(struct _Unwind_Context *);
+
+
+// _Unwind_GetIPInfo is a gcc extension that can be called from within a
+// personality handler.  Similar to _Unwind_GetIP() but also returns in
+// *ipBefore a non-zero value if the instruction pointer is at or before the
+// instruction causing the unwind. Normally, in a function call, the IP returned
+// is the return address which is after the call instruction and may be past the
+// end of the function containing the call instruction.
+extern uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
+                                   int *ipBefore);
+
+
+// __register_frame() is used with dynamically generated code to register the
+// FDE for a generated (JIT) code.  The FDE must use pc-rel addressing to point
+// to its function and optional LSDA.
+// __register_frame() has existed in all versions of Mac OS X, but in 10.4 and
+// 10.5 it was buggy and did not actually register the FDE with the unwinder.
+// In 10.6 and later it does register properly.
+extern void __register_frame(const void *fde);
+extern void __deregister_frame(const void *fde);
+
+// _Unwind_Find_FDE() will locate the FDE if the pc is in some function that has
+// an associated FDE. Note, Mac OS X 10.6 and later, introduces "compact unwind
+// info" which the runtime uses in preference to DWARF unwind info.  This
+// function will only work if the target function has an FDE but no compact
+// unwind info.
+struct dwarf_eh_bases {
+  uintptr_t tbase;
+  uintptr_t dbase;
+  uintptr_t func;
+};
+extern const void *_Unwind_Find_FDE(const void *pc, struct dwarf_eh_bases *);
+
+
+// This function attempts to find the start (address of first instruction) of
+// a function given an address inside the function.  It only works if the
+// function has an FDE (DWARF unwind info).
+// This function is unimplemented on Mac OS X 10.6 and later.  Instead, use
+// _Unwind_Find_FDE() and look at the dwarf_eh_bases.func result.
+extern void *_Unwind_FindEnclosingFunction(void *pc);
+
+// Mac OS X does not support text-rel and data-rel addressing so these functions
+// are unimplemented.
+extern uintptr_t _Unwind_GetDataRelBase(struct _Unwind_Context *context)
+    LIBUNWIND_UNAVAIL;
+extern uintptr_t _Unwind_GetTextRelBase(struct _Unwind_Context *context)
+    LIBUNWIND_UNAVAIL;
+
+// Mac OS X 10.4 and 10.5 had implementations of these functions in
+// libgcc_s.dylib, but they never worked.
+/// These functions are no longer available on Mac OS X.
+extern void __register_frame_info_bases(const void *fde, void *ob, void *tb,
+                                        void *db) LIBUNWIND_UNAVAIL;
+extern void __register_frame_info(const void *fde, void *ob)
+    LIBUNWIND_UNAVAIL;
+extern void __register_frame_info_table_bases(const void *fde, void *ob,
+                                              void *tb, void *db)
+    LIBUNWIND_UNAVAIL;
+extern void __register_frame_info_table(const void *fde, void *ob)
+    LIBUNWIND_UNAVAIL;
+extern void __register_frame_table(const void *fde)
+    LIBUNWIND_UNAVAIL;
+extern void *__deregister_frame_info(const void *fde)
+    LIBUNWIND_UNAVAIL;
+extern void *__deregister_frame_info_bases(const void *fde)
+    LIBUNWIND_UNAVAIL;
+
+#if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
+#ifndef _WIN32
+typedef struct _EXCEPTION_RECORD EXCEPTION_RECORD;
+typedef struct _CONTEXT CONTEXT;
+typedef struct _DISPATCHER_CONTEXT DISPATCHER_CONTEXT;
+#elif !defined(__MINGW32__) && VER_PRODUCTBUILD < 8000
+typedef struct _DISPATCHER_CONTEXT DISPATCHER_CONTEXT;
+#endif
+// This is the common wrapper for GCC-style personality functions with SEH.
+extern EXCEPTION_DISPOSITION _GCC_specific_handler(EXCEPTION_RECORD *exc,
+                                                   void *frame, CONTEXT *ctx,
+                                                   DISPATCHER_CONTEXT *disp,
+                                                   _Unwind_Personality_Fn pers);
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // __UNWIND_H__

third_party/libunwind/include/unwind_arm_ehabi.h

@@ -0,0 +1,170 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// C++ ABI Level 1 ABI documented at:
+//   https://github.com/ARM-software/abi-aa/blob/main/ehabi32/ehabi32.rst
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __ARM_EHABI_UNWIND_H__
+#define __ARM_EHABI_UNWIND_H__
+
+typedef uint32_t _Unwind_State;
+
+static const _Unwind_State _US_VIRTUAL_UNWIND_FRAME   = 0;
+static const _Unwind_State _US_UNWIND_FRAME_STARTING  = 1;
+static const _Unwind_State _US_UNWIND_FRAME_RESUME    = 2;
+static const _Unwind_State _US_ACTION_MASK            = 3;
+/* Undocumented flag for force unwinding. */
+static const _Unwind_State _US_FORCE_UNWIND           = 8;
+
+typedef uint32_t _Unwind_EHT_Header;
+
+struct _Unwind_Control_Block;
+typedef struct _Unwind_Control_Block _Unwind_Control_Block;
+#define _Unwind_Exception _Unwind_Control_Block /* Alias */
+typedef uint8_t _Unwind_Exception_Class[8];
+
+struct _Unwind_Control_Block {
+  _Unwind_Exception_Class exception_class;
+  void (*exception_cleanup)(_Unwind_Reason_Code, _Unwind_Control_Block*);
+
+  /* Unwinder cache, private fields for the unwinder's use */
+  struct {
+    uint32_t reserved1; /* init reserved1 to 0, then don't touch */
+    uint32_t reserved2;
+    uint32_t reserved3;
+    uint32_t reserved4;
+    uint32_t reserved5;
+  } unwinder_cache;
+
+  /* Propagation barrier cache (valid after phase 1): */
+  struct {
+    uint32_t sp;
+    uint32_t bitpattern[5];
+  } barrier_cache;
+
+  /* Cleanup cache (preserved over cleanup): */
+  struct {
+    uint32_t bitpattern[4];
+  } cleanup_cache;
+
+  /* Pr cache (for pr's benefit): */
+  struct {
+    uint32_t fnstart; /* function start address */
+    _Unwind_EHT_Header* ehtp; /* pointer to EHT entry header word */
+    uint32_t additional;
+    uint32_t reserved1;
+  } pr_cache;
+
+  long long int :0; /* Enforce the 8-byte alignment */
+} __attribute__((__aligned__(8)));
+
+typedef _Unwind_Reason_Code (*_Unwind_Personality_Fn)(
+    _Unwind_State state, _Unwind_Exception *exceptionObject,
+    struct _Unwind_Context *context);
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+//
+// The following are the base functions documented by the C++ ABI
+//
+#ifdef __USING_SJLJ_EXCEPTIONS__
+extern _Unwind_Reason_Code
+    _Unwind_SjLj_RaiseException(_Unwind_Exception *exception_object);
+extern void _Unwind_SjLj_Resume(_Unwind_Exception *exception_object);
+#else
+extern _Unwind_Reason_Code
+    _Unwind_RaiseException(_Unwind_Exception *exception_object);
+extern void _Unwind_Resume(_Unwind_Exception *exception_object);
+#endif
+extern void _Unwind_DeleteException(_Unwind_Exception *exception_object);
+
+typedef enum {
+  _UVRSC_CORE = 0,  /* integer register */
+  _UVRSC_VFP = 1,   /* vfp */
+  _UVRSC_WMMXD = 3, /* Intel WMMX data register */
+  _UVRSC_WMMXC = 4, /* Intel WMMX control register */
+  _UVRSC_PSEUDO = 5 /* Special purpose pseudo register */
+} _Unwind_VRS_RegClass;
+
+typedef enum {
+  _UVRSD_UINT32 = 0,
+  _UVRSD_VFPX = 1,
+  _UVRSD_UINT64 = 3,
+  _UVRSD_FLOAT = 4,
+  _UVRSD_DOUBLE = 5
+} _Unwind_VRS_DataRepresentation;
+
+typedef enum {
+  _UVRSR_OK = 0,
+  _UVRSR_NOT_IMPLEMENTED = 1,
+  _UVRSR_FAILED = 2
+} _Unwind_VRS_Result;
+
+extern void _Unwind_Complete(_Unwind_Exception* exception_object);
+
+extern _Unwind_VRS_Result
+_Unwind_VRS_Get(_Unwind_Context *context, _Unwind_VRS_RegClass regclass,
+                uint32_t regno, _Unwind_VRS_DataRepresentation representation,
+                void *valuep);
+
+extern _Unwind_VRS_Result
+_Unwind_VRS_Set(_Unwind_Context *context, _Unwind_VRS_RegClass regclass,
+                uint32_t regno, _Unwind_VRS_DataRepresentation representation,
+                void *valuep);
+
+extern _Unwind_VRS_Result
+_Unwind_VRS_Pop(_Unwind_Context *context, _Unwind_VRS_RegClass regclass,
+                uint32_t discriminator,
+                _Unwind_VRS_DataRepresentation representation);
+
+#if defined(_LIBUNWIND_UNWIND_LEVEL1_EXTERNAL_LINKAGE)
+#define _LIBUNWIND_EXPORT_UNWIND_LEVEL1 extern
+#else
+#define _LIBUNWIND_EXPORT_UNWIND_LEVEL1 static __inline__
+#endif
+
+// These are de facto helper functions for ARM, which delegate the function
+// calls to _Unwind_VRS_Get/Set().  These are not a part of ARM EHABI
+// specification, thus these function MUST be inlined.  Please don't replace
+// these with the "extern" function declaration; otherwise, the program
+// including this <unwind.h> header won't be ABI compatible and will result in
+// link error when we are linking the program with libgcc.
+
+_LIBUNWIND_EXPORT_UNWIND_LEVEL1
+uintptr_t _Unwind_GetGR(struct _Unwind_Context *context, int index) {
+  uintptr_t value = 0;
+  _Unwind_VRS_Get(context, _UVRSC_CORE, (uint32_t)index, _UVRSD_UINT32, &value);
+  return value;
+}
+
+_LIBUNWIND_EXPORT_UNWIND_LEVEL1
+void _Unwind_SetGR(struct _Unwind_Context *context, int index,
+                   uintptr_t value) {
+  _Unwind_VRS_Set(context, _UVRSC_CORE, (uint32_t)index, _UVRSD_UINT32, &value);
+}
+
+_LIBUNWIND_EXPORT_UNWIND_LEVEL1
+uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
+  // remove the thumb-bit before returning
+  return _Unwind_GetGR(context, 15) & (~(uintptr_t)0x1);
+}
+
+_LIBUNWIND_EXPORT_UNWIND_LEVEL1
+void _Unwind_SetIP(struct _Unwind_Context *context, uintptr_t value) {
+  uintptr_t thumb_bit = _Unwind_GetGR(context, 15) & ((uintptr_t)0x1);
+  _Unwind_SetGR(context, 15, value | thumb_bit);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // __ARM_EHABI_UNWIND_H__

third_party/libunwind/include/unwind_itanium.h

@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+// C++ ABI Level 1 ABI documented at:
+//   https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __ITANIUM_UNWIND_H__
+#define __ITANIUM_UNWIND_H__
+
+struct _Unwind_Context;   // opaque
+struct _Unwind_Exception; // forward declaration
+typedef struct _Unwind_Exception _Unwind_Exception;
+typedef uint64_t _Unwind_Exception_Class;
+
+struct _Unwind_Exception {
+  _Unwind_Exception_Class exception_class;
+  void (*exception_cleanup)(_Unwind_Reason_Code reason,
+                            _Unwind_Exception *exc);
+#if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
+  uintptr_t private_[6];
+#else
+  uintptr_t private_1; // non-zero means forced unwind
+  uintptr_t private_2; // holds sp that phase1 found for phase2 to use
+#endif
+#if __SIZEOF_POINTER__ == 4
+  // The implementation of _Unwind_Exception uses an attribute mode on the
+  // above fields which has the side effect of causing this whole struct to
+  // round up to 32 bytes in size (48 with SEH). To be more explicit, we add
+  // pad fields added for binary compatibility.
+  uint32_t reserved[3];
+#endif
+  // The Itanium ABI requires that _Unwind_Exception objects are "double-word
+  // aligned".  GCC has interpreted this to mean "use the maximum useful
+  // alignment for the target"; so do we.
+} __attribute__((__aligned__));
+
+typedef _Unwind_Reason_Code (*_Unwind_Personality_Fn)(
+    int version, _Unwind_Action actions, uint64_t exceptionClass,
+    _Unwind_Exception *exceptionObject, struct _Unwind_Context *context);
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+//
+// The following are the base functions documented by the C++ ABI
+//
+#ifdef __USING_SJLJ_EXCEPTIONS__
+extern _Unwind_Reason_Code
+    _Unwind_SjLj_RaiseException(_Unwind_Exception *exception_object);
+extern void _Unwind_SjLj_Resume(_Unwind_Exception *exception_object);
+#else
+extern _Unwind_Reason_Code
+    _Unwind_RaiseException(_Unwind_Exception *exception_object);
+extern void _Unwind_Resume(_Unwind_Exception *exception_object);
+#endif
+extern void _Unwind_DeleteException(_Unwind_Exception *exception_object);
+
+
+extern uintptr_t _Unwind_GetGR(struct _Unwind_Context *context, int index);
+extern void _Unwind_SetGR(struct _Unwind_Context *context, int index,
+                          uintptr_t new_value);
+extern uintptr_t _Unwind_GetIP(struct _Unwind_Context *context);
+extern void _Unwind_SetIP(struct _Unwind_Context *, uintptr_t new_value);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // __ITANIUM_UNWIND_H__

third_party/libunwind/libunwind.cc

@@ -0,0 +1,475 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Implements unw_* functions from <libunwind.h>
+//
+//===----------------------------------------------------------------------===//
+
+#include "third_party/libunwind/include/libunwind.h"
+
+#include "third_party/libunwind/config.h"
+#include "third_party/libunwind/libunwind_ext.h"
+
+#include "libc/isystem/stdlib.h"
+
+// Define the __has_feature extension for compilers that do not support it so
+// that we can later check for the presence of ASan in a compiler-neutral way.
+#if !defined(__has_feature)
+#define __has_feature(feature) 0
+#endif
+
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+#include <sanitizer/asan_interface.h>
+#endif
+
+#if !defined(__USING_SJLJ_EXCEPTIONS__)
+#include "third_party/libunwind/AddressSpace.hpp"
+#include "third_party/libunwind/UnwindCursor.hpp"
+
+using namespace libunwind;
+
+/// internal object to represent this processes address space
+LocalAddressSpace LocalAddressSpace::sThisAddressSpace;
+
+_LIBUNWIND_EXPORT unw_addr_space_t unw_local_addr_space =
+    (unw_addr_space_t)&LocalAddressSpace::sThisAddressSpace;
+
+/// Create a cursor of a thread in this process given 'context' recorded by
+/// __unw_getcontext().
+_LIBUNWIND_HIDDEN int __unw_init_local(unw_cursor_t *cursor,
+                                       unw_context_t *context) {
+  _LIBUNWIND_TRACE_API("__unw_init_local(cursor=%p, context=%p)",
+                       static_cast<void *>(cursor),
+                       static_cast<void *>(context));
+#if defined(__i386__)
+# define REGISTER_KIND Registers_x86
+#elif defined(__x86_64__)
+# define REGISTER_KIND Registers_x86_64
+#elif defined(__powerpc64__)
+# define REGISTER_KIND Registers_ppc64
+#elif defined(__powerpc__)
+# define REGISTER_KIND Registers_ppc
+#elif defined(__aarch64__)
+# define REGISTER_KIND Registers_arm64
+#elif defined(__arm__)
+# define REGISTER_KIND Registers_arm
+#elif defined(__or1k__)
+# define REGISTER_KIND Registers_or1k
+#elif defined(__hexagon__)
+# define REGISTER_KIND Registers_hexagon
+#elif defined(__mips__) && defined(_ABIO32) && _MIPS_SIM == _ABIO32
+# define REGISTER_KIND Registers_mips_o32
+#elif defined(__mips64)
+# define REGISTER_KIND Registers_mips_newabi
+#elif defined(__mips__)
+# warning The MIPS architecture is not supported with this ABI and environment!
+#elif defined(__sparc__) && defined(__arch64__)
+#define REGISTER_KIND Registers_sparc64
+#elif defined(__sparc__)
+# define REGISTER_KIND Registers_sparc
+#elif defined(__riscv)
+# define REGISTER_KIND Registers_riscv
+#elif defined(__ve__)
+# define REGISTER_KIND Registers_ve
+#elif defined(__s390x__)
+# define REGISTER_KIND Registers_s390x
+#elif defined(__loongarch__) && __loongarch_grlen == 64
+#define REGISTER_KIND Registers_loongarch
+#else
+# error Architecture not supported
+#endif
+  // Use "placement new" to allocate UnwindCursor in the cursor buffer.
+  new (reinterpret_cast<UnwindCursor<LocalAddressSpace, REGISTER_KIND> *>(cursor))
+      UnwindCursor<LocalAddressSpace, REGISTER_KIND>(
+          context, LocalAddressSpace::sThisAddressSpace);
+#undef REGISTER_KIND
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  co->setInfoBasedOnIPRegister();
+
+  return UNW_ESUCCESS;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_init_local, unw_init_local)
+
+/// Get value of specified register at cursor position in stack frame.
+_LIBUNWIND_HIDDEN int __unw_get_reg(unw_cursor_t *cursor, unw_regnum_t regNum,
+                                    unw_word_t *value) {
+  _LIBUNWIND_TRACE_API("__unw_get_reg(cursor=%p, regNum=%d, &value=%p)",
+                       static_cast<void *>(cursor), regNum,
+                       static_cast<void *>(value));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  if (co->validReg(regNum)) {
+    *value = co->getReg(regNum);
+    return UNW_ESUCCESS;
+  }
+  return UNW_EBADREG;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_get_reg, unw_get_reg)
+
+/// Set value of specified register at cursor position in stack frame.
+_LIBUNWIND_HIDDEN int __unw_set_reg(unw_cursor_t *cursor, unw_regnum_t regNum,
+                                    unw_word_t value) {
+  _LIBUNWIND_TRACE_API("__unw_set_reg(cursor=%p, regNum=%d, value=0x%" PRIxPTR
+                       ")",
+                       static_cast<void *>(cursor), regNum, value);
+  typedef LocalAddressSpace::pint_t pint_t;
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  if (co->validReg(regNum)) {
+    co->setReg(regNum, (pint_t)value);
+    // special case altering IP to re-find info (being called by personality
+    // function)
+    if (regNum == UNW_REG_IP) {
+      unw_proc_info_t info;
+      // First, get the FDE for the old location and then update it.
+      co->getInfo(&info);
+      co->setInfoBasedOnIPRegister(false);
+      // If the original call expects stack adjustment, perform this now.
+      // Normal frame unwinding would have included the offset already in the
+      // CFA computation.
+      // Note: for PA-RISC and other platforms where the stack grows up,
+      // this should actually be - info.gp. LLVM doesn't currently support
+      // any such platforms and Clang doesn't export a macro for them.
+      if (info.gp)
+        co->setReg(UNW_REG_SP, co->getReg(UNW_REG_SP) + info.gp);
+    }
+    return UNW_ESUCCESS;
+  }
+  return UNW_EBADREG;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_set_reg, unw_set_reg)
+
+/// Get value of specified float register at cursor position in stack frame.
+_LIBUNWIND_HIDDEN int __unw_get_fpreg(unw_cursor_t *cursor, unw_regnum_t regNum,
+                                      unw_fpreg_t *value) {
+  _LIBUNWIND_TRACE_API("__unw_get_fpreg(cursor=%p, regNum=%d, &value=%p)",
+                       static_cast<void *>(cursor), regNum,
+                       static_cast<void *>(value));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  if (co->validFloatReg(regNum)) {
+    *value = co->getFloatReg(regNum);
+    return UNW_ESUCCESS;
+  }
+  return UNW_EBADREG;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_get_fpreg, unw_get_fpreg)
+
+/// Set value of specified float register at cursor position in stack frame.
+_LIBUNWIND_HIDDEN int __unw_set_fpreg(unw_cursor_t *cursor, unw_regnum_t regNum,
+                                      unw_fpreg_t value) {
+#if defined(_LIBUNWIND_ARM_EHABI)
+  _LIBUNWIND_TRACE_API("__unw_set_fpreg(cursor=%p, regNum=%d, value=%llX)",
+                       static_cast<void *>(cursor), regNum, value);
+#else
+  _LIBUNWIND_TRACE_API("__unw_set_fpreg(cursor=%p, regNum=%d, value=%g)",
+                       static_cast<void *>(cursor), regNum, value);
+#endif
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  if (co->validFloatReg(regNum)) {
+    co->setFloatReg(regNum, value);
+    return UNW_ESUCCESS;
+  }
+  return UNW_EBADREG;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_set_fpreg, unw_set_fpreg)
+
+/// Move cursor to next frame.
+_LIBUNWIND_HIDDEN int __unw_step(unw_cursor_t *cursor) {
+  _LIBUNWIND_TRACE_API("__unw_step(cursor=%p)", static_cast<void *>(cursor));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  return co->step();
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_step, unw_step)
+
+// Move cursor to next frame and for stage2 of unwinding.
+// This resets MTE tags of tagged frames to zero.
+extern "C" _LIBUNWIND_HIDDEN int __unw_step_stage2(unw_cursor_t *cursor) {
+  _LIBUNWIND_TRACE_API("__unw_step_stage2(cursor=%p)",
+                       static_cast<void *>(cursor));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  return co->step(true);
+}
+
+/// Get unwind info at cursor position in stack frame.
+_LIBUNWIND_HIDDEN int __unw_get_proc_info(unw_cursor_t *cursor,
+                                          unw_proc_info_t *info) {
+  _LIBUNWIND_TRACE_API("__unw_get_proc_info(cursor=%p, &info=%p)",
+                       static_cast<void *>(cursor), static_cast<void *>(info));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  co->getInfo(info);
+  if (info->end_ip == 0)
+    return UNW_ENOINFO;
+  return UNW_ESUCCESS;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_get_proc_info, unw_get_proc_info)
+
+/// Resume execution at cursor position (aka longjump).
+_LIBUNWIND_HIDDEN int __unw_resume(unw_cursor_t *cursor) {
+  _LIBUNWIND_TRACE_API("__unw_resume(cursor=%p)", static_cast<void *>(cursor));
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+  // Inform the ASan runtime that now might be a good time to clean stuff up.
+  __asan_handle_no_return();
+#endif
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  co->jumpto();
+  return UNW_EUNSPEC;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_resume, unw_resume)
+
+/// Get name of function at cursor position in stack frame.
+_LIBUNWIND_HIDDEN int __unw_get_proc_name(unw_cursor_t *cursor, char *buf,
+                                          size_t bufLen, unw_word_t *offset) {
+  _LIBUNWIND_TRACE_API("__unw_get_proc_name(cursor=%p, &buf=%p, bufLen=%lu)",
+                       static_cast<void *>(cursor), static_cast<void *>(buf),
+                       static_cast<unsigned long>(bufLen));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  if (co->getFunctionName(buf, bufLen, offset))
+    return UNW_ESUCCESS;
+  return UNW_EUNSPEC;
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_get_proc_name, unw_get_proc_name)
+
+/// Checks if a register is a floating-point register.
+_LIBUNWIND_HIDDEN int __unw_is_fpreg(unw_cursor_t *cursor,
+                                     unw_regnum_t regNum) {
+  _LIBUNWIND_TRACE_API("__unw_is_fpreg(cursor=%p, regNum=%d)",
+                       static_cast<void *>(cursor), regNum);
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  return co->validFloatReg(regNum);
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_is_fpreg, unw_is_fpreg)
+
+/// Checks if a register is a floating-point register.
+_LIBUNWIND_HIDDEN const char *__unw_regname(unw_cursor_t *cursor,
+                                            unw_regnum_t regNum) {
+  _LIBUNWIND_TRACE_API("__unw_regname(cursor=%p, regNum=%d)",
+                       static_cast<void *>(cursor), regNum);
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  return co->getRegisterName(regNum);
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_regname, unw_regname)
+
+/// Checks if current frame is signal trampoline.
+_LIBUNWIND_HIDDEN int __unw_is_signal_frame(unw_cursor_t *cursor) {
+  _LIBUNWIND_TRACE_API("__unw_is_signal_frame(cursor=%p)",
+                       static_cast<void *>(cursor));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  return co->isSignalFrame();
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_is_signal_frame, unw_is_signal_frame)
+
+#ifdef _AIX
+_LIBUNWIND_EXPORT uintptr_t __unw_get_data_rel_base(unw_cursor_t *cursor) {
+  _LIBUNWIND_TRACE_API("unw_get_data_rel_base(cursor=%p)",
+                       static_cast<void *>(cursor));
+  AbstractUnwindCursor *co = reinterpret_cast<AbstractUnwindCursor *>(cursor);
+  return co->getDataRelBase();
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_get_data_rel_base, unw_get_data_rel_base)
+#endif
+
+#ifdef __arm__
+// Save VFP registers d0-d15 using FSTMIADX instead of FSTMIADD
+_LIBUNWIND_HIDDEN void __unw_save_vfp_as_X(unw_cursor_t *cursor) {
+  _LIBUNWIND_TRACE_API("__unw_get_fpreg_save_vfp_as_X(cursor=%p)",
+                       static_cast<void *>(cursor));
+  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
+  return co->saveVFPAsX();
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_save_vfp_as_X, unw_save_vfp_as_X)
+#endif
+
+
+#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+/// SPI: walks cached DWARF entries
+_LIBUNWIND_HIDDEN void __unw_iterate_dwarf_unwind_cache(void (*func)(
+    unw_word_t ip_start, unw_word_t ip_end, unw_word_t fde, unw_word_t mh)) {
+  _LIBUNWIND_TRACE_API("__unw_iterate_dwarf_unwind_cache(func=%p)",
+                       reinterpret_cast<void *>(func));
+  DwarfFDECache<LocalAddressSpace>::iterateCacheEntries(func);
+}
+_LIBUNWIND_WEAK_ALIAS(__unw_iterate_dwarf_unwind_cache,
+                      unw_iterate_dwarf_unwind_cache)
+
+/// IPI: for __register_frame()
+void __unw_add_dynamic_fde(unw_word_t fde) {
+  CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
+  CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
+  const char *message = CFI_Parser<LocalAddressSpace>::decodeFDE(
+                           LocalAddressSpace::sThisAddressSpace,
+                          (LocalAddressSpace::pint_t) fde, &fdeInfo, &cieInfo);
+  if (message == NULL) {
+    // dynamically registered FDEs don't have a mach_header group they are in.
+    // Use fde as mh_group
+    unw_word_t mh_group = fdeInfo.fdeStart;
+    DwarfFDECache<LocalAddressSpace>::add((LocalAddressSpace::pint_t)mh_group,
+                                          fdeInfo.pcStart, fdeInfo.pcEnd,
+                                          fdeInfo.fdeStart);
+  } else {
+    _LIBUNWIND_DEBUG_LOG("__unw_add_dynamic_fde: bad fde: %s", message);
+  }
+}
+
+/// IPI: for __deregister_frame()
+void __unw_remove_dynamic_fde(unw_word_t fde) {
+  // fde is own mh_group
+  DwarfFDECache<LocalAddressSpace>::removeAllIn((LocalAddressSpace::pint_t)fde);
+}
+
+void __unw_add_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
+  // The eh_frame section start serves as the mh_group
+  unw_word_t mh_group = eh_frame_start;
+  CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
+  CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
+  auto p = (LocalAddressSpace::pint_t)eh_frame_start;
+  while (true) {
+    if (CFI_Parser<LocalAddressSpace>::decodeFDE(
+            LocalAddressSpace::sThisAddressSpace, p, &fdeInfo, &cieInfo,
+            true) == NULL) {
+      DwarfFDECache<LocalAddressSpace>::add((LocalAddressSpace::pint_t)mh_group,
+                                            fdeInfo.pcStart, fdeInfo.pcEnd,
+                                            fdeInfo.fdeStart);
+      p += fdeInfo.fdeLength;
+    } else if (CFI_Parser<LocalAddressSpace>::parseCIE(
+                   LocalAddressSpace::sThisAddressSpace, p, &cieInfo) == NULL) {
+      p += cieInfo.cieLength;
+    } else
+      return;
+  }
+}
+
+void __unw_remove_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
+  // The eh_frame section start serves as the mh_group
+  DwarfFDECache<LocalAddressSpace>::removeAllIn(
+      (LocalAddressSpace::pint_t)eh_frame_start);
+}
+
+#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+#endif // !defined(__USING_SJLJ_EXCEPTIONS__)
+
+#ifdef __APPLE__
+
+namespace libunwind {
+
+static constexpr size_t MAX_DYNAMIC_UNWIND_SECTIONS_FINDERS = 8;
+
+static RWMutex findDynamicUnwindSectionsLock;
+static size_t numDynamicUnwindSectionsFinders = 0;
+static unw_find_dynamic_unwind_sections
+    dynamicUnwindSectionsFinders[MAX_DYNAMIC_UNWIND_SECTIONS_FINDERS] = {0};
+
+bool findDynamicUnwindSections(void *addr, unw_dynamic_unwind_sections *info) {
+  bool found = false;
+  findDynamicUnwindSectionsLock.lock_shared();
+  for (size_t i = 0; i != numDynamicUnwindSectionsFinders; ++i) {
+    if (dynamicUnwindSectionsFinders[i]((unw_word_t)addr, info)) {
+      found = true;
+      break;
+    }
+  }
+  findDynamicUnwindSectionsLock.unlock_shared();
+  return found;
+}
+
+} // namespace libunwind
+
+int __unw_add_find_dynamic_unwind_sections(
+    unw_find_dynamic_unwind_sections find_dynamic_unwind_sections) {
+  findDynamicUnwindSectionsLock.lock();
+
+  // Check that we have enough space...
+  if (numDynamicUnwindSectionsFinders == MAX_DYNAMIC_UNWIND_SECTIONS_FINDERS) {
+    findDynamicUnwindSectionsLock.unlock();
+    return UNW_ENOMEM;
+  }
+
+  // Check for value already present...
+  for (size_t i = 0; i != numDynamicUnwindSectionsFinders; ++i) {
+    if (dynamicUnwindSectionsFinders[i] == find_dynamic_unwind_sections) {
+      findDynamicUnwindSectionsLock.unlock();
+      return UNW_EINVAL;
+    }
+  }
+
+  // Success -- add callback entry.
+  dynamicUnwindSectionsFinders[numDynamicUnwindSectionsFinders++] =
+    find_dynamic_unwind_sections;
+  findDynamicUnwindSectionsLock.unlock();
+
+  return UNW_ESUCCESS;
+}
+
+int __unw_remove_find_dynamic_unwind_sections(
+    unw_find_dynamic_unwind_sections find_dynamic_unwind_sections) {
+  findDynamicUnwindSectionsLock.lock();
+
+  // Find index to remove.
+  size_t finderIdx = numDynamicUnwindSectionsFinders;
+  for (size_t i = 0; i != numDynamicUnwindSectionsFinders; ++i) {
+    if (dynamicUnwindSectionsFinders[i] == find_dynamic_unwind_sections) {
+      finderIdx = i;
+      break;
+    }
+  }
+
+  // If no such registration is present then error out.
+  if (finderIdx == numDynamicUnwindSectionsFinders) {
+    findDynamicUnwindSectionsLock.unlock();
+    return UNW_EINVAL;
+  }
+
+  // Remove entry.
+  for (size_t i = finderIdx; i != numDynamicUnwindSectionsFinders - 1; ++i)
+    dynamicUnwindSectionsFinders[i] = dynamicUnwindSectionsFinders[i + 1];
+  dynamicUnwindSectionsFinders[--numDynamicUnwindSectionsFinders] = nullptr;
+
+  findDynamicUnwindSectionsLock.unlock();
+  return UNW_ESUCCESS;
+}
+
+#endif // __APPLE__
+
+// Add logging hooks in Debug builds only
+#ifndef NDEBUG
+#include "libc/isystem/stdlib.h"
+
+_LIBUNWIND_HIDDEN
+bool logAPIs() {
+  // do manual lock to avoid use of _cxa_guard_acquire or initializers
+  static bool checked = false;
+  static bool log = false;
+  if (!checked) {
+    log = (getenv("LIBUNWIND_PRINT_APIS") != NULL);
+    checked = true;
+  }
+  return log;
+}
+
+_LIBUNWIND_HIDDEN
+bool logUnwinding() {
+  // do manual lock to avoid use of _cxa_guard_acquire or initializers
+  static bool checked = false;
+  static bool log = false;
+  if (!checked) {
+    log = (getenv("LIBUNWIND_PRINT_UNWINDING") != NULL);
+    checked = true;
+  }
+  return log;
+}
+
+_LIBUNWIND_HIDDEN
+bool logDWARF() {
+  // do manual lock to avoid use of _cxa_guard_acquire or initializers
+  static bool checked = false;
+  static bool log = false;
+  if (!checked) {
+    log = (getenv("LIBUNWIND_PRINT_DWARF") != NULL);
+    checked = true;
+  }
+  return log;
+}
+
+#endif // NDEBUG
+

third_party/libunwind/libunwind_ext.h

@@ -0,0 +1,137 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//
+//  Extensions to libunwind API.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LIBUNWIND_EXT__
+#define __LIBUNWIND_EXT__
+
+#include "third_party/libunwind/config.h"
+#include "third_party/libunwind/include/libunwind.h"
+#include "third_party/libunwind/include/unwind.h"
+
+#define UNW_STEP_SUCCESS 1
+#define UNW_STEP_END     0
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern int __unw_getcontext(unw_context_t *);
+extern int __unw_init_local(unw_cursor_t *, unw_context_t *);
+extern int __unw_step(unw_cursor_t *);
+extern int __unw_get_reg(unw_cursor_t *, unw_regnum_t, unw_word_t *);
+extern int __unw_get_fpreg(unw_cursor_t *, unw_regnum_t, unw_fpreg_t *);
+extern int __unw_set_reg(unw_cursor_t *, unw_regnum_t, unw_word_t);
+extern int __unw_set_fpreg(unw_cursor_t *, unw_regnum_t, unw_fpreg_t);
+extern int __unw_resume(unw_cursor_t *);
+
+#ifdef __arm__
+/* Save VFP registers in FSTMX format (instead of FSTMD). */
+extern void __unw_save_vfp_as_X(unw_cursor_t *);
+#endif
+
+extern const char *__unw_regname(unw_cursor_t *, unw_regnum_t);
+extern int __unw_get_proc_info(unw_cursor_t *, unw_proc_info_t *);
+extern int __unw_is_fpreg(unw_cursor_t *, unw_regnum_t);
+extern int __unw_is_signal_frame(unw_cursor_t *);
+extern int __unw_get_proc_name(unw_cursor_t *, char *, size_t, unw_word_t *);
+
+#if defined(_AIX)
+extern uintptr_t __unw_get_data_rel_base(unw_cursor_t *);
+#endif
+
+// SPI
+extern void __unw_iterate_dwarf_unwind_cache(void (*func)(
+    unw_word_t ip_start, unw_word_t ip_end, unw_word_t fde, unw_word_t mh));
+
+// IPI
+extern void __unw_add_dynamic_fde(unw_word_t fde);
+extern void __unw_remove_dynamic_fde(unw_word_t fde);
+
+extern void __unw_add_dynamic_eh_frame_section(unw_word_t eh_frame_start);
+extern void __unw_remove_dynamic_eh_frame_section(unw_word_t eh_frame_start);
+
+#ifdef __APPLE__
+
+// Holds a description of the object-format-header (if any) and unwind info
+// sections for a given address:
+//
+// * dso_base should point to a header for the JIT'd object containing the
+//   given address. The header's type should match the format type that
+//   libunwind was compiled for (so a mach_header or mach_header_64 on Darwin).
+//   A value of zero indicates that no such header exists.
+//
+// * dwarf_section and dwarf_section_length hold the address range of a DWARF
+//   eh-frame section associated with the given address, if any. If the
+//   dwarf_section_length field is zero it indicates that no such section
+//   exists (and in this case dwarf_section should also be set to zero).
+//
+// * compact_unwind_section and compact_unwind_section_length hold the address
+//   range of a compact-unwind info section associated with the given address,
+//   if any. If the compact_unwind_section_length field is zero it indicates
+//   that no such section exists (and in this case compact_unwind_section
+//   should also be set to zero).
+//
+// See the unw_find_dynamic_unwind_sections type below for more details.
+struct unw_dynamic_unwind_sections {
+  unw_word_t dso_base;
+  unw_word_t dwarf_section;
+  size_t     dwarf_section_length;
+  unw_word_t compact_unwind_section;
+  size_t     compact_unwind_section_length;
+};
+
+// Typedef for unwind-info lookup callbacks. Functions of this type can be
+// registered and deregistered using __unw_add_find_dynamic_unwind_sections
+// and __unw_remove_find_dynamic_unwind_sections respectively.
+//
+// An unwind-info lookup callback should return 1 to indicate that it found
+// unwind-info for the given address, or 0 to indicate that it did not find
+// unwind-info for the given address. If found, the callback should populate
+// some or all of the fields of the info argument (which is guaranteed to be
+// non-null with all fields zero-initialized):
+typedef int (*unw_find_dynamic_unwind_sections)(
+    unw_word_t addr, struct unw_dynamic_unwind_sections *info);
+
+// Register a dynamic unwind-info lookup callback. If libunwind does not find
+// unwind info for a given frame in the executable program or normal dynamic
+// shared objects then it will call all registered dynamic lookup functions
+// in registration order until either one of them returns true, or the end
+// of the list is reached. This lookup will happen before libunwind searches
+// any eh-frames registered via __register_frame or
+// __unw_add_dynamic_eh_frame_section.
+//
+// Returns UNW_ESUCCESS for successful registrations. If the given callback
+// has already been registered then UNW_EINVAL will be returned. If all
+// available callback entries are in use then UNW_ENOMEM will be returned.
+extern int __unw_add_find_dynamic_unwind_sections(
+    unw_find_dynamic_unwind_sections find_dynamic_unwind_sections);
+
+// Deregister a dynacim unwind-info lookup callback.
+//
+// Returns UNW_ESUCCESS for successful deregistrations. If the given callback
+// has already been registered then UNW_EINVAL will be returned.
+extern int __unw_remove_find_dynamic_unwind_sections(
+    unw_find_dynamic_unwind_sections find_dynamic_unwind_sections);
+
+#endif
+
+#if defined(_LIBUNWIND_ARM_EHABI)
+extern const uint32_t* decode_eht_entry(const uint32_t*, size_t*, size_t*);
+extern _Unwind_Reason_Code _Unwind_VRS_Interpret(_Unwind_Context *context,
+                                                 const uint32_t *data,
+                                                 size_t offset, size_t len);
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // __LIBUNWIND_EXT__