third_party: Add libunwind (#1053)

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

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