Improve debug binary location detection

2025-05-23 05:42:29 +00:00 · 2023-11-16 23:26:05 -08:00 · 2023-11-16 23:26:05 -08:00 · 7a9e176ecf
commit 7a9e176ecf
parent 68c7c9c1e0
17 changed files with 92 additions and 50 deletions
--- a/libc/calls/finddebugbinary.c
+++ b/libc/calls/finddebugbinary.c
@ -0,0 +1,130 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "ape/sections.internal.h"
+#include "libc/atomic.h"
+#include "libc/calls/blockcancel.internal.h"
+#include "libc/calls/calls.h"
+#include "libc/calls/syscall-sysv.internal.h"
+#include "libc/cosmo.h"
+#include "libc/dce.h"
+#include "libc/elf/def.h"
+#include "libc/elf/tinyelf.internal.h"
+#include "libc/errno.h"
+#include "libc/intrin/bits.h"
+#include "libc/intrin/directmap.internal.h"
+#include "libc/nt/memory.h"
+#include "libc/nt/runtime.h"
+#include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/prot.h"
+
+static struct {
+  atomic_uint once;
+  const char *res;
+  char buf[PATH_MAX];
+} g_comdbg;
+
+static const char *kDbgExts[] = {
+    ".dbg",
+    ".com.dbg",
+#ifdef __aarch64__
+    ".aarch64.elf",
+#elif defined(__powerpc64__)
+    ".ppc64.elf",
+#endif
+};
+
+static int GetElfMachine(void) {
+#ifdef __x86_64__
+  return EM_NEXGEN32E;
+#elif defined(__aarch64__)
+  return EM_AARCH64;
+#elif defined(__powerpc64__)
+  return EM_PPC64;
+#elif defined(__riscv)
+  return EM_RISCV;
+#elif defined(__s390x__)
+  return EM_S390;
+#else
+#error "unsupported architecture"
+#endif
+}
+
+static bool IsMyDebugBinary(const char *path) {
+  int64_t size;
+  uintptr_t value;
+  bool res = false;
+  int fd, e = errno;
+  struct DirectMap dm;
+  BLOCK_CANCELATION;
+  if ((fd = open(path, O_RDONLY | O_CLOEXEC, 0)) != -1) {
+    // sanity test that this .com.dbg file (1) is an elf image, and (2)
+    // contains the same number of bytes of code as our .com executable
+    // which is currently running in memory.
+    if ((size = lseek(fd, 0, SEEK_END)) != -1 &&
+        (dm = sys_mmap(0, size, PROT_READ, MAP_SHARED, fd, 0)).addr !=
+            MAP_FAILED) {
+      if (READ32LE((char *)dm.addr) == READ32LE("\177ELF") &&
+          ((Elf64_Ehdr *)dm.addr)->e_machine == GetElfMachine() &&
+          GetElfSymbolValue(dm.addr, "_etext", &value)) {
+        res = !_etext || value == (uintptr_t)_etext;
+      }
+      if (!IsWindows()) {
+        sys_munmap(dm.addr, size);
+      } else {
+        CloseHandle(dm.maphandle);
+        UnmapViewOfFile(dm.addr);
+      }
+    }
+    close(fd);
+  }
+  ALLOW_CANCELATION;
+  errno = e;
+  return res;
+}
+
+static void FindDebugBinaryInit(void) {
+  const char *comdbg;
+  if ((comdbg = getenv("COMDBG")) && IsMyDebugBinary(comdbg)) {
+    g_comdbg.res = comdbg;
+    return;
+  }
+  char *prog = GetProgramExecutableName();
+  for (int i = 0; i < ARRAYLEN(kDbgExts); ++i) {
+    strlcpy(g_comdbg.buf, prog, sizeof(g_comdbg.buf));
+    strlcat(g_comdbg.buf, kDbgExts[i], sizeof(g_comdbg.buf));
+    if (IsMyDebugBinary(g_comdbg.buf)) {
+      g_comdbg.res = g_comdbg.buf;
+      return;
+    }
+  }
+  g_comdbg.res = prog;
+}
+
+/**
+ * Returns path of binary with the debug information, or null.
+ *
+ * @return path to debug binary, or NULL
+ */
+const char *FindDebugBinary(void) {
+  cosmo_once(&g_comdbg.once, FindDebugBinaryInit);
+  return g_comdbg.res;
+}