Feature #4096: Follow .gnu_debuglink section.

• Status: Closed
• Assignee: -
• Target version: -

[shinh (Shinichiro Hamaji)]

=begin
浜地です。

先日取り込んでいただいた行情報のパッチですが、
ディストリビューションなんかが配布する ruby バイナリは、

debug 情報を持っていない

/usr/bin/ruby

debug 情報を持っている

debug package をインストールした場合に存在する。

/usr/lib/debug/usr/bin/ruby

とかいう感じで二つに別れています。
バグレポートする人の中には debug package を入れている人も
いるかもしれませんし、これに対応するのは一定の価値があるかもなぁ
ということで書いたパッチです。

Subject: [PATCH] Follow .gnu_debuglink section.

With this patch, a user of distribution provided ruby will see line
info if s/he has a debug package for ruby.

addr2line.c | 97 ++++++++++++++++++++++++++++++++++++++++++----------------
1 files changed, 70 insertions(+), 27 deletions(-)

diff --git a/addr2line.c b/addr2line.c
index 443333f..97bd652 100644
--- a/addr2line.c
+++ b/addr2line.c
@@ -382,14 +382,71 @@ parse_debug_line(int num_traces, void **traces,

/* read file and fill lines */
static void
-fill_lines(int num_traces, void **traces, char **syms,

• char *file, line_info_t *lines)
  

+fill_lines(int num_traces, void **traces, char **syms, int check_debuglink,

• line_info_t *current_line, line_info_t *lines);
  

+static void
+follow_debuglink(char *debuglink, int num_traces, void **traces, char **syms,

•   line_info_t *current_line, line_info_t *lines)
  

+{

• /* Ideally we should check 4 paths to follow gnu_debuglink,

•   but we handle only one case for now as this format is used
  

•   by some linux distributions. See GDB's info for detail. */
  

• static const char global_debug_dir[] = "/usr/lib/debug";
• char *p, *subdir;
• p = strrchr(binary_filename, '/');
• if (!p) {
• return;
• }
• p[1] = '\0';
• subdir = (char *)alloca(strlen(binary_filename) + 1);
• strcpy(subdir, binary_filename);
• strcpy(binary_filename, global_debug_dir);
• strncat(binary_filename, subdir,

•  PATH_MAX - strlen(binary_filename) - 1);
  

• strncat(binary_filename, debuglink,

•  PATH_MAX - strlen(binary_filename) - 1);
  

• munmap(current_line->mapped, current_line->mapped_size);
• close(current_line->fd);
• fill_lines(num_traces, traces, syms, 0, current_line, lines);
  +}

+/* read file and fill lines */
+static void
+fill_lines(int num_traces, void **traces, char **syms, int check_debuglink,

• line_info_t *current_line, line_info_t *lines)
  

{
int i;
char *shstr;
char *section_name;
ElfW(Ehdr) *ehdr;

• ElfW(Shdr) *shdr, *shstr_shdr, *debug_line_shdr = NULL;

• ElfW(Shdr) *shdr, *shstr_shdr;

• ElfW(Shdr) *debug_line_shdr = NULL, *gnu_debuglink_shdr = NULL;

• int fd;

• off_t filesize;

• char *file;

• fd = open(binary_filename, O_RDONLY);

• if (fd < 0) {

• return;

• }

• filesize = lseek(fd, 0, SEEK_END);

• lseek(fd, 0, SEEK_SET);

• /* async-signal unsafe */

• file = (char *)mmap(NULL, filesize, PROT_READ, MAP_SHARED, fd, 0);

• if (file == MAP_FAILED) {

• int e = errno;

• close(fd);

• fprintf(stderr, "mmap: %s\n", strerror(e));

• return;

• }

• current_line->fd = fd;

• current_line->mapped = file;

• current_line->mapped_size = filesize;

  for (i = 0; i < num_traces; i++) {
  const char *path;
  @@ -411,11 +468,19 @@ fill_lines(int num_traces, void **traces, char **syms,
  if (!strcmp(section_name, ".debug_line")) {
  debug_line_shdr = shdr + i;
  break;

• } else if (!strcmp(section_name, ".gnu_debuglink")) {

•  gnu_debuglink_shdr = shdr + i;
  

  }
  }

  if (!debug_line_shdr) {

• /* this file doesn't have .debug_line section */

• /* This file doesn't have .debug_line section,

• let's check .gnu_debuglink section instead. */
  

• if (gnu_debuglink_shdr && check_debuglink) {

•  follow_debuglink(file + gnu_debuglink_shdr->sh_offset,
  

•  	     num_traces, traces, syms,
  

•  	     current_line, lines);
  

• }
  return;
  }

@@ -458,12 +523,9 @@ void
rb_dump_backtrace_with_lines(int num_traces, void **trace, char **syms)
{
int i;

• int fd;
  /* async-signal unsafe */
  line_info_t *lines = (line_info_t *)calloc(num_traces,
  sizeof(line_info_t));

• off_t filesize;

• char *file;

  /* Note that line info of shared objects might not be shown
  if we don't have dl_iterate_phdr */
  @@ -491,26 +553,7 @@ rb_dump_backtrace_with_lines(int num_traces, void **trace, char **syms)
  strncpy(binary_filename, path, len);
  binary_filename[len] = '\0';

• fd = open(binary_filename, O_RDONLY);

• if (fd < 0) {

•  continue;
  

• }

• filesize = lseek(fd, 0, SEEK_END);

• lseek(fd, 0, SEEK_SET);

• /* async-signal unsafe */

• file = (char *)mmap(NULL, filesize, PROT_READ, MAP_SHARED, fd, 0);

• if (file == MAP_FAILED) {

•  int e = errno;
  

•  close(fd);
  

•  fprintf(stderr, "mmap: %s\n", strerror(e));
  

•  continue;
  

• }

• lines[i].fd = fd;

• lines[i].mapped = file;

• lines[i].mapped_size = filesize;

• fill_lines(num_traces, trace, syms, file, lines);

• fill_lines(num_traces, trace, syms, 1, &lines[i], lines);
  }

  /* fprintf may not be async-signal safe */
  --
  1.7.2.3
  =end

[naruse (Yui NARUSE)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

=begin
This issue was solved with changeset r29987.
Shinichiro, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

=end