| Summary: | Files in .gnu_debugaltlink should be resolved relative to .debug file, not symlink. | ||
|---|---|---|---|
| Product: | [Developer tools] valgrind | Reporter: | Mark Wielaard <mark> |
| Component: | general | Assignee: | Julian Seward <jseward> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | ||
| Priority: | NOR | ||
| Version First Reported In: | 3.14 SVN | ||
| Target Milestone: | --- | ||
| Platform: | Other | ||
| OS: | Linux | ||
| Latest Commit: | Version Fixed In: | ||
| Sentry Crash Report: | |||
| Attachments: | Fix gnu debug alt file resolving. | ||
commit be82bb5f9dfecd854c53eda321d1914f28f19790 Author: Mark Wielaard <mark@klomp.org> Date: Sat Dec 9 23:01:29 2017 +0100 Fix gnu debug alt file resolving. https://bugs.kde.org/show_bug.cgi?id=387773 The path to the alt file is relative to the actual debug file. Make sure that we got the real file, not a (build-id) symlink. Also handle the case where a debug or alt file is an absolute path. This is still not completely correct. If the symlink itself contains a relative path then we need to add the symlink dir before it. Something like the following:
diff --git a/coregrind/m_debuginfo/readelf.c b/coregrind/m_debuginfo/readelf.c
index c19ff212b..70c28e629 100644
--- a/coregrind/m_debuginfo/readelf.c
+++ b/coregrind/m_debuginfo/readelf.c
@@ -1582,6 +1582,24 @@ static HChar* readlink_path (const HChar *path)
return NULL;
}
+ if (buf[0] == '/')
+ return buf;
+
+ /* Relative path, add link dir. */
+ HChar *linkdirptr;
+ SizeT linkdir_len = VG_(strlen)(path);
+ if ((linkdirptr = VG_(strrchr)(path, '/')) != NULL)
+ linkdir_len -= VG_(strlen)(linkdirptr + 1);
+
+ SizeT buflen = VG_(strlen)(buf);
+ SizeT needed = linkdir_len + buflen + 1;
+ if (bufsiz < needed)
+ buf = ML_(dinfo_realloc)("readlink_path.linkdir", buf, needed);
+
+ VG_(memmove)(buf + linkdir_len, buf, buflen);
+ VG_(memcpy)(buf, path, linkdir_len);
+ buf[needed - 1] = '\0';
+
return buf;
}
Tested additional fix in Fedora and committed now as commit 7d0403032250c8985ae99a96af7bcd9190ad654b Author: Mark Wielaard <mark@klomp.org> Date: Sat Jan 13 14:33:50 2018 +0100 Additional fix for gnu debug alt file resolving. Also handle the case where the symlink itself contains a relative path. Then we need to add the symlink dir before it. https://bugs.kde.org/show_bug.cgi?id=387773 |
Created attachment 109296 [details] Fix gnu debug alt file resolving. In some situations (Fedora 27) the .debug file is available through a build-id symlink, but the debug alt file isn't (which arguably isn't ideal, and probably should be fixed). In such cases resolving the debug alt file from the relative path in the .gnu_debugaltlink should be done against the actual .debug file, not against the (build-id) symlink that pointed to the .debug file. This causes issues like: $ valgrind -q /usr/libexec/pcp/bin/telnet-probe --17775-- WARNING: Serious error when reading debug info --17775-- When reading debug info from /usr/libexec/pcp/bin/telnet-probe: --17775-- get_Form_contents: DW_FORM_GNU_strp_alt used, but no alternate .debug_str This is caused because the relative debug alt file path is resolved against the build-id symlink file, instead of against the actual .debug file. /usr/lib/debug/.build-id/87/1a7e7175751df1a2017ef448e5ebf390270c6f.debug -> ../../../../../usr/lib/debug/usr/libexec/pcp/bin/telnet-probe-3.12.1-3.fc27.x86_64.debug The attached patch fixes this by making sure that the file against which any relative paths are resolved isn't a symlink.