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Look for build-id-based separate debug files under the sysroot 

When looking for a separate debug file that matches a given build-id,
GDB only looks in the host's debug dir (typically /usr/lib/debug).  This
patch makes it look in the sysroot as well.  This is to match the
behavior of GDB when using debuglink-based separate debug files,
introduced in :

402d2bfec4 ("Look for separate debug files in debug directories under a sysroot.")

In the following example, my sysroot is "/tmp/sysroot" and I am trying
to load symbols for
/tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so.  This is
the current behavior:

    (gdb) file /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so
    Reading symbols from /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so...

    Looking for separate debug info (build-id) for /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so
      Trying /usr/lib/debug/.build-id/f3/d6594d2600e985812cd4ba2ad083ac2aceae22.debug... no, unable to compute real path

    <snip>
    (No debugging symbols found in /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so)

With this patch:

    (gdb) file /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so
    Reading symbols from /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so...

    Looking for separate debug info (build-id) for /tmp/sysroot/usr/lib/arm-linux-gnueabihf/gconv/EBCDIC-AT-DE.so
      Trying /usr/lib/debug/.build-id/f3/d6594d2600e985812cd4ba2ad083ac2aceae22.debug... no, unable to compute real path
      Trying /tmp/sysroot/usr/lib/debug/.build-id/f3/d6594d2600e985812cd4ba2ad083ac2aceae22.debug... yes!
    Reading symbols from /tmp/sysroot/usr/lib/debug/.build-id/f3/d6594d2600e985812cd4ba2ad083ac2aceae22.debug...

In the original code, there is a suspicious "abfd.release ()" in
build_id_to_debug_bfd, that I don't understand.  If a file with the
right name exists but its build-id note doesn't match, we release (leak)
our reference, meaning the file will stay open?  I removed it in the new
code, so that the reference is dropped if we end up not using that file.
I tested briefly by corrupting a separate debug file to trigger this
code, nothing exploded.

gdb/ChangeLog:

	* build-id.c (build_id_to_debug_bfd_1): New function.
	(build_id_to_debug_bfd): Look for separate debug file in
	sysroot.
This commit is contained in:
Simon Marchi 2019-02-22 15:09:23 -05:00 committed by Simon Marchi
parent c6f4a5d0ed
commit 07bc701d03
2 changed files with 80 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
gdb/ChangeLog
View File

@ -1,3 +1,9 @@
2019-02-22 Simon Marchi <simon.marchi@polymtl.ca>
* build-id.c (build_id_to_debug_bfd_1): New function.
(build_id_to_debug_bfd): Look for separate debug file in
sysroot.
2019-02-22 Andrew Burgess <andrew.burgess@embecosm.com>
* gdbarch.sh: Update the copyright year range that is placed into

119
gdb/build-id.c
View File

@ -65,13 +65,63 @@ build_id_verify (bfd *abfd, size_t check_len, const bfd_byte *check)
return retval;
}
/* Helper for build_id_to_debug_bfd. LINK is a path to a potential
build-id-based separate debug file, potentially a symlink to the real file.
If the file exists and matches BUILD_ID, return a BFD reference to it. */
static gdb_bfd_ref_ptr
build_id_to_debug_bfd_1 (const std::string &link, size_t build_id_len,
const bfd_byte *build_id)
{
if (separate_debug_file_debug)
{
printf_unfiltered (_(" Trying %s..."), link.c_str ());
gdb_flush (gdb_stdout);
}
/* lrealpath() is expensive even for the usually non-existent files. */
gdb::unique_xmalloc_ptr<char> filename;
if (access (link.c_str (), F_OK) == 0)
filename.reset (lrealpath (link.c_str ()));
if (filename == NULL)
{
if (separate_debug_file_debug)
printf_unfiltered (_(" no, unable to compute real path\n"));
return {};
}
/* We expect to be silent on the non-existing files. */
gdb_bfd_ref_ptr debug_bfd = gdb_bfd_open (filename.get (), gnutarget, -1);
if (debug_bfd == NULL)
{
if (separate_debug_file_debug)
printf_unfiltered (_(" no, unable to open.\n"));
return {};
}
if (!build_id_verify (debug_bfd.get(), build_id_len, build_id))
{
if (separate_debug_file_debug)
printf_unfiltered (_(" no, build-id does not match.\n"));
return {};
}
if (separate_debug_file_debug)
printf_unfiltered (_(" yes!\n"));
return debug_bfd;
}
/* See build-id.h. */
gdb_bfd_ref_ptr
build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
{
gdb_bfd_ref_ptr abfd;
/* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will
cause "/.build-id/..." lookups. */
@ -83,6 +133,10 @@ build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
const gdb_byte *data = build_id;
size_t size = build_id_len;
/* Compute where the file named after the build-id would be.
If debugdir is "/usr/lib/debug" and the build-id is abcdef, this will
give "/usr/lib/debug/.build-id/ab/cdef.debug". */
std::string link = debugdir.get ();
link += "/.build-id/";
@ -97,53 +151,28 @@ build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
link += ".debug";
if (separate_debug_file_debug)
gdb_bfd_ref_ptr debug_bfd
= build_id_to_debug_bfd_1 (link, build_id_len, build_id);
if (debug_bfd != NULL)
return debug_bfd;
/* Try to look under the sysroot as well. If the sysroot is
"/the/sysroot", it will give
"/the/sysroot/usr/lib/debug/.build-id/ab/cdef.debug".
Don't do it if the sysroot is the target system ("target:"). It
could work in theory, but the lrealpath in build_id_to_debug_bfd_1
only works with local paths. */
if (strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) != 0)
{
printf_unfiltered (_(" Trying %s..."), link.c_str ());
gdb_flush (gdb_stdout);
link = gdb_sysroot + link;
debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
if (debug_bfd != NULL)
return debug_bfd;
}
/* lrealpath() is expensive even for the usually non-existent files. */
gdb::unique_xmalloc_ptr<char> filename;
if (access (link.c_str (), F_OK) == 0)
filename.reset (lrealpath (link.c_str ()));
if (filename == NULL)
{
if (separate_debug_file_debug)
printf_unfiltered (_(" no, unable to compute real path\n"));
continue;
}
/* We expect to be silent on the non-existing files. */
abfd = gdb_bfd_open (filename.get (), gnutarget, -1);
if (abfd == NULL)
{
if (separate_debug_file_debug)
printf_unfiltered (_(" no, unable to open.\n"));
continue;
}
if (build_id_verify (abfd.get(), build_id_len, build_id))
{
if (separate_debug_file_debug)
printf_unfiltered (_(" yes!\n"));
break;
}
else
{
if (separate_debug_file_debug)
printf_unfiltered (_(" no, build-id does not match.\n"));
}
abfd.release ();
}
return abfd;
return {};
}
/* See build-id.h. */