[PATCH] Add "build_id" to struct bfd_preserve

[Bhushan Attarde <bhushan dot attarde at imgtec dot com>]

  Currently the "build_id" field of "struct bfd" is not preserved by
"struct bfd_preserve" when "bfd_check_format_matches" is going through all
target vectors trying to find a compatible target vector. This leads to a
segmentation fault in GDB.

  Consider a case where one compatible target vector has already been found (so
the subset of bfd state is saved in struct bfd_preserve) and then an attempt to
find a better match fails after it has modified bfd's build_id pointer. Since
this attempt is failed, all its side effects will be undone and all memory
allocations done by this vector will be free'd. This will eventually free the
memory block that build_id pointer is pointing to. This free'd block then gets
reallocated and used for storing something else -- leaving build_id pointing to
incorrect contents.

 This patch adds "build_id" pointer to "struct bfd_preserve" so that it will be
preserved on success which can then be recoverable on failure.

bfd/ChangeLog:

	* format.c (struct bfd_preserve): New "build_id" field.
	(bfd_preserve_save): Save "build_id".
	(bfd_preserve_restore): Restore "build_id".
---
 bfd/format.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/bfd/format.c b/bfd/format.c
index f34b1d4..459aa54 100644
--- a/bfd/format.c
+++ b/bfd/format.c
@@ -104,6 +104,7 @@ struct bfd_preserve
   struct bfd_section *section_last;
   unsigned int section_count;
   struct bfd_hash_table section_htab;
+  const struct bfd_build_id *build_id;
 };
 
 /* When testing an object for compatibility with a particular target
@@ -125,6 +126,7 @@ bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve)
   preserve->section_last = abfd->section_last;
   preserve->section_count = abfd->section_count;
   preserve->section_htab = abfd->section_htab;
+  preserve->build_id = abfd->build_id;
   preserve->marker = bfd_alloc (abfd, 1);
   if (preserve->marker == NULL)
     return FALSE;
@@ -158,6 +160,7 @@ bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
   abfd->sections = preserve->sections;
   abfd->section_last = preserve->section_last;
   abfd->section_count = preserve->section_count;
+  abfd->build_id = preserve->build_id;
 
   /* bfd_release frees all memory more recently bfd_alloc'd than
      its arg, as well as its arg.  */
-- 
1.9-rc2