unstrip: Handle debuginfo files with missing SHF_INFO_LINK section flags.

With GCC 5 there might be a .rela.plt section with SHF_INFO_LINK set.
Buggy binutils objdump might strip it from the section in the debug file.
Ignore such differences for relocation sections and put the flag back
if necessary.

Also improve the error message a little by only discarding the already
matched sections if there is an prelink undo section. Otherwise we will
report all sections as not matching if the file wasn't prelinked instead
of just the non-matching sections.

New testfiles generated by gcc5 and binutils objdump added.

Signed-off-by: Mark Wielaard <[email protected]>

2 files changed, 38 insertions, 5 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 632330c9..a0c32fa2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2015-07-29  Mark Wielaard  <[email protected]>
+
+	* unstrip.c (sections_flags_match): New function.
+	(sections_match): Use sections_flags_match.
+	(find_alloc_sections_prelink): Only clear matched sections if there
+	is an undo section.
+	(copy_elided_sections): Add SHF_INFO_LINK to shdr_mem.sh_flags if
+	necessary.
+
 2015-06-27  Pino Toscano  <[email protected]>
 
 	* src/strings.c: Define MAP_POPULATE if not defined already.
diff --git a/src/unstrip.c b/src/unstrip.c
index 4a8e5fa9..88330946 100644
--- a/src/unstrip.c
+++ b/src/unstrip.c
@@ -867,12 +867,28 @@ compare_symbols_output (const void *a, const void *b)
 
 #undef CMP
 
+/* Return true if the flags of the sections match, ignoring the SHF_INFO_LINK
+   flag if the section contains relocation information.  */
+static bool
+sections_flags_match (Elf64_Xword sh_flags1, Elf64_Xword sh_flags2,
+		      Elf64_Word sh_type)
+{
+  if (sh_type == SHT_REL || sh_type == SHT_RELA)
+    {
+      sh_flags1 &= ~SHF_INFO_LINK;
+      sh_flags2 &= ~SHF_INFO_LINK;
+    }
+
+  return sh_flags1 == sh_flags2;
+}
+
 /* Return true iff the flags, size, and name match.  */
 static bool
 sections_match (const struct section *sections, size_t i,
 		const GElf_Shdr *shdr, const char *name)
 {
-  return (sections[i].shdr.sh_flags == shdr->sh_flags
+  return (sections_flags_match (sections[i].shdr.sh_flags, shdr->sh_flags,
+				sections[i].shdr.sh_type)
 	  && (sections[i].shdr.sh_size == shdr->sh_size
 	      || (sections[i].shdr.sh_size < shdr->sh_size
 		  && section_can_shrink (&sections[i].shdr)))
@@ -930,10 +946,6 @@ find_alloc_sections_prelink (Elf *debug, Elf_Data *debug_shstrtab,
 			     struct section *sections,
 			     size_t nalloc, size_t nsections)
 {
-  /* Clear assignments that might have been bogus.  */
-  for (size_t i = 0; i < nalloc; ++i)
-    sections[i].outscn = NULL;
-
   Elf_Scn *undo = NULL;
   for (size_t i = nalloc; i < nsections; ++i)
     {
@@ -952,6 +964,10 @@ find_alloc_sections_prelink (Elf *debug, Elf_Data *debug_shstrtab,
   size_t undo_nalloc = 0;
   if (undo != NULL)
     {
+      /* Clear assignments that might have been bogus.  */
+      for (size_t i = 0; i < nalloc; ++i)
+	sections[i].outscn = NULL;
+
       Elf_Data *undodata = elf_rawdata (undo, NULL);
       ELF_CHECK (undodata != NULL,
 		 _("cannot read '.gnu.prelink_undo' section: %s"));
@@ -1500,6 +1516,14 @@ more sections in stripped file than debug file -- arguments reversed?"));
 	shdr_mem.sh_size = sec->shdr.sh_size;
 	shdr_mem.sh_info = sec->shdr.sh_info;
 	shdr_mem.sh_link = sec->shdr.sh_link;
+
+	/* Buggy binutils objdump might have stripped the SHF_INFO_LINK
+	   put it back if necessary.  */
+	if ((sec->shdr.sh_type == SHT_REL || sec->shdr.sh_type == SHT_RELA)
+	    && sec->shdr.sh_flags != shdr_mem.sh_flags
+	    && (sec->shdr.sh_flags & SHF_INFO_LINK) != 0)
+	  shdr_mem.sh_flags |= SHF_INFO_LINK;
+
 	if (sec->shdr.sh_link != SHN_UNDEF)
 	  shdr_mem.sh_link = ndx_section[sec->shdr.sh_link - 1];
 	if (shdr_mem.sh_flags & SHF_INFO_LINK)