Teach the ELF parser to handle multiple PT_NOTE phdrs.

It is legal for an ELF to contain multiple PT_NOTEs, and that is in
fact what lld's output looks like.

Testing: "make check" and breakpad_unittests when patched into
chromium.

Bug: chromium:716484
Change-Id: I01d3f8679961e2cb7e789d4007de8914c6af357d
Reviewed-on: https://chromium-review.googlesource.com/513512
Reviewed-by: Primiano Tucci <primiano@chromium.org>
Reviewed-by: Ted Mielczarek <ted@mielczarek.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

1 files changed, 15 insertions, 8 deletions

diff --git a/src/common/linux/file_id.cc b/src/common/linux/file_id.cc
index 728f0bc8..67921c45 100644
--- a/src/common/linux/file_id.cc
+++ b/src/common/linux/file_id.cc
@@ -95,18 +95,25 @@ static bool ElfClassBuildIDNoteIdentifier(const void *section, size_t length,
 // and copy it into |identifier|.
 static bool FindElfBuildIDNote(const void* elf_mapped_base,
                                wasteful_vector<uint8_t>& identifier) {
+  PageAllocator allocator;
+  // lld normally creates 2 PT_NOTEs, gold normally creates 1.
+  auto_wasteful_vector<ElfSegment, 2> segs(&allocator);
+  if (FindElfSegments(elf_mapped_base, PT_NOTE, &segs)) {
+    for (ElfSegment& seg : segs) {
+      if (ElfClassBuildIDNoteIdentifier(seg.start, seg.size, identifier)) {
+        return true;
+      }
+    }
+  }
+
   void* note_section;
   size_t note_size;
-  if ((!FindElfSegment(elf_mapped_base, PT_NOTE,
-                       (const void**)&note_section, &note_size) ||
-      note_size == 0)  &&
-      (!FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,
-                       (const void**)&note_section, &note_size) ||
-      note_size == 0)) {
-    return false;
+  if (FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,
+                     (const void**)&note_section, &note_size)) {
+    return ElfClassBuildIDNoteIdentifier(note_section, note_size, identifier);
   }
 
-  return ElfClassBuildIDNoteIdentifier(note_section, note_size, identifier);
+  return false;
 }
 
 // Attempt to locate the .text section of an ELF binary and generate