Prefer to use .note.gnu.build-id section as ElfBuildId

Summary:
Android prefers `.note.gnu-build-id`[0] as BuildId than anyother PT_NOTE
phdrs. This CL tries to read ElfBuildId from `.note.gnu.build-id` first
to fix the BuildId mismatch issue between Android tombstone report and
breakpad symbol file.

e.g
```
Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .note.androi[...] NOTE             0000000000000270  00000270
       0000000000000018  0000000000000000   A       0     0     4
  [ 2] .note.hwasan[...] NOTE             0000000000000288  00000288
       000000000000001c  0000000000000000   A       0     0     4
  [ 3] .note.gnu.bu[...] NOTE             00000000000002a4  000002a4
       0000000000000020  0000000000000000   A       0     0     4

$ readelf -x .note.hwasan.globals
Hex dump of section '.note.hwasan.globals':
  0x00000288 08000000 08000000 03000000 4c4c564d ............LLVM
  0x00000298 00000000 98890100 409d0100          ........@...

$ readelf -x .note.gnu.build-id
Hex dump of section '.note.gnu.build-id':
  0x000002a4 04000000 10000000 03000000 474e5500 ............GNU.
  0x000002b4 a4eb3625 c1db6452 1e881973 bfdff9bd ..6%..dR...s....
```

The BuildId in tombstone:
```
libartbase.so (BuildId: c7e463b51b0898d442269a421353bdbd)
```

But the breakpad dump_syms got:
```
MODULE Linux arm64 000189989D40000100000000000000000 libartbase.so
INFO CODE_ID 98890100409D0100
`````

[0]
https://cs.android.com/android/platform/superproject/main/+/main:system/unwinding/libunwindstack/ElfInterface.cpp;l=423-427;drc=3d19fbcc09b1b44928639b06cd0b88f735cd988d

Change-Id: I01e3514e0e2a1ea163c03093055284448ed4e89c
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/5463566
Reviewed-by: Joshua Peraza <jperaza@chromium.org>

2 files changed, 46 insertions, 7 deletions

diff --git a/src/common/linux/file_id.cc b/src/common/linux/file_id.cc
index d8fcbd8d..29653160 100644
--- a/src/common/linux/file_id.cc
+++ b/src/common/linux/file_id.cc
@@ -99,6 +99,13 @@ 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) {
+  void* note_section;
+  size_t note_size;
+  if (FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,
+                     (const void**)&note_section, &note_size)) {
+    return ElfClassBuildIDNoteIdentifier(note_section, note_size, identifier);
+  }
+
   PageAllocator allocator;
   // lld normally creates 2 PT_NOTEs, gold normally creates 1.
   auto_wasteful_vector<ElfSegment, 2> segs(&allocator);
@@ -110,13 +117,6 @@ static bool FindElfBuildIDNote(const void* elf_mapped_base,
     }
   }
 
-  void* note_section;
-  size_t note_size;
-  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 false;
 }
 
diff --git a/src/common/linux/file_id_unittest.cc b/src/common/linux/file_id_unittest.cc
index 0ef45353..7be239f6 100644
--- a/src/common/linux/file_id_unittest.cc
+++ b/src/common/linux/file_id_unittest.cc
@@ -326,6 +326,45 @@ TYPED_TEST(FileIDTest, BuildIDMultiplePH) {
   EXPECT_EQ(expected_identifier_string, identifier_string);
 }
 
+TYPED_TEST(FileIDTest, BuildIDMultiplePHPreferGNU) {
+  const uint8_t kExpectedIdentifierBytes[] =
+    {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+     0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
+     0x10, 0x11, 0x12, 0x13};
+  const string expected_identifier_string =
+      this->get_file_id(kExpectedIdentifierBytes);
+
+  ELF elf(EM_386, TypeParam::kClass, kLittleEndian);
+  Section text(kLittleEndian);
+  text.Append(4096, 0);
+  elf.AddSection(".text", text, SHT_PROGBITS);
+  Notes notes1(kLittleEndian);
+  notes1.AddNote(0, "Linux",
+                reinterpret_cast<const uint8_t*>("\0x42\0x02\0\0"), 4);
+  Notes notes2(kLittleEndian);
+  notes2.AddNote(NT_GNU_BUILD_ID, "GNU",
+                reinterpret_cast<const uint8_t*>("\0x42\0x02\0\0"), 4);
+  Notes notes3(kLittleEndian);
+  notes3.AddNote(NT_GNU_BUILD_ID, "GNU", kExpectedIdentifierBytes,
+                 sizeof(kExpectedIdentifierBytes));
+  int note1_idx = elf.AddSection(".note1", notes1, SHT_NOTE);
+  int note2_idx = elf.AddSection(".note2", notes2, SHT_NOTE);
+  int note3_idx = elf.AddSection(".note.gnu.build-id", notes3, SHT_NOTE);
+  elf.AddSegment(note1_idx, note1_idx, PT_NOTE);
+  elf.AddSegment(note2_idx, note2_idx, PT_NOTE);
+  elf.AddSegment(note3_idx, note3_idx, PT_NOTE);
+  elf.Finish();
+  this->GetElfContents(elf);
+
+  id_vector identifier(this->make_vector());
+  EXPECT_TRUE(FileID::ElfFileIdentifierFromMappedFile(this->elfdata,
+                                                      identifier));
+  EXPECT_EQ(sizeof(kExpectedIdentifierBytes), identifier.size());
+
+  string identifier_string = FileID::ConvertIdentifierToUUIDString(identifier);
+  EXPECT_EQ(expected_identifier_string, identifier_string);
+}
+
 // Test to make sure two files with different text sections produce
 // different hashes when not using a build id.
 TYPED_TEST(FileIDTest, UniqueHashes) {