Switch the Linux minidump writer to use MDCVInfoELF for CV data.

src/common/linux/file_id.cc

Index: src/common/linux/file_id.cc
diff --git a/src/common/linux/file_id.cc b/src/common/linux/file_id.cc
index 00b37313afd9e3814aa4ab3e567550f41dd41763..bc16fa36424a3f228479f26a6cf1d25fcd98c9f7 100644
--- a/src/common/linux/file_id.cc
+++ b/src/common/linux/file_id.cc
@@ -48,6 +48,9 @@
 
 namespace google_breakpad {
 
+// Used in a few places for backwards-compatibility.
+const size_t kMDGUIDSize = sizeof(MDGUID);
+
 FileID::FileID(const char* path) : path_(path) {}
 
 // ELF note name and desc are 32-bits word padded.
@@ -58,9 +61,12 @@ FileID::FileID(const char* path) : path_(path) {}
 
 template<typename ElfClass>
 static bool ElfClassBuildIDNoteIdentifier(const void *section, size_t length,
-                                          uint8_t identifier[kMDGUIDSize]) {
+                                          uint8_t identifier[kMaxBuildID],
+                                          size_t* identifier_length) {
   typedef typename ElfClass::Nhdr Nhdr;
 
+  assert(identifier_length);
+
   const void* section_end = reinterpret_cast<const char*>(section) + length;
   const Nhdr* note_header = reinterpret_cast<const Nhdr*>(section);
   while (reinterpret_cast<const void *>(note_header) < section_end) {
@@ -76,21 +82,26 @@ static bool ElfClassBuildIDNoteIdentifier(const void *section, size_t length,
     return false;
   }
 
-  const char* build_id = reinterpret_cast<const char*>(note_header) +
+  const uint8_t* build_id = reinterpret_cast<const uint8_t*>(note_header) +
     sizeof(Nhdr) + NOTE_PADDING(note_header->n_namesz);
   // Copy as many bits of the build ID as will fit
-  // into the GUID space.
-  my_memset(identifier, 0, kMDGUIDSize);
-  memcpy(identifier, build_id,
-         std::min(kMDGUIDSize, (size_t)note_header->n_descsz));
+  // into |identifier|. This should always fit unless someone has
+  // passed --build-id=0x... to the linker with a longer-than-standard
+  // hex string.
+  my_memset(identifier, 0, kMaxBuildID);
+  *identifier_length = std::min(kMaxBuildID, (size_t)note_header->n_descsz);
+  memcpy(identifier, build_id, *identifier_length);
 
   return true;
 }
 
 // Attempt to locate a .note.gnu.build-id section in an ELF binary
 // and copy as many bytes of it as will fit into |identifier|.
+// Set |*identifier_length| to the number of bytes copied.
 static bool FindElfBuildIDNote(const void *elf_mapped_base,
-                               uint8_t identifier[kMDGUIDSize]) {
+                               uint8_t identifier[kMaxBuildID],
+                               size_t* identifier_length) {
+  assert(identifier_length);
   void* note_section;
   size_t note_size;
   int elfclass;
@@ -105,10 +116,12 @@ static bool FindElfBuildIDNote(const void *elf_mapped_base,
 
   if (elfclass == ELFCLASS32) {
     return ElfClassBuildIDNoteIdentifier<ElfClass32>(note_section, note_size,
-                                                     identifier);
+                                                     identifier,
+                                                     identifier_length);
   } else if (elfclass == ELFCLASS64) {
     return ElfClassBuildIDNoteIdentifier<ElfClass64>(note_section, note_size,
-                                                     identifier);
+                                                     identifier,
+                                                     identifier_length);
   }
 
   return false;
@@ -117,7 +130,9 @@ static bool FindElfBuildIDNote(const void *elf_mapped_base,
 // Attempt to locate the .text section of an ELF binary and generate
 // a simple hash by XORing the first page worth of bytes into |identifier|.
 static bool HashElfTextSection(const void *elf_mapped_base,
-                               uint8_t identifier[kMDGUIDSize]) {
+                               uint8_t identifier[kMaxBuildID],
+                               size_t* identifier_length) {
+  assert(identifier_length);
   void* text_section;
   size_t text_size;
   if (!FindElfSection(elf_mapped_base, ".text", SHT_PROGBITS,
@@ -126,6 +141,8 @@ static bool HashElfTextSection(const void *elf_mapped_base,
     return false;
   }
 
+  // Only provide |kMDGUIDSize| bytes to keep identifiers produced by this
+  // function backwards-compatible.
   my_memset(identifier, 0, kMDGUIDSize);
   const uint8_t* ptr = reinterpret_cast<const uint8_t*>(text_section);
   const uint8_t* ptr_end = ptr + std::min(text_size, static_cast<size_t>(4096));
@@ -134,30 +151,34 @@ static bool HashElfTextSection(const void *elf_mapped_base,
       identifier[i] ^= ptr[i];
     ptr += kMDGUIDSize;
   }
+  *identifier_length = kMDGUIDSize;
   return true;
 }
 
 // static
 bool FileID::ElfFileIdentifierFromMappedFile(const void* base,
-                                             uint8_t identifier[kMDGUIDSize]) {
+                                             uint8_t identifier[kMaxBuildID],
+                                             size_t* identifier_length) {
   // Look for a build id note first.
-  if (FindElfBuildIDNote(base, identifier))
+  if (FindElfBuildIDNote(base, identifier, identifier_length))
     return true;
 
   // Fall back on hashing the first page of the text section.
-  return HashElfTextSection(base, identifier);
+  return HashElfTextSection(base, identifier, identifier_length);
 }
 
-bool FileID::ElfFileIdentifier(uint8_t identifier[kMDGUIDSize]) {
+bool FileID::ElfFileIdentifier(uint8_t identifier[kMaxBuildID],
+                               size_t* identifier_length) {
   MemoryMappedFile mapped_file(path_.c_str(), 0);
   if (!mapped_file.data())  // Should probably check if size >= ElfW(Ehdr)?
     return false;
 
-  return ElfFileIdentifierFromMappedFile(mapped_file.data(), identifier);
+  return ElfFileIdentifierFromMappedFile(mapped_file.data(), identifier,
+                                         identifier_length);
 }
 
 // static
-void FileID::ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],
+void FileID::ConvertIdentifierToString(const uint8_t identifier[kMaxBuildID],
                                        char* buffer, int buffer_length) {
   uint8_t identifier_swapped[kMDGUIDSize];