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

src/common/linux/file_id.h

 // Copyright (c) 2006, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
 #ifndef COMMON_LINUX_FILE_ID_H__
 #define COMMON_LINUX_FILE_ID_H__
 
 #include <limits.h>
 #include <string>
 
 #include "common/linux/guid_creator.h"
 
 namespace google_breakpad {
 
-static const size_t kMDGUIDSize = sizeof(MDGUID);
+// This is somewhat arbitrary, but GNU binutils' ld defaults to
+// 'sha1', which is 160 bits == 20 bytes, so this is enough to fit
+// that, which most binaries will use.
+const size_t kMaxBuildID = 20;

[Lei Zhang, 2016/02/10 23:08:50]

In src/client/linux/microdump_writer/microdump_writer.cc:346, we have:

uint8_t identifier_bytes[kMaxBuildID];
my_memcpy(&identifier_bytes, identifier, sizeof(MDGUID));

Can we static_assert(kMaxBuildID >= sizeof(MDGUID), "kMaxBuildID too small") ?

 
 class FileID {
  public:
   explicit FileID(const char* path);
   ~FileID() {}
 
   // Load the identifier for the elf file path specified in the constructor into
-  // |identifier|.  Return false if the identifier could not be created for the
+  // |identifier|.  Set |identifier_length| to the length of the identifier in
+  // bytes.  Return false if the identifier could not be created for this
   // file.
   // The current implementation will look for a .note.gnu.build-id
   // section and use that as the file id, otherwise it falls back to
   // XORing the first 4096 bytes of the .text section to generate an identifier.
-  bool ElfFileIdentifier(uint8_t identifier[kMDGUIDSize]);
+  bool ElfFileIdentifier(uint8_t identifier[kMaxBuildID],
+                         size_t* identifier_length);
 
   // Load the identifier for the elf file mapped into memory at |base| into
-  // |identifier|.  Return false if the identifier could not be created for the
+  // |identifier|.  Set |identifier_length| to the length of the identifier in
+  // bytes.  Return false if the identifier could not be created for this
   // file.
   static bool ElfFileIdentifierFromMappedFile(const void* base,
-                                              uint8_t identifier[kMDGUIDSize]);
+                                              uint8_t identifier[kMaxBuildID],
+                                              size_t* identifier_length);
 
   // Convert the |identifier| data to a NULL terminated string.  The string will
   // be formatted as a UUID (e.g., 22F065BB-FC9C-49F7-80FE-26A7CEBD7BCE).
   // The |buffer| should be at least 37 bytes long to receive all of the data
   // and termination.  Shorter buffers will contain truncated data.
-  static void ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],
+  static void ConvertIdentifierToString(const uint8_t identifier[kMaxBuildID],
                                         char* buffer, int buffer_length);
 
  private:
   // Storage for the path specified
   std::string path_;
 };
 
 }  // namespace google_breakpad
 
 #endif  // COMMON_LINUX_FILE_ID_H__