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

This preserves full build ids in minidumps, which are useful for
tracking down the right version of system libraries from Linux
distributions.

The default build id produced by GNU binutils' ld is a 160-bit SHA-1
hash of some parts of the binary, which is exactly 20 bytes:
https://sourceware.org/binutils/docs-2.26/ld/Options.html#index-g_t_002d_002dbuild_002did-292

The bulk of the changes here are to change the signatures of the
FileID methods to use a wasteful_vector instead of raw pointers, since
build ids can be of arbitrary length.

The previous change that added support for this in the processor code
preserved the return value of `Minidump::debug_identifier()` as the
current `GUID+age` treatment for backwards-compatibility, and exposed
the full build id from `Minidump::code_identifier()`, which was
previously stubbed out for Linux dumps. This change keeps the debug ID
in the `dump_syms` output the same to match.

R=mark@chromium.org, thestig@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1688743002 .

1 files changed, 13 insertions, 23 deletions

diff --git a/src/common/linux/dump_symbols.cc b/src/common/linux/dump_symbols.cc
index 5d2aac7e..d31e2c2d 100644
--- a/src/common/linux/dump_symbols.cc
+++ b/src/common/linux/dump_symbols.cc
@@ -64,6 +64,7 @@
 #include "common/linux/elfutils-inl.h"
 #include "common/linux/elf_symbols_to_module.h"
 #include "common/linux/file_id.h"
+#include "common/memory.h"
 #include "common/module.h"
 #include "common/scoped_ptr.h"
 #ifndef NO_STABS_SUPPORT
@@ -82,14 +83,18 @@ using google_breakpad::DwarfLineToModule;
 using google_breakpad::ElfClass;
 using google_breakpad::ElfClass32;
 using google_breakpad::ElfClass64;
+using google_breakpad::FileID;
 using google_breakpad::FindElfSectionByName;
 using google_breakpad::GetOffset;
 using google_breakpad::IsValidElf;
+using google_breakpad::kDefaultBuildIdSize;
 using google_breakpad::Module;
+using google_breakpad::PageAllocator;
 #ifndef NO_STABS_SUPPORT
 using google_breakpad::StabsToModule;
 #endif
 using google_breakpad::scoped_ptr;
+using google_breakpad::wasteful_vector;
 
 // Define AARCH64 ELF architecture if host machine does not include this define.
 #ifndef EM_AARCH64
@@ -854,25 +859,6 @@ const char* ElfArchitecture(const typename ElfClass::Ehdr* elf_header) {
   }
 }
 
-// Format the Elf file identifier in IDENTIFIER as a UUID with the
-// dashes removed.
-string FormatIdentifier(unsigned char identifier[16]) {
-  char identifier_str[40];
-  google_breakpad::FileID::ConvertIdentifierToString(
-      identifier,
-      identifier_str,
-      sizeof(identifier_str));
-  string id_no_dash;
-  for (int i = 0; identifier_str[i] != '\0'; ++i)
-    if (identifier_str[i] != '-')
-      id_no_dash += identifier_str[i];
-  // Add an extra "0" by the end.  PDB files on Windows have an 'age'
-  // number appended to the end of the file identifier; this isn't
-  // really used or necessary on other platforms, but be consistent.
-  id_no_dash += '0';
-  return id_no_dash;
-}
-
 // Return the non-directory portion of FILENAME: the portion after the
 // last slash, or the whole filename if there are no slashes.
 string BaseFileName(const string &filename) {
@@ -924,9 +910,10 @@ bool ReadSymbolDataElfClass(const typename ElfClass::Ehdr* elf_header,
 
   *out_module = NULL;
 
-  unsigned char identifier[16];
-  if (!google_breakpad::FileID::ElfFileIdentifierFromMappedFile(elf_header,
-                                                                identifier)) {
+  PageAllocator allocator;
+  wasteful_vector<uint8_t> identifier(&allocator, kDefaultBuildIdSize);
+  if (!FileID::ElfFileIdentifierFromMappedFile(elf_header,
+                                               identifier)) {
     fprintf(stderr, "%s: unable to generate file identifier\n",
             obj_filename.c_str());
     return false;
@@ -946,7 +933,10 @@ bool ReadSymbolDataElfClass(const typename ElfClass::Ehdr* elf_header,
 
   string name = BaseFileName(obj_filename);
   string os = "Linux";
-  string id = FormatIdentifier(identifier);
+  // Add an extra "0" at the end.  PDB files on Windows have an 'age'
+  // number appended to the end of the file identifier; this isn't
+  // really used or necessary on other platforms, but be consistent.
+  string id = FileID::ConvertIdentifierToUUIDString(identifier) + "0";
 
   LoadSymbolsInfo<ElfClass> info(debug_dirs);
   scoped_ptr<Module> module(new Module(name, os, architecture, id));