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, 52 insertions, 35 deletions

diff --git a/src/client/linux/minidump_writer/minidump_writer_unittest.cc b/src/client/linux/minidump_writer/minidump_writer_unittest.cc
index e1046e12..db7d4f5d 100644
--- a/src/client/linux/minidump_writer/minidump_writer_unittest.cc
+++ b/src/client/linux/minidump_writer/minidump_writer_unittest.cc
@@ -54,10 +54,6 @@
 
 using namespace google_breakpad;
 
-// Length of a formatted GUID string =
-// sizeof(MDGUID) * 2 + 4 (for dashes) + 1 (null terminator)
-const int kGUIDStringSize = 37;
-
 namespace {
 
 typedef testing::Test MinidumpWriterTest;
@@ -137,19 +133,7 @@ TEST(MinidumpWriterTest, MappingInfo) {
     0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
     0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF
   };
-  char module_identifier_buffer[kGUIDStringSize];
-  FileID::ConvertIdentifierToString(kModuleGUID,
-                                    module_identifier_buffer,
-                                    sizeof(module_identifier_buffer));
-  string module_identifier(module_identifier_buffer);
-  // Strip out dashes
-  size_t pos;
-  while ((pos = module_identifier.find('-')) != string::npos) {
-    module_identifier.erase(pos, 1);
-  }
-  // And append a zero, because module IDs include an "age" field
-  // which is always zero on Linux.
-  module_identifier += "0";
+  const string module_identifier = "33221100554477668899AABBCCDDEEFF0";
 
   // Get some memory.
   char* memory =
@@ -230,6 +214,53 @@ TEST(MinidumpWriterTest, MappingInfo) {
   close(fds[1]);
 }
 
+// Test that a binary with a longer-than-usual build id note
+// makes its way all the way through to the minidump unscathed.
+// The linux_client_unittest is linked with an explicit --build-id
+// in Makefile.am.
+TEST(MinidumpWriterTest, BuildIDLong) {
+  int fds[2];
+  ASSERT_NE(-1, pipe(fds));
+
+  const pid_t child = fork();
+  if (child == 0) {
+    close(fds[1]);
+    char b;
+    IGNORE_RET(HANDLE_EINTR(read(fds[0], &b, sizeof(b))));
+    close(fds[0]);
+    syscall(__NR_exit);
+  }
+  close(fds[0]);
+
+  ExceptionHandler::CrashContext context;
+  memset(&context, 0, sizeof(context));
+  ASSERT_EQ(0, getcontext(&context.context));
+  context.tid = child;
+
+  AutoTempDir temp_dir;
+  const string dump_path = temp_dir.path() + kMDWriterUnitTestFileName;
+
+  EXPECT_TRUE(WriteMinidump(dump_path.c_str(),
+                            child, &context, sizeof(context)));
+  close(fds[1]);
+
+  // Read the minidump. Load the module list, and ensure that
+  // the main module has the correct debug id and code id.
+  Minidump minidump(dump_path);
+  ASSERT_TRUE(minidump.Read());
+
+  MinidumpModuleList* module_list = minidump.GetModuleList();
+  ASSERT_TRUE(module_list);
+  const MinidumpModule* module = module_list->GetMainModule();
+  ASSERT_TRUE(module);
+  const string module_identifier = "030201000504070608090A0B0C0D0E0F0";
+  // This is passed explicitly to the linker in Makefile.am
+  const string build_id =
+      "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f";
+  EXPECT_EQ(module_identifier, module->debug_identifier());
+  EXPECT_EQ(build_id, module->code_identifier());
+}
+
 // Test that mapping info can be specified, and that it overrides
 // existing mappings that are wholly contained within the specified
 // range.
@@ -245,19 +276,7 @@ TEST(MinidumpWriterTest, MappingInfoContained) {
     0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
     0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF
   };
-  char module_identifier_buffer[kGUIDStringSize];
-  FileID::ConvertIdentifierToString(kModuleGUID,
-                                    module_identifier_buffer,
-                                    sizeof(module_identifier_buffer));
-  string module_identifier(module_identifier_buffer);
-  // Strip out dashes
-  size_t pos;
-  while ((pos = module_identifier.find('-')) != string::npos) {
-    module_identifier.erase(pos, 1);
-  }
-  // And append a zero, because module IDs include an "age" field
-  // which is always zero on Linux.
-  module_identifier += "0";
+  const string module_identifier = "33221100554477668899AABBCCDDEEFF0";
 
   // mmap a file
   AutoTempDir temp_dir;
@@ -410,12 +429,10 @@ TEST(MinidumpWriterTest, DeletedBinary) {
   EXPECT_STREQ(binpath.c_str(), module->code_file().c_str());
   // Check that the file ID is correct.
   FileID fileid(helper_path.c_str());
-  uint8_t identifier[sizeof(MDGUID)];
+  PageAllocator allocator;
+  wasteful_vector<uint8_t> identifier(&allocator, kDefaultBuildIdSize);
   EXPECT_TRUE(fileid.ElfFileIdentifier(identifier));
-  char identifier_string[kGUIDStringSize];
-  FileID::ConvertIdentifierToString(identifier,
-                                    identifier_string,
-                                    kGUIDStringSize);
+  string identifier_string = FileID::ConvertIdentifierToUUIDString(identifier);
   string module_identifier(identifier_string);
   // Strip out dashes
   size_t pos;