Linux: Check the CRC32 of the debug link file in the symbol dumper.

R=mark@chromium.org

Review URL: https://breakpad.appspot.com/1644002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1320 4c0a9323-5329-0410-9bdc-e9ce6186880e

Makefile.am

@@ -462,6 +462,7 @@ src_tools_linux_dump_syms_dump_syms_SOURCES = \
 	src/common/dwarf/bytereader.cc \
 	src/common/dwarf/dwarf2diehandler.cc \
 	src/common/dwarf/dwarf2reader.cc \
+	src/common/linux/crc32.cc \
 	src/common/linux/dump_symbols.cc \
 	src/common/linux/elf_symbols_to_module.cc \
 	src/common/linux/elfutils.cc \
@@ -510,6 +511,7 @@ src_common_dumper_unittest_SOURCES = \
 	src/common/dwarf/dwarf2reader.cc \
 	src/common/dwarf/dwarf2reader_cfi_unittest.cc \
 	src/common/dwarf/dwarf2reader_die_unittest.cc \
+	src/common/linux/crc32.cc \
 	src/common/linux/dump_symbols.cc \
 	src/common/linux/dump_symbols_unittest.cc \
 	src/common/linux/elf_core_dump.cc \
@@ -1115,6 +1117,7 @@ EXTRA_DIST = \
 	src/client/windows/sender/crash_report_sender.vcproj \
 	src/common/convert_UTF.c \
 	src/common/convert_UTF.h \
+	src/common/linux/crc32.cc \
 	src/common/linux/dump_symbols.cc \
 	src/common/linux/dump_symbols.h \
 	src/common/linux/elf_symbols_to_module.cc \

Makefile.in

@@ -610,7 +610,7 @@ am__src_common_dumper_unittest_SOURCES_DIST =  \
 	src/common/dwarf/dwarf2reader.cc \
 	src/common/dwarf/dwarf2reader_cfi_unittest.cc \
 	src/common/dwarf/dwarf2reader_die_unittest.cc \
-	src/common/linux/dump_symbols.cc \
+	src/common/linux/crc32.cc src/common/linux/dump_symbols.cc \
 	src/common/linux/dump_symbols_unittest.cc \
 	src/common/linux/elf_core_dump.cc \
 	src/common/linux/elf_core_dump_unittest.cc \
@@ -654,6 +654,7 @@ am__src_common_dumper_unittest_SOURCES_DIST =  \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/src_common_dumper_unittest-dwarf2reader.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/src_common_dumper_unittest-dwarf2reader_cfi_unittest.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/src_common_dumper_unittest-dwarf2reader_die_unittest.$(OBJEXT) \
+@DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/src_common_dumper_unittest-crc32.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/src_common_dumper_unittest-dump_symbols.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/src_common_dumper_unittest-dump_symbols_unittest.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/src_common_dumper_unittest-elf_core_dump.$(OBJEXT) \
@@ -1211,7 +1212,7 @@ am__src_tools_linux_dump_syms_dump_syms_SOURCES_DIST =  \
 	src/common/module.cc src/common/stabs_reader.cc \
 	src/common/stabs_to_module.cc src/common/dwarf/bytereader.cc \
 	src/common/dwarf/dwarf2diehandler.cc \
-	src/common/dwarf/dwarf2reader.cc \
+	src/common/dwarf/dwarf2reader.cc src/common/linux/crc32.cc \
 	src/common/linux/dump_symbols.cc \
 	src/common/linux/elf_symbols_to_module.cc \
 	src/common/linux/elfutils.cc src/common/linux/file_id.cc \
@@ -1229,6 +1230,7 @@ am__src_tools_linux_dump_syms_dump_syms_SOURCES_DIST =  \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/bytereader.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2diehandler.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2reader.$(OBJEXT) \
+@DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/crc32.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/dump_symbols.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/elf_symbols_to_module.$(OBJEXT) \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/elfutils.$(OBJEXT) \
@@ -2022,6 +2024,7 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/bytereader.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2diehandler.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2reader.cc \
+@DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/crc32.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/dump_symbols.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/elf_symbols_to_module.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/elfutils.cc \
@@ -2070,6 +2073,7 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2reader.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2reader_cfi_unittest.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/dwarf/dwarf2reader_die_unittest.cc \
+@DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/crc32.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/dump_symbols.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/dump_symbols_unittest.cc \
 @DISABLE_TOOLS_FALSE@@LINUX_HOST_TRUE@	src/common/linux/elf_core_dump.cc \
@@ -2712,6 +2716,7 @@ EXTRA_DIST = \
 	src/client/windows/sender/crash_report_sender.vcproj \
 	src/common/convert_UTF.c \
 	src/common/convert_UTF.h \
+	src/common/linux/crc32.cc \
 	src/common/linux/dump_symbols.cc \
 	src/common/linux/dump_symbols.h \
 	src/common/linux/elf_symbols_to_module.cc \
@@ -3387,6 +3392,9 @@ src/common/dwarf/src_common_dumper_unittest-dwarf2reader_cfi_unittest.$(OBJEXT):
 src/common/dwarf/src_common_dumper_unittest-dwarf2reader_die_unittest.$(OBJEXT):  \
 	src/common/dwarf/$(am__dirstamp) \
 	src/common/dwarf/$(DEPDIR)/$(am__dirstamp)
+src/common/linux/src_common_dumper_unittest-crc32.$(OBJEXT):  \
+	src/common/linux/$(am__dirstamp) \
+	src/common/linux/$(DEPDIR)/$(am__dirstamp)
 src/common/linux/src_common_dumper_unittest-dump_symbols.$(OBJEXT):  \
 	src/common/linux/$(am__dirstamp) \
 	src/common/linux/$(DEPDIR)/$(am__dirstamp)
@@ -3893,6 +3901,8 @@ src/common/dwarf/dwarf2diehandler.$(OBJEXT):  \
 src/common/dwarf/dwarf2reader.$(OBJEXT):  \
 	src/common/dwarf/$(am__dirstamp) \
 	src/common/dwarf/$(DEPDIR)/$(am__dirstamp)
+src/common/linux/crc32.$(OBJEXT): src/common/linux/$(am__dirstamp) \
+	src/common/linux/$(DEPDIR)/$(am__dirstamp)
 src/common/linux/dump_symbols.$(OBJEXT):  \
 	src/common/linux/$(am__dirstamp) \
 	src/common/linux/$(DEPDIR)/$(am__dirstamp)
@@ -4062,6 +4072,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/dwarf/$(DEPDIR)/src_common_dumper_unittest-dwarf2reader.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/dwarf/$(DEPDIR)/src_common_dumper_unittest-dwarf2reader_cfi_unittest.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/dwarf/$(DEPDIR)/src_common_dumper_unittest-dwarf2reader_die_unittest.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/crc32.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/dump_symbols.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/elf_core_dump.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/elf_symbols_to_module.Po@am__quote@
@@ -4074,6 +4085,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/safe_readlink.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-elf_core_dump.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-linux_libc_support_unittest.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/src_common_dumper_unittest-dump_symbols.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/src_common_dumper_unittest-dump_symbols_unittest.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/common/linux/$(DEPDIR)/src_common_dumper_unittest-elf_core_dump.Po@am__quote@
@@ -4978,6 +4990,20 @@ src/common/dwarf/src_common_dumper_unittest-dwarf2reader_die_unittest.obj: src/c
 @AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
 @am__fastdepCXX_FALSE@	$(AM_V_CXX@am__nodep@)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_common_dumper_unittest_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -c -o src/common/dwarf/src_common_dumper_unittest-dwarf2reader_die_unittest.obj `if test -f 'src/common/dwarf/dwarf2reader_die_unittest.cc'; then $(CYGPATH_W) 'src/common/dwarf/dwarf2reader_die_unittest.cc'; else $(CYGPATH_W) '$(srcdir)/src/common/dwarf/dwarf2reader_die_unittest.cc'; fi`
 
+src/common/linux/src_common_dumper_unittest-crc32.o: src/common/linux/crc32.cc
+@am__fastdepCXX_TRUE@	$(AM_V_CXX)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_common_dumper_unittest_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -MT src/common/linux/src_common_dumper_unittest-crc32.o -MD -MP -MF src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Tpo -c -o src/common/linux/src_common_dumper_unittest-crc32.o `test -f 'src/common/linux/crc32.cc' || echo '$(srcdir)/'`src/common/linux/crc32.cc
+@am__fastdepCXX_TRUE@	$(AM_V_at)$(am__mv) src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Tpo src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Po
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	$(AM_V_CXX)source='src/common/linux/crc32.cc' object='src/common/linux/src_common_dumper_unittest-crc32.o' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCXX_FALSE@	$(AM_V_CXX@am__nodep@)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_common_dumper_unittest_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -c -o src/common/linux/src_common_dumper_unittest-crc32.o `test -f 'src/common/linux/crc32.cc' || echo '$(srcdir)/'`src/common/linux/crc32.cc
+
+src/common/linux/src_common_dumper_unittest-crc32.obj: src/common/linux/crc32.cc
+@am__fastdepCXX_TRUE@	$(AM_V_CXX)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_common_dumper_unittest_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -MT src/common/linux/src_common_dumper_unittest-crc32.obj -MD -MP -MF src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Tpo -c -o src/common/linux/src_common_dumper_unittest-crc32.obj `if test -f 'src/common/linux/crc32.cc'; then $(CYGPATH_W) 'src/common/linux/crc32.cc'; else $(CYGPATH_W) '$(srcdir)/src/common/linux/crc32.cc'; fi`
+@am__fastdepCXX_TRUE@	$(AM_V_at)$(am__mv) src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Tpo src/common/linux/$(DEPDIR)/src_common_dumper_unittest-crc32.Po
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	$(AM_V_CXX)source='src/common/linux/crc32.cc' object='src/common/linux/src_common_dumper_unittest-crc32.obj' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCXX_FALSE@	$(AM_V_CXX@am__nodep@)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_common_dumper_unittest_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -c -o src/common/linux/src_common_dumper_unittest-crc32.obj `if test -f 'src/common/linux/crc32.cc'; then $(CYGPATH_W) 'src/common/linux/crc32.cc'; else $(CYGPATH_W) '$(srcdir)/src/common/linux/crc32.cc'; fi`
+
 src/common/linux/src_common_dumper_unittest-dump_symbols.o: src/common/linux/dump_symbols.cc
 @am__fastdepCXX_TRUE@	$(AM_V_CXX)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_common_dumper_unittest_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -MT src/common/linux/src_common_dumper_unittest-dump_symbols.o -MD -MP -MF src/common/linux/$(DEPDIR)/src_common_dumper_unittest-dump_symbols.Tpo -c -o src/common/linux/src_common_dumper_unittest-dump_symbols.o `test -f 'src/common/linux/dump_symbols.cc' || echo '$(srcdir)/'`src/common/linux/dump_symbols.cc
 @am__fastdepCXX_TRUE@	$(AM_V_at)$(am__mv) src/common/linux/$(DEPDIR)/src_common_dumper_unittest-dump_symbols.Tpo src/common/linux/$(DEPDIR)/src_common_dumper_unittest-dump_symbols.Po

src/common/linux/crc32.cc

@@ -0,0 +1,70 @@
+// Copyright 2014 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
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "common/linux/crc32.h"
+
+namespace google_breakpad {
+
+// This implementation is based on the sample implementation in RFC 1952.
+
+// CRC32 polynomial, in reversed form.
+// See RFC 1952, or http://en.wikipedia.org/wiki/Cyclic_redundancy_check
+static const uint32_t kCrc32Polynomial = 0xEDB88320;
+static uint32_t kCrc32Table[256] = { 0 };
+
+#define arraysize(f) (sizeof(f) / sizeof(*f))
+
+static void EnsureCrc32TableInited() {
+  if (kCrc32Table[arraysize(kCrc32Table) - 1])
+    return;  // already inited
+  for (uint32_t i = 0; i < arraysize(kCrc32Table); ++i) {
+    uint32_t c = i;
+    for (size_t j = 0; j < 8; ++j) {
+      if (c & 1) {
+        c = kCrc32Polynomial ^ (c >> 1);
+      } else {
+        c >>= 1;
+      }
+    }
+    kCrc32Table[i] = c;
+  }
+}
+
+uint32_t UpdateCrc32(uint32_t start, const void* buf, size_t len) {
+  EnsureCrc32TableInited();
+
+  uint32_t c = start ^ 0xFFFFFFFF;
+  const uint8_t* u = static_cast<const uint8_t*>(buf);
+  for (size_t i = 0; i < len; ++i) {
+    c = kCrc32Table[(c ^ u[i]) & 0xFF] ^ (c >> 8);
+  }
+  return c ^ 0xFFFFFFFF;
+}
+
+}  // namespace google_breakpad

src/common/linux/crc32.h

@@ -0,0 +1,53 @@
+// Copyright 2014 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
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef COMMON_LINUX_CRC32_H_
+#define COMMON_LINUX_CRC32_H_
+
+#include <stdint.h>
+
+#include <string>
+
+namespace google_breakpad {
+
+// Updates a CRC32 checksum with |len| bytes from |buf|. |initial| holds the
+// checksum result from the previous update; for the first call, it should be 0.
+uint32_t UpdateCrc32(uint32_t initial, const void* buf, size_t len);
+
+// Computes a CRC32 checksum using |len| bytes from |buf|.
+inline uint32_t ComputeCrc32(const void* buf, size_t len) {
+  return UpdateCrc32(0, buf, len);
+}
+inline uint32_t ComputeCrc32(const std::string& str) {
+  return ComputeCrc32(str.c_str(), str.size());
+}
+
+}  // namespace google_breakpad
+
+#endif  // COMMON_LINUX_CRC32_H_

src/common/linux/dump_symbols.cc

@@ -57,6 +57,8 @@
 #include "common/dwarf_cfi_to_module.h"
 #include "common/dwarf_cu_to_module.h"
 #include "common/dwarf_line_to_module.h"
+#include "common/linux/crc32.h"
+#include "common/linux/eintr_wrapper.h"
 #include "common/linux/elfutils.h"
 #include "common/linux/elfutils-inl.h"
 #include "common/linux/elf_symbols_to_module.h"
@@ -141,7 +143,7 @@ class MmapWrapper {
 
  private:
   bool is_set_;
-  void *base_;
+  void* base_;
   size_t size_;
 };
 
@@ -204,8 +206,8 @@ class DumperLineToModule: public DwarfCUToModule::LineToModuleHandler {
   void StartCompilationUnit(const string& compilation_dir) {
     compilation_dir_ = compilation_dir;
   }
-  void ReadProgram(const char *program, uint64 length,
+  void ReadProgram(const char* program, uint64 length,
-                   Module *module, std::vector<Module::Line> *lines) {
+                   Module* module, std::vector<Module::Line>* lines) {
     DwarfLineToModule handler(module, compilation_dir_, lines);
     dwarf2reader::LineInfo parser(program, length, byte_reader_, &handler);
     parser.Start();
@@ -369,7 +371,7 @@ bool LoadELF(const string& obj_file, MmapWrapper* map_wrapper,
             obj_file.c_str(), strerror(errno));
     return false;
   }
-  void *obj_base = mmap(NULL, st.st_size,
+  void* obj_base = mmap(NULL, st.st_size,
                         PROT_READ | PROT_WRITE, MAP_PRIVATE, obj_fd, 0);
   if (obj_base == MAP_FAILED) {
     fprintf(stderr, "Failed to mmap ELF file '%s': %s\n",
@@ -405,19 +407,19 @@ bool ElfEndianness(const typename ElfClass::Ehdr* elf_header,
 
 // Read the .gnu_debuglink and get the debug file name. If anything goes
 // wrong, return an empty string.
-template<typename ElfClass>
 string ReadDebugLink(const char* debuglink,
-                     size_t debuglink_size,
+                     const size_t debuglink_size,
+                     const bool big_endian,
                      const string& obj_file,
                      const std::vector<string>& debug_dirs) {
-  size_t debuglink_len = strlen(debuglink) + 5;  // '\0' + CRC32.
+  size_t debuglink_len = strlen(debuglink) + 5;  // Include '\0' + CRC32.
-  debuglink_len = 4 * ((debuglink_len + 3) / 4);  // Round to nearest 4 bytes.
+  debuglink_len = 4 * ((debuglink_len + 3) / 4);  // Round up to 4 bytes.
 
   // Sanity check.
   if (debuglink_len != debuglink_size) {
     fprintf(stderr, "Mismatched .gnu_debuglink string / section size: "
             "%zx %zx\n", debuglink_len, debuglink_size);
-    return "";
+    return string();
   }
 
   bool found = false;
@@ -428,10 +430,39 @@ string ReadDebugLink(const char* debuglink,
     const string& debug_dir = *it;
     debuglink_path = debug_dir + "/" + debuglink;
     debuglink_fd = open(debuglink_path.c_str(), O_RDONLY);
-    if (debuglink_fd >= 0) {
+    if (debuglink_fd < 0)
-      found = true;
+      continue;
-      break;
+
+    FDWrapper debuglink_fd_wrapper(debuglink_fd);
+
+    // The CRC is the last 4 bytes in |debuglink|.
+    const dwarf2reader::Endianness endianness = big_endian ?
+        dwarf2reader::ENDIANNESS_BIG : dwarf2reader::ENDIANNESS_LITTLE;
+    dwarf2reader::ByteReader byte_reader(endianness);
+    uint32_t expected_crc =
+        byte_reader.ReadFourBytes(&debuglink[debuglink_size - 4]);
+
+    uint32_t actual_crc = 0;
+    while (true) {
+      const size_t kReadSize = 4096;
+      char buf[kReadSize];
+      ssize_t bytes_read = HANDLE_EINTR(read(debuglink_fd, &buf, kReadSize));
+      if (bytes_read < 0) {
+        fprintf(stderr, "Error reading debug ELF file %s.\n",
+                debuglink_path.c_str());
+        return string();
+      }
+      if (bytes_read == 0)
+        break;
+      actual_crc = google_breakpad::UpdateCrc32(actual_crc, buf, bytes_read);
     }
+    if (actual_crc != expected_crc) {
+      fprintf(stderr, "Error reading debug ELF file - CRC32 mismatch: %s\n",
+              debuglink_path.c_str());
+      continue;
+    }
+    found = true;
+    break;
   }
 
   if (!found) {
@@ -441,13 +472,9 @@ string ReadDebugLink(const char* debuglink,
       const string debug_dir = *it;
       fprintf(stderr, "  %s/%s\n", debug_dir.c_str(), debuglink);
     }
-    return "";
+    return string();
   }
 
-  FDWrapper debuglink_fd_wrapper(debuglink_fd);
-  // TODO(thestig) check the CRC-32 at the end of the .gnu_debuglink
-  // section.
-
   return debuglink_path;
 }
 
@@ -657,10 +684,12 @@ bool LoadSymbols(const string& obj_file,
           const char* debuglink_contents =
               GetOffset<ElfClass, char>(elf_header,
                                         gnu_debuglink_section->sh_offset);
-          string debuglink_file
+          string debuglink_file =
-              = ReadDebugLink<ElfClass>(debuglink_contents,
+              ReadDebugLink(debuglink_contents,
-                                        gnu_debuglink_section->sh_size,
+                            gnu_debuglink_section->sh_size,
-                                        obj_file, info->debug_dirs());
+                            big_endian,
+                            obj_file,
+                            info->debug_dirs());
           info->set_debuglink_file(debuglink_file);
         } else {
           fprintf(stderr, ".gnu_debuglink section found in '%s', "
@@ -759,7 +788,7 @@ string FormatIdentifier(unsigned char identifier[16]) {
 // last slash, or the whole filename if there are no slashes.
 string BaseFileName(const string &filename) {
   // Lots of copies!  basename's behavior is less than ideal.
-  char *c_filename = strdup(filename.c_str());
+  char* c_filename = strdup(filename.c_str());
   string base = basename(c_filename);
   free(c_filename);
   return base;