allow passing info about known memory mappings to MinidumpWriter and ExceptionHandler

r=thestig at http://breakpad.appspot.com/242001/show

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@741 4c0a9323-5329-0410-9bdc-e9ce6186880e

10 files changed, 616 insertions, 77 deletions

diff --git a/src/client/linux/handler/exception_handler.cc b/src/client/linux/handler/exception_handler.cc
index 592c9e5b..4c7436ea 100644
--- a/src/client/linux/handler/exception_handler.cc
+++ b/src/client/linux/handler/exception_handler.cc
@@ -88,10 +88,12 @@
 #include <unistd.h>
 
 #include <algorithm>
+#include <utility>
 #include <vector>
 
 #include "common/linux/linux_libc_support.h"
 #include "common/memory.h"
+#include "client/linux/minidump_writer/linux_dumper.h"
 #include "client/linux/minidump_writer/minidump_writer.h"
 #include "common/linux/guid_creator.h"
 #include "common/linux/eintr_wrapper.h"
@@ -449,8 +451,11 @@ void ExceptionHandler::WaitForContinueSignal() {
 // Runs on the cloned process.
 bool ExceptionHandler::DoDump(pid_t crashing_process, const void* context,
                               size_t context_size) {
-  return google_breakpad::WriteMinidump(
-      next_minidump_path_c_, crashing_process, context, context_size);
+  return google_breakpad::WriteMinidump(next_minidump_path_c_,
+                                        crashing_process,
+                                        context,
+                                        context_size,
+                                        mapping_list_);
 }
 
 // static
@@ -482,4 +487,21 @@ bool ExceptionHandler::WriteMinidump() {
 #endif  // !defined(__ARM_EABI__)
 }
 
+void ExceptionHandler::AddMappingInfo(const std::string& name,
+                                      const u_int8_t identifier[sizeof(MDGUID)],
+                                      uintptr_t start_address,
+                                      size_t mapping_size,
+                                      size_t file_offset) {
+  MappingInfo info;
+  info.start_addr = start_address;
+  info.size = mapping_size;
+  info.offset = file_offset;
+  strncpy(info.name, name.c_str(), std::min(name.size(), sizeof(info)));
+
+  MappingEntry mapping;
+  mapping.first = info;
+  memcpy(mapping.second, identifier, sizeof(MDGUID));
+  mapping_list_.push_back(mapping);
+}
+
 }  // namespace google_breakpad
diff --git a/src/client/linux/handler/exception_handler.h b/src/client/linux/handler/exception_handler.h
index 82f7fb4c..e75517ea 100644
--- a/src/client/linux/handler/exception_handler.h
+++ b/src/client/linux/handler/exception_handler.h
@@ -30,17 +30,20 @@
 #ifndef CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
 #define CLIENT_LINUX_HANDLER_EXCEPTION_HANDLER_H_
 
-#include <vector>
 #include <string>
+#include <vector>
 
 #include <pthread.h>
 #include <signal.h>
+#include <stdint.h>
 #include <stdio.h>
 
 #if defined(__ANDROID__)
 #include "client/linux/android_ucontext.h"
 #endif
 #include "client/linux/crash_generation/crash_generation_client.h"
+#include "client/linux/minidump_writer/minidump_writer.h"
+#include "google_breakpad/common/minidump_format.h"
 #include "processor/scoped_ptr.h"
 
 struct sigaction;
@@ -181,6 +184,15 @@ class ExceptionHandler {
       return crash_generation_client_.get() != NULL;
   }
 
+  // Add information about a memory mapping. This can be used if
+  // a custom library loader is used that maps things in a way
+  // that the linux dumper can't handle by reading the maps file.
+  void AddMappingInfo(const std::string& name,
+                      const u_int8_t identifier[sizeof(MDGUID)],
+                      uintptr_t start_address,
+                      size_t mapping_size,
+                      size_t file_offset);
+
  private:
   void Init(const std::string &dump_path,
             const int server_fd);
@@ -236,6 +248,10 @@ class ExceptionHandler {
   // cloned process after creating it, until we have explicitly enabled 
   // ptrace. This is used to store the file descriptors for the pipe
   int fdes[2];
+
+  // Callers can add extra info about mappings for cases where the
+  // dumper code cannot extract enough information from /proc/<pid>/maps.
+  MappingList mapping_list_;
 };
 
 }  // namespace google_breakpad
diff --git a/src/client/linux/handler/exception_handler_unittest.cc b/src/client/linux/handler/exception_handler_unittest.cc
index 988de063..67c05f6b 100644
--- a/src/client/linux/handler/exception_handler_unittest.cc
+++ b/src/client/linux/handler/exception_handler_unittest.cc
@@ -42,6 +42,7 @@
 #include "client/linux/handler/exception_handler.h"
 #include "client/linux/minidump_writer/minidump_writer.h"
 #include "common/linux/eintr_wrapper.h"
+#include "common/linux/file_id.h"
 #include "common/linux/linux_libc_support.h"
 #include "third_party/lss/linux_syscall_support.h"
 #include "google_breakpad/processor/minidump.h"
@@ -54,6 +55,10 @@ using namespace google_breakpad;
 #define TEMPDIR "/data/local/tmp"
 #endif
 
+// Length of a formatted GUID string =
+// sizeof(MDGUID) * 2 + 4 (for dashes) + 1 (null terminator)
+const int kGUIDStringSize = 37;
+
 static void sigchld_handler(int signo) { }
 
 class ExceptionHandlerTest : public ::testing::Test {
@@ -573,6 +578,87 @@ TEST(ExceptionHandlerTest, InstructionPointerMemoryNullPointer) {
   free(filename);
 }
 
+static bool SimpleCallback(const char* dump_path,
+                           const char* minidump_id,
+                           void* context,
+                           bool succeeded) {
+  if (!succeeded)
+    return succeeded;
+
+  string* minidump_file = reinterpret_cast<string*>(context);
+  minidump_file->append(dump_path);
+  minidump_file->append("/");
+  minidump_file->append(minidump_id);
+  minidump_file->append(".dmp");
+  return true;
+}
+
+// Test that anonymous memory maps can be annotated with names and IDs.
+TEST(ExceptionHandlerTest, ModuleInfo) {
+  // These are defined here so the parent can use them to check the
+  // data from the minidump afterwards.
+  const u_int32_t kMemorySize = sysconf(_SC_PAGESIZE);
+  const char* kMemoryName = "a fake module";
+  const u_int8_t kModuleGUID[sizeof(MDGUID)] = {
+    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";
+
+  // Get some memory.
+  char* memory =
+    reinterpret_cast<char*>(mmap(NULL,
+                                 kMemorySize,
+                                 PROT_READ | PROT_WRITE,
+                                 MAP_PRIVATE | MAP_ANON,
+                                 -1,
+                                 0));
+  const u_int64_t kMemoryAddress = reinterpret_cast<u_int64_t>(memory);
+  ASSERT_TRUE(memory);
+
+  string minidump_filename;
+  ExceptionHandler handler(TEMPDIR, NULL, SimpleCallback,
+                           (void*)&minidump_filename, true);
+  // Add info about the anonymous memory mapping.
+  handler.AddMappingInfo(kMemoryName,
+                         kModuleGUID,
+                         kMemoryAddress,
+                         kMemorySize,
+                         0);
+  handler.WriteMinidump();
+
+  // Read the minidump. Load the module list, and ensure that
+  // the mmap'ed |memory| is listed with the given module name
+  // and debug ID.
+  Minidump minidump(minidump_filename);
+  ASSERT_TRUE(minidump.Read());
+
+  MinidumpModuleList* module_list = minidump.GetModuleList();
+  ASSERT_TRUE(module_list);
+  const MinidumpModule* module =
+    module_list->GetModuleForAddress(kMemoryAddress);
+  ASSERT_TRUE(module);
+
+  EXPECT_EQ(kMemoryAddress, module->base_address());
+  EXPECT_EQ(kMemorySize, module->size());
+  EXPECT_EQ(kMemoryName, module->code_file());
+  EXPECT_EQ(module_identifier, module->debug_identifier());
+
+  unlink(minidump_filename.c_str());
+}
+
 static const unsigned kControlMsgSize =
     CMSG_SPACE(sizeof(int)) + CMSG_SPACE(sizeof(struct ucred));
 
diff --git a/src/client/linux/minidump_writer/linux_dumper.cc b/src/client/linux/minidump_writer/linux_dumper.cc
index 6e6f4cfa..5187120f 100644
--- a/src/client/linux/minidump_writer/linux_dumper.cc
+++ b/src/client/linux/minidump_writer/linux_dumper.cc
@@ -104,12 +104,12 @@ static bool ResumeThread(pid_t pid) {
 }
 
 inline static bool IsMappedFileOpenUnsafe(
-    const google_breakpad::MappingInfo* mapping) {
+    const google_breakpad::MappingInfo& mapping) {
   // It is unsafe to attempt to open a mapped file that lives under /dev,
   // because the semantics of the open may be driver-specific so we'd risk
   // hanging the crash dumper. And a file in /dev/ almost certainly has no
   // ELF file identifier anyways.
-  return my_strncmp(mapping->name,
+  return my_strncmp(mapping.name,
                     kMappedFileUnsafePrefix,
                     sizeof(kMappedFileUnsafePrefix) - 1) == 0;
 }
@@ -203,21 +203,21 @@ LinuxDumper::BuildProcPath(char* path, pid_t pid, const char* node) const {
 }
 
 bool
-LinuxDumper::ElfFileIdentifierForMapping(unsigned int mapping_id,
+LinuxDumper::ElfFileIdentifierForMapping(const MappingInfo& mapping,
+                                         unsigned int mapping_id,
                                          uint8_t identifier[sizeof(MDGUID)])
 {
-  assert(mapping_id < mappings_.size());
+  assert(mapping_id == -1 || mapping_id < mappings_.size());
   my_memset(identifier, 0, sizeof(MDGUID));
-  MappingInfo* mapping = mappings_[mapping_id];
   if (IsMappedFileOpenUnsafe(mapping))
     return false;
 
   char filename[NAME_MAX];
-  size_t filename_len = my_strlen(mapping->name);
+  size_t filename_len = my_strlen(mapping.name);
   assert(filename_len < NAME_MAX);
   if (filename_len >= NAME_MAX)
     return false;
-  memcpy(filename, mapping->name, filename_len);
+  memcpy(filename, mapping.name, filename_len);
   filename[filename_len] = '\0';
   bool filename_modified = HandleDeletedFileInMapping(filename);
 
@@ -239,8 +239,11 @@ LinuxDumper::ElfFileIdentifierForMapping(unsigned int mapping_id,
 
   bool success = FileID::ElfFileIdentifierFromMappedFile(base, identifier);
   sys_munmap(base, st.st_size);
-  if (success && filename_modified)
-    mapping->name[filename_len - sizeof(kDeletedSuffix) + 1] = '\0';
+  if (success && mapping_id != -1 && filename_modified) {
+    mappings_[mapping_id]->name[filename_len -
+                                sizeof(kDeletedSuffix) + 1] = '\0';
+  }
+
   return success;
 }
 
@@ -310,7 +313,7 @@ LinuxDumper::EnumerateMappings(wasteful_vector<MappingInfo*>* result) const {
           module->offset = offset;
           const char* name = NULL;
           // Only copy name if the name is a valid path name, or if
-          // we've found the VDSO image
+          // it's the VDSO image.
           if ((name = my_strchr(line, '/')) != NULL) {
             const unsigned l = my_strlen(name);
             if (l < sizeof(module->name))
@@ -500,7 +503,7 @@ const MappingInfo* LinuxDumper::FindMapping(const void* address) const {
   return NULL;
 }
 
-bool LinuxDumper::HandleDeletedFileInMapping(char* path) {
+bool LinuxDumper::HandleDeletedFileInMapping(char* path) const {
   static const size_t kDeletedSuffixLen = sizeof(kDeletedSuffix) - 1;
 
   // Check for ' (deleted)' in |path|.
diff --git a/src/client/linux/minidump_writer/linux_dumper.h b/src/client/linux/minidump_writer/linux_dumper.h
index 16b15f3c..2233ec05 100644
--- a/src/client/linux/minidump_writer/linux_dumper.h
+++ b/src/client/linux/minidump_writer/linux_dumper.h
@@ -151,8 +151,10 @@ class LinuxDumper {
   // without any slashes.
   void BuildProcPath(char* path, pid_t pid, const char* node) const;
 
-  // Generate a File ID from the .text section of a mapped entry
-  bool ElfFileIdentifierForMapping(unsigned int mapping_id,
+  // Generate a File ID from the .text section of a mapped entry.
+  // mapping_id may be -1 if this is not a member of mappings_.
+  bool ElfFileIdentifierForMapping(const MappingInfo& mapping,
+                                   unsigned int mapping_id,
                                    uint8_t identifier[sizeof(MDGUID)]);
 
   // Utility method to find the location of where the kernel has
@@ -174,7 +176,7 @@ class LinuxDumper {
   // For programs that don't end with ' (deleted)', this is a no-op.
   // This assumes |path| is a buffer with length NAME_MAX.
   // Returns true if |path| is modified.
-  bool HandleDeletedFileInMapping(char* path);
+  bool HandleDeletedFileInMapping(char* path) const;
 
   const pid_t pid_;
 
diff --git a/src/client/linux/minidump_writer/linux_dumper_unittest.cc b/src/client/linux/minidump_writer/linux_dumper_unittest.cc
index b81291b6..a3e84dbc 100644
--- a/src/client/linux/minidump_writer/linux_dumper_unittest.cc
+++ b/src/client/linux/minidump_writer/linux_dumper_unittest.cc
@@ -32,26 +32,19 @@
 #include <limits.h>
 #include <unistd.h>
 #include <signal.h>
+#include <stdint.h>
+#include <sys/poll.h>
 #include <sys/types.h>
 
 #include "breakpad_googletest_includes.h"
 #include "client/linux/minidump_writer/linux_dumper.h"
+#include "common/linux/eintr_wrapper.h"
 #include "common/linux/file_id.h"
 #include "common/memory.h"
 
 using std::string;
 using namespace google_breakpad;
 
-// This provides a wrapper around system calls which may be
-// interrupted by a signal and return EINTR. See man 7 signal.
-#define HANDLE_EINTR(x) ({ \
-  typeof(x) __eintr_result__; \
-  do { \
-    __eintr_result__ = x; \
-  } while (__eintr_result__ == -1 && errno == EINTR); \
-  __eintr_result__;\
-})
-
 namespace {
 typedef testing::Test LinuxDumperTest;
 }
@@ -88,8 +81,14 @@ TEST(LinuxDumperTest, VerifyStackReadWithMultipleThreads) {
   char kNumberOfThreadsArgument[2];
   sprintf(kNumberOfThreadsArgument, "%d", kNumberOfThreadsInHelperProgram);
 
+  int fds[2];
+  ASSERT_NE(-1, pipe(fds));
+
   pid_t child_pid = fork();
   if (child_pid == 0) {
+    // In child process.
+    close(fds[0]);
+
     // Locate helper binary next to the current binary.
     char self_path[PATH_MAX];
     if (readlink("/proc/self/exe", self_path, sizeof(self_path) - 1) == -1) {
@@ -105,9 +104,12 @@ TEST(LinuxDumperTest, VerifyStackReadWithMultipleThreads) {
     helper_path.erase(pos + 1);
     helper_path += "linux_dumper_unittest_helper";
 
-    // Set the number of threads
+    // Pass the pipe fd and the number of threads as arguments.
+    char pipe_fd_string[8];
+    sprintf(pipe_fd_string, "%d", fds[1]);
     execl(helper_path.c_str(),
           "linux_dumper_unittest_helper",
+          pipe_fd_string,
           kNumberOfThreadsArgument,
           NULL);
     // Kill if we get here.
@@ -115,9 +117,21 @@ TEST(LinuxDumperTest, VerifyStackReadWithMultipleThreads) {
     FAIL() << "Exec of " << helper_path << " failed: " << strerror(errno);
     exit(0);
   }
-  // The sleep is flaky, but prevents us from reading
-  // the child process before all threads have been created.
-  sleep(1);
+  close(fds[1]);
+  // Wait for the child process to signal that it's ready.
+  struct pollfd pfd;
+  memset(&pfd, 0, sizeof(pfd));
+  pfd.fd = fds[0];
+  pfd.events = POLLIN | POLLERR;
+
+  const int r = HANDLE_EINTR(poll(&pfd, 1, 1000));
+  ASSERT_EQ(1, r);
+  ASSERT_TRUE(pfd.revents & POLLIN);
+  uint8_t junk;
+  read(fds[0], &junk, sizeof(junk));
+  close(fds[0]);
+
+  // Child is ready now.
   LinuxDumper dumper(child_pid);
   ASSERT_TRUE(dumper.Init());
   EXPECT_EQ((size_t)kNumberOfThreadsInHelperProgram, dumper.threads().size());
@@ -240,7 +254,8 @@ TEST(LinuxDumperTest, FileIDsMatch) {
 
   uint8_t identifier1[sizeof(MDGUID)];
   uint8_t identifier2[sizeof(MDGUID)];
-  EXPECT_TRUE(dumper.ElfFileIdentifierForMapping(i, identifier1));
+  EXPECT_TRUE(dumper.ElfFileIdentifierForMapping(*mappings[i], i,
+                                                 identifier1));
   FileID fileid(exe_name);
   EXPECT_TRUE(fileid.ElfFileIdentifier(identifier2));
   char identifier_string1[37];
diff --git a/src/client/linux/minidump_writer/linux_dumper_unittest_helper.cc b/src/client/linux/minidump_writer/linux_dumper_unittest_helper.cc
index 6b7ad5a2..27c2e994 100644
--- a/src/client/linux/minidump_writer/linux_dumper_unittest_helper.cc
+++ b/src/client/linux/minidump_writer/linux_dumper_unittest_helper.cc
@@ -32,6 +32,7 @@
 // id.
 
 #include <pthread.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/syscall.h>
@@ -58,7 +59,13 @@ void *thread_function(void *data) {
 }
 
 int main(int argc, char *argv[]) {
-  int num_threads = atoi(argv[1]);
+  if (argc < 2) {
+    fprintf(stderr,
+            "usage: linux_dumper_unittest_helper <pipe fd> <# of threads\n");
+    return 1;
+  }
+  int pipefd = atoi(argv[1]);
+  int num_threads = atoi(argv[2]);
   if (num_threads < 1) {
     fprintf(stderr, "ERROR: number of threads is 0");
     return 1;
@@ -70,6 +77,9 @@ int main(int argc, char *argv[]) {
   for (int i = 1; i < num_threads; i++) {
     pthread_create(&threads[i], &thread_attributes, &thread_function, NULL);
   }
+  // Signal parent that this process has started all threads.
+  uint8_t byte = 1;
+  write(pipefd, &byte, sizeof(byte));
   thread_function(NULL);
   return 0;
 }
diff --git a/src/client/linux/minidump_writer/minidump_writer.cc b/src/client/linux/minidump_writer/minidump_writer.cc
index 405ec4e8..3eb90953 100644
--- a/src/client/linux/minidump_writer/minidump_writer.cc
+++ b/src/client/linux/minidump_writer/minidump_writer.cc
@@ -368,7 +368,8 @@ class MinidumpWriter {
  public:
   MinidumpWriter(const char* filename,
                  pid_t crashing_pid,
-                 const ExceptionHandler::CrashContext* context)
+                 const ExceptionHandler::CrashContext* context,
+                 const MappingList& mappings)
       : filename_(filename),
         siginfo_(&context->siginfo),
         ucontext_(&context->context),
@@ -380,7 +381,8 @@ class MinidumpWriter {
 #endif
         crashing_tid_(context->tid),
         dumper_(crashing_pid),
-        memory_blocks_(dumper_.allocator()) {
+        memory_blocks_(dumper_.allocator()),
+        mapping_list_(mappings) {
   }
 
   bool Init() {
@@ -752,17 +754,34 @@ class MinidumpWriter {
     return true;
   }
 
+  // If there is caller-provided information about this mapping
+  // in the mapping_list_ list, return true. Otherwise, return false.
+  bool HaveMappingInfo(const MappingInfo& mapping) {
+    for (MappingList::const_iterator iter = mapping_list_.begin();
+         iter != mapping_list_.end();
+         ++iter) {
+      // Ignore any mappings that are wholly contained within
+      // mappings in the mapping_info_ list.
+      if (mapping.start_addr >= iter->first.start_addr &&
+          (mapping.start_addr + mapping.size) <=
+          (iter->first.start_addr + iter->first.size)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   // Write information about the mappings in effect. Because we are using the
   // minidump format, the information about the mappings is pretty limited.
   // Because of this, we also include the full, unparsed, /proc/$x/maps file in
   // another stream in the file.
   bool WriteMappings(MDRawDirectory* dirent) {
     const unsigned num_mappings = dumper_.mappings().size();
-    unsigned num_output_mappings = 0;
+    unsigned num_output_mappings = mapping_list_.size();
 
     for (unsigned i = 0; i < dumper_.mappings().size(); ++i) {
       const MappingInfo& mapping = *dumper_.mappings()[i];
-      if (ShouldIncludeMapping(mapping))
+      if (ShouldIncludeMapping(mapping) && !HaveMappingInfo(mapping))
         num_output_mappings++;
     }
 
@@ -774,56 +793,86 @@ class MinidumpWriter {
     dirent->location = list.location();
     *list.get() = num_output_mappings;
 
-    for (unsigned i = 0, j = 0; i < num_mappings; ++i) {
+    // First write all the mappings from the dumper
+    unsigned int j = 0;
+    for (unsigned i = 0; i < num_mappings; ++i) {
       const MappingInfo& mapping = *dumper_.mappings()[i];
-      if (!ShouldIncludeMapping(mapping))
+      if (!ShouldIncludeMapping(mapping) || HaveMappingInfo(mapping))
         continue;
 
       MDRawModule mod;
-      my_memset(&mod, 0, MD_MODULE_SIZE);
-      mod.base_of_image = mapping.start_addr;
-      mod.size_of_image = mapping.size;
-      const size_t filepath_len = my_strlen(mapping.name);
-
-      // Figure out file name from path
-      const char* filename_ptr = mapping.name + filepath_len - 1;
-      while (filename_ptr >= mapping.name) {
-        if (*filename_ptr == '/')
-          break;
-        filename_ptr--;
-      }
-      filename_ptr++;
-      const size_t filename_len = mapping.name + filepath_len - filename_ptr;
-
-      uint8_t cv_buf[MDCVInfoPDB70_minsize + NAME_MAX];
-      uint8_t* cv_ptr = cv_buf;
-      UntypedMDRVA cv(&minidump_writer_);
-      if (!cv.Allocate(MDCVInfoPDB70_minsize + filename_len + 1))
+      if (!FillRawModule(mapping, i, mod, NULL))
         return false;
+      list.CopyIndexAfterObject(j++, &mod, MD_MODULE_SIZE);
+    }
+    // Next write all the mappings provided by the caller
+    for (MappingList::const_iterator iter = mapping_list_.begin();
+         iter != mapping_list_.end();
+         ++iter) {
+      MDRawModule mod;
+      if (!FillRawModule(iter->first, -1, mod, iter->second))
+        return false;
+      list.CopyIndexAfterObject(j++, &mod, MD_MODULE_SIZE);
+    }
 
-      const uint32_t cv_signature = MD_CVINFOPDB70_SIGNATURE;
-      memcpy(cv_ptr, &cv_signature, sizeof(cv_signature));
-      cv_ptr += sizeof(cv_signature);
-      uint8_t* signature = cv_ptr;
-      cv_ptr += sizeof(MDGUID);
-      dumper_.ElfFileIdentifierForMapping(i, signature);
-      my_memset(cv_ptr, 0, sizeof(uint32_t));  // Set age to 0 on Linux.
-      cv_ptr += sizeof(uint32_t);
+    return true;
+  }
 
-      // Write pdb_file_name
-      memcpy(cv_ptr, filename_ptr, filename_len + 1);
-      cv.Copy(cv_buf, MDCVInfoPDB70_minsize + filename_len + 1);
+  // Fill the MDRawModule |mod| with information about the provided
+  // |mapping|. If |identifier| is non-NULL, use it instead of calculating
+  // a file ID from the mapping. |mapping_id| can be -1 if this mapping
+  // is not from the LinuxDumper.
+  bool FillRawModule(const MappingInfo& mapping,
+                     unsigned int mapping_id,
+                     MDRawModule& mod,
+                     const u_int8_t* identifier) {
+    my_memset(&mod, 0, MD_MODULE_SIZE);
+
+    mod.base_of_image = mapping.start_addr;
+    mod.size_of_image = mapping.size;
+    const size_t filepath_len = my_strlen(mapping.name);
+
+    // Figure out file name from path
+    const char* filename_ptr = mapping.name + filepath_len - 1;
+    while (filename_ptr >= mapping.name) {
+      if (*filename_ptr == '/')
+        break;
+      filename_ptr--;
+    }
+    filename_ptr++;
 
-      mod.cv_record = cv.location();
+    const size_t filename_len = mapping.name + filepath_len - filename_ptr;
 
-      MDLocationDescriptor ld;
-      if (!minidump_writer_.WriteString(mapping.name, filepath_len, &ld))
-        return false;
-      mod.module_name_rva = ld.rva;
+    uint8_t cv_buf[MDCVInfoPDB70_minsize + NAME_MAX];
+    uint8_t* cv_ptr = cv_buf;
+    UntypedMDRVA cv(&minidump_writer_);
+    if (!cv.Allocate(MDCVInfoPDB70_minsize + filename_len + 1))
+      return false;
 
-      list.CopyIndexAfterObject(j++, &mod, MD_MODULE_SIZE);
+    const uint32_t cv_signature = MD_CVINFOPDB70_SIGNATURE;
+    memcpy(cv_ptr, &cv_signature, sizeof(cv_signature));
+    cv_ptr += sizeof(cv_signature);
+    uint8_t* signature = cv_ptr;
+    cv_ptr += sizeof(MDGUID);
+    if (identifier) {
+      // GUID was provided by caller.
+      memcpy(signature, identifier, sizeof(MDGUID));
+    } else {
+      dumper_.ElfFileIdentifierForMapping(mapping, mapping_id, signature);
     }
+    my_memset(cv_ptr, 0, sizeof(uint32_t));  // Set age to 0 on Linux.
+    cv_ptr += sizeof(uint32_t);
 
+    // Write pdb_file_name
+    memcpy(cv_ptr, filename_ptr, filename_len + 1);
+    cv.Copy(cv_buf, MDCVInfoPDB70_minsize + filename_len + 1);
+
+    mod.cv_record = cv.location();
+
+    MDLocationDescriptor ld;
+    if (!minidump_writer_.WriteString(mapping.name, filepath_len, &ld))
+      return false;
+    mod.module_name_rva = ld.rva;
     return true;
   }
 
@@ -1233,15 +1282,24 @@ class MinidumpWriter {
   // written while writing the thread list stream, but saved here
   // so a memory list stream can be written afterwards.
   wasteful_vector<MDMemoryDescriptor> memory_blocks_;
+  // Additional information about some mappings provided by the caller.
+  const MappingList& mapping_list_;
 };
 
 bool WriteMinidump(const char* filename, pid_t crashing_process,
                    const void* blob, size_t blob_size) {
+  MappingList m;
+  return WriteMinidump(filename, crashing_process, blob, blob_size, m);
+}
+
+bool WriteMinidump(const char* filename, pid_t crashing_process,
+                   const void* blob, size_t blob_size,
+                   const MappingList& mappings) {
   if (blob_size != sizeof(ExceptionHandler::CrashContext))
     return false;
   const ExceptionHandler::CrashContext* context =
       reinterpret_cast<const ExceptionHandler::CrashContext*>(blob);
-  MinidumpWriter writer(filename, crashing_process, context);
+  MinidumpWriter writer(filename, crashing_process, context, mappings);
   if (!writer.Init())
     return false;
   return writer.Dump();
diff --git a/src/client/linux/minidump_writer/minidump_writer.h b/src/client/linux/minidump_writer/minidump_writer.h
index 579f68cd..156ca35f 100644
--- a/src/client/linux/minidump_writer/minidump_writer.h
+++ b/src/client/linux/minidump_writer/minidump_writer.h
@@ -33,8 +33,17 @@
 #include <stdint.h>
 #include <unistd.h>
 
+#include <list>
+#include <utility>
+
+#include "google_breakpad/common/minidump_format.h"
+
 namespace google_breakpad {
 
+// A list of <MappingInfo, GUID>
+typedef std::pair<struct MappingInfo, u_int8_t[sizeof(MDGUID)]> MappingEntry;
+typedef std::list<MappingEntry> MappingList;
+
 // Write a minidump to the filesystem. This function does not malloc nor use
 // libc functions which may. Thus, it can be used in contexts where the state
 // of the heap may be corrupt.
@@ -48,6 +57,11 @@ namespace google_breakpad {
 bool WriteMinidump(const char* filename, pid_t crashing_process,
                    const void* blob, size_t blob_size);
 
+// This overload also allows passing a list of known mappings.
+bool WriteMinidump(const char* filename, pid_t crashing_process,
+                   const void* blob, size_t blob_size,
+                   const MappingList& mappings);
+
 }  // namespace google_breakpad
 
 #endif  // CLIENT_LINUX_MINIDUMP_WRITER_MINIDUMP_WRITER_H_
diff --git a/src/client/linux/minidump_writer/minidump_writer_unittest.cc b/src/client/linux/minidump_writer/minidump_writer_unittest.cc
index 0a3b46f2..5377aaca 100644
--- a/src/client/linux/minidump_writer/minidump_writer_unittest.cc
+++ b/src/client/linux/minidump_writer/minidump_writer_unittest.cc
@@ -28,12 +28,17 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <unistd.h>
+#include <sys/poll.h>
+#include <sys/stat.h>
 #include <sys/syscall.h>
 
+#include "breakpad_googletest_includes.h"
 #include "client/linux/handler/exception_handler.h"
+#include "client/linux/minidump_writer/linux_dumper.h"
 #include "client/linux/minidump_writer/minidump_writer.h"
 #include "common/linux/eintr_wrapper.h"
-#include "breakpad_googletest_includes.h"
+#include "common/linux/file_id.h"
+#include "google_breakpad/processor/minidump.h"
 
 using namespace google_breakpad;
 
@@ -43,6 +48,10 @@ using namespace google_breakpad;
 #define TEMPDIR "/data/local/tmp"
 #endif
 
+// Length of a formatted GUID string =
+// sizeof(MDGUID) * 2 + 4 (for dashes) + 1 (null terminator)
+const int kGUIDStringSize = 37;
+
 namespace {
 typedef testing::Test MinidumpWriterTest;
 }
@@ -76,3 +85,307 @@ TEST(MinidumpWriterTest, Setup) {
 
   close(fds[1]);
 }
+
+// Test that mapping info can be specified when writing a minidump,
+// and that it ends up in the module list of the minidump.
+TEST(MinidumpWriterTest, MappingInfo) {
+  int fds[2];
+  ASSERT_NE(-1, pipe(fds));
+
+  // These are defined here so the parent can use them to check the
+  // data from the minidump afterwards.
+  const u_int32_t kMemorySize = sysconf(_SC_PAGESIZE);
+  const char* kMemoryName = "a fake module";
+  const u_int8_t kModuleGUID[sizeof(MDGUID)] = {
+    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";
+  
+  // Get some memory.
+  char* memory =
+    reinterpret_cast<char*>(mmap(NULL,
+                                 kMemorySize,
+                                 PROT_READ | PROT_WRITE,
+                                 MAP_PRIVATE | MAP_ANON,
+                                 -1,
+                                 0));
+  const u_int64_t kMemoryAddress = reinterpret_cast<u_int64_t>(memory);
+  ASSERT_TRUE(memory);
+
+  const pid_t child = fork();
+  if (child == 0) {
+    close(fds[1]);
+    char b;
+    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));
+  context.tid = 1;
+
+  char templ[] = TEMPDIR "/minidump-writer-unittest-XXXXXX";
+  mktemp(templ);
+
+  // Add information about the mapped memory.
+  MappingInfo info;
+  info.start_addr = kMemoryAddress;
+  info.size = kMemorySize;
+  info.offset = 0;
+  strcpy(info.name, kMemoryName);
+  
+  MappingList mappings;
+  MappingEntry mapping;
+  mapping.first = info;
+  memcpy(mapping.second, kModuleGUID, sizeof(MDGUID));
+  mappings.push_back(mapping);
+  ASSERT_TRUE(WriteMinidump(templ, child, &context, sizeof(context), mappings));
+
+  // Read the minidump. Load the module list, and ensure that
+  // the mmap'ed |memory| is listed with the given module name
+  // and debug ID.
+  Minidump minidump(templ);
+  ASSERT_TRUE(minidump.Read());
+
+  MinidumpModuleList* module_list = minidump.GetModuleList();
+  ASSERT_TRUE(module_list);
+  const MinidumpModule* module =
+    module_list->GetModuleForAddress(kMemoryAddress);
+  ASSERT_TRUE(module);
+
+  EXPECT_EQ(kMemoryAddress, module->base_address());
+  EXPECT_EQ(kMemorySize, module->size());
+  EXPECT_EQ(kMemoryName, module->code_file());
+  EXPECT_EQ(module_identifier, module->debug_identifier());
+
+  unlink(templ);
+  close(fds[1]);
+}
+
+// Test that mapping info can be specified, and that it overrides
+// existing mappings that are wholly contained within the specified
+// range.
+TEST(MinidumpWriterTest, MappingInfoContained) {
+  int fds[2];
+  ASSERT_NE(-1, pipe(fds));
+
+  // These are defined here so the parent can use them to check the
+  // data from the minidump afterwards.
+  const u_int32_t kMemorySize = sysconf(_SC_PAGESIZE);
+  const char* kMemoryName = "a fake module";
+  const u_int8_t kModuleGUID[sizeof(MDGUID)] = {
+    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";
+  
+  // mmap a file
+  char tempfile[] = TEMPDIR "/minidump-writer-unittest-temp-XXXXXX";
+  mktemp(tempfile);
+  int fd = open(tempfile, O_RDWR | O_CREAT, 0);
+  ASSERT_NE(-1, fd);
+  unlink(tempfile);
+  // fill with zeros
+  char buffer[kMemorySize];
+  memset(buffer, 0, kMemorySize);
+  ASSERT_EQ(kMemorySize, write(fd, buffer, kMemorySize));
+  lseek(fd, 0, SEEK_SET);
+
+  char* memory =
+    reinterpret_cast<char*>(mmap(NULL,
+                                 kMemorySize,
+                                 PROT_READ | PROT_WRITE,
+                                 MAP_PRIVATE,
+                                 fd,
+                                 0));
+  const u_int64_t kMemoryAddress = reinterpret_cast<u_int64_t>(memory);
+  ASSERT_TRUE(memory);
+  close(fd);
+
+  const pid_t child = fork();
+  if (child == 0) {
+    close(fds[1]);
+    char b;
+    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));
+  context.tid = 1;
+
+  char dumpfile[] = TEMPDIR "/minidump-writer-unittest-XXXXXX";
+  mktemp(dumpfile);
+
+  // Add information about the mapped memory. Report it as being larger than
+  // it actually is.
+  MappingInfo info;
+  info.start_addr = kMemoryAddress - kMemorySize;
+  info.size = kMemorySize * 3;
+  info.offset = 0;
+  strcpy(info.name, kMemoryName);
+
+  MappingList mappings;
+  MappingEntry mapping;
+  mapping.first = info;
+  memcpy(mapping.second, kModuleGUID, sizeof(MDGUID));
+  mappings.push_back(mapping);
+  ASSERT_TRUE(WriteMinidump(dumpfile, child, &context, sizeof(context), mappings));
+
+  // Read the minidump. Load the module list, and ensure that
+  // the mmap'ed |memory| is listed with the given module name
+  // and debug ID.
+  Minidump minidump(dumpfile);
+  ASSERT_TRUE(minidump.Read());
+
+  MinidumpModuleList* module_list = minidump.GetModuleList();
+  ASSERT_TRUE(module_list);
+  const MinidumpModule* module =
+    module_list->GetModuleForAddress(kMemoryAddress);
+  ASSERT_TRUE(module);
+
+  EXPECT_EQ(info.start_addr, module->base_address());
+  EXPECT_EQ(info.size, module->size());
+  EXPECT_EQ(kMemoryName, module->code_file());
+  EXPECT_EQ(module_identifier, module->debug_identifier());
+
+  unlink(dumpfile);
+  close(fds[1]);
+}
+
+TEST(MinidumpWriterTest, DeletedBinary) {
+  static const int kNumberOfThreadsInHelperProgram = 1;
+  char kNumberOfThreadsArgument[2];
+  sprintf(kNumberOfThreadsArgument, "%d", kNumberOfThreadsInHelperProgram);
+
+  // Locate helper binary next to the current binary.
+  char self_path[PATH_MAX];
+  if (readlink("/proc/self/exe", self_path, sizeof(self_path) - 1) == -1) {
+    FAIL() << "readlink failed: " << strerror(errno);
+    exit(1);
+  }
+  string helper_path(self_path);
+  size_t pos = helper_path.rfind('/');
+  if (pos == string::npos) {
+    FAIL() << "no trailing slash in path: " << helper_path;
+    exit(1);
+  }
+  helper_path.erase(pos + 1);
+  helper_path += "linux_dumper_unittest_helper";
+
+  // Copy binary to a temp file.
+  char binpath[] = TEMPDIR "/linux-dumper-unittest-helper-XXXXXX";
+  mktemp(binpath);
+  char cmdline[2 * PATH_MAX];
+  sprintf(cmdline, "/bin/cp \"%s\" \"%s\"", helper_path.c_str(), binpath);
+  ASSERT_EQ(0, system(cmdline));
+  ASSERT_EQ(0, chmod(binpath, 0755));
+
+  int fds[2];
+  ASSERT_NE(-1, pipe(fds));
+
+  pid_t child_pid = fork();
+  if (child_pid == 0) {
+    // In child process.
+    close(fds[0]);
+
+    // Pass the pipe fd and the number of threads as arguments.
+    char pipe_fd_string[8];
+    sprintf(pipe_fd_string, "%d", fds[1]);
+    execl(binpath,
+          binpath,
+          pipe_fd_string,
+          kNumberOfThreadsArgument,
+          NULL);
+  }
+  close(fds[1]);
+  // Wait for the child process to signal that it's ready.
+  struct pollfd pfd;
+  memset(&pfd, 0, sizeof(pfd));
+  pfd.fd = fds[0];
+  pfd.events = POLLIN | POLLERR;
+
+  const int r = HANDLE_EINTR(poll(&pfd, 1, 1000));
+  ASSERT_EQ(1, r);
+  ASSERT_TRUE(pfd.revents & POLLIN);
+  uint8_t junk;
+  read(fds[0], &junk, sizeof(junk));
+  close(fds[0]);
+
+  // Child is ready now.
+  // Unlink the test binary.
+  unlink(binpath);
+
+  ExceptionHandler::CrashContext context;
+  memset(&context, 0, sizeof(context));
+
+  char templ[] = TEMPDIR "/minidump-writer-unittest-XXXXXX";
+  mktemp(templ);
+  // Set a non-zero tid to avoid tripping asserts.
+  context.tid = 1;
+  ASSERT_TRUE(WriteMinidump(templ, child_pid, &context, sizeof(context)));
+  kill(child_pid, SIGKILL);
+
+  struct stat st;
+  ASSERT_EQ(stat(templ, &st), 0);
+  ASSERT_GT(st.st_size, 0u);
+
+
+
+  Minidump minidump(templ);
+  ASSERT_TRUE(minidump.Read());
+
+  // Check that the main module filename is correct.
+  MinidumpModuleList* module_list = minidump.GetModuleList();
+  ASSERT_TRUE(module_list);
+  const MinidumpModule* module = module_list->GetMainModule();
+  EXPECT_STREQ(binpath, module->code_file().c_str());
+  // Check that the file ID is correct.
+  FileID fileid(helper_path.c_str());
+  uint8_t identifier[sizeof(MDGUID)];
+  EXPECT_TRUE(fileid.ElfFileIdentifier(identifier));
+  char identifier_string[kGUIDStringSize];
+  FileID::ConvertIdentifierToString(identifier,
+                                    identifier_string,
+                                    kGUIDStringSize);
+  string module_identifier(identifier_string);
+  // Strip out dashes
+  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";
+  EXPECT_EQ(module_identifier, module->debug_identifier());
+
+  unlink(templ);
+}