Introduce microdump writer class.

Microdumps are a very lightweight variant of minidumps. They are meant
to dump a minimal crash report on the system log (logcat on Android),
containing only the state of the crashing thread.
This is to deal with cases where the user has opted out from crash
uploading but we still want to generate meaningful information on the
device to pull a stacktrace for development purposes.
Conversely to conventional stack traces (e.g. the one generated by
Android's debuggerd or Chromium's base::stacktrace) microdumps do NOT
require unwind tables to be present in the target binary. This allows
to save precious binary size (~1.5 MB for Chrome on Arm, ~10 MB on
arm64).
More information and design doc on crbug.com/410294

BUG=chromium:410294

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1398 4c0a9323-5329-0410-9bdc-e9ce6186880e

7 files changed, 490 insertions, 21 deletions

diff --git a/src/client/linux/dump_writer_common/mapping_info.h b/src/client/linux/dump_writer_common/mapping_info.h
index c206b504..5f247cfd 100644
--- a/src/client/linux/dump_writer_common/mapping_info.h
+++ b/src/client/linux/dump_writer_common/mapping_info.h
@@ -30,8 +30,12 @@
 #ifndef CLIENT_LINUX_DUMP_WRITER_COMMON_MAPPING_INFO_H_
 #define CLIENT_LINUX_DUMP_WRITER_COMMON_MAPPING_INFO_H_
 
+#include <limits.h>
+#include <list>
 #include <stdint.h>
 
+#include "google_breakpad/common/minidump_format.h"
+
 namespace google_breakpad {
 
 // One of these is produced for each mapping in the process (i.e. line in
@@ -44,6 +48,14 @@ struct MappingInfo {
   char name[NAME_MAX];
 };
 
+struct MappingEntry {
+  MappingInfo first;
+  uint8_t second[sizeof(MDGUID)];
+};
+
+// A list of <MappingInfo, GUID>
+typedef std::list<MappingEntry> MappingList;
+
 }  // namespace google_breakpad
 
 #endif  // CLIENT_LINUX_DUMP_WRITER_COMMON_MAPPING_INFO_H_
diff --git a/src/client/linux/handler/exception_handler.cc b/src/client/linux/handler/exception_handler.cc
index 7cad7756..3e2d1962 100644
--- a/src/client/linux/handler/exception_handler.cc
+++ b/src/client/linux/handler/exception_handler.cc
@@ -91,6 +91,7 @@
 #include "common/linux/linux_libc_support.h"
 #include "common/memory.h"
 #include "client/linux/log/log.h"
+#include "client/linux/microdump_writer/microdump_writer.h"
 #include "client/linux/minidump_writer/linux_dumper.h"
 #include "client/linux/minidump_writer/minidump_writer.h"
 #include "common/linux/eintr_wrapper.h"
@@ -210,7 +211,8 @@ ExceptionHandler::ExceptionHandler(const MinidumpDescriptor& descriptor,
   if (server_fd >= 0)
     crash_generation_client_.reset(CrashGenerationClient::TryCreate(server_fd));
 
-  if (!IsOutOfProcess() && !minidump_descriptor_.IsFD())
+  if (!IsOutOfProcess() && !minidump_descriptor_.IsFD() &&
+      !minidump_descriptor_.IsMicrodumpOnConsole())
     minidump_descriptor_.UpdatePath();
 
   pthread_mutex_lock(&g_handler_stack_mutex_);
@@ -548,6 +550,12 @@ void ExceptionHandler::WaitForContinueSignal() {
 // Runs on the cloned process.
 bool ExceptionHandler::DoDump(pid_t crashing_process, const void* context,
                               size_t context_size) {
+  if (minidump_descriptor_.IsMicrodumpOnConsole()) {
+    return google_breakpad::WriteMicrodump(crashing_process,
+                                           context,
+                                           context_size,
+                                           mapping_list_);
+  }
   if (minidump_descriptor_.IsFD()) {
     return google_breakpad::WriteMinidump(minidump_descriptor_.fd(),
                                           minidump_descriptor_.size_limit(),
@@ -583,7 +591,8 @@ bool ExceptionHandler::WriteMinidump(const string& dump_path,
 __attribute__((optimize("no-omit-frame-pointer")))
 #endif
 bool ExceptionHandler::WriteMinidump() {
-  if (!IsOutOfProcess() && !minidump_descriptor_.IsFD()) {
+  if (!IsOutOfProcess() && !minidump_descriptor_.IsFD() &&
+      !minidump_descriptor_.IsMicrodumpOnConsole()) {
     // Update the path of the minidump so that this can be called multiple times
     // and new files are created for each minidump.  This is done before the
     // generation happens, as clients may want to access the MinidumpDescriptor
diff --git a/src/client/linux/handler/minidump_descriptor.cc b/src/client/linux/handler/minidump_descriptor.cc
index c4618adc..029f8926 100644
--- a/src/client/linux/handler/minidump_descriptor.cc
+++ b/src/client/linux/handler/minidump_descriptor.cc
@@ -35,8 +35,12 @@
 
 namespace google_breakpad {
 
+//static
+const MinidumpDescriptor::MicrodumpOnConsole kMicrodumpOnConsole = {};
+
 MinidumpDescriptor::MinidumpDescriptor(const MinidumpDescriptor& descriptor)
-    : fd_(descriptor.fd_),
+    : mode_(descriptor.mode_),
+      fd_(descriptor.fd_),
       directory_(descriptor.directory_),
       c_path_(NULL),
       size_limit_(descriptor.size_limit_) {
@@ -50,6 +54,7 @@ MinidumpDescriptor& MinidumpDescriptor::operator=(
     const MinidumpDescriptor& descriptor) {
   assert(descriptor.path_.empty());
 
+  mode_ = descriptor.mode_;
   fd_ = descriptor.fd_;
   directory_ = descriptor.directory_;
   path_.clear();
@@ -63,7 +68,7 @@ MinidumpDescriptor& MinidumpDescriptor::operator=(
 }
 
 void MinidumpDescriptor::UpdatePath() {
-  assert(fd_ == -1 && !directory_.empty());
+  assert(mode_ == kWriteMinidumpToFile && !directory_.empty());
 
   GUID guid;
   char guid_str[kGUIDStringLength + 1];
@@ -72,7 +77,7 @@ void MinidumpDescriptor::UpdatePath() {
   }
 
   path_.clear();
-  path_ = directory_ + "/" + guid_str + ".dmp";  
+  path_ = directory_ + "/" + guid_str + ".dmp";
   c_path_ = path_.c_str();
 }
 
diff --git a/src/client/linux/handler/minidump_descriptor.h b/src/client/linux/handler/minidump_descriptor.h
index 9ffe622b..ed656cee 100644
--- a/src/client/linux/handler/minidump_descriptor.h
+++ b/src/client/linux/handler/minidump_descriptor.h
@@ -37,18 +37,25 @@
 
 #include "common/using_std_string.h"
 
-// The MinidumpDescriptor describes how to access a minidump: it can contain
-// either a file descriptor or a path.
-// Note that when using files, it is created with the path to a directory.
-// The actual path where the minidump is generated is created by this class.
+// This class describes how a crash dump should be generated, either:
+// - Writing a full minidump to a file in a given directory (the actual path,
+//   inside the directory, is determined by this class).
+// - Writing a full minidump to a given fd.
+// - Writing a reduced microdump to the console (logcat on Android).
 namespace google_breakpad {
 
 class MinidumpDescriptor {
  public:
-  MinidumpDescriptor() : fd_(-1), size_limit_(-1) {}
+  struct MicrodumpOnConsole {};
+  static const MicrodumpOnConsole kMicrodumpOnConsole;
+
+  MinidumpDescriptor() : mode_(kUninitialized),
+                         fd_(-1),
+                         size_limit_(-1) {}
 
   explicit MinidumpDescriptor(const string& directory)
-      : fd_(-1),
+      : mode_(kWriteMinidumpToFile),
+        fd_(-1),
         directory_(directory),
         c_path_(NULL),
         size_limit_(-1) {
@@ -56,16 +63,24 @@ class MinidumpDescriptor {
   }
 
   explicit MinidumpDescriptor(int fd)
-      : fd_(fd),
+      : mode_(kWriteMinidumpToFd),
+        fd_(fd),
         c_path_(NULL),
         size_limit_(-1) {
     assert(fd != -1);
   }
 
+  explicit MinidumpDescriptor(const MicrodumpOnConsole&)
+      : mode_(kWriteMicrodumpToConsole),
+        fd_(-1),
+        size_limit_(-1) {}
+
   explicit MinidumpDescriptor(const MinidumpDescriptor& descriptor);
   MinidumpDescriptor& operator=(const MinidumpDescriptor& descriptor);
 
-  bool IsFD() const { return fd_ != -1; }
+  static MinidumpDescriptor getMicrodumpDescriptor();
+
+  bool IsFD() const { return mode_ == kWriteMinidumpToFd; }
 
   int fd() const { return fd_; }
 
@@ -73,6 +88,10 @@ class MinidumpDescriptor {
 
   const char* path() const { return c_path_; }
 
+  bool IsMicrodumpOnConsole() const {
+    return mode_ == kWriteMicrodumpToConsole;
+  }
+
   // Updates the path so it is unique.
   // Should be called from a normal context: this methods uses the heap.
   void UpdatePath();
@@ -81,6 +100,16 @@ class MinidumpDescriptor {
   void set_size_limit(off_t limit) { size_limit_ = limit; }
 
  private:
+  enum DumpMode {
+    kUninitialized = 0,
+    kWriteMinidumpToFile,
+    kWriteMinidumpToFd,
+    kWriteMicrodumpToConsole
+  };
+
+  // Specifies the dump mode (see DumpMode).
+  DumpMode mode_;
+
   // The file descriptor where the minidump is generated.
   int fd_;
 
diff --git a/src/client/linux/microdump_writer/microdump_writer.cc b/src/client/linux/microdump_writer/microdump_writer.cc
new file mode 100644
index 00000000..494e2a20
--- /dev/null
+++ b/src/client/linux/microdump_writer/microdump_writer.cc
@@ -0,0 +1,364 @@
+// Copyright (c) 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.
+
+// This translation unit generates microdumps into the console (logcat on
+// Android). See crbug.com/410294 for more info and design docs.
+
+#include "client/linux/microdump_writer/microdump_writer.h"
+
+#include <sys/utsname.h>
+
+#include "client/linux/dump_writer_common/seccomp_unwinder.h"
+#include "client/linux/dump_writer_common/thread_info.h"
+#include "client/linux/dump_writer_common/ucontext_reader.h"
+#include "client/linux/handler/exception_handler.h"
+#include "client/linux/minidump_writer/linux_ptrace_dumper.h"
+#include "common/linux/linux_libc_support.h"
+#include "client/linux/log/log.h"
+
+namespace {
+
+using google_breakpad::ExceptionHandler;
+using google_breakpad::LinuxDumper;
+using google_breakpad::LinuxPtraceDumper;
+using google_breakpad::MappingInfo;
+using google_breakpad::MappingList;
+using google_breakpad::RawContextCPU;
+using google_breakpad::SeccompUnwinder;
+using google_breakpad::ThreadInfo;
+using google_breakpad::UContextReader;
+
+class MicrodumpWriter {
+ public:
+  MicrodumpWriter(const ExceptionHandler::CrashContext* context,
+                  const MappingList& mappings,
+                  LinuxDumper* dumper)
+      : ucontext_(context ? &context->context : NULL),
+#if !defined(__ARM_EABI__) && !defined(__mips__)
+        float_state_(context ? &context->float_state : NULL),
+#endif
+        dumper_(dumper),
+        mapping_list_(mappings) { }
+
+  ~MicrodumpWriter() { dumper_->ThreadsResume(); }
+
+  bool Init() {
+    if (!dumper_->Init())
+      return false;
+    return dumper_->ThreadsSuspend();
+  }
+
+  bool Dump() {
+    bool success;
+    LogLine("-----BEGIN BREAKPAD MICRODUMP-----");
+    success = DumpOSInformation();
+    if (success)
+      success = DumpCrashingThread();
+    if (success)
+      success = DumpMappings();
+    LogLine("-----END BREAKPAD MICRODUMP-----");
+    dumper_->ThreadsResume();
+    return success;
+  }
+
+ private:
+  // Writes one line to the system log.
+  void LogLine(const char* msg) {
+    logger::write(msg, my_strlen(msg));
+  }
+
+  // Stages the given string in the current line buffer.
+  void LogAppend(const char* str) {
+    my_strlcat(log_line_, str, sizeof(log_line_));
+  }
+
+  // As above (required to take precedence over template specialization below).
+  void LogAppend(char* str) {
+    LogAppend(const_cast<const char*>(str));
+  }
+
+  // Stages the hex repr. of the given int type in the current line buffer.
+  template<typename T>
+  void LogAppend(T value) {
+    // Make enough room to hex encode the largest int type + NUL.
+    static const char HEX[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+                               'A', 'B', 'C', 'D', 'E', 'F'};
+    char hexstr[sizeof(T) * 2 + 1];
+    for (int i = sizeof(T) * 2 - 1; i >= 0; --i, value >>= 4)
+      hexstr[i] = HEX[static_cast<uint8_t>(value) & 0x0F];
+    hexstr[sizeof(T) * 2] = '\0';
+    LogAppend(hexstr);
+  }
+
+  // Stages the buffer content hex-encoded in the current line buffer.
+  void LogAppend(const void* buf, size_t length) {
+    const uint8_t* ptr = reinterpret_cast<const uint8_t*>(buf);
+    for (size_t i = 0; i < length; ++i, ++ptr)
+      LogAppend(*ptr);
+  }
+
+  // Writes out the current line buffer on the system log.
+  void LogCommitLine() {
+    logger::write(log_line_, my_strlen(log_line_));
+    my_strlcpy(log_line_, "", sizeof(log_line_));
+  }
+
+  bool DumpOSInformation() {
+    struct utsname uts;
+    if (uname(&uts))
+      return false;
+
+#if defined(__ANDROID__)
+    const char kOSId[] = "A";
+#else
+    const char kOSId[] = "L";
+#endif
+
+    LogAppend("O ");
+    LogAppend(kOSId);
+    LogAppend(" \"");
+    LogAppend(uts.machine);
+    LogAppend("\" \"");
+    LogAppend(uts.release);
+    LogAppend(" \"");
+    LogAppend(uts.version);
+    LogAppend("\"");
+    LogCommitLine();
+    return true;
+  }
+
+  bool DumpThreadStack(uint32_t thread_id,
+                       uintptr_t stack_pointer,
+                       int max_stack_len,
+                       uint8_t** stack_copy) {
+    *stack_copy = NULL;
+    const void* stack;
+    size_t stack_len;
+
+    if (!dumper_->GetStackInfo(&stack, &stack_len, stack_pointer)) {
+      assert(false);
+      return false;
+    }
+
+    LogAppend("S 0 ");
+    LogAppend(stack_pointer);
+    LogAppend(" ");
+    LogAppend(reinterpret_cast<uintptr_t>(stack));
+    LogAppend(" ");
+    LogAppend(stack_len);
+    LogCommitLine();
+
+    if (max_stack_len >= 0 &&
+        stack_len > static_cast<unsigned int>(max_stack_len)) {
+      stack_len = max_stack_len;
+    }
+
+    *stack_copy = reinterpret_cast<uint8_t*>(Alloc(stack_len));
+    dumper_->CopyFromProcess(*stack_copy, thread_id, stack, stack_len);
+
+    // Dump the content of the stack, splicing it into chunks which size is
+    // compatible with the max logcat line size (see LOGGER_ENTRY_MAX_PAYLOAD).
+    const size_t STACK_DUMP_CHUNK_SIZE = 384;
+    for (size_t stack_off = 0; stack_off < stack_len;
+         stack_off += STACK_DUMP_CHUNK_SIZE) {
+      LogAppend("S ");
+      LogAppend(reinterpret_cast<uintptr_t>(stack) + stack_off);
+      LogAppend(" ");
+      LogAppend(*stack_copy + stack_off,
+                std::min(STACK_DUMP_CHUNK_SIZE, stack_len - stack_off));
+      LogCommitLine();
+    }
+    return true;
+  }
+
+  // Write information about the crashing thread.
+  bool DumpCrashingThread() {
+    const unsigned num_threads = dumper_->threads().size();
+
+    for (unsigned i = 0; i < num_threads; ++i) {
+      MDRawThread thread;
+      my_memset(&thread, 0, sizeof(thread));
+      thread.thread_id = dumper_->threads()[i];
+
+      // Dump only the crashing thread.
+      if (static_cast<pid_t>(thread.thread_id) != dumper_->crash_thread())
+        continue;
+
+      assert(ucontext_);
+      assert(!dumper_->IsPostMortem());
+
+      uint8_t* stack_copy;
+      const uintptr_t stack_ptr = UContextReader::GetStackPointer(ucontext_);
+      if (!DumpThreadStack(thread.thread_id, stack_ptr, -1, &stack_copy))
+        return false;
+
+      RawContextCPU cpu;
+      my_memset(&cpu, 0, sizeof(RawContextCPU));
+#if !defined(__ARM_EABI__) && !defined(__mips__)
+      UContextReader::FillCPUContext(&cpu, ucontext_, float_state_);
+#else
+      UContextReader::FillCPUContext(&cpu, ucontext_);
+#endif
+      if (stack_copy)
+        SeccompUnwinder::PopSeccompStackFrame(&cpu, thread, stack_copy);
+      DumpCPUState(&cpu);
+    }
+    return true;
+  }
+
+  void DumpCPUState(RawContextCPU* cpu) {
+    LogAppend("C ");
+    LogAppend(cpu, sizeof(*cpu));
+    LogCommitLine();
+  }
+
+  // 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;
+  }
+
+  // Dump information about the provided |mapping|. If |identifier| is non-NULL,
+  // use it instead of calculating a file ID from the mapping.
+  void DumpModule(const MappingInfo& mapping,
+                  bool member,
+                  unsigned int mapping_id,
+                  const uint8_t* identifier) {
+    MDGUID module_identifier;
+    if (identifier) {
+      // GUID was provided by caller.
+      my_memcpy(&module_identifier, identifier, sizeof(MDGUID));
+    } else {
+      dumper_->ElfFileIdentifierForMapping(
+          mapping,
+          member,
+          mapping_id,
+          reinterpret_cast<uint8_t*>(&module_identifier));
+    }
+
+    char file_name[NAME_MAX];
+    char file_path[NAME_MAX];
+    LinuxDumper::GetMappingEffectiveNameAndPath(
+        mapping, file_path, sizeof(file_path), file_name, sizeof(file_name));
+
+    LogAppend("M ");
+    LogAppend(static_cast<uintptr_t>(mapping.start_addr));
+    LogAppend(" ");
+    LogAppend(mapping.offset);
+    LogAppend(" ");
+    LogAppend(mapping.size);
+    LogAppend(" ");
+    LogAppend(module_identifier.data1);
+    LogAppend(module_identifier.data2);
+    LogAppend(module_identifier.data3);
+    LogAppend(module_identifier.data4[0]);
+    LogAppend(module_identifier.data4[1]);
+    LogAppend(module_identifier.data4[2]);
+    LogAppend(module_identifier.data4[3]);
+    LogAppend(module_identifier.data4[4]);
+    LogAppend(module_identifier.data4[5]);
+    LogAppend(module_identifier.data4[6]);
+    LogAppend(module_identifier.data4[7]);
+    LogAppend(" ");
+    LogAppend(file_name);
+    LogCommitLine();
+  }
+
+  // Write information about the mappings in effect.
+  bool DumpMappings() {
+    // First write all the mappings from the dumper
+    for (unsigned i = 0; i < dumper_->mappings().size(); ++i) {
+      const MappingInfo& mapping = *dumper_->mappings()[i];
+      // Skip mappings which don't look like libraries.
+      if (!strstr(mapping.name, ".so") ||  // dump only libs (skip fonts, apks).
+          mapping.size < 4096) { // too small to get a signature for.
+        continue;
+      }
+
+      if (HaveMappingInfo(mapping))
+        continue;
+
+      DumpModule(mapping, true, i, NULL);
+    }
+    // Next write all the mappings provided by the caller
+    for (MappingList::const_iterator iter = mapping_list_.begin();
+         iter != mapping_list_.end();
+         ++iter) {
+      DumpModule(iter->first, false, 0, iter->second);
+    }
+    return true;
+  }
+
+  void* Alloc(unsigned bytes) { return dumper_->allocator()->Alloc(bytes); }
+
+  const struct ucontext* const ucontext_;
+#if !defined(__ARM_EABI__) && !defined(__mips__)
+  const google_breakpad::fpstate_t* const float_state_;
+#endif
+  LinuxDumper* dumper_;
+  const MappingList& mapping_list_;
+  char log_line_[512];
+};
+}  // namespace
+
+namespace google_breakpad {
+
+bool WriteMicrodump(pid_t crashing_process,
+                    const void* blob,
+                    size_t blob_size,
+                    const MappingList& mappings) {
+  LinuxPtraceDumper dumper(crashing_process);
+  const ExceptionHandler::CrashContext* context = NULL;
+  if (blob) {
+    if (blob_size != sizeof(ExceptionHandler::CrashContext))
+      return false;
+    context = reinterpret_cast<const ExceptionHandler::CrashContext*>(blob);
+    dumper.set_crash_address(
+        reinterpret_cast<uintptr_t>(context->siginfo.si_addr));
+    dumper.set_crash_signal(context->siginfo.si_signo);
+    dumper.set_crash_thread(context->tid);
+  }
+  MicrodumpWriter writer(context, mappings, &dumper);
+  if (!writer.Init())
+    return false;
+  return writer.Dump();
+}
+
+}  // namespace google_breakpad
diff --git a/src/client/linux/microdump_writer/microdump_writer.h b/src/client/linux/microdump_writer/microdump_writer.h
new file mode 100644
index 00000000..3c19f3d0
--- /dev/null
+++ b/src/client/linux/microdump_writer/microdump_writer.h
@@ -0,0 +1,58 @@
+// Copyright (c) 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 CLIENT_LINUX_MINIDUMP_WRITER_MICRODUMP_WRITER_H_
+#define CLIENT_LINUX_MINIDUMP_WRITER_MICRODUMP_WRITER_H_
+
+#include <stdint.h>
+#include <sys/types.h>
+
+#include "client/linux/dump_writer_common/mapping_info.h"
+
+namespace google_breakpad {
+
+// Writes a microdump (a reduced dump containing only the state of the crashing
+// thread) on the console (logcat on Android). These functions do not malloc nor
+// use libc functions which may. Thus, it can be used in contexts where the
+// state of the heap may be corrupt.
+// Args:
+//   crashing_process: the pid of the crashing process. This must be trusted.
+//   blob: a blob of data from the crashing process. See exception_handler.h
+//   blob_size: the length of |blob| in bytes.
+//   mappings: a list of additional mappings provided by the application.
+//
+// Returns true iff successful.
+bool WriteMicrodump(pid_t crashing_process,
+                    const void* blob,
+                    size_t blob_size,
+                    const MappingList& mappings);
+
+}  // namespace google_breakpad
+
+#endif  // CLIENT_LINUX_MINIDUMP_WRITER_MICRODUMP_WRITER_H_
diff --git a/src/client/linux/minidump_writer/minidump_writer.h b/src/client/linux/minidump_writer/minidump_writer.h
index e1afe69b..d13fb120 100644
--- a/src/client/linux/minidump_writer/minidump_writer.h
+++ b/src/client/linux/minidump_writer/minidump_writer.h
@@ -45,14 +45,6 @@ namespace google_breakpad {
 
 class ExceptionHandler;
 
-struct MappingEntry {
-  MappingInfo first;
-  uint8_t second[sizeof(MDGUID)];
-};
-
-// A list of <MappingInfo, GUID>
-typedef std::list<MappingEntry> MappingList;
-
 #if defined(__aarch64__)
 typedef struct fpsimd_context fpstate_t;
 #elif !defined(__ARM_EABI__) && !defined(__mips__)