Implement core dump to minidump conversion.

This patch is part of a bigger patch that helps merging the breakpad code
with the modified version in Chromium OS.

Specifically, this patch makes the following changes:
1. Turn the LinuxDumper class into a base class and move ptrace related
   code into a new derived class, LinuxPtraceDumper.
2. Add a LinuxCoreDumper class, which is derived from LinuxDumper, to
   extract information from a crashed process via a core dump file instead
   of ptrace.
3. Add a WriteMinidumpFromCore function to
     src/client/linux/minidump_writer/minidump_writer.h,
   which uses LinuxCoreDumper to extract information from a core dump file.
4. Add a core2md utility, which simply wraps WriteMinidumpFromCore, for
   converting a core dump to a minidump.

BUG=455
TEST=Tested the following:
1. Build on 32-bit and 64-bit Linux with gcc 4.4.3 and gcc 4.6.
2. Build on Mac OS X 10.6.8 with gcc 4.2 and clang 3.0 (with latest gmock).
3. All unit tests pass.
4. Run Chromium OS tests to test core2md.
Review URL: http://breakpad.appspot.com/343001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@905 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 292 insertions, 0 deletions

diff --git a/src/client/linux/minidump_writer/linux_ptrace_dumper.cc b/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
new file mode 100644
index 00000000..ea58dd11
--- /dev/null
+++ b/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
@@ -0,0 +1,292 @@
+// Copyright (c) 2012, 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.
+
+// linux_ptrace_dumper.cc: Implement google_breakpad::LinuxPtraceDumper.
+// See linux_ptrace_dumper.h for detals.
+// This class was originally splitted from google_breakpad::LinuxDumper.
+
+// This code deals with the mechanics of getting information about a crashed
+// process. Since this code may run in a compromised address space, the same
+// rules apply as detailed at the top of minidump_writer.h: no libc calls and
+// use the alternative allocator.
+
+#include "client/linux/minidump_writer/linux_ptrace_dumper.h"
+
+#include <asm/ptrace.h>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+
+#include "client/linux/minidump_writer/directory_reader.h"
+#include "client/linux/minidump_writer/line_reader.h"
+#include "common/linux/linux_libc_support.h"
+#include "third_party/lss/linux_syscall_support.h"
+
+// Suspends a thread by attaching to it.
+static bool SuspendThread(pid_t pid) {
+  // This may fail if the thread has just died or debugged.
+  errno = 0;
+  if (sys_ptrace(PTRACE_ATTACH, pid, NULL, NULL) != 0 &&
+      errno != 0) {
+    return false;
+  }
+  while (sys_waitpid(pid, NULL, __WALL) < 0) {
+    if (errno != EINTR) {
+      sys_ptrace(PTRACE_DETACH, pid, NULL, NULL);
+      return false;
+    }
+  }
+#if defined(__i386) || defined(__x86_64)
+  // On x86, the stack pointer is NULL or -1, when executing trusted code in
+  // the seccomp sandbox. Not only does this cause difficulties down the line
+  // when trying to dump the thread's stack, it also results in the minidumps
+  // containing information about the trusted threads. This information is
+  // generally completely meaningless and just pollutes the minidumps.
+  // We thus test the stack pointer and exclude any threads that are part of
+  // the seccomp sandbox's trusted code.
+  user_regs_struct regs;
+  if (sys_ptrace(PTRACE_GETREGS, pid, NULL, &regs) == -1 ||
+#if defined(__i386)
+      !regs.esp
+#elif defined(__x86_64)
+      !regs.rsp
+#endif
+      ) {
+    sys_ptrace(PTRACE_DETACH, pid, NULL, NULL);
+    return false;
+  }
+#endif
+  return true;
+}
+
+// Resumes a thread by detaching from it.
+static bool ResumeThread(pid_t pid) {
+  return sys_ptrace(PTRACE_DETACH, pid, NULL, NULL) >= 0;
+}
+
+namespace google_breakpad {
+
+LinuxPtraceDumper::LinuxPtraceDumper(pid_t pid)
+    : LinuxDumper(pid),
+      threads_suspended_(false) {
+}
+
+bool LinuxPtraceDumper::BuildProcPath(char* path, pid_t pid,
+                                      const char* node) const {
+  if (!path || !node || pid <= 0)
+    return false;
+
+  size_t node_len = my_strlen(node);
+  if (node_len == 0)
+    return false;
+
+  const unsigned pid_len = my_int_len(pid);
+  const size_t total_length = 6 + pid_len + 1 + node_len;
+  if (total_length >= NAME_MAX)
+    return false;
+
+  memcpy(path, "/proc/", 6);
+  my_itos(path + 6, pid, pid_len);
+  path[6 + pid_len] = '/';
+  memcpy(path + 6 + pid_len + 1, node, node_len);
+  path[total_length] = '\0';
+  return true;
+}
+
+void LinuxPtraceDumper::CopyFromProcess(void* dest, pid_t child,
+                                        const void* src, size_t length) {
+  unsigned long tmp = 55;
+  size_t done = 0;
+  static const size_t word_size = sizeof(tmp);
+  uint8_t* const local = (uint8_t*) dest;
+  uint8_t* const remote = (uint8_t*) src;
+
+  while (done < length) {
+    const size_t l = (length - done > word_size) ? word_size : (length - done);
+    if (sys_ptrace(PTRACE_PEEKDATA, child, remote + done, &tmp) == -1) {
+      tmp = 0;
+    }
+    memcpy(local + done, &tmp, l);
+    done += l;
+  }
+}
+
+// Read thread info from /proc/$pid/status.
+// Fill out the |tgid|, |ppid| and |pid| members of |info|. If unavailable,
+// these members are set to -1. Returns true iff all three members are
+// available.
+bool LinuxPtraceDumper::GetThreadInfoByIndex(size_t index, ThreadInfo* info) {
+  if (index >= threads_.size())
+    return false;
+
+  pid_t tid = threads_[index];
+
+  assert(info != NULL);
+  char status_path[NAME_MAX];
+  if (!BuildProcPath(status_path, tid, "status"))
+    return false;
+
+  const int fd = sys_open(status_path, O_RDONLY, 0);
+  if (fd < 0)
+    return false;
+
+  LineReader* const line_reader = new(allocator_) LineReader(fd);
+  const char* line;
+  unsigned line_len;
+
+  info->ppid = info->tgid = -1;
+
+  while (line_reader->GetNextLine(&line, &line_len)) {
+    if (my_strncmp("Tgid:\t", line, 6) == 0) {
+      my_strtoui(&info->tgid, line + 6);
+    } else if (my_strncmp("PPid:\t", line, 6) == 0) {
+      my_strtoui(&info->ppid, line + 6);
+    }
+
+    line_reader->PopLine(line_len);
+  }
+
+  if (info->ppid == -1 || info->tgid == -1)
+    return false;
+
+  if (sys_ptrace(PTRACE_GETREGS, tid, NULL, &info->regs) == -1) {
+    return false;
+  }
+
+#if !defined(__ANDROID__)
+  if (sys_ptrace(PTRACE_GETFPREGS, tid, NULL, &info->fpregs) == -1) {
+    return false;
+  }
+#endif
+
+#if defined(__i386)
+  if (sys_ptrace(PTRACE_GETFPXREGS, tid, NULL, &info->fpxregs) == -1)
+    return false;
+#endif
+
+#if defined(__i386) || defined(__x86_64)
+  for (unsigned i = 0; i < ThreadInfo::kNumDebugRegisters; ++i) {
+    if (sys_ptrace(
+        PTRACE_PEEKUSER, tid,
+        reinterpret_cast<void*> (offsetof(struct user,
+                                          u_debugreg[0]) + i *
+                                 sizeof(debugreg_t)),
+        &info->dregs[i]) == -1) {
+      return false;
+    }
+  }
+#endif
+
+  const uint8_t* stack_pointer;
+#if defined(__i386)
+  memcpy(&stack_pointer, &info->regs.esp, sizeof(info->regs.esp));
+#elif defined(__x86_64)
+  memcpy(&stack_pointer, &info->regs.rsp, sizeof(info->regs.rsp));
+#elif defined(__ARM_EABI__)
+  memcpy(&stack_pointer, &info->regs.ARM_sp, sizeof(info->regs.ARM_sp));
+#else
+#error "This code hasn't been ported to your platform yet."
+#endif
+
+  return GetStackInfo(&info->stack, &info->stack_len,
+                      (uintptr_t) stack_pointer);
+}
+
+bool LinuxPtraceDumper::IsPostMortem() const {
+  return false;
+}
+
+bool LinuxPtraceDumper::ThreadsSuspend() {
+  if (threads_suspended_)
+    return true;
+  for (size_t i = 0; i < threads_.size(); ++i) {
+    if (!SuspendThread(threads_[i])) {
+      // If the thread either disappeared before we could attach to it, or if
+      // it was part of the seccomp sandbox's trusted code, it is OK to
+      // silently drop it from the minidump.
+      memmove(&threads_[i], &threads_[i+1],
+              (threads_.size() - i - 1) * sizeof(threads_[i]));
+      threads_.resize(threads_.size() - 1);
+      --i;
+    }
+  }
+  threads_suspended_ = true;
+  return threads_.size() > 0;
+}
+
+bool LinuxPtraceDumper::ThreadsResume() {
+  if (!threads_suspended_)
+    return false;
+  bool good = true;
+  for (size_t i = 0; i < threads_.size(); ++i)
+    good &= ResumeThread(threads_[i]);
+  threads_suspended_ = false;
+  return good;
+}
+
+// Parse /proc/$pid/task to list all the threads of the process identified by
+// pid.
+bool LinuxPtraceDumper::EnumerateThreads() {
+  char task_path[NAME_MAX];
+  if (!BuildProcPath(task_path, pid_, "task"))
+    return false;
+
+  const int fd = sys_open(task_path, O_RDONLY | O_DIRECTORY, 0);
+  if (fd < 0)
+    return false;
+  DirectoryReader* dir_reader = new(allocator_) DirectoryReader(fd);
+
+  // The directory may contain duplicate entries which we filter by assuming
+  // that they are consecutive.
+  int last_tid = -1;
+  const char* dent_name;
+  while (dir_reader->GetNextEntry(&dent_name)) {
+    if (my_strcmp(dent_name, ".") &&
+        my_strcmp(dent_name, "..")) {
+      int tid = 0;
+      if (my_strtoui(&tid, dent_name) &&
+          last_tid != tid) {
+        last_tid = tid;
+        threads_.push_back(tid);
+      }
+    }
+    dir_reader->PopEntry();
+  }
+
+  sys_close(fd);
+  return true;
+}
+
+}  // namespace google_breakpad