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// 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;
my_memcpy(path, "/proc/", 6);
my_itos(path + 6, pid, pid_len);
path[6 + pid_len] = '/';
my_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;
}
my_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);
}
sys_close(fd);
if (info->ppid == -1 || info->tgid == -1)
return false;
if (sys_ptrace(PTRACE_GETREGS, tid, NULL, &info->regs) == -1) {
return false;
}
if (sys_ptrace(PTRACE_GETFPREGS, tid, NULL, &info->fpregs) == -1) {
return false;
}
#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)
my_memcpy(&stack_pointer, &info->regs.esp, sizeof(info->regs.esp));
#elif defined(__x86_64)
my_memcpy(&stack_pointer, &info->regs.rsp, sizeof(info->regs.rsp));
#elif defined(__ARM_EABI__)
my_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
info->stack_pointer = reinterpret_cast<uintptr_t>(stack_pointer);
return true;
}
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.
my_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