sandbox/linux/services/scoped_process.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sandbox/linux/services/scoped_process.h"
   6
   7 #include <fcntl.h>
   8 #include <signal.h>
   9 #include <sys/stat.h>
  10 #include <sys/syscall.h>
  11 #include <sys/types.h>
  12 #include <sys/wait.h>
  13 #include <unistd.h>
  14
  15 #include "base/callback.h"
  16 #include "base/logging.h"
  17 #include "base/posix/eintr_wrapper.h"
  18 #include "build/build_config.h"
  19 #include "sandbox/linux/services/syscall_wrappers.h"
  20 #include "sandbox/linux/services/thread_helpers.h"
  21
  22 namespace sandbox {
  23
  24 namespace {
  25
  26 const char kSynchronisationChar[] = "D";
  27
  28 void WaitForever() {
  29   while(true) {
  30     pause();
  31   }
  32 }
  33
  34 }  // namespace
  35
  36 ScopedProcess::ScopedProcess(const base::Closure& child_callback)
  37     : child_process_id_(-1), process_id_(getpid()) {
  38   PCHECK(0 == pipe(pipe_fds_));
  39 #if !defined(THREAD_SANITIZER)
  40   // Make sure that we can safely fork().
  41   CHECK(ThreadHelpers::IsSingleThreaded());
  42 #endif
  43   child_process_id_ = fork();
  44   PCHECK(0 <= child_process_id_);
  45
  46   if (0 == child_process_id_) {
  47     PCHECK(0 == IGNORE_EINTR(close(pipe_fds_[0])));
  48     pipe_fds_[0] = -1;
  49     child_callback.Run();
  50     // Notify the parent that the closure has run.
  51     CHECK_EQ(1, HANDLE_EINTR(write(pipe_fds_[1], kSynchronisationChar, 1)));
  52     WaitForever();
  53     NOTREACHED();
  54     _exit(1);
  55   }
  56
  57   PCHECK(0 == IGNORE_EINTR(close(pipe_fds_[1])));
  58   pipe_fds_[1] = -1;
  59 }
  60
  61 ScopedProcess::~ScopedProcess() {
  62   CHECK(IsOriginalProcess());
  63   if (child_process_id_ >= 0) {
  64     PCHECK(0 == kill(child_process_id_, SIGKILL));
  65     siginfo_t process_info;
  66
  67     PCHECK(0 == HANDLE_EINTR(
  68                     waitid(P_PID, child_process_id_, &process_info, WEXITED)));
  69   }
  70   if (pipe_fds_[0] >= 0) {
  71     PCHECK(0 == IGNORE_EINTR(close(pipe_fds_[0])));
  72   }
  73   if (pipe_fds_[1] >= 0) {
  74     PCHECK(0 == IGNORE_EINTR(close(pipe_fds_[1])));
  75   }
  76 }
  77
  78 int ScopedProcess::WaitForExit(bool* got_signaled) {
  79   DCHECK(got_signaled);
  80   CHECK(IsOriginalProcess());
  81   siginfo_t process_info;
  82   // WNOWAIT to make sure that the destructor can wait on the child.
  83   int ret = HANDLE_EINTR(
  84       waitid(P_PID, child_process_id_, &process_info, WEXITED | WNOWAIT));
  85   PCHECK(0 == ret) << "Did something else wait on the child?";
  86
  87   if (process_info.si_code == CLD_EXITED) {
  88     *got_signaled = false;
  89   } else if (process_info.si_code == CLD_KILLED ||
  90              process_info.si_code == CLD_DUMPED) {
  91     *got_signaled = true;
  92   } else {
  93     CHECK(false) << "ScopedProcess needs to be extended for si_code "
  94                  << process_info.si_code;
  95   }
  96   return process_info.si_status;
  97 }
  98
  99 bool ScopedProcess::WaitForClosureToRun() {
 100   char c = 0;
 101   int ret = HANDLE_EINTR(read(pipe_fds_[0], &c, 1));
 102   PCHECK(ret >= 0);
 103   if (0 == ret)
 104     return false;
 105
 106   CHECK_EQ(c, kSynchronisationChar[0]);
 107   return true;
 108 }
 109
 110 // It would be problematic if after a fork(), another process would start using
 111 // this object.
 112 // This method allows to assert it is not happening.
 113 bool ScopedProcess::IsOriginalProcess() {
 114   // Make a direct syscall to bypass glibc caching of PIDs.
 115   pid_t pid = sys_getpid();
 116   return pid == process_id_;
 117 }
 118
 119 }  // namespace sandbox