base/process/launch_fuchsia.cc

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/process/launch.h"

#include <tuple>

#include <lib/fdio/limits.h>
#include <lib/fdio/namespace.h>
#include <lib/fdio/spawn.h>
#include <lib/zx/job.h>
#include <stdint.h>
#include <unistd.h>
#include <zircon/processargs.h>

#include "base/command_line.h"
#include "base/files/file_util.h"
#include "base/fuchsia/default_job.h"
#include "base/fuchsia/file_utils.h"
#include "base/fuchsia/fuchsia_logging.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/process/environment_internal.h"
#include "base/scoped_generic.h"
#include "base/threading/scoped_blocking_call.h"
#include "base/trace_event/base_tracing.h"

namespace base {

namespace {

bool GetAppOutputInternal(const CommandLine& cmd_line,
                          bool include_stderr,
                          std::string* output,
                          int* exit_code) {
  DCHECK(exit_code);
  TRACE_EVENT0("base", "GetAppOutput");

  LaunchOptions options;

  // LaunchProcess will automatically clone any stdio fd we do not explicitly
  // map.
  int pipe_fd[2];
  if (pipe(pipe_fd) < 0)
    return false;
  options.fds_to_remap.emplace_back(pipe_fd[1], STDOUT_FILENO);
  if (include_stderr)
    options.fds_to_remap.emplace_back(pipe_fd[1], STDERR_FILENO);

  Process process = LaunchProcess(cmd_line, options);
  close(pipe_fd[1]);
  if (!process.IsValid()) {
    close(pipe_fd[0]);
    return false;
  }

  output->clear();
  for (;;) {
    char buffer[256];
    ssize_t bytes_read = read(pipe_fd[0], buffer, sizeof(buffer));
    if (bytes_read <= 0)
      break;
    output->append(buffer, static_cast<size_t>(bytes_read));
  }
  close(pipe_fd[0]);

  // It is okay to allow this process to wait on the launched process as a
  // process launched with GetAppOutput*() shouldn't wait back on the process
  // that launched it.
  internal::GetAppOutputScopedAllowBaseSyncPrimitives allow_wait;
  return process.WaitForExit(exit_code);
}

fdio_spawn_action_t FdioSpawnAction(uint32_t action) {
  fdio_spawn_action_t new_action = {};
  new_action.action = action;
  return new_action;
}

fdio_spawn_action_t FdioSpawnActionCloneFd(int local_fd, int target_fd) {
  fdio_spawn_action_t action = FdioSpawnAction(FDIO_SPAWN_ACTION_CLONE_FD);
  action.fd.local_fd = local_fd;
  action.fd.target_fd = target_fd;
  return action;
}

fdio_spawn_action_t FdioSpawnActionAddNamespaceEntry(const char* prefix,
                                                     zx_handle_t handle) {
  fdio_spawn_action_t action = FdioSpawnAction(FDIO_SPAWN_ACTION_ADD_NS_ENTRY);
  action.ns.prefix = prefix;
  action.ns.handle = handle;
  return action;
}

fdio_spawn_action_t FdioSpawnActionAddHandle(uint32_t id, zx_handle_t handle) {
  fdio_spawn_action_t action = FdioSpawnAction(FDIO_SPAWN_ACTION_ADD_HANDLE);
  action.h.id = id;
  action.h.handle = handle;
  return action;
}

fdio_spawn_action_t FdioSpawnActionSetName(const char* name) {
  fdio_spawn_action_t action = FdioSpawnAction(FDIO_SPAWN_ACTION_SET_NAME);
  action.name.data = name;
  return action;
}

}  // namespace

// static
uint32_t LaunchOptions::AddHandleToTransfer(
    HandlesToTransferVector* handles_to_transfer,
    zx_handle_t handle) {
  CHECK_LE(handles_to_transfer->size(), std::numeric_limits<uint16_t>::max())
      << "Number of handles to transfer exceeds total allowed";
  auto handle_id =
      static_cast<uint32_t>(PA_HND(PA_USER1, handles_to_transfer->size()));
  handles_to_transfer->push_back({handle_id, handle});
  return handle_id;
}

Process LaunchProcess(const CommandLine& cmdline,
                      const LaunchOptions& options) {
  return LaunchProcess(cmdline.argv(), options);
}

Process LaunchProcess(const std::vector<std::string>& argv,
                      const LaunchOptions& options) {
  // fdio_spawn_etc() accepts an array of |fdio_spawn_action_t|, describing
  // namespace entries, descriptors and handles to launch the child process
  // with. |fdio_spawn_action_t| does not own any values assigned to its
  // members, so strings assigned to members must be valid through the
  // fdio_spawn_etc() call.
  std::vector<fdio_spawn_action_t> spawn_actions;

  // Handles to be transferred to the child are owned by this vector, so that
  // they they are closed on early-exit, and can be release()d otherwise.
  std::vector<zx::handle> transferred_handles;

  // Add caller-supplied handles for transfer. We must do this first to ensure
  // that the handles are consumed even if some later step fails.
  for (const auto& id_and_handle : options.handles_to_transfer) {
    spawn_actions.push_back(
        FdioSpawnActionAddHandle(id_and_handle.id, id_and_handle.handle));
    transferred_handles.emplace_back(id_and_handle.handle);
  }

  // Determine the job under which to launch the new process.
  zx::unowned_job job = options.job_handle != ZX_HANDLE_INVALID
                            ? zx::unowned_job(options.job_handle)
                            : GetDefaultJob();
  DCHECK(job->is_valid());

  // Construct an |argv| array of C-strings from the supplied std::strings.
  std::vector<const char*> argv_cstr;
  argv_cstr.reserve(argv.size() + 1);
  for (const auto& arg : argv)
    argv_cstr.push_back(arg.c_str());
  argv_cstr.push_back(nullptr);

  // If |environment| is set then it contains values to set/replace to create
  // the new process' environment.
  EnvironmentMap environ_modifications = options.environment;

  // "PWD" is set in the new process' environment, to one of:
  // 1. The value of |current_directory|, if set.
  // 2. The value specified in |environment|, if any.
  // 3. The current process' current working directory, if known.
  if (!options.current_directory.empty()) {
    environ_modifications["PWD"] = options.current_directory.value();
  } else if (environ_modifications.find("PWD") == environ_modifications.end()) {
    FilePath cwd;
    if (GetCurrentDirectory(&cwd)) {
      environ_modifications["PWD"] = cwd.value();
    }
  }

  // By default the calling process' environment is copied, and the collated
  // modifications applied, to create the new process' environment. If
  // |clear_environment| is set then only the collated modifications are used.
  char* const kEmptyEnviron = nullptr;
  char* const* old_environ =
      options.clear_environment ? &kEmptyEnviron : environ;
  std::unique_ptr<char*[]> new_environ =
      internal::AlterEnvironment(old_environ, environ_modifications);

  // Always clone the library loader service and UTC clock to new processes,
  // in addition to any flags specified by the caller.
  uint32_t spawn_flags = FDIO_SPAWN_DEFAULT_LDSVC | FDIO_SPAWN_CLONE_UTC_CLOCK |
                         options.spawn_flags;

  // Add actions to clone handles for any specified paths into the new process'
  // namespace.
  if (!options.paths_to_clone.empty() || !options.paths_to_transfer.empty()) {
    DCHECK((options.spawn_flags & FDIO_SPAWN_CLONE_NAMESPACE) == 0);
    transferred_handles.reserve(transferred_handles.size() +
                                options.paths_to_clone.size() +
                                options.paths_to_transfer.size());

    for (const auto& path_to_transfer : options.paths_to_transfer) {
      zx::handle handle(path_to_transfer.handle);
      spawn_actions.push_back(FdioSpawnActionAddNamespaceEntry(
          path_to_transfer.path.value().c_str(), handle.get()));
      transferred_handles.push_back(std::move(handle));
    }

    for (const auto& path_to_clone : options.paths_to_clone) {
      fidl::InterfaceHandle<::fuchsia::io::Directory> directory =
          base::OpenDirectoryHandle(path_to_clone);
      if (!directory) {
        LOG(WARNING) << "Could not open handle for path: " << path_to_clone;
        return base::Process();
      }

      zx::handle handle = directory.TakeChannel();

      spawn_actions.push_back(FdioSpawnActionAddNamespaceEntry(
          path_to_clone.value().c_str(), handle.get()));
      transferred_handles.push_back(std::move(handle));
    }
  }

  // Add any file-descriptors to be cloned into the new process.
  // Note that if FDIO_SPAWN_CLONE_STDIO is set, then any stdio entries in
  // |fds_to_remap| will be used in place of the parent process' descriptors.
  for (const auto& src_target : options.fds_to_remap) {
    spawn_actions.push_back(
        FdioSpawnActionCloneFd(src_target.first, src_target.second));
  }

  // If |process_name_suffix| is specified then set process name as
  // "<file_name><suffix>", otherwise leave the default value.
  std::string process_name;  // Must outlive the fdio_spawn_etc() call.
  if (!options.process_name_suffix.empty()) {
    process_name = base::FilePath(argv[0]).BaseName().value() +
                   options.process_name_suffix;
    spawn_actions.push_back(FdioSpawnActionSetName(process_name.c_str()));
  }

  zx::process process_handle;
  // fdio_spawn_etc() will write a null-terminated scring to |error_message| in
  // case of failure, so we avoid unnecessarily initializing it here.
  char error_message[FDIO_SPAWN_ERR_MSG_MAX_LENGTH];
  zx_status_t status = fdio_spawn_etc(
      job->get(), spawn_flags, argv_cstr[0], argv_cstr.data(),
      new_environ.get(), spawn_actions.size(), spawn_actions.data(),
      process_handle.reset_and_get_address(), error_message);

  // fdio_spawn_etc() will close all handles specified in add-handle actions,
  // regardless of whether it succeeds or fails, so release our copies.
  for (auto& transferred_handle : transferred_handles)
    std::ignore = transferred_handle.release();

  if (status != ZX_OK) {
    ZX_LOG(ERROR, status) << "fdio_spawn: " << error_message;
    return Process();
  }

  // Wrap the handle into a Process, and wait for it to terminate, if requested.
  Process process(process_handle.release());
  if (options.wait) {
    status = zx_object_wait_one(process.Handle(), ZX_TASK_TERMINATED,
                                ZX_TIME_INFINITE, nullptr);
    ZX_DCHECK(status == ZX_OK, status) << "zx_object_wait_one";
  }

  return process;
}

bool GetAppOutput(const CommandLine& cl, std::string* output) {
  int exit_code;
  bool result = GetAppOutputInternal(cl, false, output, &exit_code);
  return result && exit_code == EXIT_SUCCESS;
}

bool GetAppOutput(const std::vector<std::string>& argv, std::string* output) {
  return GetAppOutput(CommandLine(argv), output);
}

bool GetAppOutputAndError(const CommandLine& cl, std::string* output) {
  int exit_code;
  bool result = GetAppOutputInternal(cl, true, output, &exit_code);
  return result && exit_code == EXIT_SUCCESS;
}

bool GetAppOutputAndError(const std::vector<std::string>& argv,
                          std::string* output) {
  return GetAppOutputAndError(CommandLine(argv), output);
}

bool GetAppOutputWithExitCode(const CommandLine& cl,
                              std::string* output,
                              int* exit_code) {
  // Contrary to GetAppOutput(), |true| return here means that the process was
  // launched and the exit code was waited upon successfully, but not
  // necessarily that the exit code was EXIT_SUCCESS.
  return GetAppOutputInternal(cl, false, output, exit_code);
}

void RaiseProcessToHighPriority() {
  // Fuchsia doesn't provide an API to change process priority.
}

}  // namespace base