For Linux, create a ZygoteForkDelegate that uses the nacl_helper executable

chrome/nacl/nacl_fork_delegate_linux.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/common/nacl_fork_delegate_linux.h"
+
+#include <signal.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+
+#include "base/basictypes.h"
+#include "base/command_line.h"
+#include "base/eintr_wrapper.h"
+#include "base/logging.h"
+#include "base/file_path.h"
+#include "base/process_util.h"
+#include "content/common/unix_domain_socket_posix.h"
+#include "content/common/zygote_fork_delegate_linux.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/nacl_helper_linux.h"
+
+NaClForkDelegate::NaClForkDelegate()
+    : ready_(false),
+      sandboxed_(false),
+      fd_(-1) {}
+
+void NaClForkDelegate::Init(const bool sandboxed,
+                            const int browserdesc,
+                            const int sandboxdesc) {
+  VLOG(1) << "NaClForkDelegate::Init()";
+  int fds[2];
+
+  sandboxed_ = sandboxed;
+  // Confirm a couple hard-wired assumptions.
+  // The NaCl constants are from chrome/nacl/nacl_linux_helper.h
+  DCHECK(kNaClBrowserDescriptor == browserdesc);
+  DCHECK(kNaClSandboxDescriptor == sandboxdesc);
+
+  CHECK(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fds) == 0);
+  base::file_handle_mapping_vector fds_to_map;
+  fds_to_map.push_back(std::make_pair(fds[1], kNaClZygoteDescriptor));
+  fds_to_map.push_back(std::make_pair(sandboxdesc, kNaClSandboxDescriptor));
+  // TODO(bradchen): Before making this the default for release builds,
+  // replace command line switch with PathService::Get().
+  const std::string nacl_zygote_exe =
+      CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kNaClLinuxHelper);
+  ready_ = false;
+  if (nacl_zygote_exe.length() != 0) {
+    CommandLine::StringVector argv = CommandLine::ForCurrentProcess()->argv();
+    argv[0] = nacl_zygote_exe;
+    base::LaunchOptions options;
+    options.fds_to_remap = &fds_to_map;
+    options.clone_flags = CLONE_FS | SIGCHLD;
+    ready_ = base::LaunchProcess(argv, options, NULL);
+    // parent and error cases are handled below
+  }
+  HANDLE_EINTR(close(fds[1]));
+  if (ready_) {
+    const ssize_t kExpectedLength = strlen(kNaClHelperStartupAck);
+    char buf[kExpectedLength];
+
+    // Wait for ack from nacl_helper, indicating it is ready to help
+    const ssize_t nread = HANDLE_EINTR(read(fds[0], buf, sizeof(buf)));
+    if (nread == kExpectedLength &&
+        memcmp(buf, kNaClHelperStartupAck, nread) == 0) {
+      // all is well
+      fd_ = fds[0];
+      return;
+    }
+    LOG(ERROR) << "Bad NaCl helper startup ack (" << nread << " bytes)";
+  }
+  // TODO(bradchen): Make this LOG(ERROR) when the NaCl helper
+  // becomes the default.
+  ready_ = false;
+  fd_ = -1;
+  HANDLE_EINTR(close(fds[0]));
+}
+
+NaClForkDelegate::~NaClForkDelegate() {
+  HANDLE_EINTR(close(fd_));  // side effect: delegate process will terminate
+}
+
+bool NaClForkDelegate::CanHelp(const std::string& process_type) {
+  return (process_type == switches::kNaClLoaderProcess && ready_);
+}
+
+pid_t NaClForkDelegate::Fork(const std::vector<int>& fds) {
+  base::ProcessId naclchild;
+  VLOG(1) << "NaClForkDelegate::Fork";
+
+  DCHECK(fds.size() == kNaClParentFDIndex + 1);
+  if (!UnixDomainSocket::SendMsg(fd_, kNaClForkRequest,
+                                 strlen(kNaClForkRequest), fds)) {
+    LOG(ERROR) << "NaClForkDelegate::Fork: SendMsg failed";
+    return -1;
+  }
+  int nread = HANDLE_EINTR(read(fd_, &naclchild, sizeof(naclchild)));
+  if (nread != sizeof(naclchild)) {
+    LOG(ERROR) << "NaClForkDelegate::Fork: read failed";
+    return -1;
+  }
+  VLOG(1) << "nacl_child is " << naclchild << " (" << nread << " bytes)";
+  return naclchild;
+}
+
+bool NaClForkDelegate::AckChild(const int fd,
+                                const std::string& channel_switch) {
+  int nwritten = HANDLE_EINTR(write(fd, channel_switch.c_str(),
+                                    channel_switch.length()));
+  if (nwritten != static_cast<int>(channel_switch.length())) {
+    return false;
+  }
+  return true;
+}