New NaCl zygote implementation 2

chrome/browser/nacl_fork_delegate.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 <signal.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+
+#include "base/basictypes.h"
+#include "base/command_line.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.h"
+#include "chrome/browser/nacl_fork_delegate.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/nacl_helper_linux.h"
+
+NaClForkDelegate::NaClForkDelegate() : sandboxed_(false),
+                                       fd_(-1),
+                                       pid_(-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));
+
+  const char* nacl_zygote_exe = getenv("NACL_NEW_ZYGOTE");
+  pid_ = -1;
+  if (NULL != nacl_zygote_exe) {
+    CommandLine::StringVector argv = CommandLine::ForCurrentProcess()->argv();
+    argv[0] = nacl_zygote_exe;
+    base::LaunchAppWithClone(argv, fds_to_map, false, &pid_,

[agl, 2011/06/20 17:28:55]

This looks like Linux specific code. If so, the filename should have _linux at
the end.

Also, I must admit that I'm lost here. Where does this code run?

[Brad Chen, 2011/06/20 22:09:47]

I renamed the file to nacl/nacl_fork_delegate_linux.cc.

The code runs in the zygote. When the zygote wants to fork, it first asks the
delegate if it wants to implement fork. If the delegate says "no" then the
zygote does the fork itself. I've added an explanatory comment to the .h file as
I believe is the convention. If that doesn't seem like enough let me know. 

On 2011/06/20 17:28:55, agl wrote:

+                             CLONE_FS | SIGCHLD);
+  }
+  close(fds[1]);

[agl, 2011/06/20 17:28:55]

HANDLE_EINTR around this.

[Brad Chen, 2011/06/20 22:09:47]

Done.

+  if (pid_ > 0) {
+    const int kExpectedLength = sizeof(kNaClHelperStartupAck);

[agl, 2011/06/20 17:28:55]

s/int/size_t/

[Brad Chen, 2011/06/20 22:09:47]

Done.

+    char buf[kExpectedLength];
+
+    // Wait for ack from nacl_helper, indicating it is ready to help
+    int nread = read(fds[0], buf, sizeof(buf));
+    if (nread == kExpectedLength &&
+        memcmp(buf, kNaClHelperStartupAck, nread) == 0) {
+      // all is well
+      fd_ = fds[0];
+      return;
+    } else {
+      LOG(ERROR) << "Bad NaCl helper startup ack (" << nread << " bytes";
+    }
+  }
+  // TODO(bradchen): Make this LOG(ERROR) when the NaCl helper
+  // becomes the default.
+  VLOG(1) << "Could not launch NaCl helper";
+  pid_ = -1;
+  fd_ = -1;
+  close(fds[0]);

[agl, 2011/06/20 17:28:55]

HANDLE_EINTR

[Brad Chen, 2011/06/20 22:09:47]

Done.

+}
+
+NaClForkDelegate::~NaClForkDelegate() {
+  close(fd_);  // side effect: delegate process will terminate

[agl, 2011/06/20 17:28:55]

HANDLE_EINTR()

[Brad Chen, 2011/06/20 22:09:47]

Done.

+}
+
+bool NaClForkDelegate::CanHelp(const std::string& process_type) {
+  return (process_type == switches::kNaClLoaderProcess && (Pid() != -1));
+}
+
+pid_t NaClForkDelegate::Fork(const std::vector<int>& fds) {
+  base::ProcessId naclchild;
+  VLOG(1) << "NaClForkDelegate::Fork";
+
+  if (sandboxed_) {
+    DCHECK(fds.size() == kNaClParentFDIndex + 1);
+  } else {
+    DCHECK(fds.size() == kNaClBrowserFDIndex + 1);
+  }
+  if (!UnixDomainSocket::SendMsg(FD(), kNaClForkRequest,
+                                 sizeof(kNaClForkRequest), fds)) {
+    LOG(ERROR) << "NaClForkDelegate::Fork: SendMsg failed";
+    return -1;
+  }
+  int nread = 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;
+}