Linux: refactor zygote support

http://code.google.com/p/chromium/wiki/LinuxZygote

* Move Chrome specific bits out of base
* Move away from the idea of reserved file descriptors (which don't
  really work with zygotes)
* Load resources before forking renderers (means that we don't need
  communication between the zygote process and the renderers)
* Make sure that gdb works against the browser again
* Make sure that we have different ASLR between the renderers and the
  browser.

http://codereview.chromium.org/119335


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18109 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 98 insertions, 0 deletions

diff --git a/base/unix_domain_socket_posix.cc b/base/unix_domain_socket_posix.cc
new file mode 100644
index 0000000..af7c0c3
--- /dev/null
+++ b/base/unix_domain_socket_posix.cc
@@ -0,0 +1,98 @@
+// Copyright (c) 2009 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 "base/unix_domain_socket_posix.h"
+
+#include <unistd.h>
+#include <sys/uio.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include "base/eintr_wrapper.h"
+#include "base/logging.h"
+
+namespace base {
+
+bool SendMsg(int fd, const void* buf, size_t length, std::vector<int>& fds) {
+  struct msghdr msg;
+  memset(&msg, 0, sizeof(msg));
+  struct iovec iov = {const_cast<void*>(buf), length};
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  char* control_buffer = NULL;
+  if (fds.size()) {
+    const unsigned control_len = CMSG_SPACE(sizeof(int) * fds.size());
+    control_buffer = new char[control_len];
+    if (!control_buffer)
+      return false;
+
+    struct cmsghdr *cmsg;
+
+    msg.msg_control = control_buffer;
+    msg.msg_controllen = control_len;
+    cmsg = CMSG_FIRSTHDR(&msg);
+    cmsg->cmsg_level = SOL_SOCKET;
+    cmsg->cmsg_type = SCM_RIGHTS;
+    cmsg->cmsg_len = CMSG_LEN(sizeof(int) * fds.size());
+    memcpy(CMSG_DATA(cmsg), &fds[0], sizeof(int) * fds.size());
+    msg.msg_controllen = cmsg->cmsg_len;
+  }
+
+  const ssize_t r = HANDLE_EINTR(sendmsg(fd, &msg, 0));
+  const bool ret = static_cast<ssize_t>(length) == r;
+  delete[] control_buffer;
+  return ret;
+}
+
+ssize_t RecvMsg(int fd, void* buf, size_t length, std::vector<int>* fds) {
+  static const unsigned kMaxDescriptors = 16;
+
+  fds->clear();
+
+  struct msghdr msg;
+  memset(&msg, 0, sizeof(msg));
+  struct iovec iov = {buf, length};
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  char control_buffer[CMSG_SPACE(sizeof(int) * kMaxDescriptors)];
+  msg.msg_control = control_buffer;
+  msg.msg_controllen = sizeof(control_buffer);
+
+  const ssize_t r = HANDLE_EINTR(recvmsg(fd, &msg, 0));
+  if (r == -1)
+    return -1;
+
+  int* wire_fds;
+  unsigned wire_fds_len = 0;
+
+  if (msg.msg_controllen > 0) {
+    struct cmsghdr* cmsg;
+    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+      if (cmsg->cmsg_level == SOL_SOCKET &&
+          cmsg->cmsg_type == SCM_RIGHTS) {
+        const unsigned payload_len = cmsg->cmsg_len - CMSG_LEN(0);
+        DCHECK(payload_len % sizeof(int) == 0);
+        wire_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
+        wire_fds_len = payload_len / sizeof(int);
+        break;
+      }
+    }
+  }
+
+  if (msg.msg_flags & MSG_TRUNC || msg.msg_flags & MSG_CTRUNC) {
+    for (unsigned i = 0; i < wire_fds_len; ++i)
+      close(wire_fds[i]);
+    errno = EMSGSIZE;
+    return -1;
+  }
+
+  fds->resize(wire_fds_len);
+  memcpy(&(*fds)[0], wire_fds, sizeof(int) * wire_fds_len);
+
+  return r;
+}
+
+}  // namespace base