Revert 90805 - I am submitting this with LGTMs from agl@ and evanm@. I'm marking this as TBR=jam@...

chrome/nacl/nacl_helper_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.
-
-// A mini-zygote specifically for Native Client.
-
-#include "chrome/common/nacl_helper_linux.h"
-
-#include <errno.h>
-#include <stdlib.h>
-#include <sys/socket.h>
-#include <sys/types.h>
-
-#include <string>
-#include <vector>
-
-#include "base/at_exit.h"
-#include "base/eintr_wrapper.h"
-#include "base/logging.h"
-#include "base/message_loop.h"
-#include "base/rand_util.h"
-#include "chrome/nacl/nacl_listener.h"
-#include "content/common/main_function_params.h"
-#include "content/common/unix_domain_socket_posix.h"
-#include "ipc/ipc_switches.h"
-
-namespace {
-
-bool g_suid_sandbox_active;
-
-// The child must mimic the behavior of zygote_main_linux.cc on the child
-// side of the fork. See zygote_main_linux.cc:HandleForkRequest from
-//   if (!child) {
-// Note: this code doesn't attempt to support SELINUX or the SECCOMP sandbox.
-void BecomeNaClLoader(const std::vector<int>& child_fds) {
-  VLOG(1) << "NaCl loader: setting up IPC descriptor";
-  if (HANDLE_EINTR(close(kNaClZygoteDescriptor)) < 0)
-    LOG(ERROR) << "close failed: " << errno;
-
-  // Set up browser descriptor as expected by Chrome on fd 3
-  // The zygote takes care of putting the sandbox IPC channel on fd 5
-  int zfd = dup2(child_fds[kNaClBrowserFDIndex], kNaClBrowserDescriptor);
-  if (zfd != kNaClBrowserDescriptor) {
-    LOG(ERROR) << "Could not initialize kNaClBrowserDescriptor";
-    _exit(-1);
-  }
-
-  MessageLoopForIO main_message_loop;
-  NaClListener *listener = new NaClListener();
-  listener->Listen();
-  _exit(0);
-}
-
-// Some of this code was lifted from
-// content/browser/zygote_main_linux.cc:ForkWithRealPid()
-void HandleForkRequest(const std::vector<int>& child_fds) {
-  VLOG(1) << "nacl_helper: forking";
-  pid_t childpid = fork();
-  if (childpid < 0) {
-    perror("fork");
-    LOG(ERROR) << "*** HandleForkRequest failed\n";
-    // fall through to parent case below
-  } else if (childpid == 0) {  // In the child process.
-    bool validack = false;
-    const size_t kMaxReadSize = 1024;
-    char buffer[kMaxReadSize];
-    // Wait until the parent process has discovered our PID.  We
-    // should not fork any child processes (which the seccomp
-    // sandbox does) until then, because that can interfere with the
-    // parent's discovery of our PID.
-    const int nread = HANDLE_EINTR(read(child_fds[kNaClParentFDIndex], buffer,
-                                        kMaxReadSize));
-    const std::string switch_prefix = std::string("--") +
-        switches::kProcessChannelID + std::string("=");
-    const size_t len = switch_prefix.length();
-
-    if (nread < 0) {
-      perror("read");
-      LOG(ERROR) << "read returned " << nread;
-    } else if (nread > static_cast<int>(len)) {
-      if (switch_prefix.compare(0, len, buffer, 0, len) == 0) {
-        VLOG(1) << "NaCl loader is synchronised with Chrome zygote";
-        CommandLine::ForCurrentProcess()->AppendSwitchASCII(
-            switches::kProcessChannelID,
-            std::string(&buffer[len], nread - len));
-        validack = true;
-      }
-    }
-    if (HANDLE_EINTR(close(child_fds[kNaClDummyFDIndex])))
-      LOG(ERROR) << "close failed: " << errno;
-    if (HANDLE_EINTR(close(child_fds[kNaClParentFDIndex])))
-      LOG(ERROR) << "close failed: " << errno;
-
-    if (validack) {
-      BecomeNaClLoader(child_fds);
-    } else {
-      LOG(ERROR) << "Failed to synch with zygote";
-    }
-    // NOTREACHED
-    return;
-  }
-  // I am the parent.
-  // First, close the dummy_fd so the sandbox won't find me when
-  // looking for the child's pid in /proc. Also close other fds.
-  for (size_t i = 0; i < child_fds.size(); i++) {
-    if (HANDLE_EINTR(close(child_fds[i])))
-      LOG(ERROR) << "close failed: " << errno;
-  }
-  VLOG(1) << "nacl_helper: childpid is " << childpid;
-  // Now tell childpid to the Chrome zygote.
-  if (HANDLE_EINTR(send(kNaClZygoteDescriptor,
-                        &childpid, sizeof(childpid), MSG_EOR))
-      != sizeof(childpid)) {
-    LOG(ERROR) << "*** send() to zygote failed";
-  }
-}
-
-}  // namespace
-
-int main(int argc, char *argv[]) {
-  CommandLine::Init(argc, argv);
-  base::AtExitManager exit_manager;
-  base::RandUint64();  // acquire /dev/urandom fd before sandbox is raised
-  std::vector<int> empty; // for SendMsg() calls
-
-  g_suid_sandbox_active = (NULL != getenv("SBX_D"));
-
-  // Send the zygote a message to let it know we are ready to help
-  if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor,
-                                 kNaClHelperStartupAck,
-                                 sizeof(kNaClHelperStartupAck), empty)) {
-    LOG(ERROR) << "*** send() to zygote failed";
-  }
-
-  while (true) {
-    int badpid = -1;
-    std::vector<int> fds;
-    static const unsigned kMaxMessageLength = 2048;
-    char buf[kMaxMessageLength];
-    const ssize_t msglen = UnixDomainSocket::RecvMsg(kNaClZygoteDescriptor,
-                                                     &buf, sizeof(buf), &fds);
-    if (msglen == 0 || (msglen == -1 && errno == ECONNRESET)) {
-      // EOF from the browser. Goodbye!
-      _exit(0);
-    }
-    if (msglen == sizeof(kNaClForkRequest) - 1 &&
-        memcmp(buf, kNaClForkRequest, msglen) == 0) {
-      if (kNaClParentFDIndex + 1 == fds.size()) {
-        HandleForkRequest(fds);
-        continue;  // fork succeeded. Note: child does not return
-      } else {
-        LOG(ERROR) << "nacl_helper: unexpected number of fds, got "
-                   << fds.size();
-      }
-    } else {
-      if (msglen != 0) {
-        LOG(ERROR) << "nacl_helper unrecognized request: %s";
-        _exit(-1);
-      }
-    }
-    // if fork fails, send PID=-1 to zygote
-    if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor, &badpid,
-                                   sizeof(badpid), empty)) {
-      LOG(ERROR) << "*** send() to zygote failed";
-    }
-  }
-}