Reserve 1GB at the base of the address space of linux nacl_helper for Native Client module.

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/path_service.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_paths.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);
+  // TODO(bradchen): To make this the default for release builds,
+  // remove command line switch.
   ready_ = false;
-  if (nacl_zygote_exe.length() != 0) {
+  const bool use_helper = CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kNaClLinuxHelper);
+  FilePath helper_exe;
+  if (use_helper && PathService::Get(chrome::FILE_NACL_HELPER, &helper_exe)) {
     CommandLine::StringVector argv = CommandLine::ForCurrentProcess()->argv();
-    argv[0] = nacl_zygote_exe;
+    argv[0] = helper_exe.value();
     base::LaunchOptions options;
     options.fds_to_remap = &fds_to_map;
     options.clone_flags = CLONE_FS | SIGCHLD;
+    // LD_BIND_NOW forces non-lazy binding in the dynamic linker, to
+    // prevent the linker from trying to look at the text of the nacl_helper
+    // program after it has been replaced by the nacl module.
+    base::environment_vector env;
+    env.push_back(std::make_pair("LD_BIND_NOW", "1"));
+    options.environ = &env;
     ready_ = base::LaunchProcess(argv, options, NULL);
     // parent and error cases are handled below
   }
   if (HANDLE_EINTR(close(fds[1])) != 0)
     LOG(ERROR) << "close(fds[1]) failed";
   if (ready_) {
     const ssize_t kExpectedLength = strlen(kNaClHelperStartupAck);
     char buf[kExpectedLength];
 
     // Wait for ack from nacl_helper, indicating it is ready to help
@@ skipping 47 matching lines @@
 
 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;
 }