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

chrome/nacl/nacl_fork_delegate_linux.cc

Index: chrome/nacl/nacl_fork_delegate_linux.cc
diff --git a/chrome/nacl/nacl_fork_delegate_linux.cc b/chrome/nacl/nacl_fork_delegate_linux.cc
index 794cfdaed0ee09a22f955f1cb877af9f3d3da4a2..e5ee01a3c5168490811a5cf68c073557db4b5f40 100644
--- a/chrome/nacl/nacl_fork_delegate_linux.cc
+++ b/chrome/nacl/nacl_fork_delegate_linux.cc
@@ -13,9 +13,11 @@
 #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"
 
@@ -40,18 +42,24 @@ void NaClForkDelegate::Init(const bool sandboxed,
   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+    // program after it has been replaced by the nacl module.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
   }