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

Use PathService instead of command line flag to enable helper. Adds a nacl_helper_bootstrap executable that implements the actual space reservation.

This is for resubmit of reverted CL 7670011, fixing nacl.gypi for the linux_shared build.

See 7670011 and 7599011 for review history.

TBR=agl,bradnelson

BUG=92964, nativeclient:480
TEST=manual for now

Review URL: http://codereview.chromium.org/7655010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@97137 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/chrome_paths.cc

@@ -52,6 +52,12 @@ const FilePath::CharType kInternalNaClPluginFileName[] =
     FILE_PATH_LITERAL("libppGoogleNaClPluginChrome.so");
 #endif
 
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+// File name of the nacl_helper, Linux only.
+const FilePath::CharType kInternalNaClHelperFileName[] =
+    FILE_PATH_LITERAL("nacl_helper_bootstrap");
+#endif
+
 }  // namespace
 
 namespace chrome {
@@ -234,6 +240,13 @@ bool PathProvider(int key, FilePath* result) {
         return false;
       cur = cur.Append(kInternalNaClPluginFileName);
       break;
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+    case chrome::FILE_NACL_HELPER:
+      if (!PathService::Get(base::DIR_MODULE, &cur))
+        return false;
+      cur = cur.Append(kInternalNaClHelperFileName);
+      break;
+#endif
     case chrome::FILE_RESOURCES_PACK:
 #if defined(OS_MACOSX)
       if (base::mac::AmIBundled()) {

chrome/common/chrome_paths.h

@@ -40,7 +40,7 @@ enum {
                                 // using it.
   DIR_INTERNAL_PLUGINS,         // Directory where internal plugins reside.
   DIR_MEDIA_LIBS,               // Directory where the Media libraries reside.
-#if !defined(OS_MACOSX) && defined(OS_POSIX)
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
   DIR_POLICY_FILES,             // Directory for system-wide read-only
                                 // policy files that allow sys-admins
                                 // to set policies for chrome. This directory
@@ -68,6 +68,10 @@ enum {
   FILE_FLASH_PLUGIN,            // Full path to the internal Flash plugin file.
   FILE_PEPPER_FLASH_PLUGIN,     // Full path to the pepper Flash plugin file.
   FILE_PDF_PLUGIN,              // Full path to the internal PDF plugin file.
+
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+  FILE_NACL_HELPER,             // Full path to Linux nacl_helper executable.
+#endif
   FILE_NACL_PLUGIN,             // Full path to the internal NaCl plugin file.
   FILE_LIBAVCODEC,              // Full path to libavcodec media decoding
                                 // library.

chrome/nacl.gypi

@@ -144,10 +144,12 @@
         },
       ],
     }],
-    ['OS=="linux" and touchui == 0', {
+    ['OS=="linux"', {
       'targets': [
         {
-          'target_name': 'nacl_helper',
+          'target_name': 'nacl_helper.so',
+          # 'executable' will be overridden below when we add the -shared
+          # flag; here it prevents gyp from using the --whole-archive flag
           'type': 'executable',
           'include_dirs': [
             '..',
@@ -165,6 +167,35 @@
               ],
             }],
           ],
+          'link_settings': {
+            # NOTE: '-shared' overrides 'executable' above
+            'ldflags': ['-shared',
+                        '-Wl,--version-script=chrome/nacl/nacl_helper_exports.txt',
+                      ],
+          },
+        },
+        {
+          'target_name': 'nacl_helper_bootstrap',
+          'type': 'executable',
+          'dependencies': [
+            'nacl_helper.so',
+          ],
+          'sources': [
+            '../chrome/nacl/nacl_helper_bootstrap_linux.c',
+          ],
+          # TODO(bradchen): Delete the -B argument when Gold supports
+          # -Ttext properly. Until then use ld.bfd.
+          'link_settings': {
+            'ldflags': ['-B', 'tools/ld_bfd',
+                        # Force text segment at 0x10000 (64KB)
+                        # The max-page-size option is needed on x86-64 linux
+                        # where 4K pages are not the default in the BFD linker.
+                        '-Wl,-Ttext-segment,10000,-z,max-page-size=0x1000',
+                        # reference nacl_helper as a shared library
+                        '<(PRODUCT_DIR)/nacl_helper.so',
+                        '-Wl,-rpath,<(SHARED_LIB_DIR)',
+                      ],
+          },
         },
       ],
     }],

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
   }

chrome/nacl/nacl_helper_bootstrap_linux.c

+/* 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.
+ *
+ * Bootstraping the nacl_helper. This executable reserves the bottom 1G
+ * of the address space, then invokes nacl_helper_init. Note that,
+ * as the text of this executable will eventually be overwritten by the
+ * native_client module, nacl_helper_init must not attempt to return.
+ */
+
+#include <stdlib.h>
+
+/* reserve 1GB of space */
+#define ONEGIG (1 << 30)
+char nacl_reserved_space[ONEGIG];
+
+void nacl_helper_init(int argc, char *argv[],
+                      const char *nacl_reserved_space);
+
+int main(int argc, char *argv[]) {
+  nacl_helper_init(argc, argv, nacl_reserved_space);
+  abort();
+  return 0;  // convince the tools I'm sane.
+}

chrome/nacl/nacl_helper_exports.txt

+# gnu-ld version script for exporting desired symbols from nacl_helper
+#
+
+NACL_HELPER_1_0 {
+	global:
+		nacl_helper_init;
+		nacl_helper_get_1G_address;
+	local:
+		*;
+};

chrome/nacl/nacl_helper_linux.cc

@@ -116,14 +116,33 @@ void HandleForkRequest(const std::vector<int>& child_fds) {
 
 }  // namespace
 
-int main(int argc, char *argv[]) {
+static const void* g_nacl_reserved_space = NULL;
+extern "C" __attribute__((visibility("default")))
+const void* nacl_helper_get_1G_address() {
+  return g_nacl_reserved_space;
+}
+
+// nacl_helper_init does the real work of this module. It is invoked as
+// a static constructor and never returns, preventing main() from the
+// nacl_helper_bootstrap program from being called.
+//
+// NOTE This routine must not return.
+extern "C" __attribute__((visibility("default")))
+void nacl_helper_init(int argc, char *argv[],
+                      const char *nacl_reserved_space) {
   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"));
-
+  g_nacl_reserved_space = nacl_reserved_space;
+  if (!nacl_reserved_space) {
+    VLOG(1) << "nacl_reserved_space is NULL";
+  } else {
+    VLOG(1) << "nacl_reserved_space is at "
+            << (void *)nacl_reserved_space;
+  }
   // Send the zygote a message to let it know we are ready to help
   if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor,
                                  kNaClHelperStartupAck,
@@ -163,4 +182,5 @@ int main(int argc, char *argv[]) {
       LOG(ERROR) << "*** send() to zygote failed";
     }
   }
+  CHECK(false);  // This routine must not return
 }

tools/ld_bfd/ld

@@ -34,6 +34,8 @@ def main():
       continue
     if arg == "-Wl,--thread-count=4" or arg == "--thread-count=4":
       continue
+    if arg == "--icf=none":
+      continue
     args.append(arg)
   print("ld_bfd/ld: exec ", args)
   sys.exit(subprocess.call(args))