Add flags for v2 sandbox to Chrome and Helper executable.

chrome/app/chrome_exe_main_mac.cc

 // Copyright 2015 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.
 
 // The entry point for all Mac Chromium processes, including the outer app
 // bundle (browser) and helper app (renderer, plugin, and friends).
 
 #include <dlfcn.h>
 #include <errno.h>
 #include <libgen.h>
@@ skipping 14 matching lines @@
 #include "sandbox/mac/seatbelt_exec.h"
 #endif  // defined(HELPER_EXECUTABLE)
 
 namespace {
 
 typedef int (*ChromeMainPtr)(int, char**);
 
 #if defined(HELPER_EXECUTABLE)
 // The command line parameter to engage the v2 sandbox.
 constexpr char v2_sandbox_arg[] = "--v2-sandbox";
+// The command line paramter indicating that the v2 sandbox is enabled. This
+// must be different than the "v2-sandbox" flag to avoid endless re-executing.
+// The flag tells the sandbox initialization code inside Chrome that the sandbox
+// should already be enabled.

[Charlie Reis, 2017/06/02 20:50:41]

Can you repeat this comment in content_switches.cc?  It's hard to understand why
both flags are needed there at the moment, without digging around.

[Greg K, 2017/06/02 23:59:02]

Done.

+// TODO(kerrnel): Remove this once the V2 sandbox migration is complete.
+constexpr char v2_sandbox_enabled_arg[] = "--v2-sandbox-enabled";
 // The command line parameter for the file descriptor used to receive the
 // sandbox policy.
 constexpr char fd_mapping_arg[] = "--fd_mapping=";
 
 __attribute__((noreturn)) void SandboxExec(const char* exec_path,
                                            int argc,
                                            char* argv[],
                                            int fd_mapping) {
   char rp[MAXPATHLEN];
   if (realpath(exec_path, rp) == NULL) {
@@ skipping 19 matching lines @@
     abort();
   }
 
   std::vector<char*> new_argv;
   for (int i = 1; i < argc; ++i) {
     if (strcmp(argv[i], v2_sandbox_arg) != 0 &&
         strncmp(argv[i], fd_mapping_arg, strlen(fd_mapping_arg)) != 0) {
       new_argv.push_back(argv[i]);
     }
   }
+  // Tell Chrome that the sandbox should already be enabled.
+  // Note that execv() is documented to treat the argv as constants, so the
+  // const_cast is safe.
+  new_argv.push_back(const_cast<char*>(v2_sandbox_enabled_arg));
   new_argv.push_back(nullptr);
 
   // The helper executable re-executes itself under the sandbox.
   execv(exec_path, new_argv.data());
   perror("execve");
   abort();
 }
 #endif  // defined(HELPER_EXECUTABLE)
 
 }  // namespace
@@ skipping 72 matching lines @@
   if (!chrome_main) {
     fprintf(stderr, "dlsym ChromeMain: %s\n", dlerror());
     abort();
   }
   rv = chrome_main(argc, argv);
 
   // exit, don't return from main, to avoid the apparent removal of main from
   // stack backtraces under tail call optimization.
   exit(rv);
 }