Plumb executable flag through proxy to base::SharedMemory::Create.

base::SharedMemory now takes a flag for whether executability is required.
Plumb that through the Linux-only proxy for this interface.

BUG= http://code.google.com/p/chromium/issues/detail?id=103377
TEST= nacl still works

R=mseaborn@chromium.org,jam@chromium.org

Review URL: http://codereview.chromium.org/8776053

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112818 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/render_sandbox_host_linux.cc

@@ -373,12 +373,14 @@ class SandboxIPCProcess  {
 
   void HandleMakeSharedMemorySegment(int fd, const Pickle& pickle, void* iter,
                                      std::vector<int>& fds) {
-    uint32_t shm_size;
-    if (!pickle.ReadUInt32(&iter, &shm_size))
+    base::SharedMemoryCreateOptions options;
+    if (!pickle.ReadUInt32(&iter, &options.size))
+      return;
+    if (!pickle.ReadBool(&iter, &options.executable))
       return;
     int shm_fd = -1;
     base::SharedMemory shm;
-    if (shm.CreateAnonymous(shm_size))
+    if (shm.Create(options))
       shm_fd = shm.handle().fd;
     Pickle reply;
     SendRendererReply(fds, reply, shm_fd);

content/common/child_process_sandbox_support_impl_linux.cc

@@ -91,6 +91,7 @@ int MakeSharedMemorySegmentViaIPC(size_t length, bool executable) {
   Pickle request;
   request.WriteInt(LinuxSandbox::METHOD_MAKE_SHARED_MEMORY_SEGMENT);
   request.WriteUInt32(length);
+  request.WriteBool(executable);
   uint8_t reply_buf[10];
   int result_fd;
   ssize_t result = UnixDomainSocket::SendRecvMsg(GetSandboxFD(),

content/public/common/child_process_sandbox_support_linux.h

@@ -13,9 +13,13 @@
 
 namespace content {
 
-// Returns a file descriptor for a shared memory segment.
-// The second argument is ignored because SHM segments are always
-// mappable with PROT_EXEC on Linux.
+// Returns a file descriptor for a shared memory segment.  The
+// executable flag indicates that the caller intends to use mprotect
+// with PROT_EXEC after making a mapping, but not that it intends to
+// mmap with PROT_EXEC in the first place.  (Some systems, such as
+// ChromeOS, disallow PROT_EXEC in mmap on /dev/shm files but do allow
+// PROT_EXEC in mprotect on mappings from such files.  This function
+// can yield an object that has that constraint.)
 CONTENT_EXPORT int MakeSharedMemorySegmentViaIPC(size_t length,
                                                  bool executable);