[NaCl SDK] Re-land "Added support for NaCl IO to use the IRT Extension API."

native_client_sdk/src/libraries/nacl_io/kernel_wrap.h

 // Copyright (c) 2012 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.
 
 #ifndef LIBRARIES_NACL_IO_KERNEL_WRAP_H_
 #define LIBRARIES_NACL_IO_KERNEL_WRAP_H_
 
 #include <assert.h>
 #include <signal.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <sys/fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 
 #include "nacl_io/ossignal.h"
 #include "nacl_io/ossocket.h"
 #include "nacl_io/ostypes.h"
 #include "nacl_io/osutime.h"
 #include "sdk_util/macros.h"
 
+// Curently enable NaCl IO IRT Extension when using arm glibc (which
+// only supports this method interception).
+#if defined(__native_client__) && defined(__GLIBC__) && defined(__arm__)
+# define NACL_IO_IRT_EXT 1
+#endif
+
 #if defined(__GLIBC__)
 #include <sys/cdefs.h>
 #define NOTHROW __THROW
 #else
 #define NOTHROW
 #endif
 
 // Most kernel intercept functions (ki_*) return -1 and set the global errno.
 // However, the IRT wrappers are expected to return errno on failure. These
 // macros are used in the wrappers to check that the ki_ function actually
@@ skipping 116 matching lines @@
 ssize_t sendmsg(int fd, const struct msghdr* msg, int flags);
 int setsockopt(int fd, int lvl, int optname, const void* optval, socklen_t len);
 int shutdown(int fd, int how);
 int socket(int domain, int type, int protocol);
 int socketpair(int domain, int type, int protocl, int* sv);
 #endif  // PROVIDES_SOCKET_API
 
 EXTERN_C_END
 
 #endif  // LIBRARIES_NACL_IO_KERNEL_WRAP_H_