Report EMSGSIZE when appropriate for sendmsg

src/trusted/service_runtime/nacl_syscall_common.c

 /*
  * Copyright 2008 The Native Client Authors.  All rights reserved.
  * Use of this source code is governed by a BSD-style license that can
  * be found in the LICENSE file.
  */
 
 /*
  * NaCl service run-time, non-platform specific system call helper routines.
  */
 #include <sys/types.h>
@@ skipping 1713 matching lines @@
 
   ssize_retval = NaClImcSendTypedMessage(ndp, &kern_msg_hdr, flags);
 
   if (NaClIsNegErrno(ssize_retval)) {
     /*
      * NaClWouldBlock uses TSD (for both the errno-based and
      * GetLastError()-based implementations), so this is threadsafe.
      */
     if (0 != (flags & NACL_DONT_WAIT) && NaClWouldBlock()) {
       retval = -NACL_ABI_EAGAIN;
+    } else if (-NACL_ABI_EMSGSIZE == ssize_retval) {
+      /*
+       * Allow the caller to handle the case when imc_sendmsg fails because
+       * the message is too large for the system to send in one piece.
+       */
+      retval = -NACL_ABI_EMSGSIZE;
     } else {
       /*
        * TODO(bsy): the else case is some mysterious internal error.
        * Should we destroy the ndp or otherwise mark it as bad?  Was
        * the failure atomic?  Did it send some partial data?  Linux
        * implementation appears okay.
        */
       retval = -NACL_ABI_EIO;
     }
   } else if (ssize_retval > INT32_MAX || ssize_retval < INT32_MIN) {
@@ skipping 990 matching lines @@
                                 void                  *code_target,
                                 void                  *code_buffer,
                                 size_t                code_size) {
   UNREFERENCED_PARAMETER(natp);
   UNREFERENCED_PARAMETER(code_target);
   UNREFERENCED_PARAMETER(code_buffer);
   UNREFERENCED_PARAMETER(code_size);
 
   return -NACL_ABI_ENOSYS;
 }