A mechanism to identify/forbid/"rewrite" non-temporal instructions (and other)

src/trusted/validator_ragel/dfa_validate_common.c

 /*
  * Copyright (c) 2012 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.
  */
 
 /* Implement the functions common for ia32 and x86-64 architectures.  */
 #include "native_client/src/trusted/validator_ragel/dfa_validate_common.h"
 
 #include <string.h>
@@ skipping 15 matching lines @@
 Bool NaClDfaProcessValidationError(const uint8_t *begin, const uint8_t *end,
                                    uint32_t info, void *callback_data) {
   UNREFERENCED_PARAMETER(begin);
   UNREFERENCED_PARAMETER(end);
   UNREFERENCED_PARAMETER(info);
   UNREFERENCED_PARAMETER(callback_data);
 
   return FALSE;
 }
 
-Bool NaClDfaStubOutCPUUnsupportedInstruction(const uint8_t *begin,
-                                             const uint8_t *end,
-                                             uint32_t info,
-                                             void *callback_data) {
+Bool NaClDfaForbidOrRewriteInstruction(const uint8_t *begin,
+                                       const uint8_t *end,
+                                       uint32_t info,
+                                       void *callback_data) {
+  struct ForbidRewriteCallbackData *data = callback_data;

[Petr Hosek, 2015/07/20 23:58:57]

Shouldn't you doing a cast here? Is this actually compiling?

[ruiq, 2015/07/21 00:39:44]

This is valid in C, while not in C++. In C++, an explicit static_cast is needed.

[Petr Hosek, 2015/07/21 00:46:58]

I'd still include an explicit cast, even if this passes through compiler.

[ruiq, 2015/07/21 02:52:24]

I left this as it is: 1) It is not ambiguous; 2) it is cleaner and easier to
read, and not requiring a new line; 3) it is consistent with line 65.

   /* Stub-out instructions unsupported on this CPU, but valid on other CPUs.  */
   if ((info & VALIDATION_ERRORS_MASK) == CPUID_UNSUPPORTED_INSTRUCTION) {
-    int *did_stubout = callback_data;
-    *did_stubout = 1;
+    data->did_rewrite = 1;
     memset((uint8_t *)begin, NACL_HALT_OPCODE, end - begin);
     return TRUE;
+  } else if ((info & VALIDATION_ERRORS_MASK) == FORBID_OR_REWRITE_INSTRUCTION) {
+    if (data->pnacl_mode)
+      return FALSE;
+    else {
+      /* TODO: rewrite instruction. For now, we keep the original instruction

[Petr Hosek, 2015/07/20 23:58:57]

Nit: Please include your LDAP in the TODO, i.e. "TODO(ruiq)".

[ruiq, 2015/07/21 02:52:24]

Done.

+       * and indicate validation success, which is consistent with current
+       * validation results. */
+      data->did_rewrite = 1;
+      return TRUE;
+    }
   } else {
     return FALSE;
   }
 }
 
 Bool NaClDfaProcessCodeCopyInstruction(const uint8_t *begin_new,
                                        const uint8_t *end_new,
                                        uint32_t info_new,
                                        void *callback_data) {
   struct CodeCopyCallbackData *data = callback_data;
@@ skipping 12 matching lines @@
 
 Bool NaClDfaCodeReplacementIsStubouted(const uint8_t *begin_existing,
                                        size_t instruction_length) {
 
   /* Unsupported instruction must have been replaced with HLTs.  */
   if (memcmp(kStubOutMem, begin_existing, instruction_length) == 0)
     return TRUE;
   else
     return FALSE;
 }