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

src/trusted/validator_ragel/dfa_validate_common.c

Index: src/trusted/validator_ragel/dfa_validate_common.c
diff --git a/src/trusted/validator_ragel/dfa_validate_common.c b/src/trusted/validator_ragel/dfa_validate_common.c
index 330a0ce2c44fc128ff1f7736740f2da3b9f0d80a..0bf579790e59a7ac90626eac9fb4782b15289775 100644
--- a/src/trusted/validator_ragel/dfa_validate_common.c
+++ b/src/trusted/validator_ragel/dfa_validate_common.c
@@ -33,16 +33,26 @@ Bool NaClDfaProcessValidationError(const uint8_t *begin, const uint8_t *end,
   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;
   }