[MIPS] New pattern in validator to detect jumps/branches in delay slots.

src/trusted/validator_mips/validator.cc

 /*
  * 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.
  */
 
 #include <assert.h>
 #include "native_client/src/trusted/service_runtime/nacl_config.h"
 #include "native_client/src/trusted/validator_mips/validator.h"
 #include "native_client/src/include/nacl_macros.h"
@@ skipping 197 matching lines @@
       }
       out->ReportProblem(second.addr(), second.safety(),
                          kProblemUnsafeLoadStore);
       return PATTERN_UNSAFE;
       }
   }
   return NO_MATCH;
 }
 
 
+/*
+ * Checks if there is jump/branch in the delay slot.
+ */
+static PatternMatch CheckBranchInDelaySlot(const SfiValidator &sfi,
+                                   const DecodedInstruction &first,
+                                   const DecodedInstruction &second,
+                                   ProblemSink *out) {
+  UNREFERENCED_PARAMETER(sfi);
+  if (first.HasDelaySlot() && second.HasDelaySlot()) {
+    out->ReportProblem(second.addr(), second.safety(),
+                       kProblemBranchInDelaySlot);
+    return PATTERN_UNSAFE;
+  }
+  return NO_MATCH;
+}
+
+
 /*********************************************************
  * Pseudo-instruction patterns.
  *********************************************************/
 
 /*
  * Checks if a pseudo-instruction that starts with instr will cross bundle
  * border (i.e. if it starts in one and ends in second).
  * The exception to this rule are pseudo-instructions altering the data register
  * value (because mask is the second instruction).
  */
@@ skipping 183 matching lines @@
   //  Type for two-instruction pattern functions.
   typedef PatternMatch (*TwoInstPattern)(const SfiValidator &,
                                          const DecodedInstruction &first,
                                          const DecodedInstruction &second,
                                          ProblemSink *out);
   //  The list of patterns -- defined in static functions up top.
   static const TwoInstPattern two_inst_patterns[] = {
     &CheckJmpReg,
     &CheckDataRegisterUpdate,
     &CheckDataRegisterDslot,
-    &CheckLoadStore
+    &CheckLoadStore,
+    &CheckBranchInDelaySlot
   };
 
   bool complete_success = true;
 
   for (uint32_t i = 0; i < NACL_ARRAY_SIZE(two_inst_patterns); i++) {
     PatternMatch r = two_inst_patterns[i](*this, first, second, out);
     switch (r) {
       case NO_MATCH:
          break;
       case PATTERN_UNSAFE:
@@ skipping 51 matching lines @@
 DecodedInstruction::DecodedInstruction(uint32_t vaddr,
                                        Instruction inst,
                                        const ClassDecoder &decoder)
     : vaddr_(vaddr),
       inst_(inst),
       decoder_(&decoder),
       safety_(decoder.safety(inst_))
 {}
 
 }  // namespace