[MIPS] Forbid $sp update at the end of the last bundle.

src/trusted/validator_mips/validator_tests.cc

Index: src/trusted/validator_mips/validator_tests.cc
diff --git a/src/trusted/validator_mips/validator_tests.cc b/src/trusted/validator_mips/validator_tests.cc
index a1dbc4f9d2522e41ae3b0348ea9d75bf544785be..502cce6c47f547fc90c255523237dee76666b8cb 100644
--- a/src/trusted/validator_mips/validator_tests.cc
+++ b/src/trusted/validator_mips/validator_tests.cc
@@ -43,6 +43,8 @@ using nacl_mips_dec::Instruction;
 using nacl_mips_val::SfiValidator;
 using nacl_mips_val::ProblemSink;
 using nacl_mips_val::CodeSegment;
+using nacl_mips_dec::kInstrSize;
+using nacl_mips_dec::kNop;
 
 namespace {
 
@@ -250,10 +252,6 @@ static const AnnotatedInstruction examples_of_safe_jumps[] = {
   { (10<<21|8),               "simple jump jr t2" },
 };
 
-static const AnnotatedInstruction nop_instruction[] = {
-  {  0, "nop"},
-};
-
 TEST_F(ValidatorTests, SafeMaskedJumps) {
   /*
    * Produces examples of masked jumps using the safe jump table
@@ -266,7 +264,7 @@ TEST_F(ValidatorTests, SafeMaskedJumps) {
               << ", "
               << examples_of_safe_jumps[s].about;
       mips_inst program[] = {
-        nop_instruction[0].inst,
+        kNop,
         examples_of_safe_jump_masks[m].inst,
         examples_of_safe_jumps[s].inst,
       };
@@ -357,7 +355,7 @@ TEST_F(ValidatorTests, IncorrectStackOps) {
       mips_inst bad_program[] = {
         examples_of_safe_stack_masks[m].inst,
         examples_of_safe_stack_ops[s].inst,
-        nop_instruction[0].inst
+        kNop
       };
 
       ValidationShouldFail(bad_program,
@@ -368,6 +366,16 @@ TEST_F(ValidatorTests, IncorrectStackOps) {
   }
 }
 
+TEST_F(ValidatorTests, UnmaskedSpUpdate) {

[JF, 2012/11/16 21:03:27]

Please also add a test for nop (as in the ARM change): otherwise the validator
might be failing because nop is disallowed and not because ending with sp update
is disallowed.

There is also a test in the ARM validator that the masked SP updates succeed.

[petarj, 2012/11/19 18:46:10]

Done.

+  vector<mips_inst> code(_validator.bytes_per_bundle()/kInstrSize, kNop);

[Mark Seaborn, 2012/11/16 20:08:08]

Nit: please put spaces around '/'

[petarj, 2012/11/19 18:46:10]

Done.

+  for (vector<mips_inst>::size_type i = 0; i < code.size(); ++i) {
+    std::fill(code.begin(), code.end(), kNop);
+    code[i] = 0x8fbd0000;  // lw $sp, 0($sp)
+    ValidationShouldFail(&code[0], code.size(), kDefaultBaseAddr,
+                         "unmasked SP update");
+  }
+}
+
 /*
  * Implementation of the ValidatorTests utility methods.  These are documented
  * toward the top of this file.