[MIPS] Make validator allow only two load patterns via $t8

src/trusted/validator_mips/testdata/test_tp_access.S

+# Copyright 2015 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.
+
+# Several test cases are implemented in this file:
+#  1. Test if regular way to access thread pointers is allowed.
+#  2. Test different random examples of forbidden stores through $t8.
+#  3. Test different random examples of forbidden loads through $t8.
+
+
+   .align 4

[Mark Seaborn, 2015/12/27 03:46:35]

Nit: can you use a consistent indentation?  There's a mix of 2 and 3 spaces in
this file.

[petarj, 2015/12/28 14:07:00]

Done. More files in this directory could be modified the same way.

+   .globl __start
+__start:
+   .set noreorder
+   .set mips32r2
+
+  # Test valid tp access
+valid_load_access:
+  lw      $a0, 0($t8)            # OK
+  lw      $a0, 4($t8)            # OK
+  nop
+  nop
+
+  # Test invalid tp access
+invalid_store_access:
+  sb      $a0, 4($t8)            # Error, forbidden thread pointer access.
+  sc      $a0, 4($t8)            # Error, forbidden thread pointer access.
+  sdc1    $0, 4($t8)             # Error, forbidden thread pointer access.
+  sdc2    $8, 4($t8)             # Error, forbidden thread pointer access.
+
+  sh      $a0, 4($t8)            # Error, forbidden thread pointer access.
+  sw      $a0, 4($t8)            # Error, forbidden thread pointer access.
+  swc1    $f2, 4($t8)            # Error, forbidden thread pointer access.
+  swc2    $22, 4($t8)            # Error, forbidden thread pointer access.
+
+  swl     $a0, 4($t8)            # Error, forbidden thread pointer access.
+  swr     $a0, 4($t8)            # Error, forbidden thread pointer access.
+  sdxc1   $f6, $a2($t8)          # Error, forbidden instruction.
+  suxc1   $f4, $t8($t8)          # Error, forbidden instruction.
+
+  swxc1   $f4, $t8($t8)          # Error, forbidden instruction.
+  nop
+  nop
+  nop
+
+invalid_load_access:
+  lb      $a0, 4($t8)            # Error, forbidden thread pointer access.
+  lw      $a0, 8($t8)            # Error, forbidden thread pointer access.
+  lbu     $a0, 4($t8)            # Error, forbidden thread pointer access.
+  ldc1    $f0, 4($t8)            # Error, forbidden thread pointer access.
+
+  ldc2    $10, -24($t8)          # Error, forbidden thread pointer access.
+  lh      $a0, 4($t8)            # Error, forbidden thread pointer access.
+  lhu     $a0, 4($t8)            # Error, forbidden thread pointer access.
+  ll      $a0, 4($t8)            # Error, forbidden thread pointer access.
+
+  lwc1    $f0, 4($t8)            # Error, forbidden thread pointer access.
+  lwc2    $10, 4($t8)            # Error, forbidden thread pointer access.
+  lwl     $a0, 4($t8)            # Error, forbidden thread pointer access.
+  lwr     $a0, 4($t8)            # Error, forbidden thread pointer access.
+
+  ldxc1   $f0, $0($t8)           # Error, forbidden instruction.
+  luxc1   $f0, $a2($t8)          # Error, forbidden instruction.
+  lwxc1   $f6, $v0($t8)          # Error, forbidden instruction.
+  nop
+
+  .set dsp
+  lbux    $a3, $t2($t8)          # Error, forbidden instruction.
+  lhx     $a1, $a2($t8)          # Error, forbidden instruction.
+  lwx     $t1, $t2($t8)          # Error, forbidden instruction.
+  nop
+end_of_code: