[MIPS] Make $t8 point to the address of TLS pointers

src/tools/tls_edit/tls_edit.c

 /*
  * Copyright (c) 2014 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.
  */
 
 /*
  * This alters instructions for the IRT so that access to the TLS
  * point to the IRT's TLS.
  */
@@ skipping 48 matching lines @@
       /*
        * This is 'ldr REG, [r9, #0]'.
        * Turn it into 'ldr REG, [r9, #4]'.
        */
       *insn |= 4;
       ++g_changes;
     }
   }
 }
 
+static void EditMipsCode(void *code, size_t code_length) {
+  Elf32_Word *const words = code;
+  Elf32_Word *const end = (void *) ((uint8_t *) code + code_length);
+  Elf32_Word *insn;
+
+  for (insn = words; insn < end; ++insn) {
+    if ((*insn & 0xFFE0FFFF) == 0x8f000000) {
+      /*
+       * This is 'lw $REG, 0($t8)'.
+       * Turn it into 'lw $REG, 4($t8)'.
+       */
+      *insn |= 4;
+      ++g_changes;
+    }
+  }
+}
+
 static Bool ConsiderOneInsn(const uint8_t *insn_begin, const uint8_t *insn_end,
                             uint32_t validation_info, void *data) {
   UNREFERENCED_PARAMETER(data);
   if (insn_begin[0] == 0x65) {  /* GS prefix */
     if (insn_end - insn_begin < 6) {
       ReportError(insn_begin, "Unexpected GS prefix");
     } else if (insn_end[-1] == 0 && insn_end[-2] == 0 &&
                insn_end[-3] == 0 && insn_end[-4] == 0) {
       /*
        * This is 'something %gs:0'.
@@ skipping 103 matching lines @@
     case EM_386:
       EditX86_32Code(g_code_start, code_length);
       break;
     case EM_X86_64:
       if (g_verbose) {
         printf("%s: x86-64 ELF detected, no instructions changed\n",
                infile);
       }
       return TRUE;
     case EM_MIPS:
-      if (g_verbose) {
-        printf("%s: MIPS ELF detected, no instructions changed\n",
-               infile);
-      }
+      EditMipsCode(g_code_start, code_length);
       return TRUE;
     default:
       fprintf(stderr, "%s: Unsupported e_machine %d\n",
               infile, e_machine);
       return FALSE;
   }
 
   if (g_verbose) {
     if (g_changes == 0) {
       printf("%s: Found no changes to make\n",
@@ skipping 182 matching lines @@
             infile);
     return 1;
   }
 
   if (g_errors != 0)
     return 1;
 
   WriteOutput(outfile);
   return 0;
 }