[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 22 matching lines @@
   return (uint32_t) ((uint8_t *) insn - g_code_start) + g_code_addr;
 }
 
 static void ReportError(const void *insn, const char *message) {
   uint32_t insn_addr = GetInsnAddr(insn);
 
   fprintf(stderr, "%#x: %s\n", (unsigned int) insn_addr, message);
   ++g_errors;
 }
 
+static void EditMipsCode(void *code, size_t code_length) {

[Mark Seaborn, 2016/01/11 22:19:28]

Nit: can you order this after EditArmCode()?

[petarj, 2016/01/11 23:21:38]

Done.

+  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 void EditArmCode(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 == NACL_INSTR_ARM_LITERAL_POOL_HEAD) {
       if ((insn - words) % 4 != 0) {
         ReportError(insn, "Roadblock not at start of bundle");
       } else {
@@ skipping 129 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;
 }