[MIPS] Implementation of sel_ldr for MIPS architecture.

src/trusted/service_runtime/linux/nacl_bootstrap.c

 /*
  * 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.
  *
  * This is a standalone program that loads and runs the dynamic linker.
  * This program itself must be linked statically.  To keep it small, it's
  * written to avoid all dependencies on libc and standard startup code.
  * Hence, this should be linked using -nostartfiles.  It must be compiled
  * with -fno-stack-protector to ensure the compiler won't emit code that
@@ skipping 246 matching lines @@
       ehdr.e_phentsize != sizeof(ElfW(Phdr)))
     fail(filename, "File has no valid ELF header!", NULL, 0, NULL, 0);
 
   switch (ehdr.e_machine) {
 #if defined(__i386__)
     case EM_386:
 #elif defined(__x86_64__)
     case EM_X86_64:
 #elif defined(__arm__)
     case EM_ARM:
+#elif defined(__mips__)
+    case EM_MIPS:
 #else
 # error "Don't know the e_machine value for this architecture!"
 #endif
       break;
     default:
       fail(filename, "ELF file has wrong architecture!  ",
            "e_machine", ehdr.e_machine, NULL, 0);
       break;
   }
 
@@ skipping 383 matching lines @@
 #endif
     "mov fp, #0\n"
     "mov lr, #0\n"
     "mov r4, sp\n"              /* Save starting SP in r4.  */
     "mov r0, sp\n"              /* Argument: stack block.  */
     "bl do_load\n"
     "mov sp, r4\n"              /* Restore the saved SP.  */
     "blx r0\n"                  /* Jump to the entry point.  */
     ".popsection"
     );
+#elif defined(__mips__)
+  asm(".pushsection \".text\",\"ax\",%progbits\n"
+    ".globl _start\n"
+    ".type _start,@function\n"
+    "_start:\n"
+    ".set noreorder\n"
+    "addiu $fp, $zero, 0\n"
+    "addiu $ra, $zero, 0\n"
+    "addiu $s8, $sp,   0\n"     /* Save starting SP in s8.  */
+    "addiu $a0, $sp,   0\n"
+    "addiu $sp, $sp, -16\n"
+    "jal   do_load\n"
+    "nop\n"
+    "addiu $sp, $s8,  0\n"      /* Restore the saved SP.  */
+    "jr    $v0\n"               /* Jump to the entry point.  */
+    "nop\n"
+    ".popsection"
+    );
 #else
 # error "Need stack-preserving _start code for this architecture!"
 #endif
 
 #if defined(__arm__)
 /*
  * We may bring in __aeabi_* functions from libgcc that in turn
  * want to call raise.
  */
 int raise(int sig) {
   return sys_kill(sys_getpid(), sig);
 }
 #endif