[MIPS] Implementation of sel_ldr for MIPS architecture.

SConstruct

 #! -*- python -*-
 # 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.
 
 import atexit
 import os
 import platform
 import subprocess
 import sys
@@ skipping 2241 matching lines @@
                          ])
     # /usr/lib makes sense for most configuration except this one
     # No ARM compatible libs can be found there.
     # So this just makes the command lines longer and sometimes results
     # in linker warnings referring to this directory.
     env.FilterOut(LIBPATH=['/usr/lib'])
 
   # get_plugin_dirname.cc has a dependency on dladdr
   env.Append(LIBS=['dl'])
 
+def SetupLinuxEnvMips(env):
+  jail = '${SCONSTRUCT_DIR}/toolchain/linux_mips-trusted'
+  if env.Bit('built_elsewhere'):
+    def FakeInstall(dest, source, env):
+      print 'Not installing', dest
+      # Replace build commands with no-ops
+    env.Replace(CC='true', CXX='true', LD='true',
+                AR='true', RANLIB='true', INSTALL=FakeInstall)
+    # Allow emulation on x86 hosts for testing built_elsewhere flag
+    if not platform.machine().startswith('mips'):
+      env.Replace(EMULATOR=jail + '/run_under_qemu_mips32')
+  else:
+    sys.path.append('tools/trusted_cross_toolchains')
+    from setup_mips32_trusted_toolchain import mips32_env
+    sys.path.pop()
+    # Allow env vars to override these settings, for what it's worth.
+    mips32_env = mips32_env.copy()
+    mips32_env.update(os.environ)
+    env.Replace(CC=mips32_env.get('MIPS32_CC', 'NO-MIPSEL-CC-SPECIFIED'),
+                CXX=mips32_env.get('MIPS32_CXX', 'NO-MIPSEL-CXX-SPECIFIED'),
+                LD=mips32_env.get('MIPS32_LD', 'NO-MIPSEL-LD-SPECIFIED'),
+                EMULATOR=mips32_env.get('MIPS32_EMU', ''),
+                ASFLAGS=[],
+                LIBPATH=['${LIB_DIR}',
+                mips32_env.get('MIPS32_LIB_DIR', '').split()],
+                LINKFLAGS=mips32_env.get('MIPS32_LINKFLAGS', ''),
+                )
+
+    env.Append(LIBS=['rt', 'dl', 'pthread'],
+                     CCFLAGS=['-EL', '-Wl,-EL', '-march=mips32r2'])
+
 def MakeLinuxEnv():
   linux_env = MakeUnixLikeEnv().Clone(
       BUILD_TYPE = '${OPTIMIZATION_LEVEL}-linux',
       BUILD_TYPE_DESCRIPTION = 'Linux ${OPTIMIZATION_LEVEL} build',
       tools = ['target_platform_linux'],
       # TODO(bradnelson): this should really be able to live in unix_like_env
       #                   but can't due to what the target_platform_x module is
       #                   doing.
       LINK = '$CXX',
   )
@@ skipping 18 matching lines @@
         LINKFLAGS = ['-m32', '-L/usr/lib32', ],
         )
   elif linux_env.Bit('build_x86_64'):
     linux_env.Prepend(
         CCFLAGS = ['-m64', ],
         LINKFLAGS = ['-m64', '-L/usr/lib64', ],
         )
   elif linux_env.Bit('build_arm'):
     SetupLinuxEnvArm(linux_env)
   elif linux_env.Bit('build_mips32'):
-    # TODO(petarj): Add support for MIPS.
-    pass
+    SetupLinuxEnvMips(linux_env)
   else:
     Banner('Strange platform: %s' % GetPlatform())
 
   # These are desireable options for every Linux platform:
   # _FORTIFY_SOURCE: general paranoia "hardening" option for library functions
   # -fPIE/-pie: create a position-independent executable
   # relro/now: "hardening" options for linking
   # noexecstack: ensure that the executable does not get a PT_GNU_STACK
   #              header that causes the kernel to set the READ_IMPLIES_EXEC
   #              personality flag, which disables NX page protection.
   linux_env.Prepend(
       CPPDEFINES=[['-D_FORTIFY_SOURCE', '2']],
       LINKFLAGS=['-pie', '-Wl,-z,relro', '-Wl,-z,now', '-Wl,-z,noexecstack'],
       )
   # The ARM toolchain has a linker that doesn't handle the code its
   # compiler generates under -fPIE.
-  if linux_env.Bit('build_arm'):
+  if linux_env.Bit('build_arm') or linux_env.Bit('build_mips32'):
     linux_env.Prepend(CCFLAGS=['-fPIC'])
     # TODO(mcgrathr): Temporarily punt _FORTIFY_SOURCE for ARM because
     # it causes a libc dependency newer than the old bots have installed.
     linux_env.FilterOut(CPPDEFINES=[['-D_FORTIFY_SOURCE', '2']])
   else:
     linux_env.Prepend(CCFLAGS=['-fPIE'])
 
   # We always want to use the same flags for .S as for .c because
   # code-generation flags affect the predefines we might test there.
   linux_env.Replace(ASFLAGS=['${CCFLAGS}'])
@@ skipping 946 matching lines @@
   nacl_env.ValidateSdk()
 
 if BROKEN_TEST_COUNT > 0:
   msg = "There are %d broken tests." % BROKEN_TEST_COUNT
   if GetOption('brief_comstr'):
     msg += " Add --verbose to the command line for more information."
   print msg
 
 # separate warnings from actual build output
 Banner('B U I L D - O U T P U T:')