[MIPS] Support for building tests for MIPS

[MIPS] Support for building tests for MIPS

This change includes set of small changes to enable building the tests
for MIPS.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=2275
TEST= ./scons hello_world --mode=nacl platform=mips32 --verbose


Committed: http://src.chromium.org/viewvc/native_client?view=rev&revision=10972

[petarj, 2013-03-12 00:12:53]

A subset of changes at
https://codereview.chromium.org/12256018/

[Mark Seaborn, 2013-03-12 00:39:28]

LGTM, thanks

https://codereview.chromium.org/12667019/diff/1/tests/syscall_return_sandboxi...
File tests/syscall_return_sandboxing/sandboxed_mips.S (right):

https://codereview.chromium.org/12667019/diff/1/tests/syscall_return_sandboxi...
tests/syscall_return_sandboxing/sandboxed_mips.S:37: nop                 /*
sandboxed (bundle aligned) return address */
This would be more robust as:

.p2align 4
  /* Expected return address */
  jmp done
  /*
   * We don't expect the syscall to return to the following unaligned
   * address or to align up to the bundle boundary after it.
   */
bad:
.p2align 4
  break /* Abort */

done:
  move $v0, 1 /* Indicate success */

With whatever tweaks you need to make this real MIPS assembly code. :-)

Otherwise, the test can accidentally pass if the syscall returns a non-zero
result, and it doesn't check whether NaCl aligns the address up or down.

[petarj, 2013-03-12 17:46:15]

Second patch set uploaded.

[Mark Seaborn, 2013-03-12 21:55:24]

LGTM

https://codereview.chromium.org/12667019/diff/18001/tests/syscall_return_sand...
File tests/syscall_return_sandboxing/sandboxed_mips.S (right):

https://codereview.chromium.org/12667019/diff/18001/tests/syscall_return_sand...
tests/syscall_return_sandboxing/sandboxed_mips.S:38: nop
FWIW, adding in ".p2align 4" as well makes this more robust against someone
changing this and accidentally getting the bundling wrong (e.g. by miscounting
the instructions or by not understanding your convention of grouping into
bundles using empty lines).

[commit-bot: I haz the power, 2013-03-12 22:32:33]

CQ is trying da patch. Follow status at
https://nativeclient-status.appspot.com/cq/petarj@mips.com/12667019/18001

[commit-bot: I haz the power, 2013-03-13 00:43:40]

Change committed as 10972