Fix stack alignment of child threads on ARM.

Fix stack alignment of child threads on ARM.

It is intended that a child thread starts with the stack pointer
aligned with 16-byte boundary, but it was misaligned by 4 bytes
on ARM due to pop instruction. This CL fixes it by using ldr
instruction instead.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4016
TEST=./scons bitcode=1 nonsfi_nacl=1 pnacl_generate_pexe=0 platform=arm \
         run_stack_alignment_asm_test
TEST=./scons bitcode=1 nonsfi_nacl=1 pnacl_generate_pexe=0 platform=arm \
         nonsfi_tests
TEST=./stack_alignment_asm_test.nexe  # On a real ARM machine
TEST=./thread_test.nexe  # On a real ARM machine

Committed: http://src.chromium.org/viewvc/native_client?view=rev&revision=14203

[mazda, 2014-12-10 10:48:26]

mazda@chromium.org changed reviewers:
+ hamaji@chromium.org, mseaborn@chromium.org

[mazda, 2014-12-10 10:48:26]

PTAL

[Mark Seaborn, 2014-12-10 16:28:21]

LGTM

https://codereview.chromium.org/722423003/diff/20001/src/nonsfi/linux/linux_p...
File src/nonsfi/linux/linux_pthread_private.c (right):

https://codereview.chromium.org/722423003/diff/20001/src/nonsfi/linux/linux_p...
src/nonsfi/linux/linux_pthread_private.c:98: * Load start_func from the stack
and call it.
Nit: Lower case "load"

[hamaji, 2014-12-11 01:37:39]

lgtm

Nice. Thanks for fixing this issue...

[mazda, 2014-12-11 03:41:49]

Thank you for the review.

https://codereview.chromium.org/722423003/diff/20001/src/nonsfi/linux/linux_p...
File src/nonsfi/linux/linux_pthread_private.c (right):

https://codereview.chromium.org/722423003/diff/20001/src/nonsfi/linux/linux_p...
src/nonsfi/linux/linux_pthread_private.c:98: * Load start_func from the stack
and call it.
On 2014/12/10 16:28:21, Mark Seaborn wrote:
> Nit: Lower case "load"

Done.

[mazda, 2014-12-11 03:42:28]

The CQ bit was checked by mazda@chromium.org

[commit-bot: I haz the power, 2014-12-11 03:42:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/722423003/40001

[commit-bot: I haz the power, 2014-12-11 16:16:57]

Committed patchset #3 (id:40001) as
http://src.chromium.org/viewvc/native_client?view=rev&revision=14203