NDK x86 SSE memory misalignment [37119345]

Fixed

Bug

Status Update

No update yet.

Description

di...@gmail.com

created issue #1

Sep 12, 2016 02:26PM

We are facing reproducible app crashes on some x86 Android devices for an existing game. The engine code and the game code are written mostly in C++ and can be cross compiled for Windows, OSX, iOS and Android (arm, armabiv7, x86). The game is running fine on all platforms except on some Android x86 devices. On these devices the app crashes reproducible with:

signal 11 (SIGSEGV), code 128 (SI_KERNEL), fault addr 00000000

Debugging with gdb shows that the app fails due to a misalignment for instruction MOVAPS:

=> 0x79413b59 <+249>: movaps %xmm2,-0x58(%ebp)
ebp 0x79c676e4 0x79c676e4

The instruction MOVAPS requires 16 byte aligned data. Obviously -0x58(%ebp) is not aligned.

0x79c676e4 – 0x58 = 0x79C6768C

We are using NDK (ndk-build) and clang as compile tool chain. The error also happens with the GCC 4.9 compiler but on a different location.

Build system:
Windows 10 64 bit
NDK r12b
(android-ndk-r12b-windows-x86_64.zip)

Test Device:
Asus Memo Pad FHD 10
CPU Intel Atom Z2560 1.6GHz
Android 4.3
(also failed on a ASUS Fonepad but is working in x86 emulator)

Compiler settings general:
APP_ABI := x86
APP_STL := gnustl_static
APP_PLATFORM := android-9
LOCAL_CFLAGS += -Os –DNDEBUG
LOCAL_CFLAGS += -march=i686 -mtune=intel -mssse3 -mfpmath=sse -m32

Compiler Settings CLANG:
NDK_TOOLCHAIN_VERSION := clang

Compiler Settings GCC:
NDK_TOOLCHAIN_VERSION := 4.9

Please find the full gdb logs attached.

gdb_clang_debug.txt

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gdb_gcc49_release.txt

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Comments

[Deleted User] <[Deleted User]> #2Sep 12, 2016 04:03PM

Hi,

I suppose a workaround for your crash would be to use -mstackrealign.
Can you give it a try and confirm?

di...@gmail.com <di...@gmail.com> #3Sep 13, 2016 05:50AM

Hi Xavier,

You are correct. Recompilation with -mstackrealign fixes the problem. Tested with clang and gcc 4.9.

Shouldn't this option be enabled by default for x86 ABI?

xh...@novetys.com <xh...@novetys.com> #4Sep 13, 2016 07:27AM

[Comment deleted]

[Deleted User] <[Deleted User]> #5Sep 13, 2016 07:28AM

Thanks for the confirmation!

mstackrealign seems to have been removed for performance reasons.
but your report shows that x86 devices (pre-kitkat?) are still calling NDK code with non-16-byte-aligned stack, leading to crashes.
So yes, I agree that when compiling against android-9 (<=14?) platform, it should be the default.

ks...@google.com <ks...@google.com> Sep 14, 2016 12:05AM

Assigned to da...@google.com.

da...@google.com <da...@google.com> #6Sep 29, 2016 08:31PM

https://android-review.googlesource.com/281284

da...@google.com <da...@google.com> #7Sep 29, 2016 08:57PM

Marked as fixed.

Submitted to master, will be in r14.

da...@google.com <da...@google.com> #8Sep 29, 2016 09:05PM

Actually, this is low risk enough that I'm cherry-picking it into r13.

da...@google.com <da...@google.com> #9Oct 31, 2016 07:57PM

We're seeing this on newer devices too, so this flag is going to be applied to x86 regardless of target API level:

https://android-review.googlesource.com/c/297957/

da...@google.com <da...@google.com> #10Oct 31, 2016 07:57PM

da...@google.com <da...@google.com> #12Oct 31, 2016 08:01PM

jomof/chiur: The fix for this only affects ndk-build. I've asked srhines to update the Clang driver to always pass this for Android, but that won't land until r14 at the earliest. Do we want to apply this to gradle/cmake as well?

da...@google.com <da...@google.com> #13Oct 31, 2016 08:20PM

(I've fixed cmake as well:

https://android-review.googlesource.com/c/297957/)

ta...@gmail.com <ta...@gmail.com> #14Nov 1, 2016 02:10PM

Yes can confirm -mstackrealign fixes the problem (it was in merged

issue 36949180

)

da...@google.com <da...@google.com> #15Nov 1, 2016 02:24PM

Glad to hear it. This fix is partially applied in r13 (as long as you're targeting API 19 or lower), and the full thing will be in r14.