https://bugs.freedesktop.org/show_bug.cgi?id=108135
Bug ID: 108135
Summary: AVX instructions leak outside of CPU feature check and
cause SIGILL
Product: Mesa
Version: git
Hardware: Other
OS: All
Status: NEW
Severity: normal
Priority: medium
Component: Drivers/Gallium/swr
Assignee: mesa-dev@lists.freedesktop.org
Reporter: thi...@kde.org
QA Contact: mesa-dev@lists.freedesktop.org
Reported at https://github.com/clearlinux/distribution/issues/210
Symptom: when running certain applications (Xwayland in our case) on an Atom
CPU, the application crashes with SIGILL. The backtrace:
#7 _Z41__static_initialization_and_destruction_0ii.constprop.120() -
[swrast_dri.so] - lower_x86.cpp:73
#8 _GLOBAL__I_65535_0_gallium_dri_la_target.o.1657199() - [swrast_dri.so]
#9 call_init.part.0() - [ld-linux-x86-64.so.2] - dl-init.c:72
#10 _dl_init() - [ld-linux-x86-64.so.2] - dl-init.c:30
#11 dl_open_worker() - [ld-linux-x86-64.so.2] - dl-open.c:506
#12 _dl_catch_exception() - [libc.so.6] - dl-error-skeleton.c:196
#13 _dl_open() - [ld-linux-x86-64.so.2] - dl-open.c:588
#14 dlopen_doit() - [libdl.so.2] - dlopen.c:66
#15 _dl_catch_exception() - [libc.so.6] - dl-error-skeleton.c:196
#16 _dl_catch_error() - [libc.so.6] - dl-error-skeleton.c:215
#17 _dlerror_run() - [libdl.so.2] - dlerror.c:163
#18 dlopen@@GLIBC_2.2.5() - [libdl.so.2] - dlopen.c:87
#19 glxProbeDriver() - [/usr/bin/Xwayland] - glxdricommon.c:305
#20 __glXDRIscreenProbe() - [/usr/bin/Xwayland] - glxdriswrast.c:437
#21 xorgGlxServerInit() - [/usr/bin/Xwayland] - glxext.c:550
#22 _CallCallbacks() - [/usr/bin/Xwayland] - dixutils.c:737
#23 GlxExtensionInit() - [/usr/bin/Xwayland] - callback.h:83
#24 InitExtensions() - [/usr/bin/Xwayland] - miinitext.c:267
#25 dix_main() - [/usr/bin/Xwayland] - main.c:197
#26 __libc_start_main() - [libc.so.6] - libc-start.c:308
#27 _start() - [/usr/bin/Xwayland] - start.S:120
Investigation shows that the swrast_dri.so plugin contains AVX instructions
outside of a CPUID check in the "__static_initialization_and_destruction_0"
function. Further investigation shows some of those functions come from
src/gallium/drivers/swr/rasterizer/jitter/functionpasses/lower_x86.cpp, while
initialising the variable SwrJit::instructionMap (which is a global static
non-POD of type std::map - see
<https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/gallium/drivers/swr/rasterizer/jitter/functionpasses/lower_x86.cpp#L66>).
This lower_x86.cpp file is compiled with -mavx. This means the compiler is free
to generate AVX instructions anywhere in the file without a CPUID check,
including in the dynamic initialisation and destruction code that the std::map
variable requires.
The simplest solution I can think of, for this particular instruction, is to
change it from a global static to a local static. This will solve the problem
for this particular initialisation, but I think there are more variables with
this problem.
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