[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

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https://bugs.freedesktop.org/show_bug.cgi?id=108135

GitLab Migration User  changed:

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 Status|NEW |RESOLVED

--- Comment #8 from GitLab Migration User  ---
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been
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You can subscribe and participate further through the new bug through this link
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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #7 from Thiago Macieira  ---
You can scan for .o that have initialisers by searching for .init_array
sections

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #6 from Kenneth Graunke  ---
This does point out an even more serious issue though:

Megadrivers interacts very badly with drivers that have global C++
initializers.  When dlopen'ing a DRI driver, C++ global constructors will run
for ANY driver that is built in, even if that isn't the driver the user is
trying to use.

In other words, let's say you're on a Raspberry Pi and are trying to use the
vc4 driver.  If your distro happens to have built SWR, then you'll end up
running a bunch of SWR C++ constructors...when trying to dlopen
vc4_dri.so...because both live in the same .so file.

Such global initialization really ought to happen at driver screen init time,
not dlopen time.  IMO we should forbid C++ global objects in Mesa drivers.  (We
have a few in the compiler, but everybody uses the compiler.)  I don't know how
feasible that is, though.  If it isn't, maybe we need to exclude such drivers
from the megadrivers mechanism...

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #5 from Thiago Macieira  ---
Please note that Clear was affected by this GCC bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87522. HJ is on it. It affects
LTO.

However, there's still one load-time initialisation left even without LTO.
That's a showstopper for all distributions: they simply can't turn SWR on. If
we want SWR to be used, that needs to be solved.

I'm working on a different solution for Clear, but it won't apply to other
Linux distributions.

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

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https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #4 from Alok Hota  ---
Hi Thiago,

Thanks for taking such a deep look into this. We probably shouldn't need to be
specifically targeting a specific architecture in the jitter. We may be able to
fix this by tweaking the build system.

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

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https://bugs.freedesktop.org/show_bug.cgi?id=108135

Alok Hota  changed:

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   Assignee|timothy.o.row...@intel.com  |alok.h...@intel.com

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #3 from Thiago Macieira  ---
(In reply to Thiago Macieira from comment #2)
> The patch does solve the problem for the particular file, but there are more
> AVX uses in swrast_dri.so. The next issue is the intialisation of the
> builtin types in src/compiler/glsl_types.cpp, caused by:

I believe that's a red herring. It's caused by our use of -flto in the build,
meaning the use of AVX in one place "spills" to surrounding code that is
otherwise innocent.

Without -flto, the next instruction to crash happens inside
GlobalKnobs::GlobalKnobs(). I see this function (in fact, the entire
gen_knobs.cpp file) present in at least two libraries: libmesaswr and
libswrAVX. That is,
both./src/gallium/drivers/swr/rasterizer/codegen/.libs/libmesaswr_la-gen_knobs.o
and ./src/gallium/drivers/swr/rasterizer/codegen/.libs/libswrAVX_la-gen_knobs.o
exist and contain this function. And BOTH files have AVX instructions. I can
see the -mavx flag in the build.

Was this intended?

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #2 from Thiago Macieira  ---
The patch does solve the problem for the particular file, but there are more
AVX uses in swrast_dri.so. The next issue is the intialisation of the builtin
types in src/compiler/glsl_types.cpp, caused by:

#define DECL_TYPE(NAME, ...)\
   const glsl_type glsl_type::_##NAME##_type = glsl_type(__VA_ARGS__, #NAME); \
   const glsl_type *const glsl_type::NAME##_type = _type::_##NAME##_type;

#define STRUCT_TYPE(NAME)

#include "compiler/builtin_type_macros.h"

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

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https://bugs.freedesktop.org/show_bug.cgi?id=108135

--- Comment #1 from Thiago Macieira  ---
Created attachment 141840
  --> https://bugs.freedesktop.org/attachment.cgi?id=141840=edit
Attempt at making the variables local static

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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

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
).

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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[Mesa-dev] [Bug 108135] AVX instructions leak outside of CPU feature check and cause SIGILL

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=108135

Thiago Macieira  changed:

   What|Removed |Added

   Assignee|mesa-dev@lists.freedesktop. |timothy.o.row...@intel.com
   |org |

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