[Bug math/26534] New: libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[Bug math/26534] New: libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[ondra.hosek at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

            Bug ID: 26534
           Summary: libm.so 2.32 SIGILL in pow() due to FMA4 instruction
                    on non-FMA4 system
           Product: glibc
           Version: 2.32
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: ondra.hosek at gmail dot com
  Target Milestone: ---

Programs calling libm's pow() exit with SIGILL because it executes the FMA4
instruction

    vfmaddsd %xmm4,0x8(%rdx),%xmm6,%xmm0

on a system that does not support FMA4.

This is apparently due to a regression in commit
107e6a3c2212ba7a3a4ec7cae8d82d73f7c95d0b file
sysdeps/x86_64/fpu/multiarch/ifunc-fma4.h where the ifunc checks for "FMA"
instead of "FMA4".

Originally reported to Arch Linux: https://bugs.archlinux.org/task/67715

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[ondra.hosek at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

--- Comment #1 from Ondřej Hošek <ondra.hosek at gmail dot com> ---
Created attachment 12797
  --> https://sourceware.org/bugzilla/attachment.cgi?id=12797&action=edit
patch fixing the regression (correcting typo/backspace-o)

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hjl.tools at gmail dot com

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-08-25
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Ondřej Hošek from comment #1)
> Created attachment 12797 [details]
> patch fixing the regression (correcting typo/backspace-o)

Can you send it to the glibc mailing list?  Thanks.

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[ondra.hosek at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

--- Comment #3 from Ondřej Hošek <ondra.hosek at gmail dot com> ---
Patch sent to the mailing list:

https://sourceware.org/pipermail/libc-alpha/2020-August/117267.html

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[slyfox at inbox dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

Sergei Trofimovich <slyfox at inbox dot ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |slyfox at inbox dot ru

--- Comment #4 from Sergei Trofimovich <slyfox at inbox dot ru> ---
Gentoo also encountered it: https://bugs.gentoo.org/740110

Looks like patch was merged into master as:
https://sourceware.org/git/?p=glibc.git;a=patch;h=23af890b3f04e80da783ba64e6b6d94822e01d54

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[ondra.hosek at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

Ondřej Hošek <ondra.hosek at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #5 from Ondřej Hošek <ondra.hosek at gmail dot com> ---
Yup, and backported to the 2.32 branch in
https://sourceware.org/git/?p=glibc.git;a=commit;h=cebc01cbfd6c257f329e818b68bb1b2eef2afe09

I guess I can change the status to RESOLVED FIXED now...

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.33
              Flags|                            |security-
                 CC|                            |fweimer at redhat dot com

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[Bug math/26534] libm.so 2.32 SIGILL in pow() due to FMA4 instruction on non-FMA4 system

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26534

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://bugzilla.redhat.com
                   |                            |/show_bug.cgi?id=1918115

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