[Bug libc/27511] New: S390 memmove assumes Vector Facility when MIE Facility 3 is present

[Bug libc/27511] New: S390 memmove assumes Vector Facility when MIE Facility 3 is present

[ian at iarosh dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27511

            Bug ID: 27511
           Summary: S390 memmove assumes Vector Facility when MIE Facility
                    3 is present
           Product: glibc
           Version: 2.32
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: ian at iarosh dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

glibc-2.32\sysdeps\s390\memmove.c contains:-

s390_libc_ifunc_expr (__redirect_memmove, memmove,
          ({
      s390_libc_ifunc_expr_stfle_init ();
      (HAVE_MEMMOVE_ARCH13
       && S390_IS_ARCH13_MIE3 (stfle_bits))
        ? MEMMOVE_ARCH13
        : (HAVE_MEMMOVE_Z13 && (hwcap & HWCAP_S390_VX))
        ? MEMMOVE_Z13
        : MEMMOVE_DEFAULT;
          })
          )

If S390_IS_ARCH13_MIE3 is on (i.e. Miscellaneous-Instruction-Extensions
Facility 3 is installed) the function MEMMOVE_ARCH13 is called, which contains
Vector Facility instructions. As the Vector Facility is optional,
MEMMOVE_ARCH13 abends with an Operation Exception.

The problem could be avoided if the code was changed to:

s390_libc_ifunc_expr (__redirect_memmove, memmove,
          ({
      s390_libc_ifunc_expr_stfle_init ();
      (HAVE_MEMMOVE_ARCH13 && (hwcap & HWCAP_S390_VX)
       && S390_IS_ARCH13_MIE3 (stfle_bits))
        ? MEMMOVE_ARCH13
        : (HAVE_MEMMOVE_Z13 && (hwcap & HWCAP_S390_VX))
        ? MEMMOVE_Z13
        : MEMMOVE_DEFAULT;
          })
          )

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[Bug libc/27511] S390 memmove assumes Vector Facility when MIE Facility 3 is present

[stli at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27511

Stefan Liebler <stli at linux dot ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-03-23
                 CC|                            |stli at linux dot ibm.com
           Assignee|unassigned at sourceware dot org   |stli at linux dot ibm.com

--- Comment #1 from Stefan Liebler <stli at linux dot ibm.com> ---
Thanks Ian,

you are right, if vector support is not present, this leads to an exception.
This is e.g. observable if you are booting with "novx" kernel-parameter on a
z15 or if you e.g. running on a zVM guest with an older zVM which has no
support for vector registers. I think some valgrind versions are also disabling
the vector HWCAPs, but not the stfle bits.

Which environment / distro are you using which leads to this exception?

I've just posted this patch:
[PATCH] S390: Also check vector support in memmove ifunc-selector [BZ #27511]
https://sourceware.org/pipermail/libc-alpha/2021-March/124311.html

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[Bug libc/27511] S390 memmove assumes Vector Facility when MIE Facility 3 is present

[ian at iarosh dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27511

--- Comment #2 from Ian <ian at iarosh dot com> ---
I discovered the problem using Fedora 33 s390x under Hercules (the S390
emulator). Hercules does not support Vector, but recently started supporting
MIE3, whereupon the problem surfaced. However, as Vector is still optional even
on a z15 (though possibly not for much longer) someone somewhere might
experience the problem on real hardware.

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[Bug libc/27511] S390 memmove assumes Vector Facility when MIE Facility 3 is present

[stli at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27511

Stefan Liebler <stli at linux dot ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |2.34

--- Comment #3 from Stefan Liebler <stli at linux dot ibm.com> ---
Committed to master:
"S390: Also check vector support in memmove ifunc-selector [BZ #27511]"
https://sourceware.org/git/?p=glibc.git;a=commit;h=7759be2593b689cb1eafc0f52ee7f59c639e5d2f

and to the release branches 2.30 - 2.33

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