[Bug libc/28782] New: x86-64 ISA level for glibc itself is always x86-64-baseline

[Bug libc/28782] New: x86-64 ISA level for glibc itself is always x86-64-baseline

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

            Bug ID: 28782
           Summary: x86-64 ISA level for glibc itself is always
                    x86-64-baseline
           Product: glibc
           Version: 2.35
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---
             Build: x86_64-linux-gnu
             Flags: security-

Even if glibc is built with CC="gcc -march=x86-64-v4" or CFLAGS includes
-march=x86-64-v2. This means that the check in sysdeps/x86/dl-prop.h never
reports anything amiss.

(I am working on patches to allow the early startup code to build with a
different ISA level.)

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[Bug libc/28782] x86-64 ISA level for glibc itself is always x86-64-baseline

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

--- Comment #1 from Florian Weimer <fweimer at redhat dot com> ---
HAVE_X86_LAHF_SAHF and HAVE_X86_MOVBE are not set correctly.

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[Bug libc/28782] x86-64 ISA level for glibc itself is always x86-64-baseline

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
But there is another bug, even after fixing that.

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[Bug libc/28782] x86-64 ISA level for glibc itself is always x86-64-baseline

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

--- Comment #3 from Florian Weimer <fweimer at redhat dot com> ---
(In reply to Florian Weimer from comment #2)
> But there is another bug, even after fixing that.

The markup is there after these changes, but we would have to compile most of
the loader with the baseline ISA to avoid crashes before reaching the existing
ISA level check. I'm going to add a separate check to avoid that.

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[Bug libc/28782] x86-64 ISA level for glibc itself is always x86-64-baseline

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

--- Comment #4 from Florian Weimer <fweimer at redhat dot com> ---
Patches posted:

[PATCH 0/7] Reliable CPU compatibility diagnostics in ld.so
https://sourceware.org/pipermail/libc-alpha/2022-January/135291.html

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[Bug libc/28782] x86-64 ISA level for glibc itself is always x86-64-baseline

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |fweimer at redhat dot com
             Status|NEW                         |RESOLVED
   Target Milestone|---                         |2.35
         Resolution|---                         |FIXED

--- Comment #5 from Florian Weimer <fweimer at redhat dot com> ---
First parted fixed by:

commit 5732a881aad24fac876f5505a212395048a7a483
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Jan 14 16:09:20 2022 +0100

    x86: HAVE_X86_LAHF_SAHF, HAVE_X86_MOVBE and -march=x86-64-vN (bug 28782)

    HAVE_X86_LAHF_SAHF is implied by x86-64-v2, and HAVE_X86_MOVBE by
    x86-64-v3.

    The individual flag does not appear in -fverbose-asm flag output
    even if the ISA level implies it.

    Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Second part fixed by:

commit 990c953bce06d77360d2e933faa9a008e2c55405
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Jan 14 20:16:05 2022 +0100

    x86: Add x86-64-vN check to early startup

    This ISA level covers the glibc build itself.  <dl-hwcap-check.h>
    cannot be used because this check (by design) happens before
    DL_PLATFORM_INIT and the x86 CPU flags initialization.

    Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

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[Bug libc/28782] x86-64 ISA level for glibc itself is always x86-64-baseline

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28782

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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