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From: "msc at linux dot ibm.com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/27623] New: powerpc: Missing registers in sc[v] clobbers
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Date: Mon, 22 Mar 2021 13:23:48 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27623

            Bug ID: 27623
           Summary: powerpc: Missing registers in sc[v] clobbers list
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: msc at linux dot ibm.com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

The current clobbers list for syscalls using sc or scv in
sysdeps/unix/sysv/linux/powerpc/sysdep.h is not complete, as the kernel
zeroes XER register on exit and per the kernel documentation scv may also
clobber the condition register.

This is unlikely to be causing issues in the wild today, as the code has
been missing the XER clobber for years and I couldn't find any reported bugs
related to that. Also, the kernel currently restores the CR on exit, but
that could change in the future, as that is not mandated by the ABI for all
CR fields.

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