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    SubjectRe: x86: get rid of the insane TIF_ABI_PENDING bit
    On 02/15/2010 11:41 AM, Roland McGrath wrote:
    >> I suspect the purpose of TS_COMPAT is actually so you can ptrace() the
    >> newly exec'd process (and see it as a 32-bit process!) before it returns
    >> to userspace. The comment, obviously, is wrong -- that again refers to
    >> TIF_IA32.
    >
    > I don't follow you. TS_COMPAT does not affect ptrace.
    > It affects syscall-audit, but only at syscall entry time.
    > It affects asm/syscall.h accessors, but ptrace does not use those.
    > It affects whatever uses is_compat_task(), but I can't see anything
    > where that matters except inside some particular syscall or for
    > syscall restart after signals.
    >
    > TS_COMPAT does not affect the syscall return machinery itself.
    > The return path just follows from the particular entry path.

    It's entirely possible it is completely superfluous. The patch in
    question only moves the setting. I don't know what gdb or strace use to
    distinguish a 32-bit and a 64-bit process, which is why I thought it
    might have something to do with ptrace.

    -hpa

    --
    H. Peter Anvin, Intel Open Source Technology Center
    I work for Intel. I don't speak on their behalf.



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