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    SubjectRe: Compat 32-bit syscall entry from 64-bit task!?
    On Thu, Jan 19, 2012 at 3:54 PM, Jamie Lokier <> wrote:
    > Mine was: strace currently checks the CS value and may have a bug on
    > existing/older kernels if Xen is involved when using the *normal*
    > syscall entry point (not int $0x80).  Can we patch strace to solve
    > that on those kernels in a generic way, or does the fix need to
    > hard-code knowledge of Xen's CS values (and any similar PV hypervisors
    > if there are any).
    > No amount of patching newer kernels will fix that, but it would be
    > nice if newer kernels made it unambiguous.

    Ok. So yeah, I think the heuristics for strace could possibly be
    improved when running under Xen, I agree. See my suggestion for taking
    other register contents into account (%rsp in particular - the code
    segment tends to be mapped low in 64-bit mode, but the stack is almost
    always high unless you are doing something really odd).

    So heuristics improvements could be a good idea. Very few real
    programs will use "int 0x80" in long mode, since it's slow and limited
    to 32 bit.

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      Last update: 2012-01-20 01:09    [W:0.022 / U:4.528 seconds]
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