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    SubjectRe: [PATCH v10 05/11] seccomp: add system call filtering using BPF
    On 02/22/2012 03:51 PM, Andrew Lutomirski wrote:
    > On Wed, Feb 22, 2012 at 3:46 PM, Indan Zupancic <indan@nul.nu> wrote:
    >> On Wed, February 22, 2012 20:47, Will Drewry wrote:
    >>> On Wed, Feb 22, 2012 at 8:23 AM, Ben Hutchings
    >>>> I would have thought the way to make sure the architecture is always
    >>>> checked is to pack it together with the syscall number.
    >>
    >> I missed that suggestion, putting the syscall number and arch in one
    >> data field would indeed make it harder to not check the arch.
    >
    > Is there enough room? On x86-64 at least, rax could conceivably be
    > extended to 64 bits some day. Bit 30 is already spoken for by x32.
    >

    No it couldn't, because we mask off the high 32 bits and thus it could
    (theoretically) break user space.

    -hpa


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



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