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    SubjectRe: [PATCH v3 08/10] x86-64: Emulate legacy vsyscalls
    On Wed, Jun 1, 2011 at 7:54 AM, Brian Gerst <brgerst@gmail.com> wrote:
    > On Tue, May 31, 2011 at 9:16 AM, Andy Lutomirski <luto@mit.edu> wrote:
    >> There's a fair amount of code in the vsyscall page.  It contains a
    >> syscall instruction (in the gettimeofday fallback) and who knows
    >> what will happen if an exploit jumps into the middle of some other
    >> code.
    >>
    >> Reduce the risk by replacing the vsyscalls with short magic
    >> incantations that cause the kernel to emulate the real vsyscalls.
    >> These incantations are useless if entered in the middle.
    >
    > How about remapping the vsyscall page into a random page in the
    > modules area, and make the fixed page simply have stubs that jump to
    > the code in that page.  That would solve the fixed address syscall
    > problem without any more overhead.

    It wouldn't give any protection against local attacks, though.

    --Andy

    >
    > --
    > Brian Gerst
    >
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