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    SubjectRe: [PATCH 4/5] x86-64: Replace vsyscall gettimeofday fallback with int 0xcc
    On Sun, May 29, 2011 at 4:01 PM, Ingo Molnar <mingo@elte.hu> wrote:
    >
    > * Andrew Lutomirski <luto@mit.edu> wrote:
    >
    >> On Sun, May 29, 2011 at 3:49 PM, Ingo Molnar <mingo@elte.hu> wrote:
    >> >
    >> > * Andrew Lutomirski <luto@mit.edu> wrote:
    >> >
    >> >> > Ok, i suspect you marked it 0xCC because that's the INT3 instruction
    >> >> > - not very useful for exploits?
    >> >>
    >> >> Exactly.
    >> >>
    >> >> The comments in irq_vectors.h make it sound like vectors 0x81..0xed
    >> >> are used for device interrupts but AFAICT it's only 0x20..0x39 that
    >> >> are used, so the precise choice of vector doesn't matter that much.
    >> >
    >> > No, we use almost all of the vector space for device interrupts. Why
    >> > do you think only 0x20..0x39 is used?
    >>
    >> Possibility my inability to understand all the IRQ mapping code in
    >> just half an hour of trying.
    >
    > Hey, you managed to find all the scattered pieces in just half an
    > hour, i'm impressed ;-)

    grep and an SSD are amazing. I'll add the BUG_ON just to satisfy my
    paranoia. I'll also update the comment in irq_vectors.h.

    --Andy


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