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    SubjectRe: [patch 2/2] x86 NMI-safe INT3 and Page Fault
    On Fri, Jul 16, 2010 at 11:25:19AM -0700, Linus Torvalds wrote:
    > On Fri, Jul 16, 2010 at 11:15 AM, Avi Kivity <> wrote:
    > >
    > > I think the concern here is about an NMI handler's code running in vmalloc
    > > space, or is it something else?
    > I think the concern was also potentially doing things like backtraces
    > etc that may need access to the module data structures (I think the
    > ELF headers end up all being in vmalloc space too, for example).
    > The whole debugging thing is also an issue. Now, I obviously am not a
    > big fan of remote debuggers, but everybody tells me I'm wrong. And
    > putting a breakpoint on NMI is certainly not insane if you are doing
    > debugging in the first place. So it's not necessarily always about the
    > page faults.

    We already have infrastructure for kprobes to prevent breakpoints
    on critical code (the __kprobes section). In principle kgdb/kdb
    could be taught about honoring those too.

    That wouldn't help for truly external JTAG debuggers, but I would assume
    those generally can (should) handle any contexts anyways.


    -- -- Speaking for myself only.

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