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SubjectRe: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)
On 01/18/2010 02:14 PM, Peter Zijlstra wrote:
>
>> Well, the alternatives are very unappealing. Emulation and
>> single-stepping are going to be very slow compared to a couple of jumps.
>>
> With CPL2 or RPL on user segments the protection issue seems to be
> manageable for running the instructions from kernel space.
>

CPL2 gives unrestricted access to the kernel address space; and RPL does
not affect page level protection. Segment limits don't work on x86-64.
But perhaps I missed something - these things are tricky.

It should be possible to translate the instruction into an address space
check, followed by the action, but that's still slower due to privilege
level switches.

--
error compiling committee.c: too many arguments to function



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