Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)

From: Avi Kivity
Date: Mon Jan 18 2010 - 07:37:54 EST

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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