Messages in this thread | | | Date | Mon, 18 Jan 2010 14:37:19 +0200 | From | Avi Kivity <> | Subject | Re: [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
| |