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

[Avi Kivity]

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/