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Date: Mon, 18 Jan 2010 14:37:19 +0200 From: Avi Kivity <avi@...hat.com> To: Peter Zijlstra <peterz@...radead.org> CC: ananth@...ibm.com, Jim Keniston <jkenisto@...ibm.com>, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Ingo Molnar <mingo@...e.hu>, Arnaldo Carvalho de Melo <acme@...radead.org>, utrace-devel <utrace-devel@...hat.com>, Frederic Weisbecker <fweisbec@...il.com>, Masami Hiramatsu <mhiramat@...hat.com>, Maneesh Soni <maneesh@...ibm.com>, Mark Wielaard <mjw@...hat.com>, LKML <linux-kernel@...r.kernel.org> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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