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Commit a562b187 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf, x86: Robustify PEBS fixup 



It turns out the LBR is massively unreliable on certain CPUs, so code the
fixup a little more defensive to avoid crashing the kernel.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: paulus@samba.org
Cc: eranian@google.com
Cc: robert.richter@amd.com
Cc: fweisbec@gmail.com
LKML-Reference: <20100305154129.042271287@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 74846d35

arch/x86/kernel/cpu/perf_event_intel_ds.c

+19 −2
Original line number Original line Diff line number Diff line
@@ -399,10 +399,23 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs) 
	if (!x86_pmu.intel_cap.pebs_trap)

	if (!x86_pmu.intel_cap.pebs_trap)

		return 1;

		return 1;





	/*

	 * No LBR entry, no basic block, no rewinding

	 */

	if (!cpuc->lbr_stack.nr || !from || !to)

	if (!cpuc->lbr_stack.nr || !from || !to)

		return 0;

		return 0;





	if (ip < to)

	/*

	 * Basic blocks should never cross user/kernel boundaries

	 */

	if (kernel_ip(ip) != kernel_ip(to))

		return 0;



	/*

	 * unsigned math, either ip is before the start (impossible) or

	 * the basic block is larger than 1 page (sanity)

	 */

	if ((ip - to) > PAGE_SIZE)

		return 0;

		return 0;





	/*

	/*
@@ -420,7 +433,7 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs) 




		old_to = to;

		old_to = to;

		if (!kernel_ip(ip)) {

		if (!kernel_ip(ip)) {

			int bytes, size = min_t(int, MAX_INSN_SIZE, ip - to);

			int bytes, size = MAX_INSN_SIZE;





			bytes = copy_from_user_nmi(buf, (void __user *)to, size);

			bytes = copy_from_user_nmi(buf, (void __user *)to, size);

			if (bytes != size)

			if (bytes != size)
@@ -440,6 +453,10 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs) 
		return 1;

		return 1;

	}

	}





	/*

	 * Even though we decoded the basic block, the instruction stream

	 * never matched the given IP, either the TO or the IP got corrupted.

	 */

	return 0;

	return 0;

}

}