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perf, x86: Robustify PEBS fixup

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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: Peter 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-03-05 16:29:14 +01:00 committed by Ingo Molnar
parent 74846d35b2
commit a562b1871f
1 changed files with 19 additions and 2 deletions
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21
arch/x86/kernel/cpu/perf_event_intel_ds.c
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@ -399,10 +399,23 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
if (!x86_pmu.intel_cap.pebs_trap)
return 1;
/*
* No LBR entry, no basic block, no rewinding
*/
if (!cpuc->lbr_stack.nr || !from || !to)
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;
/*
@ -420,7 +433,7 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
old_to = to;
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);
if (bytes != size)
@ -440,6 +453,10 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
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;
}