[tip:perf/pebs] perf, x86: Robustify PEBS fixup
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From: tip-bot for Peter Zijlstra on 10 Mar 2010 08:30 Commit-ID: a562b1871f7f7d2f3a835c3c1e07fa58d473cfb7 Gitweb: http://git.kernel.org/tip/a562b1871f7f7d2f3a835c3c1e07fa58d473cfb7 Author: Peter Zijlstra <a.p.zijlstra(a)chello.nl> AuthorDate: Fri, 5 Mar 2010 16:29:14 +0100 Committer: Ingo Molnar <mingo(a)elte.hu> CommitDate: Wed, 10 Mar 2010 13:23:35 +0100 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: Peter Zijlstra <a.p.zijlstra(a)chello.nl> Cc: Arnaldo Carvalho de Melo <acme(a)infradead.org> Cc: paulus(a)samba.org Cc: eranian(a)google.com Cc: robert.richter(a)amd.com Cc: fweisbec(a)gmail.com LKML-Reference: <20100305154129.042271287(a)chello.nl> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> --- arch/x86/kernel/cpu/perf_event_intel_ds.c | 21 +++++++++++++++++++-- 1 files changed, 19 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c index a67fff1..e7ac517 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c @@ -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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |