linux-kernel - Re: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86

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Message-ID: <1317987622.31132.15.camel@twins>
Date:	Fri, 07 Oct 2011 13:40:22 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, acme@...hat.com, ming.m.lin@...el.com,
	robert.richter@....com, ravitillo@....gov
Subject: Re: [PATCH 07/12] perf_events: add LBR software filter support for
 Intel X86

On Fri, 2011-10-07 at 20:25 +0900, Masami Hiramatsu wrote:
> Oops, I've thought existing code is only for kernel. Hmm, I guess
> this could cause a problem when running 32bit binary on x86-64.
> 
I queued below.
> 
---
Subject: perf, x86: Fix PEBS instruction unwind
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Fri Oct 07 13:36:40 CEST 2011

Masami spotted that we always try to decode the instruction stream as
64bit instructions when running a 64bit kernel, this doesn't work for
ia32-compat proglets.

Use TIF_IA32 to detect if we need to use the 32bit instruction
decoder.

Reported-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 arch/x86/kernel/cpu/perf_event_intel_ds.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel_ds.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -493,6 +493,7 @@ static int intel_pmu_pebs_fixup_ip(struc
 	unsigned long from = cpuc->lbr_entries[0].from;
 	unsigned long old_to, to = cpuc->lbr_entries[0].to;
 	unsigned long ip = regs->ip;
+	int is_64bit = 0;
 
 	/*
 	 * We don't need to fixup if the PEBS assist is fault like
@@ -544,7 +545,10 @@ static int intel_pmu_pebs_fixup_ip(struc
 		} else
 			kaddr = (void *)to;
 
-		kernel_insn_init(&insn, kaddr);
+#ifdef CONFIG_X86_64
+		is_64bit = kernel_ip(to) || !test_thread_flag(TIF_IA32);
+#endif
+		insn_init(&insn, kaddr, is_64bit);
 		insn_get_length(&insn);
 		to += insn.length;
 	} while (to < ip);

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