Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932151AbaKEDK4 (ORCPT ); Tue, 4 Nov 2014 22:10:56 -0500 Received: from mga01.intel.com ([192.55.52.88]:23438 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753352AbaKEDKv (ORCPT ); Tue, 4 Nov 2014 22:10:51 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,317,1413270000"; d="scan'208";a="617287022" From: Kan Liang To: a.p.zijlstra@chello.nl, eranian@google.com Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, paulus@samba.org, acme@kernel.org, jolsa@redhat.com, ak@linux.intel.com, Kan Liang Subject: [PATCH V7 15/17] perf, x86: Discard zero length call entries in LBR call stack Date: Tue, 4 Nov 2014 21:56:11 -0500 Message-Id: <1415156173-10035-16-git-send-email-kan.liang@intel.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1415156173-10035-1-git-send-email-kan.liang@intel.com> References: <1415156173-10035-1-git-send-email-kan.liang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yan, Zheng "Zero length call" uses the attribute of the call instruction to push the immediate instruction pointer on to the stack and then pops off that address into a register. This is accomplished without any matching return instruction. It confuses the hardware and make the recorded call stack incorrect. We can partially resolve this issue by: decode call instructions and discard any zero length call entry in the LBR stack. Signed-off-by: Yan, Zheng Signed-off-by: Kan Liang --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 12a87b0..b75adec 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -94,7 +94,8 @@ enum { X86_BR_ABORT = 1 << 12,/* transaction abort */ X86_BR_IN_TX = 1 << 13,/* in transaction */ X86_BR_NO_TX = 1 << 14,/* not in transaction */ - X86_BR_CALL_STACK = 1 << 15,/* call stack */ + X86_BR_ZERO_CALL = 1 << 15,/* zero length call */ + X86_BR_CALL_STACK = 1 << 16,/* call stack */ }; #define X86_BR_PLM (X86_BR_USER | X86_BR_KERNEL) @@ -111,13 +112,15 @@ enum { X86_BR_JMP |\ X86_BR_IRQ |\ X86_BR_ABORT |\ - X86_BR_IND_CALL) + X86_BR_IND_CALL |\ + X86_BR_ZERO_CALL) #define X86_BR_ALL (X86_BR_PLM | X86_BR_ANY) #define X86_BR_ANY_CALL \ (X86_BR_CALL |\ X86_BR_IND_CALL |\ + X86_BR_ZERO_CALL |\ X86_BR_SYSCALL |\ X86_BR_IRQ |\ X86_BR_INT) @@ -689,6 +692,12 @@ static int branch_type(unsigned long from, unsigned long to, int abort) ret = X86_BR_INT; break; case 0xe8: /* call near rel */ + insn_get_immediate(&insn); + if (insn.immediate1.value == 0) { + /* zero length call */ + ret = X86_BR_ZERO_CALL; + break; + } case 0x9a: /* call far absolute */ ret = X86_BR_CALL; break; -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/