linux-kernel - [PATCH 5.10 200/452] perf/amd/ibs: Use interrupt regs ip for stack unwinding

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Message-Id: <20220607164914.523627774@linuxfoundation.org>
Date:   Tue,  7 Jun 2022 19:00:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>,
        Peter Zijlstra <peterz@...radead.org>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 200/452] perf/amd/ibs: Use interrupt regs ip for stack unwinding

From: Ravi Bangoria <ravi.bangoria@....com>

[ Upstream commit 3d47083b9ff46863e8374ad3bb5edb5e464c75f8 ]

IbsOpRip is recorded when IBS interrupt is triggered. But there is
a skid from the time IBS interrupt gets triggered to the time the
interrupt is presented to the core. Meanwhile processor would have
moved ahead and thus IbsOpRip will be inconsistent with rsp and rbp
recorded as part of the interrupt regs. This causes issues while
unwinding stack using the ORC unwinder as it needs consistent rip,
rsp and rbp. Fix this by using rip from interrupt regs instead of
IbsOpRip for stack unwinding.

Fixes: ee9f8fce99640 ("x86/unwind: Add the ORC unwinder")
Reported-by: Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20220429051441.14251-1-ravi.bangoria@amd.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/events/amd/ibs.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 780d89d2ae32..8a85658a24cc 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -312,6 +312,16 @@ static int perf_ibs_init(struct perf_event *event)
 	hwc->config_base = perf_ibs->msr;
 	hwc->config = config;
 
+	/*
+	 * rip recorded by IbsOpRip will not be consistent with rsp and rbp
+	 * recorded as part of interrupt regs. Thus we need to use rip from
+	 * interrupt regs while unwinding call stack. Setting _EARLY flag
+	 * makes sure we unwind call-stack before perf sample rip is set to
+	 * IbsOpRip.
+	 */
+	if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
+		event->attr.sample_type |= __PERF_SAMPLE_CALLCHAIN_EARLY;
+
 	return 0;
 }
 
@@ -692,6 +702,14 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
 		data.raw = &raw;
 	}
 
+	/*
+	 * rip recorded by IbsOpRip will not be consistent with rsp and rbp
+	 * recorded as part of interrupt regs. Thus we need to use rip from
+	 * interrupt regs while unwinding call stack.
+	 */
+	if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
+		data.callchain = perf_callchain(event, iregs);
+
 	throttle = perf_event_overflow(event, &data, &regs);
 out:
 	if (throttle) {
-- 
2.35.1