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Patch "perf cs-etm: Correct CPU mode for samples" has been added to the 4.19-stable tree

PATCH gregkh at linuxfoundation.org 1 participant 1 message Nov 19, 2018

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perf events Arm/CoreSight framework and drivers Performance events tooling arm64
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gregkh at linuxfoundation.org

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This is a note to let you know that I've just added the patch titled

perf cs-etm: Correct CPU mode for samples

to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-cs-etm-correct-cpu-mode-for-samples.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From d6c9c05fe1eb4b213b183d8a1e79416256dc833a Mon Sep 17 00:00:00 2001

From: Leo Yan <[email protected]>
Date: Tue, 30 Oct 2018 15:18:28 +0800
Subject: perf cs-etm: Correct CPU mode for samples

From: Leo Yan <[email protected]>

commit d6c9c05fe1eb4b213b183d8a1e79416256dc833a upstream.

Since commit edeb0c90df35 ("perf tools: Stop fallbacking to kallsyms for vdso symbols lookup"), the kernel address cannot be properly parsed to kernel symbol with command 'perf script -k vmlinux'. The reason is CoreSight samples is always to set CPU mode as PERF_RECORD_MISC_USER, thus it fails to find corresponding map/dso in below flows:

process_sample_event()

    `-> machine__resolve()
	  `-> thread__find_map(thread, sample->cpumode, sample->ip, al);

In this flow it needs to pass argument 'sample->cpumode' to tell what's the CPU mode, before it always passed PERF_RECORD_MISC_USER but without any failure until the commit edeb0c90df35 ("perf tools: Stop fallbacking to kallsyms for vdso symbols lookup") has been merged. The reason is even with the wrong CPU mode the function thread__find_map() firstly fails to find map but it will rollback to find kernel map for vdso symbols lookup. In the latest code it has removed the fallback code, thus if CPU mode is PERF_RECORD_MISC_USER then it cannot find map anymore with kernel address.

This patch is to correct samples CPU mode setting, it creates a new helper function cs_etm__cpu_mode() to tell what's the CPU mode based on the address with the info from machine structure; this patch has a bit extension to check not only kernel and user mode, but also check for host/guest and hypervisor mode. Finally this patch uses the function in instruction and branch samples and also apply in cs_etm__mem_access() for a minor polishing.

Signed-off-by Leo Yan <[email protected]>
Cc Adrian Hunter <[email protected]>
Cc Alexander Shishkin <[email protected]>
Cc David Miller <[email protected]>
Cc Jiri Olsa <[email protected]>
Cc Mathieu Poirier <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc coresight at lists.linaro.org
Cc linux-arm-kernel at lists.infradead.org
Cc stable at kernel.org # v4.19
Link http://lkml.kernel.org/r/1540883908-17018-1-git-send-email-leo.yan at linaro.org
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 tools/perf/util/cs-etm.c |   39 ++++++++++++++++++++++++++++++---------
 1 file changed, 30 insertions(+), 9 deletions(-)
tools/perf/util/cs-etm.c +30 -9
@@ -244,6 +244,27 @@ static void cs_etm__free(struct perf_ses
 	zfree(&aux);
 }
 
+static u8 cs_etm__cpu_mode(struct cs_etm_queue *etmq, u64 address)
+{
+	struct machine *machine;
+
+	machine = etmq->etm->machine;
+
+	if (address >= etmq->etm->kernel_start) {
+		if (machine__is_host(machine))
+			return PERF_RECORD_MISC_KERNEL;
+		else
+			return PERF_RECORD_MISC_GUEST_KERNEL;
+	} else {
+		if (machine__is_host(machine))
+			return PERF_RECORD_MISC_USER;
+		else if (perf_guest)
+			return PERF_RECORD_MISC_GUEST_USER;
+		else
+			return PERF_RECORD_MISC_HYPERVISOR;
+	}
+}
+
 static u32 cs_etm__mem_access(struct cs_etm_queue *etmq, u64 address,
 			      size_t size, u8 *buffer)
 {

@@ -258,10 +279,7 @@ static u32 cs_etm__mem_access(struct cs_
 		return -1;
 
 	machine = etmq->etm->machine;
-	if (address >= etmq->etm->kernel_start)
-		cpumode = PERF_RECORD_MISC_KERNEL;
-	else
-		cpumode = PERF_RECORD_MISC_USER;
+	cpumode = cs_etm__cpu_mode(etmq, address);
 
 	thread = etmq->thread;
 	if (!thread) {

@@ -653,7 +671,7 @@ static int cs_etm__synth_instruction_sam
 	struct perf_sample sample = {.ip = 0,};
 
 	event->sample.header.type = PERF_RECORD_SAMPLE;
-	event->sample.header.misc = PERF_RECORD_MISC_USER;
+	event->sample.header.misc = cs_etm__cpu_mode(etmq, addr);
 	event->sample.header.size = sizeof(struct perf_event_header);
 
 	sample.ip = addr;

@@ -665,7 +683,7 @@ static int cs_etm__synth_instruction_sam
 	sample.cpu = etmq->packet->cpu;
 	sample.flags = 0;
 	sample.insn_len = 1;
-	sample.cpumode = event->header.misc;
+	sample.cpumode = event->sample.header.misc;
 
 	if (etm->synth_opts.last_branch) {
 		cs_etm__copy_last_branch_rb(etmq);

@@ -706,12 +724,15 @@ static int cs_etm__synth_branch_sample(s
 		u64			nr;
 		struct branch_entry	entries;
 	} dummy_bs;
+	u64 ip;
+
+	ip = cs_etm__last_executed_instr(etmq->prev_packet);
 
 	event->sample.header.type = PERF_RECORD_SAMPLE;
-	event->sample.header.misc = PERF_RECORD_MISC_USER;
+	event->sample.header.misc = cs_etm__cpu_mode(etmq, ip);
 	event->sample.header.size = sizeof(struct perf_event_header);
 
-	sample.ip = cs_etm__last_executed_instr(etmq->prev_packet);
+	sample.ip = ip;
 	sample.pid = etmq->pid;
 	sample.tid = etmq->tid;
 	sample.addr = cs_etm__first_executed_instr(etmq->packet);

@@ -720,7 +741,7 @@ static int cs_etm__synth_branch_sample(s
 	sample.period = 1;
 	sample.cpu = etmq->packet->cpu;
 	sample.flags = 0;
-	sample.cpumode = PERF_RECORD_MISC_USER;
+	sample.cpumode = event->sample.header.misc;
 
 	/*
 	 * perf report cannot handle events without a branch stack

Patches currently in stable-queue which might be from leo.yan at linaro.org are

queue-4.19/perf-cs-etm-correct-cpu-mode-for-samples.patch queue-4.19/perf-intel-pt-bts-calculate-cpumode-for-synthesized-samples.patch queue-4.19/perf-intel-pt-insert-callchain-context-into-synthesized-callchains.patch