Re: [PATCH] perf cs-etm: Correct CPU mode for samples

Em Tue, Oct 30, 2018 at 03:18:28PM +0800, Leo Yan escreveu:

Since commit 9042f5e3539e ("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 9042f5e3539e ("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.

Mathieu, can I have your Acked-by, please? Leo, thanks for acting so quickly on this one!

Now processing coresight traces should be faster, less lookups :-)

- Arnaldo

Signed-off-by: Leo Yan leo.yan@linaro.org

tools/perf/util/cs-etm.c | 39 ++++++++++++++++++++++++++++++--------- 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 3b37d66..73430b7 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -244,6 +244,27 @@ static void cs_etm__free(struct perf_session *session) 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_etm_queue *etmq, u64 address, 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_sample(struct cs_etm_queue *etmq, 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_sample(struct cs_etm_queue *etmq, 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(struct cs_etm_queue *etmq) 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(struct cs_etm_queue *etmq) 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 -- 2.7.4