From: Thomas Richter Date: Fri, 26 Jun 2020 09:24:34 +0000 (+0200) Subject: s390/cpum_sf: prohibit callchain data collection X-Git-Tag: v5.10.7~2180^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5aa98879efe77d33d1639e006d4b0c1579cde9f6;p=platform%2Fkernel%2Flinux-rpi.git s390/cpum_sf: prohibit callchain data collection CPU Measurement sampling facility on s390 does not support perf tool collection of callchain data using --call-graph option. The sampling facility collects samples in a ring buffer which includes only the instruction address the samples were taken. When the ring buffer hits a watermark, a measurement alert interrupt is triggered and handled by the performance measurement unit (PMU) device driver. It collects the samples and feeds each sample to the perf ring buffer in the common code via functions perf_prepare_sample()/perf_output_sample(). When function perf_prepare_sample() is called to collect sample data's callchain, user register values or stack area, invalid data is picked, because the context of the collected information does not match the context when the sample was taken. There is currently no way to provide the callchain and other information, because the hardware sampler does not collect this information. Therefore prohibit sampling when the user requests a callchain graph from the hardware sampler. Return -EOPNOTSUPP to the user in this case. If call chains are really wanted, users need to specify software event cpu-clock to get the callchain information from a software event. Signed-off-by: Thomas Richter Reviewed-by: Sumanth Korikkar Signed-off-by: Heiko Carstens --- diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c index 85a711d..4f9e462 100644 --- a/arch/s390/kernel/perf_cpum_sf.c +++ b/arch/s390/kernel/perf_cpum_sf.c @@ -881,12 +881,21 @@ out: return err; } +static bool is_callchain_event(struct perf_event *event) +{ + u64 sample_type = event->attr.sample_type; + + return sample_type & (PERF_SAMPLE_CALLCHAIN | PERF_SAMPLE_REGS_USER | + PERF_SAMPLE_STACK_USER); +} + static int cpumsf_pmu_event_init(struct perf_event *event) { int err; /* No support for taken branch sampling */ - if (has_branch_stack(event)) + /* No support for callchain, stacks and registers */ + if (has_branch_stack(event) || is_callchain_event(event)) return -EOPNOTSUPP; switch (event->attr.type) {