When runs in perf mode, the driver always enables the PID tracing. This can lead confusion when the profiling session runs in non-root PID namespace, whereas it records the PIDs from the root PID namespace.
To avoid confusion for PID tracing, when runs in perf mode, this patch changes to only enable PID tracing for root PID namespace.
As result, after apply this patch, the perf tool reports PID as '-1' for all samples:
# unshare --fork --pid perf record -e cs_etm// -m 64K,64K -a \ -o perf_test.data -- uname # perf report -i perf_test.data --itrace=Zi1000i --stdio
# Total Lost Samples: 0 # # Samples: 94 of event 'instructions' # Event count (approx.): 94000 # # Overhead Command Shared Object Symbol # ........ ....... ................. .............................. # 68.09% :-1 [kernel.kallsyms] [k] __sched_text_end 3.19% :-1 [kernel.kallsyms] [k] hrtimer_interrupt 2.13% :-1 [kernel.kallsyms] [k] __bitmap_and 2.13% :-1 [kernel.kallsyms] [k] trace_vbprintk 1.06% :-1 [kernel.kallsyms] [k] __fget_files 1.06% :-1 [kernel.kallsyms] [k] __schedule 1.06% :-1 [kernel.kallsyms] [k] __softirqentry_text_start 1.06% :-1 [kernel.kallsyms] [k] __update_load_avg_cfs_rq 1.06% :-1 [kernel.kallsyms] [k] __update_load_avg_se 1.06% :-1 [kernel.kallsyms] [k] arch_counter_get_cntpct 1.06% :-1 [kernel.kallsyms] [k] check_and_switch_context 1.06% :-1 [kernel.kallsyms] [k] format_decode 1.06% :-1 [kernel.kallsyms] [k] handle_percpu_devid_irq 1.06% :-1 [kernel.kallsyms] [k] irq_enter_rcu 1.06% :-1 [kernel.kallsyms] [k] irqtime_account_irq 1.06% :-1 [kernel.kallsyms] [k] ktime_get 1.06% :-1 [kernel.kallsyms] [k] ktime_get_coarse_real_ts64 1.06% :-1 [kernel.kallsyms] [k] memmove 1.06% :-1 [kernel.kallsyms] [k] perf_ioctl 1.06% :-1 [kernel.kallsyms] [k] perf_output_begin 1.06% :-1 [kernel.kallsyms] [k] perf_output_copy 1.06% :-1 [kernel.kallsyms] [k] profile_tick 1.06% :-1 [kernel.kallsyms] [k] sched_clock 1.06% :-1 [kernel.kallsyms] [k] timerqueue_add 1.06% :-1 [kernel.kallsyms] [k] trace_save_cmdline 1.06% :-1 [kernel.kallsyms] [k] update_load_avg 1.06% :-1 [kernel.kallsyms] [k] vbin_printf
Signed-off-by: Leo Yan leo.yan@linaro.org --- drivers/hwtracing/coresight/coresight-etm4x-core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index 86a313857b58..f3eda536267c 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -656,7 +656,9 @@ static int etm4_parse_event_config(struct coresight_device *csdev, config->cfg |= BIT(11); }
- if (attr->config & BIT(ETM_OPT_CTXTID)) + /* Only trace contextID when runs in root PID namespace */ + if ((attr->config & BIT(ETM_OPT_CTXTID)) && + task_is_in_init_pid_ns(current)) /* bit[6], Context ID tracing bit */ config->cfg |= BIT(ETM4_CFG_BIT_CTXTID);
@@ -670,7 +672,11 @@ static int etm4_parse_event_config(struct coresight_device *csdev, ret = -EINVAL; goto out; } - config->cfg |= BIT(ETM4_CFG_BIT_VMID) | BIT(ETM4_CFG_BIT_VMID_OPT); + + /* Only trace virtual contextID when runs in root PID namespace */ + if (task_is_in_init_pid_ns(current)) + config->cfg |= BIT(ETM4_CFG_BIT_VMID) | + BIT(ETM4_CFG_BIT_VMID_OPT); }
/* return stack - enable if selected and supported */