perf stat: Enable counting events for BPF programs

Introduce 'perf stat -b' option, which counts events for BPF programs, like:

  [root@localhost ~]# ~/perf stat -e ref-cycles,cycles -b 254 -I 1000
     1.487903822            115,200      ref-cycles
     1.487903822             86,012      cycles
     2.489147029             80,560      ref-cycles
     2.489147029             73,784      cycles
     3.490341825             60,720      ref-cycles
     3.490341825             37,797      cycles
     4.491540887             37,120      ref-cycles
     4.491540887             31,963      cycles

The example above counts 'cycles' and 'ref-cycles' of BPF program of id
254.  This is similar to bpftool-prog-profile command, but more
flexible.

'perf stat -b' creates per-cpu perf_event and loads fentry/fexit BPF
programs (monitor-progs) to the target BPF program (target-prog). The
monitor-progs read perf_event before and after the target-prog, and
aggregate the difference in a BPF map. Then the user space reads data
from these maps.

A new 'struct bpf_counter' is introduced to provide a common interface
that uses BPF programs/maps to count perf events.

Committer notes:

Removed all but bpf_counter.h includes from evsel.h, not needed at all.

Also BPF map lookups for PERCPU_ARRAYs need to have as its value receive
buffer passed to the kernel libbpf_num_possible_cpus() entries, not
evsel__nr_cpus(evsel), as the former uses
/sys/devices/system/cpu/possible while the later uses
/sys/devices/system/cpu/online, which may be less than the 'possible'
number making the bpf map lookup overwrite memory and cause hard to
debug memory corruption.

We need to continue using evsel__nr_cpus(evsel) when accessing the
perf_counts array tho, not to overwrite another are of memory :-)

Signed-off-by: Song Liu <songliubraving@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/lkml/20210120163031.GU12699@kernel.org/
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-team@fb.com
Link: http://lore.kernel.org/lkml/20201229214214.3413833-4-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 33 insertions, 1 deletions

diff --git a/tools/perf/util/target.c b/tools/perf/util/target.c
index a3db13dea937..0f383418e3df 100644
--- a/tools/perf/util/target.c
+++ b/tools/perf/util/target.c
@@ -56,6 +56,34 @@ enum target_errno target__validate(struct target *target)
 			ret = TARGET_ERRNO__UID_OVERRIDE_SYSTEM;
 	}
 
+	/* BPF and CPU are mutually exclusive */
+	if (target->bpf_str && target->cpu_list) {
+		target->cpu_list = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_CPU;
+	}
+
+	/* BPF and PID/TID are mutually exclusive */
+	if (target->bpf_str && target->tid) {
+		target->tid = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_PID;
+	}
+
+	/* BPF and UID are mutually exclusive */
+	if (target->bpf_str && target->uid_str) {
+		target->uid_str = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_UID;
+	}
+
+	/* BPF and THREADS are mutually exclusive */
+	if (target->bpf_str && target->per_thread) {
+		target->per_thread = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_THREAD;
+	}
+
 	/* THREAD and SYSTEM/CPU are mutually exclusive */
 	if (target->per_thread && (target->system_wide || target->cpu_list)) {
 		target->per_thread = false;
@@ -109,6 +137,10 @@ static const char *target__error_str[] = {
 	"PID/TID switch overriding SYSTEM",
 	"UID switch overriding SYSTEM",
 	"SYSTEM/CPU switch overriding PER-THREAD",
+	"BPF switch overriding CPU",
+	"BPF switch overriding PID/TID",
+	"BPF switch overriding UID",
+	"BPF switch overriding THREAD",
 	"Invalid User: %s",
 	"Problems obtaining information for user %s",
 };
@@ -134,7 +166,7 @@ int target__strerror(struct target *target, int errnum,
 
 	switch (errnum) {
 	case TARGET_ERRNO__PID_OVERRIDE_CPU ...
-	     TARGET_ERRNO__SYSTEM_OVERRIDE_THREAD:
+	     TARGET_ERRNO__BPF_OVERRIDE_THREAD:
 		snprintf(buf, buflen, "%s", msg);
 		break;