linux/tools/perf/util/target.c
Song Liu fa853c4b83 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>
2021-01-20 14:25:28 -03:00

185 lines
4.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Helper functions for handling target threads/cpus
*
* Copyright (C) 2012, LG Electronics, Namhyung Kim <namhyung.kim@lge.com>
*/
#include "target.h"
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <linux/kernel.h>
#include <linux/string.h>
enum target_errno target__validate(struct target *target)
{
enum target_errno ret = TARGET_ERRNO__SUCCESS;
if (target->pid)
target->tid = target->pid;
/* CPU and PID are mutually exclusive */
if (target->tid && target->cpu_list) {
target->cpu_list = NULL;
if (ret == TARGET_ERRNO__SUCCESS)
ret = TARGET_ERRNO__PID_OVERRIDE_CPU;
}
/* UID and PID are mutually exclusive */
if (target->tid && target->uid_str) {
target->uid_str = NULL;
if (ret == TARGET_ERRNO__SUCCESS)
ret = TARGET_ERRNO__PID_OVERRIDE_UID;
}
/* UID and CPU are mutually exclusive */
if (target->uid_str && target->cpu_list) {
target->cpu_list = NULL;
if (ret == TARGET_ERRNO__SUCCESS)
ret = TARGET_ERRNO__UID_OVERRIDE_CPU;
}
/* PID and SYSTEM are mutually exclusive */
if (target->tid && target->system_wide) {
target->system_wide = false;
if (ret == TARGET_ERRNO__SUCCESS)
ret = TARGET_ERRNO__PID_OVERRIDE_SYSTEM;
}
/* UID and SYSTEM are mutually exclusive */
if (target->uid_str && target->system_wide) {
target->system_wide = false;
if (ret == TARGET_ERRNO__SUCCESS)
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;
if (ret == TARGET_ERRNO__SUCCESS)
ret = TARGET_ERRNO__SYSTEM_OVERRIDE_THREAD;
}
return ret;
}
enum target_errno target__parse_uid(struct target *target)
{
struct passwd pwd, *result;
char buf[1024];
const char *str = target->uid_str;
target->uid = UINT_MAX;
if (str == NULL)
return TARGET_ERRNO__SUCCESS;
/* Try user name first */
getpwnam_r(str, &pwd, buf, sizeof(buf), &result);
if (result == NULL) {
/*
* The user name not found. Maybe it's a UID number.
*/
char *endptr;
int uid = strtol(str, &endptr, 10);
if (*endptr != '\0')
return TARGET_ERRNO__INVALID_UID;
getpwuid_r(uid, &pwd, buf, sizeof(buf), &result);
if (result == NULL)
return TARGET_ERRNO__USER_NOT_FOUND;
}
target->uid = result->pw_uid;
return TARGET_ERRNO__SUCCESS;
}
/*
* This must have a same ordering as the enum target_errno.
*/
static const char *target__error_str[] = {
"PID/TID switch overriding CPU",
"PID/TID switch overriding UID",
"UID switch overriding CPU",
"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",
};
int target__strerror(struct target *target, int errnum,
char *buf, size_t buflen)
{
int idx;
const char *msg;
BUG_ON(buflen == 0);
if (errnum >= 0) {
str_error_r(errnum, buf, buflen);
return 0;
}
if (errnum < __TARGET_ERRNO__START || errnum >= __TARGET_ERRNO__END)
return -1;
idx = errnum - __TARGET_ERRNO__START;
msg = target__error_str[idx];
switch (errnum) {
case TARGET_ERRNO__PID_OVERRIDE_CPU ...
TARGET_ERRNO__BPF_OVERRIDE_THREAD:
snprintf(buf, buflen, "%s", msg);
break;
case TARGET_ERRNO__INVALID_UID:
case TARGET_ERRNO__USER_NOT_FOUND:
snprintf(buf, buflen, msg, target->uid_str);
break;
default:
/* cannot reach here */
break;
}
return 0;
}