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Commit 47efb302 authored by Kaixu Xia's avatar Kaixu Xia Committed by David S. Miller
Browse files

samples/bpf: example of get selected PMU counter value 



This is a simple example and shows how to use the new ability
to get the selected Hardware PMU counter value.

Signed-off-by: default avatarKaixu Xia <xiakaixu@huawei.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 35578d79

samples/bpf/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ hostprogs-y += tracex2 
hostprogs-y += tracex3

hostprogs-y += tracex4

hostprogs-y += tracex5

hostprogs-y += tracex6

hostprogs-y += lathist



test_verifier-objs := test_verifier.o libbpf.o
@@ -25,6 +26,7 @@ tracex2-objs := bpf_load.o libbpf.o tracex2_user.o 
tracex3-objs := bpf_load.o libbpf.o tracex3_user.o

tracex4-objs := bpf_load.o libbpf.o tracex4_user.o

tracex5-objs := bpf_load.o libbpf.o tracex5_user.o

tracex6-objs := bpf_load.o libbpf.o tracex6_user.o

lathist-objs := bpf_load.o libbpf.o lathist_user.o



# Tell kbuild to always build the programs
@@ -37,6 +39,7 @@ always += tracex2_kern.o 
always += tracex3_kern.o

always += tracex4_kern.o

always += tracex5_kern.o

always += tracex6_kern.o

always += tcbpf1_kern.o

always += lathist_kern.o
@@ -51,6 +54,7 @@ HOSTLOADLIBES_tracex2 += -lelf 
HOSTLOADLIBES_tracex3 += -lelf

HOSTLOADLIBES_tracex4 += -lelf -lrt

HOSTLOADLIBES_tracex5 += -lelf

HOSTLOADLIBES_tracex6 += -lelf

HOSTLOADLIBES_lathist += -lelf



# point this to your LLVM backend with bpf support

samples/bpf/bpf_helpers.h

+2 −0
Original line number Diff line number Diff line
@@ -31,6 +31,8 @@ static unsigned long long (*bpf_get_current_uid_gid)(void) = 
	(void *) BPF_FUNC_get_current_uid_gid;

static int (*bpf_get_current_comm)(void *buf, int buf_size) =

	(void *) BPF_FUNC_get_current_comm;

static int (*bpf_perf_event_read)(void *map, int index) =

	(void *) BPF_FUNC_perf_event_read;



/* llvm builtin functions that eBPF C program may use to

 * emit BPF_LD_ABS and BPF_LD_IND instructions

samples/bpf/tracex6_kern.c

0 → 100644
+26 −0
Original line number Diff line number Diff line 
#include <linux/version.h>

#include <uapi/linux/bpf.h>

#include "bpf_helpers.h"



struct bpf_map_def SEC("maps") my_map = {

	.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,

	.key_size = sizeof(int),

	.value_size = sizeof(u32),

	.max_entries = 32,

};



SEC("kprobe/sys_write")

int bpf_prog1(struct pt_regs *ctx)

{

	u64 count;

	u32 key = bpf_get_smp_processor_id();

	char fmt[] = "CPU-%d   %llu\n";



	count = bpf_perf_event_read(&my_map, key);

	bpf_trace_printk(fmt, sizeof(fmt), key, count);



	return 0;

}



char _license[] SEC("license") = "GPL";

u32 _version SEC("version") = LINUX_VERSION_CODE;

samples/bpf/tracex6_user.c

0 → 100644
+68 −0
Original line number Diff line number Diff line 
#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <stdbool.h>

#include <string.h>

#include <fcntl.h>

#include <poll.h>

#include <sys/ioctl.h>

#include <linux/perf_event.h>

#include <linux/bpf.h>

#include "libbpf.h"

#include "bpf_load.h"



#define SAMPLE_PERIOD  0x7fffffffffffffffULL



static void test_bpf_perf_event(void)

{

	int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);

	int *pmu_fd = malloc(nr_cpus * sizeof(int));

	unsigned long value;

	int i;



	struct perf_event_attr attr_insn_pmu = {

		.freq = 0,

		.sample_period = SAMPLE_PERIOD,

		.inherit = 0,

		.type = PERF_TYPE_HARDWARE,

		.read_format = 0,

		.sample_type = 0,

		.config = 0,/* PMU: cycles */

	};



	for (i = 0; i < nr_cpus; i++) {

		pmu_fd[i] = perf_event_open(&attr_insn_pmu, -1/*pid*/, i/*cpu*/, -1/*group_fd*/, 0);

		if (pmu_fd[i] < 0)

			printf("event syscall failed\n");



		bpf_update_elem(map_fd[0], &i, &pmu_fd[i], BPF_ANY);

		ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0);

	}



	system("ls");

	system("pwd");

	system("sleep 2");



	for (i = 0; i < nr_cpus; i++)

		close(pmu_fd[i]);



	close(map_fd);



	free(pmu_fd);

}



int main(int argc, char **argv)

{

	char filename[256];



	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);



	if (load_bpf_file(filename)) {

		printf("%s", bpf_log_buf);

		return 1;

	}



	test_bpf_perf_event();



	return 0;

}