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Commit 1c47910e authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

samples/bpf: add perf_event+bpf example 



The bpf program is called 50 times a second and does hashmap[kern&user_stackid]++
It's primary purpose to check that key bpf helpers like map lookup, update,
get_stackid, trace_printk and ctx access are all working.
It checks:
- PERF_COUNT_HW_CPU_CYCLES on all cpus
- PERF_COUNT_HW_CPU_CYCLES for current process and inherited perf_events to children
- PERF_COUNT_SW_CPU_CLOCK on all cpus
- PERF_COUNT_SW_CPU_CLOCK for current process

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent aa6a5f3c

samples/bpf/Makefile

+4 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ hostprogs-y += test_cgrp2_array_pin 
hostprogs-y += xdp1

hostprogs-y += xdp2

hostprogs-y += test_current_task_under_cgroup

hostprogs-y += trace_event



test_verifier-objs := test_verifier.o libbpf.o

test_maps-objs := test_maps.o libbpf.o
@@ -52,6 +53,7 @@ xdp1-objs := bpf_load.o libbpf.o xdp1_user.o 
xdp2-objs := bpf_load.o libbpf.o xdp1_user.o

test_current_task_under_cgroup-objs := bpf_load.o libbpf.o \

				       test_current_task_under_cgroup_user.o

trace_event-objs := bpf_load.o libbpf.o trace_event_user.o



# Tell kbuild to always build the programs

always := $(hostprogs-y)
@@ -79,6 +81,7 @@ always += test_cgrp2_tc_kern.o 
always += xdp1_kern.o

always += xdp2_kern.o

always += test_current_task_under_cgroup_kern.o

always += trace_event_kern.o



HOSTCFLAGS += -I$(objtree)/usr/include
@@ -103,6 +106,7 @@ HOSTLOADLIBES_test_overhead += -lelf -lrt 
HOSTLOADLIBES_xdp1 += -lelf

HOSTLOADLIBES_xdp2 += -lelf

HOSTLOADLIBES_test_current_task_under_cgroup += -lelf

HOSTLOADLIBES_trace_event += -lelf



# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:

#  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang

samples/bpf/bpf_helpers.h

+2 −0
Original line number Diff line number Diff line
@@ -55,6 +55,8 @@ static int (*bpf_skb_get_tunnel_opt)(void *ctx, void *md, int size) = 
	(void *) BPF_FUNC_skb_get_tunnel_opt;

static int (*bpf_skb_set_tunnel_opt)(void *ctx, void *md, int size) =

	(void *) BPF_FUNC_skb_set_tunnel_opt;

static unsigned long long (*bpf_get_prandom_u32)(void) =

	(void *) BPF_FUNC_get_prandom_u32;



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

 * emit BPF_LD_ABS and BPF_LD_IND instructions

samples/bpf/bpf_load.c

+6 −1
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size) 
	bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;

	bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;

	bool is_xdp = strncmp(event, "xdp", 3) == 0;

	bool is_perf_event = strncmp(event, "perf_event", 10) == 0;

	enum bpf_prog_type prog_type;

	char buf[256];

	int fd, efd, err, id;
@@ -69,6 +70,8 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size) 
		prog_type = BPF_PROG_TYPE_TRACEPOINT;

	} else if (is_xdp) {

		prog_type = BPF_PROG_TYPE_XDP;

	} else if (is_perf_event) {

		prog_type = BPF_PROG_TYPE_PERF_EVENT;

	} else {

		printf("Unknown event '%s'\n", event);

		return -1;
@@ -82,7 +85,7 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size) 


	prog_fd[prog_cnt++] = fd;



	if (is_xdp)

	if (is_xdp || is_perf_event)

		return 0;



	if (is_socket) {
@@ -326,6 +329,7 @@ int load_bpf_file(char *path) 
			    memcmp(shname_prog, "kretprobe/", 10) == 0 ||

			    memcmp(shname_prog, "tracepoint/", 11) == 0 ||

			    memcmp(shname_prog, "xdp", 3) == 0 ||

			    memcmp(shname_prog, "perf_event", 10) == 0 ||

			    memcmp(shname_prog, "socket", 6) == 0)

				load_and_attach(shname_prog, insns, data_prog->d_size);

		}
@@ -344,6 +348,7 @@ int load_bpf_file(char *path) 
		    memcmp(shname, "kretprobe/", 10) == 0 ||

		    memcmp(shname, "tracepoint/", 11) == 0 ||

		    memcmp(shname, "xdp", 3) == 0 ||

		    memcmp(shname, "perf_event", 10) == 0 ||

		    memcmp(shname, "socket", 6) == 0)

			load_and_attach(shname, data->d_buf, data->d_size);

	}

samples/bpf/trace_event_kern.c

0 → 100644
+65 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2016 Facebook

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 */

#include <linux/ptrace.h>

#include <linux/version.h>

#include <uapi/linux/bpf.h>

#include <uapi/linux/bpf_perf_event.h>

#include <uapi/linux/perf_event.h>

#include "bpf_helpers.h"



struct key_t {

	char comm[TASK_COMM_LEN];

	u32 kernstack;

	u32 userstack;

};



struct bpf_map_def SEC("maps") counts = {

	.type = BPF_MAP_TYPE_HASH,

	.key_size = sizeof(struct key_t),

	.value_size = sizeof(u64),

	.max_entries = 10000,

};



struct bpf_map_def SEC("maps") stackmap = {

	.type = BPF_MAP_TYPE_STACK_TRACE,

	.key_size = sizeof(u32),

	.value_size = PERF_MAX_STACK_DEPTH * sizeof(u64),

	.max_entries = 10000,

};



#define KERN_STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)

#define USER_STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP | BPF_F_USER_STACK)



SEC("perf_event")

int bpf_prog1(struct bpf_perf_event_data *ctx)

{

	char fmt[] = "CPU-%d period %lld ip %llx";

	u32 cpu = bpf_get_smp_processor_id();

	struct key_t key;

	u64 *val, one = 1;



	if (ctx->sample_period < 10000)

		/* ignore warmup */

		return 0;

	bpf_get_current_comm(&key.comm, sizeof(key.comm));

	key.kernstack = bpf_get_stackid(ctx, &stackmap, KERN_STACKID_FLAGS);

	key.userstack = bpf_get_stackid(ctx, &stackmap, USER_STACKID_FLAGS);

	if ((int)key.kernstack < 0 && (int)key.userstack < 0) {

		bpf_trace_printk(fmt, sizeof(fmt), cpu, ctx->sample_period,

				 ctx->regs.ip);

		return 0;

	}



	val = bpf_map_lookup_elem(&counts, &key);

	if (val)

		(*val)++;

	else

		bpf_map_update_elem(&counts, &key, &one, BPF_NOEXIST);

	return 0;

}



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

samples/bpf/trace_event_user.c

0 → 100644
+213 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2016 Facebook

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 */

#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 <signal.h>

#include <assert.h>

#include <errno.h>

#include <sys/resource.h>

#include "libbpf.h"

#include "bpf_load.h"



#define SAMPLE_FREQ 50



static bool sys_read_seen, sys_write_seen;



static void print_ksym(__u64 addr)

{

	struct ksym *sym;



	if (!addr)

		return;

	sym = ksym_search(addr);

	printf("%s;", sym->name);

	if (!strcmp(sym->name, "sys_read"))

		sys_read_seen = true;

	else if (!strcmp(sym->name, "sys_write"))

		sys_write_seen = true;

}



static void print_addr(__u64 addr)

{

	if (!addr)

		return;

	printf("%llx;", addr);

}



#define TASK_COMM_LEN 16



struct key_t {

	char comm[TASK_COMM_LEN];

	__u32 kernstack;

	__u32 userstack;

};



static void print_stack(struct key_t *key, __u64 count)

{

	__u64 ip[PERF_MAX_STACK_DEPTH] = {};

	static bool warned;

	int i;



	printf("%3lld %s;", count, key->comm);

	if (bpf_lookup_elem(map_fd[1], &key->kernstack, ip) != 0) {

		printf("---;");

	} else {

		for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--)

			print_ksym(ip[i]);

	}

	printf("-;");

	if (bpf_lookup_elem(map_fd[1], &key->userstack, ip) != 0) {

		printf("---;");

	} else {

		for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--)

			print_addr(ip[i]);

	}

	printf("\n");



	if (key->kernstack == -EEXIST && !warned) {

		printf("stackmap collisions seen. Consider increasing size\n");

		warned = true;

	} else if ((int)key->kernstack < 0 && (int)key->userstack < 0) {

		printf("err stackid %d %d\n", key->kernstack, key->userstack);

	}

}



static void int_exit(int sig)

{

	kill(0, SIGKILL);

	exit(0);

}



static void print_stacks(void)

{

	struct key_t key = {}, next_key;

	__u64 value;

	__u32 stackid = 0, next_id;

	int fd = map_fd[0], stack_map = map_fd[1];



	sys_read_seen = sys_write_seen = false;

	while (bpf_get_next_key(fd, &key, &next_key) == 0) {

		bpf_lookup_elem(fd, &next_key, &value);

		print_stack(&next_key, value);

		bpf_delete_elem(fd, &next_key);

		key = next_key;

	}



	if (!sys_read_seen || !sys_write_seen) {

		printf("BUG kernel stack doesn't contain sys_read() and sys_write()\n");

		int_exit(0);

	}



	/* clear stack map */

	while (bpf_get_next_key(stack_map, &stackid, &next_id) == 0) {

		bpf_delete_elem(stack_map, &next_id);

		stackid = next_id;

	}

}



static void test_perf_event_all_cpu(struct perf_event_attr *attr)

{

	int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);

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

	int i;



	/* open perf_event on all cpus */

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

		pmu_fd[i] = perf_event_open(attr, -1, i, -1, 0);

		if (pmu_fd[i] < 0) {

			printf("perf_event_open failed\n");

			goto all_cpu_err;

		}

		assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);

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

	}

	system("dd if=/dev/zero of=/dev/null count=5000k");

	print_stacks();

all_cpu_err:

	for (i--; i >= 0; i--)

		close(pmu_fd[i]);

	free(pmu_fd);

}



static void test_perf_event_task(struct perf_event_attr *attr)

{

	int pmu_fd;



	/* open task bound event */

	pmu_fd = perf_event_open(attr, 0, -1, -1, 0);

	if (pmu_fd < 0) {

		printf("perf_event_open failed\n");

		return;

	}

	assert(ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);

	assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0) == 0);

	system("dd if=/dev/zero of=/dev/null count=5000k");

	print_stacks();

	close(pmu_fd);

}



static void test_bpf_perf_event(void)

{

	struct perf_event_attr attr_type_hw = {

		.sample_freq = SAMPLE_FREQ,

		.freq = 1,

		.type = PERF_TYPE_HARDWARE,

		.config = PERF_COUNT_HW_CPU_CYCLES,

		.inherit = 1,

	};

	struct perf_event_attr attr_type_sw = {

		.sample_freq = SAMPLE_FREQ,

		.freq = 1,

		.type = PERF_TYPE_SOFTWARE,

		.config = PERF_COUNT_SW_CPU_CLOCK,

		.inherit = 1,

	};



	test_perf_event_all_cpu(&attr_type_hw);

	test_perf_event_task(&attr_type_hw);

	test_perf_event_all_cpu(&attr_type_sw);

	test_perf_event_task(&attr_type_sw);

}





int main(int argc, char **argv)

{

	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};

	char filename[256];



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

	setrlimit(RLIMIT_MEMLOCK, &r);



	signal(SIGINT, int_exit);



	if (load_kallsyms()) {

		printf("failed to process /proc/kallsyms\n");

		return 1;

	}



	if (load_bpf_file(filename)) {

		printf("%s", bpf_log_buf);

		return 2;

	}



	if (fork() == 0) {

		read_trace_pipe();

		return 0;

	}

	test_bpf_perf_event();



	int_exit(0);

	return 0;

}