linux/samples/bpf/trace_event_kern.c
Alexei Starovoitov 1c47910ef8 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: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-09-02 10:46:45 -07:00

66 lines
1.7 KiB
C

/* 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";