samples/bpf: add perf_event+bpf example

[cascardo/linux.git] / samples / bpf / trace_event_kern.c

diff --git a/samples/bpf/trace_event_kern.c b/samples/bpf/trace_event_kern.c
new file mode 100644 (file)
index 0000000..71a8ed3
--- /dev/null
+++ b/samples/bpf/trace_event_kern.c
@@ -0,0 +1,65 @@
+/* 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";