LXR linux/tools/testing/selftests/bpf/progs/test_stacktrace

   1// SPDX-License-Identifier: GPL-2.0
   2// Copyright (c) 2018 Facebook
   3
   4#include <linux/bpf.h>
   5#include <bpf/bpf_helpers.h>
   6
   7#ifndef PERF_MAX_STACK_DEPTH
   8#define PERF_MAX_STACK_DEPTH         127
   9#endif
  10
  11struct {
  12        __uint(type, BPF_MAP_TYPE_ARRAY);
  13        __uint(max_entries, 1);
  14        __type(key, __u32);
  15        __type(value, __u32);
  16} control_map SEC(".maps");
  17
  18struct {
  19        __uint(type, BPF_MAP_TYPE_HASH);
  20        __uint(max_entries, 16384);
  21        __type(key, __u32);
  22        __type(value, __u32);
  23} stackid_hmap SEC(".maps");
  24
  25typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
  26
  27struct {
  28        __uint(type, BPF_MAP_TYPE_STACK_TRACE);
  29        __uint(max_entries, 16384);
  30        __uint(key_size, sizeof(__u32));
  31        __uint(value_size, sizeof(stack_trace_t));
  32} stackmap SEC(".maps");
  33
  34struct {
  35        __uint(type, BPF_MAP_TYPE_ARRAY);
  36        __uint(max_entries, 16384);
  37        __type(key, __u32);
  38        __type(value, stack_trace_t);
  39} stack_amap SEC(".maps");
  40
  41/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
  42struct sched_switch_args {
  43        unsigned long long pad;
  44        char prev_comm[16];
  45        int prev_pid;
  46        int prev_prio;
  47        long long prev_state;
  48        char next_comm[16];
  49        int next_pid;
  50        int next_prio;
  51};
  52
  53SEC("tracepoint/sched/sched_switch")
  54int oncpu(struct sched_switch_args *ctx)
  55{
  56        __u32 max_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
  57        __u32 key = 0, val = 0, *value_p;
  58        void *stack_p;
  59
  60        value_p = bpf_map_lookup_elem(&control_map, &key);
  61        if (value_p && *value_p)
  62                return 0; /* skip if non-zero *value_p */
  63
  64        /* The size of stackmap and stackid_hmap should be the same */
  65        key = bpf_get_stackid(ctx, &stackmap, 0);
  66        if ((int)key >= 0) {
  67                bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
  68                stack_p = bpf_map_lookup_elem(&stack_amap, &key);
  69                if (stack_p)
  70                        bpf_get_stack(ctx, stack_p, max_len, 0);
  71        }
  72
  73        return 0;
  74}
  75
  76char _license[] SEC("license") = "GPL";
  77