root/tools/testing/selftests/bpf/progs/test_stacktrace_map.c

DEFINITIONS

1. SEC

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2018 Facebook
   3 
   4 #include <linux/bpf.h>
   5 #include "bpf_helpers.h"
   6 
   7 #ifndef PERF_MAX_STACK_DEPTH
   8 #define PERF_MAX_STACK_DEPTH         127
   9 #endif
  10 
  11 struct {
  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 
  18 struct {
  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 
  25 typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
  26 
  27 struct {
  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 
  34 struct {
  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 */
  42 struct 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 
  53 SEC("tracepoint/sched/sched_switch")
  54 int 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 
  76 char _license[] SEC("license") = "GPL";
  77 __u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */