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 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