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 struct bpf_stack_build_id stack_trace_t[PERF_MAX_STACK_DEPTH]; 26 27 struct { 28 __uint(type, BPF_MAP_TYPE_STACK_TRACE); 29 __uint(max_entries, 128); 30 __uint(map_flags, BPF_F_STACK_BUILD_ID); 31 __uint(key_size, sizeof(__u32)); 32 __uint(value_size, sizeof(stack_trace_t)); 33 } stackmap SEC(".maps"); 34 35 struct { 36 __uint(type, BPF_MAP_TYPE_ARRAY); 37 __uint(max_entries, 128); 38 __type(key, __u32); 39 /* there seems to be a bug in kernel not handling typedef properly */ 40 struct bpf_stack_build_id (*value)[PERF_MAX_STACK_DEPTH]; 41 } stack_amap SEC(".maps"); 42 43 /* taken from /sys/kernel/debug/tracing/events/random/urandom_read/format */ 44 struct random_urandom_args { 45 unsigned long long pad; 46 int got_bits; 47 int pool_left; 48 int input_left; 49 }; 50 51 SEC("tracepoint/random/urandom_read") 52 int oncpu(struct random_urandom_args *args) 53 { 54 __u32 max_len = sizeof(struct bpf_stack_build_id) 55 * PERF_MAX_STACK_DEPTH; 56 __u32 key = 0, val = 0, *value_p; 57 void *stack_p; 58 59 value_p = bpf_map_lookup_elem(&control_map, &key); 60 if (value_p && *value_p) 61 return 0; /* skip if non-zero *value_p */ 62 63 /* The size of stackmap and stackid_hmap should be the same */ 64 key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK); 65 if ((int)key >= 0) { 66 bpf_map_update_elem(&stackid_hmap, &key, &val, 0); 67 stack_p = bpf_map_lookup_elem(&stack_amap, &key); 68 if (stack_p) 69 bpf_get_stack(args, stack_p, max_len, 70 BPF_F_USER_STACK | BPF_F_USER_BUILD_ID); 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 */ 78