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 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 __type(value, stack_trace_t); 40 } stack_amap SEC(".maps"); 41 42 /* taken from /sys/kernel/debug/tracing/events/random/urandom_read/format */ 43 struct random_urandom_args { 44 unsigned long long pad; 45 int got_bits; 46 int pool_left; 47 int input_left; 48 }; 49 50 SEC("tracepoint/random/urandom_read") 51 int oncpu(struct random_urandom_args *args) 52 { 53 __u32 max_len = sizeof(struct bpf_stack_build_id) 54 * PERF_MAX_STACK_DEPTH; 55 __u32 key = 0, val = 0, *value_p; 56 void *stack_p; 57 58 value_p = bpf_map_lookup_elem(&control_map, &key); 59 if (value_p && *value_p) 60 return 0; /* skip if non-zero *value_p */ 61 62 /* The size of stackmap and stackid_hmap should be the same */ 63 key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK); 64 if ((int)key >= 0) { 65 bpf_map_update_elem(&stackid_hmap, &key, &val, 0); 66 stack_p = bpf_map_lookup_elem(&stack_amap, &key); 67 if (stack_p) 68 bpf_get_stack(args, stack_p, max_len, 69 BPF_F_USER_STACK | BPF_F_USER_BUILD_ID); 70 } 71 72 return 0; 73 } 74 75 char _license[] SEC("license") = "GPL"; 76 __u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */ 77