1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (C) 2025. Huawei Technologies Co., Ltd */ 3 #include <linux/bpf.h> 4 #include <time.h> 5 #include <bpf/bpf_tracing.h> 6 #include <bpf/bpf_helpers.h> 7 8 #define MAX_ENTRIES 8 9 10 struct map_value { 11 struct bpf_timer timer; 12 }; 13 14 struct { 15 __uint(type, BPF_MAP_TYPE_HASH); 16 __type(key, int); 17 __type(value, struct map_value); 18 __uint(max_entries, MAX_ENTRIES); 19 } map SEC(".maps"); 20 21 static int timer_cb(void *map, void *key, struct map_value *value) 22 { 23 volatile int sum = 0; 24 int i; 25 26 bpf_for(i, 0, 1024 * 1024) sum += i; 27 28 return 0; 29 } 30 31 static int start_cb(int key) 32 { 33 struct map_value *value; 34 35 value = bpf_map_lookup_elem(&map, (void *)&key); 36 if (!value) 37 return 0; 38 39 bpf_timer_init(&value->timer, &map, CLOCK_MONOTONIC); 40 bpf_timer_set_callback(&value->timer, timer_cb); 41 /* Hope 100us will be enough to wake-up and run the overwrite thread */ 42 bpf_timer_start(&value->timer, 100000, BPF_F_TIMER_CPU_PIN); 43 44 return 0; 45 } 46 47 static int overwrite_cb(int key) 48 { 49 struct map_value zero = {}; 50 51 /* Free the timer which may run on other CPU */ 52 bpf_map_update_elem(&map, (void *)&key, &zero, BPF_ANY); 53 54 return 0; 55 } 56 57 SEC("syscall") 58 int BPF_PROG(start_timer) 59 { 60 bpf_loop(MAX_ENTRIES, start_cb, NULL, 0); 61 return 0; 62 } 63 64 SEC("syscall") 65 int BPF_PROG(overwrite_timer) 66 { 67 bpf_loop(MAX_ENTRIES, overwrite_cb, NULL, 0); 68 return 0; 69 } 70 71 char _license[] SEC("license") = "GPL"; 72