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// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2025. Huawei Technologies Co., Ltd */
#include <linux/bpf.h>
#include <time.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_helpers.h>
#define MAX_ENTRIES 8
struct map_value {
struct bpf_timer timer;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__type(key, int);
__type(value, struct map_value);
__uint(max_entries, MAX_ENTRIES);
} map SEC(".maps");
static int timer_cb(void *map, void *key, struct map_value *value)
{
volatile int sum = 0;
int i;
bpf_for(i, 0, 1024 * 1024) sum += i;
return 0;
}
static int start_cb(int key)
{
struct map_value *value;
value = bpf_map_lookup_elem(&map, (void *)&key);
if (!value)
return 0;
bpf_timer_init(&value->timer, &map, CLOCK_MONOTONIC);
bpf_timer_set_callback(&value->timer, timer_cb);
/* Hope 100us will be enough to wake-up and run the overwrite thread */
bpf_timer_start(&value->timer, 100000, BPF_F_TIMER_CPU_PIN);
return 0;
}
static int overwrite_cb(int key)
{
struct map_value zero = {};
/* Free the timer which may run on other CPU */
bpf_map_update_elem(&map, (void *)&key, &zero, BPF_ANY);
return 0;
}
SEC("syscall")
int BPF_PROG(start_timer)
{
bpf_loop(MAX_ENTRIES, start_cb, NULL, 0);
return 0;
}
SEC("syscall")
int BPF_PROG(overwrite_timer)
{
bpf_loop(MAX_ENTRIES, overwrite_cb, NULL, 0);
return 0;
}
char _license[] SEC("license") = "GPL";
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