// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2020 Facebook
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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char _license[] SEC("license") = "GPL";
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struct sample {
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int pid;
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int seq;
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long value;
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char comm[16];
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};
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struct {
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__uint(type, BPF_MAP_TYPE_RINGBUF);
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__uint(max_entries, 1 << 12);
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} ringbuf SEC(".maps");
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/* inputs */
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int pid = 0;
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long value = 0;
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long flags = 0;
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/* outputs */
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long total = 0;
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long discarded = 0;
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long dropped = 0;
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long avail_data = 0;
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long ring_size = 0;
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long cons_pos = 0;
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long prod_pos = 0;
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/* inner state */
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long seq = 0;
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SEC("tp/syscalls/sys_enter_getpgid")
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int test_ringbuf(void *ctx)
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{
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int cur_pid = bpf_get_current_pid_tgid() >> 32;
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struct sample *sample;
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int zero = 0;
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if (cur_pid != pid)
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return 0;
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sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
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if (!sample) {
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__sync_fetch_and_add(&dropped, 1);
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return 1;
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}
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sample->pid = pid;
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bpf_get_current_comm(sample->comm, sizeof(sample->comm));
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sample->value = value;
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sample->seq = seq++;
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__sync_fetch_and_add(&total, 1);
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if (sample->seq & 1) {
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/* copy from reserved sample to a new one... */
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bpf_ringbuf_output(&ringbuf, sample, sizeof(*sample), flags);
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/* ...and then discard reserved sample */
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bpf_ringbuf_discard(sample, flags);
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__sync_fetch_and_add(&discarded, 1);
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} else {
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bpf_ringbuf_submit(sample, flags);
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}
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avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
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ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
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cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
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prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
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return 0;
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}
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