303 lines
6.8 KiB
C
303 lines
6.8 KiB
C
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
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/*
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* Ring buffer operations.
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*
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* Copyright (C) 2020 Facebook, Inc.
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*/
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#ifndef _GNU_SOURCE
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#define _GNU_SOURCE
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#endif
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <linux/err.h>
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#include <linux/bpf.h>
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#include <asm/barrier.h>
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#include <sys/mman.h>
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#include <sys/epoll.h>
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#include "libbpf.h"
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#include "libbpf_internal.h"
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#include "bpf.h"
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struct ring {
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ring_buffer_sample_fn sample_cb;
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void *ctx;
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void *data;
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unsigned long *consumer_pos;
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unsigned long *producer_pos;
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unsigned long mask;
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int map_fd;
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};
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struct ring_buffer {
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struct epoll_event *events;
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struct ring *rings;
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size_t page_size;
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int epoll_fd;
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int ring_cnt;
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};
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static void ringbuf_unmap_ring(struct ring_buffer *rb, struct ring *r)
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{
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if (r->consumer_pos) {
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munmap(r->consumer_pos, rb->page_size);
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r->consumer_pos = NULL;
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}
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if (r->producer_pos) {
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munmap(r->producer_pos, rb->page_size + 2 * (r->mask + 1));
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r->producer_pos = NULL;
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}
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}
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/* Add extra RINGBUF maps to this ring buffer manager */
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int ring_buffer__add(struct ring_buffer *rb, int map_fd,
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ring_buffer_sample_fn sample_cb, void *ctx)
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{
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struct bpf_map_info info;
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__u32 len = sizeof(info);
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struct epoll_event *e;
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struct ring *r;
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void *tmp;
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int err;
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memset(&info, 0, sizeof(info));
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err = bpf_obj_get_info_by_fd(map_fd, &info, &len);
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if (err) {
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err = -errno;
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pr_warn("ringbuf: failed to get map info for fd=%d: %d\n",
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map_fd, err);
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return libbpf_err(err);
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}
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if (info.type != BPF_MAP_TYPE_RINGBUF) {
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pr_warn("ringbuf: map fd=%d is not BPF_MAP_TYPE_RINGBUF\n",
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map_fd);
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return libbpf_err(-EINVAL);
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}
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tmp = libbpf_reallocarray(rb->rings, rb->ring_cnt + 1, sizeof(*rb->rings));
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if (!tmp)
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return libbpf_err(-ENOMEM);
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rb->rings = tmp;
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tmp = libbpf_reallocarray(rb->events, rb->ring_cnt + 1, sizeof(*rb->events));
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if (!tmp)
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return libbpf_err(-ENOMEM);
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rb->events = tmp;
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r = &rb->rings[rb->ring_cnt];
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memset(r, 0, sizeof(*r));
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r->map_fd = map_fd;
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r->sample_cb = sample_cb;
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r->ctx = ctx;
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r->mask = info.max_entries - 1;
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/* Map writable consumer page */
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tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED,
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map_fd, 0);
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if (tmp == MAP_FAILED) {
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err = -errno;
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pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
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map_fd, err);
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return libbpf_err(err);
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}
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r->consumer_pos = tmp;
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/* Map read-only producer page and data pages. We map twice as big
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* data size to allow simple reading of samples that wrap around the
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* end of a ring buffer. See kernel implementation for details.
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* */
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tmp = mmap(NULL, rb->page_size + 2 * info.max_entries, PROT_READ,
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MAP_SHARED, map_fd, rb->page_size);
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if (tmp == MAP_FAILED) {
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err = -errno;
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ringbuf_unmap_ring(rb, r);
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pr_warn("ringbuf: failed to mmap data pages for map fd=%d: %d\n",
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map_fd, err);
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return libbpf_err(err);
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}
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r->producer_pos = tmp;
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r->data = tmp + rb->page_size;
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e = &rb->events[rb->ring_cnt];
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memset(e, 0, sizeof(*e));
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e->events = EPOLLIN;
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e->data.fd = rb->ring_cnt;
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if (epoll_ctl(rb->epoll_fd, EPOLL_CTL_ADD, map_fd, e) < 0) {
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err = -errno;
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ringbuf_unmap_ring(rb, r);
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pr_warn("ringbuf: failed to epoll add map fd=%d: %d\n",
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map_fd, err);
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return libbpf_err(err);
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}
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rb->ring_cnt++;
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return 0;
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}
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void ring_buffer__free(struct ring_buffer *rb)
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{
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int i;
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if (!rb)
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return;
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for (i = 0; i < rb->ring_cnt; ++i)
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ringbuf_unmap_ring(rb, &rb->rings[i]);
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if (rb->epoll_fd >= 0)
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close(rb->epoll_fd);
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free(rb->events);
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free(rb->rings);
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free(rb);
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}
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struct ring_buffer *
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ring_buffer__new(int map_fd, ring_buffer_sample_fn sample_cb, void *ctx,
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const struct ring_buffer_opts *opts)
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{
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struct ring_buffer *rb;
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int err;
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if (!OPTS_VALID(opts, ring_buffer_opts))
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return errno = EINVAL, NULL;
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rb = calloc(1, sizeof(*rb));
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if (!rb)
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return errno = ENOMEM, NULL;
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rb->page_size = getpagesize();
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rb->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
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if (rb->epoll_fd < 0) {
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err = -errno;
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pr_warn("ringbuf: failed to create epoll instance: %d\n", err);
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goto err_out;
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}
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err = ring_buffer__add(rb, map_fd, sample_cb, ctx);
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if (err)
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goto err_out;
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return rb;
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err_out:
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ring_buffer__free(rb);
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return errno = -err, NULL;
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}
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static inline int roundup_len(__u32 len)
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{
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/* clear out top 2 bits (discard and busy, if set) */
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len <<= 2;
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len >>= 2;
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/* add length prefix */
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len += BPF_RINGBUF_HDR_SZ;
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/* round up to 8 byte alignment */
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return (len + 7) / 8 * 8;
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}
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static int64_t ringbuf_process_ring(struct ring* r)
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{
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int *len_ptr, len, err;
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/* 64-bit to avoid overflow in case of extreme application behavior */
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int64_t cnt = 0;
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unsigned long cons_pos, prod_pos;
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bool got_new_data;
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void *sample;
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cons_pos = smp_load_acquire(r->consumer_pos);
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do {
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got_new_data = false;
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prod_pos = smp_load_acquire(r->producer_pos);
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while (cons_pos < prod_pos) {
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len_ptr = r->data + (cons_pos & r->mask);
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len = smp_load_acquire(len_ptr);
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/* sample not committed yet, bail out for now */
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if (len & BPF_RINGBUF_BUSY_BIT)
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goto done;
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got_new_data = true;
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cons_pos += roundup_len(len);
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if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
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sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
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err = r->sample_cb(r->ctx, sample, len);
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if (err < 0) {
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/* update consumer pos and bail out */
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smp_store_release(r->consumer_pos,
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cons_pos);
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return err;
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}
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cnt++;
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}
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smp_store_release(r->consumer_pos, cons_pos);
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}
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} while (got_new_data);
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done:
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return cnt;
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}
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/* Consume available ring buffer(s) data without event polling.
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* Returns number of records consumed across all registered ring buffers (or
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* INT_MAX, whichever is less), or negative number if any of the callbacks
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* return error.
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*/
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int ring_buffer__consume(struct ring_buffer *rb)
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{
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int64_t err, res = 0;
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int i;
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for (i = 0; i < rb->ring_cnt; i++) {
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struct ring *ring = &rb->rings[i];
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err = ringbuf_process_ring(ring);
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if (err < 0)
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return libbpf_err(err);
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res += err;
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}
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if (res > INT_MAX)
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return INT_MAX;
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return res;
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}
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/* Poll for available data and consume records, if any are available.
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* Returns number of records consumed (or INT_MAX, whichever is less), or
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* negative number, if any of the registered callbacks returned error.
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*/
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int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
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{
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int i, cnt;
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int64_t err, res = 0;
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cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms);
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if (cnt < 0)
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return libbpf_err(-errno);
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for (i = 0; i < cnt; i++) {
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__u32 ring_id = rb->events[i].data.fd;
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struct ring *ring = &rb->rings[ring_id];
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err = ringbuf_process_ring(ring);
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if (err < 0)
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return libbpf_err(err);
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res += err;
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}
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if (res > INT_MAX)
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return INT_MAX;
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return res;
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}
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/* Get an fd that can be used to sleep until data is available in the ring(s) */
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int ring_buffer__epoll_fd(const struct ring_buffer *rb)
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{
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return rb->epoll_fd;
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}
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