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