#include <linux/bpf.h>
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#include <linux/btf.h>
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#include <linux/err.h>
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#include <linux/irq_work.h>
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#include <linux/slab.h>
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#include <linux/filter.h>
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#include <linux/mm.h>
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#include <linux/vmalloc.h>
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#include <linux/wait.h>
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#include <linux/poll.h>
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#include <linux/kmemleak.h>
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#include <uapi/linux/btf.h>
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#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
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/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */
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#define RINGBUF_PGOFF \
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(offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT)
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/* consumer page and producer page */
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#define RINGBUF_POS_PAGES 2
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#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
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/* Maximum size of ring buffer area is limited by 32-bit page offset within
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* record header, counted in pages. Reserve 8 bits for extensibility, and take
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* into account few extra pages for consumer/producer pages and
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* non-mmap()'able parts. This gives 64GB limit, which seems plenty for single
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* ring buffer.
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*/
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#define RINGBUF_MAX_DATA_SZ \
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(((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
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struct bpf_ringbuf {
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wait_queue_head_t waitq;
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struct irq_work work;
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u64 mask;
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struct page **pages;
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int nr_pages;
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spinlock_t spinlock ____cacheline_aligned_in_smp;
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/* Consumer and producer counters are put into separate pages to allow
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* mapping consumer page as r/w, but restrict producer page to r/o.
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* This protects producer position from being modified by user-space
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* application and ruining in-kernel position tracking.
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*/
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unsigned long consumer_pos __aligned(PAGE_SIZE);
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unsigned long producer_pos __aligned(PAGE_SIZE);
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char data[] __aligned(PAGE_SIZE);
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};
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struct bpf_ringbuf_map {
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struct bpf_map map;
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struct bpf_map_memory memory;
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struct bpf_ringbuf *rb;
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};
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/* 8-byte ring buffer record header structure */
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struct bpf_ringbuf_hdr {
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u32 len;
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u32 pg_off;
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};
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static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
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{
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const gfp_t flags = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN |
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__GFP_ZERO;
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int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
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int nr_data_pages = data_sz >> PAGE_SHIFT;
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int nr_pages = nr_meta_pages + nr_data_pages;
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struct page **pages, *page;
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struct bpf_ringbuf *rb;
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size_t array_size;
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int i;
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/* Each data page is mapped twice to allow "virtual"
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* continuous read of samples wrapping around the end of ring
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* buffer area:
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* ------------------------------------------------------
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* | meta pages | real data pages | same data pages |
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* ------------------------------------------------------
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* | | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
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* ------------------------------------------------------
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* | | TA DA | TA DA |
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* ------------------------------------------------------
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* ^^^^^^^
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* |
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* Here, no need to worry about special handling of wrapped-around
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* data due to double-mapped data pages. This works both in kernel and
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* when mmap()'ed in user-space, simplifying both kernel and
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* user-space implementations significantly.
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*/
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array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
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if (array_size > PAGE_SIZE)
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pages = vmalloc_node(array_size, numa_node);
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else
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pages = kmalloc_node(array_size, flags, numa_node);
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if (!pages)
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return NULL;
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for (i = 0; i < nr_pages; i++) {
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page = alloc_pages_node(numa_node, flags, 0);
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if (!page) {
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nr_pages = i;
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goto err_free_pages;
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}
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pages[i] = page;
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if (i >= nr_meta_pages)
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pages[nr_data_pages + i] = page;
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}
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rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
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VM_MAP | VM_USERMAP, PAGE_KERNEL);
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if (rb) {
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kmemleak_not_leak(pages);
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rb->pages = pages;
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rb->nr_pages = nr_pages;
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return rb;
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}
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err_free_pages:
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for (i = 0; i < nr_pages; i++)
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__free_page(pages[i]);
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kvfree(pages);
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return NULL;
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}
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static void bpf_ringbuf_notify(struct irq_work *work)
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{
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struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
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wake_up_all(&rb->waitq);
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}
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static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
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{
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struct bpf_ringbuf *rb;
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rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
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if (!rb)
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return ERR_PTR(-ENOMEM);
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spin_lock_init(&rb->spinlock);
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init_waitqueue_head(&rb->waitq);
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init_irq_work(&rb->work, bpf_ringbuf_notify);
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rb->mask = data_sz - 1;
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rb->consumer_pos = 0;
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rb->producer_pos = 0;
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return rb;
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}
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static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
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{
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struct bpf_ringbuf_map *rb_map;
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u64 cost;
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int err;
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if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
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return ERR_PTR(-EINVAL);
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if (attr->key_size || attr->value_size ||
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!is_power_of_2(attr->max_entries) ||
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!PAGE_ALIGNED(attr->max_entries))
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return ERR_PTR(-EINVAL);
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#ifdef CONFIG_64BIT
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/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
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if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
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return ERR_PTR(-E2BIG);
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#endif
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rb_map = kzalloc(sizeof(*rb_map), GFP_USER);
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if (!rb_map)
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return ERR_PTR(-ENOMEM);
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bpf_map_init_from_attr(&rb_map->map, attr);
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cost = sizeof(struct bpf_ringbuf_map) +
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sizeof(struct bpf_ringbuf) +
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attr->max_entries;
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err = bpf_map_charge_init(&rb_map->map.memory, cost);
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if (err)
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goto err_free_map;
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rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
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if (IS_ERR(rb_map->rb)) {
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err = PTR_ERR(rb_map->rb);
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goto err_uncharge;
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}
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return &rb_map->map;
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err_uncharge:
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bpf_map_charge_finish(&rb_map->map.memory);
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err_free_map:
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kfree(rb_map);
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return ERR_PTR(err);
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}
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static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
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{
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/* copy pages pointer and nr_pages to local variable, as we are going
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* to unmap rb itself with vunmap() below
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*/
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struct page **pages = rb->pages;
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int i, nr_pages = rb->nr_pages;
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vunmap(rb);
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for (i = 0; i < nr_pages; i++)
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__free_page(pages[i]);
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kvfree(pages);
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}
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static void ringbuf_map_free(struct bpf_map *map)
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{
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struct bpf_ringbuf_map *rb_map;
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rb_map = container_of(map, struct bpf_ringbuf_map, map);
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bpf_ringbuf_free(rb_map->rb);
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kfree(rb_map);
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}
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static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
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{
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return ERR_PTR(-ENOTSUPP);
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}
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static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
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u64 flags)
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{
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return -ENOTSUPP;
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}
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static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
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{
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return -ENOTSUPP;
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}
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static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
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void *next_key)
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{
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return -ENOTSUPP;
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}
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static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
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{
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struct bpf_ringbuf_map *rb_map;
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rb_map = container_of(map, struct bpf_ringbuf_map, map);
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if (vma->vm_flags & VM_WRITE) {
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/* allow writable mapping for the consumer_pos only */
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if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
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return -EPERM;
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} else {
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vma->vm_flags &= ~VM_MAYWRITE;
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}
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/* remap_vmalloc_range() checks size and offset constraints */
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return remap_vmalloc_range(vma, rb_map->rb,
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vma->vm_pgoff + RINGBUF_PGOFF);
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}
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static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
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{
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unsigned long cons_pos, prod_pos;
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cons_pos = smp_load_acquire(&rb->consumer_pos);
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prod_pos = smp_load_acquire(&rb->producer_pos);
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return prod_pos - cons_pos;
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}
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static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
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struct poll_table_struct *pts)
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{
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struct bpf_ringbuf_map *rb_map;
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rb_map = container_of(map, struct bpf_ringbuf_map, map);
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poll_wait(filp, &rb_map->rb->waitq, pts);
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if (ringbuf_avail_data_sz(rb_map->rb))
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return EPOLLIN | EPOLLRDNORM;
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return 0;
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}
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static int ringbuf_map_btf_id;
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const struct bpf_map_ops ringbuf_map_ops = {
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.map_meta_equal = bpf_map_meta_equal,
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.map_alloc = ringbuf_map_alloc,
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.map_free = ringbuf_map_free,
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.map_mmap = ringbuf_map_mmap,
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.map_poll = ringbuf_map_poll,
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.map_lookup_elem = ringbuf_map_lookup_elem,
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.map_update_elem = ringbuf_map_update_elem,
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.map_delete_elem = ringbuf_map_delete_elem,
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.map_get_next_key = ringbuf_map_get_next_key,
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.map_btf_name = "bpf_ringbuf_map",
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.map_btf_id = &ringbuf_map_btf_id,
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};
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/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
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* calculate offset from record metadata to ring buffer in pages, rounded
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* down. This page offset is stored as part of record metadata and allows to
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* restore struct bpf_ringbuf * from record pointer. This page offset is
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* stored at offset 4 of record metadata header.
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*/
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static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
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struct bpf_ringbuf_hdr *hdr)
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{
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return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
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}
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/* Given pointer to ring buffer record header, restore pointer to struct
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* bpf_ringbuf itself by using page offset stored at offset 4
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*/
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static struct bpf_ringbuf *
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bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
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{
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unsigned long addr = (unsigned long)(void *)hdr;
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unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
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return (void*)((addr & PAGE_MASK) - off);
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}
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static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
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{
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unsigned long cons_pos, prod_pos, new_prod_pos, flags;
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u32 len, pg_off;
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struct bpf_ringbuf_hdr *hdr;
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if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
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return NULL;
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len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
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if (len > rb->mask + 1)
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return NULL;
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cons_pos = smp_load_acquire(&rb->consumer_pos);
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if (in_nmi()) {
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if (!spin_trylock_irqsave(&rb->spinlock, flags))
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return NULL;
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} else {
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spin_lock_irqsave(&rb->spinlock, flags);
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}
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prod_pos = rb->producer_pos;
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new_prod_pos = prod_pos + len;
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/* check for out of ringbuf space by ensuring producer position
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* doesn't advance more than (ringbuf_size - 1) ahead
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*/
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if (new_prod_pos - cons_pos > rb->mask) {
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spin_unlock_irqrestore(&rb->spinlock, flags);
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return NULL;
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}
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hdr = (void *)rb->data + (prod_pos & rb->mask);
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pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
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hdr->len = size | BPF_RINGBUF_BUSY_BIT;
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hdr->pg_off = pg_off;
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/* pairs with consumer's smp_load_acquire() */
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smp_store_release(&rb->producer_pos, new_prod_pos);
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spin_unlock_irqrestore(&rb->spinlock, flags);
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return (void *)hdr + BPF_RINGBUF_HDR_SZ;
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}
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BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
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{
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struct bpf_ringbuf_map *rb_map;
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if (unlikely(flags))
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return 0;
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rb_map = container_of(map, struct bpf_ringbuf_map, map);
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return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
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}
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const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
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.func = bpf_ringbuf_reserve,
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.ret_type = RET_PTR_TO_ALLOC_MEM_OR_NULL,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_CONST_ALLOC_SIZE_OR_ZERO,
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.arg3_type = ARG_ANYTHING,
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};
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static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
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{
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unsigned long rec_pos, cons_pos;
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struct bpf_ringbuf_hdr *hdr;
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struct bpf_ringbuf *rb;
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u32 new_len;
|
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hdr = sample - BPF_RINGBUF_HDR_SZ;
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rb = bpf_ringbuf_restore_from_rec(hdr);
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new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
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if (discard)
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new_len |= BPF_RINGBUF_DISCARD_BIT;
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/* update record header with correct final size prefix */
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xchg(&hdr->len, new_len);
|
|
/* if consumer caught up and is waiting for our record, notify about
|
* new data availability
|
*/
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rec_pos = (void *)hdr - (void *)rb->data;
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cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
|
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if (flags & BPF_RB_FORCE_WAKEUP)
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irq_work_queue(&rb->work);
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else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
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irq_work_queue(&rb->work);
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}
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BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
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{
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bpf_ringbuf_commit(sample, flags, false /* discard */);
|
return 0;
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}
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const struct bpf_func_proto bpf_ringbuf_submit_proto = {
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.func = bpf_ringbuf_submit,
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.ret_type = RET_VOID,
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.arg1_type = ARG_PTR_TO_ALLOC_MEM,
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.arg2_type = ARG_ANYTHING,
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};
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BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
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{
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bpf_ringbuf_commit(sample, flags, true /* discard */);
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return 0;
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}
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const struct bpf_func_proto bpf_ringbuf_discard_proto = {
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.func = bpf_ringbuf_discard,
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.ret_type = RET_VOID,
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.arg1_type = ARG_PTR_TO_ALLOC_MEM,
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.arg2_type = ARG_ANYTHING,
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};
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BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
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u64, flags)
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{
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struct bpf_ringbuf_map *rb_map;
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void *rec;
|
|
if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
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return -EINVAL;
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rb_map = container_of(map, struct bpf_ringbuf_map, map);
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rec = __bpf_ringbuf_reserve(rb_map->rb, size);
|
if (!rec)
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return -EAGAIN;
|
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memcpy(rec, data, size);
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bpf_ringbuf_commit(rec, flags, false /* discard */);
|
return 0;
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}
|
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const struct bpf_func_proto bpf_ringbuf_output_proto = {
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.func = bpf_ringbuf_output,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_MEM,
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.arg3_type = ARG_CONST_SIZE_OR_ZERO,
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.arg4_type = ARG_ANYTHING,
|
};
|
|
BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
|
{
|
struct bpf_ringbuf *rb;
|
|
rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
|
|
switch (flags) {
|
case BPF_RB_AVAIL_DATA:
|
return ringbuf_avail_data_sz(rb);
|
case BPF_RB_RING_SIZE:
|
return rb->mask + 1;
|
case BPF_RB_CONS_POS:
|
return smp_load_acquire(&rb->consumer_pos);
|
case BPF_RB_PROD_POS:
|
return smp_load_acquire(&rb->producer_pos);
|
default:
|
return 0;
|
}
|
}
|
|
const struct bpf_func_proto bpf_ringbuf_query_proto = {
|
.func = bpf_ringbuf_query,
|
.ret_type = RET_INTEGER,
|
.arg1_type = ARG_CONST_MAP_PTR,
|
.arg2_type = ARG_ANYTHING,
|
};
|
