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475 lines
13 KiB
475 lines
13 KiB
#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 <uapi/linux/btf.h> |
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|
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#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE) |
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|
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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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|
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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_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_ACCOUNT | __GFP_RETRY_MAYFAIL | |
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__GFP_NOWARN | __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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pages = bpf_map_area_alloc(array_size, 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_ALLOC | VM_USERMAP, PAGE_KERNEL); |
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if (rb) { |
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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 NULL; |
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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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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 | __GFP_ACCOUNT); |
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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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rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node); |
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if (!rb_map->rb) { |
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kfree(rb_map); |
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return ERR_PTR(-ENOMEM); |
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} |
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return &rb_map->map; |
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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); |
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/* if consumer caught up and is waiting for our record, notify about |
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* new data availability |
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*/ |
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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 */); |
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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; |
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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); |
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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 */); |
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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, |
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}; |
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BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags) |
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{ |
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struct bpf_ringbuf *rb; |
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rb = container_of(map, struct bpf_ringbuf_map, map)->rb; |
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switch (flags) { |
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case BPF_RB_AVAIL_DATA: |
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return ringbuf_avail_data_sz(rb); |
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case BPF_RB_RING_SIZE: |
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return rb->mask + 1; |
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case BPF_RB_CONS_POS: |
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return smp_load_acquire(&rb->consumer_pos); |
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case BPF_RB_PROD_POS: |
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return smp_load_acquire(&rb->producer_pos); |
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default: |
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return 0; |
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} |
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} |
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const struct bpf_func_proto bpf_ringbuf_query_proto = { |
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.func = bpf_ringbuf_query, |
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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_ANYTHING, |
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};
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