#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/err.h>
#include <linux/irq_work.h>
#include <linux/slab.h>
#include <linux/filter.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/kmemleak.h>
#include <uapi/linux/btf.h>
#include <linux/btf_ids.h>
#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */
#define RINGBUF_PGOFF \
(offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT)
/* consumer page and producer page */
#define RINGBUF_POS_PAGES 2
#define RINGBUF_NR_META_PAGES (RINGBUF_PGOFF + RINGBUF_POS_PAGES)
#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
struct bpf_ringbuf {
wait_queue_head_t waitq;
struct irq_work work;
u64 mask;
struct page **pages;
int nr_pages;
spinlock_t spinlock ____cacheline_aligned_in_smp;
/* For user-space producer ring buffers, an atomic_t busy bit is used
* to synchronize access to the ring buffers in the kernel, rather than
* the spinlock that is used for kernel-producer ring buffers. This is
* done because the ring buffer must hold a lock across a BPF program's
* callback:
*
* __bpf_user_ringbuf_peek() // lock acquired
* -> program callback_fn()
* -> __bpf_user_ringbuf_sample_release() // lock released
*
* It is unsafe and incorrect to hold an IRQ spinlock across what could
* be a long execution window, so we instead simply disallow concurrent
* access to the ring buffer by kernel consumers, and return -EBUSY from
* __bpf_user_ringbuf_peek() if the busy bit is held by another task.
*/
atomic_t busy ____cacheline_aligned_in_smp;
/* Consumer and producer counters are put into separate pages to
* allow each position to be mapped with different permissions.
* This prevents a user-space application from modifying the
* position and ruining in-kernel tracking. The permissions of the
* pages depend on who is producing samples: user-space or the
* kernel. Note that the pending counter is placed in the same
* page as the producer, so that it shares the same cache line.
*
* Kernel-producer
* ---------------
* The producer position and data pages are mapped as r/o in
* userspace. For this approach, bits in the header of samples are
* used to signal to user-space, and to other producers, whether a
* sample is currently being written.
*
* User-space producer
* -------------------
* Only the page containing the consumer position is mapped r/o in
* user-space. User-space producers also use bits of the header to
* communicate to the kernel, but the kernel must carefully check and
* validate each sample to ensure that they're correctly formatted, and
* fully contained within the ring buffer.
*/
unsigned long consumer_pos __aligned(PAGE_SIZE);
unsigned long producer_pos __aligned(PAGE_SIZE);
unsigned long pending_pos;
char data[] __aligned(PAGE_SIZE);
};
struct bpf_ringbuf_map {
struct bpf_map map;
struct bpf_ringbuf *rb;
};
/* 8-byte ring buffer record header structure */
struct bpf_ringbuf_hdr {
u32 len;
u32 pg_off;
};
static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
{
const gfp_t flags = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL |
__GFP_NOWARN | __GFP_ZERO;
int nr_meta_pages = RINGBUF_NR_META_PAGES;
int nr_data_pages = data_sz >> PAGE_SHIFT;
int nr_pages = nr_meta_pages + nr_data_pages;
struct page **pages, *page;
struct bpf_ringbuf *rb;
size_t array_size;
int i;
/* Each data page is mapped twice to allow "virtual"
* continuous read of samples wrapping around the end of ring
* buffer area:
* ------------------------------------------------------
* | meta pages | real data pages | same data pages |
* ------------------------------------------------------
* | | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
* ------------------------------------------------------
* | | TA DA | TA DA |
* ------------------------------------------------------
* ^^^^^^^
* |
* Here, no need to worry about special handling of wrapped-around
* data due to double-mapped data pages. This works both in kernel and
* when mmap()'ed in user-space, simplifying both kernel and
* user-space implementations significantly.
*/
array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
pages = bpf_map_area_alloc(array_size, numa_node);
if (!pages)
return NULL;
for (i = 0; i < nr_pages; i++) {
page = alloc_pages_node(numa_node, flags, 0);
if (!page) {
nr_pages = i;
goto err_free_pages;
}
pages[i] = page;
if (i >= nr_meta_pages)
pages[nr_data_pages + i] = page;
}
rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
VM_MAP | VM_USERMAP, PAGE_KERNEL);
if (rb) {
kmemleak_not_leak(pages);
rb->pages = pages;
rb->nr_pages = nr_pages;
return rb;
}
err_free_pages:
for (i = 0; i < nr_pages; i++)
__free_page(pages[i]);
bpf_map_area_free(pages);
return NULL;
}
static void bpf_ringbuf_notify(struct irq_work *work)
{
struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
wake_up_all(&rb->waitq);
}
/* Maximum size of ring buffer area is limited by 32-bit page offset within
* record header, counted in pages. Reserve 8 bits for extensibility, and
* take into account few extra pages for consumer/producer pages and
* non-mmap()'able parts, the current maximum size would be:
*
* (((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
*
* This gives 64GB limit, which seems plenty for single ring buffer. Now
* considering that the maximum value of data_sz is (4GB - 1), there
* will be no overflow, so just note the size limit in the comments.
*/
static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
{
struct bpf_ringbuf *rb;
rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
if (!rb)
return NULL;
spin_lock_init(&rb->spinlock);
atomic_set(&rb->busy, 0);
init_waitqueue_head(&rb->waitq);
init_irq_work(&rb->work, bpf_ringbuf_notify);
rb->mask = data_sz - 1;
rb->consumer_pos = 0;
rb->producer_pos = 0;
rb->pending_pos = 0;
return rb;
}
static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
{
struct bpf_ringbuf_map *rb_map;
if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
return ERR_PTR(-EINVAL);
if (attr->key_size || attr->value_size ||
!is_power_of_2(attr->max_entries) ||
!PAGE_ALIGNED(attr->max_entries))
return ERR_PTR(-EINVAL);
rb_map = bpf_map_area_alloc(sizeof(*rb_map), NUMA_NO_NODE);
if (!rb_map)
return ERR_PTR(-ENOMEM);
bpf_map_init_from_attr(&rb_map->map, attr);
rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
if (!rb_map->rb) {
bpf_map_area_free(rb_map);
return ERR_PTR(-ENOMEM);
}
return &rb_map->map;
}
static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
{
/* copy pages pointer and nr_pages to local variable, as we are going
* to unmap rb itself with vunmap() below
*/
struct page **pages = rb->pages;
int i, nr_pages = rb->nr_pages;
vunmap(rb);
for (i = 0; i < nr_pages; i++)
__free_page(pages[i]);
bpf_map_area_free(pages);
}
static void ringbuf_map_free(struct bpf_map *map)
{
struct bpf_ringbuf_map *rb_map;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
bpf_ringbuf_free(rb_map->rb);
bpf_map_area_free(rb_map);
}
static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
{
return ERR_PTR(-ENOTSUPP);
}
static long ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 flags)
{
return -ENOTSUPP;
}
static long ringbuf_map_delete_elem(struct bpf_map *map, void *key)
{
return -ENOTSUPP;
}
static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
void *next_key)
{
return -ENOTSUPP;
}
static int ringbuf_map_mmap_kern(struct bpf_map *map, struct vm_area_struct *vma)
{
struct bpf_ringbuf_map *rb_map;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
if (vma->vm_flags & VM_WRITE) {
/* allow writable mapping for the consumer_pos only */
if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
return -EPERM;
} else {
vm_flags_clear(vma, VM_MAYWRITE);
}
/* remap_vmalloc_range() checks size and offset constraints */
return remap_vmalloc_range(vma, rb_map->rb,
vma->vm_pgoff + RINGBUF_PGOFF);
}
static int ringbuf_map_mmap_user(struct bpf_map *map, struct vm_area_struct *vma)
{
struct bpf_ringbuf_map *rb_map;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
if (vma->vm_flags & VM_WRITE) {
if (vma->vm_pgoff == 0)
/* Disallow writable mappings to the consumer pointer,
* and allow writable mappings to both the producer
* position, and the ring buffer data itself.
*/
return -EPERM;
} else {
vm_flags_clear(vma, VM_MAYWRITE);
}
/* remap_vmalloc_range() checks size and offset constraints */
return remap_vmalloc_range(vma, rb_map->rb, vma->vm_pgoff + RINGBUF_PGOFF);
}
static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
{
unsigned long cons_pos, prod_pos;
cons_pos = smp_load_acquire(&rb->consumer_pos);
prod_pos = smp_load_acquire(&rb->producer_pos);
return prod_pos - cons_pos;
}
static u32 ringbuf_total_data_sz(const struct bpf_ringbuf *rb)
{
return rb->mask + 1;
}
static __poll_t ringbuf_map_poll_kern(struct bpf_map *map, struct file *filp,
struct poll_table_struct *pts)
{
struct bpf_ringbuf_map *rb_map;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
poll_wait(filp, &rb_map->rb->waitq, pts);
if (ringbuf_avail_data_sz(rb_map->rb))
return EPOLLIN | EPOLLRDNORM;
return 0;
}
static __poll_t ringbuf_map_poll_user(struct bpf_map *map, struct file *filp,
struct poll_table_struct *pts)
{
struct bpf_ringbuf_map *rb_map;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
poll_wait(filp, &rb_map->rb->waitq, pts);
if (ringbuf_avail_data_sz(rb_map->rb) < ringbuf_total_data_sz(rb_map->rb))
return EPOLLOUT | EPOLLWRNORM;
return 0;
}
static u64 ringbuf_map_mem_usage(const struct bpf_map *map)
{
struct bpf_ringbuf *rb;
int nr_data_pages;
int nr_meta_pages;
u64 usage = sizeof(struct bpf_ringbuf_map);
rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
usage += (u64)rb->nr_pages << PAGE_SHIFT;
nr_meta_pages = RINGBUF_NR_META_PAGES;
nr_data_pages = map->max_entries >> PAGE_SHIFT;
usage += (nr_meta_pages + 2 * nr_data_pages) * sizeof(struct page *);
return usage;
}
BTF_ID_LIST_SINGLE(ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
const struct bpf_map_ops ringbuf_map_ops = {
.map_meta_equal = bpf_map_meta_equal,
.map_alloc = ringbuf_map_alloc,
.map_free = ringbuf_map_free,
.map_mmap = ringbuf_map_mmap_kern,
.map_poll = ringbuf_map_poll_kern,
.map_lookup_elem = ringbuf_map_lookup_elem,
.map_update_elem = ringbuf_map_update_elem,
.map_delete_elem = ringbuf_map_delete_elem,
.map_get_next_key = ringbuf_map_get_next_key,
.map_mem_usage = ringbuf_map_mem_usage,
.map_btf_id = &ringbuf_map_btf_ids[0],
};
BTF_ID_LIST_SINGLE(user_ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
const struct bpf_map_ops user_ringbuf_map_ops = {
.map_meta_equal = bpf_map_meta_equal,
.map_alloc = ringbuf_map_alloc,
.map_free = ringbuf_map_free,
.map_mmap = ringbuf_map_mmap_user,
.map_poll = ringbuf_map_poll_user,
.map_lookup_elem = ringbuf_map_lookup_elem,
.map_update_elem = ringbuf_map_update_elem,
.map_delete_elem = ringbuf_map_delete_elem,
.map_get_next_key = ringbuf_map_get_next_key,
.map_mem_usage = ringbuf_map_mem_usage,
.map_btf_id = &user_ringbuf_map_btf_ids[0],
};
/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
* calculate offset from record metadata to ring buffer in pages, rounded
* down. This page offset is stored as part of record metadata and allows to
* restore struct bpf_ringbuf * from record pointer. This page offset is
* stored at offset 4 of record metadata header.
*/
static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
struct bpf_ringbuf_hdr *hdr)
{
return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
}
/* Given pointer to ring buffer record header, restore pointer to struct
* bpf_ringbuf itself by using page offset stored at offset 4
*/
static struct bpf_ringbuf *
bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
{
unsigned long addr = (unsigned long)(void *)hdr;
unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
return (void*)((addr & PAGE_MASK) - off);
}
static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
{
unsigned long cons_pos, prod_pos, new_prod_pos, pend_pos, flags;
struct bpf_ringbuf_hdr *hdr;
u32 len, pg_off, tmp_size, hdr_len;
if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
return NULL;
len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
if (len > ringbuf_total_data_sz(rb))
return NULL;
cons_pos = smp_load_acquire(&rb->consumer_pos);
if (in_nmi()) {
if (!spin_trylock_irqsave(&rb->spinlock, flags))
return NULL;
} else {
spin_lock_irqsave(&rb->spinlock, flags);
}
pend_pos = rb->pending_pos;
prod_pos = rb->producer_pos;
new_prod_pos = prod_pos + len;
while (pend_pos < prod_pos) {
hdr = (void *)rb->data + (pend_pos & rb->mask);
hdr_len = READ_ONCE(hdr->len);
if (hdr_len & BPF_RINGBUF_BUSY_BIT)
break;
tmp_size = hdr_len & ~BPF_RINGBUF_DISCARD_BIT;
tmp_size = round_up(tmp_size + BPF_RINGBUF_HDR_SZ, 8);
pend_pos += tmp_size;
}
rb->pending_pos = pend_pos;
/* check for out of ringbuf space:
* - by ensuring producer position doesn't advance more than
* (ringbuf_size - 1) ahead
* - by ensuring oldest not yet committed record until newest
* record does not span more than (ringbuf_size - 1)
*/
if (new_prod_pos - cons_pos > rb->mask ||
new_prod_pos - pend_pos > rb->mask) {
spin_unlock_irqrestore(&rb->spinlock, flags);
return NULL;
}
hdr = (void *)rb->data + (prod_pos & rb->mask);
pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
hdr->len = size | BPF_RINGBUF_BUSY_BIT;
hdr->pg_off = pg_off;
/* pairs with consumer's smp_load_acquire() */
smp_store_release(&rb->producer_pos, new_prod_pos);
spin_unlock_irqrestore(&rb->spinlock, flags);
return (void *)hdr + BPF_RINGBUF_HDR_SZ;
}
BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
{
struct bpf_ringbuf_map *rb_map;
if (unlikely(flags))
return 0;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
}
const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
.func = bpf_ringbuf_reserve,
.ret_type = RET_PTR_TO_RINGBUF_MEM_OR_NULL,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_CONST_ALLOC_SIZE_OR_ZERO,
.arg3_type = ARG_ANYTHING,
};
static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
{
unsigned long rec_pos, cons_pos;
struct bpf_ringbuf_hdr *hdr;
struct bpf_ringbuf *rb;
u32 new_len;
hdr = sample - BPF_RINGBUF_HDR_SZ;
rb = bpf_ringbuf_restore_from_rec(hdr);
new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
if (discard)
new_len |= BPF_RINGBUF_DISCARD_BIT;
/* update record header with correct final size prefix */
xchg(&hdr->len, new_len);
/* if consumer caught up and is waiting for our record, notify about
* new data availability
*/
rec_pos = (void *)hdr - (void *)rb->data;
cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
if (flags & BPF_RB_FORCE_WAKEUP)
irq_work_queue(&rb->work);
else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
irq_work_queue(&rb->work);
}
BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
{
bpf_ringbuf_commit(sample, flags, false /* discard */);
return 0;
}
const struct bpf_func_proto bpf_ringbuf_submit_proto = {
.func = bpf_ringbuf_submit,
.ret_type = RET_VOID,
.arg1_type = ARG_PTR_TO_RINGBUF_MEM | OBJ_RELEASE,
.arg2_type = ARG_ANYTHING,
};
BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
{
bpf_ringbuf_commit(sample, flags, true /* discard */);
return 0;
}
const struct bpf_func_proto bpf_ringbuf_discard_proto = {
.func = bpf_ringbuf_discard,
.ret_type = RET_VOID,
.arg1_type = ARG_PTR_TO_RINGBUF_MEM | OBJ_RELEASE,
.arg2_type = ARG_ANYTHING,
};
BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
u64, flags)
{
struct bpf_ringbuf_map *rb_map;
void *rec;
if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
return -EINVAL;
rb_map = container_of(map, struct bpf_ringbuf_map, map);
rec = __bpf_ringbuf_reserve(rb_map->rb, size);
if (!rec)
return -EAGAIN;
memcpy(rec, data, size);
bpf_ringbuf_commit(rec, flags, false /* discard */);
return 0;
}
const struct bpf_func_proto bpf_ringbuf_output_proto = {
.func = bpf_ringbuf_output,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_MEM | MEM_RDONLY,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.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 ringbuf_total_data_sz(rb);
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,
};
BPF_CALL_4(bpf_ringbuf_reserve_dynptr, struct bpf_map *, map, u32, size, u64, flags,
struct bpf_dynptr_kern *, ptr)
{
struct bpf_ringbuf_map *rb_map;
void *sample;
int err;
if (unlikely(flags)) {
bpf_dynptr_set_null(ptr);
return -EINVAL;
}
err = bpf_dynptr_check_size(size);
if (err) {
bpf_dynptr_set_null(ptr);
return err;
}
rb_map = container_of(map, struct bpf_ringbuf_map, map);
sample = __bpf_ringbuf_reserve(rb_map->rb, size);
if (!sample) {
bpf_dynptr_set_null(ptr);
return -EINVAL;
}
bpf_dynptr_init(ptr, sample, BPF_DYNPTR_TYPE_RINGBUF, 0, size);
return 0;
}
const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto = {
.func = bpf_ringbuf_reserve_dynptr,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_ANYTHING,
.arg3_type = ARG_ANYTHING,
.arg4_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | MEM_UNINIT,
};
BPF_CALL_2(bpf_ringbuf_submit_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
{
if (!ptr->data)
return 0;
bpf_ringbuf_commit(ptr->data, flags, false /* discard */);
bpf_dynptr_set_null(ptr);
return 0;
}
const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto = {
.func = bpf_ringbuf_submit_dynptr,
.ret_type = RET_VOID,
.arg1_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
.arg2_type = ARG_ANYTHING,
};
BPF_CALL_2(bpf_ringbuf_discard_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
{
if (!ptr->data)
return 0;
bpf_ringbuf_commit(ptr->data, flags, true /* discard */);
bpf_dynptr_set_null(ptr);
return 0;
}
const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = {
.func = bpf_ringbuf_discard_dynptr,
.ret_type = RET_VOID,
.arg1_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
.arg2_type = ARG_ANYTHING,
};
static int __bpf_user_ringbuf_peek(struct bpf_ringbuf *rb, void **sample, u32 *size)
{
int err;
u32 hdr_len, sample_len, total_len, flags, *hdr;
u64 cons_pos, prod_pos;
/* Synchronizes with smp_store_release() in user-space producer. */
prod_pos = smp_load_acquire(&rb->producer_pos);
if (prod_pos % 8)
return -EINVAL;
/* Synchronizes with smp_store_release() in __bpf_user_ringbuf_sample_release() */
cons_pos = smp_load_acquire(&rb->consumer_pos);
if (cons_pos >= prod_pos)
return -ENODATA;
hdr = (u32 *)((uintptr_t)rb->data + (uintptr_t)(cons_pos & rb->mask));
/* Synchronizes with smp_store_release() in user-space producer. */
hdr_len = smp_load_acquire(hdr);
flags = hdr_len & (BPF_RINGBUF_BUSY_BIT | BPF_RINGBUF_DISCARD_BIT);
sample_len = hdr_len & ~flags;
total_len = round_up(sample_len + BPF_RINGBUF_HDR_SZ, 8);
/* The sample must fit within the region advertised by the producer position. */
if (total_len > prod_pos - cons_pos)
return -EINVAL;
/* The sample must fit within the data region of the ring buffer. */
if (total_len > ringbuf_total_data_sz(rb))
return -E2BIG;
/* The sample must fit into a struct bpf_dynptr. */
err = bpf_dynptr_check_size(sample_len);
if (err)
return -E2BIG;
if (flags & BPF_RINGBUF_DISCARD_BIT) {
/* If the discard bit is set, the sample should be skipped.
*
* Update the consumer pos, and return -EAGAIN so the caller
* knows to skip this sample and try to read the next one.
*/
smp_store_release(&rb->consumer_pos, cons_pos + total_len);
return -EAGAIN;
}
if (flags & BPF_RINGBUF_BUSY_BIT)
return -ENODATA;
*sample = (void *)((uintptr_t)rb->data +
(uintptr_t)((cons_pos + BPF_RINGBUF_HDR_SZ) & rb->mask));
*size = sample_len;
return 0;
}
static void __bpf_user_ringbuf_sample_release(struct bpf_ringbuf *rb, size_t size, u64 flags)
{
u64 consumer_pos;
u32 rounded_size = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
/* Using smp_load_acquire() is unnecessary here, as the busy-bit
* prevents another task from writing to consumer_pos after it was read
* by this task with smp_load_acquire() in __bpf_user_ringbuf_peek().
*/
consumer_pos = rb->consumer_pos;
/* Synchronizes with smp_load_acquire() in user-space producer. */
smp_store_release(&rb->consumer_pos, consumer_pos + rounded_size);
}
BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map,
void *, callback_fn, void *, callback_ctx, u64, flags)
{
struct bpf_ringbuf *rb;
long samples, discarded_samples = 0, ret = 0;
bpf_callback_t callback = (bpf_callback_t)callback_fn;
u64 wakeup_flags = BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP;
int busy = 0;
if (unlikely(flags & ~wakeup_flags))
return -EINVAL;
rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
/* If another consumer is already consuming a sample, wait for them to finish. */
if (!atomic_try_cmpxchg(&rb->busy, &busy, 1))
return -EBUSY;
for (samples = 0; samples < BPF_MAX_USER_RINGBUF_SAMPLES && ret == 0; samples++) {
int err;
u32 size;
void *sample;
struct bpf_dynptr_kern dynptr;
err = __bpf_user_ringbuf_peek(rb, &sample, &size);
if (err) {
if (err == -ENODATA) {
break;
} else if (err == -EAGAIN) {
discarded_samples++;
continue;
} else {
ret = err;
goto schedule_work_return;
}
}
bpf_dynptr_init(&dynptr, sample, BPF_DYNPTR_TYPE_LOCAL, 0, size);
ret = callback((uintptr_t)&dynptr, (uintptr_t)callback_ctx, 0, 0, 0);
__bpf_user_ringbuf_sample_release(rb, size, flags);
}
ret = samples - discarded_samples;
schedule_work_return:
/* Prevent the clearing of the busy-bit from being reordered before the
* storing of any rb consumer or producer positions.
*/
atomic_set_release(&rb->busy, 0);
if (flags & BPF_RB_FORCE_WAKEUP)
irq_work_queue(&rb->work);
else if (!(flags & BPF_RB_NO_WAKEUP) && samples > 0)
irq_work_queue(&rb->work);
return ret;
}
const struct bpf_func_proto bpf_user_ringbuf_drain_proto = {
.func = bpf_user_ringbuf_drain,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
.arg2_type = ARG_PTR_TO_FUNC,
.arg3_type = ARG_PTR_TO_STACK_OR_NULL,
.arg4_type = ARG_ANYTHING,
};
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