queue_stack_maps.c
// SPDX-License-Identifier: GPL-2.0
/*
* queue_stack_maps.c: BPF queue and stack maps
*
* Copyright (c) 2018 Politecnico di Torino
*/
#include <linux/bpf.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/capability.h>
#include "percpu_freelist.h"
#define QUEUE_STACK_CREATE_FLAG_MASK \
(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
struct bpf_queue_stack {
struct bpf_map map;
raw_spinlock_t lock;
u32 head, tail;
u32 size; /* max_entries + 1 */
char elements[0] __aligned(8);
};
static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
{
return container_of(map, struct bpf_queue_stack, map);
}
static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
{
return qs->head == qs->tail;
}
static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
{
u32 head = qs->head + 1;
if (unlikely(head >= qs->size))
head = 0;
return head == qs->tail;
}
/* Called from syscall */
static int queue_stack_map_alloc_check(union bpf_attr *attr)
{
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 0 ||
attr->value_size == 0 ||
attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
return -EINVAL;
if (attr->value_size > KMALLOC_MAX_SIZE)
/* if value_size is bigger, the user space won't be able to
* access the elements.
*/
return -E2BIG;
return 0;
}
static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
{
int ret, numa_node = bpf_map_attr_numa_node(attr);
struct bpf_queue_stack *qs;
u64 size, queue_size, cost;
size = (u64) attr->max_entries + 1;
cost = queue_size = sizeof(*qs) + size * attr->value_size;
if (cost >= U32_MAX - PAGE_SIZE)
return ERR_PTR(-E2BIG);
cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
ret = bpf_map_precharge_memlock(cost);
if (ret < 0)
return ERR_PTR(ret);
qs = bpf_map_area_alloc(queue_size, numa_node);
if (!qs)
return ERR_PTR(-ENOMEM);
memset(qs, 0, sizeof(*qs));
bpf_map_init_from_attr(&qs->map, attr);
qs->map.pages = cost;
qs->size = size;
raw_spin_lock_init(&qs->lock);
return &qs->map;
}
/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
static void queue_stack_map_free(struct bpf_map *map)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
* so the programs (can be more than one that used this map) were
* disconnected from events. Wait for outstanding critical sections in
* these programs to complete
*/
synchronize_rcu();
bpf_map_area_free(qs);
}
static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
unsigned long flags;
int err = 0;
void *ptr;
raw_spin_lock_irqsave(&qs->lock, flags);
if (queue_stack_map_is_empty(qs)) {
memset(value, 0, qs->map.value_size);
err = -ENOENT;
goto out;
}
ptr = &qs->elements[qs->tail * qs->map.value_size];
memcpy(value, ptr, qs->map.value_size);
if (delete) {
if (unlikely(++qs->tail >= qs->size))
qs->tail = 0;
}
out:
raw_spin_unlock_irqrestore(&qs->lock, flags);
return err;
}
static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
unsigned long flags;
int err = 0;
void *ptr;
u32 index;
raw_spin_lock_irqsave(&qs->lock, flags);
if (queue_stack_map_is_empty(qs)) {
memset(value, 0, qs->map.value_size);
err = -ENOENT;
goto out;
}
index = qs->head - 1;
if (unlikely(index >= qs->size))
index = qs->size - 1;
ptr = &qs->elements[index * qs->map.value_size];
memcpy(value, ptr, qs->map.value_size);
if (delete)
qs->head = index;
out:
raw_spin_unlock_irqrestore(&qs->lock, flags);
return err;
}
/* Called from syscall or from eBPF program */
static int queue_map_peek_elem(struct bpf_map *map, void *value)
{
return __queue_map_get(map, value, false);
}
/* Called from syscall or from eBPF program */
static int stack_map_peek_elem(struct bpf_map *map, void *value)
{
return __stack_map_get(map, value, false);
}
/* Called from syscall or from eBPF program */
static int queue_map_pop_elem(struct bpf_map *map, void *value)
{
return __queue_map_get(map, value, true);
}
/* Called from syscall or from eBPF program */
static int stack_map_pop_elem(struct bpf_map *map, void *value)
{
return __stack_map_get(map, value, true);
}
/* Called from syscall or from eBPF program */
static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
u64 flags)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
unsigned long irq_flags;
int err = 0;
void *dst;
/* BPF_EXIST is used to force making room for a new element in case the
* map is full
*/
bool replace = (flags & BPF_EXIST);
/* Check supported flags for queue and stack maps */
if (flags & BPF_NOEXIST || flags > BPF_EXIST)
return -EINVAL;
raw_spin_lock_irqsave(&qs->lock, irq_flags);
if (queue_stack_map_is_full(qs)) {
if (!replace) {
err = -E2BIG;
goto out;
}
/* advance tail pointer to overwrite oldest element */
if (unlikely(++qs->tail >= qs->size))
qs->tail = 0;
}
dst = &qs->elements[qs->head * qs->map.value_size];
memcpy(dst, value, qs->map.value_size);
if (unlikely(++qs->head >= qs->size))
qs->head = 0;
out:
raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
return err;
}
/* Called from syscall or from eBPF program */
static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
{
return NULL;
}
/* Called from syscall or from eBPF program */
static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 flags)
{
return -EINVAL;
}
/* Called from syscall or from eBPF program */
static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
{
return -EINVAL;
}
/* Called from syscall */
static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
void *next_key)
{
return -EINVAL;
}
const struct bpf_map_ops queue_map_ops = {
.map_alloc_check = queue_stack_map_alloc_check,
.map_alloc = queue_stack_map_alloc,
.map_free = queue_stack_map_free,
.map_lookup_elem = queue_stack_map_lookup_elem,
.map_update_elem = queue_stack_map_update_elem,
.map_delete_elem = queue_stack_map_delete_elem,
.map_push_elem = queue_stack_map_push_elem,
.map_pop_elem = queue_map_pop_elem,
.map_peek_elem = queue_map_peek_elem,
.map_get_next_key = queue_stack_map_get_next_key,
};
const struct bpf_map_ops stack_map_ops = {
.map_alloc_check = queue_stack_map_alloc_check,
.map_alloc = queue_stack_map_alloc,
.map_free = queue_stack_map_free,
.map_lookup_elem = queue_stack_map_lookup_elem,
.map_update_elem = queue_stack_map_update_elem,
.map_delete_elem = queue_stack_map_delete_elem,
.map_push_elem = queue_stack_map_push_elem,
.map_pop_elem = stack_map_pop_elem,
.map_peek_elem = stack_map_peek_elem,
.map_get_next_key = queue_stack_map_get_next_key,
};