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https://github.com/Fishwaldo/linux-bl808.git
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bpf: add queue and stack maps
Queue/stack maps implement a FIFO/LIFO data storage for ebpf programs. These maps support peek, pop and push operations that are exposed to eBPF programs through the new bpf_map[peek/pop/push] helpers. Those operations are exposed to userspace applications through the already existing syscalls in the following way: BPF_MAP_LOOKUP_ELEM -> peek BPF_MAP_LOOKUP_AND_DELETE_ELEM -> pop BPF_MAP_UPDATE_ELEM -> push Queue/stack maps are implemented using a buffer, tail and head indexes, hence BPF_F_NO_PREALLOC is not supported. As opposite to other maps, queue and stack do not use RCU for protecting maps values, the bpf_map[peek/pop] have a ARG_PTR_TO_UNINIT_MAP_VALUE argument that is a pointer to a memory zone where to save the value of a map. Basically the same as ARG_PTR_TO_UNINIT_MEM, but the size has not be passed as an extra argument. Our main motivation for implementing queue/stack maps was to keep track of a pool of elements, like network ports in a SNAT, however we forsee other use cases, like for exampling saving last N kernel events in a map and then analysing from userspace. Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Mauricio Vasquez B
Alexei Starovoitov
parent
2ea864c58f
commit
f1a2e44a3a
10 changed files with 401 additions and 3 deletions
288
kernel/bpf/queue_stack_maps.c
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288
kernel/bpf/queue_stack_maps.c
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@ -0,0 +1,288 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* queue_stack_maps.c: BPF queue and stack maps
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*
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* Copyright (c) 2018 Politecnico di Torino
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*/
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#include <linux/bpf.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include "percpu_freelist.h"
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#define QUEUE_STACK_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
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struct bpf_queue_stack {
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struct bpf_map map;
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raw_spinlock_t lock;
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u32 head, tail;
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u32 size; /* max_entries + 1 */
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char elements[0] __aligned(8);
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};
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static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
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{
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return container_of(map, struct bpf_queue_stack, map);
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}
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static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
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{
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return qs->head == qs->tail;
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}
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static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
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{
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u32 head = qs->head + 1;
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if (unlikely(head >= qs->size))
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head = 0;
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return head == qs->tail;
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}
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/* Called from syscall */
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static int queue_stack_map_alloc_check(union bpf_attr *attr)
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{
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/* check sanity of attributes */
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if (attr->max_entries == 0 || attr->key_size != 0 ||
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attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
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return -EINVAL;
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if (attr->value_size > KMALLOC_MAX_SIZE)
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/* if value_size is bigger, the user space won't be able to
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* access the elements.
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*/
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return -E2BIG;
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return 0;
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}
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static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
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{
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int ret, numa_node = bpf_map_attr_numa_node(attr);
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struct bpf_queue_stack *qs;
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u32 size, value_size;
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u64 queue_size, cost;
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size = attr->max_entries + 1;
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value_size = attr->value_size;
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queue_size = sizeof(*qs) + (u64) value_size * size;
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cost = queue_size;
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if (cost >= U32_MAX - PAGE_SIZE)
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return ERR_PTR(-E2BIG);
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cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
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ret = bpf_map_precharge_memlock(cost);
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if (ret < 0)
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return ERR_PTR(ret);
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qs = bpf_map_area_alloc(queue_size, numa_node);
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if (!qs)
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return ERR_PTR(-ENOMEM);
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memset(qs, 0, sizeof(*qs));
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bpf_map_init_from_attr(&qs->map, attr);
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qs->map.pages = cost;
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qs->size = size;
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raw_spin_lock_init(&qs->lock);
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return &qs->map;
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}
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/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
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static void queue_stack_map_free(struct bpf_map *map)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
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* so the programs (can be more than one that used this map) were
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* disconnected from events. Wait for outstanding critical sections in
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* these programs to complete
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*/
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synchronize_rcu();
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bpf_map_area_free(qs);
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}
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static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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unsigned long flags;
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int err = 0;
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void *ptr;
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raw_spin_lock_irqsave(&qs->lock, flags);
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if (queue_stack_map_is_empty(qs)) {
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err = -ENOENT;
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goto out;
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}
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ptr = &qs->elements[qs->tail * qs->map.value_size];
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memcpy(value, ptr, qs->map.value_size);
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if (delete) {
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if (unlikely(++qs->tail >= qs->size))
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qs->tail = 0;
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}
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out:
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raw_spin_unlock_irqrestore(&qs->lock, flags);
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return err;
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}
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static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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unsigned long flags;
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int err = 0;
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void *ptr;
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u32 index;
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raw_spin_lock_irqsave(&qs->lock, flags);
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if (queue_stack_map_is_empty(qs)) {
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err = -ENOENT;
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goto out;
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}
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index = qs->head - 1;
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if (unlikely(index >= qs->size))
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index = qs->size - 1;
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ptr = &qs->elements[index * qs->map.value_size];
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memcpy(value, ptr, qs->map.value_size);
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if (delete)
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qs->head = index;
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out:
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raw_spin_unlock_irqrestore(&qs->lock, flags);
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return err;
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}
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/* Called from syscall or from eBPF program */
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static int queue_map_peek_elem(struct bpf_map *map, void *value)
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{
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return __queue_map_get(map, value, false);
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}
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/* Called from syscall or from eBPF program */
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static int stack_map_peek_elem(struct bpf_map *map, void *value)
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{
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return __stack_map_get(map, value, false);
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}
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/* Called from syscall or from eBPF program */
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static int queue_map_pop_elem(struct bpf_map *map, void *value)
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{
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return __queue_map_get(map, value, true);
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}
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/* Called from syscall or from eBPF program */
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static int stack_map_pop_elem(struct bpf_map *map, void *value)
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{
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return __stack_map_get(map, value, true);
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}
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/* Called from syscall or from eBPF program */
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static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
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u64 flags)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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unsigned long irq_flags;
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int err = 0;
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void *dst;
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/* BPF_EXIST is used to force making room for a new element in case the
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* map is full
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*/
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bool replace = (flags & BPF_EXIST);
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/* Check supported flags for queue and stack maps */
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if (flags & BPF_NOEXIST || flags > BPF_EXIST)
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return -EINVAL;
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raw_spin_lock_irqsave(&qs->lock, irq_flags);
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if (queue_stack_map_is_full(qs)) {
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if (!replace) {
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err = -E2BIG;
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goto out;
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}
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/* advance tail pointer to overwrite oldest element */
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if (unlikely(++qs->tail >= qs->size))
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qs->tail = 0;
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}
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dst = &qs->elements[qs->head * qs->map.value_size];
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memcpy(dst, value, qs->map.value_size);
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if (unlikely(++qs->head >= qs->size))
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qs->head = 0;
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out:
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raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
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return err;
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}
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/* Called from syscall or from eBPF program */
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static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
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{
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return NULL;
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}
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/* Called from syscall or from eBPF program */
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static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
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void *value, u64 flags)
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{
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return -EINVAL;
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}
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/* Called from syscall or from eBPF program */
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static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
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{
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return -EINVAL;
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}
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/* Called from syscall */
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static int queue_stack_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 -EINVAL;
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}
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const struct bpf_map_ops queue_map_ops = {
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.map_alloc_check = queue_stack_map_alloc_check,
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.map_alloc = queue_stack_map_alloc,
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.map_free = queue_stack_map_free,
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.map_lookup_elem = queue_stack_map_lookup_elem,
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.map_update_elem = queue_stack_map_update_elem,
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.map_delete_elem = queue_stack_map_delete_elem,
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.map_push_elem = queue_stack_map_push_elem,
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.map_pop_elem = queue_map_pop_elem,
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.map_peek_elem = queue_map_peek_elem,
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.map_get_next_key = queue_stack_map_get_next_key,
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};
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const struct bpf_map_ops stack_map_ops = {
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.map_alloc_check = queue_stack_map_alloc_check,
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.map_alloc = queue_stack_map_alloc,
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.map_free = queue_stack_map_free,
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.map_lookup_elem = queue_stack_map_lookup_elem,
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.map_update_elem = queue_stack_map_update_elem,
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.map_delete_elem = queue_stack_map_delete_elem,
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.map_push_elem = queue_stack_map_push_elem,
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.map_pop_elem = stack_map_pop_elem,
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.map_peek_elem = stack_map_peek_elem,
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.map_get_next_key = queue_stack_map_get_next_key,
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};
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