Commit 14dc6f04 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller

bpf: Add syscall lookup support for fd array and htab

This patch allows userspace to do BPF_MAP_LOOKUP_ELEM on
BPF_MAP_TYPE_PROG_ARRAY,
BPF_MAP_TYPE_ARRAY_OF_MAPS and
BPF_MAP_TYPE_HASH_OF_MAPS.

The lookup returns a prog-id or map-id to the userspace.
The userspace can then use the BPF_PROG_GET_FD_BY_ID
or BPF_MAP_GET_FD_BY_ID to get a fd.
Signed-off-by: 's avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: 's avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
parent 77b0d361
......@@ -36,6 +36,7 @@ struct bpf_map_ops {
int fd);
void (*map_fd_put_ptr)(void *ptr);
u32 (*map_gen_lookup)(struct bpf_map *map, struct bpf_insn *insn_buf);
u32 (*map_fd_sys_lookup_elem)(void *ptr);
};
struct bpf_map {
......@@ -288,9 +289,11 @@ int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value);
int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
void *key, void *value, u64 map_flags);
int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
void bpf_fd_array_map_clear(struct bpf_map *map);
int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
void *key, void *value, u64 map_flags);
int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
/* memcpy that is used with 8-byte aligned pointers, power-of-8 size and
* forced to use 'long' read/writes to try to atomically copy long counters.
......
......@@ -334,6 +334,26 @@ static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
return NULL;
}
/* only called from syscall */
int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)
{
void **elem, *ptr;
int ret = 0;
if (!map->ops->map_fd_sys_lookup_elem)
return -ENOTSUPP;
rcu_read_lock();
elem = array_map_lookup_elem(map, key);
if (elem && (ptr = READ_ONCE(*elem)))
*value = map->ops->map_fd_sys_lookup_elem(ptr);
else
ret = -ENOENT;
rcu_read_unlock();
return ret;
}
/* only called from syscall */
int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,
void *key, void *value, u64 map_flags)
......@@ -400,6 +420,11 @@ static void prog_fd_array_put_ptr(void *ptr)
bpf_prog_put(ptr);
}
static u32 prog_fd_array_sys_lookup_elem(void *ptr)
{
return ((struct bpf_prog *)ptr)->aux->id;
}
/* decrement refcnt of all bpf_progs that are stored in this map */
void bpf_fd_array_map_clear(struct bpf_map *map)
{
......@@ -418,6 +443,7 @@ const struct bpf_map_ops prog_array_map_ops = {
.map_delete_elem = fd_array_map_delete_elem,
.map_fd_get_ptr = prog_fd_array_get_ptr,
.map_fd_put_ptr = prog_fd_array_put_ptr,
.map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
};
static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
......@@ -585,4 +611,5 @@ const struct bpf_map_ops array_of_maps_map_ops = {
.map_delete_elem = fd_array_map_delete_elem,
.map_fd_get_ptr = bpf_map_fd_get_ptr,
.map_fd_put_ptr = bpf_map_fd_put_ptr,
.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
};
......@@ -1243,6 +1243,26 @@ static void fd_htab_map_free(struct bpf_map *map)
htab_map_free(map);
}
/* only called from syscall */
int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)
{
void **ptr;
int ret = 0;
if (!map->ops->map_fd_sys_lookup_elem)
return -ENOTSUPP;
rcu_read_lock();
ptr = htab_map_lookup_elem(map, key);
if (ptr)
*value = map->ops->map_fd_sys_lookup_elem(READ_ONCE(*ptr));
else
ret = -ENOENT;
rcu_read_unlock();
return ret;
}
/* only called from syscall */
int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
void *key, void *value, u64 map_flags)
......@@ -1305,4 +1325,5 @@ const struct bpf_map_ops htab_of_maps_map_ops = {
.map_delete_elem = htab_map_delete_elem,
.map_fd_get_ptr = bpf_map_fd_get_ptr,
.map_fd_put_ptr = bpf_map_fd_put_ptr,
.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
};
......@@ -95,3 +95,8 @@ void bpf_map_fd_put_ptr(void *ptr)
*/
bpf_map_put(ptr);
}
u32 bpf_map_fd_sys_lookup_elem(void *ptr)
{
return ((struct bpf_map *)ptr)->id;
}
......@@ -19,5 +19,6 @@ bool bpf_map_meta_equal(const struct bpf_map *meta0,
void *bpf_map_fd_get_ptr(struct bpf_map *map, struct file *map_file,
int ufd);
void bpf_map_fd_put_ptr(void *ptr);
u32 bpf_map_fd_sys_lookup_elem(void *ptr);
#endif
......@@ -24,6 +24,13 @@
#include <linux/kernel.h>
#include <linux/idr.h>
#define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PROG_ARRAY || \
(map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \
(map)->map_type == BPF_MAP_TYPE_CGROUP_ARRAY || \
(map)->map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS)
#define IS_FD_HASH(map) ((map)->map_type == BPF_MAP_TYPE_HASH_OF_MAPS)
#define IS_FD_MAP(map) (IS_FD_ARRAY(map) || IS_FD_HASH(map))
DEFINE_PER_CPU(int, bpf_prog_active);
static DEFINE_IDR(prog_idr);
static DEFINE_SPINLOCK(prog_idr_lock);
......@@ -411,6 +418,8 @@ static int map_lookup_elem(union bpf_attr *attr)
map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH ||
map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
value_size = round_up(map->value_size, 8) * num_possible_cpus();
else if (IS_FD_MAP(map))
value_size = sizeof(u32);
else
value_size = map->value_size;
......@@ -426,9 +435,10 @@ static int map_lookup_elem(union bpf_attr *attr)
err = bpf_percpu_array_copy(map, key, value);
} else if (map->map_type == BPF_MAP_TYPE_STACK_TRACE) {
err = bpf_stackmap_copy(map, key, value);
} else if (map->map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
err = -ENOTSUPP;
} else if (IS_FD_ARRAY(map)) {
err = bpf_fd_array_map_lookup_elem(map, key, value);
} else if (IS_FD_HASH(map)) {
err = bpf_fd_htab_map_lookup_elem(map, key, value);
} else {
rcu_read_lock();
ptr = map->ops->map_lookup_elem(map, key);
......
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