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Date: Tue, 27 Jun 2017 23:08:34 -0700
From: Martin KaFai Lau <kafai@...com>
To: <netdev@...r.kernel.org>
CC: Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...com>, <kernel-team@...com>
Subject: [PATCH net-next 1/2] 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: Martin KaFai Lau <kafai@...com>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
include/linux/bpf.h | 3 +++
kernel/bpf/arraymap.c | 27 +++++++++++++++++++++++++++
kernel/bpf/hashtab.c | 21 +++++++++++++++++++++
kernel/bpf/map_in_map.c | 5 +++++
kernel/bpf/map_in_map.h | 1 +
kernel/bpf/syscall.c | 16 +++++++++++++---
6 files changed, 70 insertions(+), 3 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index deca4e7f2845..5175729270d7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -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.
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index ecb43542246e..d771a3872500 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -335,6 +335,26 @@ static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
}
/* 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,
};
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 004334ea13ba..4fb463172aa8 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1244,6 +1244,26 @@ static void fd_htab_map_free(struct bpf_map *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,
};
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 59bcdf821ae4..1da574612bea 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -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;
+}
diff --git a/kernel/bpf/map_in_map.h b/kernel/bpf/map_in_map.h
index 177fadb689dc..6183db9ec08c 100644
--- a/kernel/bpf/map_in_map.h
+++ b/kernel/bpf/map_in_map.h
@@ -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
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8942c820d620..4409ccca8831 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -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);
--
2.9.3
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