This introduces a new command to retrieve a variable number of entries
from a bpf map wrapping the existing bpf methods:
map_get_next_key and map_lookup_elem
Note that map_dump doesn't guarantee that reading the entire table is
consistent since this function is always racing with kernel and user code
but the same behaviour is found when the entire table is walked using
the current interfaces: map_get_next_key + map_lookup_elem.
It is also important to note that when a locked map is provided it is
consistent only for 1 entry at the time, meaning that the buf returned
might or might not be consistent.
Suggested-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
Signed-off-by: Brian Vazquez <brianvv@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 9 ++++
kernel/bpf/syscall.c | 108 +++++++++++++++++++++++++++++++++++++++
2 files changed, 117 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b077507efa3f3..1d753958874df 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -106,6 +106,7 @@ enum bpf_cmd {
BPF_TASK_FD_QUERY,
BPF_MAP_LOOKUP_AND_DELETE_ELEM,
BPF_MAP_FREEZE,
+ BPF_MAP_DUMP,
};
enum bpf_map_type {
@@ -385,6 +386,14 @@ union bpf_attr {
__u64 flags;
};
+ struct { /* struct used by BPF_MAP_DUMP command */
+ __u32 map_fd;
+ __aligned_u64 prev_key;
+ __aligned_u64 buf;
+ __aligned_u64 buf_len; /* input/output: len of buf */
+ __u64 flags;
+ } dump;
+
struct { /* anonymous struct used by BPF_PROG_LOAD command */
__u32 prog_type; /* one of enum bpf_prog_type */
__u32 insn_cnt;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a1823a50f9be0..7653346b5cfd1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1097,6 +1097,111 @@ static int map_get_next_key(union bpf_attr *attr)
return err;
}
+/* last field in 'union bpf_attr' used by this command */
+#define BPF_MAP_DUMP_LAST_FIELD dump.buf_len
+
+static int map_dump(union bpf_attr *attr)
+{
+ void __user *ukey = u64_to_user_ptr(attr->dump.prev_key);
+ void __user *ubuf = u64_to_user_ptr(attr->dump.buf);
+ u32 __user *ubuf_len = u64_to_user_ptr(attr->dump.buf_len);
+ int ufd = attr->dump.map_fd;
+ struct bpf_map *map;
+ void *buf, *prev_key, *key, *value;
+ u32 value_size, elem_size, buf_len, cp_len;
+ struct fd f;
+ int err;
+
+ if (CHECK_ATTR(BPF_MAP_DUMP))
+ return -EINVAL;
+
+ attr->flags = 0;
+ if (attr->dump.flags & ~BPF_F_LOCK)
+ return -EINVAL;
+
+ f = fdget(ufd);
+ map = __bpf_map_get(f);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
+ if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
+ if ((attr->dump.flags & BPF_F_LOCK) &&
+ !map_value_has_spin_lock(map)) {
+ err = -EINVAL;
+ goto err_put;
+ }
+
+ if (map->map_type == BPF_MAP_TYPE_QUEUE ||
+ map->map_type == BPF_MAP_TYPE_STACK) {
+ err = -ENOTSUPP;
+ goto err_put;
+ }
+
+ value_size = bpf_map_value_size(map);
+
+ err = get_user(buf_len, ubuf_len);
+ if (err)
+ goto err_put;
+
+ elem_size = map->key_size + value_size;
+ if (buf_len < elem_size) {
+ err = -EINVAL;
+ goto err_put;
+ }
+
+ if (ukey) {
+ prev_key = __bpf_copy_key(ukey, map->key_size);
+ if (IS_ERR(prev_key)) {
+ err = PTR_ERR(prev_key);
+ goto err_put;
+ }
+ } else {
+ prev_key = NULL;
+ }
+
+ err = -ENOMEM;
+ buf = kmalloc(elem_size, GFP_USER | __GFP_NOWARN);
+ if (!buf)
+ goto err_put;
+
+ key = buf;
+ value = key + map->key_size;
+ for (cp_len = 0; cp_len + elem_size <= buf_len ; cp_len += elem_size) {
+next:
+ if (signal_pending(current)) {
+ err = -EINTR;
+ break;
+ }
+
+ rcu_read_lock();
+ err = map->ops->map_get_next_key(map, prev_key, key);
+ rcu_read_unlock();
+
+ if (err)
+ break;
+
+ if (bpf_map_copy_value(map, key, value, attr->dump.flags))
+ goto next;
+
+ if (copy_to_user(ubuf + cp_len, buf, elem_size))
+ break;
+
+ prev_key = key;
+ }
+
+ if (cp_len)
+ err = 0;
+ if (copy_to_user(ubuf_len, &cp_len, sizeof(cp_len)))
+ err = -EFAULT;
+ kfree(buf);
+err_put:
+ fdput(f);
+ return err;
+}
+
#define BPF_MAP_LOOKUP_AND_DELETE_ELEM_LAST_FIELD value
static int map_lookup_and_delete_elem(union bpf_attr *attr)
@@ -2891,6 +2996,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_MAP_LOOKUP_AND_DELETE_ELEM:
err = map_lookup_and_delete_elem(&attr);
break;
+ case BPF_MAP_DUMP:
+ err = map_dump(&attr);
+ break;
default:
err = -EINVAL;
break;
--
2.22.0.410.gd8fdbe21b5-goog
