From: YiFei Zhu <zhuyifei@xxxxxxxxxx>
This syscall attaches a map to a program. -EEXIST if the map is
already attached to the program. call_rcu is used to free the
old used_maps struct after an RCU grace period.
Signed-off-by: YiFei Zhu <zhuyifei@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 7 +++
kernel/bpf/syscall.c | 83 ++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 7 +++
3 files changed, 97 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b134e679e9db..01b32036a0f5 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -118,6 +118,7 @@ enum bpf_cmd {
BPF_ENABLE_STATS,
BPF_ITER_CREATE,
BPF_LINK_DETACH,
+ BPF_PROG_ADD_MAP,
};
enum bpf_map_type {
@@ -648,6 +649,12 @@ union bpf_attr {
__u32 flags;
} iter_create;
+ struct { /* struct used by BPF_PROG_ADD_MAP command */
+ __u32 prog_fd;
+ __u32 map_fd;
+ __u32 flags; /* extra flags */
+ } prog_add_map;
+
} __attribute__((aligned(8)));
/* The description below is an attempt at providing documentation to eBPF
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3fde9dc4b595..0564a4291184 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4144,6 +4144,86 @@ static int bpf_iter_create(union bpf_attr *attr)
return err;
}
+#define BPF_PROG_ADD_MAP_LAST_FIELD prog_add_map.flags
+
+static void __bpf_free_used_maps_rcu(struct rcu_head *rcu)
+{
+ struct bpf_used_maps *used_maps = container_of(rcu, struct bpf_used_maps, rcu);
+
+ kfree(used_maps->arr);
+ kfree(used_maps);
+}
+
+static int bpf_prog_add_map(union bpf_attr *attr)
+{
+ struct bpf_prog *prog;
+ struct bpf_map *map;
+ struct bpf_used_maps *used_maps_old, *used_maps_new;
+ int i, ret = 0;
+
+ if (CHECK_ATTR(BPF_PROG_ADD_MAP))
+ return -EINVAL;
+
+ if (attr->prog_add_map.flags)
+ return -EINVAL;
+
+ prog = bpf_prog_get(attr->prog_add_map.prog_fd);
+ if (IS_ERR(prog))
+ return PTR_ERR(prog);
+
+ map = bpf_map_get(attr->prog_add_map.map_fd);
+ if (IS_ERR(map)) {
+ ret = PTR_ERR(map);
+ goto out_prog_put;
+ }
+
+ used_maps_new = kzalloc(sizeof(*used_maps_new), GFP_KERNEL);
+ if (!used_maps_new) {
+ ret = -ENOMEM;
+ goto out_map_put;
+ }
+
+ mutex_lock(&prog->aux->used_maps_mutex);
+
+ used_maps_old = rcu_dereference_protected(prog->aux->used_maps,
+ lockdep_is_held(&prog->aux->used_maps_mutex));
+
+ for (i = 0; i < used_maps_old->cnt; i++)
+ if (used_maps_old->arr[i] == map) {
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ used_maps_new->cnt = used_maps_old->cnt + 1;
+ used_maps_new->arr = kmalloc_array(used_maps_new->cnt,
+ sizeof(used_maps_new->arr[0]),
+ GFP_KERNEL);
+ if (!used_maps_new->arr) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ memcpy(used_maps_new->arr, used_maps_old->arr,
+ sizeof(used_maps_old->arr[0]) * used_maps_old->cnt);
+ used_maps_new->arr[used_maps_old->cnt] = map;
+
+ rcu_assign_pointer(prog->aux->used_maps, used_maps_new);
+ call_rcu(&used_maps_old->rcu, __bpf_free_used_maps_rcu);
+
+out_unlock:
+ mutex_unlock(&prog->aux->used_maps_mutex);
+
+ if (ret)
+ kfree(used_maps_new);
+
+out_map_put:
+ if (ret)
+ bpf_map_put(map);
+out_prog_put:
+ bpf_prog_put(prog);
+ return ret;
+}
+
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
union bpf_attr attr;
@@ -4277,6 +4357,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_LINK_DETACH:
err = link_detach(&attr);
break;
+ case BPF_PROG_ADD_MAP:
+ err = bpf_prog_add_map(&attr);
+ break;
default:
err = -EINVAL;
break;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index b134e679e9db..01b32036a0f5 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -118,6 +118,7 @@ enum bpf_cmd {
BPF_ENABLE_STATS,
BPF_ITER_CREATE,
BPF_LINK_DETACH,
+ BPF_PROG_ADD_MAP,
};
enum bpf_map_type {
@@ -648,6 +649,12 @@ union bpf_attr {
__u32 flags;
} iter_create;
+ struct { /* struct used by BPF_PROG_ADD_MAP command */
+ __u32 prog_fd;
+ __u32 map_fd;
+ __u32 flags; /* extra flags */
+ } prog_add_map;
+
} __attribute__((aligned(8)));
/* The description below is an attempt at providing documentation to eBPF
--
2.28.0
