bpf: Add BPF_PROG_BIND_MAP syscall

This syscall binds a map to a program. Returns success if the map is
already bound to the program.

Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: YiFei Zhu <zhuyifei1999@gmail.com>
Link: https://lore.kernel.org/bpf/20200915234543.3220146-3-sdf@google.com

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7dd3141..a228125 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -124,6 +124,7 @@ enum bpf_cmd {
        BPF_ENABLE_STATS,
        BPF_ITER_CREATE,
        BPF_LINK_DETACH,
+       BPF_PROG_BIND_MAP,
 };
 
 enum bpf_map_type {
@@ -658,6 +659,12 @@ union bpf_attr {
                __u32           flags;
        } iter_create;
 
+       struct { /* struct used by BPF_PROG_BIND_MAP command */
+               __u32           prog_fd;
+               __u32           map_fd;
+               __u32           flags;          /* extra flags */
+       } prog_bind_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 a67b8c6..2ce32ca 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4161,6 +4161,66 @@ static int bpf_iter_create(union bpf_attr *attr)
        return err;
 }
 
+#define BPF_PROG_BIND_MAP_LAST_FIELD prog_bind_map.flags
+
+static int bpf_prog_bind_map(union bpf_attr *attr)
+{
+       struct bpf_prog *prog;
+       struct bpf_map *map;
+       struct bpf_map **used_maps_old, **used_maps_new;
+       int i, ret = 0;
+
+       if (CHECK_ATTR(BPF_PROG_BIND_MAP))
+               return -EINVAL;
+
+       if (attr->prog_bind_map.flags)
+               return -EINVAL;
+
+       prog = bpf_prog_get(attr->prog_bind_map.prog_fd);
+       if (IS_ERR(prog))
+               return PTR_ERR(prog);
+
+       map = bpf_map_get(attr->prog_bind_map.map_fd);
+       if (IS_ERR(map)) {
+               ret = PTR_ERR(map);
+               goto out_prog_put;
+       }
+
+       mutex_lock(&prog->aux->used_maps_mutex);
+
+       used_maps_old = prog->aux->used_maps;
+
+       for (i = 0; i < prog->aux->used_map_cnt; i++)
+               if (used_maps_old[i] == map)
+                       goto out_unlock;
+
+       used_maps_new = kmalloc_array(prog->aux->used_map_cnt + 1,
+                                     sizeof(used_maps_new[0]),
+                                     GFP_KERNEL);
+       if (!used_maps_new) {
+               ret = -ENOMEM;
+               goto out_unlock;
+       }
+
+       memcpy(used_maps_new, used_maps_old,
+              sizeof(used_maps_old[0]) * prog->aux->used_map_cnt);
+       used_maps_new[prog->aux->used_map_cnt] = map;
+
+       prog->aux->used_map_cnt++;
+       prog->aux->used_maps = used_maps_new;
+
+       kfree(used_maps_old);
+
+out_unlock:
+       mutex_unlock(&prog->aux->used_maps_mutex);
+
+       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;
@@ -4294,6 +4354,9 @@ 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_BIND_MAP:
+               err = bpf_prog_bind_map(&attr);
+               break;
        default:
                err = -EINVAL;
                break;

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7dd3141..a228125 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -124,6 +124,7 @@ enum bpf_cmd {
        BPF_ENABLE_STATS,
        BPF_ITER_CREATE,
        BPF_LINK_DETACH,
+       BPF_PROG_BIND_MAP,
 };
 
 enum bpf_map_type {
@@ -658,6 +659,12 @@ union bpf_attr {
                __u32           flags;
        } iter_create;
 
+       struct { /* struct used by BPF_PROG_BIND_MAP command */
+               __u32           prog_fd;
+               __u32           map_fd;
+               __u32           flags;          /* extra flags */
+       } prog_bind_map;
+
 } __attribute__((aligned(8)));
 
 /* The description below is an attempt at providing documentation to eBPF