bpf: Add file mode configuration into bpf maps

Introduce the map read/write flags to the eBPF syscalls that returns the
map fd. The flags is used to set up the file mode when construct a new
file descriptor for bpf maps. To not break the backward capability, the
f_flags is set to O_RDWR if the flag passed by syscall is 0. Otherwise
it should be O_RDONLY or O_WRONLY. When the userspace want to modify or
read the map content, it will check the file mode to see if it is
allowed to make the change.

Signed-off-by: Chenbo Feng <fengc@google.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4303fb6c3817..d83f95ea6a1b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -218,6 +218,10 @@ enum bpf_attach_type {
 
 #define BPF_OBJ_NAME_LEN 16U
 
+/* Flags for accessing BPF object */
+#define BPF_F_RDONLY            (1U << 3)
+#define BPF_F_WRONLY            (1U << 4)
+
 union bpf_attr {
         struct { /* anonymous struct used by BPF_MAP_CREATE command */
                 __u32   map_type;       /* one of enum bpf_map_type */
@@ -260,6 +264,7 @@ union bpf_attr {
         struct { /* anonymous struct used by BPF_OBJ_* commands */
                 __aligned_u64   pathname;
                 __u32           bpf_fd;
+                __u32           file_flags;
         };
 
         struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */
@@ -287,6 +292,7 @@ union bpf_attr {
                         __u32           map_id;
                 };
                 __u32           next_id;
+                __u32           open_flags;
         };
 
         struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */