xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

bpf: btf: Introduce BTF ID

Browse Source 
This patch gives an ID to each loaded BTF.  The ID is allocated by
the idr like the existing prog-id and map-id.

The bpf_put(map->btf) is moved to __bpf_map_put() so that the
userspace can stop seeing the BTF ID ASAP when the last BTF
refcnt is gone.

It also makes BTF accessible from userspace through the
1. new BPF_BTF_GET_FD_BY_ID command.  It is limited to CAP_SYS_ADMIN
   which is inline with the BPF_BTF_LOAD cmd and the existing
   BPF_[MAP|PROG]_GET_FD_BY_ID cmd.
2. new btf_id (and btf_key_id + btf_value_id) in "struct bpf_map_info"

Once the BTF ID handler is accessible from userspace, freeing a BTF
object has to go through a rcu period.  The BPF_BTF_GET_FD_BY_ID cmd
can then be done under a rcu_read_lock() instead of taking
spin_lock.
[Note: A similar rcu usage can be done to the existing
       bpf_prog_get_fd_by_id() in a follow up patch]

When processing the BPF_BTF_GET_FD_BY_ID cmd,
refcount_inc_not_zero() is needed because the BTF object
could be already in the rcu dead row .  btf_get() is
removed since its usage is currently limited to btf.c
alone.  refcount_inc() is used directly instead.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau
2018-05-04 14:49:51 -07:00
committed by Daniel Borkmann
parent 82e9697250
commit 78958fca7e
4 changed files with 128 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
include/uapi/linux/bpf.h
View File

@@ -96,6 +96,7 @@ enum bpf_cmd {
BPF_PROG_QUERY,
BPF_RAW_TRACEPOINT_OPEN,
BPF_BTF_LOAD,
BPF_BTF_GET_FD_BY_ID,
};
enum bpf_map_type {
@@ -344,6 +345,7 @@ union bpf_attr {
__u32 start_id;
__u32 prog_id;
__u32 map_id;
__u32 btf_id;
};
__u32 next_id;
__u32 open_flags;
@@ -2130,6 +2132,9 @@ struct bpf_map_info {
__u32 ifindex;
__u64 netns_dev;
__u64 netns_ino;
__u32 btf_id;
__u32 btf_key_id;
__u32 btf_value_id;
} __attribute__((aligned(8)));
/* User bpf_sock_addr struct to access socket fields and sockaddr struct passed