bpf: treewide: Annotate BPF kfuncs in BTF

This commit marks kfuncs as such inside the .BTF_ids section. The upshot
of these annotations is that we'll be able to automatically generate
kfunc prototypes for downstream users. The process is as follows:

1. In source, use BTF_KFUNCS_START/END macro pair to mark kfuncs
2. During build, pahole injects into BTF a "bpf_kfunc" BTF_DECL_TAG for
   each function inside BTF_KFUNCS sets
3. At runtime, vmlinux or module BTF is made available in sysfs
4. At runtime, bpftool (or similar) can look at provided BTF and
   generate appropriate prototypes for functions with "bpf_kfunc" tag

To ensure future kfunc are similarly tagged, we now also return error
inside kfunc registration for untagged kfuncs. For vmlinux kfuncs,
we also WARN(), as initcall machinery does not handle errors.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Acked-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/e55150ceecbf0a5d961e608941165c0bee7bc943.1706491398.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

5 files changed, 10 insertions, 10 deletions

diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 834edc18463ac..7f518ea5f4ac7 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -201,13 +201,13 @@ bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 	}
 }
 
-BTF_SET8_START(bpf_tcp_ca_check_kfunc_ids)
+BTF_KFUNCS_START(bpf_tcp_ca_check_kfunc_ids)
 BTF_ID_FLAGS(func, tcp_reno_ssthresh)
 BTF_ID_FLAGS(func, tcp_reno_cong_avoid)
 BTF_ID_FLAGS(func, tcp_reno_undo_cwnd)
 BTF_ID_FLAGS(func, tcp_slow_start)
 BTF_ID_FLAGS(func, tcp_cong_avoid_ai)
-BTF_SET8_END(bpf_tcp_ca_check_kfunc_ids)
+BTF_KFUNCS_END(bpf_tcp_ca_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_tcp_ca_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/fou_bpf.c b/net/ipv4/fou_bpf.c
index 4da03bf45c9b7..06e5572f296f1 100644
--- a/net/ipv4/fou_bpf.c
+++ b/net/ipv4/fou_bpf.c
@@ -100,10 +100,10 @@ __bpf_kfunc int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
 
 __bpf_kfunc_end_defs();
 
-BTF_SET8_START(fou_kfunc_set)
+BTF_KFUNCS_START(fou_kfunc_set)
 BTF_ID_FLAGS(func, bpf_skb_set_fou_encap)
 BTF_ID_FLAGS(func, bpf_skb_get_fou_encap)
-BTF_SET8_END(fou_kfunc_set)
+BTF_KFUNCS_END(fou_kfunc_set)
 
 static const struct btf_kfunc_id_set fou_bpf_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index 22358032dd484..05dc2d05bc7cb 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -1155,7 +1155,7 @@ static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = {
 	.set_state	= bbr_set_state,
 };
 
-BTF_SET8_START(tcp_bbr_check_kfunc_ids)
+BTF_KFUNCS_START(tcp_bbr_check_kfunc_ids)
 #ifdef CONFIG_X86
 #ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, bbr_init)
@@ -1168,7 +1168,7 @@ BTF_ID_FLAGS(func, bbr_min_tso_segs)
 BTF_ID_FLAGS(func, bbr_set_state)
 #endif
 #endif
-BTF_SET8_END(tcp_bbr_check_kfunc_ids)
+BTF_KFUNCS_END(tcp_bbr_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_bbr_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 0fd78ecb67e75..44869ea089e34 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -485,7 +485,7 @@ static struct tcp_congestion_ops cubictcp __read_mostly = {
 	.name		= "cubic",
 };
 
-BTF_SET8_START(tcp_cubic_check_kfunc_ids)
+BTF_KFUNCS_START(tcp_cubic_check_kfunc_ids)
 #ifdef CONFIG_X86
 #ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, cubictcp_init)
@@ -496,7 +496,7 @@ BTF_ID_FLAGS(func, cubictcp_cwnd_event)
 BTF_ID_FLAGS(func, cubictcp_acked)
 #endif
 #endif
-BTF_SET8_END(tcp_cubic_check_kfunc_ids)
+BTF_KFUNCS_END(tcp_cubic_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_cubic_kfunc_set = {
 	.owner = THIS_MODULE,
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index bb23bb5b387a0..e33fbe4933e42 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -260,7 +260,7 @@ static struct tcp_congestion_ops dctcp_reno __read_mostly = {
 	.name		= "dctcp-reno",
 };
 
-BTF_SET8_START(tcp_dctcp_check_kfunc_ids)
+BTF_KFUNCS_START(tcp_dctcp_check_kfunc_ids)
 #ifdef CONFIG_X86
 #ifdef CONFIG_DYNAMIC_FTRACE
 BTF_ID_FLAGS(func, dctcp_init)
@@ -271,7 +271,7 @@ BTF_ID_FLAGS(func, dctcp_cwnd_undo)
 BTF_ID_FLAGS(func, dctcp_state)
 #endif
 #endif
-BTF_SET8_END(tcp_dctcp_check_kfunc_ids)
+BTF_KFUNCS_END(tcp_dctcp_check_kfunc_ids)
 
 static const struct btf_kfunc_id_set tcp_dctcp_kfunc_set = {
 	.owner = THIS_MODULE,