[PATCH bpf-next v3 1/4] bpf: Add support for kfunc set with common btf_ids

[Yonghong Song <yhs@xxxxxx>]

Later on, we will introduce kfuncs bpf_cast_to_kern_ctx() and
bpf_rdonly_cast() which apply to all program types. Currently kfunc set
only supports individual prog types. This patch added support for kfunc
applying to all program types.

Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
 kernel/bpf/btf.c     |  8 ++++++++
 kernel/bpf/helpers.c | 12 +++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index d52054ec69c9..1c78d4df9e18 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -199,6 +199,7 @@ DEFINE_IDR(btf_idr);
 DEFINE_SPINLOCK(btf_idr_lock);
 
 enum btf_kfunc_hook {
+	BTF_KFUNC_HOOK_COMMON,
 	BTF_KFUNC_HOOK_XDP,
 	BTF_KFUNC_HOOK_TC,
 	BTF_KFUNC_HOOK_STRUCT_OPS,
@@ -7531,6 +7532,8 @@ static u32 *__btf_kfunc_id_set_contains(const struct btf *btf,
 static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
 {
 	switch (prog_type) {
+	case BPF_PROG_TYPE_UNSPEC:
+		return BTF_KFUNC_HOOK_COMMON;
 	case BPF_PROG_TYPE_XDP:
 		return BTF_KFUNC_HOOK_XDP;
 	case BPF_PROG_TYPE_SCHED_CLS:
@@ -7559,6 +7562,11 @@ u32 *btf_kfunc_id_set_contains(const struct btf *btf,
 			       u32 kfunc_btf_id)
 {
 	enum btf_kfunc_hook hook;
+	u32 *kfunc_flags;
+
+	kfunc_flags = __btf_kfunc_id_set_contains(btf, BTF_KFUNC_HOOK_COMMON, kfunc_btf_id);
+	if (kfunc_flags)
+		return kfunc_flags;
 
 	hook = bpf_prog_type_to_kfunc_hook(prog_type);
 	return __btf_kfunc_id_set_contains(btf, hook, kfunc_btf_id);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 89a95f3d854c..6b2de097b950 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1903,10 +1903,19 @@ static const struct btf_kfunc_id_set generic_kfunc_set = {
 	.set   = &generic_btf_ids,
 };
 
+
 BTF_ID_LIST(generic_dtor_ids)
 BTF_ID(struct, task_struct)
 BTF_ID(func, bpf_task_release)
 
+BTF_SET8_START(common_btf_ids)
+BTF_SET8_END(common_btf_ids)
+
+static const struct btf_kfunc_id_set common_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set   = &common_btf_ids,
+};
+
 static int __init kfunc_init(void)
 {
 	int ret;
@@ -1920,9 +1929,10 @@ static int __init kfunc_init(void)
 	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &generic_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &generic_kfunc_set);
-	return ret ?: register_btf_id_dtor_kfuncs(generic_dtors,
+	ret = ret ?: register_btf_id_dtor_kfuncs(generic_dtors,
 						  ARRAY_SIZE(generic_dtors),
 						  THIS_MODULE);
+	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC, &common_kfunc_set);
 }
 
 late_initcall(kfunc_init);
-- 
2.30.2