Merge branch 'bpf-support-dumping-kfunc-prototypes-from-btf'

Daniel Xu says:

====================
bpf: Support dumping kfunc prototypes from BTF

This patchset enables both detecting as well as dumping compilable
prototypes for kfuncs.

The first commit instructs pahole to DECL_TAG kfuncs when available.
This requires v1.27 which was released on 6/11/24. With it, users will
be able to look at BTF inside vmlinux (or modules) and check if the
kfunc they want is available.

The final commit teaches bpftool how to dump kfunc prototypes. This
is done for developer convenience.

The rest of the commits are fixups to enable selftests to use the
newly dumped kfunc prototypes. With these, selftests will regularly
exercise the newly added codepaths.

Tested with and without the required pahole changes:

  * https://github.com/kernel-patches/bpf/pull/7186
  * https://github.com/kernel-patches/bpf/pull/7187

=== Changelog ===
From v4:
* Change bpf_session_cookie() return type
* Only fixup used fentry test kfunc prototypes
* Extract out projection detection into shared btf_is_projection_of()
* Fix kernel test robot build warnings about doc comments

From v3:
* Teach selftests to use dumped prototypes

From v2:
* Update Makefile.btf with pahole flag
* More error checking
* Output formatting changes
* Drop already-merged commit

From v1:
* Add __weak annotation
* Use btf_dump for kfunc prototypes
* Update kernel bpf_rdonly_cast() signature
====================

Link: https://lore.kernel.org/r/cover.1718207789.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 5 insertions, 4 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a834f4b761bc..f636b4998bf7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3265,8 +3265,8 @@ u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
 				struct bpf_insn *insn_buf,
 				struct bpf_prog *prog,
 				u32 *target_size);
-int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
-			       struct bpf_dynptr_kern *ptr);
+int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags,
+			       struct bpf_dynptr *ptr);
 #else
 static inline bool bpf_sock_common_is_valid_access(int off, int size,
 						   enum bpf_access_type type,
@@ -3288,8 +3288,8 @@ static inline u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
 {
 	return 0;
 }
-static inline int bpf_dynptr_from_skb_rdonly(struct sk_buff *skb, u64 flags,
-					     struct bpf_dynptr_kern *ptr)
+static inline int bpf_dynptr_from_skb_rdonly(struct __sk_buff *skb, u64 flags,
+					     struct bpf_dynptr *ptr)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/include/linux/btf.h b/include/linux/btf.h
index f9e56fd12a9f..56d91daacdba 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -531,6 +531,7 @@ s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id);
 int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
 				struct module *owner);
 struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id);
+bool btf_is_projection_of(const char *pname, const char *tname);
 bool btf_is_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
 			   const struct btf_type *t, enum bpf_prog_type prog_type,
 			   int arg);