btf: Extend UAPI to support BTF location (inline site) info

Add BTF_KIND_LOC_PARAM, BTF_KIND_LOC_PROTO and BTF_KIND_LOCSEC
to help represent location information for functions.

BTF_KIND_LOC_PARAM is used to represent how we retrieve data at a
location; either via register(s), or register+offset, a dereference
of a register+offset or a constant value.

BTF_KIND_LOC_PROTO represents location information about a location
with multiple BTF_KIND_LOC_PARAMs.

And finally BTF_KIND_LOCSEC is a set of location sites, each
of which has

- a BTF_KIND_FUNC function associated with the inline site
- a location prototype specifying where to find the function
  parameters
- an address offset relative to the kernel base address

This can be used to support representing

- a fully-inlined function at potentially multiple inline sites
  with potentially different parameter availability
- a partially-inlined function where some _LOC_PROTOs represent
  inlined sites as above and others have normal _FUNC representations

Also BTF_KIND_LOCSEC struct btf_loc will have two type id
references; one for the associated func, the other for the loc_proto.
Accordingly increase the number of m_offs references in btf_field_desc
to 2.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260924111428.75957-2-alan.maguire@oracle.com

1 files changed, 21 insertions, 1 deletions

diff --git a/include/linux/btf.h b/include/linux/btf.h
index ddd0f4f32d24..f29ed358b7a8 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -261,6 +261,11 @@ const char *btf_type_str(const struct btf_type *t);
 	     i < btf_type_vlen(datasec_type);			\
 	     i++, member++)
 
+#define for_each_loc(i, locsec_type, member)			\
+	for (i = 0, member = btf_type_loc_secinfo(locsec_type);	\
+	     i < btf_type_vlen(locsec_type);			\
+	     i++, member++)
+
 static inline bool btf_type_is_ptr(const struct btf_type *t)
 {
 	return BTF_INFO_KIND(t->info) == BTF_KIND_PTR;
@@ -329,6 +334,21 @@ static inline u64 btf_enum64_value(const struct btf_enum64 *e)
 	return ((u64)e->val_hi32 << 32) | e->val_lo32;
 }
 
+static inline struct btf_loc_param *btf_loc_param(const struct btf_type *t)
+{
+	return (struct btf_loc_param *)(t + 1);
+}
+
+static inline __u32 *btf_loc_proto_params(const struct btf_type *t)
+{
+	return (__u32 *)(t + 1);
+}
+
+static inline struct btf_loc *btf_type_loc_secinfo(const struct btf_type *t)
+{
+	return (struct btf_loc *)(t + 1);
+}
+
 static inline bool btf_is_composite(const struct btf_type *t)
 {
 	u16 kind = btf_kind(t);
@@ -559,7 +579,7 @@ struct btf_field_desc {
 	/* member struct size, or zero, if no members */
 	int m_sz;
 	/* repeated per-member offsets */
-	int m_off_cnt, m_offs[1];
+	int m_off_cnt, m_offs[2];
 };
 
 struct btf_field_iter {