bpf: Prepare to reuse get_ctx_arg_idx

JIRA: https://issues.redhat.com/browse/RHEL-78203

commit a1b669e
Author: Amery Hung <ameryhung@gmail.com>
Date:   Wed Apr 9 14:45:57 2025 -0700

    bpf: Prepare to reuse get_ctx_arg_idx
    
    Rename get_ctx_arg_idx to bpf_ctx_arg_idx, and allow others to call it.
    No functional change.
    
    Signed-off-by: Amery Hung <ameryhung@gmail.com>
    Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
    Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
    Link: https://patch.msgid.link/20250409214606.2000194-2-ameryhung@gmail.com

Signed-off-by: Viktor Malik <vmalik@redhat.com>

Author: viktormalik

include/linux/btf.h

@@ -522,6 +522,7 @@ bool btf_param_match_suffix(const struct btf *btf,
 			    const char *suffix);
 int btf_ctx_arg_offset(const struct btf *btf, const struct btf_type *func_proto,
 		       u32 arg_no);
+u32 btf_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto, int off);
 
 struct bpf_verifier_log;
 

kernel/bpf/btf.c

@@ -6391,8 +6391,8 @@ static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
 	return btf_type_is_int(t);
 }
 
-static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
-			   int off)
+u32 btf_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
+		    int off)
 {
 	const struct btf_param *args;
 	const struct btf_type *t;
@@ -6671,7 +6671,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 			tname, off);
 		return false;
 	}
-	arg = get_ctx_arg_idx(btf, t, off);
+	arg = btf_ctx_arg_idx(btf, t, off);
 	args = (const struct btf_param *)(t + 1);
 	/* if (t == NULL) Fall back to default BPF prog with
 	 * MAX_BPF_FUNC_REG_ARGS u64 arguments.