[PATCH bpf-next v1 12/14] resolve_btfids: Drop KF_ARENA_ARG flag support

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

Arena argument suffixes now describe the address-space contract at any
parameter position, while the kernel no longer publishes KF_ARENA_ARG1
or KF_ARENA_ARG2. Keeping private copies in resolve_btfids would leave an
obsolete second annotation mechanism and silently accept flags the
kernel no longer understands.

Derive arena arguments exclusively from their suffixes and retain
KF_ARENA_RET for functions returning arena pointers. Update the resolver
selftest to distinguish return-only flags, unannotated pointer arguments,
and suffix-annotated arguments.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/bpf/resolve_btfids/main.c               | 22 ++-----------------
 .../selftests/bpf/prog_tests/resolve_btfids.c | 22 ++++++-------------
 2 files changed, 9 insertions(+), 35 deletions(-)

diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index 37d7e7224207..3dbf329edb46 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -177,8 +177,6 @@ struct object {
 
 #define KF_FASTCALL	(1 << 12)
 #define KF_ARENA_RET	(1 << 13)
-#define KF_ARENA_ARG1	(1 << 14)
-#define KF_ARENA_ARG2	(1 << 15)
 #define KF_IMPLICIT_ARGS (1 << 16)
 #define KF_IMPL_SUFFIX "_impl"
 #define TYPE_ATTR_ARENA "address_space(1)"
@@ -1317,22 +1315,6 @@ static int process_kfunc_with_implicit_args(struct btf2btf_context *ctx, struct
 	return 0;
 }
 
-static bool is_arena_arg(const struct btf *btf, const struct kfunc *kfunc,
-			 const struct btf_param *param, u32 idx)
-{
-	if (is_arena_param(btf, param))
-		return true;
-
-	switch (idx) {
-	case 0:
-		return kfunc->flags & KF_ARENA_ARG1;
-	case 1:
-		return kfunc->flags & KF_ARENA_ARG2;
-	default:
-		return false;
-	}
-}
-
 static s32 arena_tag_ptr(struct btf *btf, u32 ptr_id, struct kfunc *kfunc)
 {
 	const struct btf_type *ptr = btf__type_by_id(btf, ptr_id);
@@ -1382,7 +1364,7 @@ static s32 add_arena_tagged_proto(struct btf *btf, struct kfunc *kfunc)
 	int err, i;
 
 	for (i = 0; i < nr_params; i++) {
-		if (is_arena_arg(btf, kfunc, &params[i], i)) {
+		if (is_arena_param(btf, &params[i])) {
 			has_arena_arg = true;
 			break;
 		}
@@ -1420,7 +1402,7 @@ static s32 add_arena_tagged_proto(struct btf *btf, struct kfunc *kfunc)
 	for (i = 0; i < nr_params; i++) {
 		t = btf__type_by_id(btf, new_proto_id);
 		tag_params = btf_params(t);
-		if (!is_arena_arg(btf, kfunc, &tag_params[i], i))
+		if (!is_arena_param(btf, &tag_params[i]))
 			continue;
 
 		id = arena_tag_ptr(btf, tag_params[i].type, kfunc);
diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index 3f9949e8227d..a4381c7fa7da 100644
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -23,13 +23,6 @@
 #ifndef KF_ARENA_RET
 #define KF_ARENA_RET  (1 << 13)
 #endif
-#ifndef KF_ARENA_ARG1
-#define KF_ARENA_ARG1 (1 << 14)
-#endif
-#ifndef KF_ARENA_ARG2
-#define KF_ARENA_ARG2 (1 << 15)
-#endif
-
 struct symbol {
 	const char	*name;
 	int		 type;
@@ -57,9 +50,8 @@ struct kfunc_symbol {
 static struct kfunc_symbol kfunc_symbols[] = {
 	{ "kfunc_a", -1, 0, 0, false },
 	{ "kfunc_b", -1, KF_FASTCALL, 0, false },
-	{ "kfunc_c", -1, KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2,
-	  ARENA_ARG(0) | ARENA_ARG(1), true },
-	{ "kfunc_d", -1, KF_ARENA_ARG2, ARENA_ARG(1), false },
+	{ "kfunc_c", -1, KF_ARENA_RET, 0, true },
+	{ "kfunc_d", -1, 0, 0, false },
 	{ "kfunc_e", -1, 0, ARENA_ARG(0) | ARENA_ARG(1) | ARENA_ARG(2) |
 	  ARENA_ARG(3) | ARENA_ARG(4), false },
 	{ "kfunc_f", -1, 0, ARENA_ARG(1), false },
@@ -111,8 +103,8 @@ BTF_SET_END(test_set)
 BTF_KFUNCS_START(test_kfunc_set)
 BTF_ID_FLAGS(func, kfunc_a)
 BTF_ID_FLAGS(func, kfunc_b, KF_FASTCALL)
-BTF_ID_FLAGS(func, kfunc_c, KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2)
-BTF_ID_FLAGS(func, kfunc_d, KF_ARENA_ARG2)
+BTF_ID_FLAGS(func, kfunc_c, KF_ARENA_RET)
+BTF_ID_FLAGS(func, kfunc_d)
 BTF_ID_FLAGS(func, kfunc_e)
 BTF_ID_FLAGS(func, kfunc_f)
 BTF_ID_FLAGS(func, kfunc_g, KF_ARENA_RET)
@@ -126,8 +118,8 @@ BTF_KFUNCS_START(test_kfunc_set_rev)
 BTF_ID_FLAGS(func, kfunc_g, KF_ARENA_RET)
 BTF_ID_FLAGS(func, kfunc_f)
 BTF_ID_FLAGS(func, kfunc_e)
-BTF_ID_FLAGS(func, kfunc_d, KF_ARENA_ARG2)
-BTF_ID_FLAGS(func, kfunc_c, KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2)
+BTF_ID_FLAGS(func, kfunc_d)
+BTF_ID_FLAGS(func, kfunc_c, KF_ARENA_RET)
 BTF_ID_FLAGS(func, kfunc_b, KF_FASTCALL)
 BTF_ID_FLAGS(func, kfunc_a)
 BTF_KFUNCS_END(test_kfunc_set_rev)
@@ -315,7 +307,7 @@ void test_resolve_btfids(void)
 	}
 
 	/*
-	 * Check resolve_btfids wrapped exactly the arena-flagged or suffixed
+	 * Check resolve_btfids wrapped exactly the arena return or suffixed
 	 * return/args with the address_space(1) type attribute, and left other
 	 * pointers/returns untouched.
 	 */
-- 
2.53.0