[PATCH bpf-next v2 0/2] Add resolve_btfids support for __arena kfunc suffix

[PATCH bpf-next v2 0/2] Add resolve_btfids support for __arena kfunc suffix

[Kumar Kartikeya Dwivedi]

Use __arena/__arena__nullable suffixes to emit address_space(1)
annotations on kfunc definitions in vmlinux.h. See commits for details.

Changelog:
----------
v1 -> v2
v1: https://lore.kernel.org/bpf/20260809085155.3305519-1-memxor@gmail.com

 * Avoid enumerating all the ways resolve_btfids can emit the
   "address_space(1)" attribute in its header comment and in kfuncs.rst.
   (Ihor)
 * Drop the kfunc_has_arena_arg() helper: add_arena_tagged_proto()
   returns the original prototype when nothing needs tagging, so it can
   be invoked unconditionally for every kfunc. (Ihor)
 * Add resolve_btfids selftest cases with mixed tagged and untagged
   arguments, and a kfunc that combines the KF_ARENA_RET flag with
   suffixed arena arguments. (Ihor)

Kumar Kartikeya Dwivedi (2):
  resolve_btfids: Emit arena attributes from kfunc parameter suffixes
  selftests/bpf: Test resolve_btfids arena argument suffixes

 Documentation/bpf/kfuncs.rst                  |  4 +-
 tools/bpf/resolve_btfids/main.c               | 72 +++++++++++++------
 .../selftests/bpf/prog_tests/resolve_btfids.c | 41 ++++++-----
 tools/testing/selftests/bpf/progs/btf_data.c  | 20 ++++++
 4 files changed, 99 insertions(+), 38 deletions(-)


base-commit: 3a59f11e0f989bdd637c87151992605a6559a7cb
-- 
2.53.0

[PATCH bpf-next v2 1/2] resolve_btfids: Emit arena attributes from kfunc parameter suffixes

[Kumar Kartikeya Dwivedi]

Kfunc declarations can identify arena arguments through parameter name
suffixes without repeating KF_ARENA_ARG flags in their BTF ID sets.
resolve_btfids currently misses those arguments when synthesizing the
address_space(1) attributes used by generated vmlinux.h files.

Teach the arena prototype rewrite to recognize __arena and
__arena__nullable directly on each parameter. Keep KF_ARENA_ARG1 and
KF_ARENA_ARG2 handling for explicitly flagged kfuncs, while allowing
suffixes on any argument without synthesizing kfunc flags.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 Documentation/bpf/kfuncs.rst    |  4 +-
 tools/bpf/resolve_btfids/main.c | 72 ++++++++++++++++++++++++---------
 2 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 1004eb0bec61..10e725cbe64c 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -513,8 +513,8 @@ At kernel build time the ``resolve_btfids`` tool finds all kfuncs declared with
 ``BTF_KFUNCS_START()`` and emits their BTF annotations into the kernel's BTF.
 For each kfunc it emits a ``bpf_kfunc`` BTF decl tag, a ``bpf_fastcall`` decl
 tag when the kfunc is flagged ``KF_FASTCALL``, and the ``address_space(1)`` type
-attribute on the return value and/or arguments flagged ``KF_ARENA_RET``,
-``KF_ARENA_ARG1`` or ``KF_ARENA_ARG2`` (see section 2.8).
+attribute on the return value and/or arguments that use arena pointers (see
+sections 2.3.8 and 2.8).
 
 2.7  Specifying no-cast aliases with ___init
 --------------------------------------------
diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index d2e4176339da..37d7e7224207 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -64,8 +64,8 @@
  * each such kfunc it:
  *
  *   - emits a "bpf_kfunc" decl tag, and "bpf_fastcall" when KF_FASTCALL is set;
- *   - wraps the return value and/or arguments flagged KF_ARENA_RET,
- *     KF_ARENA_ARG1 or KF_ARENA_ARG2 with the "address_space(1)" type attribute;
+ *   - wraps the return value and/or arguments that use arena pointers
+ *     with the "address_space(1)" type attribute;
  *   - rewrites the prototype of KF_IMPLICIT_ARGS kfuncs.
  *
  * These kfunc annotations were historically produced by pahole.
@@ -182,6 +182,8 @@ struct object {
 #define KF_IMPLICIT_ARGS (1 << 16)
 #define KF_IMPL_SUFFIX "_impl"
 #define TYPE_ATTR_ARENA "address_space(1)"
+#define PARAM_SUFFIX_ARENA "__arena"
+#define PARAM_SUFFIX_ARENA_NULLABLE "__arena__nullable"
 
 struct kfunc {
 	struct rb_node rb_node;
@@ -1067,6 +1069,22 @@ static int collect_decl_tags(struct btf2btf_context *ctx)
 	return 0;
 }
 
+static bool param_name_has_suffix(const char *name, const char *suffix)
+{
+	size_t name_len = strlen(name);
+	size_t suffix_len = strlen(suffix);
+
+	return name_len >= suffix_len && !strcmp(name + name_len - suffix_len, suffix);
+}
+
+static bool is_arena_param(const struct btf *btf, const struct btf_param *param)
+{
+	const char *name = btf__name_by_offset(btf, param->name_off);
+
+	return param_name_has_suffix(name, PARAM_SUFFIX_ARENA) ||
+	       param_name_has_suffix(name, PARAM_SUFFIX_ARENA_NULLABLE);
+}
+
 static int collect_kfuncs(struct object *obj, struct btf2btf_context *ctx)
 {
 	Elf_Data *idlist = obj->efile.idlist;
@@ -1299,8 +1317,12 @@ static int process_kfunc_with_implicit_args(struct btf2btf_context *ctx, struct
 	return 0;
 }
 
-static bool is_arena_arg(struct kfunc *kfunc, u32 idx)
+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;
@@ -1339,23 +1361,36 @@ static s32 arena_tag_ptr(struct btf *btf, u32 ptr_id, struct kfunc *kfunc)
 }
 
 /*
- * Add a FUNC_PROTO for @kfunc with each relevant pointer tagged with
- * an "address_space(1)" attribute. The original proto may be shared
- * with other FUNCs, so it is never modified in place.
+ * Add a FUNC_PROTO for @kfunc with each arena pointer tagged with an
+ * "address_space(1)" attribute. The original proto may be shared with
+ * other FUNCs, so it is never modified in place. Returns the original
+ * proto id when @kfunc has no arena return value or arguments.
  */
 static s32 add_arena_tagged_proto(struct btf *btf, struct kfunc *kfunc)
 {
 	const struct btf_type *func = btf__type_by_id(btf, kfunc->btf_id);
 	u32 proto_id = func->type;
 	const struct btf_type *proto = btf__type_by_id(btf, proto_id);
+	const struct btf_param *params = btf_params(proto);
 	u32 nr_params = btf_vlen(proto);
 	s32 ret_type_id = proto->type;
 	const struct btf_type *t;
-	struct btf_param *params;
+	struct btf_param *tag_params;
 	s32 new_proto_id, id;
 	const char *name;
+	bool has_arena_arg = false;
 	int err, i;
 
+	for (i = 0; i < nr_params; i++) {
+		if (is_arena_arg(btf, kfunc, &params[i], i)) {
+			has_arena_arg = true;
+			break;
+		}
+	}
+
+	if (!(kfunc->flags & KF_ARENA_RET) && !has_arena_arg)
+		return proto_id;
+
 	if (kfunc->flags & KF_ARENA_RET) {
 		ret_type_id = arena_tag_ptr(btf, ret_type_id, kfunc);
 		if (ret_type_id < 0)
@@ -1383,19 +1418,18 @@ static s32 add_arena_tagged_proto(struct btf *btf, struct kfunc *kfunc)
 	}
 
 	for (i = 0; i < nr_params; i++) {
-		if (!is_arena_arg(kfunc, i))
-			continue;
-
 		t = btf__type_by_id(btf, new_proto_id);
-		params = btf_params(t);
+		tag_params = btf_params(t);
+		if (!is_arena_arg(btf, kfunc, &tag_params[i], i))
+			continue;
 
-		id = arena_tag_ptr(btf, params[i].type, kfunc);
+		id = arena_tag_ptr(btf, tag_params[i].type, kfunc);
 		if (id < 0)
 			return id;
 
 		t = btf__type_by_id(btf, new_proto_id);
-		params = btf_params(t);
-		params[i].type = id;
+		tag_params = btf_params(t);
+		tag_params[i].type = id;
 	}
 
 	pr_debug("added arena-tagged proto for kfunc %s: %d\n", kfunc->name, new_proto_id);
@@ -1403,7 +1437,7 @@ static s32 add_arena_tagged_proto(struct btf *btf, struct kfunc *kfunc)
 	return new_proto_id;
 }
 
-static int process_kfunc_with_arena_flags(struct btf2btf_context *ctx,
+static int process_kfunc_with_arena_attrs(struct btf2btf_context *ctx,
 					  struct kfunc *kfunc)
 {
 	struct btf_type *t;
@@ -1463,11 +1497,9 @@ static int btf2btf(struct object *obj)
 				goto out;
 		}
 
-		if (kfunc->flags & (KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2)) {
-			err = process_kfunc_with_arena_flags(&ctx, kfunc);
-			if (err)
-				goto out;
-		}
+		err = process_kfunc_with_arena_attrs(&ctx, kfunc);
+		if (err)
+			goto out;
 	}
 
 	err = 0;
-- 
2.53.0

[PATCH bpf-next v2 2/2] selftests/bpf: Test resolve_btfids arena argument suffixes

[Kumar Kartikeya Dwivedi]

Add a suffix-only kfunc declaration with arena annotations on all five
arguments. Verify that resolve_btfids emits address_space(1) type tags
for every position without KF_ARENA_ARG flags in the BTF ID sets.

Represent expected arena arguments as a per-parameter bitmap so the
test covers suffixes beyond the two positions expressible by flags.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/prog_tests/resolve_btfids.c | 41 +++++++++++--------
 tools/testing/selftests/bpf/progs/btf_data.c  | 20 +++++++++
 2 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index 732cfed35e1c..3f9949e8227d 100644
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -15,6 +15,7 @@
 #define DECL_TAG_FASTCALL "bpf_fastcall"
 #define DECL_TAG_KFUNC "bpf_kfunc"
 #define TYPE_ATTR_ARENA "address_space(1)"
+#define ARENA_ARG(n) (1U << (n))
 
 #ifndef KF_FASTCALL
 #define KF_FASTCALL (1 << 12)
@@ -49,13 +50,20 @@ struct kfunc_symbol {
 	const char	*name;
 	s32		 id;
 	u32		 flags;
+	u32		 arena_args;
+	bool		 arena_ret;
 };
 
 static struct kfunc_symbol kfunc_symbols[] = {
-	{ "kfunc_a", -1, 0 },
-	{ "kfunc_b", -1, KF_FASTCALL },
-	{ "kfunc_c", -1, KF_ARENA_RET | KF_ARENA_ARG1 | KF_ARENA_ARG2 },
-	{ "kfunc_d", -1, KF_ARENA_ARG2 },
+	{ "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_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 },
+	{ "kfunc_g", -1, KF_ARENA_RET, ARENA_ARG(0) | ARENA_ARG(1), true },
 };
 
 /* Align the .BTF_ids section to 4 bytes */
@@ -105,6 +113,9 @@ 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_e)
+BTF_ID_FLAGS(func, kfunc_f)
+BTF_ID_FLAGS(func, kfunc_g, KF_ARENA_RET)
 BTF_KFUNCS_END(test_kfunc_set)
 
 /*
@@ -112,6 +123,9 @@ BTF_KFUNCS_END(test_kfunc_set)
  * actually sort at least one of the two sets.
  */
 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_b, KF_FASTCALL)
@@ -301,15 +315,15 @@ void test_resolve_btfids(void)
 	}
 
 	/*
-	 * Check resolve_btfids wrapped exactly the arena-flagged return/args
-	 * with the address_space(1) type attribute, and left other
+	 * Check resolve_btfids wrapped exactly the arena-flagged or suffixed
+	 * return/args with the address_space(1) type attribute, and left other
 	 * pointers/returns untouched.
 	 */
 	for (i = 0; i < ARRAY_SIZE(kfunc_symbols); i++) {
 		const struct btf_type *fn, *proto;
 		const struct btf_param *params;
 		const char *name = kfunc_symbols[i].name;
-		u32 fl = kfunc_symbols[i].flags;
+		u32 arena_args = kfunc_symbols[i].arena_args;
 		__u32 nr;
 
 		fn = btf__type_by_id(btf, kfunc_symbols[i].id);
@@ -322,15 +336,10 @@ void test_resolve_btfids(void)
 		nr = btf_vlen(proto);
 
 		ASSERT_EQ(is_arena_tagged_ptr(btf, proto->type),
-			  !!(fl & KF_ARENA_RET), name);
-		if (nr > 0) {
-			ASSERT_EQ(is_arena_tagged_ptr(btf, params[0].type),
-				  !!(fl & KF_ARENA_ARG1), name);
-		}
-		if (nr > 1) {
-			ASSERT_EQ(is_arena_tagged_ptr(btf, params[1].type),
-				  !!(fl & KF_ARENA_ARG2), name);
-		}
+			  kfunc_symbols[i].arena_ret, name);
+		for (j = 0; j < nr; j++)
+			ASSERT_EQ(is_arena_tagged_ptr(btf, params[j].type),
+				  !!(arena_args & ARENA_ARG(j)), name);
 	}
 
 out:
diff --git a/tools/testing/selftests/bpf/progs/btf_data.c b/tools/testing/selftests/bpf/progs/btf_data.c
index ec34f7a6e038..8082c13490ab 100644
--- a/tools/testing/selftests/bpf/progs/btf_data.c
+++ b/tools/testing/selftests/bpf/progs/btf_data.c
@@ -68,3 +68,23 @@ int kfunc_d(struct root_struct *a, struct root_struct *b)
 {
 	return 0;
 }
+
+int kfunc_e(struct root_struct *a__arena,
+	    struct root_struct *b__arena__nullable,
+	    struct root_struct *c__arena,
+	    struct root_struct *d__arena__nullable,
+	    struct root_struct *e__arena)
+{
+	return 0;
+}
+
+int kfunc_f(struct root_struct *a, struct root_struct *b__arena, int flags)
+{
+	return 0;
+}
+
+struct root_struct *kfunc_g(struct root_struct *a__arena,
+			    struct root_struct *b__arena__nullable)
+{
+	return a__arena;
+}
-- 
2.53.0

Re: [PATCH bpf-next v2 2/2] selftests/bpf: Test resolve_btfids arena argument suffixes

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1301 bytes --]

> selftests/bpf: Test resolve_btfids arena argument suffixes
>
> Add a suffix-only kfunc declaration with arena annotations on all five
> arguments. Verify that resolve_btfids emits address_space(1) type tags
> for every position without KF_ARENA_ARG flags in the BTF ID sets.
>
> Represent expected arena arguments as a per-parameter bitmap so the
> test covers suffixes beyond the two positions expressible by flags.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

This isn't a bug, but would it be worth mentioning kfunc_f and kfunc_g in
the changelog?

The description talks about "a suffix-only kfunc declaration with arena
annotations on all five arguments" (which is kfunc_e), but the patch also
adds kfunc_f (a mixed prototype where only the second of three parameters
is suffixed and the third is a non-pointer) and kfunc_g (suffixes combined
with KF_ARENA_RET).

kfunc_f and kfunc_g arguably cover more interesting cases since they pin
down that unsuffixed and non-pointer parameters stay untagged and that
suffixes and flags compose.


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31635245405

Re: [PATCH bpf-next v2 1/2] resolve_btfids: Emit arena attributes from kfunc parameter suffixes

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 3334 bytes --]

>     resolve_btfids: Emit arena attributes from kfunc parameter suffixes
>
>     Kfunc declarations can identify arena arguments through parameter name
>     suffixes without repeating KF_ARENA_ARG flags in their BTF ID sets.
>     resolve_btfids currently misses those arguments when synthesizing the
>     address_space(1) attributes used by generated vmlinux.h files.
>
>     Teach the arena prototype rewrite to recognize __arena and
>     __arena__nullable directly on each parameter. Keep KF_ARENA_ARG1 and
>     KF_ARENA_ARG2 handling for explicitly flagged kfuncs, while allowing
>     suffixes on any argument without synthesizing kfunc flags.
>
>     Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

This looks like a bug fix for missing arena suffix handling. Should this
include:

  Fixes: 27a78c2e7eee ("resolve_btfids: Process KF_ARENA_* flags in resolve_btfids")

> diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
> index 1004eb0bec617..10e725cbe64cd 100644
> --- a/Documentation/bpf/kfuncs.rst
> +++ b/Documentation/bpf/kfuncs.rst

[ ... ]

> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index d2e4176339da6..37d7e7224207d 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c

[ ... ]

> @@ -1067,6 +1069,22 @@ static int collect_decl_tags(struct btf2btf_context *ctx)
>  	return 0;
>  }
>
> +static bool param_name_has_suffix(const char *name, const char *suffix)
> +{
> +	size_t name_len = strlen(name);
> +	size_t suffix_len = strlen(suffix);
> +
> +	return name_len >= suffix_len && !strcmp(name + name_len - suffix_len, suffix);
> +}

Does this accept parameter names that are exactly "__arena" or
"__arena__nullable"?  The kernel's btf_param_match_suffix() in
kernel/bpf/btf.c deliberately rejects that case:

    len = strlen(param_name);
    if (len <= suffix_len)
            return false;

Both verifier and JIT go through that helper. If resolve_btfids uses >= but
the kernel uses >, a parameter whose whole name is the suffix would get
address_space(1) in the generated vmlinux.h but would be treated as an
ordinary pointer by the verifier and JIT. The header and kernel would then
disagree about the calling convention.

Should the comparison here be name_len > suffix_len to match the kernel?

> +
> +static bool is_arena_param(const struct btf *btf, const struct btf_param *param)
> +{
> +	const char *name = btf__name_by_offset(btf, param->name_off);
> +
> +	return param_name_has_suffix(name, PARAM_SUFFIX_ARENA) ||
> +	       param_name_has_suffix(name, PARAM_SUFFIX_ARENA_NULLABLE);
> +}

[ ... ]

> @@ -1299,8 +1317,12 @@ static int process_kfunc_with_implicit_args(struct btf2btf_context *ctx, struct
>  	return 0;
>  }
>
> -static bool is_arena_arg(struct kfunc *kfunc, u32 idx)
> +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;

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31635245405

Re: [PATCH bpf-next v2 0/2] Add resolve_btfids support for __arena kfunc suffix

[Ihor Solodrai]

On 8/12/26 12:38 PM, Kumar Kartikeya Dwivedi wrote:
> Use __arena/__arena__nullable suffixes to emit address_space(1)
> annotations on kfunc definitions in vmlinux.h. See commits for details.
> 
> Changelog:
> ----------
> v1 -> v2
> v1: https://lore.kernel.org/bpf/20260809085155.3305519-1-memxor@gmail.com
> 
>  * Avoid enumerating all the ways resolve_btfids can emit the
>    "address_space(1)" attribute in its header comment and in kfuncs.rst.
>    (Ihor)
>  * Drop the kfunc_has_arena_arg() helper: add_arena_tagged_proto()
>    returns the original prototype when nothing needs tagging, so it can
>    be invoked unconditionally for every kfunc. (Ihor)
>  * Add resolve_btfids selftest cases with mixed tagged and untagged
>    arguments, and a kfunc that combines the KF_ARENA_RET flag with
>    suffixed arena arguments. (Ihor)

For the series:

Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>

Thanks!

> 
> Kumar Kartikeya Dwivedi (2):
>   resolve_btfids: Emit arena attributes from kfunc parameter suffixes
>   selftests/bpf: Test resolve_btfids arena argument suffixes
> 
>  Documentation/bpf/kfuncs.rst                  |  4 +-
>  tools/bpf/resolve_btfids/main.c               | 72 +++++++++++++------
>  .../selftests/bpf/prog_tests/resolve_btfids.c | 41 ++++++-----
>  tools/testing/selftests/bpf/progs/btf_data.c  | 20 ++++++
>  4 files changed, 99 insertions(+), 38 deletions(-)
> 
> 
> base-commit: 3a59f11e0f989bdd637c87151992605a6559a7cb

Re: [PATCH bpf-next v2 0/2] Add resolve_btfids support for __arena kfunc suffix

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Eduard Zingerman <eddyz87@gmail.com>:

On Wed, 12 Aug 2026 21:38:39 +0200 you wrote:
> Use __arena/__arena__nullable suffixes to emit address_space(1)
> annotations on kfunc definitions in vmlinux.h. See commits for details.
> 
> Changelog:
> ----------
> v1 -> v2
> v1: https://lore.kernel.org/bpf/20260809085155.3305519-1-memxor@gmail.com
> 
> [...]

Here is the summary with links:
  - [bpf-next,v2,1/2] resolve_btfids: Emit arena attributes from kfunc parameter suffixes
    https://git.kernel.org/bpf/bpf-next/c/5e31d32843d3
  - [bpf-next,v2,2/2] selftests/bpf: Test resolve_btfids arena argument suffixes
    https://git.kernel.org/bpf/bpf-next/c/d7842e98ca17

You are awesome, thank you!
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