[PATCH bpf-next v1 0/4] Modernize resolve_btfids selftest

[PATCH bpf-next v1 0/4] Modernize resolve_btfids selftest

[Ihor Solodrai]

This series updates resolve_btfids selftests to use latest selftest
helpers API and add kfunc set testing.

This series was split from a bigger series [1].  It's general selftest
improvements that don't have to be entangled with resolve_btfids
development, and makes the main series a bit smaller.

[1] https://lore.kernel.org/bpf/20260601221805.821394-1-ihor.solodrai@linux.dev/

Changes compared to original 4 patches:
  * various nits from Jiri, Andrii and Emil
  * in patch #3 (that adds gcc pragma) definitions are moved such that
    .local BTF_ID_* containers are grouped together and we have a
    single pragma scope

---

Ihor Solodrai (4):
  tools/bpf: Sync btf_ids.h to tools
  selftests/bpf: Modernize resolve_btfids test scaffolding
  selftests/bpf: Fix resolve_btfids test reads of BTF ID sets in PIE
    builds
  selftests/bpf: Add kfunc set test to resolve_btfids

 tools/include/linux/btf_ids.h                 |  78 +++++++++-
 .../selftests/bpf/prog_tests/resolve_btfids.c | 140 ++++++++++++------
 tools/testing/selftests/bpf/progs/btf_data.c  |  10 ++
 3 files changed, 177 insertions(+), 51 deletions(-)

-- 
2.54.0

[PATCH bpf-next v1 1/4] tools/bpf: Sync btf_ids.h to tools

[Ihor Solodrai]

Sync tools/include/linux/btf_ids.h with include/linux/btf_ids.h so
tools-side code can use BTF_ID_FLAGS(), BTF_SET8_START(), and
BTF_KFUNCS_START().

Keep the tools copy's existing compiler header dependency:
tools/include/linux/compiler.h already provides __maybe_unused and
tools/include/linux/compiler_attributes.h does not exist.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/include/linux/btf_ids.h | 78 ++++++++++++++++++++++++++++++++---
 1 file changed, 73 insertions(+), 5 deletions(-)

diff --git a/tools/include/linux/btf_ids.h b/tools/include/linux/btf_ids.h
index 72ea363d434d..4fe5c5f1558c 100644
--- a/tools/include/linux/btf_ids.h
+++ b/tools/include/linux/btf_ids.h
@@ -10,6 +10,9 @@ struct btf_id_set {
 	u32 ids[];
 };
 
+/* This flag implies BTF_SET8 holds kfunc(s) */
+#define BTF_SET8_KFUNCS		(1 << 0)
+
 struct btf_id_set8 {
 	u32 cnt;
 	u32 flags;
@@ -22,6 +25,7 @@ struct btf_id_set8 {
 #ifdef CONFIG_DEBUG_INFO_BTF
 
 #include <linux/compiler.h> /* for __PASTE */
+#include <linux/stringify.h>
 
 /*
  * Following macros help to define lists of BTF IDs placed
@@ -35,7 +39,7 @@ struct btf_id_set8 {
 
 #define BTF_IDS_SECTION ".BTF_ids"
 
-#define ____BTF_ID(symbol)				\
+#define ____BTF_ID(symbol, word)			\
 asm(							\
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
 ".local " #symbol " ;                          \n"	\
@@ -43,10 +47,11 @@ asm(							\
 ".size  " #symbol ", 4;                        \n"	\
 #symbol ":                                     \n"	\
 ".zero 4                                       \n"	\
+word							\
 ".popsection;                                  \n");
 
-#define __BTF_ID(symbol) \
-	____BTF_ID(symbol)
+#define __BTF_ID(symbol, word) \
+	____BTF_ID(symbol, word)
 
 #define __ID(prefix) \
 	__PASTE(__PASTE(prefix, __COUNTER__), __LINE__)
@@ -56,7 +61,14 @@ asm(							\
  * to 4 zero bytes.
  */
 #define BTF_ID(prefix, name) \
-	__BTF_ID(__ID(__BTF_ID__##prefix##__##name##__))
+	__BTF_ID(__ID(__BTF_ID__##prefix##__##name##__), "")
+
+#define ____BTF_ID_FLAGS(prefix, name, flags) \
+	__BTF_ID(__ID(__BTF_ID__##prefix##__##name##__), ".long " #flags "\n")
+#define __BTF_ID_FLAGS(prefix, name, flags, ...) \
+	____BTF_ID_FLAGS(prefix, name, flags)
+#define BTF_ID_FLAGS(prefix, name, ...) \
+	__BTF_ID_FLAGS(prefix, name, ##__VA_ARGS__, 0)
 
 /*
  * The BTF_ID_LIST macro defines pure (unsorted) list
@@ -155,10 +167,58 @@ asm(							\
 ".popsection;                                 \n");	\
 extern struct btf_id_set name;
 
+/*
+ * The BTF_SET8_START/END macros pair defines sorted list of
+ * BTF IDs and their flags plus its members count, with the
+ * following layout:
+ *
+ * BTF_SET8_START(list)
+ * BTF_ID_FLAGS(type1, name1, flags)
+ * BTF_ID_FLAGS(type2, name2, flags)
+ * BTF_SET8_END(list)
+ *
+ * __BTF_ID__set8__list:
+ * .zero 8
+ * list:
+ * __BTF_ID__type1__name1__3:
+ * .zero 4
+ * .word (1 << 0) | (1 << 2)
+ * __BTF_ID__type2__name2__5:
+ * .zero 4
+ * .word (1 << 3) | (1 << 1) | (1 << 2)
+ *
+ */
+#define __BTF_SET8_START(name, scope, flags)		\
+__BTF_ID_LIST(name, local)				\
+asm(							\
+".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\
+"." #scope " __BTF_ID__set8__" #name ";        \n"	\
+"__BTF_ID__set8__" #name ":;                   \n"	\
+".zero 4                                       \n"	\
+".long " __stringify(flags)                   "\n"	\
+".popsection;                                  \n");
+
+#define BTF_SET8_START(name)				\
+__BTF_SET8_START(name, local, 0)
+
+#define BTF_SET8_END(name)				\
+asm(							\
+".pushsection " BTF_IDS_SECTION ",\"a\";      \n"	\
+".size __BTF_ID__set8__" #name ", .-" #name "  \n"	\
+".popsection;                                 \n");	\
+extern struct btf_id_set8 name;
+
+#define BTF_KFUNCS_START(name)				\
+__BTF_SET8_START(name, local, BTF_SET8_KFUNCS)
+
+#define BTF_KFUNCS_END(name)				\
+BTF_SET8_END(name)
+
 #else
 
-#define BTF_ID_LIST(name) static u32 __maybe_unused name[5];
+#define BTF_ID_LIST(name) static u32 __maybe_unused name[128];
 #define BTF_ID(prefix, name)
+#define BTF_ID_FLAGS(prefix, name, ...)
 #define BTF_ID_UNUSED
 #define BTF_ID_LIST_GLOBAL(name, n) u32 __maybe_unused name[n];
 #define BTF_ID_LIST_SINGLE(name, prefix, typename) static u32 __maybe_unused name[1];
@@ -166,6 +226,10 @@ extern struct btf_id_set name;
 #define BTF_SET_START(name) static struct btf_id_set __maybe_unused name = { 0 };
 #define BTF_SET_START_GLOBAL(name) static struct btf_id_set __maybe_unused name = { 0 };
 #define BTF_SET_END(name)
+#define BTF_SET8_START(name) static struct btf_id_set8 __maybe_unused name = { 0 };
+#define BTF_SET8_END(name)
+#define BTF_KFUNCS_START(name) static struct btf_id_set8 __maybe_unused name = { .flags = BTF_SET8_KFUNCS };
+#define BTF_KFUNCS_END(name)
 
 #endif /* CONFIG_DEBUG_INFO_BTF */
 
@@ -215,5 +279,9 @@ MAX_BTF_TRACING_TYPE,
 };
 
 extern u32 btf_tracing_ids[];
+extern u32 bpf_cgroup_btf_id[];
+extern u32 bpf_local_storage_map_btf_id[];
+extern u32 btf_bpf_map_id[];
+extern u32 bpf_kmem_cache_btf_id[];
 
 #endif
-- 
2.54.0

[PATCH bpf-next v1 2/4] selftests/bpf: Modernize resolve_btfids test scaffolding

[Ihor Solodrai]

Refactor resolve_btfids test in order to:
  * use newer ASSERT_* macros instead of CHECK
  * extend the lifetime of loaded BTF to enable additional checks
  * cleanup unused/unnecessary code

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 .../selftests/bpf/prog_tests/resolve_btfids.c | 60 +++++++------------
 1 file changed, 20 insertions(+), 40 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index 41dfaaabb73f..e549780697c7 100644
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -10,7 +10,7 @@
 #include <linux/btf_ids.h>
 #include "test_progs.h"
 
-static int duration;
+#define BTF_DATA_FILE "resolve_btfids.test.o.BTF"
 
 struct symbol {
 	const char	*name;
@@ -70,10 +70,8 @@ __resolve_symbol(struct btf *btf, int type_id)
 	unsigned int i;
 
 	type = btf__type_by_id(btf, type_id);
-	if (!type) {
-		PRINT_FAIL("Failed to get type for ID %d\n", type_id);
+	if (!ASSERT_OK_PTR(type, "btf__type_by_id"))
 		return -1;
-	}
 
 	for (i = 0; i < ARRAY_SIZE(test_symbols); i++) {
 		if (test_symbols[i].id >= 0)
@@ -83,10 +81,8 @@ __resolve_symbol(struct btf *btf, int type_id)
 			continue;
 
 		str = btf__name_by_offset(btf, type->name_off);
-		if (!str) {
-			PRINT_FAIL("Failed to get name for BTF ID %d\n", type_id);
+		if (!ASSERT_OK_PTR(str, "btf__name_by_offset"))
 			return -1;
-		}
 
 		if (!strcmp(str, test_symbols[i].name))
 			test_symbols[i].id = type_id;
@@ -95,25 +91,15 @@ __resolve_symbol(struct btf *btf, int type_id)
 	return 0;
 }
 
-static int resolve_symbols(void)
+static int resolve_symbols(struct btf *btf)
 {
-	struct btf *btf;
+	__u32 nr = btf__type_cnt(btf);
 	int type_id;
-	__u32 nr;
-
-	btf = btf__parse_raw("resolve_btfids.test.o.BTF");
-	if (CHECK(libbpf_get_error(btf), "resolve",
-		  "Failed to load BTF from resolve_btfids.test.o.BTF\n"))
-		return -1;
-
-	nr = btf__type_cnt(btf);
 
 	for (type_id = 1; type_id < nr; type_id++) {
 		if (__resolve_symbol(btf, type_id))
-			break;
+			return -1;
 	}
-
-	btf__free(btf);
 	return 0;
 }
 
@@ -121,25 +107,22 @@ void test_resolve_btfids(void)
 {
 	__u32 *test_list, *test_lists[] = { test_list_local, test_list_global };
 	unsigned int i, j;
-	int ret = 0;
+	struct btf *btf;
 
-	if (resolve_symbols())
+	btf = btf__parse_raw(BTF_DATA_FILE);
+	if (!ASSERT_OK_PTR(btf, "btf_parse"))
 		return;
 
+	if (resolve_symbols(btf))
+		goto out;
+
 	/* Check BTF_ID_LIST(test_list_local) and
 	 * BTF_ID_LIST_GLOBAL(test_list_global) IDs
 	 */
 	for (j = 0; j < ARRAY_SIZE(test_lists); j++) {
 		test_list = test_lists[j];
-		for (i = 0; i < ARRAY_SIZE(test_symbols); i++) {
-			ret = CHECK(test_list[i] != test_symbols[i].id,
-				    "id_check",
-				    "wrong ID for %s (%d != %d)\n",
-				    test_symbols[i].name,
-				    test_list[i], test_symbols[i].id);
-			if (ret)
-				return;
-		}
+		for (i = 0; i < ARRAY_SIZE(test_symbols); i++)
+			ASSERT_EQ(test_list[i], test_symbols[i].id, test_symbols[i].name);
 	}
 
 	/* Check BTF_SET_START(test_set) IDs */
@@ -153,15 +136,12 @@ void test_resolve_btfids(void)
 			break;
 		}
 
-		ret = CHECK(!found, "id_check",
-			    "ID %d not found in test_symbols\n",
-			    test_set.ids[i]);
-		if (ret)
-			break;
+		ASSERT_TRUE(found, "id_in_test_symbols");
 
-		if (i > 0) {
-			if (!ASSERT_LE(test_set.ids[i - 1], test_set.ids[i], "sort_check"))
-				return;
-		}
+		if (i > 0)
+			ASSERT_LE(test_set.ids[i - 1], test_set.ids[i], "sort_check");
 	}
+
+out:
+	btf__free(btf);
 }
-- 
2.54.0

[PATCH bpf-next v1 3/4] selftests/bpf: Fix resolve_btfids test reads of BTF ID sets in PIE builds

[Ihor Solodrai]

TL;DR

On aarch64 with gcc toolchain, when test_progs is linked as a PIE,
reads of BTF ID array by C name return garbage because the GNU
assembler on aarch64 unconditionally folds .local symbol references
into section+addend form, and GOT slots cannot carry an addend per the
AArch64 ELF spec.

Fix by marking the test's BTF ID objects with hidden visibility, which
makes gcc emit a direct access that bypasses the GOT entirely.

Details below.

The subsequent patches adding kfunc checks to resolve_btfids test may
cause test failures on aarch64 / gcc-15:

  test_resolve_btfids:FAIL:kfunc_set_flags  actual 13 != expected 1
  test_resolve_btfids:FAIL:kfunc_set_cnt    actual 0  != expected 4

The test defines its BTF ID sets with the same macros as the kernel
and reads them back directly by C name (in the same way as the kernel
code does).

test_kfunc_set is a .local symbol emitted into .BTF_ids by inline asm
and declared to the compiler as a plain default-visibility
extern, that is:
    extern struct btf_id_set8 test_kfunc_set;

Depending on the build environment, test_progs may be linked as a
position-independent executable (for example, gcc defaults to -fpie
[1]). In a PIE, taking the address of a default-visibility extern is
routed through the GOT (Global Offset Table) [2].

The GNU assembler's adjust_reloc_syms() pass (gas/write.c [3])
replaces references to local symbols with the corresponding section
symbol, folding the symbol's offset into the relocation addend.  On
aarch64 this conversion is unconditional: tc_fix_adjustable() is
defined to 1 for all fixups (gas/config/tc-aarch64.h [4]), so even
GOT-generating relocations are subject to it.  The resulting object
file therefore contains:

  R_AARCH64_ADR_GOT_PAGE      .BTF_ids + 0x54
  R_AARCH64_LD64_GOT_LO12_NC  .BTF_ids + 0x54

However, the AArch64 ELF specification mandates that GOT-generating
relocations must have a zero addend [5].  The +0x54 is therefore not
honored: the linker creates a GOT slot pointing at the .BTF_ids base,
and every access through that slot reads offset 0 instead of 0x54.

This is purely a read-side problem, specific to the PIE test binary on
aarch64 with gcc toolchain. resolve_btfids patches the set header
correctly and the .BTF_ids bytes in test_progs are correct. vmlinux is
unaffected because it is built with -fno-PIE [6] and reaches .BTF_ids
with direct, addend-preserving relocations rather than the GOT. clang
is unaffected because LLVM's assembler retains the original symbol for
GOT relocations instead of converting to section+addend [7].

To mitigate this issue, mark the test's .local BTF ID objects
(test_list_local and test_set) hidden with a visibility pragma so that
gcc treats them as non-interposable and emits a direct access instead
of a GOT load. test_list_global is .globl, which the assembler does not
fold into section+addend, so it is left at default visibility. This
keeps the natural by-name access, works in both PIE and non-PIE builds,
and needs no change to the BTF_ID macros or resolve_btfids.

[1] https://gcc.gnu.org/onlinedocs/gnat_ugn/Position-Independent-Executable-PIE-Enabled-by-Default-on-Linux.html
[2] https://gcc.gnu.org/wiki/Visibility
[3] https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gas/write.c#l922
[4] https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gas/config/tc-aarch64.h#l279
[5] https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#5733relocation-operations
[6] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Makefile?h=v7.1-rc6#n593
[7] https://github.com/llvm/llvm-project/blob/4b3bc46d1d794b8ed78b75ccd35a6cc30235bf31/llvm/lib/MC/ELFObjectWriter.cpp#L1213-L1224

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 .../selftests/bpf/prog_tests/resolve_btfids.c | 29 +++++++++++++++----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index e549780697c7..6bcadee50bb8 100644
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -34,6 +34,24 @@ asm (
 ".balign 4, 0;                            \n"
 ".popsection;                             \n");
 
+/*
+ * test_list_local and test_set are .local symbols placed in .BTF_ids by
+ * inline asm, and are read here directly by C name. To the compiler they
+ * are plain, default-visibility extern objects.
+ *
+ * When test_progs is linked as a position-independent executable (PIE),
+ * taking the address of such an extern is routed through the GOT. The
+ * GNU assembler on aarch64 unconditionally converts references to .local
+ * symbols into section + addend form (".BTF_ids + <offset>"), but a GOT
+ * slot cannot carry an addend (the AArch64 ELF spec mandates zero), so
+ * the linker resolves it to the .BTF_ids base.
+ *
+ * Mark them hidden so the compiler treats them as non-interposable and
+ * emits a direct, addend-preserving PC-relative access instead of a GOT
+ * load, in both PIE and non-PIE builds. test_list_global is .globl and
+ * not affected, so it is left at default visibility.
+ */
+#pragma GCC visibility push(hidden)
 BTF_ID_LIST(test_list_local)
 BTF_ID_UNUSED
 BTF_ID(typedef, S)
@@ -43,24 +61,25 @@ BTF_ID(struct,  S)
 BTF_ID(union,   U)
 BTF_ID(func,    func)
 
-extern __u32 test_list_global[];
-BTF_ID_LIST_GLOBAL(test_list_global, 1)
-BTF_ID_UNUSED
+BTF_SET_START(test_set)
 BTF_ID(typedef, S)
 BTF_ID(typedef, T)
 BTF_ID(typedef, U)
 BTF_ID(struct,  S)
 BTF_ID(union,   U)
 BTF_ID(func,    func)
+BTF_SET_END(test_set)
+#pragma GCC visibility pop
 
-BTF_SET_START(test_set)
+extern __u32 test_list_global[];
+BTF_ID_LIST_GLOBAL(test_list_global, 1)
+BTF_ID_UNUSED
 BTF_ID(typedef, S)
 BTF_ID(typedef, T)
 BTF_ID(typedef, U)
 BTF_ID(struct,  S)
 BTF_ID(union,   U)
 BTF_ID(func,    func)
-BTF_SET_END(test_set)
 
 static int
 __resolve_symbol(struct btf *btf, int type_id)
-- 
2.54.0

[PATCH bpf-next v1 4/4] selftests/bpf: Add kfunc set test to resolve_btfids

[Ihor Solodrai]

Extend the resolve_btfids selftest to cover kfunc sets defined with
BTF_KFUNCS_START/BTF_KFUNCS_END.

The test verifies that resolve_btfids correctly processes BTF_ID_FLAGS,
resolves function IDs, and checks the kfunc set is sorted.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 .../selftests/bpf/prog_tests/resolve_btfids.c | 63 ++++++++++++++++---
 tools/testing/selftests/bpf/progs/btf_data.c  | 10 +++
 2 files changed, 66 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index 6bcadee50bb8..65ede3ac5845 100644
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -12,6 +12,10 @@
 
 #define BTF_DATA_FILE "resolve_btfids.test.o.BTF"
 
+#ifndef KF_FASTCALL
+#define KF_FASTCALL (1 << 12)
+#endif
+
 struct symbol {
 	const char	*name;
 	int		 type;
@@ -28,6 +32,17 @@ struct symbol test_symbols[] = {
 	{ "func",    BTF_KIND_FUNC,    -1 },
 };
 
+struct kfunc_symbol {
+	const char	*name;
+	s32		 id;
+	u32		 flags;
+};
+
+static struct kfunc_symbol kfunc_symbols[] = {
+	{ "kfunc_a", -1, 0 },
+	{ "kfunc_b", -1, KF_FASTCALL },
+};
+
 /* Align the .BTF_ids section to 4 bytes */
 asm (
 ".pushsection " BTF_IDS_SECTION " ,\"a\"; \n"
@@ -35,9 +50,9 @@ asm (
 ".popsection;                             \n");
 
 /*
- * test_list_local and test_set are .local symbols placed in .BTF_ids by
- * inline asm, and are read here directly by C name. To the compiler they
- * are plain, default-visibility extern objects.
+ * test_list_local, test_set and test_kfunc_set are .local symbols placed
+ * in .BTF_ids by inline asm, and are read here directly by C name. To the
+ * compiler they are plain, default-visibility extern objects.
  *
  * When test_progs is linked as a position-independent executable (PIE),
  * taking the address of such an extern is routed through the GOT. The
@@ -69,6 +84,11 @@ BTF_ID(struct,  S)
 BTF_ID(union,   U)
 BTF_ID(func,    func)
 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_KFUNCS_END(test_kfunc_set)
 #pragma GCC visibility pop
 
 extern __u32 test_list_global[];
@@ -92,6 +112,8 @@ __resolve_symbol(struct btf *btf, int type_id)
 	if (!ASSERT_OK_PTR(type, "btf__type_by_id"))
 		return -1;
 
+	str = btf__name_by_offset(btf, type->name_off);
+
 	for (i = 0; i < ARRAY_SIZE(test_symbols); i++) {
 		if (test_symbols[i].id >= 0)
 			continue;
@@ -99,14 +121,20 @@ __resolve_symbol(struct btf *btf, int type_id)
 		if (BTF_INFO_KIND(type->info) != test_symbols[i].type)
 			continue;
 
-		str = btf__name_by_offset(btf, type->name_off);
-		if (!ASSERT_OK_PTR(str, "btf__name_by_offset"))
-			return -1;
-
 		if (!strcmp(str, test_symbols[i].name))
 			test_symbols[i].id = type_id;
 	}
 
+	if (!btf_is_func(type))
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(kfunc_symbols); i++) {
+		if (kfunc_symbols[i].id >= 0)
+			continue;
+		if (!strcmp(str, kfunc_symbols[i].name))
+			kfunc_symbols[i].id = type_id;
+	}
+
 	return 0;
 }
 
@@ -161,6 +189,27 @@ void test_resolve_btfids(void)
 			ASSERT_LE(test_set.ids[i - 1], test_set.ids[i], "sort_check");
 	}
 
+	/* Check BTF_KFUNCS_START(test_kfunc_set) */
+	ASSERT_EQ(test_kfunc_set.flags, BTF_SET8_KFUNCS, "kfunc_set_flags");
+	ASSERT_EQ(test_kfunc_set.cnt, ARRAY_SIZE(kfunc_symbols), "kfunc_set_cnt");
+
+	for (i = 0; i < test_kfunc_set.cnt; i++) {
+		for (j = 0; j < ARRAY_SIZE(kfunc_symbols); j++) {
+			if (kfunc_symbols[j].id == (s32)test_kfunc_set.pairs[i].id) {
+				ASSERT_EQ(test_kfunc_set.pairs[i].flags,
+					  kfunc_symbols[j].flags, "kfunc_flags_check");
+				break;
+			}
+		}
+
+		ASSERT_TRUE(j < ARRAY_SIZE(kfunc_symbols), "kfunc_id_found");
+
+		if (i > 0) {
+			ASSERT_LE(test_kfunc_set.pairs[i - 1].id,
+				  test_kfunc_set.pairs[i].id, "kfunc_sort_check");
+		}
+	}
+
 out:
 	btf__free(btf);
 }
diff --git a/tools/testing/selftests/bpf/progs/btf_data.c b/tools/testing/selftests/bpf/progs/btf_data.c
index baa525275bde..8587658012c3 100644
--- a/tools/testing/selftests/bpf/progs/btf_data.c
+++ b/tools/testing/selftests/bpf/progs/btf_data.c
@@ -48,3 +48,13 @@ int func(struct root_struct *root)
 {
 	return 0;
 }
+
+int kfunc_a(struct root_struct *root)
+{
+	return 0;
+}
+
+int kfunc_b(struct root_struct *root)
+{
+	return 0;
+}
-- 
2.54.0