Merge branch 'modernize-resolve_btfids-selftest'

Ihor Solodrai says:

====================
Modernize resolve_btfids selftest

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/
---

v1->v2:
  * add another kfunc set in reverse order and check_kfunc_set()
    helper to ensure proper testing of BTF ID sort (Eduard, patch #4)
  * nit: restore a dropped break (Eduard, patch #2)
v1: https://lore.kernel.org/bpf/20260617210619.1562858-1-ihor.solodrai@linux.dev/

v0->v1:
  * 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
====================

Link: https://patch.msgid.link/20260624005546.1818483-1-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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

tools/testing/selftests/bpf/prog_tests/resolve_btfids.c

@@ -10,7 +10,11 @@
 #include <linux/btf_ids.h>
 #include "test_progs.h"
 
-static int duration;
+#define BTF_DATA_FILE "resolve_btfids.test.o.BTF"
+
+#ifndef KF_FASTCALL
+#define KF_FASTCALL (1 << 12)
+#endif
 
 struct symbol {
 	const char	*name;
@@ -28,12 +32,41 @@ 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"
 ".balign 4, 0;                            \n"
 ".popsection;                             \n");
 
+/*
+ * 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
+ * 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)
@@ -43,16 +76,6 @@ 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_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_START(test_set)
 BTF_ID(typedef, S)
 BTF_ID(typedef, T)
@@ -62,6 +85,31 @@ 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)
+
+/*
+ * Same kfuncs in reverse declaration order, so resolve_btfids has to
+ * actually sort at least one of the two sets.
+ */
+BTF_KFUNCS_START(test_kfunc_set_rev)
+BTF_ID_FLAGS(func, kfunc_b, KF_FASTCALL)
+BTF_ID_FLAGS(func, kfunc_a)
+BTF_KFUNCS_END(test_kfunc_set_rev)
+#pragma GCC visibility pop
+
+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)
+
 static int
 __resolve_symbol(struct btf *btf, int type_id)
 {
@@ -70,10 +118,10 @@ __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;
-	}
+
+	str = btf__name_by_offset(btf, type->name_off);
 
 	for (i = 0; i < ARRAY_SIZE(test_symbols); i++) {
 		if (test_symbols[i].id >= 0)
@@ -82,64 +130,80 @@ __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 (!str) {
-			PRINT_FAIL("Failed to get name for BTF ID %d\n", type_id);
-			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;
 }
 
-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;
 }
 
+static void check_kfunc_set(struct btf_id_set8 *set)
+{
+	unsigned int i, j;
+
+	ASSERT_EQ(set->flags, BTF_SET8_KFUNCS, "kfunc_set_flags");
+	ASSERT_EQ(set->cnt, ARRAY_SIZE(kfunc_symbols), "kfunc_set_cnt");
+
+	for (i = 0; i < set->cnt; i++) {
+		for (j = 0; j < ARRAY_SIZE(kfunc_symbols); j++) {
+			if (kfunc_symbols[j].id == (s32)set->pairs[i].id) {
+				ASSERT_EQ(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(set->pairs[i - 1].id,
+				  set->pairs[i].id, "kfunc_sort_check");
+		}
+	}
+}
+
 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 +217,16 @@ 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)
+		if (!ASSERT_TRUE(found, "id_in_test_symbols"))
 			break;
 
-		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");
 	}
+
+	check_kfunc_set(&test_kfunc_set);
+	check_kfunc_set(&test_kfunc_set_rev);
+
+out:
+	btf__free(btf);
 }

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;
+}