selftests/bpf: Add tracing multi intersect tests

Adding tracing multi tests for intersecting attached functions.

Using bits from (from 1 to 16 values) to specify (up to 4) attached
programs, and randomly choosing bpf_fentry_test* functions they are
attached to.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-24-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/Makefile

@@ -513,7 +513,8 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
 		linked_vars.skel.h linked_maps.skel.h 			\
 		test_subskeleton.skel.h test_subskeleton_lib.skel.h	\
 		test_usdt.skel.h tracing_multi.skel.h			\
-		tracing_multi_module.skel.h
+		tracing_multi_module.skel.h				\
+		tracing_multi_intersect.skel.h
 
 LSKELS := fexit_sleep.c trace_printk.c trace_vprintk.c map_ptr_kern.c 	\
 	core_kern.c core_kern_overflow.c test_ringbuf.c			\
@@ -541,6 +542,7 @@ xdp_hw_metadata.skel.h-deps := xdp_hw_metadata.bpf.o
 xdp_features.skel.h-deps := xdp_features.bpf.o
 tracing_multi.skel.h-deps := tracing_multi_attach.bpf.o tracing_multi_check.bpf.o
 tracing_multi_module.skel.h-deps := tracing_multi_attach_module.bpf.o tracing_multi_check.bpf.o
+tracing_multi_intersect.skel.h-deps := tracing_multi_intersect_attach.bpf.o tracing_multi_check.bpf.o
 
 LINKED_BPF_OBJS := $(foreach skel,$(LINKED_SKELS),$($(skel)-deps))
 LINKED_BPF_SRCS := $(patsubst %.bpf.o,%.c,$(LINKED_BPF_OBJS))

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

@@ -6,6 +6,7 @@
 #include "bpf/libbpf_internal.h"
 #include "tracing_multi.skel.h"
 #include "tracing_multi_module.skel.h"
+#include "tracing_multi_intersect.skel.h"
 #include "trace_helpers.h"
 
 static const char * const bpf_fentry_test[] = {
@@ -31,6 +32,20 @@ static const char * const bpf_testmod_fentry_test[] = {
 
 #define FUNCS_CNT (ARRAY_SIZE(bpf_fentry_test))
 
+static int get_random_funcs(const char **funcs)
+{
+	int i, cnt = 0;
+
+	for (i = 0; i < FUNCS_CNT; i++) {
+		if (rand() % 2)
+			funcs[cnt++] = bpf_fentry_test[i];
+	}
+	/* we always need at least one.. */
+	if (!cnt)
+		funcs[cnt++] = bpf_fentry_test[rand() % FUNCS_CNT];
+	return cnt;
+}
+
 static int compare(const void *ppa, const void *ppb)
 {
 	const char *pa = *(const char **) ppa;
@@ -341,6 +356,88 @@ static void test_module_link_api_ids(void)
 	free(ids);
 }
 
+static bool is_set(__u32 mask, __u32 bit)
+{
+	return (1 << bit) & mask;
+}
+
+static void __test_intersect(__u32 mask, const struct bpf_program *progs[4], __u64 *test_results[4])
+{
+	LIBBPF_OPTS(bpf_tracing_multi_opts, opts);
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct bpf_link *links[4] = { NULL };
+	const char *funcs[FUNCS_CNT];
+	__u64 expected[4];
+	__u32 *ids, i;
+	int err, cnt;
+
+	/*
+	 * We have 4 programs in progs and the mask bits pick which
+	 * of them gets attached to randomly chosen functions.
+	 */
+	for (i = 0; i < 4; i++) {
+		if (!is_set(mask, i))
+			continue;
+
+		cnt = get_random_funcs(funcs);
+		ids = get_ids(funcs, cnt, NULL);
+		if (!ASSERT_OK_PTR(ids, "get_ids"))
+			goto cleanup;
+
+		opts.ids = ids;
+		opts.cnt = cnt;
+		links[i] = bpf_program__attach_tracing_multi(progs[i], NULL, &opts);
+		free(ids);
+
+		if (!ASSERT_OK_PTR(links[i], "bpf_program__attach_tracing_multi"))
+			goto cleanup;
+
+		expected[i] = *test_results[i] + cnt;
+	}
+
+	err = bpf_prog_test_run_opts(bpf_program__fd(progs[0]), &topts);
+	ASSERT_OK(err, "test_run");
+
+	for (i = 0; i < 4; i++) {
+		if (!is_set(mask, i))
+			continue;
+		ASSERT_EQ(*test_results[i], expected[i], "test_results");
+	}
+
+cleanup:
+	for (i = 0; i < 4; i++)
+		bpf_link__destroy(links[i]);
+}
+
+static void test_intersect(void)
+{
+	struct tracing_multi_intersect *skel;
+	const struct bpf_program *progs[4];
+	__u64 *test_results[4];
+	__u32 i;
+
+	skel = tracing_multi_intersect__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "tracing_multi_intersect__open_and_load"))
+		return;
+
+	skel->bss->pid = getpid();
+
+	progs[0] = skel->progs.fentry_1;
+	progs[1] = skel->progs.fexit_1;
+	progs[2] = skel->progs.fentry_2;
+	progs[3] = skel->progs.fexit_2;
+
+	test_results[0] = &skel->bss->test_result_fentry_1;
+	test_results[1] = &skel->bss->test_result_fexit_1;
+	test_results[2] = &skel->bss->test_result_fentry_2;
+	test_results[3] = &skel->bss->test_result_fexit_2;
+
+	for (i = 1; i < 16; i++)
+		__test_intersect(i, progs, test_results);
+
+	tracing_multi_intersect__destroy(skel);
+}
+
 void test_tracing_multi_test(void)
 {
 #ifndef __x86_64__
@@ -360,4 +457,6 @@ void test_tracing_multi_test(void)
 		test_module_link_api_pattern();
 	if (test__start_subtest("module_link_api_ids"))
 		test_module_link_api_ids();
+	if (test__start_subtest("intersect"))
+		test_intersect();
 }

tools/testing/selftests/bpf/progs/tracing_multi_intersect_attach.c

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+__hidden extern int tracing_multi_arg_check(__u64 *ctx, __u64 *test_result, bool is_return);
+
+__u64 test_result_fentry_1 = 0;
+__u64 test_result_fentry_2 = 0;
+__u64 test_result_fexit_1 = 0;
+__u64 test_result_fexit_2 = 0;
+
+SEC("fentry.multi")
+int BPF_PROG(fentry_1)
+{
+	tracing_multi_arg_check(ctx, &test_result_fentry_1, false);
+	return 0;
+}
+
+SEC("fentry.multi")
+int BPF_PROG(fentry_2)
+{
+	tracing_multi_arg_check(ctx, &test_result_fentry_2, false);
+	return 0;
+}
+
+SEC("fexit.multi")
+int BPF_PROG(fexit_1)
+{
+	tracing_multi_arg_check(ctx, &test_result_fexit_1, true);
+	return 0;
+}
+
+SEC("fexit.multi")
+int BPF_PROG(fexit_2)
+{
+	tracing_multi_arg_check(ctx, &test_result_fexit_2, true);
+	return 0;
+}