selftests/bpf: Add test for sleepable program tailcalls

Adding test that makes sure we can't mix sleepable and non-sleepable
bpf programs in the BPF_MAP_TYPE_PROG_ARRAY map and that we can do
tail call in the sleepable program.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260130081208.1130204-3-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: olsajiri

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

@@ -8,6 +8,7 @@
 #include "tailcall_freplace.skel.h"
 #include "tc_bpf2bpf.skel.h"
 #include "tailcall_fail.skel.h"
+#include "tailcall_sleepable.skel.h"
 
 /* test_tailcall_1 checks basic functionality by patching multiple locations
  * in a single program for a single tail call slot with nop->jmp, jmp->nop
@@ -1653,6 +1654,77 @@ static void test_tailcall_failure()
 	RUN_TESTS(tailcall_fail);
 }
 
+noinline void uprobe_sleepable_trigger(void)
+{
+	asm volatile ("");
+}
+
+static void test_tailcall_sleepable(void)
+{
+	LIBBPF_OPTS(bpf_uprobe_opts, opts);
+	struct tailcall_sleepable *skel;
+	int prog_fd, map_fd;
+	int err, key;
+
+	skel = tailcall_sleepable__open();
+	if (!ASSERT_OK_PTR(skel, "tailcall_sleepable__open"))
+		return;
+
+	/*
+	 * Test that we can't load uprobe_normal and uprobe_sleepable_1,
+	 * because they share tailcall map.
+	 */
+	bpf_program__set_autoload(skel->progs.uprobe_normal, true);
+	bpf_program__set_autoload(skel->progs.uprobe_sleepable_1, true);
+
+	err = tailcall_sleepable__load(skel);
+	if (!ASSERT_ERR(err, "tailcall_sleepable__load"))
+		goto out;
+
+	tailcall_sleepable__destroy(skel);
+
+	/*
+	 * Test that we can tail call from sleepable to sleepable program.
+	 */
+	skel = tailcall_sleepable__open();
+	if (!ASSERT_OK_PTR(skel, "tailcall_sleepable__open"))
+		return;
+
+	bpf_program__set_autoload(skel->progs.uprobe_sleepable_1, true);
+	bpf_program__set_autoload(skel->progs.uprobe_sleepable_2, true);
+
+	err = tailcall_sleepable__load(skel);
+	if (!ASSERT_OK(err, "tailcall_sleepable__load"))
+		goto out;
+
+	/* Add sleepable uprobe_sleepable_2 to jmp_table[0]. */
+	key = 0;
+	prog_fd = bpf_program__fd(skel->progs.uprobe_sleepable_2);
+	map_fd = bpf_map__fd(skel->maps.jmp_table);
+	err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY);
+	if (!ASSERT_OK(err, "update jmp_table"))
+		goto out;
+
+	skel->bss->my_pid = getpid();
+
+	/* Attach uprobe_sleepable_1 to uprobe_sleepable_trigger and hit it.  */
+	opts.func_name = "uprobe_sleepable_trigger";
+	skel->links.uprobe_sleepable_1 = bpf_program__attach_uprobe_opts(
+						skel->progs.uprobe_sleepable_1,
+						-1,
+						"/proc/self/exe",
+						0 /* offset */,
+						&opts);
+	if (!ASSERT_OK_PTR(skel->links.uprobe_sleepable_1, "bpf_program__attach_uprobe_opts"))
+		goto out;
+
+	uprobe_sleepable_trigger();
+	ASSERT_EQ(skel->bss->executed, 1, "executed");
+
+out:
+	tailcall_sleepable__destroy(skel);
+}
+
 void test_tailcalls(void)
 {
 	if (test__start_subtest("tailcall_1"))
@@ -1707,4 +1779,6 @@ void test_tailcalls(void)
 		test_tailcall_bpf2bpf_freplace();
 	if (test__start_subtest("tailcall_failure"))
 		test_tailcall_failure();
+	if (test__start_subtest("tailcall_sleepable"))
+		test_tailcall_sleepable();
 }

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

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "bpf_test_utils.h"
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__array(values, void (void));
+} jmp_table SEC(".maps");
+
+SEC("?uprobe")
+int uprobe_normal(void *ctx)
+{
+	bpf_tail_call_static(ctx, &jmp_table, 0);
+	return 0;
+}
+
+SEC("?uprobe.s")
+int uprobe_sleepable_1(void *ctx)
+{
+	bpf_tail_call_static(ctx, &jmp_table, 0);
+	return 0;
+}
+
+int executed = 0;
+int my_pid = 0;
+
+SEC("?uprobe.s")
+int uprobe_sleepable_2(void *ctx)
+{
+	int pid = bpf_get_current_pid_tgid() >> 32;
+
+	if (pid != my_pid)
+		return 0;
+
+	executed++;
+	return 0;
+}
+
+char __license[] SEC("license") = "GPL";