bpf_experimental.h and ../bpf_testmod/bpf_testmod_kfunc.h are both
including vmlinux.h, which is not compatible with including time.h
or bpf_tcp_helpers.h.

So keep sleepable tests in a separate bpf source file.

The first correct test is run twice for convenience:
- first through RUN_TESTS
- then we ensure that the timer was actually executed, in a manual
  load/attach/run

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

---

changes in v6:
- use of new _init API with BPF_F_TIMER_SLEEPABLE

changes in v5b:
- do not use SEC(syscall) as they are run in a sleepable context
  already
- duplicate test_call_sleepable() so we can test if the callback gets
  called

changes in v5:
- keep sleepable test separate

new in v4
---
 tools/testing/selftests/bpf/bpf_experimental.h     |   5 +
 .../selftests/bpf/bpf_testmod/bpf_testmod.c        |   5 +
 .../selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h  |   1 +
 tools/testing/selftests/bpf/prog_tests/timer.c     |  34 ++++
 .../testing/selftests/bpf/progs/timer_sleepable.c  | 213 +++++++++++++++++++++
 5 files changed, 258 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index a5b9df38c162..06ed98b3bc51 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -459,4 +459,9 @@ extern int bpf_iter_css_new(struct bpf_iter_css *it,
 extern struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it) __weak __ksym;
 extern void bpf_iter_css_destroy(struct bpf_iter_css *it) __weak __ksym;
 
+extern int bpf_timer_set_sleepable_cb_impl(struct bpf_timer *timer,
+		int (callback_fn)(void *map, int *key, struct bpf_timer *timer),
+		void *aux__ign) __ksym;
+#define bpf_timer_set_sleepable_cb(timer, cb) \
+	bpf_timer_set_sleepable_cb_impl(timer, cb, NULL)
 #endif
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 39ad96a18123..eb2b78552ca2 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -494,6 +494,10 @@ __bpf_kfunc static u32 bpf_kfunc_call_test_static_unused_arg(u32 arg, u32 unused
 	return arg;
 }
 
+__bpf_kfunc void bpf_kfunc_call_test_sleepable(void)
+{
+}
+
 BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
@@ -520,6 +524,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_ref, KF_TRUSTED_ARGS | KF_RCU)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_destructive, KF_DESTRUCTIVE)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_static_unused_arg)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_offset)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_sleepable, KF_SLEEPABLE)
 BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids)
 
 static int bpf_testmod_ops_init(struct btf *btf)
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h
index 7c664dd61059..ce5cd763561c 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h
@@ -96,6 +96,7 @@ void bpf_kfunc_call_test_pass2(struct prog_test_pass2 *p) __ksym;
 void bpf_kfunc_call_test_mem_len_fail2(__u64 *mem, int len) __ksym;
 
 void bpf_kfunc_call_test_destructive(void) __ksym;
+void bpf_kfunc_call_test_sleepable(void) __ksym;
 
 void bpf_kfunc_call_test_offset(struct prog_test_ref_kfunc *p);
 struct prog_test_member *bpf_kfunc_call_memb_acquire(void);
diff --git a/tools/testing/selftests/bpf/prog_tests/timer.c b/tools/testing/selftests/bpf/prog_tests/timer.c
index d66687f1ee6a..c6c7c623b31c 100644
--- a/tools/testing/selftests/bpf/prog_tests/timer.c
+++ b/tools/testing/selftests/bpf/prog_tests/timer.c
@@ -3,6 +3,7 @@
 #include <test_progs.h>
 #include "timer.skel.h"
 #include "timer_failure.skel.h"
+#include "timer_sleepable.skel.h"
 
 #define NUM_THR 8
 
@@ -95,3 +96,36 @@ void serial_test_timer(void)
 
 	RUN_TESTS(timer_failure);
 }
+
+/* isolate sleepable tests from main timer tests
+ * because if test_timer fails, it spews the console
+ * with 10000 * 5 "spin_lock_thread:PASS:test_run_opts retval 0 nsec"
+ */
+void serial_test_sleepable_timer(void)
+{
+	struct timer_sleepable *timer_sleepable_skel = NULL;
+	int err, prog_fd;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+
+	RUN_TESTS(timer_sleepable);
+
+	/* re-run the success test to check if the timer was actually executed */
+
+	timer_sleepable_skel = timer_sleepable__open_and_load();
+	if (!ASSERT_OK_PTR(timer_sleepable_skel, "timer_sleepable_skel_load"))
+		return;
+
+	err = timer_sleepable__attach(timer_sleepable_skel);
+	if (!ASSERT_OK(err, "timer_sleepable_attach"))
+		return;
+
+	prog_fd = bpf_program__fd(timer_sleepable_skel->progs.test_syscall_sleepable);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(topts.retval, 0, "test_run");
+
+	usleep(50); /* 10 usecs should be enough, but give it extra */
+
+	ASSERT_EQ(timer_sleepable_skel->bss->ok_sleepable, 1, "ok_sleepable");
+}
diff --git a/tools/testing/selftests/bpf/progs/timer_sleepable.c b/tools/testing/selftests/bpf/progs/timer_sleepable.c
new file mode 100644
index 000000000000..fc7829d8b6c4
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/timer_sleepable.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook
+ * Copyright (c) 2024 Benjamin Tissoires
+ */
+
+#include "bpf_experimental.h"
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "../bpf_testmod/bpf_testmod_kfunc.h"
+
+char _license[] SEC("license") = "GPL";
+
+#define CLOCK_MONOTONIC 1
+
+struct elem {
+	struct bpf_timer t;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 3);
+	__type(key, int);
+	__type(value, struct elem);
+} timer_map SEC(".maps");
+
+__u32 ok_sleepable;
+
+/* callback for sleepable timer */
+static int timer_cb_sleepable(void *map, int *key, struct bpf_timer *timer)
+{
+	bpf_kfunc_call_test_sleepable();
+	ok_sleepable |= (1 << *key);
+	return 0;
+}
+
+SEC("tc")
+/* check that calling bpf_timer_start() with BPF_F_TIMER_SLEEPABLE on a sleepable
+ * callback works
+ */
+__retval(0)
+long test_call_sleepable(void *ctx)
+{
+	int key = 0;
+	struct bpf_timer *timer;
+
+	if (ok_sleepable & 1)
+		return -1;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (timer) {
+		if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE) != 0)
+			return -2;
+		bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable);
+		if (bpf_timer_start(timer, 0, 0))
+			return -3;
+	} else {
+		return -4;
+	}
+
+	return 0;
+}
+
+SEC("syscall")
+/* check that calling bpf_timer_start() with BPF_F_TIMER_SLEEPABLE on a sleepable
+ * callback works.
+ */
+__retval(0)
+long test_syscall_sleepable(void *ctx)
+{
+	int key = 0;
+	struct bpf_timer *timer;
+
+	if (ok_sleepable & 1)
+		return -1;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (timer) {
+		if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE) != 0)
+			return -2;
+		bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable);
+		if (bpf_timer_start(timer, 0, 0))
+			return -3;
+	} else {
+		return -4;
+	}
+
+	return 0;
+}
+
+SEC("?tc")
+__log_level(2)
+__failure
+/* check that bpf_timer_set_callback() can not be called with a
+ * sleepable callback
+ */
+__msg("mark_precise: frame0: regs=r1 stack= before")
+__msg(": (85) call bpf_kfunc_call_test_sleepable#") /* anchor message */
+__msg("program must be sleepable to call sleepable kfunc bpf_kfunc_call_test_sleepable")
+long test_non_sleepable_sleepable_callback(void *ctx)
+{
+	int key = 0;
+	struct bpf_timer *timer;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (timer) {
+		bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE);
+		bpf_timer_set_callback(timer, timer_cb_sleepable);
+		bpf_timer_start(timer, 0, 0);
+	}
+
+	return 0;
+}
+
+SEC("tc")
+/* check that calling bpf_timer_set_sleepable_cb() without a sleepable timer
+ * initialized with BPF_F_TIMER_SLEEPABLE on a sleepable
+ * callback is returning -EINVAL
+ */
+__retval(3)
+long test_call_sleepable_missing_flag(void *ctx)
+{
+	int key = 1;
+	struct bpf_timer *timer;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (!timer)
+		return 1;
+
+	if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC))
+		return 2;
+
+	if (bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable))
+		return 3;
+
+	return bpf_timer_start(timer, 0, 0);
+}
+
+SEC("tc")
+/* check that calling bpf_timer_start() with a delay on a sleepable
+ * callback is returning -EINVAL
+ */
+__retval(-22)
+long test_call_sleepable_delay(void *ctx)
+{
+	int key = 2;
+	struct bpf_timer *timer;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (!timer)
+		return 1;
+
+	if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
+		return 2;
+
+	if (bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable))
+		return 3;
+
+	return bpf_timer_start(timer, 1, 0);
+}
+
+SEC("?tc")
+__log_level(2)
+__failure
+/* check that the first argument of bpf_timer_set_callback()
+ * is a correct bpf_timer pointer.
+ */
+__msg("mark_precise: frame0: regs=r1 stack= before")
+__msg(": (85) call bpf_timer_set_sleepable_cb_impl#") /* anchor message */
+__msg("arg#0 doesn't point to a map value")
+long test_wrong_pointer(void *ctx)
+{
+	int key = 0;
+	struct bpf_timer *timer;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (!timer)
+		return 1;
+
+	if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
+		return 2;
+
+	if (bpf_timer_set_sleepable_cb((void *)&timer, timer_cb_sleepable))
+		return 3;
+
+	return -22;
+}
+
+SEC("?tc")
+__log_level(2)
+__failure
+/* check that the first argument of bpf_timer_set_callback()
+ * is a correct bpf_timer pointer.
+ */
+__msg("mark_precise: frame0: regs=r1 stack= before")
+__msg(": (85) call bpf_timer_set_sleepable_cb_impl#") /* anchor message */
+__msg("off 1 doesn't point to 'struct bpf_timer' that is at 0")
+long test_wrong_pointer_offset(void *ctx)
+{
+	int key = 0;
+	struct bpf_timer *timer;
+
+	timer = bpf_map_lookup_elem(&timer_map, &key);
+	if (!timer)
+		return 1;
+
+	if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
+		return 2;
+
+	if (bpf_timer_set_sleepable_cb((void *)timer + 1, timer_cb_sleepable))
+		return 3;
+
+	return -22;
+}

-- 
2.44.0

On Mon, 2024-04-08 at 10:09 +0200, Benjamin Tissoires wrote:
> bpf_experimental.h and ../bpf_testmod/bpf_testmod_kfunc.h are both
> including vmlinux.h, which is not compatible with including time.h
> or bpf_tcp_helpers.h.
> 
> So keep sleepable tests in a separate bpf source file.
> 
> The first correct test is run twice for convenience:
> - first through RUN_TESTS
> - then we ensure that the timer was actually executed, in a manual
>   load/attach/run
> 
> Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
> 
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
(With a few nitpicks)

> diff --git a/tools/testing/selftests/bpf/prog_tests/timer.c b/tools/testing/selftests/bpf/prog_tests/timer.c
> index d66687f1ee6a..c6c7c623b31c 100644
> --- a/tools/testing/selftests/bpf/prog_tests/timer.c
> +++ b/tools/testing/selftests/bpf/prog_tests/timer.c

[...]

> +void serial_test_sleepable_timer(void)
> +{
> +	struct timer_sleepable *timer_sleepable_skel = NULL;
> +	int err, prog_fd;
> +
> +	LIBBPF_OPTS(bpf_test_run_opts, topts);
> +
> +	RUN_TESTS(timer_sleepable);
> +
> +	/* re-run the success test to check if the timer was actually executed */
> +
> +	timer_sleepable_skel = timer_sleepable__open_and_load();
> +	if (!ASSERT_OK_PTR(timer_sleepable_skel, "timer_sleepable_skel_load"))
> +		return;
> +
> +	err = timer_sleepable__attach(timer_sleepable_skel);
> +	if (!ASSERT_OK(err, "timer_sleepable_attach"))
> +		return;

Nit: this should call timer_sleepable__destroy();

> +
> +	prog_fd = bpf_program__fd(timer_sleepable_skel->progs.test_syscall_sleepable);
> +	err = bpf_prog_test_run_opts(prog_fd, &topts);
> +	ASSERT_OK(err, "test_run");
> +	ASSERT_EQ(topts.retval, 0, "test_run");
> +
> +	usleep(50); /* 10 usecs should be enough, but give it extra */
> +
> +	ASSERT_EQ(timer_sleepable_skel->bss->ok_sleepable, 1, "ok_sleepable");

Nit: same as above.

> +}
> diff --git a/tools/testing/selftests/bpf/progs/timer_sleepable.c b/tools/testing/selftests/bpf/progs/timer_sleepable.c
> new file mode 100644
> index 000000000000..fc7829d8b6c4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/timer_sleepable.c

[...]

> +SEC("tc")
> +/* check that calling bpf_timer_start() with BPF_F_TIMER_SLEEPABLE on a sleepable
> + * callback works
> + */
> +__retval(0)
> +long test_call_sleepable(void *ctx)
> +{
> +	int key = 0;
> +	struct bpf_timer *timer;
> +
> +	if (ok_sleepable & 1)
> +		return -1;
> +
> +	timer = bpf_map_lookup_elem(&timer_map, &key);
> +	if (timer) {
> +		if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE) != 0)
> +			return -2;
> +		bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable);
> +		if (bpf_timer_start(timer, 0, 0))
> +			return -3;
> +	} else {
> +		return -4;
> +	}
> +
> +	return 0;
> +}
> +
> +SEC("syscall")
> +/* check that calling bpf_timer_start() with BPF_F_TIMER_SLEEPABLE on a sleepable
> + * callback works.
> + */
> +__retval(0)
> +long test_syscall_sleepable(void *ctx)
> +{

Nit: the body of this function is the same as in test_call_sleepable(),
     maybe factor it out as an auxiliary static function?
     (also, should these tests use different 'key' ?)

> +	int key = 0;
> +	struct bpf_timer *timer;
> +
> +	if (ok_sleepable & 1)
> +		return -1;
> +
> +	timer = bpf_map_lookup_elem(&timer_map, &key);
> +	if (timer) {
> +		if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE) != 0)
> +			return -2;
> +		bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable);
> +		if (bpf_timer_start(timer, 0, 0))
> +			return -3;
> +	} else {
> +		return -4;
> +	}
> +
> +	return 0;
> +}

[...]

> +SEC("tc")
> +/* check that calling bpf_timer_start() with a delay on a sleepable
> + * callback is returning -EINVAL
> + */
> +__retval(-22)
> +long test_call_sleepable_delay(void *ctx)
> +{
> +	int key = 2;
> +	struct bpf_timer *timer;
> +
> +	timer = bpf_map_lookup_elem(&timer_map, &key);
> +	if (!timer)
> +		return 1;
> +
> +	if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
> +		return 2;
> +
> +	if (bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable))
> +		return 3;
> +
> +	return bpf_timer_start(timer, 1, 0);

Q: should verifier statically check that 3rd parameter is zero for sleepable timers?
  (same question for call to bpf_timer_set_sleepable_cb() with non-sleepable map)

[...]

On Mon, Apr 8, 2024 at 4:01 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> > +SEC("tc")
> > +/* check that calling bpf_timer_start() with a delay on a sleepable
> > + * callback is returning -EINVAL
> > + */
> > +__retval(-22)
> > +long test_call_sleepable_delay(void *ctx)
> > +{
> > +     int key = 2;
> > +     struct bpf_timer *timer;
> > +
> > +     timer = bpf_map_lookup_elem(&timer_map, &key);
> > +     if (!timer)
> > +             return 1;
> > +
> > +     if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
> > +             return 2;
> > +
> > +     if (bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable))
> > +             return 3;
> > +
> > +     return bpf_timer_start(timer, 1, 0);
>
> Q: should verifier statically check that 3rd parameter is zero for sleepable timers?
>   (same question for call to bpf_timer_set_sleepable_cb() with non-sleepable map)

It can, but that sounds like more work for the verifier.
Which gives more reasons to use new kfuncs and clean start with bpf_wq.