[PATCH v4 bpf-next 0/4] tracing/probe: Add PERF_EVENT_IOC_QUERY_PROBE

[PATCH v4 bpf-next 0/4] tracing/probe: Add PERF_EVENT_IOC_QUERY_PROBE

[Daniel Xu]

It's useful to know [uk]probe's nmissed and nhit stats. For example with
tracing tools, it's important to know when events may have been lost.
debugfs currently exposes a control file to get this information, but
it is not compatible with probes registered with the perf API.

While bpf programs may be able to manually count nhit, there is no way
to gather nmissed. In other words, it is currently not possible to
retrieve information about FD-based probes.

This patch adds a new ioctl that lets users query nmissed (as well as
nhit for completeness). We currently only add support for [uk]probes
but leave the possibility open for other probes like tracepoint.

v3 -> v4:
- Make kernel code set size field on ioctl arg
- Update selftests to check size field
- Remove unnecessary function stubs

v2 -> v3:
- Introduce bpf_link_type and associated getter to track underlying link
  types
- Add back size field in perf_event_query_probe for forward/backwards
  compat
- Remove NULL checks, fix typos

v1 -> v2:
- More descriptive cover letter
- Make API more generic and support uprobes as well
- Use casters/getters for libbpf instead of single getter
- Fix typos
- Remove size field from ioctl struct
- Split out libbpf.h sync to tools dir to separate commit

Daniel Xu (4):
  tracing/probe: Add PERF_EVENT_IOC_QUERY_PROBE ioctl
  libbpf: Add helpers to extract perf fd from bpf_link
  tracing/probe: Sync perf_event.h to tools
  tracing/probe: Add self test for PERF_EVENT_IOC_QUERY_PROBE

 include/linux/trace_events.h                  |   2 +
 include/uapi/linux/perf_event.h               |  23 ++++
 kernel/events/core.c                          |  20 +++
 kernel/trace/trace_kprobe.c                   |  25 ++++
 kernel/trace/trace_uprobe.c                   |  25 ++++
 tools/include/uapi/linux/perf_event.h         |  23 ++++
 tools/lib/bpf/libbpf.c                        |  21 ++++
 tools/lib/bpf/libbpf.h                        |  13 ++
 tools/lib/bpf/libbpf.map                      |   3 +
 .../selftests/bpf/prog_tests/attach_probe.c   | 115 ++++++++++++++++++
 10 files changed, 270 insertions(+)

-- 
2.21.0

[PATCH v4 bpf-next 1/4] tracing/probe: Add PERF_EVENT_IOC_QUERY_PROBE ioctl

[Daniel Xu]

It's useful to know [uk]probe's nmissed and nhit stats. For example with
tracing tools, it's important to know when events may have been lost.
debugfs currently exposes a control file to get this information, but
it is not compatible with probes registered with the perf API.

While bpf programs may be able to manually count nhit, there is no way
to gather nmissed. In other words, it is currently not possible to
retrieve information about FD-based probes.

This patch adds a new ioctl that lets users query nmissed (as well as
nhit for completeness). We currently only add support for [uk]probes
but leave the possibility open for other probes like tracepoint.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 include/linux/trace_events.h    |  2 ++
 include/uapi/linux/perf_event.h | 23 +++++++++++++++++++++++
 kernel/events/core.c            | 20 ++++++++++++++++++++
 kernel/trace/trace_kprobe.c     | 25 +++++++++++++++++++++++++
 kernel/trace/trace_uprobe.c     | 25 +++++++++++++++++++++++++
 5 files changed, 95 insertions(+)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 5150436783e8..96f3cf2e39b4 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -586,6 +586,7 @@ extern int bpf_get_kprobe_info(const struct perf_event *event,
 			       u32 *fd_type, const char **symbol,
 			       u64 *probe_offset, u64 *probe_addr,
 			       bool perf_type_tracepoint);
+extern int perf_kprobe_event_query(struct perf_event *event, void __user *info);
 #endif
 #ifdef CONFIG_UPROBE_EVENTS
 extern int  perf_uprobe_init(struct perf_event *event,
@@ -594,6 +595,7 @@ extern void perf_uprobe_destroy(struct perf_event *event);
 extern int bpf_get_uprobe_info(const struct perf_event *event,
 			       u32 *fd_type, const char **filename,
 			       u64 *probe_offset, bool perf_type_tracepoint);
+extern int perf_uprobe_event_query(struct perf_event *event, void __user *info);
 #endif
 extern int  ftrace_profile_set_filter(struct perf_event *event, int event_id,
 				     char *filter_str);
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 7198ddd0c6b1..8783d29a807a 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -447,6 +447,28 @@ struct perf_event_query_bpf {
 	__u32	ids[0];
 };
 
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_PROBE command
+ * to query information about the probe attached to the perf
+ * event. Currently only supports [uk]probes.
+ */
+struct perf_event_query_probe {
+	/*
+	 * Size of structure for forward/backward compatibility
+	 */
+	__u64	size;
+	/*
+	 * Set by the kernel to indicate number of times this probe
+	 * was temporarily disabled
+	 */
+	__u64	nmissed;
+	/*
+	 * Set by the kernel to indicate number of times this probe
+	 * was hit
+	 */
+	__u64	nhit;
+};
+
 /*
  * Ioctls that can be done on a perf event fd:
  */
@@ -462,6 +484,7 @@ struct perf_event_query_bpf {
 #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
 #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
 #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_QUERY_PROBE		_IOR('$', 12, struct perf_event_query_probe *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0463c1151bae..ed33d50511a3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5060,6 +5060,8 @@ static int perf_event_set_filter(struct perf_event *event, void __user *arg);
 static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd);
 static int perf_copy_attr(struct perf_event_attr __user *uattr,
 			  struct perf_event_attr *attr);
+static int perf_probe_event_query(struct perf_event *event,
+				    void __user *info);
 
 static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned long arg)
 {
@@ -5143,6 +5145,10 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
 
 		return perf_event_modify_attr(event,  &new_attr);
 	}
+#if defined(CONFIG_KPROBE_EVENTS) || defined(CONFIG_UPROBE_EVENTS)
+	case PERF_EVENT_IOC_QUERY_PROBE:
+		return perf_probe_event_query(event, (void __user *)arg);
+#endif
 	default:
 		return -ENOTTY;
 	}
@@ -8833,6 +8839,20 @@ static inline void perf_tp_register(void)
 #endif
 }
 
+static int perf_probe_event_query(struct perf_event *event,
+				    void __user *info)
+{
+#ifdef CONFIG_KPROBE_EVENTS
+	if (event->attr.type == perf_kprobe.type)
+		return perf_kprobe_event_query(event, (void __user *)info);
+#endif
+#ifdef CONFIG_UPROBE_EVENTS
+	if (event->attr.type == perf_uprobe.type)
+		return perf_uprobe_event_query(event, (void __user *)info);
+#endif
+	return -EINVAL;
+}
+
 static void perf_event_free_filter(struct perf_event *event)
 {
 	ftrace_profile_free_filter(event);
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 9d483ad9bb6c..7da9b0102e34 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -196,6 +196,31 @@ bool trace_kprobe_error_injectable(struct trace_event_call *call)
 	return within_error_injection_list(trace_kprobe_address(tk));
 }
 
+int perf_kprobe_event_query(struct perf_event *event, void __user *info)
+{
+	struct perf_event_query_probe __user *uquery = info;
+	struct perf_event_query_probe query = {};
+	struct trace_event_call *call = event->tp_event;
+	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
+	u64 ncopy;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (copy_from_user(&query, uquery,
+			   offsetofend(struct perf_event_query_probe, size)))
+		return -EFAULT;
+
+	ncopy = min_t(u64, query.size, sizeof(query));
+	query.size = ncopy;
+	query.nhit = trace_kprobe_nhit(tk);
+	query.nmissed = tk->rp.kp.nmissed;
+
+	if (copy_to_user(uquery, &query, ncopy))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int register_kprobe_event(struct trace_kprobe *tk);
 static int unregister_kprobe_event(struct trace_kprobe *tk);
 
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 1ceedb9146b1..88c03cc9042e 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -1333,6 +1333,31 @@ static inline void init_trace_event_call(struct trace_uprobe *tu)
 	call->data = tu;
 }
 
+int perf_uprobe_event_query(struct perf_event *event, void __user *info)
+{
+	struct perf_event_query_probe __user *uquery = info;
+	struct perf_event_query_probe query = {};
+	struct trace_event_call *call = event->tp_event;
+	struct trace_uprobe *tu = (struct trace_uprobe *)call->data;
+	u64 ncopy;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (copy_from_user(&query, uquery,
+			   offsetofend(struct perf_event_query_probe, size)))
+		return -EFAULT;
+
+	ncopy = min_t(u64, query.size, sizeof(query));
+	query.size = ncopy;
+	query.nhit = tu->nhit;
+	query.nmissed = 0;
+
+	if (copy_to_user(uquery, &query, ncopy))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int register_uprobe_event(struct trace_uprobe *tu)
 {
 	init_trace_event_call(tu);
-- 
2.21.0

[PATCH v4 bpf-next 2/4] libbpf: Add helpers to extract perf fd from bpf_link

[Daniel Xu]

It is sometimes necessary to perform ioctl's on the underlying perf fd.
There is not currently a way to extract the fd given a bpf_link, so add a
a pair of casting and getting helpers.

The casting and getting helpers are nice because they let us define
broad categories of links that makes it clear to users what they can
expect to extract from what type of link.

Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 tools/lib/bpf/libbpf.c   | 21 +++++++++++++++++++++
 tools/lib/bpf/libbpf.h   | 13 +++++++++++++
 tools/lib/bpf/libbpf.map |  3 +++
 3 files changed, 37 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2233f919dd88..41588e13be2b 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4876,6 +4876,7 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
 
 struct bpf_link {
 	int (*destroy)(struct bpf_link *link);
+	enum bpf_link_type type;
 };
 
 int bpf_link__destroy(struct bpf_link *link)
@@ -4909,6 +4910,24 @@ static int bpf_link__destroy_perf_event(struct bpf_link *link)
 	return err;
 }
 
+const struct bpf_link_fd *bpf_link__as_fd(const struct bpf_link *link)
+{
+	if (link->type != LIBBPF_LINK_FD)
+		return NULL;
+
+	return (struct bpf_link_fd *)link;
+}
+
+enum bpf_link_type bpf_link__type(const struct bpf_link *link)
+{
+	return link->type;
+}
+
+int bpf_link_fd__fd(const struct bpf_link_fd *link)
+{
+	return link->fd;
+}
+
 struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
 						int pfd)
 {
@@ -4932,6 +4951,7 @@ struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
 	if (!link)
 		return ERR_PTR(-ENOMEM);
 	link->link.destroy = &bpf_link__destroy_perf_event;
+	link->link.type = LIBBPF_LINK_FD;
 	link->fd = pfd;
 
 	if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) {
@@ -5225,6 +5245,7 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
 	link = malloc(sizeof(*link));
 	if (!link)
 		return ERR_PTR(-ENOMEM);
+	link->link.type = LIBBPF_LINK_FD;
 	link->link.destroy = &bpf_link__destroy_fd;
 
 	pfd = bpf_raw_tracepoint_open(tp_name, prog_fd);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index e8f70977d137..2ddef5315ff9 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -166,7 +166,20 @@ LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
 LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
 LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
 
+enum bpf_link_type {
+	LIBBPF_LINK_FD,
+};
+
 struct bpf_link;
+struct bpf_link_fd;
+
+/* casting APIs */
+LIBBPF_API const struct bpf_link_fd *
+bpf_link__as_fd(const struct bpf_link *link);
+
+/* getters APIs */
+LIBBPF_API enum bpf_link_type bpf_link__type(const struct bpf_link *link);
+LIBBPF_API int bpf_link_fd__fd(const struct bpf_link_fd *link);
 
 LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 664ce8e7a60e..ed169579896f 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -188,4 +188,7 @@ LIBBPF_0.0.4 {
 LIBBPF_0.0.5 {
 	global:
 		bpf_btf_get_next_id;
+		bpf_link__type;
+		bpf_link__as_fd;
+		bpf_link_fd__fd;
 } LIBBPF_0.0.4;
-- 
2.21.0

[PATCH v4 bpf-next 3/4] tracing/probe: Sync perf_event.h to tools

[Daniel Xu]

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 tools/include/uapi/linux/perf_event.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 7198ddd0c6b1..8783d29a807a 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -447,6 +447,28 @@ struct perf_event_query_bpf {
 	__u32	ids[0];
 };
 
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_PROBE command
+ * to query information about the probe attached to the perf
+ * event. Currently only supports [uk]probes.
+ */
+struct perf_event_query_probe {
+	/*
+	 * Size of structure for forward/backward compatibility
+	 */
+	__u64	size;
+	/*
+	 * Set by the kernel to indicate number of times this probe
+	 * was temporarily disabled
+	 */
+	__u64	nmissed;
+	/*
+	 * Set by the kernel to indicate number of times this probe
+	 * was hit
+	 */
+	__u64	nhit;
+};
+
 /*
  * Ioctls that can be done on a perf event fd:
  */
@@ -462,6 +484,7 @@ struct perf_event_query_bpf {
 #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
 #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
 #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_QUERY_PROBE		_IOR('$', 12, struct perf_event_query_probe *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
-- 
2.21.0

[PATCH v4 bpf-next 4/4] tracing/probe: Add self test for PERF_EVENT_IOC_QUERY_PROBE

[Daniel Xu]

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 .../selftests/bpf/prog_tests/attach_probe.c   | 115 ++++++++++++++++++
 1 file changed, 115 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 5ecc267d98b0..414d5f4f7ccd 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -27,17 +27,27 @@ void test_attach_probe(void)
 	const char *kretprobe_name = "kretprobe/sys_nanosleep";
 	const char *uprobe_name = "uprobe/trigger_func";
 	const char *uretprobe_name = "uretprobe/trigger_func";
+	struct perf_event_query_probe kprobe_query = {};
+	struct perf_event_query_probe kretprobe_query = {};
+	struct perf_event_query_probe uprobe_query = {};
+	struct perf_event_query_probe uretprobe_query = {};
 	const int kprobe_idx = 0, kretprobe_idx = 1;
 	const int uprobe_idx = 2, uretprobe_idx = 3;
 	const char *file = "./test_attach_probe.o";
 	struct bpf_program *kprobe_prog, *kretprobe_prog;
 	struct bpf_program *uprobe_prog, *uretprobe_prog;
 	struct bpf_object *obj;
+	const struct bpf_link_fd *kprobe_fd_link;
+	const struct bpf_link_fd *kretprobe_fd_link;
+	const struct bpf_link_fd *uprobe_fd_link;
+	const struct bpf_link_fd *uretprobe_fd_link;
 	int err, prog_fd, duration = 0, res;
 	struct bpf_link *kprobe_link = NULL;
 	struct bpf_link *kretprobe_link = NULL;
 	struct bpf_link *uprobe_link = NULL;
 	struct bpf_link *uretprobe_link = NULL;
+	int kprobe_fd, kretprobe_fd;
+	int uprobe_fd, uretprobe_fd;
 	int results_map_fd;
 	size_t uprobe_offset;
 	ssize_t base_addr;
@@ -116,6 +126,63 @@ void test_attach_probe(void)
 	/* trigger & validate kprobe && kretprobe */
 	usleep(1);
 
+	kprobe_fd_link = bpf_link__as_fd(kprobe_link);
+	if (CHECK(!kprobe_fd_link, "kprobe_link_as_fd",
+		  "failed to cast link to fd link\n"))
+		goto cleanup;
+
+	kprobe_fd = bpf_link_fd__fd(kprobe_fd_link);
+	if (CHECK(kprobe_fd < 0, "kprobe_get_perf_fd",
+	    "failed to get perf fd from kprobe link\n"))
+		goto cleanup;
+
+	kretprobe_fd_link = bpf_link__as_fd(kretprobe_link);
+	if (CHECK(!kretprobe_fd_link, "kretprobe_link_as_fd",
+		  "failed to cast link to fd link\n"))
+		goto cleanup;
+
+	kretprobe_fd = bpf_link_fd__fd(kretprobe_fd_link);
+	if (CHECK(kretprobe_fd < 0, "kretprobe_get_perf_fd",
+	    "failed to get perf fd from kretprobe link\n"))
+		goto cleanup;
+
+	kprobe_query.size = sizeof(kprobe_query);
+	err = ioctl(kprobe_fd, PERF_EVENT_IOC_QUERY_PROBE, &kprobe_query);
+	if (CHECK(err, "get_kprobe_ioctl",
+		  "failed to issue kprobe query ioctl\n"))
+		goto cleanup;
+	if (CHECK(kprobe_query.size != sizeof(kprobe_query), "get_kprobe_ioctl",
+		  "read incorrect size from kprobe_ioctl: %llu\n",
+		  kprobe_query.size))
+		goto cleanup;
+	if (CHECK(kprobe_query.nmissed > 0, "get_kprobe_ioctl",
+		  "read incorrect nmissed from kprobe_ioctl: %llu\n",
+		  kprobe_query.nmissed))
+		goto cleanup;
+	if (CHECK(kprobe_query.nhit == 0, "get_kprobe_ioctl",
+		  "read incorrect nhit from kprobe_ioctl: %llu\n",
+		  kprobe_query.nhit))
+		goto cleanup;
+
+	kretprobe_query.size = sizeof(kretprobe_query);
+	err = ioctl(kretprobe_fd, PERF_EVENT_IOC_QUERY_PROBE, &kretprobe_query);
+	if (CHECK(err, "get_kretprobe_ioctl",
+		  "failed to issue kretprobe query ioctl\n"))
+		goto cleanup;
+	if (CHECK(kretprobe_query.size != sizeof(kretprobe_query),
+		  "get_kretprobe_ioctl",
+		  "read incorrect size from kretprobe_ioctl: %llu\n",
+		  kretprobe_query.size))
+		goto cleanup;
+	if (CHECK(kretprobe_query.nmissed > 0, "get_kretprobe_ioctl",
+		  "read incorrect nmissed from kretprobe_ioctl: %llu\n",
+		  kretprobe_query.nmissed))
+		goto cleanup;
+	if (CHECK(kretprobe_query.nhit <= 0, "get_kretprobe_ioctl",
+		  "read incorrect nhit from kretprobe_ioctl: %llu\n",
+		  kretprobe_query.nhit))
+		goto cleanup;
+
 	err = bpf_map_lookup_elem(results_map_fd, &kprobe_idx, &res);
 	if (CHECK(err, "get_kprobe_res",
 		  "failed to get kprobe res: %d\n", err))
@@ -135,6 +202,54 @@ void test_attach_probe(void)
 	/* trigger & validate uprobe & uretprobe */
 	get_base_addr();
 
+	uprobe_fd_link = bpf_link__as_fd(uprobe_link);
+	if (CHECK(!uprobe_fd_link, "uprobe_link_as_fd",
+		  "failed to cast link to fd link\n"))
+		goto cleanup;
+
+	uprobe_fd = bpf_link_fd__fd(uprobe_fd_link);
+	if (CHECK(uprobe_fd < 0, "uprobe_get_perf_fd",
+	    "failed to get perf fd from uprobe link\n"))
+		goto cleanup;
+
+	uretprobe_fd_link = bpf_link__as_fd(uretprobe_link);
+	if (CHECK(!uretprobe_fd_link, "uretprobe_link_as_fd",
+		  "failed to cast link to fd link\n"))
+		goto cleanup;
+
+	uretprobe_fd = bpf_link_fd__fd(uretprobe_fd_link);
+	if (CHECK(uretprobe_fd < 0, "uretprobe_get_perf_fd",
+	    "failed to get perf fd from uretprobe link\n"))
+		goto cleanup;
+
+	uprobe_query.size = sizeof(uprobe_query);
+	err = ioctl(uprobe_fd, PERF_EVENT_IOC_QUERY_PROBE, &uprobe_query);
+	if (CHECK(err, "get_uprobe_ioctl",
+		  "failed to issue uprobe query ioctl\n"))
+		goto cleanup;
+	if (CHECK(uprobe_query.nmissed > 0, "get_uprobe_ioctl",
+		  "read incorrect nmissed from uprobe_ioctl: %llu\n",
+		  uprobe_query.nmissed))
+		goto cleanup;
+	if (CHECK(uprobe_query.nhit == 0, "get_uprobe_ioctl",
+		  "read incorrect nhit from uprobe_ioctl: %llu\n",
+		  uprobe_query.nhit))
+		goto cleanup;
+
+	uretprobe_query.size = sizeof(uretprobe_query);
+	err = ioctl(uretprobe_fd, PERF_EVENT_IOC_QUERY_PROBE, &uretprobe_query);
+	if (CHECK(err, "get_uretprobe_ioctl",
+		  "failed to issue uretprobe query ioctl\n"))
+		goto cleanup;
+	if (CHECK(uretprobe_query.nmissed > 0, "get_uretprobe_ioctl",
+		  "read incorrect nmissed from uretprobe_ioctl: %llu\n",
+		  uretprobe_query.nmissed))
+		goto cleanup;
+	if (CHECK(uretprobe_query.nhit <= 0, "get_uretprobe_ioctl",
+		  "read incorrect nhit from uretprobe_ioctl: %llu\n",
+		  uretprobe_query.nhit))
+		goto cleanup;
+
 	err = bpf_map_lookup_elem(results_map_fd, &uprobe_idx, &res);
 	if (CHECK(err, "get_uprobe_res",
 		  "failed to get uprobe res: %d\n", err))
-- 
2.21.0