bpf: Add missed value to kprobe perf link info

[ Upstream commit 3acf8ace68230e9558cf916847f1cc9f208abdf1 ]

Add missed value to kprobe attached through perf link info to
hold the stats of missed kprobe handler execution.

The kprobe's missed counter gets incremented when kprobe handler
is not executed due to another kprobe running on the same cpu.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230920213145.1941596-4-jolsa@kernel.org
Stable-dep-of: 4deecdd29cf2 ("bpf: fix unpopulated name_len field in perf_event link info")
Signed-off-by: Sasha Levin <sashal@kernel.org>

3 files changed, 22 insertions, 11 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b1933d074f05..9c76f21f187f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3444,7 +3444,7 @@ static void bpf_perf_link_dealloc(struct bpf_link *link)
 static int bpf_perf_link_fill_common(const struct perf_event *event,
 				     char __user *uname, u32 ulen,
 				     u64 *probe_offset, u64 *probe_addr,
-				     u32 *fd_type)
+				     u32 *fd_type, unsigned long *missed)
 {
 	const char *buf;
 	u32 prog_id;
@@ -3455,7 +3455,7 @@ static int bpf_perf_link_fill_common(const struct perf_event *event,
 		return -EINVAL;
 
 	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
-				      probe_offset, probe_addr);
+				      probe_offset, probe_addr, missed);
 	if (err)
 		return err;
 	if (!uname)
@@ -3478,6 +3478,7 @@ static int bpf_perf_link_fill_common(const struct perf_event *event,
 static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
 				     struct bpf_link_info *info)
 {
+	unsigned long missed;
 	char __user *uname;
 	u64 addr, offset;
 	u32 ulen, type;
@@ -3486,7 +3487,7 @@ static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
 	uname = u64_to_user_ptr(info->perf_event.kprobe.func_name);
 	ulen = info->perf_event.kprobe.name_len;
 	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,
-					&type);
+					&type, &missed);
 	if (err)
 		return err;
 	if (type == BPF_FD_TYPE_KRETPROBE)
@@ -3495,6 +3496,7 @@ static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
 		info->perf_event.type = BPF_PERF_EVENT_KPROBE;
 
 	info->perf_event.kprobe.offset = offset;
+	info->perf_event.kprobe.missed = missed;
 	if (!kallsyms_show_value(current_cred()))
 		addr = 0;
 	info->perf_event.kprobe.addr = addr;
@@ -3514,7 +3516,7 @@ static int bpf_perf_link_fill_uprobe(const struct perf_event *event,
 	uname = u64_to_user_ptr(info->perf_event.uprobe.file_name);
 	ulen = info->perf_event.uprobe.name_len;
 	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,
-					&type);
+					&type, NULL);
 	if (err)
 		return err;
 
@@ -3550,7 +3552,7 @@ static int bpf_perf_link_fill_tracepoint(const struct perf_event *event,
 	uname = u64_to_user_ptr(info->perf_event.tracepoint.tp_name);
 	ulen = info->perf_event.tracepoint.name_len;
 	info->perf_event.type = BPF_PERF_EVENT_TRACEPOINT;
-	return bpf_perf_link_fill_common(event, uname, ulen, NULL, NULL, NULL);
+	return bpf_perf_link_fill_common(event, uname, ulen, NULL, NULL, NULL, NULL);
 }
 
 static int bpf_perf_link_fill_perf_event(const struct perf_event *event,
@@ -4897,7 +4899,7 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
 
 		err = bpf_get_perf_event_info(event, &prog_id, &fd_type,
 					      &buf, &probe_offset,
-					      &probe_addr);
+					      &probe_addr, NULL);
 		if (!err)
 			err = bpf_task_fd_query_copy(attr, uattr, prog_id,
 						     fd_type, buf,
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index eca858bde804..bbdc4199748b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2389,7 +2389,8 @@ int bpf_probe_unregister(struct bpf_raw_event_map *btp, struct bpf_prog *prog)
 
 int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
 			    u32 *fd_type, const char **buf,
-			    u64 *probe_offset, u64 *probe_addr)
+			    u64 *probe_offset, u64 *probe_addr,
+			    unsigned long *missed)
 {
 	bool is_tracepoint, is_syscall_tp;
 	struct bpf_prog *prog;
@@ -2424,7 +2425,7 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
 #ifdef CONFIG_KPROBE_EVENTS
 		if (flags & TRACE_EVENT_FL_KPROBE)
 			err = bpf_get_kprobe_info(event, fd_type, buf,
-						  probe_offset, probe_addr,
+						  probe_offset, probe_addr, missed,
 						  event->attr.type == PERF_TYPE_TRACEPOINT);
 #endif
 #ifdef CONFIG_UPROBE_EVENTS
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 47812aa16bb5..52f8b537dd0a 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1249,6 +1249,12 @@ static const struct file_operations kprobe_events_ops = {
 	.write		= probes_write,
 };
 
+static unsigned long trace_kprobe_missed(struct trace_kprobe *tk)
+{
+	return trace_kprobe_is_return(tk) ?
+		tk->rp.kp.nmissed + tk->rp.nmissed : tk->rp.kp.nmissed;
+}
+
 /* Probes profiling interfaces */
 static int probes_profile_seq_show(struct seq_file *m, void *v)
 {
@@ -1260,8 +1266,7 @@ static int probes_profile_seq_show(struct seq_file *m, void *v)
 		return 0;
 
 	tk = to_trace_kprobe(ev);
-	nmissed = trace_kprobe_is_return(tk) ?
-		tk->rp.kp.nmissed + tk->rp.nmissed : tk->rp.kp.nmissed;
+	nmissed = trace_kprobe_missed(tk);
 	seq_printf(m, "  %-44s %15lu %15lu\n",
 		   trace_probe_name(&tk->tp),
 		   trace_kprobe_nhit(tk),
@@ -1607,7 +1612,8 @@ NOKPROBE_SYMBOL(kretprobe_perf_func);
 
 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)
+			u64 *probe_addr, unsigned long *missed,
+			bool perf_type_tracepoint)
 {
 	const char *pevent = trace_event_name(event->tp_event);
 	const char *group = event->tp_event->class->system;
@@ -1626,6 +1632,8 @@ int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
 	*probe_addr = kallsyms_show_value(current_cred()) ?
 		      (unsigned long)tk->rp.kp.addr : 0;
 	*symbol = tk->symbol;
+	if (missed)
+		*missed = trace_kprobe_missed(tk);
 	return 0;
 }
 #endif	/* CONFIG_PERF_EVENTS */