linux-kernel - [PATCH AUTOSEL 4.14 18/20] tracing: Have TRACE_DEFINE

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Message-Id: <20220330115336.1672930-18-sashal@kernel.org>
Date:   Wed, 30 Mar 2022 07:53:34 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>, mingo@...hat.com
Subject: [PATCH AUTOSEL 4.14 18/20] tracing: Have TRACE_DEFINE_ENUM affect trace event types as well

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

[ Upstream commit b3bc8547d3be60898818885f5bf22d0a62e2eb48 ]

The macro TRACE_DEFINE_ENUM is used to convert enums in the kernel to
their actual value when they are exported to user space via the trace
event format file.

Currently only the enums in the "print fmt" (TP_printk in the TRACE_EVENT
macro) have the enums converted. But the enums can be used to denote array
size:

        field:unsigned int fc_ineligible_rc[EXT4_FC_REASON_MAX]; offset:12;      size:36;        signed:0;

The EXT4_FC_REASON_MAX has no meaning to userspace but it needs to know
that information to know how to parse the array.

Have the array indexes also be parsed as well.

Link: https://lore.kernel.org/all/cover.1646922487.git.riteshh@linux.ibm.com/

Reported-by: Ritesh Harjani <riteshh@...ux.ibm.com>
Tested-by: Ritesh Harjani <riteshh@...ux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/trace/trace_events.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 1285ef6e2d14..7c2d4ff7a51f 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2209,6 +2209,33 @@ static void update_event_printk(struct trace_event_call *call,
 	}
 }
 
+static void update_event_fields(struct trace_event_call *call,
+				struct trace_eval_map *map)
+{
+	struct ftrace_event_field *field;
+	struct list_head *head;
+	char *ptr;
+	int len = strlen(map->eval_string);
+
+	head = trace_get_fields(call);
+	list_for_each_entry(field, head, link) {
+		ptr = strchr(field->type, '[');
+		if (!ptr)
+			continue;
+		ptr++;
+
+		if (!isalpha(*ptr) && *ptr != '_')
+			continue;
+
+		if (strncmp(map->eval_string, ptr, len) != 0)
+			continue;
+
+		ptr = eval_replace(ptr, map, len);
+		/* enum/sizeof string smaller than value */
+		WARN_ON_ONCE(!ptr);
+	}
+}
+
 void trace_event_eval_update(struct trace_eval_map **map, int len)
 {
 	struct trace_event_call *call, *p;
@@ -2244,6 +2271,7 @@ void trace_event_eval_update(struct trace_eval_map **map, int len)
 					first = false;
 				}
 				update_event_printk(call, map[i]);
+				update_event_fields(call, map[i]);
 			}
 		}
 	}
-- 
2.34.1