linux-kernel - [PATCH v2 14/15] dyndbg: write debug logs to trace instance

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Message-ID: <20231130234048.157509-15-lb@semihalf.com>
Date:   Fri,  1 Dec 2023 00:40:47 +0100
From:   Łukasz Bartosik <lb@...ihalf.com>
To:     Jason Baron <jbaron@...mai.com>, Jim Cromie <jim.cromie@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Douglas Anderson <dianders@...omium.org>
Cc:     Guenter Roeck <groeck@...gle.com>,
        Yaniv Tzoreff <yanivt@...gle.com>,
        Benson Leung <bleung@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Pekka Paalanen <ppaalanen@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        upstream@...ihalf.com
Subject: [PATCH v2 14/15] dyndbg: write debug logs to trace instance

When trace is enabled (T flag is set) and trace destination field
is set to a value in range [0..62] (TRACE_DST_MAX(63) is reserved
for writing to trace events) then debug logs will be written to a
trace instance pointed by inst[trace destination].name, e.g. when
trace destination value is 2 and inst[2].name is set to tbt then
debug logs will be written to <debugfs>/tracing/instances/tbt
instance.

Before using trace instance as a destination for writing debug
logs it has to be explicitly opened with open command.

Signed-off-by: Łukasz Bartosik <lb@...ihalf.com>
---
 lib/dynamic_debug.c | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index ae05b3728520..afcc536c2e91 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -141,6 +141,11 @@ static inline bool has_tr_default_dst(void)
 	return tr.default_dst != DST_NOT_SET;
 }
 
+static inline bool is_tr_event_dst(const struct _ddebug *desc)
+{
+	return desc->ctrl.trace_dst == TRACE_DST_MAX;
+}
+
 static int find_tr_instance(const char *name)
 {
 	int idx;
@@ -1251,8 +1256,8 @@ static DEFINE_PER_CPU(struct ddebug_trace_bufs, ddebug_trace_bufs);
 static DEFINE_PER_CPU(int, ddebug_trace_reserve);
 
 __printf(3, 0)
-static void ddebug_trace(struct _ddebug *desc, const struct device *dev,
-			 const char *fmt, va_list args)
+static void ddebug_trace_event(struct _ddebug *desc, const struct device *dev,
+			       const char *fmt, va_list args)
 {
 	struct ddebug_trace_buf *buf;
 	int bufidx;
@@ -1283,6 +1288,18 @@ static void ddebug_trace(struct _ddebug *desc, const struct device *dev,
 	preempt_enable_notrace();
 }
 
+__printf(2, 0)
+static void ddebug_trace_instance(struct _ddebug *desc, const char *fmt,
+				  va_list *args)
+{
+	struct va_format vaf = { .fmt = fmt, .va = args};
+	struct trace_array *arr = tr.inst[get_trace_dst(desc)].arr;
+
+	WARN_ON_ONCE(!arr);
+
+	trace_array_printk(arr, 0, "%pV", &vaf);
+}
+
 __printf(2, 3)
 static void ddebug_printk(struct _ddebug *desc, const char *fmt, ...)
 {
@@ -1295,7 +1312,11 @@ static void ddebug_printk(struct _ddebug *desc, const char *fmt, ...)
 		 * All callers include the KERN_DEBUG prefix to keep the
 		 * vprintk case simple; strip it out for tracing.
 		 */
-		ddebug_trace(desc, NULL, fmt + strlen(KERN_DEBUG), args);
+		if (is_tr_event_dst(desc))
+			ddebug_trace_event(desc, NULL,
+					   fmt + strlen(KERN_DEBUG), args);
+		else
+			ddebug_trace_instance(desc, fmt, &args);
 		va_end(args);
 	}
 
@@ -1317,7 +1338,10 @@ static void ddebug_dev_printk(struct _ddebug *desc, const struct device *dev,
 		va_list args;
 
 		va_start(args, fmt);
-		ddebug_trace(desc, dev, fmt, args);
+		if (is_tr_event_dst(desc))
+			ddebug_trace_event(desc, dev, fmt, args);
+		else
+			ddebug_trace_instance(desc, fmt, &args);
 		va_end(args);
 	}
 
-- 
2.43.0.rc2.451.g8631bc7472-goog