linux-kernel - [PATCH v1 09/12] dyndbg: add trace destination field to

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Date:   Fri,  3 Nov 2023 14:10:08 +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 v1 09/12] dyndbg: add trace destination field to _ddebug

Add trace destination field (trace_dst) to the _ddebug structure.
The trace destination field is used to determine output of debug
logs when +T is set. Setting trace_dst value to 0 (default) enables
output to prdbg and devdbg trace events. Setting trace_dst value to
a value in range of [1..255] enables output to trace instance.

Signed-off-by: Łukasz Bartosik <lb@...ihalf.com>
---
 include/linux/dynamic_debug.h | 13 +++++++++++--
 lib/dynamic_debug.c           | 28 +++++++++++++++++++---------
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 684766289bfc..3084302876b4 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -60,9 +60,18 @@ struct _ddebug {
 #else
 #define _DPRINTK_FLAGS_DEFAULT 0
 #endif
-	struct {
+	struct dd_ctrl {
 		unsigned int flags:8;
-		unsigned unused:24;
+	/*
+	 * The trace destination field is used to determine output of debug
+	 * logs when +T is set. Setting trace_dst value to 0 (default) enables
+	 * output to prdbg and devdbg trace events. Setting trace_dst value to
+	 * a value in range of [1..255] enables output to trace instance.
+	 */
+#define TRACE_DST_BITS 8
+		unsigned int trace_dst:TRACE_DST_BITS;
+#define TRACE_DST_MAX	((1 << TRACE_DST_BITS) - 1)
+		unsigned unused:16;
 	} ctrl;
 } __attribute__((aligned(8)));
 
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index ca87adf327df..3218ab078a76 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -80,14 +80,24 @@ module_param(verbose, int, 0644);
 MODULE_PARM_DESC(verbose, " dynamic_debug/control processing "
 		 "( 0 = off (default), 1 = module add/rm, 2 = >control summary, 3 = parsing, 4 = per-site changes)");
 
+static inline struct dd_ctrl *get_ctrl(struct _ddebug *desc)
+{
+	return &desc->ctrl;
+}
+
+static inline void set_ctrl(struct _ddebug *desc, struct dd_ctrl *ctrl)
+{
+	desc->ctrl = *ctrl;
+}
+
 static inline unsigned int get_flags(const struct _ddebug *desc)
 {
 	return desc->ctrl.flags;
 }
 
-static inline void set_flags(struct _ddebug *desc, unsigned int val)
+static inline unsigned int get_trace_dst(const struct _ddebug *desc)
 {
-	desc->ctrl.flags = val;
+	return desc->ctrl.trace_dst;
 }
 
 /* Return the path relative to source root */
@@ -190,8 +200,8 @@ static int ddebug_change(const struct ddebug_query *query,
 {
 	int i;
 	struct ddebug_table *dt;
-	unsigned int newflags;
 	unsigned int nfound = 0;
+	struct dd_ctrl nctrl = {0};
 	struct flagsbuf fbuf, nbuf;
 	struct ddebug_class_map *map = NULL;
 	int __outvar valid_class;
@@ -257,14 +267,14 @@ static int ddebug_change(const struct ddebug_query *query,
 
 			nfound++;
 
-			newflags = (get_flags(dp) & modifiers->mask) | modifiers->flags;
-			if (newflags == get_flags(dp))
+			nctrl.flags = (get_flags(dp) & modifiers->mask) | modifiers->flags;
+			if (!memcmp(&nctrl, get_ctrl(dp), sizeof(struct dd_ctrl)))
 				continue;
 #ifdef CONFIG_JUMP_LABEL
 			if (get_flags(dp) & _DPRINTK_FLAGS_ENABLED) {
-				if (!(newflags & _DPRINTK_FLAGS_ENABLED))
+				if (!(nctrl.flags & _DPRINTK_FLAGS_ENABLED))
 					static_branch_disable(&dp->key.dd_key_true);
-			} else if (newflags & _DPRINTK_FLAGS_ENABLED) {
+			} else if (nctrl.flags & _DPRINTK_FLAGS_ENABLED) {
 				static_branch_enable(&dp->key.dd_key_true);
 			}
 #endif
@@ -272,8 +282,8 @@ static int ddebug_change(const struct ddebug_query *query,
 				  trim_prefix(dp->filename), dp->lineno,
 				  dt->mod_name, dp->function,
 				  ddebug_describe_flags(get_flags(dp), &fbuf),
-				  ddebug_describe_flags(newflags, &nbuf));
-			set_flags(dp, newflags);
+				  ddebug_describe_flags(nctrl.flags, &nbuf));
+			set_ctrl(dp, &nctrl);
 		}
 	}
 	mutex_unlock(&ddebug_lock);
-- 
2.42.0.869.gea05f2083d-goog