linux-kernel - [PATCH v3 11/22] dyndbg: don't close trace instance when in use

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Message-ID: <20231223015131.2836090-12-lb@semihalf.com>
Date: Sat, 23 Dec 2023 02:51:20 +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>,
	Simon Ser <contact@...rsion.fr>,
	John Ogness <john.ogness@...utronix.de>,
	Petr Mladek <pmladek@...e.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	linux-kernel@...r.kernel.org,
	upstream@...ihalf.com
Subject: [PATCH v3 11/22] dyndbg: don't close trace instance when in use

Don't allow trace instance to be closed when it
is still being used by at least one callsite.

Signed-off-by: Łukasz Bartosik <lb@...ihalf.com>
---
 lib/dynamic_debug.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index dd4510ad124e..59682729ed3a 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -81,6 +81,7 @@ struct flag_settings {
 struct dd_private_tracebuf {
 	const char *name;
 	struct trace_array *arr;
+	int use_cnt;
 };
 
 /*
@@ -279,6 +280,7 @@ static int handle_trace_open_cmd(const char *arg)
 		goto end;
 	}
 
+	buf->use_cnt = 0;
 	set_bit(idx, trc_tbl.bmap);
 	v3pr_info("opened trace instance idx=%d, name=%s\n", idx, arg);
 end:
@@ -301,6 +303,14 @@ static int handle_trace_close_cmd(const char *arg)
 
 	buf = &trc_tbl.buf[idx];
 
+	WARN_ON(buf->use_cnt < 0);
+	if (buf->use_cnt) {
+		pr_err("trace instance is being used name=%s, use_cnt=%d\n",
+		       buf->name, buf->use_cnt);
+		ret = -EBUSY;
+		goto end;
+	}
+
 	trace_array_put(buf->arr);
 	/*
 	 * don't destroy trace instance but let user do it manually
@@ -321,6 +331,24 @@ static int handle_trace_close_cmd(const char *arg)
 	return ret;
 }
 
+static
+void update_tr_dst(const struct _ddebug *desc, const struct dd_ctrl *nctrl)
+{
+	int oflags = get_flags(desc), odst = get_trace_dst(desc);
+	int nflags = nctrl->flags, ndst = nctrl->trace_dst;
+
+	if (oflags & _DPRINTK_FLAGS_TRACE &&
+	    nflags & _DPRINTK_FLAGS_TRACE &&
+	    odst == ndst)
+		return;
+
+	if (odst && (oflags & _DPRINTK_FLAGS_TRACE))
+		trc_tbl.buf[odst].use_cnt--;
+
+	if (ndst && (nflags & _DPRINTK_FLAGS_TRACE))
+		trc_tbl.buf[ndst].use_cnt++;
+}
+
 static int ddebug_parse_cmd(char *words[], int nwords)
 {
 	if (nwords != 1)
@@ -447,6 +475,7 @@ static int ddebug_change(const struct ddebug_query *query,
 				  dt->mod_name, dp->function,
 				  ddebug_describe_flags(get_flags(dp), &fbuf),
 				  ddebug_describe_flags(nctrl.flags, &nbuf));
+			update_tr_dst(dp, &nctrl);
 			set_ctrl(dp, &nctrl);
 		}
 	}
@@ -1628,6 +1657,15 @@ int ddebug_dyndbg_module_param_cb(char *param, char *val, const char *module)
 
 static void ddebug_table_free(struct ddebug_table *dt)
 {
+
+	int dst, i;
+
+	for (i = 0; i < dt->num_ddebugs; i++) {
+		dst = get_trace_dst(&dt->ddebugs[i]);
+		if (dst && (get_flags(&dt->ddebugs[i]) & _DPRINTK_FLAGS_TRACE))
+			trc_tbl.buf[dst].use_cnt--;
+	}
+
 	list_del_init(&dt->link);
 	kfree(dt);
 }
-- 
2.43.0.472.g3155946c3a-goog