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Date:   Fri, 01 May 2020 22:28:51 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, bristot@...hat.com,
        jbaron@...mai.com, torvalds@...ux-foundation.org,
        tglx@...utronix.de, mingo@...nel.org, namit@...are.com,
        hpa@...or.com, luto@...nel.org, ard.biesheuvel@...aro.org,
        jpoimboe@...hat.com, pbonzini@...hat.com,
        mathieu.desnoyers@...icios.com,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Robert Richter <rric@...nel.org>
Subject: [PATCH v4 02/18] module: Fix up module_notifier return values

While auditing all module notifiers I noticed a whole bunch of fail
wrt the return value. Notifiers have a 'special' return semantics.

As is; NOTIFY_DONE vs NOTIFY_OK is a bit vague; but
notifier_from_errno(0) results in NOTIFY_OK and NOTIFY_DONE has a
comment that says "Don't care".

>>From this I've used NOTIFY_DONE when the function completely ignores
the callback and notifier_to_error() isn't used.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Reviewed-by: Robert Richter <rric@...nel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 drivers/oprofile/buffer_sync.c |    4 ++--
 kernel/trace/bpf_trace.c       |    8 ++++++--
 kernel/trace/trace.c           |    2 +-
 kernel/trace/trace_events.c    |    2 +-
 kernel/trace/trace_printk.c    |    4 ++--
 kernel/tracepoint.c            |    2 +-
 6 files changed, 13 insertions(+), 9 deletions(-)

--- a/drivers/oprofile/buffer_sync.c
+++ b/drivers/oprofile/buffer_sync.c
@@ -116,7 +116,7 @@ module_load_notify(struct notifier_block
 {
 #ifdef CONFIG_MODULES
 	if (val != MODULE_STATE_COMING)
-		return 0;
+		return NOTIFY_DONE;
 
 	/* FIXME: should we process all CPU buffers ? */
 	mutex_lock(&buffer_mutex);
@@ -124,7 +124,7 @@ module_load_notify(struct notifier_block
 	add_event_entry(MODULE_LOADED_CODE);
 	mutex_unlock(&buffer_mutex);
 #endif
-	return 0;
+	return NOTIFY_OK;
 }
 
 
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1451,10 +1451,11 @@ static int bpf_event_notify(struct notif
 {
 	struct bpf_trace_module *btm, *tmp;
 	struct module *mod = module;
+	int ret = 0;
 
 	if (mod->num_bpf_raw_events == 0 ||
 	    (op != MODULE_STATE_COMING && op != MODULE_STATE_GOING))
-		return 0;
+		goto out;
 
 	mutex_lock(&bpf_module_mutex);
 
@@ -1464,6 +1465,8 @@ static int bpf_event_notify(struct notif
 		if (btm) {
 			btm->module = module;
 			list_add(&btm->list, &bpf_trace_modules);
+		} else {
+			ret = -ENOMEM;
 		}
 		break;
 	case MODULE_STATE_GOING:
@@ -1479,7 +1482,8 @@ static int bpf_event_notify(struct notif
 
 	mutex_unlock(&bpf_module_mutex);
 
-	return 0;
+out:
+	return notifier_from_errno(ret);
 }
 
 static struct notifier_block bpf_module_nb = {
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8696,7 +8696,7 @@ static int trace_module_notify(struct no
 		break;
 	}
 
-	return 0;
+	return NOTIFY_OK;
 }
 
 static struct notifier_block trace_module_nb = {
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2442,7 +2442,7 @@ static int trace_module_notify(struct no
 	mutex_unlock(&trace_types_lock);
 	mutex_unlock(&event_mutex);
 
-	return 0;
+	return NOTIFY_OK;
 }
 
 static struct notifier_block trace_module_nb = {
--- a/kernel/trace/trace_printk.c
+++ b/kernel/trace/trace_printk.c
@@ -95,7 +95,7 @@ static int module_trace_bprintk_format_n
 		if (val == MODULE_STATE_COMING)
 			hold_module_trace_bprintk_format(start, end);
 	}
-	return 0;
+	return NOTIFY_OK;
 }
 
 /*
@@ -173,7 +173,7 @@ __init static int
 module_trace_bprintk_format_notify(struct notifier_block *self,
 		unsigned long val, void *data)
 {
-	return 0;
+	return NOTIFY_OK;
 }
 static inline const char **
 find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -521,7 +521,7 @@ static int tracepoint_module_notify(stru
 	case MODULE_STATE_UNFORMED:
 		break;
 	}
-	return ret;
+	return notifier_from_errno(ret);
 }
 
 static struct notifier_block tracepoint_module_nb = {


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