[PATCH v5 02/17] module: Fix up module_notifier return values

Peter Zijlstra
2020-06-24T15:52:33Z

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@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Robert Richter <rric@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.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 = {