This does the simplest possible thing: add a directory at the root of
sysfs that allows setting the "maxlevel" parameter for each console.
We can let kobject destruction race with console removal: if it does,
maxlevel_{show,store}() will safely fail with -ENODEV. This is a little
weird, but avoids embedding the kobject and therefore needing to totally
refactor the way we handle console struct lifetime.
Signed-off-by: Calvin Owens <calvinow...@fb.com>
---
include/linux/console.h | 1 +
kernel/printk/printk.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 83 insertions(+)
diff --git a/include/linux/console.h b/include/linux/console.h
index 764a2c0..c76fde0 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -148,6 +148,7 @@ struct console {
void *data;
struct console *next;
int maxlevel;
+ struct kobject *kobj;
};
/*
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5393928..e9d036b 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -105,6 +105,8 @@ enum devkmsg_log_masks {
static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
+static struct kobject *consoles_dir_kobj;
+
static int __control_devkmsg(char *str)
{
if (!str)
@@ -2386,6 +2388,76 @@ static int __init keep_bootcon_setup(char *str)
early_param("keep_bootcon", keep_bootcon_setup);
+static ssize_t maxlevel_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct console *con;
+ ssize_t ret = -ENODEV;
+
+ console_lock();
+ for_each_console(con) {
+ if (con->kobj == kobj) {
+ ret = sprintf(buf, "%d\n", con->maxlevel);
+ break;
+ }
+ }
+ console_unlock();
+
+ return ret;
+}
+
+static ssize_t maxlevel_store(struct kobject *kobj, struct kobj_attribute
*attr,
+ const char *buf, size_t count)
+{
+ struct console *con;
+ ssize_t ret;
+ int tmp;
+
+ ret = kstrtoint(buf, 10, &tmp);
+ if (ret < 0)
+ return ret;
+
+ if (tmp < 0 || tmp > LOGLEVEL_DEBUG)
+ return -ERANGE;
+
+ ret = -ENODEV;
+ console_lock();
+ for_each_console(con) {
+ if (con->kobj == kobj) {
+ con->maxlevel = tmp;
+ ret = count;
+ break;
+ }
+ }
+ console_unlock();
+
+ return ret;
+}
+
+static const struct kobj_attribute console_level_attr =
+ __ATTR(maxlevel, 0644, maxlevel_show, maxlevel_store);
+
+static void console_register_sysfs(struct console *newcon)
+{
+ /*
+ * We might be called very early from register_console(): in that case,
+ * printk_late_init() will take care of this later.
+ */
+ if (!consoles_dir_kobj)
+ return;
+
+ newcon->kobj = kobject_create_and_add(newcon->name, consoles_dir_kobj);
+ if (WARN_ON(!newcon->kobj))
+ return;
+
+ WARN_ON(sysfs_create_file(newcon->kobj, &console_level_attr.attr));
+}
+
+static void console_unregister_sysfs(struct console *oldcon)
+{
+ kobject_put(oldcon->kobj);
+}
+
/*
* The console driver calls this routine during kernel initialization
* to register the console printing procedure with printk() and to
@@ -2509,6 +2581,7 @@ void register_console(struct console *newcon)
* By default, the per-console loglevel filter permits all messages.
*/
newcon->maxlevel = LOGLEVEL_DEBUG;
+ newcon->kobj = NULL;
/*
* Put this console in the list - keep the
@@ -2545,6 +2618,7 @@ void register_console(struct console *newcon)
*/
exclusive_console = newcon;
}
+ console_register_sysfs(newcon);
console_unlock();
console_sysfs_notify();
@@ -2611,6 +2685,7 @@ int unregister_console(struct console *console)
console_drivers->flags |= CON_CONSDEV;
console->flags &= ~CON_ENABLED;
+ console_unregister_sysfs(console);
console_unlock();
console_sysfs_notify();
return res;
@@ -2656,6 +2731,13 @@ static int __init printk_late_init(void)
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
console_cpu_notify, NULL);
WARN_ON(ret < 0);
+
+ consoles_dir_kobj = kobject_create_and_add("consoles", NULL);
+ WARN_ON(!consoles_dir_kobj);
+
+ for_each_console(con)
+ console_register_sysfs(con);
+
return 0;
}
late_initcall(printk_late_init);
--
2.9.3
