[PATCH v2 1/3] printk: introduce new macros pr_<level>_cont()

From: Thomas Weißschuh
Date: Fri Nov 25 2022 - 14:10:18 EST


These macros emit continuation messages with explicit levels.
In case the continuation is logged separately from the original message
it will retain its level instead of falling back to KERN_DEFAULT.

This remedies the issue that logs filtered by level contain stray
continuation messages without context.

Suggested-by: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
include/linux/printk.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 8c81806c2e99..8f564c38f121 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -537,6 +537,8 @@ struct pi_entry {
* This macro expands to a printk with KERN_CONT loglevel. It should only be
* used when continuing a log message with no newline ('\n') enclosed. Otherwise
* it defaults back to KERN_DEFAULT loglevel.
+ *
+ * Use the dedicated pr_<level>_cont() macros instead.
*/
#define pr_cont(fmt, ...) \
printk(KERN_CONT fmt, ##__VA_ARGS__)
@@ -701,6 +703,27 @@ do { \
no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#endif

+/*
+ * Print a continuation message with level. In case the continuation is split
+ * from the main message it preserves the level.
+ */
+
+#define pr_emerg_cont(fmt, ...) \
+ printk(KERN_EMERG KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_alert_cont(fmt, ...) \
+ printk(KERN_ALERT KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_crit_cont(fmt, ...) \
+ printk(KERN_CRIT KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_err_cont(fmt, ...) \
+ printk(KERN_ERR KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_warn_cont(fmt, ...) \
+ printk(KERN_WARN KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_notice_cont(fmt, ...) \
+ printk(KERN_NOTICE KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_info_cont(fmt, ...) \
+ printk(KERN_INFO KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+/* no pr_debug_ratelimited, it doesn't make sense with CONFIG_DYNAMIC_DEBUG. */
+
extern const struct file_operations kmsg_fops;

enum {
--
2.38.1