Subject: [PATCH 39/48] printk: Provide helper for message prepending
From: John Ogness <[email-masked]>
Date: Thu, 28 Mar 2024 13:29:10 +0000

In order to support prepending different texts to printk
messages, split out the prepending code into a helper
function.

Signed-off-by: John Ogness <[email-masked]>
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 kernel/printk/printk.c |   38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

Index: linux-6.8.2-rt10/kernel/printk/printk.c
===================================================================
--- linux-6.8.2-rt10.orig/kernel/printk/printk.c
+++ linux-6.8.2-rt10/kernel/printk/printk.c
@@ -2819,30 +2819,25 @@ static void __console_unlock(void)
 #ifdef CONFIG_PRINTK
 
 /*
- * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This
- * is achieved by shifting the existing message over and inserting the dropped
- * message.
+ * Prepend the message in @pmsg->pbufs->outbuf with the message in
+ * @pmsg->pbufs->scratchbuf. This is achieved by shifting the existing message
+ * over and inserting the scratchbuf message.
  *
  * @pmsg is the printk message to prepend.
  *
- * @dropped is the dropped count to report in the dropped message.
+ * @len is the length of the message in @pmsg->pbufs->scratchbuf.
  *
  * If the message text in @pmsg->pbufs->outbuf does not have enough space for
- * the dropped message, the message text will be sufficiently truncated.
+ * the scratchbuf message, the message text will be sufficiently truncated.
  *
  * If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
  */
-void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
+static void __console_prepend_scratch(struct printk_message *pmsg, size_t len)
 {
 	struct printk_buffers *pbufs = pmsg->pbufs;
-	const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
 	const size_t outbuf_sz = sizeof(pbufs->outbuf);
 	char *scratchbuf = &pbufs->scratchbuf[0];
 	char *outbuf = &pbufs->outbuf[0];
-	size_t len;
-
-	len = scnprintf(scratchbuf, scratchbuf_sz,
-		       "** %lu printk messages dropped **\n", dropped);
 
 	/*
 	 * Make sure outbuf is sufficiently large before prepending.
@@ -2865,6 +2860,27 @@ void console_prepend_dropped(struct prin
 }
 
 /*
+ * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message".
+ * @pmsg->outbuf_len is updated appropriately.
+ *
+ * @pmsg is the printk message to prepend.
+ *
+ * @dropped is the dropped count to report in the dropped message.
+ */
+void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
+{
+	struct printk_buffers *pbufs = pmsg->pbufs;
+	const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
+	char *scratchbuf = &pbufs->scratchbuf[0];
+	size_t len;
+
+	len = scnprintf(scratchbuf, scratchbuf_sz,
+		       "** %lu printk messages dropped **\n", dropped);
+
+	__console_prepend_scratch(pmsg, len);
+}
+
+/*
  * Read and format the specified record (or a later record if the specified
  * record is not available).
  *