printk: convert the format for KERN_<LEVEL> to a 2 byte pattern

Instead of "<.>", use an ASCII SOH for the KERN_<LEVEL> prefix initiator.

This saves 1 byte per printk, thousands of bytes in a normal kernel.

No output changes are produced as vprintk_emit converts these uses to
"<.>".

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 16 insertions, 13 deletions

diff --git a/include/linux/kern_levels.h b/include/linux/kern_levels.h
index 337e56ff533..8c719a955b5 100644
--- a/include/linux/kern_levels.h
+++ b/include/linux/kern_levels.h
@@ -1,22 +1,25 @@
 #ifndef __KERN_LEVELS_H__
 #define __KERN_LEVELS_H__
 
-#define KERN_EMERG      "<0>"   /* system is unusable                   */
-#define KERN_ALERT      "<1>"   /* action must be taken immediately     */
-#define KERN_CRIT       "<2>"   /* critical conditions                  */
-#define KERN_ERR        "<3>"   /* error conditions                     */
-#define KERN_WARNING    "<4>"   /* warning conditions                   */
-#define KERN_NOTICE     "<5>"   /* normal but significant condition     */
-#define KERN_INFO       "<6>"   /* informational                        */
-#define KERN_DEBUG      "<7>"   /* debug-level messages                 */
+#define KERN_SOH        "\001"          /* ASCII Start Of Header */
+#define KERN_SOH_ASCII  '\001'
+
+#define KERN_EMERG      KERN_SOH "0"    /* system is unusable */
+#define KERN_ALERT      KERN_SOH "1"    /* action must be taken immediately */
+#define KERN_CRIT       KERN_SOH "2"    /* critical conditions */
+#define KERN_ERR        KERN_SOH "3"    /* error conditions */
+#define KERN_WARNING    KERN_SOH "4"    /* warning conditions */
+#define KERN_NOTICE     KERN_SOH "5"    /* normal but significant condition */
+#define KERN_INFO       KERN_SOH "6"    /* informational */
+#define KERN_DEBUG      KERN_SOH "7"    /* debug-level messages */
+
+#define KERN_DEFAULT    KERN_SOH "d"    /* the default kernel loglevel */
 
-/* Use the default kernel loglevel */
-#define KERN_DEFAULT    "<d>"
 /*
  * Annotation for a "continued" line of log printout (only done after a
  * line that had no enclosing \n). Only to be used by core/arch code
  * during early bootup (a continued line is not SMP-safe otherwise).
  */
-#define KERN_CONT       "<c>"
+#define KERN_CONT       KERN_SOH "c"
 
 #endif
diff --git a/include/linux/printk.h b/include/linux/printk.h
index fea2de37b64..93a231f9835 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -9,7 +9,7 @@ extern const char linux_proc_banner[];
 
 static inline int printk_get_level(const char *buffer)
 {
-        if (buffer[0] == '<' && buffer[1] && buffer[2] == '>') {
+        if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
                 switch (buffer[1]) {
                 case '0' ... '7':
                 case 'd':       /* KERN_DEFAULT */
@@ -27,7 +27,7 @@ static inline const char *printk_skip_level(const char *buffer)
                 case '0' ... '7':
                 case 'd':       /* KERN_DEFAULT */
                 case 'c':       /* KERN_CONT */
-                        return buffer + 3;
+                        return buffer + 2;
                 }
         }
         return buffer;