printk: add generic functions to find KERN_<LEVEL> headers

The current form of a KERN_<LEVEL> is "<.>".

Add printk_get_level and printk_skip_level functions to handle these
formats.

These functions centralize tests of KERN_<LEVEL> so a future modification
can change the KERN_<LEVEL> style and shorten the number of bytes consumed
by these headers.

[akpm@linux-foundation.org: fix build error and warning]
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Wu Fengguang <wfg@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/printk.h

@@ -24,6 +24,32 @@ extern const char linux_proc_banner[];
  */
 #define KERN_CONT	"<c>"
 
+static inline int printk_get_level(const char *buffer)
+{
+	if (buffer[0] == '<' && buffer[1] && buffer[2] == '>') {
+		switch (buffer[1]) {
+		case '0' ... '7':
+		case 'd':	/* KERN_DEFAULT */
+		case 'c':	/* KERN_CONT */
+			return buffer[1];
+		}
+	}
+	return 0;
+}
+
+static inline const char *printk_skip_level(const char *buffer)
+{
+	if (printk_get_level(buffer)) {
+		switch (buffer[1]) {
+		case '0' ... '7':
+		case 'd':	/* KERN_DEFAULT */
+		case 'c':	/* KERN_CONT */
+			return buffer + 3;
+		}
+	}
+	return buffer;
+}
+
 extern int console_printk[];
 
 #define console_loglevel (console_printk[0])

kernel/printk.c

@@ -1487,6 +1487,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 	size_t text_len;
 	enum log_flags lflags = 0;
 	unsigned long flags;
+	int kern_level;
 	int this_cpu;
 	int printed_len = 0;
 
@@ -1543,17 +1544,20 @@ asmlinkage int vprintk_emit(int facility, int level,
 	}
 
 	/* strip syslog prefix and extract log level or control flags */
-	if (text[0] == '<' && text[1] && text[2] == '>') {
-		switch (text[1]) {
+	kern_level = printk_get_level(text);
+	if (kern_level) {
+		const char *end_of_header = printk_skip_level(text);
+		switch (kern_level) {
 		case '0' ... '7':
 			if (level == -1)
-				level = text[1] - '0';
+				level = kern_level - '0';
 		case 'd':	/* KERN_DEFAULT */
 			lflags |= LOG_PREFIX;
 		case 'c':	/* KERN_CONT */
-			text += 3;
-			text_len -= 3;
+			break;
 		}
+		text_len -= end_of_header - text;
+		text = (char *)end_of_header;
 	}
 
 	if (level == -1)