printk: add support of hh length modifier for printk

Impact: new feature, extend vsprintf format strings

hh is used as length modifier for signed char or unsigned char.
It is supported by glibc, we add kernel support now.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Acked-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: torvalds@linux-foundation.org
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <49CC9739.30107@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

lib/vsprintf.c

@@ -408,6 +408,8 @@ enum format_type {
 	FORMAT_TYPE_LONG_LONG,
 	FORMAT_TYPE_ULONG,
 	FORMAT_TYPE_LONG,
+	FORMAT_TYPE_UBYTE,
+	FORMAT_TYPE_BYTE,
 	FORMAT_TYPE_USHORT,
 	FORMAT_TYPE_SHORT,
 	FORMAT_TYPE_UINT,
@@ -853,11 +855,15 @@ static int format_decode(const char *fmt, struct printf_spec *spec)
 	spec->qualifier = -1;
 	if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' ||
 	    *fmt == 'Z' || *fmt == 'z' || *fmt == 't') {
-		spec->qualifier = *fmt;
-		++fmt;
-		if (spec->qualifier == 'l' && *fmt == 'l') {
+		spec->qualifier = *fmt++;
+		if (unlikely(spec->qualifier == *fmt)) {
+			if (spec->qualifier == 'l') {
 				spec->qualifier = 'L';
 				++fmt;
+			} else if (spec->qualifier == 'h') {
+				spec->qualifier = 'H';
+				++fmt;
+			}
 		}
 	}
 
@@ -919,6 +925,11 @@ static int format_decode(const char *fmt, struct printf_spec *spec)
 		spec->type = FORMAT_TYPE_SIZE_T;
 	} else if (spec->qualifier == 't') {
 		spec->type = FORMAT_TYPE_PTRDIFF;
+	} else if (spec->qualifier == 'H') {
+		if (spec->flags & SIGN)
+			spec->type = FORMAT_TYPE_BYTE;
+		else
+			spec->type = FORMAT_TYPE_UBYTE;
 	} else if (spec->qualifier == 'h') {
 		if (spec->flags & SIGN)
 			spec->type = FORMAT_TYPE_SHORT;
@@ -1087,6 +1098,12 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
 			case FORMAT_TYPE_PTRDIFF:
 				num = va_arg(args, ptrdiff_t);
 				break;
+			case FORMAT_TYPE_UBYTE:
+				num = (unsigned char) va_arg(args, int);
+				break;
+			case FORMAT_TYPE_BYTE:
+				num = (signed char) va_arg(args, int);
+				break;
 			case FORMAT_TYPE_USHORT:
 				num = (unsigned short) va_arg(args, int);
 				break;
@@ -1363,6 +1380,10 @@ do {									\
 			case FORMAT_TYPE_PTRDIFF:
 				save_arg(ptrdiff_t);
 				break;
+			case FORMAT_TYPE_UBYTE:
+			case FORMAT_TYPE_BYTE:
+				save_arg(char);
+				break;
 			case FORMAT_TYPE_USHORT:
 			case FORMAT_TYPE_SHORT:
 				save_arg(short);
@@ -1538,6 +1559,12 @@ int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf)
 			case FORMAT_TYPE_PTRDIFF:
 				num = get_arg(ptrdiff_t);
 				break;
+			case FORMAT_TYPE_UBYTE:
+				num = get_arg(unsigned char);
+				break;
+			case FORMAT_TYPE_BYTE:
+				num = get_arg(signed char);
+				break;
 			case FORMAT_TYPE_USHORT:
 				num = get_arg(unsigned short);
 				break;