vsprintf: fix calling convention for format_decode()

Every single caller wants to know what the next format location is, but
instead the function returned the length of the processed part and so
every single return statement in the format_decode() function was
instead subtracting the start of the format string.

The callers that that did want to know the length (in addition to the
end of the format processing) already had to save off the start of the
format string anyway.  So this was all just doing extra processing both
on the caller and callee sides.

Just change the calling convention to return the end of the format
processing, making everything simpler (and preparing for yet more
simplification to come).

Signed-off-by: Linus Torvalds <[email protected]>

Author: torvalds

lib/vsprintf.c

@@ -2546,7 +2546,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
  * @qualifier: qualifier of a number (long, size_t, ...)
  */
 static noinline_for_stack
-int format_decode(const char *fmt, struct printf_spec *spec)
+const char *format_decode(const char *fmt, struct printf_spec *spec)
 {
 	const char *start = fmt;
 	char qualifier;
@@ -2580,7 +2580,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 
 	/* Return the current non-format string */
 	if (fmt != start || !*fmt)
-		return fmt - start;
+		return fmt;
 
 	/* Process flags */
 	spec->flags = 0;
@@ -2611,7 +2611,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 	else if (*fmt == '*') {
 		/* it's the next argument */
 		spec->type = FORMAT_TYPE_WIDTH;
-		return ++fmt - start;
+		return ++fmt;
 	}
 
 precision:
@@ -2626,7 +2626,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 		} else if (*fmt == '*') {
 			/* it's the next argument */
 			spec->type = FORMAT_TYPE_PRECISION;
-			return ++fmt - start;
+			return ++fmt;
 		}
 	}
 
@@ -2652,19 +2652,19 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 	switch (*fmt) {
 	case 'c':
 		spec->type = FORMAT_TYPE_CHAR;
-		return ++fmt - start;
+		return ++fmt;
 
 	case 's':
 		spec->type = FORMAT_TYPE_STR;
-		return ++fmt - start;
+		return ++fmt;
 
 	case 'p':
 		spec->type = FORMAT_TYPE_PTR;
-		return ++fmt - start;
+		return ++fmt;
 
 	case '%':
 		spec->type = FORMAT_TYPE_PERCENT_CHAR;
-		return ++fmt - start;
+		return ++fmt;
 
 	/* integer number formats - set up the flags and "break" */
 	case 'o':
@@ -2697,7 +2697,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 	default:
 		WARN_ONCE(1, "Please remove unsupported %%%c in format string\n", *fmt);
 		spec->type = FORMAT_TYPE_INVALID;
-		return fmt - start;
+		return fmt;
 	}
 
 	if (qualifier == 'L')
@@ -2716,7 +2716,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 		spec->type = FORMAT_TYPE_SIZE(int);
 	}
 
-	return ++fmt - start;
+	return ++fmt;
 }
 
 static void
@@ -2803,14 +2803,14 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
 
 	while (*fmt) {
 		const char *old_fmt = fmt;
-		int read = format_decode(fmt, &spec);
 
-		fmt += read;
+		fmt = format_decode(fmt, &spec);
 
 		switch (spec.type) {
 		case FORMAT_TYPE_NONE: {
-			int copy = read;
+			int read = fmt - old_fmt;
 			if (str < end) {
+				int copy = read;
 				if (copy > end - str)
 					copy = end - str;
 				memcpy(str, old_fmt, copy);
@@ -3089,9 +3089,7 @@ int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args)
 })
 
 	while (*fmt) {
-		int read = format_decode(fmt, &spec);
-
-		fmt += read;
+		fmt = format_decode(fmt, &spec);
 
 		switch (spec.type) {
 		case FORMAT_TYPE_NONE:
@@ -3233,15 +3231,14 @@ int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf)
 
 	while (*fmt) {
 		const char *old_fmt = fmt;
-		int read = format_decode(fmt, &spec);
 		unsigned long long num;
 
-		fmt += read;
-
+		fmt = format_decode(fmt, &spec);
 		switch (spec.type) {
 		case FORMAT_TYPE_NONE: {
-			int copy = read;
+			int read = fmt - old_fmt;
 			if (str < end) {
+				int copy = read;
 				if (copy > end - str)
 					copy = end - str;
 				memcpy(str, old_fmt, copy);