[U-Boot] [PATCH] tiny-printf: Adjust to avoid using data section

[Simon Glass]

We can pass all the variables down to the functions that need them, and
then everything is on the stack. This is safer than using the data section.

At least on firefly-rk3288, the code size is the same and the data size is
12 bytes smaller:

before:
  18865	   2636	     40	  21541	   5425	b/firefly-rk3288/spl/u-boot-spl
after:
  18865	   2624	     40	  21529	   5419	b/firefly-rk3288/spl/u-boot-spl

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 lib/tiny-printf.c | 102 +++++++++++++++++++++++++++++++-----------------------
 1 file changed, 58 insertions(+), 44 deletions(-)

diff --git a/lib/tiny-printf.c b/lib/tiny-printf.c
index 1aa43ab..30ac759 100644
--- a/lib/tiny-printf.c
+++ b/lib/tiny-printf.c
@@ -13,29 +13,33 @@
 #include <stdarg.h>
 #include <serial.h>
 
-/*
- * This code in here may execute before the DRAM is initialised, so
- * we should make sure that it doesn't touch BSS, which some boards
- * put in DRAM.
- */
-static char *bf __attribute__ ((section(".data")));
-static char zs __attribute__ ((section(".data")));
+struct printf_info {
+	char *bf;	/* Digit buffer */
+	char zs;	/* non-zero if a digit has been written */
+	char *outstr;	/* Next output position for sprintf() */
 
-/* Current position in sprintf() output string */
-static char *outstr __attribute__ ((section(".data")));
+	/* Output a character */
+	void (*putc)(struct printf_info *info, char ch);
+};
 
-static void out(char c)
+void putc_normal(struct printf_info *info, char ch)
 {
-	*bf++ = c;
+	putc(ch);
 }
 
-static void out_dgt(char dgt)
+static void out(struct printf_info *info, char c)
 {
-	out(dgt + (dgt < 10 ? '0' : 'a' - 10));
-	zs = 1;
+	*info->bf++ = c;
 }
 
-static void div_out(unsigned int *num, unsigned int div)
+static void out_dgt(struct printf_info *info, char dgt)
+{
+	out(info, dgt + (dgt < 10 ? '0' : 'a' - 10));
+	info->zs = 1;
+}
+
+static void div_out(struct printf_info *info, unsigned int *num,
+		    unsigned int div)
 {
 	unsigned char dgt = 0;
 
@@ -44,11 +48,11 @@ static void div_out(unsigned int *num, unsigned int div)
 		dgt++;
 	}
 
-	if (zs || dgt > 0)
-		out_dgt(dgt);
+	if (info->zs || dgt > 0)
+		out_dgt(info, dgt);
 }
 
-int _vprintf(const char *fmt, va_list va, void (*putc)(const char ch))
+int _vprintf(struct printf_info *info, const char *fmt, va_list va)
 {
 	char ch;
 	char *p;
@@ -58,7 +62,7 @@ int _vprintf(const char *fmt, va_list va, void (*putc)(const char ch))
 
 	while ((ch = *(fmt++))) {
 		if (ch != '%') {
-			putc(ch);
+			info->putc(info, ch);
 		} else {
 			bool lz = false;
 			int width = 0;
@@ -76,9 +80,9 @@ int _vprintf(const char *fmt, va_list va, void (*putc)(const char ch))
 					ch = *fmt++;
 				}
 			}
-			bf = buf;
-			p = bf;
-			zs = 0;
+			info->bf = buf;
+			p = info->bf;
+			info->zs = 0;
 
 			switch (ch) {
 			case '\0':
@@ -88,45 +92,45 @@ int _vprintf(const char *fmt, va_list va, void (*putc)(const char ch))
 				num = va_arg(va, unsigned int);
 				if (ch == 'd' && (int)num < 0) {
 					num = -(int)num;
-					out('-');
+					out(info, '-');
 				}
 				if (!num) {
-					out_dgt(0);
+					out_dgt(info, 0);
 				} else {
 					for (div = 1000000000; div; div /= 10)
-						div_out(&num, div);
+						div_out(info, &num, div);
 				}
 				break;
 			case 'x':
 				num = va_arg(va, unsigned int);
 				if (!num) {
-					out_dgt(0);
+					out_dgt(info, 0);
 				} else {
 					for (div = 0x10000000; div; div /= 0x10)
-						div_out(&num, div);
+						div_out(info, &num, div);
 				}
 				break;
 			case 'c':
-				out((char)(va_arg(va, int)));
+				out(info, (char)(va_arg(va, int)));
 				break;
 			case 's':
 				p = va_arg(va, char*);
 				break;
 			case '%':
-				out('%');
+				out(info, '%');
 			default:
 				break;
 			}
 
-			*bf = 0;
-			bf = p;
-			while (*bf++ && width > 0)
+			*info->bf = 0;
+			info->bf = p;
+			while (*info->bf++ && width > 0)
 				width--;
 			while (width-- > 0)
-				putc(lz ? '0' : ' ');
+				info->putc(info, lz ? '0' : ' ');
 			if (p) {
 				while ((ch = *p++))
-					putc(ch);
+					info->putc(info, ch);
 			}
 		}
 	}
@@ -137,36 +141,44 @@ abort:
 
 int vprintf(const char *fmt, va_list va)
 {
-	return _vprintf(fmt, va, putc);
+	struct printf_info info;
+
+	info.putc = putc_normal;
+	return _vprintf(&info, fmt, va);
 }
 
 int printf(const char *fmt, ...)
 {
+	struct printf_info info;
+
 	va_list va;
 	int ret;
 
+	info.putc = putc_normal;
 	va_start(va, fmt);
-	ret = _vprintf(fmt, va, putc);
+	ret = _vprintf(&info, fmt, va);
 	va_end(va);
 
 	return ret;
 }
 
-static void putc_outstr(char ch)
+static void putc_outstr(struct printf_info *info, char ch)
 {
-	*outstr++ = ch;
+	*info->outstr++ = ch;
 }
 
 int sprintf(char *buf, const char *fmt, ...)
 {
+	struct printf_info info;
 	va_list va;
 	int ret;
 
 	va_start(va, fmt);
-	outstr = buf;
-	ret = _vprintf(fmt, va, putc_outstr);
+	info.outstr = buf;
+	info.putc = putc_outstr;
+	ret = _vprintf(&info, fmt, va);
 	va_end(va);
-	*outstr = '\0';
+	*info.outstr = '\0';
 
 	return ret;
 }
@@ -174,14 +186,16 @@ int sprintf(char *buf, const char *fmt, ...)
 /* Note that size is ignored */
 int snprintf(char *buf, size_t size, const char *fmt, ...)
 {
+	struct printf_info info;
 	va_list va;
 	int ret;
 
 	va_start(va, fmt);
-	outstr = buf;
-	ret = _vprintf(fmt, va, putc_outstr);
+	info.outstr = buf;
+	info.putc = putc_outstr;
+	ret = _vprintf(&info, fmt, va);
 	va_end(va);
-	*outstr = '\0';
+	*info.outstr = '\0';
 
 	return ret;
 }
-- 
2.8.0.rc3.226.g39d4020