1 files changed, 54 insertions, 25 deletions

diff --git a/kernel/lib/string_helpers.c b/kernel/lib/string_helpers.c
index c98ae818e..5c88204b6 100644
--- a/kernel/lib/string_helpers.c
+++ b/kernel/lib/string_helpers.c
@@ -43,46 +43,73 @@ void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
 		[STRING_UNITS_10] = 1000,
 		[STRING_UNITS_2] = 1024,
 	};
-	int i, j;
-	u32 remainder = 0, sf_cap, exp;
+	static const unsigned int rounding[] = { 500, 50, 5 };
+	int i = 0, j;
+	u32 remainder = 0, sf_cap;
 	char tmp[8];
 	const char *unit;
 
 	tmp[0] = '\0';
-	i = 0;
-	if (!size)
+
+	if (blk_size == 0)
+		size = 0;
+	if (size == 0)
 		goto out;
 
-	while (blk_size >= divisor[units]) {
-		remainder = do_div(blk_size, divisor[units]);
+	/* This is Napier's algorithm.  Reduce the original block size to
+	 *
+	 * coefficient * divisor[units]^i
+	 *
+	 * we do the reduction so both coefficients are just under 32 bits so
+	 * that multiplying them together won't overflow 64 bits and we keep
+	 * as much precision as possible in the numbers.
+	 *
+	 * Note: it's safe to throw away the remainders here because all the
+	 * precision is in the coefficients.
+	 */
+	while (blk_size >> 32) {
+		do_div(blk_size, divisor[units]);
 		i++;
 	}
 
-	exp = divisor[units] / (u32)blk_size;
-	if (size >= exp) {
-		remainder = do_div(size, divisor[units]);
-		remainder *= blk_size;
+	while (size >> 32) {
+		do_div(size, divisor[units]);
 		i++;
-	} else {
-		remainder *= size;
 	}
 
+	/* now perform the actual multiplication keeping i as the sum of the
+	 * two logarithms */
 	size *= blk_size;
-	size += remainder / divisor[units];
-	remainder %= divisor[units];
 
+	/* and logarithmically reduce it until it's just under the divisor */
 	while (size >= divisor[units]) {
 		remainder = do_div(size, divisor[units]);
 		i++;
 	}
 
+	/* work out in j how many digits of precision we need from the
+	 * remainder */
 	sf_cap = size;
 	for (j = 0; sf_cap*10 < 1000; j++)
 		sf_cap *= 10;
 
-	if (j) {
+	if (units == STRING_UNITS_2) {
+		/* express the remainder as a decimal.  It's currently the
+		 * numerator of a fraction whose denominator is
+		 * divisor[units], which is 1 << 10 for STRING_UNITS_2 */
 		remainder *= 1000;
-		remainder /= divisor[units];
+		remainder >>= 10;
+	}
+
+	/* add a 5 to the digit below what will be printed to ensure
+	 * an arithmetical round up and carry it through to size */
+	remainder += rounding[j];
+	if (remainder >= 1000) {
+		remainder -= 1000;
+		size += 1;
+	}
+
+	if (j) {
 		snprintf(tmp, sizeof(tmp), ".%03u", remainder);
 		tmp[j+1] = '\0';
 	}
@@ -410,7 +437,7 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
  * @dst:	destination buffer (escaped)
  * @osz:	destination buffer size
  * @flags:	combination of the flags (bitwise OR):
- *	%ESCAPE_SPACE:
+ *	%ESCAPE_SPACE: (special white space, not space itself)
  *		'\f' - form feed
  *		'\n' - new line
  *		'\r' - carriage return
@@ -432,16 +459,18 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
  *		all previous together
  *	%ESCAPE_HEX:
  *		'\xHH' - byte with hexadecimal value HH (2 digits)
- * @esc:	NULL-terminated string of characters any of which, if found in
- *		the source, has to be escaped
+ * @only:	NULL-terminated string containing characters used to limit
+ *		the selected escape class. If characters are included in @only
+ *		that would not normally be escaped by the classes selected
+ *		in @flags, they will be copied to @dst unescaped.
  *
  * Description:
  * The process of escaping byte buffer includes several parts. They are applied
  * in the following sequence.
  *	1. The character is matched to the printable class, if asked, and in
  *	   case of match it passes through to the output.
- *	2. The character is not matched to the one from @esc string and thus
- *	   must go as is to the output.
+ *	2. The character is not matched to the one from @only string and thus
+ *	   must go as-is to the output.
  *	3. The character is checked if it falls into the class given by @flags.
  *	   %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
  *	   character. Note that they actually can't go together, otherwise
@@ -458,11 +487,11 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
  * dst for a '\0' terminator if and only if ret < osz.
  */
 int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
-		      unsigned int flags, const char *esc)
+		      unsigned int flags, const char *only)
 {
 	char *p = dst;
 	char *end = p + osz;
-	bool is_dict = esc && *esc;
+	bool is_dict = only && *only;
 
 	while (isz--) {
 		unsigned char c = *src++;
@@ -471,7 +500,7 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
 		 * Apply rules in the following sequence:
 		 *	- the character is printable, when @flags has
 		 *	  %ESCAPE_NP bit set
-		 *	- the @esc string is supplied and does not contain a
+		 *	- the @only string is supplied and does not contain a
 		 *	  character under question
 		 *	- the character doesn't fall into a class of symbols
 		 *	  defined by given @flags
@@ -479,7 +508,7 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
 		 * output buffer.
 		 */
 		if ((flags & ESCAPE_NP && isprint(c)) ||
-		    (is_dict && !strchr(esc, c))) {
+		    (is_dict && !strchr(only, c))) {
 			/* do nothing */
 		} else {
 			if (flags & ESCAPE_SPACE && escape_space(c, &p, end))