Add custom (faster) vfprintf implementation (disabled by default)

* defs.h: Declare strace_vfprintf either as a alias to vfprintf
or as a bona fide function. USE_CUSTOM_PRINTF define controls whether
we use strace_vfprintf. By default, we don't.
* strace.c (tprintf): Call strace_vfprintf instead of vfprintf.
* vsprintf.c: New file, implements strace_vfprintf.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 783 insertions, 0 deletions

diff --git a/vsprintf.c b/vsprintf.c
new file mode 100644
index 0000000..71bdf8c
--- /dev/null
+++ b/vsprintf.c
@@ -0,0 +1,783 @@
+/*
+ * Taken from Linux kernel's linux/lib/vsprintf.c
+ * and somewhat simplified.
+ *
+ * Copyright (C) 1991, 1992  Linus Torvalds
+ */
+/* vsprintf.c -- Lars Wirzenius & Linus Torvalds. */
+/*
+ * Wirzenius wrote this portably, Torvalds fucked it up :-)
+ */
+
+#include "defs.h"
+#include <stdarg.h>
+#include <limits.h>
+
+#ifdef USE_CUSTOM_PRINTF
+
+#define noinline_for_stack /*nothing*/
+#define likely(expr)       (expr)
+#define unlikely(expr)     (expr)
+
+#define do_div(n, d)       ({ __typeof(num) t = n % d; n /= d; t; })
+
+#undef isdigit
+#define isdigit(a) ((unsigned char)((a) - '0') <= 9)
+
+static inline
+int skip_atoi(const char **s)
+{
+	int i = 0;
+	const char *p = *s;
+
+	while (isdigit(*p))
+		i = i*10 + *p++ - '0';
+
+	*s = p;
+	return i;
+}
+
+/* Decimal conversion is by far the most typical, and is used
+ * for /proc and /sys data. This directly impacts e.g. top performance
+ * with many processes running. We optimize it for speed
+ * using ideas described at <http://www.cs.uiowa.edu/~jones/bcd/divide.html>
+ * (with permission from the author, Douglas W. Jones).
+ */
+
+#if LONG_MAX != 0x7fffffffUL || LLONG_MAX != 0x7fffffffffffffffULL
+/* Formats correctly any integer in [0, 999999999] */
+static noinline_for_stack
+char *put_dec_full9(char *buf, unsigned q)
+{
+	unsigned r;
+
+	/* Possible ways to approx. divide by 10
+	 * (x * 0x1999999a) >> 32 x < 1073741829 (multiply must be 64-bit)
+	 * (x * 0xcccd) >> 19     x <      81920 (x < 262149 when 64-bit mul)
+	 * (x * 0x6667) >> 18     x <      43699
+	 * (x * 0x3334) >> 17     x <      16389
+	 * (x * 0x199a) >> 16     x <      16389
+	 * (x * 0x0ccd) >> 15     x <      16389
+	 * (x * 0x0667) >> 14     x <       2739
+	 * (x * 0x0334) >> 13     x <       1029
+	 * (x * 0x019a) >> 12     x <       1029
+	 * (x * 0x00cd) >> 11     x <       1029 shorter code than * 0x67 (on i386)
+	 * (x * 0x0067) >> 10     x <        179
+	 * (x * 0x0034) >>  9     x <         69 same
+	 * (x * 0x001a) >>  8     x <         69 same
+	 * (x * 0x000d) >>  7     x <         69 same, shortest code (on i386)
+	 * (x * 0x0007) >>  6     x <         19
+	 * See <http://www.cs.uiowa.edu/~jones/bcd/divide.html>
+	 */
+	r      = (q * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (q - 10 * r) + '0'; /* 1 */
+	q      = (r * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (r - 10 * q) + '0'; /* 2 */
+	r      = (q * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (q - 10 * r) + '0'; /* 3 */
+	q      = (r * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (r - 10 * q) + '0'; /* 4 */
+	r      = (q * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (q - 10 * r) + '0'; /* 5 */
+	/* Now value is under 10000, can avoid 64-bit multiply */
+	q      = (r * 0x199a) >> 16;
+	*buf++ = (r - 10 * q)  + '0'; /* 6 */
+	r      = (q * 0xcd) >> 11;
+	*buf++ = (q - 10 * r)  + '0'; /* 7 */
+	q      = (r * 0xcd) >> 11;
+	*buf++ = (r - 10 * q) + '0'; /* 8 */
+	*buf++ = q + '0'; /* 9 */
+	return buf;
+}
+#endif
+
+/* Similar to above but do not pad with zeros.
+ * Code can be easily arranged to print 9 digits too, but our callers
+ * always call put_dec_full9() instead when the number has 9 decimal digits.
+ */
+static noinline_for_stack
+char *put_dec_trunc8(char *buf, unsigned r)
+{
+	unsigned q;
+
+	/* Copy of previous function's body with added early returns */
+	q      = (r * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (r - 10 * q) + '0'; /* 2 */
+	if (q == 0) return buf;
+	r      = (q * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (q - 10 * r) + '0'; /* 3 */
+	if (r == 0) return buf;
+	q      = (r * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (r - 10 * q) + '0'; /* 4 */
+	if (q == 0) return buf;
+	r      = (q * (uint64_t)0x1999999a) >> 32;
+	*buf++ = (q - 10 * r) + '0'; /* 5 */
+	if (r == 0) return buf;
+	q      = (r * 0x199a) >> 16;
+	*buf++ = (r - 10 * q)  + '0'; /* 6 */
+	if (q == 0) return buf;
+	r      = (q * 0xcd) >> 11;
+	*buf++ = (q - 10 * r)  + '0'; /* 7 */
+	if (r == 0) return buf;
+	q      = (r * 0xcd) >> 11;
+	*buf++ = (r - 10 * q) + '0'; /* 8 */
+	if (q == 0) return buf;
+	*buf++ = q + '0'; /* 9 */
+	return buf;
+}
+
+/* There are two algorithms to print larger numbers.
+ * One is generic: divide by 1000000000 and repeatedly print
+ * groups of (up to) 9 digits. It's conceptually simple,
+ * but requires a (unsigned long long) / 1000000000 division.
+ *
+ * Second algorithm splits 64-bit unsigned long long into 16-bit chunks,
+ * manipulates them cleverly and generates groups of 4 decimal digits.
+ * It so happens that it does NOT require long long division.
+ *
+ * If long is > 32 bits, division of 64-bit values is relatively easy,
+ * and we will use the first algorithm.
+ * If long long is > 64 bits (strange architecture with VERY large long long),
+ * second algorithm can't be used, and we again use the first one.
+ *
+ * Else (if long is 32 bits and long long is 64 bits) we use second one.
+ */
+
+#if LONG_MAX != 0x7fffffffUL || LLONG_MAX != 0x7fffffffffffffffULL
+
+/* First algorithm: generic */
+
+static
+char *put_dec(char *buf, unsigned long long n)
+{
+	if (n >= 100*1000*1000) {
+		while (n >= 1000*1000*1000)
+			buf = put_dec_full9(buf, do_div(n, 1000*1000*1000));
+		if (n >= 100*1000*1000)
+			return put_dec_full9(buf, n);
+	}
+	return put_dec_trunc8(buf, n);
+}
+
+#else
+
+/* Second algorithm: valid only for 64-bit long longs */
+
+static noinline_for_stack
+char *put_dec_full4(char *buf, unsigned q)
+{
+	unsigned r;
+	r      = (q * 0xcccd) >> 19;
+	*buf++ = (q - 10 * r) + '0';
+	q      = (r * 0x199a) >> 16;
+	*buf++ = (r - 10 * q)  + '0';
+	r      = (q * 0xcd) >> 11;
+	*buf++ = (q - 10 * r)  + '0';
+	*buf++ = r + '0';
+	return buf;
+}
+
+/* Based on code by Douglas W. Jones found at
+ * <http://www.cs.uiowa.edu/~jones/bcd/decimal.html#sixtyfour>
+ * (with permission from the author).
+ * Performs no 64-bit division and hence should be fast on 32-bit machines.
+ */
+static
+char *put_dec(char *buf, unsigned long long n)
+{
+	uint32_t d3, d2, d1, q, h;
+
+	if (n < 100*1000*1000)
+		return put_dec_trunc8(buf, n);
+
+	d1  = ((uint32_t)n >> 16); /* implicit "& 0xffff" */
+	h   = (n >> 32);
+	d2  = (h      ) & 0xffff;
+	d3  = (h >> 16); /* implicit "& 0xffff" */
+
+	q   = 656 * d3 + 7296 * d2 + 5536 * d1 + ((uint32_t)n & 0xffff);
+
+	buf = put_dec_full4(buf, q % 10000);
+	q   = q / 10000;
+
+	d1  = q + 7671 * d3 + 9496 * d2 + 6 * d1;
+	buf = put_dec_full4(buf, d1 % 10000);
+	q   = d1 / 10000;
+
+	d2  = q + 4749 * d3 + 42 * d2;
+	buf = put_dec_full4(buf, d2 % 10000);
+	q   = d2 / 10000;
+
+	d3  = q + 281 * d3;
+	if (!d3)
+		goto done;
+	buf = put_dec_full4(buf, d3 % 10000);
+	q   = d3 / 10000;
+	if (!q)
+		goto done;
+	buf = put_dec_full4(buf, q);
+ done:
+	while (buf[-1] == '0')
+		--buf;
+
+	return buf;
+}
+
+#endif
+
+/*
+ * For strace, the following formats are not supported:
+ * %h[h]u, %zu, %tu  - use [unsigned] int/long/long long fmt instead
+ * %8.4u  - no precision field for integers allowed (ok for strings)
+ * %+d, % d  - no forced sign or force "space positive" sign
+ * %-07u  - use %-7u instead
+ * %X  - works as %x
+ */
+
+#define ZEROPAD	1		/* pad with zero */
+#define SIGN	2		/* unsigned/signed long */
+//#define PLUS	4		/* show plus */
+//#define SPACE	8		/* space if plus */
+#define LEFT	16		/* left justified */
+//#deefine SMALL	32		/* use lowercase in hex (must be 32 == 0x20) */
+#define SPECIAL	64		/* prefix hex with "0x", octal with "0" */
+
+enum format_type {
+	FORMAT_TYPE_NONE, /* Just a string part */
+	FORMAT_TYPE_WIDTH,
+	FORMAT_TYPE_PRECISION,
+	FORMAT_TYPE_CHAR,
+	FORMAT_TYPE_STR,
+	FORMAT_TYPE_PTR,
+	FORMAT_TYPE_PERCENT_CHAR,
+	FORMAT_TYPE_INVALID,
+	FORMAT_TYPE_LONG_LONG,
+	FORMAT_TYPE_ULONG,
+	FORMAT_TYPE_LONG,
+	FORMAT_TYPE_UINT,
+	FORMAT_TYPE_INT,
+};
+
+struct printf_spec {
+	uint8_t	type;		/* format_type enum */
+	uint8_t	flags;		/* flags to number() */
+	uint8_t	base;		/* number base, 8, 10 or 16 only */
+	uint8_t	qualifier;	/* number qualifier, one of 'hHlLtzZ' */
+	int	field_width;	/* width of output field */
+	int	precision;	/* # of digits/chars */
+};
+
+static noinline_for_stack
+char *number(char *buf, char *end, unsigned long long num,
+	     struct printf_spec spec)
+{
+	/* we are called with base 8, 10 or 16, only, thus don't need "G..."  */
+	static const char digits[16] = "0123456789abcdef"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
+
+	char tmp[sizeof(long long)*3 + 4];
+	char sign;
+	int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10);
+	int i;
+
+	/* We may overflow the buf. Crudely check for it */
+	i = sizeof(long long)*3 + 4;
+	if (i < spec.field_width)
+		i = spec.field_width;
+	if ((end - buf) <= i)
+		return buf + i;
+
+//we don't use formats like "%-07u"
+//	if (spec.flags & LEFT)
+//		spec.flags &= ~ZEROPAD;
+	sign = 0;
+	if (spec.flags & SIGN) {
+		if ((signed long long)num < 0) {
+			sign = '-';
+			num = -(signed long long)num;
+			spec.field_width--;
+//		} else if (spec.flags & PLUS) {
+//			sign = '+';
+//			spec.field_width--;
+//		} else if (spec.flags & SPACE) {
+//			sign = ' ';
+//			spec.field_width--;
+		}
+	}
+	if (need_pfx) {
+		spec.field_width--;
+		if (spec.base == 16)
+			spec.field_width--;
+	}
+
+	/* generate full string in tmp[], in reverse order */
+	i = 0;
+	if (num < spec.base)
+		tmp[i++] = digits[num];
+	/* Generic code, for any base:
+	else do {
+		tmp[i++] = (digits[do_div(num,base)]);
+	} while (num != 0);
+	*/
+	else if (spec.base != 10) { /* 8 or 16 */
+		int mask = spec.base - 1;
+		int shift = 3;
+
+		if (spec.base == 16)
+			shift = 4;
+		do {
+			tmp[i++] = digits[((unsigned char)num) & mask];
+			num >>= shift;
+		} while (num);
+	} else { /* base 10 */
+		i = put_dec(tmp, num) - tmp;
+	}
+
+//spec.precision is assumed 0 ("not specified")
+//	/* printing 100 using %2d gives "100", not "00" */
+//	if (i > spec.precision)
+//		spec.precision = i;
+//	/* leading space padding */
+//	spec.field_width -= spec.precision;
+	spec.field_width -= i;
+	if (!(spec.flags & (ZEROPAD+LEFT))) {
+		while (--spec.field_width >= 0) {
+			///if (buf < end)
+				*buf = ' ';
+			++buf;
+		}
+	}
+	/* sign */
+	if (sign) {
+		///if (buf < end)
+			*buf = sign;
+		++buf;
+	}
+	/* "0x" / "0" prefix */
+	if (need_pfx) {
+		///if (buf < end)
+			*buf = '0';
+		++buf;
+		if (spec.base == 16) {
+			///if (buf < end)
+				*buf = 'x';
+			++buf;
+		}
+	}
+	/* zero or space padding */
+	if (!(spec.flags & LEFT)) {
+		char c = (spec.flags & ZEROPAD) ? '0' : ' ';
+		while (--spec.field_width >= 0) {
+			///if (buf < end)
+				*buf = c;
+			++buf;
+		}
+	}
+//	/* hmm even more zero padding? */
+//	while (i <= --spec.precision) {
+//		///if (buf < end)
+//			*buf = '0';
+//		++buf;
+//	}
+	/* actual digits of result */
+	while (--i >= 0) {
+		///if (buf < end)
+			*buf = tmp[i];
+		++buf;
+	}
+	/* trailing space padding */
+	while (--spec.field_width >= 0) {
+		///if (buf < end)
+			*buf = ' ';
+		++buf;
+	}
+
+	return buf;
+}
+
+static noinline_for_stack
+char *string(char *buf, char *end, const char *s, struct printf_spec spec)
+{
+	int len, i;
+
+	if (!s)
+		s = "(null)";
+
+	len = strnlen(s, spec.precision);
+
+	/* We may overflow the buf. Crudely check for it */
+	i = len;
+	if (i < spec.field_width)
+		i = spec.field_width;
+	if ((end - buf) <= i)
+		return buf + i;
+
+	if (!(spec.flags & LEFT)) {
+		while (len < spec.field_width--) {
+			///if (buf < end)
+				*buf = ' ';
+			++buf;
+		}
+	}
+	for (i = 0; i < len; ++i) {
+		///if (buf < end)
+			*buf = *s;
+		++buf; ++s;
+	}
+	while (len < spec.field_width--) {
+		///if (buf < end)
+			*buf = ' ';
+		++buf;
+	}
+
+	return buf;
+}
+
+static noinline_for_stack
+char *pointer(const char *fmt, char *buf, char *end, void *ptr,
+	      struct printf_spec spec)
+{
+//	spec.flags |= SMALL;
+	if (spec.field_width == -1) {
+		spec.field_width = 2 * sizeof(void *);
+		spec.flags |= ZEROPAD;
+	}
+	spec.base = 16;
+
+	return number(buf, end, (unsigned long) ptr, spec);
+}
+
+/*
+ * Helper function to decode printf style format.
+ * Each call decode a token from the format and return the
+ * number of characters read (or likely the delta where it wants
+ * to go on the next call).
+ * The decoded token is returned through the parameters
+ *
+ * 'h', 'l', or 'L' for integer fields
+ * 'z' support added 23/7/1999 S.H.
+ * 'z' changed to 'Z' --davidm 1/25/99
+ * 't' added for ptrdiff_t
+ *
+ * @fmt: the format string
+ * @type of the token returned
+ * @flags: various flags such as +, -, # tokens..
+ * @field_width: overwritten width
+ * @base: base of the number (octal, hex, ...)
+ * @precision: precision of a number
+ * @qualifier: qualifier of a number (long, size_t, ...)
+ */
+static noinline_for_stack
+int format_decode(const char *fmt, struct printf_spec *spec)
+{
+	const char *start = fmt;
+
+	/* we finished early by reading the field width */
+	if (spec->type == FORMAT_TYPE_WIDTH) {
+		if (spec->field_width < 0) {
+			spec->field_width = -spec->field_width;
+			spec->flags |= LEFT;
+		}
+		spec->type = FORMAT_TYPE_NONE;
+		goto precision;
+	}
+
+	/* we finished early by reading the precision */
+	if (spec->type == FORMAT_TYPE_PRECISION) {
+		if (spec->precision < 0)
+			spec->precision = 0;
+
+		spec->type = FORMAT_TYPE_NONE;
+		goto qualifier;
+	}
+
+	/* By default */
+	spec->type = FORMAT_TYPE_NONE;
+
+	for (;;) {
+		if (*fmt == '\0')
+			return fmt - start;
+		if (*fmt == '%')
+			break;
+		++fmt;
+	}
+
+	/* Return the current non-format string */
+	if (fmt != start)
+		return fmt - start;
+
+	/* Process flags */
+	spec->flags = 0;
+
+	while (1) { /* this also skips first '%' */
+		bool found = true;
+
+		++fmt;
+
+		switch (*fmt) {
+		case '-': spec->flags |= LEFT;    break;
+//		case '+': spec->flags |= PLUS;    break;
+//		case ' ': spec->flags |= SPACE;   break;
+		case '#': spec->flags |= SPECIAL; break;
+		case '0': spec->flags |= ZEROPAD; break;
+		default:  found = false;
+		}
+
+		if (!found)
+			break;
+	}
+
+	/* get field width */
+	spec->field_width = -1;
+
+	if (isdigit(*fmt))
+		spec->field_width = skip_atoi(&fmt);
+	else if (*fmt == '*') {
+		/* it's the next argument */
+		spec->type = FORMAT_TYPE_WIDTH;
+		return ++fmt - start;
+	}
+
+precision:
+	/* get the precision */
+	spec->precision = -1;
+	if (*fmt == '.') {
+		++fmt;
+		if (isdigit(*fmt)) {
+			spec->precision = skip_atoi(&fmt);
+//			if (spec->precision < 0)
+//				spec->precision = 0;
+		} else if (*fmt == '*') {
+			/* it's the next argument */
+			spec->type = FORMAT_TYPE_PRECISION;
+			return ++fmt - start;
+		}
+	}
+
+qualifier:
+	/* get the conversion qualifier */
+	spec->qualifier = -1;
+	if (*fmt == 'l') {
+		spec->qualifier = *fmt++;
+		if (unlikely(spec->qualifier == *fmt)) {
+			spec->qualifier = 'L';
+			++fmt;
+		}
+	}
+
+	/* default base */
+	spec->base = 10;
+	switch (*fmt) {
+	case 'c':
+		spec->type = FORMAT_TYPE_CHAR;
+		return ++fmt - start;
+
+	case 's':
+		spec->type = FORMAT_TYPE_STR;
+		return ++fmt - start;
+
+	case 'p':
+		spec->type = FORMAT_TYPE_PTR;
+		return ++fmt - start;
+
+	case '%':
+		spec->type = FORMAT_TYPE_PERCENT_CHAR;
+		return ++fmt - start;
+
+	/* integer number formats - set up the flags and "break" */
+	case 'o':
+		spec->base = 8;
+		break;
+
+	case 'x':
+//		spec->flags |= SMALL;
+
+	case 'X':
+		spec->base = 16;
+		break;
+
+	case 'd':
+	case 'i':
+		spec->flags |= SIGN;
+	case 'u':
+		break;
+
+	default:
+		spec->type = FORMAT_TYPE_INVALID;
+		return fmt - start;
+	}
+
+	if (spec->qualifier == 'L')
+		spec->type = FORMAT_TYPE_LONG_LONG;
+	else if (spec->qualifier == 'l') {
+		if (spec->flags & SIGN)
+			spec->type = FORMAT_TYPE_LONG;
+		else
+			spec->type = FORMAT_TYPE_ULONG;
+	} else {
+		if (spec->flags & SIGN)
+			spec->type = FORMAT_TYPE_INT;
+		else
+			spec->type = FORMAT_TYPE_UINT;
+	}
+
+	return ++fmt - start;
+}
+
+/**
+ * vsnprintf - Format a string and place it in a buffer
+ * @buf: The buffer to place the result into
+ * @size: The size of the buffer, including the trailing null space
+ * @fmt: The format string to use
+ * @args: Arguments for the format string
+ *
+ * The return value is the number of characters which would
+ * be generated for the given input, excluding the trailing
+ * '\0', as per ISO C99. If you want to have the exact
+ * number of characters written into @buf as return value
+ * (not including the trailing '\0'), use vscnprintf(). If the
+ * return is greater than or equal to @size, the resulting
+ * string is truncated.
+ *
+ * If you're not already dealing with a va_list consider using snprintf().
+ */
+static
+int kernel_vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
+{
+	unsigned long long num;
+	char *str, *end;
+	struct printf_spec spec = {0};
+
+	str = buf;
+	end = buf + size;
+
+	while (*fmt) {
+		const char *old_fmt = fmt;
+		int read = format_decode(fmt, &spec);
+
+		fmt += read;
+
+		switch (spec.type) {
+		case FORMAT_TYPE_NONE: {
+			int copy = read;
+			if (str < end) {
+				if (copy > end - str)
+					copy = end - str;
+				memcpy(str, old_fmt, copy);
+			}
+			str += read;
+			break;
+		}
+
+		case FORMAT_TYPE_WIDTH:
+			spec.field_width = va_arg(args, int);
+			break;
+
+		case FORMAT_TYPE_PRECISION:
+			spec.precision = va_arg(args, int);
+			break;
+
+		case FORMAT_TYPE_CHAR: {
+			char c;
+
+			if (!(spec.flags & LEFT)) {
+				while (--spec.field_width > 0) {
+					if (str < end)
+						*str = ' ';
+					++str;
+
+				}
+			}
+			c = (unsigned char) va_arg(args, int);
+			if (str < end)
+				*str = c;
+			++str;
+			while (--spec.field_width > 0) {
+				if (str < end)
+					*str = ' ';
+				++str;
+			}
+			break;
+		}
+
+		case FORMAT_TYPE_STR:
+			str = string(str, end, va_arg(args, char *), spec);
+			break;
+
+		case FORMAT_TYPE_PTR:
+			str = pointer(fmt+1, str, end, va_arg(args, void *),
+				      spec);
+//			while (isalnum(*fmt))
+//				fmt++;
+			break;
+
+		case FORMAT_TYPE_PERCENT_CHAR:
+			if (str < end)
+				*str = '%';
+			++str;
+			break;
+
+		case FORMAT_TYPE_INVALID:
+			if (str < end)
+				*str = '%';
+			++str;
+			break;
+
+		default:
+			switch (spec.type) {
+			case FORMAT_TYPE_LONG_LONG:
+				num = va_arg(args, long long);
+				break;
+			case FORMAT_TYPE_ULONG:
+				num = va_arg(args, unsigned long);
+				break;
+			case FORMAT_TYPE_LONG:
+				num = va_arg(args, long);
+				break;
+			case FORMAT_TYPE_INT:
+				num = (int) va_arg(args, int);
+				break;
+			default:
+				num = va_arg(args, unsigned int);
+			}
+
+			str = number(str, end, num, spec);
+		}
+	}
+
+//	if (size > 0) {
+		if (str < end)
+			*str = '\0';
+//		else
+//			end[-1] = '\0';
+//	}
+
+	/* the trailing null byte doesn't count towards the total */
+	return str-buf;
+
+}
+
+int strace_vfprintf(FILE *fp, const char *fmt, va_list args)
+{
+	static char *buf;
+	static unsigned buflen;
+
+	int r;
+	va_list a1;
+
+	va_copy(a1, args);
+	unsigned len = kernel_vsnprintf(buf, buflen, fmt, a1);
+	va_end(a1);
+
+	if (len >= buflen) {
+		buflen = len + 256;
+		free(buf);
+		buf = malloc(buflen);
+		/*len =*/ kernel_vsnprintf(buf, buflen, fmt, args);
+	}
+
+	r = fputs_unlocked(buf, fp);
+	if (r < 0) return r;
+	return len;
+}
+
+#endif /* USE_CUSTOM_PRINTF */