vsprintf.c

/*
 *  linux/lib/vsprintf.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/* vsprintf.c -- Lars Wirzenius & Linus Torvalds. */
/*
 * Wirzenius wrote this portably, Torvalds fucked it up :-)
 */

/* 
 * Fri Jul 13 2001 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
 * - changed to provide snprintf and vsnprintf functions
 * So Feb  1 16:51:32 CET 2004 Juergen Quade <quade@hsnr.de>
 * - scnprintf and vscnprintf
 */

#include <stdarg.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/kernel.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/ioport.h>
#include <net/addrconf.h>

#include <asm/page.h>		/* for PAGE_SIZE */
#include <asm/div64.h>
#include <asm/sections.h>	/* for dereference_function_descriptor() */

/* Works only for digits and letters, but small and fast */
#define TOLOWER(x) ((x) | 0x20)

static unsigned int simple_guess_base(const char *cp)
{
	if (cp[0] == '0') {
		if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
			return 16;
		else
			return 8;
	} else {
		return 10;
	}
}

/**
 * simple_strtoul - convert a string to an unsigned long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base)
{
	unsigned long result = 0;

	if (!base)
		base = simple_guess_base(cp);

	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
		cp += 2;

	while (isxdigit(*cp)) {
		unsigned int value;

		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
		if (value >= base)
			break;
		result = result * base + value;
		cp++;
	}

	if (endp)
		*endp = (char *)cp;
	return result;
}
EXPORT_SYMBOL(simple_strtoul);

/**
 * simple_strtol - convert a string to a signed long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
long simple_strtol(const char *cp, char **endp, unsigned int base)
{
	if(*cp == '-')
		return -simple_strtoul(cp + 1, endp, base);
	return simple_strtoul(cp, endp, base);
}
EXPORT_SYMBOL(simple_strtol);

/**
 * simple_strtoull - convert a string to an unsigned long long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
{
	unsigned long long result = 0;

	if (!base)
		base = simple_guess_base(cp);

	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
		cp += 2;

	while (isxdigit(*cp)) {
		unsigned int value;

		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
		if (value >= base)
			break;
		result = result * base + value;
		cp++;
	}

	if (endp)
		*endp = (char *)cp;
	return result;
}
EXPORT_SYMBOL(simple_strtoull);

/**
 * simple_strtoll - convert a string to a signed long long
 * @cp: The start of the string
 * @endp: A pointer to the end of the parsed string will be placed here
 * @base: The number base to use
 */
long long simple_strtoll(const char *cp, char **endp, unsigned int base)
{
	if(*cp=='-')
		return -simple_strtoull(cp + 1, endp, base);
	return simple_strtoull(cp, endp, base);
}

/**
 * strict_strtoul - convert a string to an unsigned long strictly
 * @cp: The string to be converted
 * @base: The number base to use
 * @res: The converted result value
 *
 * strict_strtoul converts a string to an unsigned long only if the
 * string is really an unsigned long string, any string containing
 * any invalid char at the tail will be rejected and -EINVAL is returned,
 * only a newline char at the tail is acceptible because people generally
 * change a module parameter in the following way:
 *
 * 	echo 1024 > /sys/module/e1000/parameters/copybreak
 *
 * echo will append a newline to the tail.
 *
 * It returns 0 if conversion is successful and *res is set to the converted
 * value, otherwise it returns -EINVAL and *res is set to 0.
 *
 * simple_strtoul just ignores the successive invalid characters and
 * return the converted value of prefix part of the string.
 */
int strict_strtoul(const char *cp, unsigned int base, unsigned long *res)
{
	char *tail;
	unsigned long val;
	size_t len;

	*res = 0;
	len = strlen(cp);
	if (len == 0)
		return -EINVAL;

	val = simple_strtoul(cp, &tail, base);
	if (tail == cp)
		return -EINVAL;
	if ((*tail == '\0') ||
		((len == (size_t)(tail - cp) + 1) && (*tail == '\n'))) {
		*res = val;
		return 0;
	}

	return -EINVAL;
}
EXPORT_SYMBOL(strict_strtoul);

/**
 * strict_strtol - convert a string to a long strictly
 * @cp: The string to be converted
 * @base: The number base to use
 * @res: The converted result value
 *
 * strict_strtol is similiar to strict_strtoul, but it allows the first
 * character of a string is '-'.
 *
 * It returns 0 if conversion is successful and *res is set to the converted
 * value, otherwise it returns -EINVAL and *res is set to 0.
 */
int strict_strtol(const char *cp, unsigned int base, long *res)
{
	int ret;
	if (*cp == '-') {
		ret = strict_strtoul(cp + 1, base, (unsigned long *)res);
		if (!ret)
			*res = -(*res);
	} else {
		ret = strict_strtoul(cp, base, (unsigned long *)res);
	}

	return ret;
}
EXPORT_SYMBOL(strict_strtol);

/**
 * strict_strtoull - convert a string to an unsigned long long strictly
 * @cp: The string to be converted
 * @base: The number base to use
 * @res: The converted result value
 *
 * strict_strtoull converts a string to an unsigned long long only if the
 * string is really an unsigned long long string, any string containing
 * any invalid char at the tail will be rejected and -EINVAL is returned,
 * only a newline char at the tail is acceptible because people generally
 * change a module parameter in the following way:
 *
 * 	echo 1024 > /sys/module/e1000/parameters/copybreak
 *
 * echo will append a newline to the tail of the string.
 *
 * It returns 0 if conversion is successful and *res is set to the converted
 * value, otherwise it returns -EINVAL and *res is set to 0.
 *
 * simple_strtoull just ignores the successive invalid characters and
 * return the converted value of prefix part of the string.
 */
int strict_strtoull(const char *cp, unsigned int base, unsigned long long *res)
{
	char *tail;
	unsigned long long val;
	size_t len;

	*res = 0;
	len = strlen(cp);
	if (len == 0)
		return -EINVAL;

	val = simple_strtoull(cp, &tail, base);
	if (tail == cp)
		return -EINVAL;
	if ((*tail == '\0') ||
		((len == (size_t)(tail - cp) + 1) && (*tail == '\n'))) {
		*res = val;
		return 0;
	}

	return -EINVAL;
}
EXPORT_SYMBOL(strict_strtoull);

/**
 * strict_strtoll - convert a string to a long long strictly
 * @cp: The string to be converted
 * @base: The number base to use
 * @res: The converted result value
 *
 * strict_strtoll is similiar to strict_strtoull, but it allows the first
 * character of a string is '-'.
 *
 * It returns 0 if conversion is successful and *res is set to the converted
 * value, otherwise it returns -EINVAL and *res is set to 0.
 */
int strict_strtoll(const char *cp, unsigned int base, long long *res)
{
	int ret;
	if (*cp == '-') {
		ret = strict_strtoull(cp + 1, base, (unsigned long long *)res);
		if (!ret)
			*res = -(*res);
	} else {
		ret = strict_strtoull(cp, base, (unsigned long long *)res);
	}

	return ret;
}
EXPORT_SYMBOL(strict_strtoll);

static int skip_atoi(const char **s)
{
	int i=0;

	while (isdigit(**s))
		i = i*10 + *((*s)++) - '0';
	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 code from
 * http://www.cs.uiowa.edu/~jones/bcd/decimal.html
 * (with permission from the author, Douglas W. Jones). */

/* Formats correctly any integer in [0,99999].
 * Outputs from one to five digits depending on input.
 * On i386 gcc 4.1.2 -O2: ~250 bytes of code. */
static char* put_dec_trunc(char *buf, unsigned q)
{
	unsigned d3, d2, d1, d0;
	d1 = (q>>4) & 0xf;
	d2 = (q>>8) & 0xf;
	d3 = (q>>12);

	d0 = 6*(d3 + d2 + d1) + (q & 0xf);
	q = (d0 * 0xcd) >> 11;
	d0 = d0 - 10*q;
	*buf++ = d0 + '0'; /* least significant digit */
	d1 = q + 9*d3 + 5*d2 + d1;
	if (d1 != 0) {
		q = (d1 * 0xcd) >> 11;
		d1 = d1 - 10*q;
		*buf++ = d1 + '0'; /* next digit */

		d2 = q + 2*d2;
		if ((d2 != 0) || (d3 != 0)) {
			q = (d2 * 0xd) >> 7;
			d2 = d2 - 10*q;
			*buf++ = d2 + '0'; /* next digit */

			d3 = q + 4*d3;
			if (d3 != 0) {
				q = (d3 * 0xcd) >> 11;
				d3 = d3 - 10*q;
				*buf++ = d3 + '0';  /* next digit */
				if (q != 0)
					*buf++ = q + '0';  /* most sign. digit */
			}
		}
	}
	return buf;
}
/* Same with if's removed. Always emits five digits */
static char* put_dec_full(char *buf, unsigned q)
{
	/* BTW, if q is in [0,9999], 8-bit ints will be enough, */
	/* but anyway, gcc produces better code with full-sized ints */
	unsigned d3, d2, d1, d0;
	d1 = (q>>4) & 0xf;
	d2 = (q>>8) & 0xf;
	d3 = (q>>12);

	/* Possible ways to approx. divide by 10 */
	/* gcc -O2 replaces multiply with shifts and adds */
	// (x * 0xcd) >> 11: 11001101 - shorter code than * 0x67 (on i386)
	// (x * 0x67) >> 10:  1100111
	// (x * 0x34) >> 9:    110100 - same
	// (x * 0x1a) >> 8:     11010 - same
	// (x * 0x0d) >> 7:      1101 - same, shortest code (on i386)

	d0 = 6*(d3 + d2 + d1) + (q & 0xf);
	q = (d0 * 0xcd) >> 11;
	d0 = d0 - 10*q;
	*buf++ = d0 + '0';
	d1 = q + 9*d3 + 5*d2 + d1;
		q = (d1 * 0xcd) >> 11;
		d1 = d1 - 10*q;
		*buf++ = d1 + '0';

		d2 = q + 2*d2;
			q = (d2 * 0xd) >> 7;
			d2 = d2 - 10*q;
			*buf++ = d2 + '0';

			d3 = q + 4*d3;
				q = (d3 * 0xcd) >> 11; /* - shorter code */
				/* q = (d3 * 0x67) >> 10; - would also work */
				d3 = d3 - 10*q;
				*buf++ = d3 + '0';
					*buf++ = q + '0';
	return buf;
}
/* No inlining helps gcc to use registers better */
static noinline char* put_dec(char *buf, unsigned long long num)
{
	while (1) {
		unsigned rem;
		if (num < 100000)
			return put_dec_trunc(buf, num);
		rem = do_div(num, 100000);
		buf = put_dec_full(buf, rem);
	}
}

#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 */
#define SMALL	32		/* Must be 32 == 0x20 */
#define SPECIAL	64		/* 0x */

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_UBYTE,
	FORMAT_TYPE_BYTE,
	FORMAT_TYPE_USHORT,
	FORMAT_TYPE_SHORT,
	FORMAT_TYPE_UINT,
	FORMAT_TYPE_INT,
	FORMAT_TYPE_NRCHARS,
	FORMAT_TYPE_SIZE_T,
	FORMAT_TYPE_PTRDIFF
};

struct printf_spec {
	enum format_type	type;
	int			flags;		/* flags to number() */
	int			field_width;	/* width of output field */
	int			base;
	int			precision;	/* # of digits/chars */
	int			qualifier;
};

static 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[66];
	char sign;
	char locase;
	int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10);
	int i;

	/* locase = 0 or 0x20. ORing digits or letters with 'locase'
	 * produces same digits or (maybe lowercased) letters */
	locase = (spec.flags & SMALL);
	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 == 0)
		tmp[i++] = '0';
	/* Generic code, for any base:
	else do {
		tmp[i++] = (digits[do_div(num,base)] | locase);
	} 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] | locase);
			num >>= shift;
		} while (num);
	} else { /* base 10 */
		i = put_dec(tmp, num) - tmp;
	}

	/* printing 100 using %2d gives "100", not "00" */
	if (i > spec.precision)
		spec.precision = i;
	/* leading space padding */
	spec.field_width -= spec.precision;
	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' | locase);
			++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 char *string(char *buf, char *end, char *s, struct printf_spec spec)
{
	int len, i;

	if ((unsigned long)s < PAGE_SIZE)
		s = "<NULL>";

	len = strnlen(s, spec.precision);

	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 char *symbol_string(char *buf, char *end, void *ptr,
				struct printf_spec spec, char ext)
{
	unsigned long value = (unsigned long) ptr;
#ifdef CONFIG_KALLSYMS
	char sym[KSYM_SYMBOL_LEN];
	if (ext != 'f')
		sprint_symbol(sym, value);
	else
		kallsyms_lookup(value, NULL, NULL, NULL, sym);
	return string(buf, end, sym, spec);
#else
	spec.field_width = 2*sizeof(void *);
	spec.flags |= SPECIAL | SMALL | ZEROPAD;
	spec.base = 16;
	return number(buf, end, value, spec);
#endif
}

static char *resource_string(char *buf, char *end, struct resource *res,
				struct printf_spec spec)
{
#ifndef IO_RSRC_PRINTK_SIZE
#define IO_RSRC_PRINTK_SIZE	4
#endif

#ifndef MEM_RSRC_PRINTK_SIZE
#define MEM_RSRC_PRINTK_SIZE	8
#endif
	struct printf_spec num_spec = {
		.base = 16,
		.precision = -1,
		.flags = SPECIAL | SMALL | ZEROPAD,
	};
	/* room for the actual numbers, the two "0x", -, [, ] and the final zero */
	char sym[4*sizeof(resource_size_t) + 8];
	char *p = sym, *pend = sym + sizeof(sym);
	int size = -1;

	if (res->flags & IORESOURCE_IO)
		size = IO_RSRC_PRINTK_SIZE;
	else if (res->flags & IORESOURCE_MEM)
		size = MEM_RSRC_PRINTK_SIZE;

	*p++ = '[';
	num_spec.field_width = size;
	p = number(p, pend, res->start, num_spec);
	*p++ = '-';
	p = number(p, pend, res->end, num_spec);
	*p++ = ']';
	*p = 0;

	return string(buf, end, sym, spec);
}

static char *mac_address_string(char *buf, char *end, u8 *addr,
				struct printf_spec spec, const char *fmt)
{
	char mac_addr[sizeof("xx:xx:xx:xx:xx:xx")];
	char *p = mac_addr;
	int i;

	for (i = 0; i < 6; i++) {
		p = pack_hex_byte(p, addr[i]);
		if (fmt[0] == 'M' && i != 5)
			*p++ = ':';
	}
	*p = '\0';

	return string(buf, end, mac_addr, spec);
}

static char *ip4_string(char *p, const u8 *addr, bool leading_zeros)
{
	int i;

	for (i = 0; i < 4; i++) {
		char temp[3];	/* hold each IP quad in reverse order */
		int digits = put_dec_trunc(temp, addr[i]) - temp;
		if (leading_zeros) {
			if (digits < 3)
				*p++ = '0';
			if (digits < 2)
				*p++ = '0';
		}
		/* reverse the digits in the quad */
		while (digits--)
			*p++ = temp[digits];
		if (i < 3)
			*p++ = '.';
	}

	*p = '\0';
	return p;
}

static char *ip6_compressed_string(char *p, const struct in6_addr *addr)
{
	int i;
	int j;
	int range;
	unsigned char zerolength[8];
	int longest = 1;
	int colonpos = -1;
	u16 word;
	u8 hi;
	u8 lo;
	bool needcolon = false;
	bool useIPv4 = ipv6_addr_v4mapped(addr) || ipv6_addr_is_isatap(addr);

	memset(zerolength, 0, sizeof(zerolength));

	if (useIPv4)
		range = 6;
	else
		range = 8;

	/* find position of longest 0 run */
	for (i = 0; i < range; i++) {
		for (j = i; j < range; j++) {
			if (addr->s6_addr16[j] != 0)
				break;
			zerolength[i]++;
		}
	}
	for (i = 0; i < range; i++) {
		if (zerolength[i] > longest) {
			longest = zerolength[i];
			colonpos = i;
		}
	}

	/* emit address */
	for (i = 0; i < range; i++) {
		if (i == colonpos) {
			if (needcolon || i == 0)
				*p++ = ':';
			*p++ = ':';
			needcolon = false;
			i += longest - 1;
			continue;
		}
		if (needcolon) {
			*p++ = ':';
			needcolon = false;
		}
		/* hex u16 without leading 0s */
		word = ntohs(addr->s6_addr16[i]);
		hi = word >> 8;
		lo = word & 0xff;
		if (hi) {
			if (hi > 0x0f)
				p = pack_hex_byte(p, hi);
			else
				*p++ = hex_asc_lo(hi);
		}
		if (hi || lo > 0x0f)
			p = pack_hex_byte(p, lo);
		else
			*p++ = hex_asc_lo(lo);
		needcolon = true;
	}

	if (useIPv4) {
		if (needcolon)
			*p++ = ':';
		p = ip4_string(p, &addr->s6_addr[12], false);
	}

	*p = '\0';
	return p;
}

static char *ip6_string(char *p, const struct in6_addr *addr, const char *fmt)
{
	int i;
	for (i = 0; i < 8; i++) {
		p = pack_hex_byte(p, addr->s6_addr[2 * i]);
		p = pack_hex_byte(p, addr->s6_addr[2 * i + 1]);
		if (fmt[0] == 'I' && i != 7)
			*p++ = ':';
	}

	*p = '\0';
	return p;
}

static char *ip6_addr_string(char *buf, char *end, const u8 *addr,
			     struct printf_spec spec, const char *fmt)
{
	char ip6_addr[sizeof("xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:255.255.255.255")];

	if (fmt[0] == 'I' && fmt[2] == 'c')
		ip6_compressed_string(ip6_addr, (const struct in6_addr *)addr);
	else
		ip6_string(ip6_addr, (const struct in6_addr *)addr, fmt);

	return string(buf, end, ip6_addr, spec);
}

static char *ip4_addr_string(char *buf, char *end, const u8 *addr,
			     struct printf_spec spec, const char *fmt)
{
	char ip4_addr[sizeof("255.255.255.255")];

	ip4_string(ip4_addr, addr, fmt[0] == 'i');

	return string(buf, end, ip4_addr, spec);
}

/*
 * Show a '%p' thing.  A kernel extension is that the '%p' is followed
 * by an extra set of alphanumeric characters that are extended format
 * specifiers.
 *
 * Right now we handle:
 *
 * - 'F' For symbolic function descriptor pointers with offset
 * - 'f' For simple symbolic function names without offset
 * - 'S' For symbolic direct pointers
 * - 'R' For a struct resource pointer, it prints the range of
 *       addresses (not the name nor the flags)
 * - 'M' For a 6-byte MAC address, it prints the address in the
 *       usual colon-separated hex notation
 * - 'm' For a 6-byte MAC address, it prints the hex address without colons
 * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
 *       IPv4 uses dot-separated decimal without leading 0's (1.2.3.4)
 *       IPv6 uses colon separated network-order 16 bit hex with leading 0's
 * - 'i' [46] for 'raw' IPv4/IPv6 addresses
 *       IPv6 omits the colons (01020304...0f)
 *       IPv4 uses dot-separated decimal with leading 0's (010.123.045.006)
 * - 'I6c' for IPv6 addresses printed as specified by
 *       http://www.ietf.org/id/draft-kawamura-ipv6-text-representation-03.txt
 * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
 * function pointers are really function descriptors, which contain a
 * pointer to the real address.
 */
static char *pointer(const char *fmt, char *buf, char *end, void *ptr,
			struct printf_spec spec)
{
	if (!ptr)
		return string(buf, end, "(null)", spec);

	switch (*fmt) {
	case 'F':
	case 'f':
		ptr = dereference_function_descriptor(ptr);
		/* Fallthrough */
	case 'S':
		return symbol_string(buf, end, ptr, spec, *fmt);
	case 'R':
		return resource_string(buf, end, ptr, spec);
	case 'M':			/* Colon separated: 00:01:02:03:04:05 */
	case 'm':			/* Contiguous: 000102030405 */
		return mac_address_string(buf, end, ptr, spec, fmt);
	case 'I':			/* Formatted IP supported
					 * 4:	1.2.3.4
					 * 6:	0001:0203:...:0708
					 * 6c:	1::708 or 1::1.2.3.4
					 */
	case 'i':			/* Contiguous:
					 * 4:	001.002.003.004
					 * 6:   000102...0f
					 */
		switch (fmt[1]) {
		case '6':
			return ip6_addr_string(buf, end, ptr, spec, fmt);
		case '4':
			return ip4_addr_string(buf, end, ptr, spec, fmt);
		}
		break;
	}
	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 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 (; *fmt ; ++fmt) {
		if (*fmt == '%')
			break;
	}

	/* Return the current non-format string */
	if (fmt != start || !*fmt)
		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 == 'h' || *fmt == 'l' || *fmt == 'L' ||
	    *fmt == 'Z' || *fmt == 'z' || *fmt == 't') {
		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;
			}
		}
	}

	/* 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;
		/* skip alnum */

	case 'n':
		spec->type = FORMAT_TYPE_NRCHARS;
		return ++fmt - start;

	case '%':