FreeBSD/Linux Kernel Cross Reference
sys/lib/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>       /* for KSYM_SYMBOL_LEN */
    #include <linux/types.h>
    #include <linux/string.h>
    #include <linux/ctype.h>
    #include <linux/kernel.h>
    #include <linux/kallsyms.h>
    #include <linux/math64.h>
    #include <linux/uaccess.h>
    #include <linux/ioport.h>
    #include <net/addrconf.h>
    
    #include <asm/page.h>           /* for PAGE_SIZE */
    #include <asm/sections.h>       /* for dereference_function_descriptor() */
    
    #include "kstrtox.h"
    
    /**
     * 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
     *
     * This function is obsolete. Please use kstrtoull instead.
     */
    unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
    {
            unsigned long long result;
            unsigned int rv;
    
            cp = _parse_integer_fixup_radix(cp, &base);
            rv = _parse_integer(cp, base, &result);
            /* FIXME */
            cp += (rv & ~KSTRTOX_OVERFLOW);
    
            if (endp)
                    *endp = (char *)cp;
    
            return result;
    }
    EXPORT_SYMBOL(simple_strtoull);
    
    /**
     * 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
     *
     * This function is obsolete. Please use kstrtoul instead.
     */
    unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base)
    {
            return simple_strtoull(cp, endp, base);
    }
    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
     *
     * This function is obsolete. Please use kstrtol instead.
     */
    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_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
     *
     * This function is obsolete. Please use kstrtoll instead.
     */
   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);
   }
   EXPORT_SYMBOL(simple_strtoll);
   
   static noinline_for_stack
   int skip_atoi(const char **s)
   {
           int i = 0;
   
           while (isdigit(**s))
                   i = i*10 + *((*s)++) - '';
   
           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 BITS_PER_LONG != 32 || BITS_PER_LONG_LONG != 64
   /* 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) + ''; /* 1 */
           q      = (r * (uint64_t)0x1999999a) >> 32;
           *buf++ = (r - 10 * q) + ''; /* 2 */
           r      = (q * (uint64_t)0x1999999a) >> 32;
           *buf++ = (q - 10 * r) + ''; /* 3 */
           q      = (r * (uint64_t)0x1999999a) >> 32;
           *buf++ = (r - 10 * q) + ''; /* 4 */
           r      = (q * (uint64_t)0x1999999a) >> 32;
           *buf++ = (q - 10 * r) + ''; /* 5 */
           /* Now value is under 10000, can avoid 64-bit multiply */
           q      = (r * 0x199a) >> 16;
           *buf++ = (r - 10 * q)  + ''; /* 6 */
           r      = (q * 0xcd) >> 11;
           *buf++ = (q - 10 * r)  + ''; /* 7 */
           q      = (r * 0xcd) >> 11;
           *buf++ = (r - 10 * q) + ''; /* 8 */
           *buf++ = q + ''; /* 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 */
           while (r >= 10000) {
                   q = r + '';
                   r  = (r * (uint64_t)0x1999999a) >> 32;
                   *buf++ = q - 10*r;
           }
   
           q      = (r * 0x199a) >> 16;    /* r <= 9999 */
           *buf++ = (r - 10 * q)  + '';
           if (q == 0)
                   return buf;
           r      = (q * 0xcd) >> 11;      /* q <= 999 */
           *buf++ = (q - 10 * r)  + '';
           if (r == 0)
                   return buf;
           q      = (r * 0xcd) >> 11;      /* r <= 99 */
           *buf++ = (r - 10 * q) + '';
           if (q == 0)
                   return buf;
           *buf++ = q + '';                /* q <= 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 BITS_PER_LONG != 32 || BITS_PER_LONG_LONG != 64
   
   /* 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 */
   
   /* See comment in put_dec_full9 for choice of constants */
   static noinline_for_stack
   void put_dec_full4(char *buf, unsigned q)
   {
           unsigned r;
           r      = (q * 0xccd) >> 15;
           buf[0] = (q - 10 * r) + '';
           q      = (r * 0xcd) >> 11;
           buf[1] = (r - 10 * q)  + '';
           r      = (q * 0xcd) >> 11;
           buf[2] = (q - 10 * r)  + '';
           buf[3] = r + '';
   }
   
   /*
    * Call put_dec_full4 on x % 10000, return x / 10000.
    * The approximation x/10000 == (x * 0x346DC5D7) >> 43
    * holds for all x < 1,128,869,999.  The largest value this
    * helper will ever be asked to convert is 1,125,520,955.
    * (d1 in the put_dec code, assuming n is all-ones).
    */
   static
   unsigned put_dec_helper4(char *buf, unsigned x)
   {
           uint32_t q = (x * (uint64_t)0x346DC5D7) >> 43;
   
           put_dec_full4(buf, x - q * 10000);
           return q;
   }
   
   /* 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);
           q = put_dec_helper4(buf, q);
   
           q += 7671 * d3 + 9496 * d2 + 6 * d1;
           q = put_dec_helper4(buf+4, q);
   
           q += 4749 * d3 + 42 * d2;
           q = put_dec_helper4(buf+8, q);
   
           q += 281 * d3;
           buf += 12;
           if (q)
                   buf = put_dec_trunc8(buf, q);
           else while (buf[-1] == '')
                   --buf;
   
           return buf;
   }
   
   #endif
   
   /*
    * Convert passed number to decimal string.
    * Returns the length of string.  On buffer overflow, returns 0.
    *
    * If speed is not important, use snprintf(). It's easy to read the code.
    */
   int num_to_str(char *buf, int size, unsigned long long num)
   {
           char tmp[sizeof(num) * 3];
           int idx, len;
   
           /* put_dec() may work incorrectly for num = 0 (generate "", not "") */
           if (num <= 9) {
                   tmp[0] = '' + num;
                   len = 1;
           } else {
                   len = put_dec(tmp, num) - tmp;
           }
   
           if (len > size)
                   return 0;
           for (idx = 0; idx < len; ++idx)
                   buf[idx] = tmp[len - idx - 1];
           return len;
   }
   
   #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              /* use lowercase in hex (must be 32 == 0x20) */
   #define SPECIAL 64              /* prefix hex with "0x", octal with "" */
   
   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 {
           u8      type;           /* format_type enum */
           u8      flags;          /* flags to number() */
           u8      base;           /* number base, 8, 10 or 16 only */
           u8      qualifier;      /* number qualifier, one of 'hHlLtzZ' */
           s16     field_width;    /* width of output field */
           s16     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[66];
           char sign;
           char locase;
           int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10);
           int i;
           bool is_zero = num == 0LL;
   
           /* 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) {
                   if (spec.base == 16)
                           spec.field_width -= 2;
                   else if (!is_zero)
                           spec.field_width--;
           }
   
           /* generate full string in tmp[], in reverse order */
           i = 0;
           if (num < spec.base)
                   tmp[i++] = digits[num] | locase;
           /* 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" / "" prefix */
           if (need_pfx) {
                   if (spec.base == 16 || !is_zero) {
                           if (buf < end)
                                   *buf = '';
                           ++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) ? '' : ' ';
                   while (--spec.field_width >= 0) {
                           if (buf < end)
                                   *buf = c;
                           ++buf;
                   }
           }
           /* hmm even more zero padding? */
           while (i <= --spec.precision) {
                   if (buf < end)
                           *buf = '';
                   ++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 ((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 noinline_for_stack
   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 == 'B')
                   sprint_backtrace(sym, value);
           else if (ext != 'f' && ext != 's')
                   sprint_symbol(sym, value);
           else
                   sprint_symbol_no_offset(sym, value);
   
           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 noinline_for_stack
   char *resource_string(char *buf, char *end, struct resource *res,
                         struct printf_spec spec, const char *fmt)
   {
   #ifndef IO_RSRC_PRINTK_SIZE
   #define IO_RSRC_PRINTK_SIZE     6
   #endif
   
   #ifndef MEM_RSRC_PRINTK_SIZE
   #define MEM_RSRC_PRINTK_SIZE    10
   #endif
           static const struct printf_spec io_spec = {
                   .base = 16,
                   .field_width = IO_RSRC_PRINTK_SIZE,
                   .precision = -1,
                   .flags = SPECIAL | SMALL | ZEROPAD,
           };
           static const struct printf_spec mem_spec = {
                   .base = 16,
                   .field_width = MEM_RSRC_PRINTK_SIZE,
                   .precision = -1,
                   .flags = SPECIAL | SMALL | ZEROPAD,
           };
           static const struct printf_spec bus_spec = {
                   .base = 16,
                   .field_width = 2,
                   .precision = -1,
                   .flags = SMALL | ZEROPAD,
           };
           static const struct printf_spec dec_spec = {
                   .base = 10,
                   .precision = -1,
                   .flags = 0,
           };
           static const struct printf_spec str_spec = {
                   .field_width = -1,
                   .precision = 10,
                   .flags = LEFT,
           };
           static const struct printf_spec flag_spec = {
                   .base = 16,
                   .precision = -1,
                   .flags = SPECIAL | SMALL,
           };
   
           /* 32-bit res (sizeof==4): 10 chars in dec, 10 in hex ("0x" + 8)
            * 64-bit res (sizeof==8): 20 chars in dec, 18 in hex ("0x" + 16) */
   #define RSRC_BUF_SIZE           ((2 * sizeof(resource_size_t)) + 4)
   #define FLAG_BUF_SIZE           (2 * sizeof(res->flags))
   #define DECODED_BUF_SIZE        sizeof("[mem - 64bit pref window disabled]")
   #define RAW_BUF_SIZE            sizeof("[mem - flags 0x]")
           char sym[max(2*RSRC_BUF_SIZE + DECODED_BUF_SIZE,
                        2*RSRC_BUF_SIZE + FLAG_BUF_SIZE + RAW_BUF_SIZE)];
   
           char *p = sym, *pend = sym + sizeof(sym);
           int decode = (fmt[0] == 'R') ? 1 : 0;
           const struct printf_spec *specp;
   
           *p++ = '[';
           if (res->flags & IORESOURCE_IO) {
                   p = string(p, pend, "io  ", str_spec);
                   specp = &io_spec;
           } else if (res->flags & IORESOURCE_MEM) {
                   p = string(p, pend, "mem ", str_spec);
                   specp = &mem_spec;
           } else if (res->flags & IORESOURCE_IRQ) {
                   p = string(p, pend, "irq ", str_spec);
                   specp = &dec_spec;
           } else if (res->flags & IORESOURCE_DMA) {
                   p = string(p, pend, "dma ", str_spec);
                   specp = &dec_spec;
           } else if (res->flags & IORESOURCE_BUS) {
                   p = string(p, pend, "bus ", str_spec);
                   specp = &bus_spec;
           } else {
                   p = string(p, pend, "??? ", str_spec);
                   specp = &mem_spec;
                   decode = 0;
           }
           p = number(p, pend, res->start, *specp);
           if (res->start != res->end) {
                   *p++ = '-';
                   p = number(p, pend, res->end, *specp);
           }
           if (decode) {
                   if (res->flags & IORESOURCE_MEM_64)
                           p = string(p, pend, " 64bit", str_spec);
                   if (res->flags & IORESOURCE_PREFETCH)
                           p = string(p, pend, " pref", str_spec);
                   if (res->flags & IORESOURCE_WINDOW)
                           p = string(p, pend, " window", str_spec);
                   if (res->flags & IORESOURCE_DISABLED)
                           p = string(p, pend, " disabled", str_spec);
           } else {
                   p = string(p, pend, " flags ", str_spec);
                   p = number(p, pend, res->flags, flag_spec);
           }
           *p++ = ']';
           *p = '\0';
   
           return string(buf, end, sym, spec);
   }
   
   static noinline_for_stack
   char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
                    const char *fmt)
   {
           int i, len = 1;         /* if we pass '%ph[CDN]', field witdh remains
                                      negative value, fallback to the default */
           char separator;
   
           if (spec.field_width == 0)
                   /* nothing to print */
                   return buf;
   
           if (ZERO_OR_NULL_PTR(addr))
                   /* NULL pointer */
                   return string(buf, end, NULL, spec);
   
           switch (fmt[1]) {
           case 'C':
                   separator = ':';
                   break;
           case 'D':
                   separator = '-';
                   break;
           case 'N':
                   separator = 0;
                   break;
           default:
                   separator = ' ';
                   break;
           }
   
           if (spec.field_width > 0)
                   len = min_t(int, spec.field_width, 64);
   
           for (i = 0; i < len && buf < end - 1; i++) {
                   buf = hex_byte_pack(buf, addr[i]);
   
                   if (buf < end && separator && i != len - 1)
                           *buf++ = separator;
           }
   
           return buf;
   }
   
   static noinline_for_stack
   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;
           char separator;
           bool reversed = false;
   
           switch (fmt[1]) {
           case 'F':
                   separator = '-';
                   break;
   
           case 'R':
                   reversed = true;
                   /* fall through */
   
           default:
                   separator = ':';
                   break;
           }
   
           for (i = 0; i < 6; i++) {
                   if (reversed)
                           p = hex_byte_pack(p, addr[5 - i]);
                   else
                           p = hex_byte_pack(p, addr[i]);
   
                   if (fmt[0] == 'M' && i != 5)
                           *p++ = separator;
           }
           *p = '\0';
   
           return string(buf, end, mac_addr, spec);
   }
   
   static noinline_for_stack
   char *ip4_string(char *p, const u8 *addr, const char *fmt)
   {
           int i;
           bool leading_zeros = (fmt[0] == 'i');
           int index;
           int step;
   
           switch (fmt[2]) {
           case 'h':
   #ifdef __BIG_ENDIAN
                   index = 0;
                   step = 1;
   #else
                   index = 3;
                   step = -1;
   #endif
                   break;
           case 'l':
                   index = 3;
                   step = -1;
                   break;
           case 'n':
           case 'b':
           default:
                   index = 0;
                   step = 1;
                   break;
           }
           for (i = 0; i < 4; i++) {
                   char temp[3];   /* hold each IP quad in reverse order */
                   int digits = put_dec_trunc8(temp, addr[index]) - temp;
                   if (leading_zeros) {
                           if (digits < 3)
                                   *p++ = '';
                           if (digits < 2)
                                   *p++ = '';
                   }
                   /* reverse the digits in the quad */
                   while (digits--)
                           *p++ = temp[digits];
                   if (i < 3)
                           *p++ = '.';
                   index += step;
           }
           *p = '\0';
   
           return p;
   }
   
   static noinline_for_stack
   char *ip6_compressed_string(char *p, const char *addr)
   {
           int i, j, range;
           unsigned char zerolength[8];
           int longest = 1;
           int colonpos = -1;
           u16 word;
           u8 hi, lo;
           bool needcolon = false;
           bool useIPv4;
           struct in6_addr in6;
   
           memcpy(&in6, addr, sizeof(struct in6_addr));
   
           useIPv4 = ipv6_addr_v4mapped(&in6) || ipv6_addr_is_isatap(&in6);
   
           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 (in6.s6_addr16[j] != 0)
                                   break;
                           zerolength[i]++;
                   }
           }
           for (i = 0; i < range; i++) {
                   if (zerolength[i] > longest) {
                           longest = zerolength[i];
                           colonpos = i;
                   }
           }
           if (longest == 1)               /* don't compress a single 0 */
                   colonpos = -1;
   
           /* 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(in6.s6_addr16[i]);
                   hi = word >> 8;
                   lo = word & 0xff;
                   if (hi) {
                           if (hi > 0x0f)
                                   p = hex_byte_pack(p, hi);
                           else
                                   *p++ = hex_asc_lo(hi);
                           p = hex_byte_pack(p, lo);
                   }
                   else if (lo > 0x0f)
                           p = hex_byte_pack(p, lo);
                   else
                           *p++ = hex_asc_lo(lo);
                   needcolon = true;
           }
   
           if (useIPv4) {
                   if (needcolon)
                           *p++ = ':';
                   p = ip4_string(p, &in6.s6_addr[12], "I4");
           }
           *p = '\0';
   
           return p;
   }
   
   static noinline_for_stack
   char *ip6_string(char *p, const char *addr, const char *fmt)
   {
           int i;
   
           for (i = 0; i < 8; i++) {
                   p = hex_byte_pack(p, *addr++);
                   p = hex_byte_pack(p, *addr++);
                   if (fmt[0] == 'I' && i != 7)
                           *p++ = ':';
           }
           *p = '\0';
   
           return p;
   }
   
   static noinline_for_stack
   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, addr);
           else
                   ip6_string(ip6_addr, addr, fmt);
   
           return string(buf, end, ip6_addr, spec);
   }
   
   static noinline_for_stack
   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);
   
           return string(buf, end, ip4_addr, spec);
   }
   
   static noinline_for_stack
   char *uuid_string(char *buf, char *end, const u8 *addr,
                     struct printf_spec spec, const char *fmt)
   {
           char uuid[sizeof("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx")];
           char *p = uuid;
           int i;
           static const u8 be[16] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
           static const u8 le[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
           const u8 *index = be;
           bool uc = false;
   
           switch (*(++fmt)) {
           case 'L':
                   uc = true;              /* fall-through */
           case 'l':
                   index = le;
                   break;
           case 'B':
                   uc = true;
                   break;
           }
   
           for (i = 0; i < 16; i++) {
                   p = hex_byte_pack(p, addr[index[i]]);
                   switch (i) {
                   case 3:
                   case 5:
                   case 7:
                   case 9:
                           *p++ = '-';
                           break;
                   }
           }
   
           *p = 0;
   
           if (uc) {
                   p = uuid;
                   do {
                           *p = toupper(*p);
                   } while (*(++p));
           }
   
           return string(buf, end, uuid, spec);
   }
   
   static
   char *netdev_feature_string(char *buf, char *end, const u8 *addr,
                         struct printf_spec spec)
   {
           spec.flags |= SPECIAL | SMALL | ZEROPAD;
           if (spec.field_width == -1)
                   spec.field_width = 2 + 2 * sizeof(netdev_features_t);
           spec.base = 16;
   
           return number(buf, end, *(const netdev_features_t *)addr, spec);
   }
   
   int kptr_restrict __read_mostly;
   
   /*
    * 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 with offset
    * - 's' For symbolic direct pointers without offset
    * - 'B' For backtraced symbolic direct pointers with offset
    * - 'R' For decoded struct resource, e.g., [mem 0x0-0x1f 64bit pref]
    * - 'r' For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201]
    * - '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
    * - 'MF' For a 6-byte MAC FDDI address, it prints the address
    *       with a dash-separated hex notation
    * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
    * - '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)
   * - '[Ii]4[hnbl]' IPv4 addresses in host, network, big or little endian order
   * - 'I6c' for IPv6 addresses printed as specified by
   *       http://tools.ietf.org/html/rfc5952
   * - 'U' For a 16 byte UUID/GUID, it prints the UUID/GUID in the form
   *       "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
   *       Options for %pU are:
   *         b big endian lower case hex (default)
   *         B big endian UPPER case hex
   *         l little endian lower case hex
   *         L little endian UPPER case hex
   *           big endian output byte order is:
   *             [0][1][2][3]-[4][5]-[6][7]-[8][9]-[10][11][12][13][14][15]
   *           little endian output byte order is:
   *             [3][2][1][0]-[5][4]-[7][6]-[8][9]-[10][11][12][13][14][15]
   * - 'V' For a struct va_format which contains a format string * and va_list *,
   *       call vsnprintf(->format, *->va_list).
   *       Implements a "recursive vsnprintf".
   *       Do not use this feature without some mechanism to verify the
   *       correctness of the format string and va_list arguments.
   * - 'K' For a kernel pointer that should be hidden from unprivileged users
   * - 'NF' For a netdev_features_t
   * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
   *            a certain separator (' ' by default):
   *              C colon
   *              D dash
   *              N no separator
   *            The maximum supported length is 64 bytes of the input. Consider
   *            to use print_hex_dump() for the larger input.
   *
   * 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 noinline_for_stack
  char *pointer(const char *fmt, char *buf, char *end, void *ptr,
                struct printf_spec spec)
  {
          int default_width = 2 * sizeof(void *) + (spec.flags & SPECIAL ? 2 : 0);
  
          if (!ptr && *fmt != 'K') {
                  /*
                   * Print (null) with the same width as a pointer so it makes
                   * tabular output look nice.
                   */
                  if (spec.field_width == -1)
                          spec.field_width = default_width;
                  return string(buf, end, "(null)", spec);
          }
  
          switch (*fmt) {
          case 'F':
          case 'f':
                  ptr = dereference_function_descriptor(ptr);
                  /* Fallthrough */
          case 'S':
          case 's':
          case 'B':
                  return symbol_string(buf, end, ptr, spec, *fmt);
          case 'R':
          case 'r':
                  return resource_string(buf, end, ptr, spec, fmt);
          case 'h':
                  return hex_string(buf, end, ptr, spec, fmt);
          case 'M':                       /* Colon separated: 00:01:02:03:04:05 */
          case 'm':                       /* Contiguous: 000102030405 */
                                          /* [mM]F (FDDI) */
                                          /* [mM]R (Reverse order; Bluetooth) */
                  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;
          case 'U':
                  return uuid_string(buf, end, ptr, spec, fmt);
          case 'V':
                  {
                          va_list va;
  
                          va_copy(va, *((struct va_format *)ptr)->va);
                          buf += vsnprintf(buf, end > buf ? end - buf : 0,
                                           ((struct va_format *)ptr)->fmt, va);
                          va_end(va);
                          return buf;
                  }
          case 'K':
                  /*
                   * %pK cannot be used in IRQ context because its test
                   * for CAP_SYSLOG would be meaningless.
                   */
                  if (kptr_restrict && (in_irq() || in_serving_softirq() ||
                                        in_nmi())) {
                          if (spec.field_width == -1)
                                  spec.field_width = default_width;
                          return string(buf, end, "pK-error", spec);
                  }
                  if (!((kptr_restrict == 0) ||
                        (kptr_restrict == 1 &&
                         has_capability_noaudit(current, CAP_SYSLOG))))
                          ptr = NULL;
                  break;
          case 'N':
                  switch (fmt[1]) {
                  case 'F':
                          return netdev_feature_string(buf, end, ptr, spec);
                  }
                  break;
          }
          spec.flags |= SMALL;
          if (spec.field_width == -1) {
                  spec.field_width = default_width;
                  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 (; *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 '': 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' || _tolower(*fmt) == 'l' ||
              _tolower(*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 '%':
                  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 (_tolower(spec->qualifier) == 'z') {
                  spec->type = FORMAT_TYPE_SIZE_T;
          } else if (spec->qualifier == 't') {
                  spec->type = FORMAT_TYPE_PTRDIFF;
          } else if (spec->qualifier == 'H') {
                  if (spec->flags & SIGN)
                          spec->type = FORMAT_TYPE_BYTE;
                  else
                          spec->type = FORMAT_TYPE_UBYTE;
          } else if (spec->qualifier == 'h') {
                  if (spec->flags & SIGN)
                          spec->type = FORMAT_TYPE_SHORT;
                  else
                          spec->type = FORMAT_TYPE_USHORT;
          } 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
   *
   * This function follows C99 vsnprintf, but has some extensions:
   * %pS output the name of a text symbol with offset
   * %ps output the name of a text symbol without offset
   * %pF output the name of a function pointer with its offset
   * %pf output the name of a function pointer without its offset
   * %pB output the name of a backtrace symbol with its offset
   * %pR output the address range in a struct resource with decoded flags
   * %pr output the address range in a struct resource with raw flags
   * %pM output a 6-byte MAC address with colons
   * %pMR output a 6-byte MAC address with colons in reversed order
   * %pMF output a 6-byte MAC address with dashes
   * %pm output a 6-byte MAC address without colons
   * %pmR output a 6-byte MAC address without colons in reversed order
   * %pI4 print an IPv4 address without leading zeros
   * %pi4 print an IPv4 address with leading zeros
   * %pI6 print an IPv6 address with colons
   * %pi6 print an IPv6 address without colons
   * %pI6c print an IPv6 address as specified by RFC 5952
   * %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
   *   case.
   * %*ph[CDN] a variable-length hex string with a separator (supports up to 64
   *           bytes of the input)
   * %n is ignored
   *
   * ** Please update Documentation/printk-formats.txt when making changes **
   *
   * 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().
   */
  int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
  {
          unsigned long long num;
          char *str, *end;
          struct printf_spec spec = {0};
  
          /* Reject out-of-range values early.  Large positive sizes are
             used for unknown buffer sizes. */
          if (WARN_ON_ONCE((int) size < 0))
                  return 0;
  
          str = buf;
          end = buf + size;
  
          /* Make sure end is always >= buf */
          if (end < buf) {
                  end = ((void *)-1);
                  size = end - buf;
          }
  
          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;
  
                  case FORMAT_TYPE_NRCHARS: {
                          u8 qualifier = spec.qualifier;
  
                          if (qualifier == 'l') {
                                  long *ip = va_arg(args, long *);
                                  *ip = (str - buf);
                          } else if (_tolower(qualifier) == 'z') {
                                  size_t *ip = va_arg(args, size_t *);
                                  *ip = (str - buf);
                          } else {
                                  int *ip = va_arg(args, int *);
                                  *ip = (str - buf);
                          }
                          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_SIZE_T:
                                  if (spec.flags & SIGN)
                                          num = va_arg(args, ssize_t);
                                  else
                                          num = va_arg(args, size_t);
                                  break;
                          case FORMAT_TYPE_PTRDIFF:
                                  num = va_arg(args, ptrdiff_t);
                                  break;
                          case FORMAT_TYPE_UBYTE:
                                  num = (unsigned char) va_arg(args, int);
                                  break;
                          case FORMAT_TYPE_BYTE:
                                  num = (signed char) va_arg(args, int);
                                  break;
                          case FORMAT_TYPE_USHORT:
                                  num = (unsigned short) va_arg(args, int);
                                  break;
                          case FORMAT_TYPE_SHORT:
                                  num = (short) va_arg(args, int);
                                  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;
  
  }
  EXPORT_SYMBOL(vsnprintf);
  
  /**
   * vscnprintf - 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 have been written into
   * the @buf not including the trailing '\0'. If @size is == 0 the function
   * returns 0.
   *
   * If you're not already dealing with a va_list consider using scnprintf().
   *
   * See the vsnprintf() documentation for format string extensions over C99.
   */
  int vscnprintf(char *buf, size_t size, const char *fmt, va_list args)
  {
          int i;
  
          i = vsnprintf(buf, size, fmt, args);
  
          if (likely(i < size))
                  return i;
          if (size != 0)
                  return size - 1;
          return 0;
  }
  EXPORT_SYMBOL(vscnprintf);
  
  /**
   * snprintf - 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
   * @...: Arguments for the format string
   *
   * The return value is the number of characters which would be
   * generated for the given input, excluding the trailing null,
   * as per ISO C99.  If the return is greater than or equal to
   * @size, the resulting string is truncated.
   *
   * See the vsnprintf() documentation for format string extensions over C99.
   */
  int snprintf(char *buf, size_t size, const char *fmt, ...)
  {
          va_list args;
          int i;
  
          va_start(args, fmt);
          i = vsnprintf(buf, size, fmt, args);
          va_end(args);
  
          return i;
  }
  EXPORT_SYMBOL(snprintf);
  
  /**
   * scnprintf - 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
   * @...: Arguments for the format string
   *
   * The return value is the number of characters written into @buf not including
   * the trailing '\0'. If @size is == 0 the function returns 0.
   */
  
  int scnprintf(char *buf, size_t size, const char *fmt, ...)
  {
          va_list args;
          int i;
  
          va_start(args, fmt);
          i = vscnprintf(buf, size, fmt, args);
          va_end(args);
  
          return i;
  }
  EXPORT_SYMBOL(scnprintf);
  
  /**
   * vsprintf - Format a string and place it in a buffer
   * @buf: The buffer to place the result into
   * @fmt: The format string to use
   * @args: Arguments for the format string
   *
   * The function returns the number of characters written
   * into @buf. Use vsnprintf() or vscnprintf() in order to avoid
   * buffer overflows.
   *
   * If you're not already dealing with a va_list consider using sprintf().
   *
   * See the vsnprintf() documentation for format string extensions over C99.
   */
  int vsprintf(char *buf, const char *fmt, va_list args)
  {
          return vsnprintf(buf, INT_MAX, fmt, args);
  }
  EXPORT_SYMBOL(vsprintf);
  
  /**
   * sprintf - Format a string and place it in a buffer
   * @buf: The buffer to place the result into
   * @fmt: The format string to use
   * @...: Arguments for the format string
   *
   * The function returns the number of characters written
   * into @buf. Use snprintf() or scnprintf() in order to avoid
   * buffer overflows.
   *
   * See the vsnprintf() documentation for format string extensions over C99.
   */
  int sprintf(char *buf, const char *fmt, ...)
  {
          va_list args;
          int i;
  
          va_start(args, fmt);
          i = vsnprintf(buf, INT_MAX, fmt, args);
          va_end(args);
  
          return i;
  }
  EXPORT_SYMBOL(sprintf);
  
  #ifdef CONFIG_BINARY_PRINTF
  /*
   * bprintf service:
   * vbin_printf() - VA arguments to binary data
   * bstr_printf() - Binary data to text string
   */
  
  /**
   * vbin_printf - Parse a format string and place args' binary value in a buffer
   * @bin_buf: The buffer to place args' binary value
   * @size: The size of the buffer(by words(32bits), not characters)
   * @fmt: The format string to use
   * @args: Arguments for the format string
   *
   * The format follows C99 vsnprintf, except %n is ignored, and its argument
   * is skiped.
   *
   * The return value is the number of words(32bits) which would be generated for
   * the given input.
   *
   * NOTE:
   * If the return value is greater than @size, the resulting bin_buf is NOT
   * valid for bstr_printf().
   */
  int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args)
  {
          struct printf_spec spec = {0};
          char *str, *end;
  
          str = (char *)bin_buf;
          end = (char *)(bin_buf + size);
  
  #define save_arg(type)                                                  \
  do {                                                                    \
          if (sizeof(type) == 8) {                                        \
                  unsigned long long value;                               \
                  str = PTR_ALIGN(str, sizeof(u32));                      \
                  value = va_arg(args, unsigned long long);               \
                  if (str + sizeof(type) <= end) {                        \
                          *(u32 *)str = *(u32 *)&value;                   \
                          *(u32 *)(str + 4) = *((u32 *)&value + 1);       \
                  }                                                       \
          } else {                                                        \
                  unsigned long value;                                    \
                  str = PTR_ALIGN(str, sizeof(type));                     \
                  value = va_arg(args, int);                              \
                  if (str + sizeof(type) <= end)                          \
                          *(typeof(type) *)str = (type)value;             \
          }                                                               \
          str += sizeof(type);                                            \
  } while (0)
  
          while (*fmt) {
                  int read = format_decode(fmt, &spec);
  
                  fmt += read;
  
                  switch (spec.type) {
                  case FORMAT_TYPE_NONE:
                  case FORMAT_TYPE_INVALID:
                  case FORMAT_TYPE_PERCENT_CHAR:
                          break;
  
                  case FORMAT_TYPE_WIDTH:
                  case FORMAT_TYPE_PRECISION:
                          save_arg(int);
                          break;
  
                  case FORMAT_TYPE_CHAR:
                          save_arg(char);
                          break;
  
                  case FORMAT_TYPE_STR: {
                          const char *save_str = va_arg(args, char *);
                          size_t len;
  
                          if ((unsigned long)save_str > (unsigned long)-PAGE_SIZE
                                          || (unsigned long)save_str < PAGE_SIZE)
                                  save_str = "(null)";
                          len = strlen(save_str) + 1;
                          if (str + len < end)
                                  memcpy(str, save_str, len);
                          str += len;
                          break;
                  }
  
                  case FORMAT_TYPE_PTR:
                          save_arg(void *);
                          /* skip all alphanumeric pointer suffixes */
                          while (isalnum(*fmt))
                                  fmt++;
                          break;
  
                  case FORMAT_TYPE_NRCHARS: {
                          /* skip %n 's argument */
                          u8 qualifier = spec.qualifier;
                          void *skip_arg;
                          if (qualifier == 'l')
                                  skip_arg = va_arg(args, long *);
                          else if (_tolower(qualifier) == 'z')
                                  skip_arg = va_arg(args, size_t *);
                          else
                                  skip_arg = va_arg(args, int *);
                          break;
                  }
  
                  default:
                          switch (spec.type) {
  
                          case FORMAT_TYPE_LONG_LONG:
                                  save_arg(long long);
                                  break;
                          case FORMAT_TYPE_ULONG:
                          case FORMAT_TYPE_LONG:
                                  save_arg(unsigned long);
                                  break;
                          case FORMAT_TYPE_SIZE_T:
                                  save_arg(size_t);
                                  break;
                          case FORMAT_TYPE_PTRDIFF:
                                  save_arg(ptrdiff_t);
                                  break;
                          case FORMAT_TYPE_UBYTE:
                          case FORMAT_TYPE_BYTE:
                                  save_arg(char);
                                  break;
                          case FORMAT_TYPE_USHORT:
                          case FORMAT_TYPE_SHORT:
                                  save_arg(short);
                                  break;
                          default:
                                  save_arg(int);
                          }
                  }
          }
  
          return (u32 *)(PTR_ALIGN(str, sizeof(u32))) - bin_buf;
  #undef save_arg
  }
  EXPORT_SYMBOL_GPL(vbin_printf);
  
  /**
   * bstr_printf - Format a string from binary arguments 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
   * @bin_buf: Binary arguments for the format string
   *
   * This function like C99 vsnprintf, but the difference is that vsnprintf gets
   * arguments from stack, and bstr_printf gets arguments from @bin_buf which is
   * a binary buffer that generated by vbin_printf.
   *
   * The format follows C99 vsnprintf, but has some extensions:
   *  see vsnprintf comment for details.
   *
   * 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.
   */
  int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf)
  {
          struct printf_spec spec = {0};
          char *str, *end;
          const char *args = (const char *)bin_buf;
  
          if (WARN_ON_ONCE((int) size < 0))
                  return 0;
  
          str = buf;
          end = buf + size;
  
  #define get_arg(type)                                                   \
  ({                                                                      \
          typeof(type) value;                                             \
          if (sizeof(type) == 8) {                                        \
                  args = PTR_ALIGN(args, sizeof(u32));                    \
                  *(u32 *)&value = *(u32 *)args;                          \
                  *((u32 *)&value + 1) = *(u32 *)(args + 4);              \
          } else {                                                        \
                  args = PTR_ALIGN(args, sizeof(type));                   \
                  value = *(typeof(type) *)args;                          \
          }                                                               \
          args += sizeof(type);                                           \
          value;                                                          \
  })
  
          /* Make sure end is always >= buf */
          if (end < buf) {
                  end = ((void *)-1);
                  size = end - buf;
          }
  
          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 = get_arg(int);
                          break;
  
                  case FORMAT_TYPE_PRECISION:
                          spec.precision = get_arg(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) get_arg(char);
                          if (str < end)
                                  *str = c;
                          ++str;
                          while (--spec.field_width > 0) {
                                  if (str < end)
                                          *str = ' ';
                                  ++str;
                          }
                          break;
                  }
  
                  case FORMAT_TYPE_STR: {
                          const char *str_arg = args;
                          args += strlen(str_arg) + 1;
                          str = string(str, end, (char *)str_arg, spec);
                          break;
                  }
  
                  case FORMAT_TYPE_PTR:
                          str = pointer(fmt+1, str, end, get_arg(void *), spec);
                          while (isalnum(*fmt))
                                  fmt++;
                          break;
  
                  case FORMAT_TYPE_PERCENT_CHAR:
                  case FORMAT_TYPE_INVALID:
                          if (str < end)
                                  *str = '%';
                          ++str;
                          break;
  
                  case FORMAT_TYPE_NRCHARS:
                          /* skip */
                          break;
  
                  default: {
                          unsigned long long num;
  
                          switch (spec.type) {
  
                          case FORMAT_TYPE_LONG_LONG:
                                  num = get_arg(long long);
                                  break;
                          case FORMAT_TYPE_ULONG:
                          case FORMAT_TYPE_LONG:
                                  num = get_arg(unsigned long);
                                  break;
                          case FORMAT_TYPE_SIZE_T:
                                  num = get_arg(size_t);
                                  break;
                          case FORMAT_TYPE_PTRDIFF:
                                  num = get_arg(ptrdiff_t);
                                  break;
                          case FORMAT_TYPE_UBYTE:
                                  num = get_arg(unsigned char);
                                  break;
                          case FORMAT_TYPE_BYTE:
                                  num = get_arg(signed char);
                                  break;
                          case FORMAT_TYPE_USHORT:
                                  num = get_arg(unsigned short);
                                  break;
                          case FORMAT_TYPE_SHORT:
                                  num = get_arg(short);
                                  break;
                          case FORMAT_TYPE_UINT:
                                  num = get_arg(unsigned int);
                                  break;
                          default:
                                  num = get_arg(int);
                          }
  
                          str = number(str, end, num, spec);
                  } /* default: */
                  } /* switch(spec.type) */
          } /* while(*fmt) */
  
          if (size > 0) {
                  if (str < end)
                          *str = '\0';
                  else
                          end[-1] = '\0';
          }
  
  #undef get_arg
  
          /* the trailing null byte doesn't count towards the total */
          return str - buf;
  }
  EXPORT_SYMBOL_GPL(bstr_printf);
  
  /**
   * bprintf - Parse a format string and place args' binary value in a buffer
   * @bin_buf: The buffer to place args' binary value
   * @size: The size of the buffer(by words(32bits), not characters)
   * @fmt: The format string to use
   * @...: Arguments for the format string
   *
   * The function returns the number of words(u32) written
   * into @bin_buf.
   */
  int bprintf(u32 *bin_buf, size_t size, const char *fmt, ...)
  {
          va_list args;
          int ret;
  
          va_start(args, fmt);
          ret = vbin_printf(bin_buf, size, fmt, args);
          va_end(args);
  
          return ret;
  }
  EXPORT_SYMBOL_GPL(bprintf);
  
  #endif /* CONFIG_BINARY_PRINTF */
  
  /**
   * vsscanf - Unformat a buffer into a list of arguments
   * @buf:        input buffer
   * @fmt:        format of buffer
   * @args:       arguments
   */
  int vsscanf(const char *buf, const char *fmt, va_list args)
  {
          const char *str = buf;
          char *next;
          char digit;
          int num = 0;
          u8 qualifier;
          unsigned int base;
          union {
                  long long s;
                  unsigned long long u;
          } val;
          s16 field_width;
          bool is_sign;
  
          while (*fmt) {
                  /* skip any white space in format */
                  /* white space in format matchs any amount of
                   * white space, including none, in the input.
                   */
                  if (isspace(*fmt)) {
                          fmt = skip_spaces(++fmt);
                          str = skip_spaces(str);
                  }
  
                  /* anything that is not a conversion must match exactly */
                  if (*fmt != '%' && *fmt) {
                          if (*fmt++ != *str++)
                                  break;
                          continue;
                  }
  
                  if (!*fmt)
                          break;
                  ++fmt;
  
                  /* skip this conversion.
                   * advance both strings to next white space
                   */
                  if (*fmt == '*') {
                          if (!*str)
                                  break;
                          while (!isspace(*fmt) && *fmt != '%' && *fmt)
                                  fmt++;
                          while (!isspace(*str) && *str)
                                  str++;
                          continue;
                  }
  
                  /* get field width */
                  field_width = -1;
                  if (isdigit(*fmt)) {
                          field_width = skip_atoi(&fmt);
                          if (field_width <= 0)
                                  break;
                  }
  
                  /* get conversion qualifier */
                  qualifier = -1;
                  if (*fmt == 'h' || _tolower(*fmt) == 'l' ||
                      _tolower(*fmt) == 'z') {
                          qualifier = *fmt++;
                          if (unlikely(qualifier == *fmt)) {
                                  if (qualifier == 'h') {
                                          qualifier = 'H';
                                          fmt++;
                                  } else if (qualifier == 'l') {
                                          qualifier = 'L';
                                          fmt++;
                                  }
                          }
                  }
  
                  if (!*fmt)
                          break;
  
                  if (*fmt == 'n') {
                          /* return number of characters read so far */
                          *va_arg(args, int *) = str - buf;
                          ++fmt;
                          continue;
                  }
  
                  if (!*str)
                          break;
  
                  base = 10;
                  is_sign = 0;
  
                  switch (*fmt++) {
                  case 'c':
                  {
                          char *s = (char *)va_arg(args, char*);
                          if (field_width == -1)
                                  field_width = 1;
                          do {
                                  *s++ = *str++;
                          } while (--field_width > 0 && *str);
                          num++;
                  }
                  continue;
                  case 's':
                  {
                          char *s = (char *)va_arg(args, char *);
                          if (field_width == -1)
                                  field_width = SHRT_MAX;
                          /* first, skip leading white space in buffer */
                          str = skip_spaces(str);
  
                          /* now copy until next white space */
                          while (*str && !isspace(*str) && field_width--)
                                  *s++ = *str++;
                          *s = '\0';
                          num++;
                  }
                  continue;
                  case 'o':
                          base = 8;
                          break;
                  case 'x':
                  case 'X':
                          base = 16;
                          break;
                  case 'i':
                          base = 0;
                  case 'd':
                          is_sign = 1;
                  case 'u':
                          break;
                  case '%':
                          /* looking for '%' in str */
                          if (*str++ != '%')
                                  return num;
                          continue;
                  default:
                          /* invalid format; stop here */
                          return num;
                  }
  
                  /* have some sort of integer conversion.
                   * first, skip white space in buffer.
                   */
                  str = skip_spaces(str);
  
                  digit = *str;
                  if (is_sign && digit == '-')
                          digit = *(str + 1);
  
                  if (!digit
                      || (base == 16 && !isxdigit(digit))
                      || (base == 10 && !isdigit(digit))
                      || (base == 8 && (!isdigit(digit) || digit > '7'))
                      || (base == 0 && !isdigit(digit)))
                          break;
  
                  if (is_sign)
                          val.s = qualifier != 'L' ?
                                  simple_strtol(str, &next, base) :
                                  simple_strtoll(str, &next, base);
                  else
                          val.u = qualifier != 'L' ?
                                  simple_strtoul(str, &next, base) :
                                  simple_strtoull(str, &next, base);
  
                  if (field_width > 0 && next - str > field_width) {
                          if (base == 0)
                                  _parse_integer_fixup_radix(str, &base);
                          while (next - str > field_width) {
                                  if (is_sign)
                                          val.s = div_s64(val.s, base);
                                  else
                                          val.u = div_u64(val.u, base);
                                  --next;
                          }
                  }
  
                  switch (qualifier) {
                  case 'H':       /* that's 'hh' in format */
                          if (is_sign)
                                  *va_arg(args, signed char *) = val.s;
                          else
                                  *va_arg(args, unsigned char *) = val.u;
                          break;
                  case 'h':
                          if (is_sign)
                                  *va_arg(args, short *) = val.s;
                          else
                                  *va_arg(args, unsigned short *) = val.u;
                          break;
                  case 'l':
                          if (is_sign)
                                  *va_arg(args, long *) = val.s;
                          else
                                  *va_arg(args, unsigned long *) = val.u;
                          break;
                  case 'L':
                          if (is_sign)
                                  *va_arg(args, long long *) = val.s;
                          else
                                  *va_arg(args, unsigned long long *) = val.u;
                          break;
                  case 'Z':
                  case 'z':
                          *va_arg(args, size_t *) = val.u;
                          break;
                  default:
                          if (is_sign)
                                  *va_arg(args, int *) = val.s;
                          else
                                  *va_arg(args, unsigned int *) = val.u;
                          break;
                  }
                  num++;
  
                  if (!next)
                          break;
                  str = next;
          }
  
          return num;
  }
  EXPORT_SYMBOL(vsscanf);
  
  /**
   * sscanf - Unformat a buffer into a list of arguments
   * @buf:        input buffer
   * @fmt:        formatting of buffer
   * @...:        resulting arguments
   */
  int sscanf(const char *buf, const char *fmt, ...)
  {
          va_list args;
          int i;
  
          va_start(args, fmt);
          i = vsscanf(buf, fmt, args);
          va_end(args);
  
          return i;
  }
  EXPORT_SYMBOL(sscanf);

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