690d137f44
_parse_integer() does one or two division instructions (which are slow) per digit parsed to perform the overflow check. Furthermore, these are particularly expensive examples of division instruction as the number of clock cycles required to complete them may go up with the position of the most significant set bit in the dividend: if (*res > div_u64(ULLONG_MAX - val, base)) which is as maximal as possible. Worse, on 32-bit arches, more than one of these division instructions may be required per digit. So, assuming we don't support a base of more than 16, skip the check if the top nibble of the result is not set at this point. Signed-off-by: David Howells <dhowells@redhat.com> [ Changed it to not dereference the pointer all the time - even if the compiler can and does optimize it away, the code just looks cleaner. And edited the top nybble test slightly to make the code generated on x86-64 better in the loop - test against a hoisted constant instead of shifting and testing the result ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
285 lines
6.0 KiB
C
285 lines
6.0 KiB
C
/*
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* Convert integer string representation to an integer.
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* If an integer doesn't fit into specified type, -E is returned.
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*
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* Integer starts with optional sign.
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* kstrtou*() functions do not accept sign "-".
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*
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* Radix 0 means autodetection: leading "0x" implies radix 16,
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* leading "0" implies radix 8, otherwise radix is 10.
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* Autodetection hints work after optional sign, but not before.
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*
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* If -E is returned, result is not touched.
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*/
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#include <linux/ctype.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/math64.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <asm/uaccess.h>
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#include "kstrtox.h"
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const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
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{
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if (*base == 0) {
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if (s[0] == '0') {
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if (_tolower(s[1]) == 'x' && isxdigit(s[2]))
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*base = 16;
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else
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*base = 8;
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} else
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*base = 10;
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}
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if (*base == 16 && s[0] == '0' && _tolower(s[1]) == 'x')
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s += 2;
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return s;
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}
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/*
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* Convert non-negative integer string representation in explicitly given radix
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* to an integer.
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* Return number of characters consumed maybe or-ed with overflow bit.
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* If overflow occurs, result integer (incorrect) is still returned.
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*
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* Don't you dare use this function.
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*/
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unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p)
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{
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unsigned long long res;
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unsigned int rv;
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int overflow;
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res = 0;
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rv = 0;
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overflow = 0;
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while (*s) {
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unsigned int val;
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if ('0' <= *s && *s <= '9')
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val = *s - '0';
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else if ('a' <= _tolower(*s) && _tolower(*s) <= 'f')
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val = _tolower(*s) - 'a' + 10;
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else
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break;
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if (val >= base)
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break;
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/*
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* Check for overflow only if we are within range of
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* it in the max base we support (16)
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*/
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if (unlikely(res & (~0ull << 60))) {
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if (res > div_u64(ULLONG_MAX - val, base))
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overflow = 1;
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}
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res = res * base + val;
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rv++;
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s++;
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}
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*p = res;
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if (overflow)
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rv |= KSTRTOX_OVERFLOW;
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return rv;
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}
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static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res)
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{
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unsigned long long _res;
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unsigned int rv;
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s = _parse_integer_fixup_radix(s, &base);
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rv = _parse_integer(s, base, &_res);
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if (rv & KSTRTOX_OVERFLOW)
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return -ERANGE;
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rv &= ~KSTRTOX_OVERFLOW;
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if (rv == 0)
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return -EINVAL;
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s += rv;
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if (*s == '\n')
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s++;
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if (*s)
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return -EINVAL;
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*res = _res;
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return 0;
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}
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int kstrtoull(const char *s, unsigned int base, unsigned long long *res)
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{
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if (s[0] == '+')
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s++;
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return _kstrtoull(s, base, res);
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}
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EXPORT_SYMBOL(kstrtoull);
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int kstrtoll(const char *s, unsigned int base, long long *res)
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{
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unsigned long long tmp;
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int rv;
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if (s[0] == '-') {
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rv = _kstrtoull(s + 1, base, &tmp);
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if (rv < 0)
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return rv;
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if ((long long)(-tmp) >= 0)
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return -ERANGE;
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*res = -tmp;
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} else {
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rv = kstrtoull(s, base, &tmp);
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if (rv < 0)
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return rv;
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if ((long long)tmp < 0)
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return -ERANGE;
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*res = tmp;
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}
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return 0;
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}
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EXPORT_SYMBOL(kstrtoll);
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/* Internal, do not use. */
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int _kstrtoul(const char *s, unsigned int base, unsigned long *res)
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{
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unsigned long long tmp;
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int rv;
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rv = kstrtoull(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (unsigned long long)(unsigned long)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(_kstrtoul);
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/* Internal, do not use. */
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int _kstrtol(const char *s, unsigned int base, long *res)
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{
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long long tmp;
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int rv;
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rv = kstrtoll(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (long long)(long)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(_kstrtol);
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int kstrtouint(const char *s, unsigned int base, unsigned int *res)
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{
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unsigned long long tmp;
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int rv;
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rv = kstrtoull(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (unsigned long long)(unsigned int)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(kstrtouint);
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int kstrtoint(const char *s, unsigned int base, int *res)
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{
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long long tmp;
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int rv;
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rv = kstrtoll(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (long long)(int)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(kstrtoint);
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int kstrtou16(const char *s, unsigned int base, u16 *res)
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{
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unsigned long long tmp;
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int rv;
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rv = kstrtoull(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (unsigned long long)(u16)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(kstrtou16);
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int kstrtos16(const char *s, unsigned int base, s16 *res)
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{
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long long tmp;
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int rv;
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rv = kstrtoll(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (long long)(s16)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(kstrtos16);
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int kstrtou8(const char *s, unsigned int base, u8 *res)
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{
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unsigned long long tmp;
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int rv;
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rv = kstrtoull(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (unsigned long long)(u8)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(kstrtou8);
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int kstrtos8(const char *s, unsigned int base, s8 *res)
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{
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long long tmp;
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int rv;
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rv = kstrtoll(s, base, &tmp);
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if (rv < 0)
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return rv;
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if (tmp != (long long)(s8)tmp)
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return -ERANGE;
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*res = tmp;
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return 0;
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}
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EXPORT_SYMBOL(kstrtos8);
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#define kstrto_from_user(f, g, type) \
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int f(const char __user *s, size_t count, unsigned int base, type *res) \
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{ \
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/* sign, base 2 representation, newline, terminator */ \
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char buf[1 + sizeof(type) * 8 + 1 + 1]; \
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\
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count = min(count, sizeof(buf) - 1); \
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if (copy_from_user(buf, s, count)) \
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return -EFAULT; \
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buf[count] = '\0'; \
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return g(buf, base, res); \
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} \
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EXPORT_SYMBOL(f)
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kstrto_from_user(kstrtoull_from_user, kstrtoull, unsigned long long);
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kstrto_from_user(kstrtoll_from_user, kstrtoll, long long);
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kstrto_from_user(kstrtoul_from_user, kstrtoul, unsigned long);
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kstrto_from_user(kstrtol_from_user, kstrtol, long);
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kstrto_from_user(kstrtouint_from_user, kstrtouint, unsigned int);
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kstrto_from_user(kstrtoint_from_user, kstrtoint, int);
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kstrto_from_user(kstrtou16_from_user, kstrtou16, u16);
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kstrto_from_user(kstrtos16_from_user, kstrtos16, s16);
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kstrto_from_user(kstrtou8_from_user, kstrtou8, u8);
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kstrto_from_user(kstrtos8_from_user, kstrtos8, s8);
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