Date:   Wed, 12 Dec 2018 16:10:32 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <bp@...en8.de>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
        <keescook@...omium.org>, <msys.mizuma@...il.com>,
        <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>
Subject: Re: [PATCH v13 1/6] x86/boot: Introduce kstrtoull() to boot
 directory instead of simple_strtoull()

On Wed, Dec 12, 2018 at 03:46:15PM +0800, Baoquan He wrote:
>On 12/12/18 at 11:10am, Chao Fan wrote:
>> Introduce kstrtoull() from lib/kstrtox.c to boot directory so that code
>
>It's not introducing kstrtoull(), just copying kstrtoull() from
>lib/kstrtox.c to boot.

Oops, maybe I misunderstand 'introduce'.

Thanks,
Chao Fan

>
>> in boot/ can use kstrtoull() and the old simple_strtoull() can be
>> replaced.
>> 
>> Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
>> ---
>>  arch/x86/boot/string.c | 137 +++++++++++++++++++++++++++++++++++++++++
>>  arch/x86/boot/string.h |   2 +
>>  2 files changed, 139 insertions(+)
>> 
>> diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
>> index c4428a176973..e02405f20f98 100644
>> --- a/arch/x86/boot/string.c
>> +++ b/arch/x86/boot/string.c
>> @@ -12,7 +12,10 @@
>>   * Very basic string functions
>>   */
>>  
>> +#define _LINUX_CTYPE_H
>>  #include <linux/types.h>
>> +#include <linux/kernel.h>
>> +#include <linux/errno.h>
>>  #include <asm/asm.h>
>>  #include "ctype.h"
>>  #include "string.h"
>> @@ -187,3 +190,137 @@ char *strchr(const char *s, int c)
>>  			return NULL;
>>  	return (char *)s;
>>  }
>> +
>> +static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
>> +{
>> +	union {
>> +		u64 v64;
>> +		u32 v32[2];
>> +	} d = { dividend };
>> +	u32 upper;
>> +
>> +	upper = d.v32[1];
>> +	d.v32[1] = 0;
>> +	if (upper >= divisor) {
>> +		d.v32[1] = upper / divisor;
>> +		upper %= divisor;
>> +	}
>> +	asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) :
>> +		"rm" (divisor), "0" (d.v32[0]), "1" (upper));
>> +	return d.v64;
>> +}
>> +
>> +static inline u64 div_u64(u64 dividend, u32 divisor)
>> +{
>> +	u32 remainder;
>> +	return div_u64_rem(dividend, divisor, &remainder);
>> +}
>> +
>> +static inline char _tolower(const char c)
>> +{
>> +	return c | 0x20;
>> +}
>> +
>> +const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
>> +{
>> +	if (*base == 0) {
>> +		if (s[0] == '0') {
>> +			if (_tolower(s[1]) == 'x' && isxdigit(s[2]))
>> +				*base = 16;
>> +			else
>> +				*base = 8;
>> +		} else
>> +			*base = 10;
>> +	}
>> +	if (*base == 16 && s[0] == '0' && _tolower(s[1]) == 'x')
>> +		s += 2;
>> +	return s;
>> +}
>> +
>> +/*
>> + * Convert non-negative integer string representation in explicitly given radix
>> + * to an integer.
>> + * Return number of characters consumed maybe or-ed with overflow bit.
>> + * If overflow occurs, result integer (incorrect) is still returned.
>> + *
>> + * Don't you dare use this function.
>> + */
>> +unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p)
>> +{
>> +	unsigned long long res;
>> +	unsigned int rv;
>> +
>> +	res = 0;
>> +	rv = 0;
>> +	while (1) {
>> +		unsigned int c = *s;
>> +		unsigned int lc = c | 0x20; /* don't tolower() this line */
>> +		unsigned int val;
>> +
>> +		if ('0' <= c && c <= '9')
>> +			val = c - '0';
>> +		else if ('a' <= lc && lc <= 'f')
>> +			val = lc - 'a' + 10;
>> +		else
>> +			break;
>> +
>> +		if (val >= base)
>> +			break;
>> +		/*
>> +		 * Check for overflow only if we are within range of
>> +		 * it in the max base we support (16)
>> +		 */
>> +		if (unlikely(res & (~0ull << 60))) {
>> +			if (res > div_u64(ULLONG_MAX - val, base))
>> +				rv |= KSTRTOX_OVERFLOW;
>> +		}
>> +		res = res * base + val;
>> +		rv++;
>> +		s++;
>> +	}
>> +	*p = res;
>> +	return rv;
>> +}
>> +
>> +static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res)
>> +{
>> +	unsigned long long _res;
>> +	unsigned int rv;
>> +
>> +	s = _parse_integer_fixup_radix(s, &base);
>> +	rv = _parse_integer(s, base, &_res);
>> +	if (rv & KSTRTOX_OVERFLOW)
>> +		return -ERANGE;
>> +	if (rv == 0)
>> +		return -EINVAL;
>> +	s += rv;
>> +	if (*s == '\n')
>> +		s++;
>> +	if (*s)
>> +		return -EINVAL;
>> +	*res = _res;
>> +	return 0;
>> +}
>> +
>> +/**
>> + * kstrtoull - convert a string to an unsigned long long
>> + * @s: The start of the string. The string must be null-terminated, and may also
>> + *  include a single newline before its terminating null. The first character
>> + *  may also be a plus sign, but not a minus sign.
>> + * @base: The number base to use. The maximum supported base is 16. If base is
>> + *  given as 0, then the base of the string is automatically detected with the
>> + *  conventional semantics - If it begins with 0x the number will be parsed as a
>> + *  hexadecimal (case insensitive), if it otherwise begins with 0, it will be
>> + *  parsed as an octal number. Otherwise it will be parsed as a decimal.
>> + * @res: Where to write the result of the conversion on success.
>> + *
>> + * Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error.
>> + * Used as a replacement for the obsolete simple_strtoull. Return code must
>> + * be checked.
>> + */
>> +int kstrtoull(const char *s, unsigned int base, unsigned long long *res)
>> +{
>> +	if (s[0] == '+')
>> +		s++;
>> +	return _kstrtoull(s, base, res);
>> +}
>> diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h
>> index 3d78e27077f4..171007c99acc 100644
>> --- a/arch/x86/boot/string.h
>> +++ b/arch/x86/boot/string.h
>> @@ -29,4 +29,6 @@ extern unsigned int atou(const char *s);
>>  extern unsigned long long simple_strtoull(const char *cp, char **endp,
>>  					  unsigned int base);
>>  
>> +int kstrtoull(const char *s, unsigned int base, unsigned long long *res);
>> +#define KSTRTOX_OVERFLOW       (1U << 31)
>>  #endif /* BOOT_STRING_H */
>> -- 
>> 2.19.2
>> 
>> 
>> 
>
>

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