linux-kernel - Re: [PATCH v13 1/6] x86/boot: Introduce kstrtoull() to boot directory instead of simple

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Date:   Thu, 13 Dec 2018 13:50:59 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, keescook@...omium.org,
        bhe@...hat.com, 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 11:10:48AM +0800, Chao Fan wrote:
> Introduce kstrtoull() from lib/kstrtox.c to boot directory so that code
> 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;
> +}

Why aren't you using the simple one from include/linux/math64.h ?

Rest looks ok.

-- 
Regards/Gruss,
    Boris.

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