Re: [PATCH 01/12] x86_64: memset_user()

[Matthew Wilcox]

On Fri, Dec 21, 2018 at 08:14:12PM +0200, Igor Stoppa wrote:
> +unsigned long __memset_user(void __user *addr, int c, unsigned long size)
> +{
> +     long __d0;
> +     unsigned long  pattern = 0;
> +     int i;
> +
> +     for (i = 0; i < 8; i++)
> +             pattern = (pattern << 8) | (0xFF & c);

That's inefficient.

        pattern = (unsigned char)c;
        pattern |= pattern << 8;
        pattern |= pattern << 16;
        pattern |= pattern << 32;