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

Matthew Wilcox
2018-12-21T18:25:26Z

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;