Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7

[H. Peter Anvin]

On 02/03/2012 09:32 AM, H. Peter Anvin wrote:
> On 02/03/2012 01:28 AM, Cyrill Gorcunov wrote:
> > static __init int kcmp_cookie_init(void)
> > {
> > int i, j;
> >
> > for (i = 0; i< KCMP_TYPES; i++) {
> > for (j = 0; j< 2; j++)
> > get_random_bytes(&cookies[i][j], sizeof(long));
> > cookies[i][1] |= (~(~0UL>> 1) | 1);
> > }
> >
> > return 0;
> > }
> >
> > I thought in first place that sizeof(cookies[i][j]) would allow me
> > to change type of cookies in one place (ie at declaration) but
> > if cookies type will be changed -- the code will need careful review
> > anway, so sizeof(long) will be enough I think.
> >
> > On the other hands, maybe more clean variant will be
> >
> > static __init int kcmp_cookie_init(void)
> > {
> > const int size = sizeof(cookies[0][0]);
> > int i, j;
> >
> > for (i = 0; i< KCMP_TYPES; i++) {
> > for (j = 0; j< 2; j++)
> > get_random_bytes(&cookies[i][j], size);
> > cookies[i][1] |= (~(~0UL>> 1) | 1);
> > }
>
> How about:
>
> const int size = sizeof(cookies[0]);
>
> get_random_bytes(&cookies[i], size);
>
> ... and skip the completely unnecessary for loop?

Even better:

static __init int kcmp_cookie_init(void)
{
	int i;

	get_random_bytes(cookies, sizeof cookies);

	for (i = 0; i < KCMP_TYPES; i++)
		cookies[i][1] |= ~(~0UL >> 1) | 1;
}

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