Re: [PATCH v2 02/17] vdso: Clean header inclusion in getrandom

Jason A. Donenfeld
2024-08-26T13:17:38Z

On Mon, Aug 26, 2024 at 12:45:40PM +0200, Christophe Leroy wrote:
>
>
> Le 26/08/2024 à 10:58, Jason A. Donenfeld a écrit :
> > On Mon, Aug 26, 2024 at 10:37:49AM +0200, Christophe Leroy wrote:
> >>
> >>
> >> Le 26/08/2024 à 10:07, Jason A. Donenfeld a écrit :
> >>> On Thu, Aug 22, 2024 at 09:13:10AM +0200, Christophe Leroy wrote:
> >>>>
> >>>> +#define _PAGE_SIZE (1UL << CONFIG_PAGE_SHIFT)
> >>>> +#define _PAGE_MASK (~(_PAGE_SIZE - 1))
> >>>
> >>> If PAGE_SIZE isn't defined at this point, why not just call it PAGE_SIZE
> >>> instead of _PAGE_SIZE? But if that's the case, why not put the vdso
> >>> definition of PAGE_SIZE into some vdso header included by this file?
> >>
> >> It was working ok on powerpc but on x86 I got:
> >
> > Seems like there might be some more fiddling to do, then? Or did you
> > conclude it's impossible?
>
> Maybe someone who knows x86 in details could helps but after a first
> look I gave up because it looks very x86 specific, indeed that's
> x86/asm/vdso/gettimeofday.h that pulls several x86/asm/ headers , and
> the same type of issue might arise for any new architecture coming in.
>
> For me it looked cleaner to just do as commit cffaefd15a8f ("vdso: Use
> CONFIG_PAGE_SHIFT in vdso/datapage.h") and not use PAGE_SIZE at all. But
> I didn't want to directly use (1UL << CONFIG_PAGE_SHIFT) and (~(1UL <<
> (CONFIG_PAGE_SHIFT - 1))) in the code directly hence the new macros with
> a leading underscore to avoid any conflict with existing macros.

If that's the case and you can't sort it out or it's impossible, then it
seems like adding #ifndef PAGE_SIZE, #define... inside of some vdso header
(not inside getrandom.c) would make sense.

Jason