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

Christophe Leroy
2024-08-26T10:45:42Z

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.

Christophe