Re: [PATCH] random: vDSO: Redefine PAGE_SIZE and PAGE_MASK

[Christophe Leroy]

Hi Vincenzo,

Le 29/08/2024 à 14:01, Vincenzo Frascino a écrit :
> Hi Christophe,
>
> On 27/08/2024 18:14, Christophe Leroy wrote:
> > Le 27/08/2024 à 18:05, Vincenzo Frascino a écrit :
> > > Hi Christophe,
> > >
> > > On 27/08/2024 11:49, Christophe Leroy wrote:
> > >
> > > ...
>
> ...
>
> > > Could you please clarify where minmax is needed? I tried to build Jason's master
> > > tree for x86, commenting the header and it seems building fine. I might be
> > > missing something.
> >
> > Without it:
> >
> >    VDSO32C arch/powerpc/kernel/vdso/vgetrandom-32.o
> > In file included from /home/chleroy/linux-powerpc/lib/vdso/getrandom.c:11,
> >                   from <command-line>:
> ...
>
> > > > Same for ARRAY_SIZE(->reserved) by the way, easy to do opencode, we also have it
> > > > only once
> > >
> > > I have a similar issue to figure out why linux/array_size.h and
> > > uapi/linux/random.h are needed. It seems that I can build the object without
> > > them. Could you please explain?
> >
> > Without linux/array_size.h:
> >
> >    VDSO32C arch/powerpc/kernel/vdso/vgetrandom-32.o
> > In file included from <command-line>:
> > /home/chleroy/linux-powerpc/lib/vdso/getrandom.c: In function
> > '__cvdso_getrandom_data':
> > /home/chleroy/linux-powerpc/lib/vdso/getrandom.c:89:40: error: implicit
> If this is the case, those headers should be defined for the powerpc
> implementation only. The generic implementation should be interpreted as the
> minimum common denominator in between all the architectures for what concerns
> the headers.

Sorry, I disagree. You can't rely on necessary headers being included 
indirectly by other arch specific headers. getrandom.c uses 
ARRAY_SIZE(), it must include the header that defines ARRAY_SIZE().

At the moment, on x86 you get linux/array.h by change through the 
following chain, that the reason why the build doesn't break:

In file included from ./include/linux/kernel.h:16,
                 from ./include/linux/cpumask.h:11,
                 from ./arch/x86/include/asm/cpumask.h:5,
                 from ./arch/x86/include/asm/msr.h:11,
                 from ./arch/x86/include/asm/vdso/gettimeofday.h:19,
                 from ./include/vdso/datapage.h:164,
                 from 
arch/x86/entry/vdso/../../../../lib/vdso/getrandom.c:9,

From my point of view you can't expect such a chain from each architecture.

Christophe