Re: [PATCH v2 05/17] vdso: Avoid call to memset() by getrandom

[Christophe Leroy]

Le 29/08/2024 à 20:02, Segher Boessenkool a écrit :
> On Thu, Aug 29, 2024 at 07:36:38PM +0200, Christophe Leroy wrote:
> > Le 28/08/2024 à 19:25, Segher Boessenkool a écrit :
> > > > Not sure about static binaries, though: do those even use the VDSO?
> > >
> > > With "static binary" people usually mean "a binary not using any DSOs",
> > > I think the VDSO is a DSO, also in this respect?  As always, -static
> > > builds are *way* less problematic (and faster and smaller :-) )
> >
> > AFAIK on powerpc even static binaries use the vDSO, otherwise signals
> > don't work.
>
> How can that work?  Non-dynamic binaries do not use ld.so (that is the
> definition of a dynamic binary, even).  So they cannot link (at runtime)
> to any DSO (unless that is done manually?!)
>
> Maybe there is something at a fixed offset in the vDSO, or something
> like that?  Is this documented somewhere?

You've got some explanation here : 
https://github.com/torvalds/linux/blob/master/Documentation/ABI/stable/vdso