[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