Re: userland clock_gettime proof of concept

[Paul Irofti]

În 22 iunie 2020 00:15:59 EEST, Christian Weisgerber <na...@mips.inka.de> a 
scris:
>Paul Irofti:
>
>[Unrelated, just to mark where we're at]
>> Right. Just reproduced it here. This moves the check at the top so
>that
>> each CPU checks its own skew and disables tc_user if necessary.
>
>I tweaked the patch locally to make _timekeep a visible global
>symbol in libc.
>
>Printing its value has revealed two issues:
>
>* The timekeep page is mapped to the same address for every process.
>  It changes across reboots, but once running, it's always the same.
>  kettenis suggested
>  - vaddr_t va;
>  + vaddr_t va = 0;
>  in exec_timekeep_map(), but that doesn't make a difference.

The va is set a few lines down the line. No point in initialization. This is 
identical behavior to the emul mapping  before timekeep.

>* I'm indeed seeing init(8) with _timekeep == NULL.

Probably because it is the first process? If you want to follow this read the 
kernel init bits and the syscall exec bits.