[BISECTED] kexec regression on PowerBook G4

[Christophe Leroy]

Hi Aero,

Le 22/05/2019 à 00:18, Aaro Koskinen a écrit :
> Hi,
> 
> I was trying to upgrade from v5.0 -> v5.1 on PowerBook G4, but when trying
> to kexec a kernel the system gets stuck (no errors seen on the console).

Do you mean you are trying to kexec a v5.1 kernel from a v5.0 kernel, or 
do you have a working v5.1 kernel, but kexec doesn't work with it ?

> 
> Bisected to: 93c4a162b014 ("powerpc/6xx: Store PGDIR physical address
> in a SPRG"). This commit doesn't revert cleanly anymore but I tested
> that the one before works OK.

Not sure that's the problem. There was a problem with that commit, but 
it was fixed by 4622a2d43101 ("powerpc/6xx: fix setup and use of 
SPRN_SPRG_PGDIR for hash32").
You probably hit some commit between those two during bisect, that's 
likely the reason why you ended here.

Can you restart your bisect from 4622a2d43101 ?

If you have CONFIG_SMP, maybe you should also consider taking 
397d2300b08c ("powerpc/32s: fix flush_hash_pages() on SMP"). Stable 
5.1.4 includes it.

> 
> With current Linus HEAD (9c7db5004280), it gets a bit further but still
> doesn't work: now I get an error on the console after kexec "Starting
> new kernel! ... Bye!":
> 
> 	kernel tried to execute exec-protected page (...) - exploit attempt?

Interesting.

Do you have CONFIG_STRICT_KERNEL_RWX=y in your .config ? If so, can you 
retry without it ?

Thanks
Christophe

> 
> A.
>