Re: [PATCH] preempt: Move PREEMPT_RT before PREEMPT in vermagic.

[Petr Pavlu]

On 12/5/24 17:06, Sebastian Andrzej Siewior wrote:
> Since the dynamic preemption has been enabled for PREEMPT_RT we have now
> CONFIG_PREEMPT and CONFIG_PREEMPT_RT set simultaneously. This affects
> the vermagic strings which comes now PREEMPT with PREEMPT_RT enabled.
> 
> The PREEMPT_RT module usually can not be loaded on a PREEMPT kernel
> because some symbols are missing.
> However if the symbols are fine then it continues and it crashes later.
> The problem is that the struct module has a different layout and the
> num_exentries or init members are at a different position leading to a
> crash later on. This is not necessary caught by the size check in
> elf_validity_cache_index_mod() because the mem member has an alignment
> requirement of __module_memory_align which is big enough keep the total
> size unchanged. Therefore we should keep the string accurate instead of
> removing it.
> 
> Move the PREEMPT_RT check before the PREEMPT so that it takes precedence
> if both symbols are enabled.
> 
> Fixes: 35772d627b55c ("sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Reviewed-by: Petr Pavlu <petr.pavlu@xxxxxxxx>

I'm going to wait for a few days if others want to comment and then plan
to take this through the modules tree for 6.13-rcX fixes.

[Luis asked me to look after the modules tree for a while, with the plan
to rotate it.]

-- 
Thanks,
Petr