Re: [PATCH] powerpc/4xx: Fix setup_kuep() on SMP

[Christophe Leroy]

Le 29/06/2021 à 13:58, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@xxxxxxxxxx> writes:
> > On SMP, setup_kuep() is also called from start_secondary() since
> > commit 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").
> >
> > start_secondary() is not an __init function.
> >
> > Remove the __init marker from setup_kuep() and bail out when
> > not caller on the first CPU as the work is already done.
> >
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Fixes: 10248dcba120 ("powerpc/44x: Implement Kernel Userspace Exec Protection (KUEP)")
> > Fixes: 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   arch/powerpc/mm/nohash/44x.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/mm/nohash/44x.c b/arch/powerpc/mm/nohash/44x.c
> > index 7da6d1e9fc9b..20c18bd5b9a0 100644
> > --- a/arch/powerpc/mm/nohash/44x.c
> > +++ b/arch/powerpc/mm/nohash/44x.c
> > @@ -241,8 +241,11 @@ void __init mmu_init_secondary(int cpu)
> >   #endif /* CONFIG_SMP */
> >   
> >   #ifdef CONFIG_PPC_KUEP
> > -void __init setup_kuep(bool disabled)
> > +void setup_kuep(bool disabled)
> >   {
> > +	if (smp_processor_id() != boot_cpuid)
> > +		return;
> > +
> >   	if (disabled)
> >   		patch_instruction_site(&patch__tlb_44x_kuep, ppc_inst(PPC_RAW_NOP()));
> >   	else
>
> Building ppc44x_defconfig gives me:
>
>    /linux/arch/powerpc/mm/nohash/44x.c: In function 'setup_kuep':
>    /linux/arch/powerpc/mm/nohash/44x.c:246:35: error: 'boot_cpuid' undeclared (first use in this function); did you mean 'boot_cpu_init'?
>      246 |         if (smp_processor_id() != boot_cpuid)
>          |                                   ^~~~~~~~~~
>          |                                   boot_cpu_init
>    /linux/arch/powerpc/mm/nohash/44x.c:246:35: note: each undeclared identifier is reported only once for each function it appears in


Seems like we need <asm/smp.h> when we don't have CONFIG_SMP.

I tested it with akebono_defconfig, looks like it has CONFIG_SMP.