linux-kernel - Re: [PATCH] powerpc/4xx: Fix setup

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Message-ID: <920c4c49-5185-a0d5-0ab2-484effc307cc@csgroup.eu>
Date:   Tue, 29 Jun 2021 14:06:49 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/4xx: Fix setup_kuep() on SMP



Le 29/06/2021 à 13:58, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@...roup.eu> 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@...el.com>
>> 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@...roup.eu>
>> ---
>>   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.