Re: [PATCH] powerpc: Inline setup_kup()

[Michael Ellerman <mpe@ellerman.id.au>]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 14/12/2020 à 13:30, Michael Ellerman a écrit :
>> setup_kup() is used by both 64-bit and 32-bit code. However on 64-bit
>> it must not be __init, because it's used for CPU hotplug, whereas on
>> 32-bit it should be __init because it calls setup_kuap/kuep() which
>> are __init.
>> 
>> We worked around that problem in the past by marking it __ref, see
>> commit 67d53f30e23e ("powerpc/mm: fix section mismatch for
>> setup_kup()").
>> 
>> Marking it __ref basically just omits it from section mismatch
>> checking, which can lead to bugs, and in fact it did, see commit
>> 44b4c4450f8d ("powerpc/64s: Mark the kuap/kuep functions non __init")
>> 
>> We can avoid all these problems by just making it static inline.
>> Because all it does is call other functions, making it inline actually
>> shrinks the 32-bit vmlinux by ~76 bytes.
>> 
>> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>> ---
>>   arch/powerpc/include/asm/kup.h | 8 ++++++--
>>   arch/powerpc/mm/init-common.c  | 6 ------
>>   2 files changed, 6 insertions(+), 8 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
>> index 5a9820c54da9..46b12c6dc728 100644
>> --- a/arch/powerpc/include/asm/kup.h
>> +++ b/arch/powerpc/include/asm/kup.h
>> @@ -49,8 +49,6 @@ extern bool disable_kuap;
>>   
>>   #include <linux/pgtable.h>
>>   
>> -void setup_kup(void);
>> -
>>   #ifdef CONFIG_PPC_KUEP
>>   void setup_kuep(bool disabled);
>>   #else
>> @@ -85,6 +83,12 @@ static inline void restore_user_access(unsigned long flags) { }
>>   #endif /* CONFIG_PPC_BOOK3S_64 */
>>   #endif /* CONFIG_PPC_KUAP */
>>   
>> +static inline void setup_kup(void)
>
> Should it be __always_inline ?

Yes I guess so, will fix. Thanks for reviewing.

cheers