[PACTH v2] powerpc/pseries/mce: Avoid instrumentation in realmode

[Ganesh]

On 9/7/22 09:49, Nicholas Piggin wrote:

> On Mon Sep 5, 2022 at 4:38 PM AEST, Ganesh Goudar wrote:
>> Part of machine check error handling is done in realmode,
>> As of now instrumentation is not possible for any code that
>> runs in realmode.
>> When MCE is injected on KASAN enabled kernel, crash is
>> observed, Hence force inline or mark no instrumentation
>> for functions which can run in realmode, to avoid KASAN
>> instrumentation.
>>
>> Signed-off-by: Ganesh Goudar<ganeshgr at linux.ibm.com>
>> ---
>> v2: Force inline few more functions.
>> ---
>>   arch/powerpc/include/asm/hw_irq.h    | 8 ++++----
>>   arch/powerpc/include/asm/interrupt.h | 2 +-
>>   arch/powerpc/include/asm/rtas.h      | 4 ++--
>>   arch/powerpc/kernel/rtas.c           | 4 ++--
>>   4 files changed, 9 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
>> index 26ede09c521d..3264991fe524 100644
>> --- a/arch/powerpc/include/asm/hw_irq.h
>> +++ b/arch/powerpc/include/asm/hw_irq.h
>> @@ -111,7 +111,7 @@ static inline void __hard_RI_enable(void)
>>   #ifdef CONFIG_PPC64
>>   #include <asm/paca.h>
>>   
>> -static inline notrace unsigned long irq_soft_mask_return(void)
>> +static __always_inline notrace unsigned long irq_soft_mask_return(void)
>>   {
>>   	return READ_ONCE(local_paca->irq_soft_mask);
>>   }
>> @@ -121,7 +121,7 @@ static inline notrace unsigned long irq_soft_mask_return(void)
>>    * for the critical section and as a clobber because
>>    * we changed paca->irq_soft_mask
>>    */
>> -static inline notrace void irq_soft_mask_set(unsigned long mask)
>> +static __always_inline notrace void irq_soft_mask_set(unsigned long mask)
>>   {
>>   	/*
>>   	 * The irq mask must always include the STD bit if any are set.
> This doesn't give a reason why it's __always_inline, and having the
> notrace attribute makes it possibly confusing. I think it would be easy
> for someone to break without realising. Could you add a noinstr to these
> instead / as well?

Yeah we can add noinstr. Missed to see your comment, Sorry for the delayed reply

>
> What about adding a 'realmode' function annotation that includes noinstr?

You mean to define a new function annotation?

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