[PATCH v6 11/22] powerpc/book3s64/pkeys: Inherit correctly on fork.

[Aneesh Kumar K.V]

On 11/25/20 7:24 PM, Christophe Leroy wrote:
> 
> 
> Le 25/11/2020 à 06:16, Aneesh Kumar K.V a écrit :
>> Child thread.kuap value is inherited from the parent in 
>> copy_thread_tls. We still
>> need to make sure when the child returns from a fork in the kernel we 
>> start with the kernel
>> default AMR value.
>>
>> Reviewed-by: Sandipan Das <sandipan at linux.ibm.com>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>> ---
>>   arch/powerpc/kernel/process.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/process.c 
>> b/arch/powerpc/kernel/process.c
>> index b6b8a845e454..733680de0ba4 100644
>> --- a/arch/powerpc/kernel/process.c
>> +++ b/arch/powerpc/kernel/process.c
>> @@ -1768,6 +1768,17 @@ int copy_thread(unsigned long clone_flags, 
>> unsigned long usp,
>>           childregs->ppr = DEFAULT_PPR;
>>       p->thread.tidr = 0;
>> +#endif
>> +    /*
>> +     * Run with the current AMR value of the kernel
>> +     */
>> +#ifdef CONFIG_PPC_KUAP
>> +    if (mmu_has_feature(MMU_FTR_KUAP))
>> +        kregs->kuap = AMR_KUAP_BLOCKED;
>> +#endif
> 
> Do we need that ifdef at all ?
> 
> Shouldn't mmu_has_feature(MMU_FTR_KUAP) be always false and get 
> optimised out when CONFIG_PPC_KUAP is not defined ?
> 
>> +#ifdef CONFIG_PPC_KUEP
>> +    if (mmu_has_feature(MMU_FTR_KUEP))
>> +        kregs->iamr = AMR_KUEP_BLOCKED;
> 
> Same ?
> 
>>   #endif
>>       kregs->nip = ppc_function_entry(f);
>>       return 0;
>>

Not really. I did hit a compile error with this patch on 
mpc885_ads_defconfig and that required me to do

modified   arch/powerpc/kernel/process.c
@@ -1772,11 +1772,10 @@ int copy_thread(unsigned long clone_flags, 
unsigned long usp,
  	/*
  	 * Run with the current AMR value of the kernel
  	 */
-#ifdef CONFIG_PPC_KUAP
+#ifdef CONFIG_PPC_PKEY
  	if (mmu_has_feature(MMU_FTR_KUAP))
-		kregs->kuap = AMR_KUAP_BLOCKED;
-#endif
-#ifdef CONFIG_PPC_KUEP
+		kregs->amr = AMR_KUAP_BLOCKED;
+
  	if (mmu_has_feature(MMU_FTR_KUEP))
  		kregs->iamr = AMR_KUEP_BLOCKED;
  #endif