[PATCH] powerpc/kasan/book3s_64: warn when running with hash MMU

[Christophe Leroy]

Le 11/10/2022 à 12:25, Christophe Leroy a écrit :
> 
> 
> Le 11/10/2022 à 12:00, Michael Ellerman a écrit :
>> Nathan Lynch <nathanl at linux.ibm.com> writes:
>>> Michael Ellerman <mpe at ellerman.id.au> writes:
>>>> Christophe Leroy <christophe.leroy at csgroup.eu> writes:
>>>>> + KASAN list
>>>>>
>>>>> Le 06/10/2022 à 06:10, Michael Ellerman a écrit :
>>>>>> Nathan Lynch <nathanl at linux.ibm.com> writes:
>>>>>>> kasan is known to crash at boot on book3s_64 with non-radix MMU. As
>>>>>>> noted in commit 41b7a347bf14 ("powerpc: Book3S 64-bit outline-only
>>>>>>> KASAN support"):
>>>>>>>
>>>>>>>      A kernel with CONFIG_KASAN=y will crash during boot on a machine
>>>>>>>      using HPT translation because not all the entry points to the
>>>>>>>      generic KASAN code are protected with a call to kasan_arch_is_ready().
>>>>>>
>>>>>> I guess I thought there was some plan to fix that.
>>>>>
>>>>> I was thinking the same.
>>>>>
>>>>> Do we have a list of the said entry points to the generic code that are
>>>>> lacking a call to kasan_arch_is_ready() ?
>>>>>
>>>>> Typically, the BUG dump below shows that kasan_byte_accessible() is
>>>>> lacking the check. It should be straight forward to add
>>>>> kasan_arch_is_ready() check to kasan_byte_accessible(), shouldn't it ?
>>>>
>>>> Yes :)
>>>>
>>>> And one other spot, but the patch below boots OK for me. I'll leave it
>>>> running for a while just in case there's a path I've missed.
>>>
>>> It works for me too, thanks (p8 pseries qemu).
>>
>> It works but I still see the kasan shadow getting mapped, which we would
>> ideally avoid.
>>
>>   From PTDUMP:
>>
>> ---[ kasan shadow mem start ]---
>> 0xc00f000000000000-0xc00f00000006ffff  0x00000000045e0000       448K         r  w       pte  valid  present        dirty  accessed
>> 0xc00f3ffffffe0000-0xc00f3fffffffffff  0x0000000004d80000       128K         r  w       pte  valid  present        dirty  accessed
>>
>> I haven't worked out how those are getting mapped.
> 
> 

Alternative patch proposed at 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/150768c55722311699fdcf8f5379e8256749f47d.1674716617.git.christophe.leroy@csgroup.eu/

Christophe