linux-kernel - Re: [PATCH v1 03/13] powerpc/mm/32s: rework mmu_mapin

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Date:   Tue, 18 Dec 2018 15:15:49 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>
Cc:     linuxppc-dev@...ts.ozlabs.org, Paul Mackerras <paulus@...ba.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 03/13] powerpc/mm/32s: rework mmu_mapin_ram()



Le 18/12/2018 à 15:07, Jonathan Neuschäfer a écrit :
> On Tue, Dec 18, 2018 at 09:18:42AM +0000, Christophe Leroy wrote:
>> The only difference I see then are the flags. Everything else is seems
>> identical.
>>
>> I know you tried already, but would you mind trying once more with the
>> following change ?
>>
> [...]
>> -		setbat(idx, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
>> +		setbat(idx, PAGE_OFFSET + base, base, size, PAGE_KERNEL_X);
> 
> Good call, with this workaround on top of patches 1-3, it boots again:
> 
> 	# mount -t debugfs d /sys/kernel/debug
> 	# cat /sys/kernel/debug/powerpc/block_address_translation
> 	---[ Instruction Block Address Translation ]---
> 	0: 0xc0000000-0xc0ffffff 0x00000000 Kernel EXEC
> 	1:         -
> 	2: 0xc1000000-0xc17fffff 0x01000000 Kernel EXEC
> 	3:         -
> 	4: 0xd0000000-0xd1ffffff 0x10000000 Kernel EXEC
> 	5:         -
> 	6:         -
> 	7:         -
> 
> 	---[ Data Block Address Translation ]---
> 	0: 0xc0000000-0xc0ffffff 0x00000000 Kernel RW
> 	1: 0xfffe0000-0xffffffff 0x0d000000 Kernel RW no cache guarded
> 	2: 0xc1000000-0xc17fffff 0x01000000 Kernel RW
> 	3:         -
> 	4: 0xd0000000-0xd1ffffff 0x10000000 Kernel RW
> 	5:         -
> 	6:         -
> 	7:         -
> 
>> I think we may have some code trying to modify the kernel text without using
>> code patching functions.
> 
> Is there any faster way than to sprinkle some printks in setup_kernel
> and try to find the guilty piece of code this way?

Can you start with the serie 
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=75072 ?

Christophe

> 
> 
> Jonathan
>