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

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Message-ID: <9a39d910-2a05-3ce7-c949-296db2d458b9@c-s.fr>
Date:   Tue, 18 Dec 2018 09:18:42 +0000
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()



On 12/18/2018 03:05 AM, Jonathan Neuschäfer wrote:
> On Mon, Dec 17, 2018 at 10:29:18AM +0100, Christophe Leroy wrote:
>>> With patches 1-3:
>>> [    0.000000] setbat(0, c0000000, 00000000, 01000000, 311)
>>> [    0.000000] setbat(2, c1000000, 01000000, 00800000, 311)
>>> [    0.000000] setbat(4, d0000000, 10000000, 02000000, 791)
>>
>> What we see is that BAT0 is not used in the origin. I have always wondered
>> the reason, maybe there is something odd behind and BAT0 shall no ne used.
>>
>> Could you try and modify find_free_bat() so that it starts at b = 1 instead
>> of b = 0 ?
> 
> In this case, setbat is called with index 2, 3, and 4, but the Wii still
> doesn't boot.
> 
>>> According to arch/powerpc/include/asm/book3s/32/hash.h,
>>>    - 0x591 = _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_COHERENT | _PAGE_PRESENT
>>>    - 0x311 = _PAGE_EXEC | _PAGE_ACCESSED | _PAGE_COHERENT | _PAGE_PRESENT
>>>    - 0x791 = _PAGE_RW | _PAGE_EXEC | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_COHERENT | _PAGE_PRESENT
>>>
>>
>> Yes, patch 1 added _PAGE_EXEC which explains this 0x200.
>> Do you confirm it still works well with only patch 1 ?
> 
> Patch 1 alone boots to userspace.
> 

Ok, thanks for testing.

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 ?

diff --git b/arch/powerpc/mm/ppc_mmu_32.c a/arch/powerpc/mm/ppc_mmu_32.c
index 61c10ee00ba2..628fba266663 100644
--- b/arch/powerpc/mm/ppc_mmu_32.c
+++ a/arch/powerpc/mm/ppc_mmu_32.c
@@ -119,7 +119,7 @@ unsigned long __init mmu_mapin_ram(unsigned long 
base, unsigned long top)

  		if (size < 128 << 10)
  			break;
-		setbat(idx, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
+		setbat(idx, PAGE_OFFSET + base, base, size, PAGE_KERNEL_X);
  		base += size;
  	}

I think we may have some code trying to modify the kernel text without 
using code patching functions.

Thanks,
Christophe


> 
> Jonathan
>