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From:   Daniel Axtens <dja@axtens.net>
To:     Christophe Leroy <christophe.leroy@c-s.fr>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linuxppc-dev@lists.ozlabs.org, kasan-dev@googlegroups.com,
        aneesh.kumar@linux.ibm.com, bsingharora@gmail.com
Cc:     Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v6 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support
In-Reply-To: <5e392944-50ac-ed06-5896-2664894335d9@c-s.fr>
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Date:   Wed, 12 Feb 2020 23:16:21 +1100
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Christophe Leroy <christophe.leroy@c-s.fr> writes:

> Le 12/02/2020 =C3=A0 11:12, Daniel Axtens a =C3=A9crit=C2=A0:
>> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>>=20
>>> Le 12/02/2020 =C3=A0 06:47, Daniel Axtens a =C3=A9crit=C2=A0:
>>>> diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/a=
sm/kasan.h
>>>> index fbff9ff9032e..2911fdd3a6a0 100644
>>>> --- a/arch/powerpc/include/asm/kasan.h
>>>> +++ b/arch/powerpc/include/asm/kasan.h
>>>> @@ -2,6 +2,8 @@
>>>>    #ifndef __ASM_KASAN_H
>>>>    #define __ASM_KASAN_H
>>>>=20=20=20=20
>>>> +#include <asm/page.h>
>>>> +
>>>>    #ifdef CONFIG_KASAN
>>>>    #define _GLOBAL_KASAN(fn)	_GLOBAL(__##fn)
>>>>    #define _GLOBAL_TOC_KASAN(fn)	_GLOBAL_TOC(__##fn)
>>>> @@ -14,29 +16,41 @@
>>>>=20=20=20=20
>>>>    #ifndef __ASSEMBLY__
>>>>=20=20=20=20
>>>> -#include <asm/page.h>
>>>> -
>>>>    #define KASAN_SHADOW_SCALE_SHIFT	3
>>>>=20=20=20=20
>>>>    #define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
>>>>    				 (PAGE_OFFSET >> KASAN_SHADOW_SCALE_SHIFT))
>>>>=20=20=20=20
>>>> +#ifdef CONFIG_KASAN_SHADOW_OFFSET
>>>>    #define KASAN_SHADOW_OFFSET	ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
>>>> +#endif
>>>>=20=20=20=20
>>>> +#ifdef CONFIG_PPC32
>>>>    #define KASAN_SHADOW_END	0UL
>>>>=20=20=20=20
>>>> -#define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
>>>> +#ifdef CONFIG_KASAN
>>>> +void kasan_late_init(void);
>>>> +#else
>>>> +static inline void kasan_late_init(void) { }
>>>> +#endif
>>>> +
>>>> +#endif
>>>> +
>>>> +#ifdef CONFIG_PPC_BOOK3S_64
>>>> +#define KASAN_SHADOW_END	(KASAN_SHADOW_OFFSET + \
>>>> +				 (RADIX_VMEMMAP_END >> KASAN_SHADOW_SCALE_SHIFT))
>>>> +
>>>> +static inline void kasan_late_init(void) { }
>>>> +#endif
>>>>=20=20=20=20
>>>>    #ifdef CONFIG_KASAN
>>>>    void kasan_early_init(void);
>>>>    void kasan_mmu_init(void);
>>>>    void kasan_init(void);
>>>> -void kasan_late_init(void);
>>>>    #else
>>>>    static inline void kasan_init(void) { }
>>>>    static inline void kasan_mmu_init(void) { }
>>>> -static inline void kasan_late_init(void) { }
>>>>    #endif
>>>
>>> Why modify all this kasan_late_init() stuff ?
>>>
>>> This function is only called from kasan init_32.c, it is never called by
>>> PPC64, so you should not need to modify anything at all.
>>=20
>> I got a compile error for a missing symbol. I'll repro it and attach it.
>>=20
>
> Oops, sorry. I looked too quickly. It is defined in kasan_init_32.c and=20
> called from mm/mem.c
>
> We don't have a performance issue here, since this is called only once=20
> during startup. Could you define an empty kasan_late_init() in=20
> init_book3s_64.c instead ?

Yeah, I can do that, will respin tomorrow.

Would you mind having a quick check of the documentation changes in
patches 2 and 4? I just want to confirm I've accurately captured the
state of ppc32 kasan work.

Thanks!
Daniel
>
> Christophe