linux-kernel - Re: [PATCH v4 2/7] mm: kasan: introduce generic kasan_populate_zero

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Date:	Mon, 10 Aug 2015 15:00:05 +0300
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel@...ts.infradead.org,
	Arnd Bergmann <arnd@...db.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	David Keitel <dkeitel@...eaurora.org>,
	Alexander Potapenko <glider@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexey Klimov <klimov.linux@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v4 2/7] mm: kasan: introduce generic kasan_populate_zero_shadow()

2015-08-10 9:01 GMT+03:00 Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>:
> Andrey Ryabinin <a.ryabinin@...sung.com> writes:
>
>> Introduce generic kasan_populate_zero_shadow(start, end).
>> This function maps kasan_zero_page to the [start, end] addresses.
>>
>> In follow on patches it will be used for ARMv8 (and maybe other
>> architectures) and will replace x86_64 specific populate_zero_shadow().
>>
>> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
>
> This assume that we can have shared pgtable_t in generic code ? Is that
> true for generic code ? Even if it is we may want to allow some arch to
> override this ? On ppc64, we store the hardware hash page table slot
> number in pte_t, Hence we won't be able to share pgtable_t.
>

So, ppc64 could define some config which will disable compilation of
mm/kasan/kasan_init.c.
However, it might be a bad idea to use such never defined config symbol now.
So I think this could be done later, in "KASAN for powerpc" series.

>
>
>> ---
>>  arch/x86/mm/kasan_init_64.c |  14 ----
>>  include/linux/kasan.h       |   8 +++
>>  mm/kasan/Makefile           |   2 +-
>>  mm/kasan/kasan_init.c       | 151 ++++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 160 insertions(+), 15 deletions(-)
>>  create mode 100644 mm/kasan/kasan_init.c
>>
>> diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
>> index e1840f3..812086c 100644
>> --- a/arch/x86/mm/kasan_init_64.c
>> +++ b/arch/x86/mm/kasan_init_64.c
>> @@ -12,20 +12,6 @@
>>  extern pgd_t early_level4_pgt[PTRS_PER_PGD];
>>  extern struct range pfn_mapped[E820_X_MAX];
>>
>> -static pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
>> -static pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss;
>> -static pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss;
>> -
>> -/*
>
> -aneesh
>
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