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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Tue, 18 Sep 2018 19:09:22 +0200
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Subject: Re: [PATCH v6 06/18] khwasan, arm64: untag virt address in
 __kimg_to_phys and _virt_addr_is_linear
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
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On Wed, Sep 12, 2018 at 6:33 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
> On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov <andreyknvl@google.com> wrote:

>> +#ifdef CONFIG_KASAN_HW
>> +#define KASAN_TAG_SHIFTED(tag)         ((unsigned long)(tag) << 56)
>> +#define KASAN_SET_TAG(addr, tag)       (((addr) & ~KASAN_TAG_SHIFTED(0xff)) | \
>> +                                               KASAN_TAG_SHIFTED(tag))
>> +#define KASAN_RESET_TAG(addr)          KASAN_SET_TAG(addr, 0xff)
>> +#endif
>> +
>
>
> Wouldn't it be better to
> #define KASAN_RESET_TAG(addr) addr
> when CONFIG_KASAN_HW is not enabled, and then not duplicate the macros
> below? That's what we do in kasan.h for all hooks.
> I see that a subsequent patch duplicates yet another macro in this
> file. While we could use:
>
> #define __kimg_to_phys(addr)   (KASAN_RESET_TAG(addr) - kimage_voffset)
>
> with and without kasan. Duplicating them increases risk that somebody
> will change only the non-kasan version but forget kasan version.

Will do in v7.