Re: [PATCH] ARM: kasan: work around LPAE build warning

From: Linus Walleij <linus.walleij@linaro.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	Ard Biesheuvel <ardb@kernel.org>, Mike Rapoport <rppt@kernel.org>,
	Abbott Liu <liuwenliang@huawei.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Alexander Potapenko <glider@google.com>,
	Andrey Konovalov <andreyknvl@gmail.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ARM: kasan: work around LPAE build warning
Date: Sat, 24 Jul 2021 00:51:32 +0200	[thread overview]
Message-ID: <CACRpkdb3DMvof3-xdtss0Pc6KM36pJA-iy=WhvtNVnsDpeJ24Q@mail.gmail.com> (raw)
In-Reply-To: <20210721151706.2439073-1-arnd@kernel.org>

On Wed, Jul 21, 2021 at 5:17 PM Arnd Bergmann <arnd@kernel.org> wrote:

> From: Arnd Bergmann <arnd@arndb.de>
>
> pgd_page_vaddr() returns an 'unsigned long' address, causing a warning
> with the memcpy() call in kasan_init():
>
> arch/arm/mm/kasan_init.c: In function 'kasan_init':
> include/asm-generic/pgtable-nop4d.h:44:50: error: passing argument 2 of '__memcpy' makes pointer from integer without a cast [-Werror=int-conversion]
>    44 | #define pgd_page_vaddr(pgd)                     ((unsigned long)(p4d_pgtable((p4d_t){ pgd })))
>       |                                                 ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>       |                                                  |
>       |                                                  long unsigned int
> arch/arm/include/asm/string.h:58:45: note: in definition of macro 'memcpy'
>    58 | #define memcpy(dst, src, len) __memcpy(dst, src, len)
>       |                                             ^~~
> arch/arm/mm/kasan_init.c:229:16: note: in expansion of macro 'pgd_page_vaddr'
>   229 |                pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_START)),
>       |                ^~~~~~~~~~~~~~
> arch/arm/include/asm/string.h:21:47: note: expected 'const void *' but argument is of type 'long unsigned int'
>    21 | extern void *__memcpy(void *dest, const void *src, __kernel_size_t n);
>       |                                   ~~~~~~~~~~~~^~~
>
> Avoid this by adding an explicit typecast.
>
> Fixes: 5615f69bc209 ("ARM: 9016/2: Initialize the mapping of KASan shadow memory")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

I can't think of anything better.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Will you add this patch to Russell's patch tracker?

Yours,
Linus Walleij