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

[Linus Walleij]

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

> From: Arnd Bergmann <arnd at 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 at arndb.de>

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

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

Yours,
Linus Walleij