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

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

[Arnd Bergmann]

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>
---
 arch/arm/mm/kasan_init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
index 9c348042a724..4b1619584b23 100644
--- a/arch/arm/mm/kasan_init.c
+++ b/arch/arm/mm/kasan_init.c
@@ -226,7 +226,7 @@ void __init kasan_init(void)
 	BUILD_BUG_ON(pgd_index(KASAN_SHADOW_START) !=
 		     pgd_index(KASAN_SHADOW_END));
 	memcpy(tmp_pmd_table,
-	       pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_START)),
+	       (void*)pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_START)),
 	       sizeof(tmp_pmd_table));
 	set_pgd(&tmp_pgd_table[pgd_index(KASAN_SHADOW_START)],
 		__pgd(__pa(tmp_pmd_table) | PMD_TYPE_TABLE | L_PGD_SWAPPER));
-- 
2.29.2

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

[Linus Walleij]

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