Re: [PATCH 03/14] ARM: remove duplicate memcpy() definition

[Linus Walleij]

On Tue, Sep 28, 2021 at 5:42 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:

> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> Both the decompressor code and the kasan logic try to override
> the memcpy() and memmove()  definitions, which leading to a clash
> in a KASAN-enabled kernel with XZ decompression:
>
> arch/arm/boot/compressed/decompress.c:50:9: error: 'memmove' macro redefined [-Werror,-Wmacro-redefined]
>  #define memmove memmove
>         ^
> arch/arm/include/asm/string.h:59:9: note: previous definition is here
>  #define memmove(dst, src, len) __memmove(dst, src, len)
>         ^
> arch/arm/boot/compressed/decompress.c:51:9: error: 'memcpy' macro redefined [-Werror,-Wmacro-redefined]
>  #define memcpy memcpy
>         ^
> arch/arm/include/asm/string.h:58:9: note: previous definition is here
>  #define memcpy(dst, src, len) __memcpy(dst, src, len)
>         ^
>
> Here we want the set of functions from the decompressor, so undefine
> the other macros before the override.
>
> Fixes: d6d51a96c7d6 ("ARM: 9014/2: Replace string mem* functions for KASan")
> Fixes: a7f464f3db93 ("ARM: 7001/2: Wire up support for the XZ decompressor")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Solves this, right?
https://lore.kernel.org/lkml/202105091112.F5rmd4By-lkp@xxxxxxxxx/

Can you put in a reported-by and Link: to this so we got it tracked?

>  #ifdef CONFIG_KERNEL_XZ
> +#undef memmove
>  #define memmove memmove
> +#undef memcpy
>  #define memcpy memcpy
>  #include "../../../../lib/decompress_unxz.c"
>  #endif

That's clever, maybe drop a small comment in the code why we do this
pretty unintuitive looking thing and how this works?

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Yours,
Linus Walleij