Re: [PATCH] powerpc/kasan: KASAN is not supported on RELOCATABLE && FSL_BOOKE

[Christophe Leroy]

Le 29/11/2019 Ã 08:04, Lexi Shao a ÃcritÂ:
> CONFIG_RELOCATABLE and CONFIG_KASAN cannot be enabled at the same time
> on ppce500 fsl_booke. All functions called before kasan_early_init()
> should be disabled with kasan check. When CONFIG_RELOCATABLE is enabled
> on ppce500 fsl_booke, relocate_init() is called before kasan_early_init()
> which triggers kasan check and results in boot failure.
> Call trace and functions which triggers kasan check(*):
>    - _start
>     - set_ivor
>      - relocate_init(*)
>       - early_get_first_memblock_info(*)
>        - of_scan_flat_dt(*)
> 	...
>      - kasan_early_init
>
> Potential solutions could be 1. implement relocate_init and all its children
> function in a seperate file or 2. introduce a global vairable in KASAN, only
> enable KASAN check when init is done.

Solution 1 seems uneasy. of_scan_flat_dt() and children are general 
functions that can't be set aside.
Solution 2 would destroy performance, and would anyway not work with 
inline instrumentation.

Have you tried moving the call to kasan_early_init() before the call of 
relocate_init() ?
On other PPC32, kasan_early_init() is the first thing done after 
activating the MMU. But AFAIU, MMU is always active on BOOKE though.

Christophe

> Disable KASAN when RELOCATABLE is selected on fsl_booke for now until
> it is supported.
>
> Signed-off-by: Lexi Shao <shaolexi@xxxxxxxxxx>
> ---
>   arch/powerpc/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 3e56c9c2f16e..14f3da63c088 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -171,7 +171,7 @@ config PPC
>   	select HAVE_ARCH_AUDITSYSCALL
>   	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
>   	select HAVE_ARCH_JUMP_LABEL
> -	select HAVE_ARCH_KASAN			if PPC32
> +	select HAVE_ARCH_KASAN			if PPC32 && !(RELOCATABLE && FSL_BOOKE)
>   	select HAVE_ARCH_KGDB
>   	select HAVE_ARCH_MMAP_RND_BITS
>   	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT