linux-kernel - Re: [PATCH v7 07/11] powerpc/32: prepare shadow area for KASAN

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Date:   Tue, 26 Feb 2019 16:12:29 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org
Subject: Re: [PATCH v7 07/11] powerpc/32: prepare shadow area for KASAN

Christophe Leroy <christophe.leroy@....fr> writes:

> This patch prepares a shadow area for KASAN.
>
> The shadow area will be at the top of the kernel virtual
> memory space above the fixmap area and will occupy one
> eighth of the total kernel virtual memory space.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>  arch/powerpc/Kconfig              |  5 +++++
>  arch/powerpc/include/asm/fixmap.h |  5 +++++
>  arch/powerpc/include/asm/kasan.h  | 17 +++++++++++++++++
>  arch/powerpc/mm/mem.c             |  4 ++++
>  arch/powerpc/mm/ptdump/ptdump.c   |  8 ++++++++
>  5 files changed, 39 insertions(+)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 652c25260838..f446e016f4a1 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -382,6 +382,11 @@ config PGTABLE_LEVELS
>  	default 3 if PPC_64K_PAGES && !PPC_BOOK3S_64
>  	default 4
>  
> +config KASAN_SHADOW_OFFSET
> +	hex
> +	depends on KASAN
> +	default 0xe0000000
> +

Should this live in Kconfig.debug?

Regards,
Daniel

>  source "arch/powerpc/sysdev/Kconfig"
>  source "arch/powerpc/platforms/Kconfig"
>  
> diff --git a/arch/powerpc/include/asm/fixmap.h b/arch/powerpc/include/asm/fixmap.h
> index b9fbed84ddca..51a1a309c919 100644
> --- a/arch/powerpc/include/asm/fixmap.h
> +++ b/arch/powerpc/include/asm/fixmap.h
> @@ -22,7 +22,12 @@
>  #include <asm/kmap_types.h>
>  #endif
>  
> +#ifdef CONFIG_KASAN
> +#include <asm/kasan.h>
> +#define FIXADDR_TOP	KASAN_SHADOW_START
> +#else
>  #define FIXADDR_TOP	((unsigned long)(-PAGE_SIZE))
> +#endif
>  
>  /*
>   * Here we define all the compile-time 'special' virtual
> diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
> index 2efd0e42cfc9..b554d3bd3e2c 100644
> --- a/arch/powerpc/include/asm/kasan.h
> +++ b/arch/powerpc/include/asm/kasan.h
> @@ -12,4 +12,21 @@
>  #define EXPORT_SYMBOL_KASAN(fn)	EXPORT_SYMBOL(fn)
>  #endif
>  
> +#ifndef __ASSEMBLY__
> +
> +#include <asm/page.h>
> +#include <asm/pgtable-types.h>
> +
> +#define KASAN_SHADOW_SCALE_SHIFT	3
> +
> +#define KASAN_SHADOW_OFFSET	ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
> +
> +#define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
> +				 (PAGE_OFFSET >> KASAN_SHADOW_SCALE_SHIFT))
> +
> +#define KASAN_SHADOW_END	0UL
> +
> +#define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
> +
> +#endif /* __ASSEMBLY */
>  #endif
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index f6787f90e158..4e7fa4eb2dd3 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -309,6 +309,10 @@ void __init mem_init(void)
>  	mem_init_print_info(NULL);
>  #ifdef CONFIG_PPC32
>  	pr_info("Kernel virtual memory layout:\n");
> +#ifdef CONFIG_KASAN
> +	pr_info("  * 0x%08lx..0x%08lx  : kasan shadow mem\n",
> +		KASAN_SHADOW_START, KASAN_SHADOW_END);
> +#endif
>  	pr_info("  * 0x%08lx..0x%08lx  : fixmap\n", FIXADDR_START, FIXADDR_TOP);
>  #ifdef CONFIG_HIGHMEM
>  	pr_info("  * 0x%08lx..0x%08lx  : highmem PTEs\n",
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index 37138428ab55..812ed680024f 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -101,6 +101,10 @@ static struct addr_marker address_markers[] = {
>  	{ 0,	"Fixmap start" },
>  	{ 0,	"Fixmap end" },
>  #endif
> +#ifdef CONFIG_KASAN
> +	{ 0,	"kasan shadow mem start" },
> +	{ 0,	"kasan shadow mem end" },
> +#endif
>  	{ -1,	NULL },
>  };
>  
> @@ -322,6 +326,10 @@ static void populate_markers(void)
>  #endif
>  	address_markers[i++].start_address = FIXADDR_START;
>  	address_markers[i++].start_address = FIXADDR_TOP;
> +#ifdef CONFIG_KASAN
> +	address_markers[i++].start_address = KASAN_SHADOW_START;
> +	address_markers[i++].start_address = KASAN_SHADOW_END;
> +#endif
>  #endif /* CONFIG_PPC64 */
>  }
>  
> -- 
> 2.13.3