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SubjectRe: [PATCH v3 1/2] arm: kasan: support CONFIG_KASAN_VMALLOC
On Sun, Feb 27, 2022 at 09:47:25PM +0800, Lecopzer Chen wrote:
> Simply make shadow of vmalloc area mapped on demand.
>
> Since the virtual address of vmalloc for Arm is also between
> MODULE_VADDR and 0x100000000 (ZONE_HIGHMEM), which means the shadow
> address has already included between KASAN_SHADOW_START and
> KASAN_SHADOW_END.
> Thus we need to change nothing for memory map of Arm.
>
> This can fix ARM_MODULE_PLTS with KASan, support KASan for higmem
> and provide the first step to support CONFIG_VMAP_STACK with Arm.
>
> Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
> ---
> arch/arm/Kconfig | 1 +
> arch/arm/include/asm/kasan_def.h | 11 ++++++++++-
> arch/arm/mm/kasan_init.c | 6 +++++-
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 4c97cb40eebb..78250e246cc6 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -72,6 +72,7 @@ config ARM
> select HAVE_ARCH_KFENCE if MMU && !XIP_KERNEL
> select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
> select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
> + select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN
> select HAVE_ARCH_MMAP_RND_BITS if MMU
> select HAVE_ARCH_PFN_VALID
> select HAVE_ARCH_SECCOMP
> diff --git a/arch/arm/include/asm/kasan_def.h b/arch/arm/include/asm/kasan_def.h
> index 5739605aa7cf..96fd1d3b5a0c 100644
> --- a/arch/arm/include/asm/kasan_def.h
> +++ b/arch/arm/include/asm/kasan_def.h
> @@ -19,7 +19,16 @@
> * space to use as shadow memory for KASan as follows:
> *
> * +----+ 0xffffffff
> - * | | \
> + * | |\
> + * | | |-> ZONE_HIGHMEM for vmalloc virtual address space.
> + * | | | Such as vmalloc(), GFP_HIGHUSER (__GFP__HIGHMEM),
> + * | | | module address using ARM_MODULE_PLTS, etc.
> + * | | |
> + * | | | If CONFIG_KASAN_VMALLOC=y, this area would populate
> + * | | | shadow address on demand.
> + * | |/

This diagram is incorrect. We already have the memory layout in
Documentation/arm/memory.rst, so we don't need another set of
documentation that is misleading.

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