Re: [PATCH v10 02/17] x86_64: add KASan support

[Andrew Morton]

On Thu, 29 Jan 2015 18:11:46 +0300 Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> wrote:

> This patch adds arch specific code for kernel address sanitizer.
> 
> 16TB of virtual addressed used for shadow memory.
> It's located in range [ffffec0000000000 - fffffc0000000000]
> between vmemmap and %esp fixup stacks.
> 
> At early stage we map whole shadow region with zero page.
> Latter, after pages mapped to direct mapping address range
> we unmap zero pages from corresponding shadow (see kasan_map_shadow())
> and allocate and map a real shadow memory reusing vmemmap_populate()
> function.
> 
> Also replace __pa with __pa_nodebug before shadow initialized.
> __pa with CONFIG_DEBUG_VIRTUAL=y make external function call (__phys_addr)
> __phys_addr is instrumented, so __asan_load could be called before
> shadow area initialized.
> 
> ...
>
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -5,6 +5,7 @@ if HAVE_ARCH_KASAN
>  
>  config KASAN
>  	bool "AddressSanitizer: runtime memory debugger"
> +	depends on !MEMORY_HOTPLUG
>  	help
>  	  Enables address sanitizer - runtime memory debugger,
>  	  designed to find out-of-bounds accesses and use-after-free bugs.

That's a significant restriction.  It has obvious runtime implications.
It also means that `make allmodconfig' and `make allyesconfig' don't
enable kasan, so compile coverage will be impacted.

This wasn't changelogged.  What's the reasoning and what has to be done
to fix it?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/