Re: [PATCH v3 00/13] Kernel address sanitizer - runtime memory debugger.

[Andrey Ryabinin]

2014-09-26 21:07 GMT+04:00 Dmitry Vyukov <dvyukov@xxxxxxxxxx>:
> On Fri, Sep 26, 2014 at 10:01 AM, Sasha Levin <sasha.levin@xxxxxxxxxx> wrote:
>> On 09/24/2014 08:43 AM, Andrey Ryabinin wrote:
>>> Hi.
>>>
>>> This is a third iteration of kerenel address sanitizer (KASan).
>>>
>>> KASan is a runtime memory debugger designed to find use-after-free
>>> and out-of-bounds bugs.
>>>
>>> Currently KASAN supported only for x86_64 architecture and requires kernel
>>> to be build with SLUB allocator.
>>> KASAN uses compile-time instrumentation for checking every memory access, therefore you
>>> will need a fresh GCC >= v5.0.0.
>>
>> Hi Andrey,
>>
>> I tried this patchset, with the latest gcc, and I'm seeing the following:
>>
>> arch/x86/kernel/head.o: In function `_GLOBAL__sub_I_00099_0_reserve_ebda_region':
>> /home/sasha/linux-next/arch/x86/kernel/head.c:71: undefined reference to `__asan_init_v4'
>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0___ksymtab_system_state':
>> /home/sasha/linux-next/init/main.c:1034: undefined reference to `__asan_init_v4'
>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_init_uts_ns':
>> /home/sasha/linux-next/init/version.c:50: undefined reference to `__asan_init_v4'
>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_root_mountflags':
>> /home/sasha/linux-next/init/do_mounts.c:638: undefined reference to `__asan_init_v4'
>> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_rd_prompt':
>> /home/sasha/linux-next/init/do_mounts_rd.c:361: undefined reference to `__asan_init_v4'
>> init/built-in.o:/home/sasha/linux-next/init/do_mounts_md.c:312: more undefined references to `__asan_init_v4' follow
>>
>>
>> What am I missing?
>
>
> Emission of __asan_init_vx needs to be disabled when
> -fsanitize=kernel-address. Our kernel does not boot with them at all.
> It probably hits some limit for something that can be increased. But I
> don't want to investigate what that limit is, as __asan_init is not
> needed for kasan at all.
>

__asan_init_vx maybe not needed for kernel, but we still need somehow
to identify
compiler's asan version (e.g. for globals).
We could add some define to GCC or just something like this in kernel:
#if __GNUC__ == 5
#define ASAN_V4
....

-- 
Best regards,
Andrey Ryabinin
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