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Subject: Re: [PATCH 1/2] riscv: Add memmove string operation.
To:     Nick Hu <nickhu@andestech.com>
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From:   Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <92dd5f5f-c8a2-53c3-4d61-44acc4366844@virtuozzo.com>
Date:   Tue, 27 Aug 2019 12:33:11 +0300
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On 8/27/19 12:07 PM, Nick Hu wrote:
> Hi Andrey
> 
> On Thu, Aug 22, 2019 at 11:59:02PM +0800, Andrey Ryabinin wrote:
>> On 8/7/19 10:19 AM, Nick Hu wrote:
>>> There are some features which need this string operation for compilation,
>>> like KASAN. So the purpose of this porting is for the features like KASAN
>>> which cannot be compiled without it.
>>>
>>
>> Compilation error can be fixed by diff bellow (I didn't test it).
>> If you don't need memmove very early (before kasan_early_init()) than arch-specific not-instrumented memmove()
>> isn't necessary to have.
>>
>> ---
>>  mm/kasan/common.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
>> index 6814d6d6a023..897f9520bab3 100644
>> --- a/mm/kasan/common.c
>> +++ b/mm/kasan/common.c
>> @@ -107,6 +107,7 @@ void *memset(void *addr, int c, size_t len)
>>  	return __memset(addr, c, len);
>>  }
>>  
>> +#ifdef __HAVE_ARCH_MEMMOVE
>>  #undef memmove
>>  void *memmove(void *dest, const void *src, size_t len)
>>  {
>> @@ -115,6 +116,7 @@ void *memmove(void *dest, const void *src, size_t len)
>>  
>>  	return __memmove(dest, src, len);
>>  }
>> +#endif
>>  
>>  #undef memcpy
>>  void *memcpy(void *dest, const void *src, size_t len)
>> -- 
>> 2.21.0
>>
>>
>>
> I have confirmed that the string operations are not used before kasan_early_init().
> But I can't make sure whether other ARCHs would need it before kasan_early_init().
> Do you have any idea to check that? Should I cc all other ARCH maintainers?
 

This doesn't affect other ARCHes in any way. If other arches have their own not-instrumented
memmove implementation (and they do), they will continue to be able to use it early.