Re: [PATCH 1/2] riscv: Add memmove string operation.

From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Nick Hu <nickhu@andestech.com>
Cc: "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
	"Alan Quey-Liang Kao(高魁良)" <alankao@andestech.com>,
	"atish.patra@wdc.com" <atish.patra@wdc.com>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"palmer@sifive.com" <palmer@sifive.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
	"離職Zong Zong-Xian Li(李宗憲)" <zong@andestech.com>,
	"alexios.zavras@intel.com" <alexios.zavras@intel.com>,
	"Anup.Patel@wdc.com" <Anup.Patel@wdc.com>,
	"glider@google.com" <glider@google.com>,
	"green.hu@gmail.com" <green.hu@gmail.com>,
	"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"deanbo422@gmail.com" <deanbo422@gmail.com>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"dvyukov@google.com" <dvyukov@google.com>
Subject: Re: [PATCH 1/2] riscv: Add memmove string operation.
Date: Tue, 27 Aug 2019 12:33:11 +0300	[thread overview]
Message-ID: <92dd5f5f-c8a2-53c3-4d61-44acc4366844@virtuozzo.com> (raw)
In-Reply-To: <20190827090738.GA22972@andestech.com>

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.

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