linux-kernel - Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in copy_mc_to

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Date:   Tue, 3 May 2022 09:06:18 +0800
From:   Tong Tiangen <tongtiangen@...wei.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Robin Murphy <robin.murphy@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Catalin Marinas" <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "Alexander Viro" <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
CC:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Xie XiuQi <xiexiuqi@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Guohanjun <guohanjun@...wei.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH -next v4 1/7] x86, powerpc: fix function define in
 copy_mc_to_user



在 2022/5/2 22:24, Christophe Leroy 写道:
> 
> 
> Le 20/04/2022 à 05:04, Tong Tiangen a écrit :
>> x86/powerpc has it's implementation of copy_mc_to_user but not use #define
>> to declare.
>>
>> This may cause problems, for example, if other architectures open
>> CONFIG_ARCH_HAS_COPY_MC, but want to use copy_mc_to_user() outside the
>> architecture, the code add to include/linux/uaddess.h is as follows:
>>
>>       #ifndef copy_mc_to_user
>>       static inline unsigned long __must_check
>>       copy_mc_to_user(void *dst, const void *src, size_t cnt)
>>       {
>> 	    ...
>>       }
>>       #endif
>>
>> Then this definition will conflict with the implementation of x86/powerpc
>> and cause compilation errors as follow:
>>
>> Fixes: ec6347bb4339 ("x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()")
> 
> I don't understand, what does it fix really ? What was the
> (existing/real) bug introduced by that patch and that your are fixing ?
> 
> If those defined had been expected and missing, we would have had a
> build failure. If you have one, can you describe it ?

There will be build failure after patch 3 is added, there is a little
confusing for a reader of this commit in isolation.
In the next version, I will put this patch after patch 3.

Thanks,
Tong.
> 
>> Signed-off-by: Tong Tiangen <tongtiangen@...wei.com>
>> ---
>>    arch/powerpc/include/asm/uaccess.h | 1 +
>>    arch/x86/include/asm/uaccess.h     | 1 +
>>    2 files changed, 2 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
>> index 9b82b38ff867..58dbe8e2e318 100644
>> --- a/arch/powerpc/include/asm/uaccess.h
>> +++ b/arch/powerpc/include/asm/uaccess.h
>> @@ -358,6 +358,7 @@ copy_mc_to_user(void __user *to, const void *from, unsigned long n)
>>    
>>    	return n;
>>    }
>> +#define copy_mc_to_user copy_mc_to_user
>>    #endif
>>    
>>    extern long __copy_from_user_flushcache(void *dst, const void __user *src,
>> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
>> index f78e2b3501a1..e18c5f098025 100644
>> --- a/arch/x86/include/asm/uaccess.h
>> +++ b/arch/x86/include/asm/uaccess.h
>> @@ -415,6 +415,7 @@ copy_mc_to_kernel(void *to, const void *from, unsigned len);
>>    
>>    unsigned long __must_check
>>    copy_mc_to_user(void *to, const void *from, unsigned len);
>> +#define copy_mc_to_user copy_mc_to_user
>>    #endif
>>    
>>    /*