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

[Christophe Leroy <christophe.leroy@csgroup.eu>]

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 ?

> Signed-off-by: Tong Tiangen <tongtiangen@huawei.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
>   
>   /*