Re: [PATCH v2 3/5] Revert "lib/string.c: implement a basic bcmp"

[Nathan Chancellor]

On Wed, Aug 19, 2020 at 12:16:52PM -0700, Nick Desaulniers wrote:
> This reverts commit 5f074f3e192f10c9fade898b9b3b8812e3d83342.
> 
> An earlier commit in the series prevents the compiler from emitting
> calls to bcmp as part of "libcall optimization," and there are no
> explicit callers, so we can now safely remove this interface.
> 
> Suggested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>

> ---
>  include/linux/string.h |  3 ---
>  lib/string.c           | 20 --------------------
>  2 files changed, 23 deletions(-)
> 
> diff --git a/include/linux/string.h b/include/linux/string.h
> index b1f3894a0a3e..f3bdb74bc230 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -155,9 +155,6 @@ extern void * memscan(void *,int,__kernel_size_t);
>  #ifndef __HAVE_ARCH_MEMCMP
>  extern int memcmp(const void *,const void *,__kernel_size_t);
>  #endif
> -#ifndef __HAVE_ARCH_BCMP
> -extern int bcmp(const void *,const void *,__kernel_size_t);
> -#endif
>  #ifndef __HAVE_ARCH_MEMCHR
>  extern void * memchr(const void *,int,__kernel_size_t);
>  #endif
> diff --git a/lib/string.c b/lib/string.c
> index 6012c385fb31..69328b8353e1 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -922,26 +922,6 @@ __visible int memcmp(const void *cs, const void *ct, size_t count)
>  EXPORT_SYMBOL(memcmp);
>  #endif
>  
> -#ifndef __HAVE_ARCH_BCMP
> -/**
> - * bcmp - returns 0 if and only if the buffers have identical contents.
> - * @a: pointer to first buffer.
> - * @b: pointer to second buffer.
> - * @len: size of buffers.
> - *
> - * The sign or magnitude of a non-zero return value has no particular
> - * meaning, and architectures may implement their own more efficient bcmp(). So
> - * while this particular implementation is a simple (tail) call to memcmp, do
> - * not rely on anything but whether the return value is zero or non-zero.
> - */
> -#undef bcmp
> -int bcmp(const void *a, const void *b, size_t len)
> -{
> -	return memcmp(a, b, len);
> -}
> -EXPORT_SYMBOL(bcmp);
> -#endif
> -
>  #ifndef __HAVE_ARCH_MEMSCAN
>  /**
>   * memscan - Find a character in an area of memory.
> -- 
> 2.28.0.297.g1956fa8f8d-goog
>