linux-kernel - Re: [PATCH 7/8] riscv: implement __get_kernel_nofault and __put_user

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Date:   Tue, 08 Sep 2020 21:59:27 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Christoph Hellwig <hch@....de>
CC:     Paul Walmsley <paul.walmsley@...ive.com>,
        Arnd Bergmann <arnd@...db.de>, viro@...iv.linux.org.uk,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject:     Re: [PATCH 7/8] riscv: implement __get_kernel_nofault and __put_user_nofault

On Sun, 06 Sep 2020 22:58:24 PDT (-0700), Christoph Hellwig wrote:
> Implement the non-faulting kernel access helpers directly instead of
> abusing the uaccess routines under set_fs(KERNEL_DS).
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/riscv/include/asm/uaccess.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> index b67d1c616ec348..264e52fb62b143 100644
> --- a/arch/riscv/include/asm/uaccess.h
> +++ b/arch/riscv/include/asm/uaccess.h
> @@ -486,6 +486,26 @@ unsigned long __must_check clear_user(void __user *to, unsigned long n)
>  	__ret;							\
>  })
>
> +#define HAVE_GET_KERNEL_NOFAULT
> +
> +#define __get_kernel_nofault(dst, src, type, err_label)			\
> +do {									\
> +	long __kr_err;							\
> +									\
> +	__get_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err);	\
> +	if (unlikely(__kr_err))						\
> +		goto err_label;						\
> +} while (0)
> +
> +#define __put_kernel_nofault(dst, src, type, err_label)			\
> +do {									\
> +	long __kr_err;							\
> +									\
> +	__put_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err);	\
> +	if (unlikely(__kr_err))						\
> +		goto err_label;						\
> +} while (0)
> +
>  #else /* CONFIG_MMU */
>  #include <asm-generic/uaccess.h>
>  #endif /* CONFIG_MMU */

Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>