Re: [PATCH] sh: uaccess: Require offsettable operands for 64-bit user access

[John Paul Adrian Glaubitz]

Hi Florian,

On Thu, 2026-07-16 at 18:53 +0200, Florian Fuchs wrote:
> The 64-bit __get_user_u64()/__put_user_u64() paths address the memory
> operand as %T2 (base+4). This base+4 requires an offsettable address,
> but "m" also allows the indexed mode @(R0,Rn) (e.g. for a variable-
> indexed array element), which has no displacement field for the +4.
> Depending on optimization this build fails with "invalid 'asm'" or an
> ICE in GCC's change_address_1.
> 
> Require an offsettable memory operand, allowing GCC to reload an
> unsuitable indexed address into an appropriate form.
> 
> Fixes: 2d2b308a8b7d ("sh: Implement __get_user_u64() required for 64-bit get_user()")
> Signed-off-by: Florian Fuchs <fuchsfl@xxxxxxxxx>
> ---
> The patch was verified on the J2 core on the Mimas v2 board. And booted
> on the Dreamcast SH4. checkpatch doesn't like the missing whitespaces
> around : I preferred not to touch the other unrelated lines, so I kept
> the local style.
> 
> The original GCC ICE, without this patch can be seen here:
> https://lore.kernel.org/linux-sh/ef22a5de-d945-4080-9f4a-f5a1ab9de1dc@xxxxxxxxxxx/
> 
>  arch/sh/include/asm/uaccess_32.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/sh/include/asm/uaccess_32.h b/arch/sh/include/asm/uaccess_32.h
> index 5d7ddc092afd..cef40414bfb1 100644
> --- a/arch/sh/include/asm/uaccess_32.h
> +++ b/arch/sh/include/asm/uaccess_32.h
> @@ -92,7 +92,7 @@ __asm__ __volatile__( \
>  	".long	1b + 2, 3b\n\t" \
>  	".previous" \
>  	:"=&r" (err), "=&r" (x) \
> -	:"m" (__m(addr)), "i" (-EFAULT), "0" (err)); })
> +	:"o" (__m(addr)), "i" (-EFAULT), "0" (err)); })
>  #else
>  #define __get_user_u64(x, addr, err) \
>  ({ \
> @@ -116,7 +116,7 @@ __asm__ __volatile__( \
>  	".long	1b + 2, 3b\n\t" \
>  	".previous" \
>  	:"=&r" (err), "=&r" (x) \
> -	:"m" (__m(addr)), "i" (-EFAULT), "0" (err)); })
> +	:"o" (__m(addr)), "i" (-EFAULT), "0" (err)); })
>  #endif
>  
>  #define __put_user_size(x,ptr,size,retval)		\
> @@ -196,7 +196,7 @@ __asm__ __volatile__( \
>  	".long	1b, 3b\n\t" \
>  	".previous" \
>  	: "=r" (retval) \
> -	: "r" (val), "m" (__m(addr)), "i" (-EFAULT), "0" (retval) \
> +	: "r" (val), "o" (__m(addr)), "i" (-EFAULT), "0" (retval) \
>          : "memory"); })
>  #else
>  #define __put_user_u64(val,addr,retval) \
> @@ -218,7 +218,7 @@ __asm__ __volatile__( \
>  	".long	1b, 3b\n\t" \
>  	".previous" \
>  	: "=r" (retval) \
> -	: "r" (val), "m" (__m(addr)), "i" (-EFAULT), "0" (retval) \
> +	: "r" (val), "o" (__m(addr)), "i" (-EFAULT), "0" (retval) \
>          : "memory"); })
>  #endif
>  

Nice catch, thanks a lot for fixing this!

Reviewed-by: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>

Adrian

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