Re: [PATCH v2] gpiolib: Switch to use compat_need_64bit_alignment_fixup() helper

[Kent Gibson <warthog618@xxxxxxxxx>]

On Thu, Oct 08, 2020 at 04:41:05PM +0300, Andy Shevchenko wrote:
> The new compat_need_64bit_alignment_fixup() helper allows to avoid
> ugly ifdeffery in IOCTL compatible code. Use it in GPIO cdev code.
> 

I'd re-arrange that checkin comment to

"Use the new compat_need_64bit_alignment_fixup() helper to avoid
ugly ifdeffery in IOCTL compatibility code."

but otherwise all good.

+1 on the deuglification, and it still works too.

Tested-by: Kent Gibson <warthog618@xxxxxxxxx>

> Depends-on: 527c412519eb ("compat: add a compat_need_64bit_alignment_fixup() helper")
> Depends-on: cc7886d25bca ("compat: lift compat_s64 and compat_u64 to <asm-generic/compat.h>")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
> v2: removed lineevent_get_size() completely, fixed typo in commit message
>  drivers/gpio/gpiolib-cdev.c | 24 ++++++++----------------
>  1 file changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index e9faeaf65d14..192721f829a3 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -1479,21 +1479,10 @@ static __poll_t lineevent_poll(struct file *file,
>  	return events;
>  }
>  
> -static ssize_t lineevent_get_size(void)
> -{
> -#if defined(CONFIG_X86_64) && !defined(CONFIG_UML)
> -	/* i386 has no padding after 'id' */
> -	if (in_ia32_syscall()) {
> -		struct compat_gpioeevent_data {
> -			compat_u64	timestamp;
> -			u32		id;
> -		};
> -
> -		return sizeof(struct compat_gpioeevent_data);
> -	}
> -#endif
> -	return sizeof(struct gpioevent_data);
> -}
> +struct compat_gpioeevent_data {
> +	compat_u64	timestamp;
> +	u32		id;
> +};
>  
>  static ssize_t lineevent_read(struct file *file,
>  			      char __user *buf,
> @@ -1515,7 +1504,10 @@ static ssize_t lineevent_read(struct file *file,
>  	 * actual sizeof() and pass this as an argument to copy_to_user() to
>  	 * drop unneeded bytes from the output.
>  	 */
> -	ge_size = lineevent_get_size();
> +	if (compat_need_64bit_alignment_fixup())
> +		ge_size = sizeof(struct compat_gpioeevent_data);
> +	else
> +		ge_size = sizeof(struct gpioevent_data);
>  	if (count < ge_size)
>  		return -EINVAL;
>  
> -- 
> 2.28.0
>