Re: [PATCH v2 06/17] compat_ioctl: move rtc handling into rtc-dev.c

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 12/09/2018 17:08:53+0200, Arnd Bergmann wrote:
> We no longer need the rtc compat handling to be in common code, now that
> all drivers are either moved to the rtc-class framework, or (rarely)
> exist in drivers/char for architectures without compat mode (m68k,
> alpha and ia64, respectively).
> 
> I checked the list of ioctl commands in drivers, and the ones that are
> not already handled are all compatible, again with the one exception of
> m68k driver, which implements RTC_PLL_GET and RTC_PLL_SET, but has no
> compat mode.
> 
> Since the ioctl commands are either compatible or differ in both structure
> and command code between 32-bit and 64-bit, we can merge the compat
> handler into the native one and just implement the two common compat
> commands (RTC_IRQP_READ, RTC_IRQP_SET) there.
> 
> The old conversion handler also deals with RTC_EPOCH_READ and
> RTC_EPOCH_SET, which are not handled in rtc-dev.c but only in
> a single device driver (rtc-vr41xx), so I'm adding the compat
> version in the same place. I don't expect other drivers to need
> those commands in the future.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
> v2: merge compat handler into ioctl function to avoid the
>     compat_alloc_user_space() roundtrip, based on feedback
>     from Al Viro.
> ---
>  drivers/rtc/rtc-dev.c    | 13 +++++++++-
>  drivers/rtc/rtc-vr41xx.c | 10 ++++++++
>  fs/compat_ioctl.c        | 54 ----------------------------------------
>  3 files changed, 22 insertions(+), 55 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
> index 43d962a9c210..ccd5b1795e20 100644
> --- a/drivers/rtc/rtc-dev.c
> +++ b/drivers/rtc/rtc-dev.c
> @@ -13,6 +13,7 @@
>  
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
> +#include <linux/compat.h>
>  #include <linux/module.h>
>  #include <linux/rtc.h>
>  #include <linux/sched/signal.h>
> @@ -364,10 +365,19 @@ static long rtc_dev_ioctl(struct file *file,
>  		mutex_unlock(&rtc->ops_lock);
>  		return rtc_update_irq_enable(rtc, 0);
>  
> +#ifdef CONFIG_COMPAT
> +#define RTC_IRQP_SET32		_IOW('p', 0x0c, compat_ulong_t)
> +#define RTC_IRQP_READ32		_IOR('p', 0x0b, compat_ulong_t)
> +	case RTC_IRQP_SET32:
> +		err = rtc_irq_set_freq(rtc, arg);
> +		break;
> +	case RTC_IRQP_READ32:
> +		err = put_user(rtc->irq_freq, (unsigned int __user *)uarg);
> +		break;
> +#endif
>  	case RTC_IRQP_SET:
>  		err = rtc_irq_set_freq(rtc, arg);
>  		break;
> -
>  	case RTC_IRQP_READ:
>  		err = put_user(rtc->irq_freq, (unsigned long __user *)uarg);
>  		break;
> @@ -439,6 +449,7 @@ static const struct file_operations rtc_dev_fops = {
>  	.read		= rtc_dev_read,
>  	.poll		= rtc_dev_poll,
>  	.unlocked_ioctl	= rtc_dev_ioctl,
> +	.compat_ioctl	= generic_compat_ioctl_ptrarg,
>  	.open		= rtc_dev_open,
>  	.release	= rtc_dev_release,
>  	.fasync		= rtc_dev_fasync,
> diff --git a/drivers/rtc/rtc-vr41xx.c b/drivers/rtc/rtc-vr41xx.c
> index 70f013e692b0..1d90bde59d21 100644
> --- a/drivers/rtc/rtc-vr41xx.c
> +++ b/drivers/rtc/rtc-vr41xx.c
> @@ -17,6 +17,7 @@
>   *  along with this program; if not, write to the Free Software
>   *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
>   */
> +#include <linux/compat.h>
>  #include <linux/err.h>
>  #include <linux/fs.h>
>  #include <linux/init.h>
> @@ -79,6 +80,10 @@ static void __iomem *rtc2_base;
>  #define rtc2_read(offset)		readw(rtc2_base + (offset))
>  #define rtc2_write(offset, value)	writew((value), rtc2_base + (offset))
>  
> +/* 32-bit compat for ioctls that nobody else uses */
> +#define RTC_EPOCH_READ32	_IOR('p', 0x0d, compat_ulong_t)
> +#define RTC_EPOCH_SET32		_IOW('p', 0x0e, compat_ulong_t)
> +
>  static unsigned long epoch = 1970;	/* Jan 1 1970 00:00:00 */
>  
>  static DEFINE_SPINLOCK(rtc_lock);
> @@ -195,6 +200,11 @@ static int vr41xx_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long
>  	switch (cmd) {
>  	case RTC_EPOCH_READ:
>  		return put_user(epoch, (unsigned long __user *)arg);
> +#ifdef CONFIG_COMPAT
> +	case RTC_EPOCH_READ32:
> +		return put_user(epoch, (unsigned int __user *)arg);
> +	case RTC_EPOCH_SET32:
> +#endif
>  	case RTC_EPOCH_SET:
>  		/* Doesn't support before 1900 */
>  		if (arg < 1900)
> diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
> index 2d7c7e149083..312b52b4e974 100644
> --- a/fs/compat_ioctl.c
> +++ b/fs/compat_ioctl.c
> @@ -46,7 +46,6 @@
>  #include <linux/raw.h>
>  #include <linux/blkdev.h>
>  #include <linux/elevator.h>
> -#include <linux/rtc.h>
>  #include <linux/pci.h>
>  #include <linux/serial.h>
>  #include <linux/if_tun.h>
> @@ -633,37 +632,6 @@ static int serial_struct_ioctl(struct file *file,
>          return err;
>  }
>  
> -#define RTC_IRQP_READ32		_IOR('p', 0x0b, compat_ulong_t)
> -#define RTC_IRQP_SET32		_IOW('p', 0x0c, compat_ulong_t)
> -#define RTC_EPOCH_READ32	_IOR('p', 0x0d, compat_ulong_t)
> -#define RTC_EPOCH_SET32		_IOW('p', 0x0e, compat_ulong_t)
> -
> -static int rtc_ioctl(struct file *file,
> -		unsigned cmd, void __user *argp)
> -{
> -	unsigned long __user *valp = compat_alloc_user_space(sizeof(*valp));
> -	int ret;
> -
> -	if (valp == NULL)
> -		return -EFAULT;
> -	switch (cmd) {
> -	case RTC_IRQP_READ32:
> -	case RTC_EPOCH_READ32:
> -		ret = do_ioctl(file, (cmd == RTC_IRQP_READ32) ?
> -					RTC_IRQP_READ : RTC_EPOCH_READ,
> -					(unsigned long)valp);
> -		if (ret)
> -			return ret;
> -		return convert_in_user(valp, (unsigned int __user *)argp);
> -	case RTC_IRQP_SET32:
> -		return do_ioctl(file, RTC_IRQP_SET, (unsigned long)argp);
> -	case RTC_EPOCH_SET32:
> -		return do_ioctl(file, RTC_EPOCH_SET, (unsigned long)argp);
> -	}
> -
> -	return -ENOIOCTLCMD;
> -}
> -
>  /* on ia32 l_start is on a 32-bit boundary */
>  #if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
>  struct space_resv_32 {
> @@ -816,21 +784,6 @@ COMPATIBLE_IOCTL(SCSI_IOCTL_GET_PCI)
>  /* Big V (don't complain on serial console) */
>  IGNORE_IOCTL(VT_OPENQRY)
>  IGNORE_IOCTL(VT_GETMODE)
> -/* Little p (/dev/rtc, /dev/envctrl, etc.) */
> -COMPATIBLE_IOCTL(RTC_AIE_ON)
> -COMPATIBLE_IOCTL(RTC_AIE_OFF)
> -COMPATIBLE_IOCTL(RTC_UIE_ON)
> -COMPATIBLE_IOCTL(RTC_UIE_OFF)
> -COMPATIBLE_IOCTL(RTC_PIE_ON)
> -COMPATIBLE_IOCTL(RTC_PIE_OFF)
> -COMPATIBLE_IOCTL(RTC_WIE_ON)
> -COMPATIBLE_IOCTL(RTC_WIE_OFF)
> -COMPATIBLE_IOCTL(RTC_ALM_SET)
> -COMPATIBLE_IOCTL(RTC_ALM_READ)
> -COMPATIBLE_IOCTL(RTC_RD_TIME)
> -COMPATIBLE_IOCTL(RTC_SET_TIME)
> -COMPATIBLE_IOCTL(RTC_WKALM_SET)
> -COMPATIBLE_IOCTL(RTC_WKALM_RD)
>  /*
>   * These two are only for the sbus rtc driver, but
>   * hwclock tries them on every rtc device first when
> @@ -1307,13 +1260,6 @@ static long do_ioctl_trans(unsigned int cmd,
>  	case TIOCGSERIAL:
>  	case TIOCSSERIAL:
>  		return serial_struct_ioctl(file, cmd, argp);
> -	/* Not implemented in the native kernel */
> -	case RTC_IRQP_READ32:
> -	case RTC_IRQP_SET32:
> -	case RTC_EPOCH_READ32:
> -	case RTC_EPOCH_SET32:
> -		return rtc_ioctl(file, cmd, argp);
> -
>  	/* dvb */
>  	case VIDEO_GET_EVENT:
>  		return do_video_get_event(file, cmd, argp);
> -- 
> 2.18.0
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com