compat_ioctl: move rtc handling into drivers/rtc/dev.c

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.

Unlike earlier versions of this patch, I'm now adding a separate
compat_ioctl handler that takes care of RTC_IRQP_READ32/RTC_IRQP_SET32
and treats all other commands as compatible, leaving the native
behavior unchanged.

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.

Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v4: handle RTC_EPOCH_SET32 in rtc_dev_compat_ioctl
v3: handle RTC_IRQP_READ32/RTC_IRQP_SET32 in rtc_dev_compat_ioctl
v2: merge compat handler into ioctl function to avoid the
    compat_alloc_user_space() roundtrip, based on feedback
    from Al Viro.

2 files changed, 40 insertions, 1 deletions

diff --git a/drivers/rtc/dev.c b/drivers/rtc/dev.c
index 84feb2565abd..5b8ebe86124a 100644
--- a/drivers/rtc/dev.c
+++ b/drivers/rtc/dev.c
@@ -10,6 +10,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/compat.h>
 #include <linux/module.h>
 #include <linux/rtc.h>
 #include <linux/sched/signal.h>
@@ -360,7 +361,6 @@ static long rtc_dev_ioctl(struct file *file,
 	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;
@@ -399,6 +399,34 @@ done:
 	return err;
 }
 
+#ifdef CONFIG_COMPAT
+#define RTC_IRQP_SET32		_IOW('p', 0x0c, __u32)
+#define RTC_IRQP_READ32		_IOR('p', 0x0b, __u32)
+#define RTC_EPOCH_SET32		_IOW('p', 0x0e, __u32)
+
+static long rtc_dev_compat_ioctl(struct file *file,
+				 unsigned int cmd, unsigned long arg)
+{
+	struct rtc_device *rtc = file->private_data;
+	void __user *uarg = compat_ptr(arg);
+
+	switch (cmd) {
+	case RTC_IRQP_READ32:
+		return put_user(rtc->irq_freq, (__u32 __user *)uarg);
+
+	case RTC_IRQP_SET32:
+		/* arg is a plain integer, not pointer */
+		return rtc_dev_ioctl(file, RTC_IRQP_SET, arg);
+
+	case RTC_EPOCH_SET32:
+		/* arg is a plain integer, not pointer */
+		return rtc_dev_ioctl(file, RTC_EPOCH_SET, arg);
+	}
+
+	return rtc_dev_ioctl(file, cmd, (unsigned long)uarg);
+}
+#endif
+
 static int rtc_dev_fasync(int fd, struct file *file, int on)
 {
 	struct rtc_device *rtc = file->private_data;
@@ -434,6 +462,9 @@ static const struct file_operations rtc_dev_fops = {
 	.read		= rtc_dev_read,
 	.poll		= rtc_dev_poll,
 	.unlocked_ioctl	= rtc_dev_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= rtc_dev_compat_ioctl,
+#endif
 	.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 c75230562c0d..c3671043ace7 100644
--- a/drivers/rtc/rtc-vr41xx.c
+++ b/drivers/rtc/rtc-vr41xx.c
@@ -4,6 +4,7 @@
  *
  *  Copyright (C) 2003-2008  Yoichi Yuasa <yuasa@linux-mips.org>
  */
+#include <linux/compat.h>
 #include <linux/err.h>
 #include <linux/fs.h>
 #include <linux/init.h>
@@ -66,6 +67,9 @@ 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, __u32)
+
 static unsigned long epoch = 1970;	/* Jan 1 1970 00:00:00 */
 
 static DEFINE_SPINLOCK(rtc_lock);
@@ -179,6 +183,10 @@ 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_64BIT
+	case RTC_EPOCH_READ32:
+		return put_user(epoch, (unsigned int __user *)arg);
+#endif
 	case RTC_EPOCH_SET:
 		/* Doesn't support before 1900 */
 		if (arg < 1900)