[PATCH] hpet: Support 32-bit userspace

[He Zhe]

hpet_compat_ioctl and read file operations failed to handle parameters from
32-bit userspace and thus samples/timers/hpet_example.c fails as below.

root@intel-x86-64:~# ./hpet_example-32.out poll /dev/hpet 1 2
-hpet: executing poll
hpet_poll: HPET_IRQFREQ failed

This patch fixes cmd and arg handling in hpet_compat_ioctl.
And adds compat handling for 32-bit userspace in hpet_read, based on the
method in commit 3418ff76119d
("[PATCH] RTC: rtc-dev tweak for 64-bit kernel").

hpet_example now shows that it works for both 64-bit and 32-bit.

root@intel-x86-64:~# ./hpet_example-32.out poll /dev/hpet 1 2
-hpet: executing poll
hpet_poll: info.hi_flags 0x0
hpet_poll: expired time = 0xf4298
hpet_poll: revents = 0x1
hpet_poll: data 0x1
hpet_poll: expired time = 0xf4235
hpet_poll: revents = 0x1
hpet_poll: data 0x1
root@intel-x86-64:~# ./hpet_example-64.out poll /dev/hpet 1 2
-hpet: executing poll
hpet_poll: info.hi_flags 0x0
hpet_poll: expired time = 0xf42a1
hpet_poll: revents = 0x1
hpet_poll: data 0x1
hpet_poll: expired time = 0xf4232
hpet_poll: revents = 0x1
hpet_poll: data 0x1

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: He Zhe <zhe.he@xxxxxxxxxxxxx>
---
 drivers/char/hpet.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index d51fc8321d41..025a5905a370 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -269,7 +269,8 @@ hpet_read(struct file *file, char __user *buf, size_t count, loff_t * ppos)
 	if (!devp->hd_ireqfreq)
 		return -EIO;
 
-	if (count < sizeof(unsigned long))
+	if ((sizeof(int) != sizeof(long) && count < sizeof(compat_ulong_t)) ||
+	    (sizeof(int) == sizeof(long) && count < sizeof(unsigned long)))
 		return -EINVAL;
 
 	add_wait_queue(&devp->hd_waitqueue, &wait);
@@ -294,9 +295,15 @@ hpet_read(struct file *file, char __user *buf, size_t count, loff_t * ppos)
 		schedule();
 	}
 
-	retval = put_user(data, (unsigned long __user *)buf);
-	if (!retval)
-		retval = sizeof(unsigned long);
+	if (sizeof(int) != sizeof(long) && count == sizeof(compat_ulong_t)) {
+		retval = put_user(data, (compat_ulong_t __user *)buf);
+		if (!retval)
+			retval = sizeof(compat_ulong_t);
+	} else {
+		retval = put_user(data, (unsigned long __user *)buf);
+		if (!retval)
+			retval = sizeof(unsigned long);
+	}
 out:
 	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(&devp->hd_waitqueue, &wait);
@@ -651,14 +658,23 @@ struct compat_hpet_info {
 	unsigned short hi_timer;
 };
 
+#define COMPAT_HPET_INFO       _IOR('h', 0x03, struct compat_hpet_info)
+#define COMPAT_HPET_IRQFREQ    _IOW('h', 0x6, compat_ulong_t)
+
 static long
 hpet_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct hpet_info info;
 	int err;
 
+	if (cmd == COMPAT_HPET_INFO)
+		cmd = HPET_INFO;
+
+	if (cmd == COMPAT_HPET_IRQFREQ)
+		cmd = HPET_IRQFREQ;
+
 	mutex_lock(&hpet_mutex);
-	err = hpet_ioctl_common(file->private_data, cmd, arg, &info);
+	err = hpet_ioctl_common(file->private_data, cmd, (unsigned long)compat_ptr(arg), &info);
 	mutex_unlock(&hpet_mutex);
 
 	if ((cmd == HPET_INFO) && !err) {
-- 
2.25.1