ptp: Properly handle compat ioctls

Pointer arguments passed to ioctls need to pass through compat_ptr() to
work correctly on s390; as explained in Documentation/driver-api/ioctl.rst.
Detect compat mode at runtime and call compat_ptr() for those commands
which do take pointer arguments.

Suggested-by: Arnd Bergmann <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]/
Fixes: d94ba80 ("ptp: Added a brand new class driver for ptp clocks.")
Signed-off-by: Thomas Weißschuh <[email protected]>
Reviewed-by: Cyrill Gorcunov <[email protected]>
Reviewed-by: Arnd Bergmann <[email protected]>
Acked-by: Richard Cochran <[email protected]>
Link: https://patch.msgid.link/20250125-posix-clock-compat_ioctl-v2-1-11c865c500eb@weissschuh.net
Signed-off-by: Paolo Abeni <[email protected]>

Author: t-8ch

drivers/ptp/ptp_chardev.c

@@ -4,6 +4,7 @@
  *
  * Copyright (C) 2010 OMICRON electronics GmbH
  */
+#include <linux/compat.h>
 #include <linux/module.h>
 #include <linux/posix-clock.h>
 #include <linux/poll.h>
@@ -176,6 +177,9 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
 	struct timespec64 ts;
 	int enable, err = 0;
 
+	if (in_compat_syscall() && cmd != PTP_ENABLE_PPS && cmd != PTP_ENABLE_PPS2)
+		arg = (unsigned long)compat_ptr(arg);
+
 	tsevq = pccontext->private_clkdata;
 
 	switch (cmd) {