On Thu, Apr 25, 2019 at 12:21:53PM -0300, Mauro Carvalho Chehab wrote:
If I understand your patch description well, using compat_ptr_ioctl only works if the driver is not for s390, right?
No; s390 is where "oh, just set ->compat_ioctl same as ->unlocked_ioctl and be done with that; compat_ptr() is a no-op anyway" breaks. IOW, s390 is the reason for having compat_ptr_ioctl() in the first place; that thing works on all biarch architectures, as long as all stuff handled by ->ioctl() takes pointer to arch-independent object as argument. IOW, argument ignored => OK any arithmetical type => no go, compat_ptr() would bugger it pointer to int => OK pointer to string => OK pointer to u64 => OK pointer to struct {u64 addr; char s[11];} => OK pointer to long => needs explicit handler pointer to struct {void *addr; char s[11];} => needs explicit handler pointer to struct {int x; u64 y;} => needs explicit handler on amd64 For "just use ->unlocked_ioctl for ->ioctl" we have argument ignored => OK any arithmetical type => OK any pointer => instant breakage on s390, in addtion to cases that break with compat_ptr_ioctl().
Probably some form of that ought to go into commit message for compat_ptr_ioctl() introduction...