Re: is avoiding compat ioctls possible?

From: David Miller
Date: Thu Oct 29 2009 - 01:41:43 EST


From: Arnd Bergmann <arndbergmann@xxxxxxxxxxxxxx>
Date: Wed, 28 Oct 2009 16:40:18 +0100

> I'm pretty sure it was ok when we started adding the compat_ioctl
> handlers years ago. I think most people just ignored these for
> the majority of drivers that can't possibly run on s390. Even
> on s390, gcc will always do the right thing if you call call ioctl
> with a pointer to a normal object in the .data section, heap or stack,
> but hand-written assembly or other compilers may not.

Arnd, even compat_sys_ioctl() itself has constructs like:

case FS_IOC_RESVSP:
case FS_IOC_RESVSP64:
error = ioctl_preallocate(filp, (void __user *)arg);
goto out_fput;

That's why I asked about the 'arg' argument to sys_ioctl
on s390 :-)
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