Re: [PATCH v2 05/17] compat_ioctl: move more drivers to generic_compat_ioctl_ptrarg

[Darren Hart]

On Fri, Sep 14, 2018 at 09:57:48PM +0100, Al Viro wrote:
> On Fri, Sep 14, 2018 at 01:35:06PM -0700, Darren Hart wrote:
>  
> > Acked-by: Darren Hart (VMware) 
> > 
> > As for a longer term solution, would it be possible to init fops in such
> > a way that the compat_ioctl call defaults to generic_compat_ioctl_ptrarg
> > so we don't have to duplicate this boilerplate for every ioctl fops
> > structure?
> 
>   Bad idea, that...  Because several years down the road somebody will add
> an ioctl that takes an unsigned int for argument.  Without so much as looking
> at your magical mystery macro being used to initialize file_operations.

Fair, being explicit in the declaration as it is currently may be
preferable then.

-- 
Darren Hart
VMware Open Source Technology Center
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Re: [PATCH v2 05/17] compat_ioctl: move more drivers to generic_compat_ioctl_ptrarg

[Darren Hart]

On Wed, Sep 12, 2018 at 05:08:52PM +0200, Arnd Bergmann wrote:
> The .ioctl and .compat_ioctl file operations have the same prototype so
> they can both point to the same function, which works great almost all
> the time when all the commands are compatible.
> 
> One exception is the s390 architecture, where a compat pointer is only
> 31 bit wide, and converting it into a 64-bit pointer requires calling
> compat_ptr(). Most drivers here will ever run in s390, but since we now
> have a generic helper for it, it's easy enough to use it consistently.
> 
> I double-checked all these drivers to ensure that all ioctl arguments
> are used as pointers or are ignored, but are not interpreted as integer
> values.
> 
> Signed-off-by: Arnd Bergmann 
> ---
...
>  drivers/platform/x86/wmi.c  | 2 +-
...
>  static void link_event_work(struct work_struct *work)
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 04791ea5d97b..e4d0697e07d6 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -886,7 +886,7 @@ static const struct file_operations wmi_fops = {
>   .read   = wmi_char_read,
>   .open   = wmi_char_open,
>   .unlocked_ioctl = wmi_ioctl,
> - .compat_ioctl   = wmi_ioctl,
> + .compat_ioctl   = generic_compat_ioctl_ptrarg,
>  };

For platform/drivers/x86:

Acked-by: Darren Hart (VMware) 

As for a longer term solution, would it be possible to init fops in such
a way that the compat_ioctl call defaults to generic_compat_ioctl_ptrarg
so we don't have to duplicate this boilerplate for every ioctl fops
structure?

-- 
Darren Hart
VMware Open Source Technology Center
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