[alsa-devel] [PATCH v3] ALSA: compress: add support for 32bit calls in a 64bit kernel

[Takashi Iwai]

On Mon, 07 Dec 2015 10:34:00 +0100,
Vinod Koul wrote:
> 
> On Mon, Dec 07, 2015 at 12:08:31PM +0530, Ravindra Lokhande wrote:
> > Compress offload does not support ioctl calls from a 32bit userspace
> > in a 64 bit kernel. This patch adds support for ioctls from a 32bit
> > userspace in a 64bit kernel
> > 
> > Signed-off-by: Ravindra Lokhande <rlokhande at nvidia.com>
> > ---
> > 
> > v1 -> v2: use compat_ptr to convert 32 bit address to 64 bit pointer
> > v2 -> v3: add header file compat.h
> > 
> >  sound/core/compress_offload.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> > index b123c42..4597820 100644
> > --- a/sound/core/compress_offload.c
> > +++ b/sound/core/compress_offload.c
> > @@ -38,6 +38,7 @@
> >  #include <linux/uio.h>
> >  #include <linux/uaccess.h>
> >  #include <linux/module.h>
> > +#include <linux/compat.h>
> >  #include <sound/core.h>
> >  #include <sound/initval.h>
> >  #include <sound/compress_params.h>
> > @@ -847,6 +848,15 @@ static long snd_compr_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
> >  	return retval;
> >  }
> >  
> > +/* support of 32bit userspace on 64bit platforms */
> > +#ifdef CONFIG_COMPAT
> > +static long snd_compr_ioctl_compat(struct file *file, unsigned int cmd,
> > +						unsigned long arg)
> > +{
> > +	return snd_compr_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
> > +}
> > +#endif
> > +
> >  static const struct file_operations snd_compr_file_ops = {
> >  		.owner =	THIS_MODULE,
> >  		.open =		snd_compr_open,
> > @@ -854,6 +864,9 @@ static const struct file_operations snd_compr_file_ops = {
> >  		.write =	snd_compr_write,
> >  		.read =		snd_compr_read,
> >  		.unlocked_ioctl = snd_compr_ioctl,
> > +#ifdef CONFIG_COMPAT
> > +		.compat_ioctl = snd_compr_ioctl_compat,
> > +#endif
> 
> While this change is okay and required, I can't help wondering why the core
> does not take care of this.

The core can't know whether it's 100% compatible.  So NULL means it's
not compatible.


Takashi

> When a driver does not support compat_ioctl as it was done recently and
> takes care of 32/64 bit issues we should call ioctl for that driver..
> 
> Neverthless, Acked-by Vinod Koul <vinod.koul at intel.com>
> 
> -- 
> ~Vinod
>