linux-kernel - Re: [PATCH] drm: Only use DRM_IOCTL_UPDATE

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Date:	Thu, 19 Feb 2009 08:59:50 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Miller <davem@...emloft.net>
Cc:	airlied@...ux.ie, dri-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: Only use DRM_IOCTL_UPDATE_DRAW compat wrapper for
 compat X86.

On Wed, 2009-02-18 at 01:35 -0800, David Miller wrote:
> Ben, I'm pretty sure you're hitting this too on powerpc.  Every time a
> 32-bit process tries to upload cliprects it's going to fail with
> -EFAULT or similar.

Heh, quite possibly

Could that be related to the kernel spewing a bunch of

[drm:drm_update_drawable_info] *ERROR* Failed to copy cliprects from userspace

?

I've seen that yesterday on the Bimini, was planning to dig today until
I got stuck home with a cold...

> Nothing in userspace checks the return value for errors, etc. :-/

Surprise !

> The only reason I caught this is because I have a debugging check on
> sparc64 that makes sure that faults on kernel accesses to 32-bit
> userspace never have any of the high 32-bits set.

That's a nice trick, I might do something similar on power..

Cheers,
Ben.

> --------------------
> 
> drm: Only use DRM_IOCTL_UPDATE_DRAW compat wrapper for compat X86.
> 
> Only X86 32-bit uses a different alignment for "unsigned long long"
> than it's 64-bit counterpart.
> 
> Therefore this compat translation is only correct, and only needed,
> when either CONFIG_X86 or CONFIG_IA64.
> 
> Signed-off-by: David S. Miller <davem@...emloft.net>
> ---
>  drivers/gpu/drm/drm_ioc32.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c
> index 920b72f..282d9fd 100644
> --- a/drivers/gpu/drm/drm_ioc32.c
> +++ b/drivers/gpu/drm/drm_ioc32.c
> @@ -954,6 +954,7 @@ static int compat_drm_sg_free(struct file *file, unsigned int cmd,
>  			 DRM_IOCTL_SG_FREE, (unsigned long)request);
>  }
>  
> +#if defined(CONFIG_X86) || defined(CONFIG_IA64)
>  typedef struct drm_update_draw32 {
>  	drm_drawable_t handle;
>  	unsigned int type;
> @@ -984,6 +985,7 @@ static int compat_drm_update_draw(struct file *file, unsigned int cmd,
>  			DRM_IOCTL_UPDATE_DRAW, (unsigned long)request);
>  	return err;
>  }
> +#endif
>  
>  struct drm_wait_vblank_request32 {
>  	enum drm_vblank_seq_type type;
> @@ -1066,7 +1068,9 @@ drm_ioctl_compat_t *drm_compat_ioctls[] = {
>  #endif
>  	[DRM_IOCTL_NR(DRM_IOCTL_SG_ALLOC32)] = compat_drm_sg_alloc,
>  	[DRM_IOCTL_NR(DRM_IOCTL_SG_FREE32)] = compat_drm_sg_free,
> +#if defined(CONFIG_X86) || defined(CONFIG_IA64)
>  	[DRM_IOCTL_NR(DRM_IOCTL_UPDATE_DRAW32)] = compat_drm_update_draw,
> +#endif
>  	[DRM_IOCTL_NR(DRM_IOCTL_WAIT_VBLANK32)] = compat_drm_wait_vblank,
>  };
>  

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