Hello Thomas.
-----Original Message----- From: Thomas Hellstrom [mailto:thomas@shipmail.org] Sent: Wednesday, August 31, 2011 5:39 PM To: Inki Dae Cc: airlied@linux.ie; dri-devel@lists.freedesktop.org; sw0312.kim@samsung.com; linux-kernel@vger.kernel.org; kyungmin.park@samsung.com; linux-arm-kernel@lists.infradead.org Subject: Re: [RFC][PATCH v3] DRM: add DRM Driver for Samsung SoC EXYNOS4210.
On 08/26/2011 01:47 PM, Inki Dae wrote:
This patch is a DRM Driver for Samsung SoC Exynos4210 and now enables
only FIMD yet
but we will add HDMI support also in the future.
this patch is based on git repository below: git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6.git, branch name: drm-next commit-id: bcc65fd8e929a9d9d34d814d6efc1d2793546922
you can refer to our working repository below: http://git.infradead.org/users/kmpark/linux-2.6-samsung branch name: samsung-drm
We tried to re-use lowlevel codes of the FIMD driver(s3c-fb.c based on Linux framebuffer) but couldn't so because lowlevel codes of s3c-fb.c are included internally and so FIMD module of this driver
has
its own lowlevel codes.
We used GEM framework for buffer management and DMA APIs(dma_alloc_*) for buffer allocation. by using DMA API, we could use CMA later.
Refer to this link for CMA(Continuous Memory Allocator): http://lkml.org/lkml/2011/7/20/45
this driver supports only physically continuous memory(non-iommu).
Links to previous versions of the patchset: v1:< https://lwn.net/Articles/454380/%3E v2:< http://www.spinics.net/lists/kernel/msg1224275.html%3E
Changelog v2: DRM: add DRM_IOCTL_SAMSUNG_GEM_MMAP ioctl command.
this feature maps user address space to physical memory region once user application requests DRM_IOCTL_SAMSUNG_GEM_MMAP ioctl.DRM: code clean and add exception codes.
Changelog v3: DRM: Support multiple irq.
FIMD and HDMI have their own irq handler but DRM Framework canregiter only one irq handler
this patch supports mutiple irq for Samsung SoC.DRM: Consider modularization.
each DRM, FIMD could be built as a module.DRM: Have indenpendent crtc object.
crtc isn't specific to SoC Platform so this patch gets a crtc to
be
used as common object.
created crtc could be attached to any encoder object.DRM: code clean and add exception codes.
S
...
+static struct drm_ioctl_desc samsung_ioctls[] = {
- DRM_IOCTL_DEF_DRV(SAMSUNG_GEM_CREATE, samsung_drm_gem_create_ioctl,
DRM_UNLOCKED),- DRM_IOCTL_DEF_DRV(SAMSUNG_GEM_MAP_OFFSET,
samsung_drm_gem_map_offset_ioctl, DRM_UNLOCKED),- DRM_IOCTL_DEF_DRV(SAMSUNG_GEM_MMAP,
samsung_drm_gem_mmap_ioctl, DRM_UNLOCKED),+};
What about security here? It looks to me like *any* user-space process can create a gem object and quickly exhaust available DMA memory space, potentially bringing the system down?
Likewise, there seems to be no owner check in the SAMSUNG_GEM_MMAP ioctl, allowing any user-space process unlimited graphics buffer access?
/Thomas
Right, we should consider security issue also as you mentioned above. thank you for your pointing out.