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Currently, userspace can fail to obtain the SAREA mapping (among other reasons) if it passes SAREA_MAX to drmAddMap without aligning it to the page size. This breaks for example on PowerPC with 64K pages and radeon despite the kernel radeon actually doing the right rouding in the first place. The way SAREA_MAX is defined with a bunch of ifdef's and duplicated between libdrm and the X server is gross, ultimately it should be retrieved by userspace from the kernel, but in the meantime, we have plenty of existing userspace built with bad values that need to work. This patch works around broken userspace by rounding the requested size in drm_addmap_core() of any SHM map to the page size. Since the backing memory for SHM maps is also allocated within addmap_core, there is no danger of adjacent memory being exposed due to the increased map size. The only side effect is that drivers that previously tried to create or access SHM maps using a size < PAGE_SIZE and failed (getting -EINVAL), will now succeed at the cost of a little bit more memory used if that happens to be when the map is created. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
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* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
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The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html