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88d7ebe593
The VMA offset manager uses a device-global address-space. Hence, any user can currently map any offset-node they want. They only need to guess the right offset. If we wanted per open-file offset spaces, we'd either need VM_NONLINEAR mappings or multiple "struct address_space" trees. As both doesn't really scale, we implement access management in the VMA manager itself. We use an rb-tree to store open-files for each VMA node. On each mmap call, GEM, TTM or the drivers must check whether the current user is allowed to map this file. We add a separate lock for each node as there is no generic lock available for the caller to protect the node easily. As we currently don't know whether an object may be used for mmap(), we have to do access management for all objects. If it turns out to slow down handle creation/deletion significantly, we can optimize it in several ways: - Most times only a single filp is added per bo so we could use a static "struct file *main_filp" which is checked/added/removed first before we fall back to the rbtree+drm_vma_offset_file. This could be even done lockless with rcu. - Let user-space pass a hint whether mmap() should be supported on the bo and avoid access-management if not. - .. there are probably more ideas once we have benchmarks .. v2: add drm_vma_node_verify_access() helper Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: Dave Airlie <airlied@redhat.com> |
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