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![David Herrmann](/assets/img/avatar_default.png)
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>
436 lines
14 KiB
C
436 lines
14 KiB
C
/*
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* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
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* Copyright (c) 2012 David Airlie <airlied@linux.ie>
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* Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <drm/drmP.h>
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#include <drm/drm_mm.h>
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#include <drm/drm_vma_manager.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/rbtree.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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/**
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* DOC: vma offset manager
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*
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* The vma-manager is responsible to map arbitrary driver-dependent memory
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* regions into the linear user address-space. It provides offsets to the
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* caller which can then be used on the address_space of the drm-device. It
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* takes care to not overlap regions, size them appropriately and to not
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* confuse mm-core by inconsistent fake vm_pgoff fields.
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* Drivers shouldn't use this for object placement in VMEM. This manager should
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* only be used to manage mappings into linear user-space VMs.
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*
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* We use drm_mm as backend to manage object allocations. But it is highly
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* optimized for alloc/free calls, not lookups. Hence, we use an rb-tree to
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* speed up offset lookups.
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*
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* You must not use multiple offset managers on a single address_space.
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* Otherwise, mm-core will be unable to tear down memory mappings as the VM will
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* no longer be linear. Please use VM_NONLINEAR in that case and implement your
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* own offset managers.
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*
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* This offset manager works on page-based addresses. That is, every argument
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* and return code (with the exception of drm_vma_node_offset_addr()) is given
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* in number of pages, not number of bytes. That means, object sizes and offsets
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* must always be page-aligned (as usual).
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* If you want to get a valid byte-based user-space address for a given offset,
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* please see drm_vma_node_offset_addr().
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*
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* Additionally to offset management, the vma offset manager also handles access
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* management. For every open-file context that is allowed to access a given
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* node, you must call drm_vma_node_allow(). Otherwise, an mmap() call on this
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* open-file with the offset of the node will fail with -EACCES. To revoke
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* access again, use drm_vma_node_revoke(). However, the caller is responsible
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* for destroying already existing mappings, if required.
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*/
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/**
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* drm_vma_offset_manager_init - Initialize new offset-manager
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* @mgr: Manager object
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* @page_offset: Offset of available memory area (page-based)
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* @size: Size of available address space range (page-based)
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*
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* Initialize a new offset-manager. The offset and area size available for the
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* manager are given as @page_offset and @size. Both are interpreted as
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* page-numbers, not bytes.
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*
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* Adding/removing nodes from the manager is locked internally and protected
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* against concurrent access. However, node allocation and destruction is left
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* for the caller. While calling into the vma-manager, a given node must
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* always be guaranteed to be referenced.
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*/
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void drm_vma_offset_manager_init(struct drm_vma_offset_manager *mgr,
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unsigned long page_offset, unsigned long size)
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{
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rwlock_init(&mgr->vm_lock);
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mgr->vm_addr_space_rb = RB_ROOT;
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drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size);
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}
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EXPORT_SYMBOL(drm_vma_offset_manager_init);
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/**
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* drm_vma_offset_manager_destroy() - Destroy offset manager
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* @mgr: Manager object
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*
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* Destroy an object manager which was previously created via
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* drm_vma_offset_manager_init(). The caller must remove all allocated nodes
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* before destroying the manager. Otherwise, drm_mm will refuse to free the
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* requested resources.
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*
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* The manager must not be accessed after this function is called.
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*/
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void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)
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{
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/* take the lock to protect against buggy drivers */
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write_lock(&mgr->vm_lock);
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drm_mm_takedown(&mgr->vm_addr_space_mm);
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write_unlock(&mgr->vm_lock);
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}
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EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
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/**
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* drm_vma_offset_lookup() - Find node in offset space
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* @mgr: Manager object
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* @start: Start address for object (page-based)
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* @pages: Size of object (page-based)
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*
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* Find a node given a start address and object size. This returns the _best_
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* match for the given node. That is, @start may point somewhere into a valid
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* region and the given node will be returned, as long as the node spans the
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* whole requested area (given the size in number of pages as @pages).
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*
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* RETURNS:
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* Returns NULL if no suitable node can be found. Otherwise, the best match
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* is returned. It's the caller's responsibility to make sure the node doesn't
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* get destroyed before the caller can access it.
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*/
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struct drm_vma_offset_node *drm_vma_offset_lookup(struct drm_vma_offset_manager *mgr,
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unsigned long start,
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unsigned long pages)
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{
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struct drm_vma_offset_node *node;
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read_lock(&mgr->vm_lock);
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node = drm_vma_offset_lookup_locked(mgr, start, pages);
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read_unlock(&mgr->vm_lock);
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return node;
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}
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EXPORT_SYMBOL(drm_vma_offset_lookup);
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/**
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* drm_vma_offset_lookup_locked() - Find node in offset space
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* @mgr: Manager object
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* @start: Start address for object (page-based)
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* @pages: Size of object (page-based)
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*
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* Same as drm_vma_offset_lookup() but requires the caller to lock offset lookup
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* manually. See drm_vma_offset_lock_lookup() for an example.
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*
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* RETURNS:
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* Returns NULL if no suitable node can be found. Otherwise, the best match
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* is returned.
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*/
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struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
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unsigned long start,
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unsigned long pages)
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{
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struct drm_vma_offset_node *node, *best;
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struct rb_node *iter;
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unsigned long offset;
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iter = mgr->vm_addr_space_rb.rb_node;
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best = NULL;
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while (likely(iter)) {
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node = rb_entry(iter, struct drm_vma_offset_node, vm_rb);
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offset = node->vm_node.start;
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if (start >= offset) {
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iter = iter->rb_right;
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best = node;
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if (start == offset)
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break;
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} else {
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iter = iter->rb_left;
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}
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}
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/* verify that the node spans the requested area */
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if (best) {
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offset = best->vm_node.start + best->vm_node.size;
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if (offset < start + pages)
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best = NULL;
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}
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return best;
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}
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EXPORT_SYMBOL(drm_vma_offset_lookup_locked);
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/* internal helper to link @node into the rb-tree */
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static void _drm_vma_offset_add_rb(struct drm_vma_offset_manager *mgr,
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struct drm_vma_offset_node *node)
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{
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struct rb_node **iter = &mgr->vm_addr_space_rb.rb_node;
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struct rb_node *parent = NULL;
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struct drm_vma_offset_node *iter_node;
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while (likely(*iter)) {
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parent = *iter;
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iter_node = rb_entry(*iter, struct drm_vma_offset_node, vm_rb);
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if (node->vm_node.start < iter_node->vm_node.start)
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iter = &(*iter)->rb_left;
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else if (node->vm_node.start > iter_node->vm_node.start)
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iter = &(*iter)->rb_right;
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else
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BUG();
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}
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rb_link_node(&node->vm_rb, parent, iter);
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rb_insert_color(&node->vm_rb, &mgr->vm_addr_space_rb);
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}
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/**
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* drm_vma_offset_add() - Add offset node to manager
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* @mgr: Manager object
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* @node: Node to be added
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* @pages: Allocation size visible to user-space (in number of pages)
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*
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* Add a node to the offset-manager. If the node was already added, this does
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* nothing and return 0. @pages is the size of the object given in number of
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* pages.
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* After this call succeeds, you can access the offset of the node until it
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* is removed again.
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*
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* If this call fails, it is safe to retry the operation or call
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* drm_vma_offset_remove(), anyway. However, no cleanup is required in that
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* case.
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*
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* @pages is not required to be the same size as the underlying memory object
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* that you want to map. It only limits the size that user-space can map into
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* their address space.
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*
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* RETURNS:
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* 0 on success, negative error code on failure.
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*/
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int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
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struct drm_vma_offset_node *node, unsigned long pages)
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{
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int ret;
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write_lock(&mgr->vm_lock);
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if (drm_mm_node_allocated(&node->vm_node)) {
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ret = 0;
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goto out_unlock;
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}
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ret = drm_mm_insert_node(&mgr->vm_addr_space_mm, &node->vm_node,
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pages, 0, DRM_MM_SEARCH_DEFAULT);
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if (ret)
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goto out_unlock;
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_drm_vma_offset_add_rb(mgr, node);
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out_unlock:
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write_unlock(&mgr->vm_lock);
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return ret;
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}
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EXPORT_SYMBOL(drm_vma_offset_add);
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/**
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* drm_vma_offset_remove() - Remove offset node from manager
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* @mgr: Manager object
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* @node: Node to be removed
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*
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* Remove a node from the offset manager. If the node wasn't added before, this
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* does nothing. After this call returns, the offset and size will be 0 until a
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* new offset is allocated via drm_vma_offset_add() again. Helper functions like
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* drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no
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* offset is allocated.
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*/
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void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
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struct drm_vma_offset_node *node)
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{
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write_lock(&mgr->vm_lock);
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if (drm_mm_node_allocated(&node->vm_node)) {
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rb_erase(&node->vm_rb, &mgr->vm_addr_space_rb);
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drm_mm_remove_node(&node->vm_node);
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memset(&node->vm_node, 0, sizeof(node->vm_node));
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}
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write_unlock(&mgr->vm_lock);
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}
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EXPORT_SYMBOL(drm_vma_offset_remove);
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/**
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* drm_vma_node_allow - Add open-file to list of allowed users
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* @node: Node to modify
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* @filp: Open file to add
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*
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* Add @filp to the list of allowed open-files for this node. If @filp is
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* already on this list, the ref-count is incremented.
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*
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* The list of allowed-users is preserved across drm_vma_offset_add() and
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* drm_vma_offset_remove() calls. You may even call it if the node is currently
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* not added to any offset-manager.
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*
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* You must remove all open-files the same number of times as you added them
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* before destroying the node. Otherwise, you will leak memory.
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*
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* This is locked against concurrent access internally.
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*
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* RETURNS:
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* 0 on success, negative error code on internal failure (out-of-mem)
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*/
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int drm_vma_node_allow(struct drm_vma_offset_node *node, struct file *filp)
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{
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struct rb_node **iter;
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struct rb_node *parent = NULL;
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struct drm_vma_offset_file *new, *entry;
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int ret = 0;
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/* Preallocate entry to avoid atomic allocations below. It is quite
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* unlikely that an open-file is added twice to a single node so we
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* don't optimize for this case. OOM is checked below only if the entry
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* is actually used. */
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new = kmalloc(sizeof(*entry), GFP_KERNEL);
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write_lock(&node->vm_lock);
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iter = &node->vm_files.rb_node;
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while (likely(*iter)) {
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parent = *iter;
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entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
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if (filp == entry->vm_filp) {
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entry->vm_count++;
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goto unlock;
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} else if (filp > entry->vm_filp) {
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iter = &(*iter)->rb_right;
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} else {
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iter = &(*iter)->rb_left;
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}
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}
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if (!new) {
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ret = -ENOMEM;
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goto unlock;
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}
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new->vm_filp = filp;
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new->vm_count = 1;
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rb_link_node(&new->vm_rb, parent, iter);
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rb_insert_color(&new->vm_rb, &node->vm_files);
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new = NULL;
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unlock:
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write_unlock(&node->vm_lock);
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kfree(new);
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return ret;
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}
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EXPORT_SYMBOL(drm_vma_node_allow);
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/**
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* drm_vma_node_revoke - Remove open-file from list of allowed users
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* @node: Node to modify
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* @filp: Open file to remove
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*
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* Decrement the ref-count of @filp in the list of allowed open-files on @node.
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* If the ref-count drops to zero, remove @filp from the list. You must call
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* this once for every drm_vma_node_allow() on @filp.
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*
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* This is locked against concurrent access internally.
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*
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* If @filp is not on the list, nothing is done.
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*/
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void drm_vma_node_revoke(struct drm_vma_offset_node *node, struct file *filp)
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{
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struct drm_vma_offset_file *entry;
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struct rb_node *iter;
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write_lock(&node->vm_lock);
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iter = node->vm_files.rb_node;
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while (likely(iter)) {
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entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
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if (filp == entry->vm_filp) {
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if (!--entry->vm_count) {
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rb_erase(&entry->vm_rb, &node->vm_files);
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kfree(entry);
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}
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break;
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} else if (filp > entry->vm_filp) {
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iter = iter->rb_right;
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} else {
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iter = iter->rb_left;
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}
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}
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write_unlock(&node->vm_lock);
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}
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EXPORT_SYMBOL(drm_vma_node_revoke);
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/**
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* drm_vma_node_is_allowed - Check whether an open-file is granted access
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* @node: Node to check
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* @filp: Open-file to check for
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*
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* Search the list in @node whether @filp is currently on the list of allowed
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* open-files (see drm_vma_node_allow()).
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*
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* This is locked against concurrent access internally.
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*
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* RETURNS:
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* true iff @filp is on the list
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*/
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bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
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struct file *filp)
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{
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struct drm_vma_offset_file *entry;
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struct rb_node *iter;
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read_lock(&node->vm_lock);
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iter = node->vm_files.rb_node;
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while (likely(iter)) {
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entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
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if (filp == entry->vm_filp)
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break;
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else if (filp > entry->vm_filp)
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iter = iter->rb_right;
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else
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iter = iter->rb_left;
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}
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read_unlock(&node->vm_lock);
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return iter;
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}
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EXPORT_SYMBOL(drm_vma_node_is_allowed);
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