From 47a2b7dc03e35d4eaf8148b87aeea8dd96723b4d Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Tue, 22 Apr 2008 16:08:23 -0700 Subject: Initial add of mmfs module. --- linux-core/mmfs_drv.c | 299 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 299 insertions(+) create mode 100644 linux-core/mmfs_drv.c (limited to 'linux-core/mmfs_drv.c') diff --git a/linux-core/mmfs_drv.c b/linux-core/mmfs_drv.c new file mode 100644 index 00000000..f4b07117 --- /dev/null +++ b/linux-core/mmfs_drv.c @@ -0,0 +1,299 @@ +/* + * Copyright © 2008 Intel Corporation + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + * + * Authors: + * Eric Anholt + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include "mmfs.h" + +/** @file mmfs.c + * + * This file provides the filesystem for memory manager objects used by the + * DRM. + * + * The goal is to have swap-backed object allocation managed through + * struct file. However, file descriptors as handles to a struct file have + * two major failings: + * - Process limits prevent more than 1024 or so being used at a time by + * default. + * - Inability to allocate high fds will aggravate the X Server's select() + * handling, and likely that of many GL client applications as well. + * + * This led to a plan of using our own integer IDs (called handles, following + * DRM terminology) to mimic fds, and implement the fd syscalls we need as + * ioctls. The objects themselves will still include the struct file so + * that we can transition to fds if the required kernel infrastructure shows + * up at a later data, and as our interface with shmfs for memory allocation. + */ + +static struct mmfs_object * +mmfs_object_alloc(size_t size) +{ + struct mmfs_object *obj; + + BUG_ON((size & (PAGE_SIZE - 1)) != 0); + + obj = kcalloc(1, sizeof(*obj), GFP_KERNEL); + + obj->filp = shmem_file_setup("mmfs object", size, 0); + if (IS_ERR(obj->filp)) { + kfree(obj); + return NULL; + } + + obj->refcount = 1; + + return obj; +} + +/** + * Removes the mapping from handle to filp for this object. + */ +static int +mmfs_handle_delete(struct mmfs_file *mmfs_filp, int handle) +{ + struct mmfs_object *obj; + + /* This is gross. The idr system doesn't let us try a delete and + * return an error code. It just spews if you fail at deleting. + * So, we have to grab a lock around finding the object and then + * doing the delete on it and dropping the refcount, or the user + * could race us to double-decrement the refcount and cause a + * use-after-free later. Given the frequency of our handle lookups, + * we may want to use ida for number allocation and a hash table + * for the pointers, anyway. + */ + spin_lock(&mmfs_filp->delete_lock); + + /* Check if we currently have a reference on the object */ + obj = idr_find(&mmfs_filp->object_idr, handle); + if (obj == NULL) { + spin_unlock(&mmfs_filp->delete_lock); + return -EINVAL; + } + + /* Release reference and decrement refcount. */ + idr_remove(&mmfs_filp->object_idr, handle); + mmfs_object_unreference(obj); + + spin_unlock(&mmfs_filp->delete_lock); + + return 0; +} + +/** + * Allocates a new mmfs object and returns a handle to it. + */ +static int +mmfs_alloc_ioctl(struct inode *inode, struct file *filp, + unsigned int cmd, unsigned long arg) +{ + struct mmfs_file *mmfs_filp = filp->private_data; + struct mmfs_alloc_args args; + struct mmfs_object *obj; + int handle, ret; + + if (copy_from_user(&args, (void __user *)arg, sizeof(args))) + return -EFAULT; + + /* Round requested size up to page size */ + args.size = (args.size + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1); + + /* Allocate the new object */ + obj = mmfs_object_alloc(args.size); + if (obj == NULL) + return -ENOMEM; + + /* Get the user-visible handle using idr. + * + * I'm not really sure why the idr api needs us to do this in two + * repeating steps. It handles internal locking of its data + * structure, yet insists that we keep its memory allocation step + * separate from its slot-finding step for locking purposes. + */ + do { + if (idr_pre_get(&mmfs_filp->object_idr, GFP_KERNEL) == 0) { + kfree(obj); + return -EFAULT; + } + + ret = idr_get_new(&mmfs_filp->object_idr, obj, &handle); + } while (ret == -EAGAIN); + + if (ret != 0) { + mmfs_object_unreference(obj); + return -EFAULT; + } + + args.handle = handle; + + if (copy_to_user((void __user *)arg, &args, sizeof(args))) { + mmfs_handle_delete(mmfs_filp, args.handle); + return -EFAULT; + } + + return 0; +} + +/** + * Allocates a new mmfs object and returns a handle to it. + */ +static int +mmfs_unreference_ioctl(struct inode *inode, struct file *filp, + unsigned int cmd, unsigned long arg) +{ + struct mmfs_file *mmfs_filp = filp->private_data; + struct mmfs_unreference_args args; + int ret; + + if (copy_from_user(&args, (void __user *)arg, sizeof(args))) + return -EFAULT; + + ret = mmfs_handle_delete(mmfs_filp, args.handle); + + return ret; +} + +static int +mmfs_ioctl(struct inode *inode, struct file *filp, + unsigned int cmd, unsigned long arg) +{ + + switch (cmd) { + case MMFS_IOCTL_ALLOC: + return mmfs_alloc_ioctl(inode, filp, cmd, arg); + case MMFS_IOCTL_UNREFERENCE: + return mmfs_unreference_ioctl(inode, filp, cmd, arg); + default: + return -EINVAL; + } +} + +/** + * Sets up the file private for keeping track of our mappings of handles to + * mmfs objects. + */ +int +mmfs_open(struct inode *inode, struct file *filp) +{ + struct mmfs_file *mmfs_filp; + + if (filp->f_flags & O_EXCL) + return -EBUSY; /* No exclusive opens */ + + mmfs_filp = kcalloc(1, sizeof(*mmfs_filp), GFP_KERNEL); + if (mmfs_filp == NULL) + return -ENOMEM; + filp->private_data = mmfs_filp; + + idr_init(&mmfs_filp->object_idr); + + return 0; +} + +/** Called at device close to release the file's references on objects. */ +static int +mmfs_object_release(int id, void *ptr, void *data) +{ + struct mmfs_object *obj = ptr; + + mmfs_object_unreference(obj); + + return 0; +} + +/** + * Called at close time when the filp is going away. + * + * Releases any remaining references on objects by this filp. + */ +int +mmfs_close(struct inode *inode, struct file *filp) +{ + struct mmfs_file *mmfs_filp = filp->private_data; + + idr_for_each(&mmfs_filp->object_idr, &mmfs_object_release, NULL); + + idr_destroy(&mmfs_filp->object_idr); + + kfree(mmfs_filp); + filp->private_data = NULL; + + return 0; +} + +void +mmfs_object_reference(struct mmfs_object *obj) +{ + spin_lock(&obj->lock); + obj->refcount++; + spin_unlock(&obj->lock); +} + +void +mmfs_object_unreference(struct mmfs_object *obj) +{ + spin_lock(&obj->lock); + obj->refcount--; + spin_unlock(&obj->lock); + if (obj->refcount == 0) { + fput(obj->filp); + kfree(obj); + } +} + +/** File operations structure */ +static const struct file_operations mmfs_dev_fops = { + .owner = THIS_MODULE, + .open = mmfs_open, + .release = mmfs_close, + .ioctl = mmfs_ioctl, +}; + +static int __init mmfs_init(void) +{ + int ret; + + ret = register_chrdev(MMFS_DEVICE_MAJOR, "mmfs", &mmfs_dev_fops); + if (ret != 0) + return ret; + + return 0; +} + +static void __exit mmfs_exit(void) +{ + unregister_chrdev(MMFS_DEVICE_MAJOR, "mmfs"); +} + +module_init(mmfs_init); +module_exit(mmfs_exit); +MODULE_LICENSE("GPL and additional rights"); -- cgit v1.2.3