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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2021 Intel Corporation
* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
*
* iommufd provides control over the IOMMU HW objects created by IOMMU kernel
* drivers. IOMMU HW objects revolve around IO page tables that map incoming DMA
* addresses (IOVA) to CPU addresses.
*/
#define pr_fmt(fmt) "iommufd: " fmt
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/bug.h>
#include <uapi/linux/iommufd.h>
#include <linux/iommufd.h>
#include "iommufd_private.h"
struct iommufd_object_ops {
void (*destroy)(struct iommufd_object *obj);
};
static const struct iommufd_object_ops iommufd_object_ops[];
struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
size_t size,
enum iommufd_object_type type)
{
struct iommufd_object *obj;
int rc;
obj = kzalloc(size, GFP_KERNEL_ACCOUNT);
if (!obj)
return ERR_PTR(-ENOMEM);
obj->type = type;
init_rwsem(&obj->destroy_rwsem);
refcount_set(&obj->users, 1);
/*
* Reserve an ID in the xarray but do not publish the pointer yet since
* the caller hasn't initialized it yet. Once the pointer is published
* in the xarray and visible to other threads we can't reliably destroy
* it anymore, so the caller must complete all errorable operations
* before calling iommufd_object_finalize().
*/
rc = xa_alloc(&ictx->objects, &obj->id, XA_ZERO_ENTRY,
xa_limit_32b, GFP_KERNEL_ACCOUNT);
if (rc)
goto out_free;
return obj;
out_free:
kfree(obj);
return ERR_PTR(rc);
}
/*
* Allow concurrent access to the object.
*
* Once another thread can see the object pointer it can prevent object
* destruction. Expect for special kernel-only objects there is no in-kernel way
* to reliably destroy a single object. Thus all APIs that are creating objects
* must use iommufd_object_abort() to handle their errors and only call
* iommufd_object_finalize() once object creation cannot fail.
*/
void iommufd_object_finalize(struct iommufd_ctx *ictx,
struct iommufd_object *obj)
{
void *old;
old = xa_store(&ictx->objects, obj->id, obj, GFP_KERNEL);
/* obj->id was returned from xa_alloc() so the xa_store() cannot fail */
WARN_ON(old);
}
/* Undo _iommufd_object_alloc() if iommufd_object_finalize() was not called */
void iommufd_object_abort(struct iommufd_ctx *ictx, struct iommufd_object *obj)
{
void *old;
old = xa_erase(&ictx->objects, obj->id);
WARN_ON(old);
kfree(obj);
}
/*
* Abort an object that has been fully initialized and needs destroy, but has
* not been finalized.
*/
void iommufd_object_abort_and_destroy(struct iommufd_ctx *ictx,
struct iommufd_object *obj)
{
iommufd_object_ops[obj->type].destroy(obj);
iommufd_object_abort(ictx, obj);
}
struct iommufd_object *iommufd_get_object(struct iommufd_ctx *ictx, u32 id,
enum iommufd_object_type type)
{
struct iommufd_object *obj;
xa_lock(&ictx->objects);
obj = xa_load(&ictx->objects, id);
if (!obj || (type != IOMMUFD_OBJ_ANY && obj->type != type) ||
!iommufd_lock_obj(obj))
obj = ERR_PTR(-ENOENT);
xa_unlock(&ictx->objects);
return obj;
}
/*
* The caller holds a users refcount and wants to destroy the object. Returns
* true if the object was destroyed. In all cases the caller no longer has a
* reference on obj.
*/
bool iommufd_object_destroy_user(struct iommufd_ctx *ictx,
struct iommufd_object *obj)
{
/*
* The purpose of the destroy_rwsem is to ensure deterministic
* destruction of objects used by external drivers and destroyed by this
* function. Any temporary increment of the refcount must hold the read
* side of this, such as during ioctl execution.
*/
down_write(&obj->destroy_rwsem);
xa_lock(&ictx->objects);
refcount_dec(&obj->users);
if (!refcount_dec_if_one(&obj->users)) {
xa_unlock(&ictx->objects);
up_write(&obj->destroy_rwsem);
return false;
}
__xa_erase(&ictx->objects, obj->id);
xa_unlock(&ictx->objects);
up_write(&obj->destroy_rwsem);
iommufd_object_ops[obj->type].destroy(obj);
kfree(obj);
return true;
}
static int iommufd_destroy(struct iommufd_ucmd *ucmd)
{
struct iommu_destroy *cmd = ucmd->cmd;
struct iommufd_object *obj;
obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY);
if (IS_ERR(obj))
return PTR_ERR(obj);
iommufd_ref_to_users(obj);
/* See iommufd_ref_to_users() */
if (!iommufd_object_destroy_user(ucmd->ictx, obj))
return -EBUSY;
return 0;
}
static int iommufd_fops_open(struct inode *inode, struct file *filp)
{
struct iommufd_ctx *ictx;
ictx = kzalloc(sizeof(*ictx), GFP_KERNEL_ACCOUNT);
if (!ictx)
return -ENOMEM;
xa_init_flags(&ictx->objects, XA_FLAGS_ALLOC1 | XA_FLAGS_ACCOUNT);
ictx->file = filp;
filp->private_data = ictx;
return 0;
}
static int iommufd_fops_release(struct inode *inode, struct file *filp)
{
struct iommufd_ctx *ictx = filp->private_data;
struct iommufd_object *obj;
/*
* The objects in the xarray form a graph of "users" counts, and we have
* to destroy them in a depth first manner. Leaf objects will reduce the
* users count of interior objects when they are destroyed.
*
* Repeatedly destroying all the "1 users" leaf objects will progress
* until the entire list is destroyed. If this can't progress then there
* is some bug related to object refcounting.
*/
while (!xa_empty(&ictx->objects)) {
unsigned int destroyed = 0;
unsigned long index;
xa_for_each(&ictx->objects, index, obj) {
if (!refcount_dec_if_one(&obj->users))
continue;
destroyed++;
xa_erase(&ictx->objects, index);
iommufd_object_ops[obj->type].destroy(obj);
kfree(obj);
}
/* Bug related to users refcount */
if (WARN_ON(!destroyed))
break;
}
kfree(ictx);
return 0;
}
static int iommufd_option(struct iommufd_ucmd *ucmd)
{
struct iommu_option *cmd = ucmd->cmd;
int rc;
if (cmd->__reserved)
return -EOPNOTSUPP;
switch (cmd->option_id) {
case IOMMU_OPTION_RLIMIT_MODE:
rc = iommufd_option_rlimit_mode(cmd, ucmd->ictx);
break;
case IOMMU_OPTION_HUGE_PAGES:
rc = iommufd_ioas_option(ucmd);
break;
default:
return -EOPNOTSUPP;
}
if (rc)
return rc;
if (copy_to_user(&((struct iommu_option __user *)ucmd->ubuffer)->val64,
&cmd->val64, sizeof(cmd->val64)))
return -EFAULT;
return 0;
}
union ucmd_buffer {
struct iommu_destroy destroy;
struct iommu_ioas_alloc alloc;
struct iommu_ioas_allow_iovas allow_iovas;
struct iommu_ioas_iova_ranges iova_ranges;
struct iommu_ioas_map map;
struct iommu_ioas_unmap unmap;
};
struct iommufd_ioctl_op {
unsigned int size;
unsigned int min_size;
unsigned int ioctl_num;
int (*execute)(struct iommufd_ucmd *ucmd);
};
#define IOCTL_OP(_ioctl, _fn, _struct, _last) \
[_IOC_NR(_ioctl) - IOMMUFD_CMD_BASE] = { \
.size = sizeof(_struct) + \
BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) < \
sizeof(_struct)), \
.min_size = offsetofend(_struct, _last), \
.ioctl_num = _ioctl, \
.execute = _fn, \
}
static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id),
IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
struct iommu_ioas_alloc, out_ioas_id),
IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,
struct iommu_ioas_allow_iovas, allowed_iovas),
IOCTL_OP(IOMMU_IOAS_COPY, iommufd_ioas_copy, struct iommu_ioas_copy,
src_iova),
IOCTL_OP(IOMMU_IOAS_IOVA_RANGES, iommufd_ioas_iova_ranges,
struct iommu_ioas_iova_ranges, out_iova_alignment),
IOCTL_OP(IOMMU_IOAS_MAP, iommufd_ioas_map, struct iommu_ioas_map,
iova),
IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct iommu_ioas_unmap,
length),
IOCTL_OP(IOMMU_OPTION, iommufd_option, struct iommu_option,
val64),
};
static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
const struct iommufd_ioctl_op *op;
struct iommufd_ucmd ucmd = {};
union ucmd_buffer buf;
unsigned int nr;
int ret;
ucmd.ictx = filp->private_data;
ucmd.ubuffer = (void __user *)arg;
ret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);
if (ret)
return ret;
nr = _IOC_NR(cmd);
if (nr < IOMMUFD_CMD_BASE ||
(nr - IOMMUFD_CMD_BASE) >= ARRAY_SIZE(iommufd_ioctl_ops))
return -ENOIOCTLCMD;
op = &iommufd_ioctl_ops[nr - IOMMUFD_CMD_BASE];
if (op->ioctl_num != cmd)
return -ENOIOCTLCMD;
if (ucmd.user_size < op->min_size)
return -EINVAL;
ucmd.cmd = &buf;
ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer,
ucmd.user_size);
if (ret)
return ret;
ret = op->execute(&ucmd);
return ret;
}
static const struct file_operations iommufd_fops = {
.owner = THIS_MODULE,
.open = iommufd_fops_open,
.release = iommufd_fops_release,
.unlocked_ioctl = iommufd_fops_ioctl,
};
/**
* iommufd_ctx_get - Get a context reference
* @ictx: Context to get
*
* The caller must already hold a valid reference to ictx.
*/
void iommufd_ctx_get(struct iommufd_ctx *ictx)
{
get_file(ictx->file);
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_get, IOMMUFD);
/**
* iommufd_ctx_from_file - Acquires a reference to the iommufd context
* @file: File to obtain the reference from
*
* Returns a pointer to the iommufd_ctx, otherwise ERR_PTR. The struct file
* remains owned by the caller and the caller must still do fput. On success
* the caller is responsible to call iommufd_ctx_put().
*/
struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
{
struct iommufd_ctx *ictx;
if (file->f_op != &iommufd_fops)
return ERR_PTR(-EBADFD);
ictx = file->private_data;
iommufd_ctx_get(ictx);
return ictx;
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_file, IOMMUFD);
/**
* iommufd_ctx_put - Put back a reference
* @ictx: Context to put back
*/
void iommufd_ctx_put(struct iommufd_ctx *ictx)
{
fput(ictx->file);
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_put, IOMMUFD);
static const struct iommufd_object_ops iommufd_object_ops[] = {
[IOMMUFD_OBJ_ACCESS] = {
.destroy = iommufd_access_destroy_object,
},
[IOMMUFD_OBJ_DEVICE] = {
.destroy = iommufd_device_destroy,
},
[IOMMUFD_OBJ_IOAS] = {
.destroy = iommufd_ioas_destroy,
},
[IOMMUFD_OBJ_HW_PAGETABLE] = {
.destroy = iommufd_hw_pagetable_destroy,
},
};
static struct miscdevice iommu_misc_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "iommu",
.fops = &iommufd_fops,
.nodename = "iommu",
.mode = 0660,
};
static int __init iommufd_init(void)
{
int ret;
ret = misc_register(&iommu_misc_dev);
if (ret)
return ret;
return 0;
}
static void __exit iommufd_exit(void)
{
misc_deregister(&iommu_misc_dev);
}
module_init(iommufd_init);
module_exit(iommufd_exit);
MODULE_DESCRIPTION("I/O Address Space Management for passthrough devices");
MODULE_LICENSE("GPL");
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