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/* SPDX-License-Identifier: GPL-2.0-only */
/* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
*/
#ifndef __IOMMUFD_PRIVATE_H
#define __IOMMUFD_PRIVATE_H
#include <linux/rwsem.h>
#include <linux/xarray.h>
#include <linux/refcount.h>
#include <linux/uaccess.h>
struct iommufd_ctx {
struct file *file;
struct xarray objects;
};
struct iommufd_ucmd {
struct iommufd_ctx *ictx;
void __user *ubuffer;
u32 user_size;
void *cmd;
};
/* Copy the response in ucmd->cmd back to userspace. */
static inline int iommufd_ucmd_respond(struct iommufd_ucmd *ucmd,
size_t cmd_len)
{
if (copy_to_user(ucmd->ubuffer, ucmd->cmd,
min_t(size_t, ucmd->user_size, cmd_len)))
return -EFAULT;
return 0;
}
enum iommufd_object_type {
IOMMUFD_OBJ_NONE,
IOMMUFD_OBJ_ANY = IOMMUFD_OBJ_NONE,
};
/* Base struct for all objects with a userspace ID handle. */
struct iommufd_object {
struct rw_semaphore destroy_rwsem;
refcount_t users;
enum iommufd_object_type type;
unsigned int id;
};
static inline bool iommufd_lock_obj(struct iommufd_object *obj)
{
if (!down_read_trylock(&obj->destroy_rwsem))
return false;
if (!refcount_inc_not_zero(&obj->users)) {
up_read(&obj->destroy_rwsem);
return false;
}
return true;
}
struct iommufd_object *iommufd_get_object(struct iommufd_ctx *ictx, u32 id,
enum iommufd_object_type type);
static inline void iommufd_put_object(struct iommufd_object *obj)
{
refcount_dec(&obj->users);
up_read(&obj->destroy_rwsem);
}
/**
* iommufd_ref_to_users() - Switch from destroy_rwsem to users refcount
* protection
* @obj - Object to release
*
* Objects have two refcount protections (destroy_rwsem and the refcount_t
* users). Holding either of these will prevent the object from being destroyed.
*
* Depending on the use case, one protection or the other is appropriate. In
* most cases references are being protected by the destroy_rwsem. This allows
* orderly destruction of the object because iommufd_object_destroy_user() will
* wait for it to become unlocked. However, as a rwsem, it cannot be held across
* a system call return. So cases that have longer term needs must switch
* to the weaker users refcount_t.
*
* With users protection iommufd_object_destroy_user() will return false,
* refusing to destroy the object, causing -EBUSY to userspace.
*/
static inline void iommufd_ref_to_users(struct iommufd_object *obj)
{
up_read(&obj->destroy_rwsem);
/* iommufd_lock_obj() obtains users as well */
}
void iommufd_object_abort(struct iommufd_ctx *ictx, struct iommufd_object *obj);
void iommufd_object_abort_and_destroy(struct iommufd_ctx *ictx,
struct iommufd_object *obj);
void iommufd_object_finalize(struct iommufd_ctx *ictx,
struct iommufd_object *obj);
bool iommufd_object_destroy_user(struct iommufd_ctx *ictx,
struct iommufd_object *obj);
struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
size_t size,
enum iommufd_object_type type);
#define iommufd_object_alloc(ictx, ptr, type) \
container_of(_iommufd_object_alloc( \
ictx, \
sizeof(*(ptr)) + BUILD_BUG_ON_ZERO( \
offsetof(typeof(*(ptr)), \
obj) != 0), \
type), \
typeof(*(ptr)), obj)
#endif
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