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author | Jason Gunthorpe <jgg@nvidia.com> | 2022-11-29 16:29:29 -0400 |
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committer | Jason Gunthorpe <jgg@nvidia.com> | 2022-11-30 20:16:49 -0400 |
commit | 2ff4bed7fee72ba1abfcff5f11ae8f8e570353f2 (patch) | |
tree | e932c21eef44174131e88a1f8cc5ffc5175589fb /drivers/iommu/iommufd/iommufd_private.h | |
parent | 658234de0d2ed3a1b86d793f4772e38a2e039b35 (diff) | |
download | linux-stable-2ff4bed7fee72ba1abfcff5f11ae8f8e570353f2.tar.gz linux-stable-2ff4bed7fee72ba1abfcff5f11ae8f8e570353f2.tar.bz2 linux-stable-2ff4bed7fee72ba1abfcff5f11ae8f8e570353f2.zip |
iommufd: File descriptor, context, kconfig and makefiles
This is the basic infrastructure of a new miscdevice to hold the iommufd
IOCTL API.
It provides:
- A miscdevice to create file descriptors to run the IOCTL interface over
- A table based ioctl dispatch and centralized extendable pre-validation
step
- An xarray mapping userspace ID's to kernel objects. The design has
multiple inter-related objects held within in a single IOMMUFD fd
- A simple usage count to build a graph of object relations and protect
against hostile userspace racing ioctls
The only IOCTL provided in this patch is the generic 'destroy any object
by handle' operation.
Link: https://lore.kernel.org/r/6-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Lixiao Yang <lixiao.yang@intel.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Diffstat (limited to 'drivers/iommu/iommufd/iommufd_private.h')
-rw-r--r-- | drivers/iommu/iommufd/iommufd_private.h | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h new file mode 100644 index 000000000000..bb720bc11317 --- /dev/null +++ b/drivers/iommu/iommufd/iommufd_private.h @@ -0,0 +1,109 @@ +/* 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 |