drivers/platform/surface/surface_aggregator_cdev.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Provides user-space access to the SSAM EC via the /dev/surface/aggregator
   4  * misc device. Intended for debugging and development.
   5  *
   6  * Copyright (C) 2020 Maximilian Luz <luzmaximilian@gmail.com>
   7  */
   8
   9 #include <linux/fs.h>
  10 #include <linux/kernel.h>
  11 #include <linux/kref.h>
  12 #include <linux/miscdevice.h>
  13 #include <linux/module.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/rwsem.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18
  19 #include <linux/surface_aggregator/cdev.h>
  20 #include <linux/surface_aggregator/controller.h>
  21
  22 #define SSAM_CDEV_DEVICE_NAME   "surface_aggregator_cdev"
  23
  24 struct ssam_cdev {
  25         struct kref kref;
  26         struct rw_semaphore lock;
  27         struct ssam_controller *ctrl;
  28         struct miscdevice mdev;
  29 };
  30
  31 static void __ssam_cdev_release(struct kref *kref)
  32 {
  33         kfree(container_of(kref, struct ssam_cdev, kref));
  34 }
  35
  36 static struct ssam_cdev *ssam_cdev_get(struct ssam_cdev *cdev)
  37 {
  38         if (cdev)
  39                 kref_get(&cdev->kref);
  40
  41         return cdev;
  42 }
  43
  44 static void ssam_cdev_put(struct ssam_cdev *cdev)
  45 {
  46         if (cdev)
  47                 kref_put(&cdev->kref, __ssam_cdev_release);
  48 }
  49
  50 static int ssam_cdev_device_open(struct inode *inode, struct file *filp)
  51 {
  52         struct miscdevice *mdev = filp->private_data;
  53         struct ssam_cdev *cdev = container_of(mdev, struct ssam_cdev, mdev);
  54
  55         filp->private_data = ssam_cdev_get(cdev);
  56         return stream_open(inode, filp);
  57 }
  58
  59 static int ssam_cdev_device_release(struct inode *inode, struct file *filp)
  60 {
  61         ssam_cdev_put(filp->private_data);
  62         return 0;
  63 }
  64
  65 static long ssam_cdev_request(struct ssam_cdev *cdev, unsigned long arg)
  66 {
  67         struct ssam_cdev_request __user *r;
  68         struct ssam_cdev_request rqst;
  69         struct ssam_request spec = {};
  70         struct ssam_response rsp = {};
  71         const void __user *plddata;
  72         void __user *rspdata;
  73         int status = 0, ret = 0, tmp;
  74
  75         r = (struct ssam_cdev_request __user *)arg;
  76         ret = copy_struct_from_user(&rqst, sizeof(rqst), r, sizeof(*r));
  77         if (ret)
  78                 goto out;
  79
  80         plddata = u64_to_user_ptr(rqst.payload.data);
  81         rspdata = u64_to_user_ptr(rqst.response.data);
  82
  83         /* Setup basic request fields. */
  84         spec.target_category = rqst.target_category;
  85         spec.target_id = rqst.target_id;
  86         spec.command_id = rqst.command_id;
  87         spec.instance_id = rqst.instance_id;
  88         spec.flags = 0;
  89         spec.length = rqst.payload.length;
  90         spec.payload = NULL;
  91
  92         if (rqst.flags & SSAM_CDEV_REQUEST_HAS_RESPONSE)
  93                 spec.flags |= SSAM_REQUEST_HAS_RESPONSE;
  94
  95         if (rqst.flags & SSAM_CDEV_REQUEST_UNSEQUENCED)
  96                 spec.flags |= SSAM_REQUEST_UNSEQUENCED;
  97
  98         rsp.capacity = rqst.response.length;
  99         rsp.length = 0;
 100         rsp.pointer = NULL;
 101
 102         /* Get request payload from user-space. */
 103         if (spec.length) {
 104                 if (!plddata) {
 105                         ret = -EINVAL;
 106                         goto out;
 107                 }
 108
 109                 /*
 110                  * Note: spec.length is limited to U16_MAX bytes via struct
 111                  * ssam_cdev_request. This is slightly larger than the
 112                  * theoretical maximum (SSH_COMMAND_MAX_PAYLOAD_SIZE) of the
 113                  * underlying protocol (note that nothing remotely this size
 114                  * should ever be allocated in any normal case). This size is
 115                  * validated later in ssam_request_sync(), for allocation the
 116                  * bound imposed by u16 should be enough.
 117                  */
 118                 spec.payload = kzalloc(spec.length, GFP_KERNEL);
 119                 if (!spec.payload) {
 120                         ret = -ENOMEM;
 121                         goto out;
 122                 }
 123
 124                 if (copy_from_user((void *)spec.payload, plddata, spec.length)) {
 125                         ret = -EFAULT;
 126                         goto out;
 127                 }
 128         }
 129
 130         /* Allocate response buffer. */
 131         if (rsp.capacity) {
 132                 if (!rspdata) {
 133                         ret = -EINVAL;
 134                         goto out;
 135                 }
 136
 137                 /*
 138                  * Note: rsp.capacity is limited to U16_MAX bytes via struct
 139                  * ssam_cdev_request. This is slightly larger than the
 140                  * theoretical maximum (SSH_COMMAND_MAX_PAYLOAD_SIZE) of the
 141                  * underlying protocol (note that nothing remotely this size
 142                  * should ever be allocated in any normal case). In later use,
 143                  * this capacity does not have to be strictly bounded, as it
 144                  * is only used as an output buffer to be written to. For
 145                  * allocation the bound imposed by u16 should be enough.
 146                  */
 147                 rsp.pointer = kzalloc(rsp.capacity, GFP_KERNEL);
 148                 if (!rsp.pointer) {
 149                         ret = -ENOMEM;
 150                         goto out;
 151                 }
 152         }
 153
 154         /* Perform request. */
 155         status = ssam_request_sync(cdev->ctrl, &spec, &rsp);
 156         if (status)
 157                 goto out;
 158
 159         /* Copy response to user-space. */
 160         if (rsp.length && copy_to_user(rspdata, rsp.pointer, rsp.length))
 161                 ret = -EFAULT;
 162
 163 out:
 164         /* Always try to set response-length and status. */
 165         tmp = put_user(rsp.length, &r->response.length);
 166         if (tmp)
 167                 ret = tmp;
 168
 169         tmp = put_user(status, &r->status);
 170         if (tmp)
 171                 ret = tmp;
 172
 173         /* Cleanup. */
 174         kfree(spec.payload);
 175         kfree(rsp.pointer);
 176
 177         return ret;
 178 }
 179
 180 static long __ssam_cdev_device_ioctl(struct ssam_cdev *cdev, unsigned int cmd,
 181                                      unsigned long arg)
 182 {
 183         switch (cmd) {
 184         case SSAM_CDEV_REQUEST:
 185                 return ssam_cdev_request(cdev, arg);
 186
 187         default:
 188                 return -ENOTTY;
 189         }
 190 }
 191
 192 static long ssam_cdev_device_ioctl(struct file *file, unsigned int cmd,
 193                                    unsigned long arg)
 194 {
 195         struct ssam_cdev *cdev = file->private_data;
 196         long status;
 197
 198         /* Ensure that controller is valid for as long as we need it. */
 199         if (down_read_killable(&cdev->lock))
 200                 return -ERESTARTSYS;
 201
 202         if (!cdev->ctrl) {
 203                 up_read(&cdev->lock);
 204                 return -ENODEV;
 205         }
 206
 207         status = __ssam_cdev_device_ioctl(cdev, cmd, arg);
 208
 209         up_read(&cdev->lock);
 210         return status;
 211 }
 212
 213 static const struct file_operations ssam_controller_fops = {
 214         .owner          = THIS_MODULE,
 215         .open           = ssam_cdev_device_open,
 216         .release        = ssam_cdev_device_release,
 217         .unlocked_ioctl = ssam_cdev_device_ioctl,
 218         .compat_ioctl   = ssam_cdev_device_ioctl,
 219         .llseek         = noop_llseek,
 220 };
 221
 222 static int ssam_dbg_device_probe(struct platform_device *pdev)
 223 {
 224         struct ssam_controller *ctrl;
 225         struct ssam_cdev *cdev;
 226         int status;
 227
 228         ctrl = ssam_client_bind(&pdev->dev);
 229         if (IS_ERR(ctrl))
 230                 return PTR_ERR(ctrl) == -ENODEV ? -EPROBE_DEFER : PTR_ERR(ctrl);
 231
 232         cdev = kzalloc(sizeof(*cdev), GFP_KERNEL);
 233         if (!cdev)
 234                 return -ENOMEM;
 235
 236         kref_init(&cdev->kref);
 237         init_rwsem(&cdev->lock);
 238         cdev->ctrl = ctrl;
 239
 240         cdev->mdev.parent   = &pdev->dev;
 241         cdev->mdev.minor    = MISC_DYNAMIC_MINOR;
 242         cdev->mdev.name     = "surface_aggregator";
 243         cdev->mdev.nodename = "surface/aggregator";
 244         cdev->mdev.fops     = &ssam_controller_fops;
 245
 246         status = misc_register(&cdev->mdev);
 247         if (status) {
 248                 kfree(cdev);
 249                 return status;
 250         }
 251
 252         platform_set_drvdata(pdev, cdev);
 253         return 0;
 254 }
 255
 256 static int ssam_dbg_device_remove(struct platform_device *pdev)
 257 {
 258         struct ssam_cdev *cdev = platform_get_drvdata(pdev);
 259
 260         misc_deregister(&cdev->mdev);
 261
 262         /*
 263          * The controller is only guaranteed to be valid for as long as the
 264          * driver is bound. Remove controller so that any lingering open files
 265          * cannot access it any more after we're gone.
 266          */
 267         down_write(&cdev->lock);
 268         cdev->ctrl = NULL;
 269         up_write(&cdev->lock);
 270
 271         ssam_cdev_put(cdev);
 272         return 0;
 273 }
 274
 275 static struct platform_device *ssam_cdev_device;
 276
 277 static struct platform_driver ssam_cdev_driver = {
 278         .probe = ssam_dbg_device_probe,
 279         .remove = ssam_dbg_device_remove,
 280         .driver = {
 281                 .name = SSAM_CDEV_DEVICE_NAME,
 282                 .probe_type = PROBE_PREFER_ASYNCHRONOUS,
 283         },
 284 };
 285
 286 static int __init ssam_debug_init(void)
 287 {
 288         int status;
 289
 290         ssam_cdev_device = platform_device_alloc(SSAM_CDEV_DEVICE_NAME,
 291                                                  PLATFORM_DEVID_NONE);
 292         if (!ssam_cdev_device)
 293                 return -ENOMEM;
 294
 295         status = platform_device_add(ssam_cdev_device);
 296         if (status)
 297                 goto err_device;
 298
 299         status = platform_driver_register(&ssam_cdev_driver);
 300         if (status)
 301                 goto err_driver;
 302
 303         return 0;
 304
 305 err_driver:
 306         platform_device_del(ssam_cdev_device);
 307 err_device:
 308         platform_device_put(ssam_cdev_device);
 309         return status;
 310 }
 311 module_init(ssam_debug_init);
 312
 313 static void __exit ssam_debug_exit(void)
 314 {
 315         platform_driver_unregister(&ssam_cdev_driver);
 316         platform_device_unregister(ssam_cdev_device);
 317 }
 318 module_exit(ssam_debug_exit);
 319
 320 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
 321 MODULE_DESCRIPTION("User-space interface for Surface System Aggregator Module");
 322 MODULE_LICENSE("GPL");