drivers/hv/hv_utils_transport.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Kernel/userspace transport abstraction for Hyper-V util driver.
0004  *
0005  * Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com>
0006  */
0007
0008 #include <linux/slab.h>
0009 #include <linux/fs.h>
0010 #include <linux/poll.h>
0011
0012 #include "hyperv_vmbus.h"
0013 #include "hv_utils_transport.h"
0014
0015 static DEFINE_SPINLOCK(hvt_list_lock);
0016 static LIST_HEAD(hvt_list);
0017
0018 static void hvt_reset(struct hvutil_transport *hvt)
0019 {
0020     kfree(hvt->outmsg);
0021     hvt->outmsg = NULL;
0022     hvt->outmsg_len = 0;
0023     if (hvt->on_reset)
0024         hvt->on_reset();
0025 }
0026
0027 static ssize_t hvt_op_read(struct file *file, char __user *buf,
0028                size_t count, loff_t *ppos)
0029 {
0030     struct hvutil_transport *hvt;
0031     int ret;
0032
0033     hvt = container_of(file->f_op, struct hvutil_transport, fops);
0034
0035     if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
0036                      hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
0037         return -EINTR;
0038
0039     mutex_lock(&hvt->lock);
0040
0041     if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
0042         ret = -EBADF;
0043         goto out_unlock;
0044     }
0045
0046     if (!hvt->outmsg) {
0047         ret = -EAGAIN;
0048         goto out_unlock;
0049     }
0050
0051     if (count < hvt->outmsg_len) {
0052         ret = -EINVAL;
0053         goto out_unlock;
0054     }
0055
0056     if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
0057         ret = hvt->outmsg_len;
0058     else
0059         ret = -EFAULT;
0060
0061     kfree(hvt->outmsg);
0062     hvt->outmsg = NULL;
0063     hvt->outmsg_len = 0;
0064
0065     if (hvt->on_read)
0066         hvt->on_read();
0067     hvt->on_read = NULL;
0068
0069 out_unlock:
0070     mutex_unlock(&hvt->lock);
0071     return ret;
0072 }
0073
0074 static ssize_t hvt_op_write(struct file *file, const char __user *buf,
0075                 size_t count, loff_t *ppos)
0076 {
0077     struct hvutil_transport *hvt;
0078     u8 *inmsg;
0079     int ret;
0080
0081     hvt = container_of(file->f_op, struct hvutil_transport, fops);
0082
0083     inmsg = memdup_user(buf, count);
0084     if (IS_ERR(inmsg))
0085         return PTR_ERR(inmsg);
0086
0087     if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
0088         ret = -EBADF;
0089     else
0090         ret = hvt->on_msg(inmsg, count);
0091
0092     kfree(inmsg);
0093
0094     return ret ? ret : count;
0095 }
0096
0097 static __poll_t hvt_op_poll(struct file *file, poll_table *wait)
0098 {
0099     struct hvutil_transport *hvt;
0100
0101     hvt = container_of(file->f_op, struct hvutil_transport, fops);
0102
0103     poll_wait(file, &hvt->outmsg_q, wait);
0104
0105     if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
0106         return EPOLLERR | EPOLLHUP;
0107
0108     if (hvt->outmsg_len > 0)
0109         return EPOLLIN | EPOLLRDNORM;
0110
0111     return 0;
0112 }
0113
0114 static int hvt_op_open(struct inode *inode, struct file *file)
0115 {
0116     struct hvutil_transport *hvt;
0117     int ret = 0;
0118     bool issue_reset = false;
0119
0120     hvt = container_of(file->f_op, struct hvutil_transport, fops);
0121
0122     mutex_lock(&hvt->lock);
0123
0124     if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
0125         ret = -EBADF;
0126     } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
0127         /*
0128          * Switching to CHARDEV mode. We switch bach to INIT when
0129          * device gets released.
0130          */
0131         hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
0132     }
0133     else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
0134         /*
0135          * We're switching from netlink communication to using char
0136          * device. Issue the reset first.
0137          */
0138         issue_reset = true;
0139         hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
0140     } else {
0141         ret = -EBUSY;
0142     }
0143
0144     if (issue_reset)
0145         hvt_reset(hvt);
0146
0147     mutex_unlock(&hvt->lock);
0148
0149     return ret;
0150 }
0151
0152 static void hvt_transport_free(struct hvutil_transport *hvt)
0153 {
0154     misc_deregister(&hvt->mdev);
0155     kfree(hvt->outmsg);
0156     kfree(hvt);
0157 }
0158
0159 static int hvt_op_release(struct inode *inode, struct file *file)
0160 {
0161     struct hvutil_transport *hvt;
0162     int mode_old;
0163
0164     hvt = container_of(file->f_op, struct hvutil_transport, fops);
0165
0166     mutex_lock(&hvt->lock);
0167     mode_old = hvt->mode;
0168     if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
0169         hvt->mode = HVUTIL_TRANSPORT_INIT;
0170     /*
0171      * Cleanup message buffers to avoid spurious messages when the daemon
0172      * connects back.
0173      */
0174     hvt_reset(hvt);
0175
0176     if (mode_old == HVUTIL_TRANSPORT_DESTROY)
0177         complete(&hvt->release);
0178
0179     mutex_unlock(&hvt->lock);
0180
0181     return 0;
0182 }
0183
0184 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
0185 {
0186     struct hvutil_transport *hvt, *hvt_found = NULL;
0187
0188     spin_lock(&hvt_list_lock);
0189     list_for_each_entry(hvt, &hvt_list, list) {
0190         if (hvt->cn_id.idx == msg->id.idx &&
0191             hvt->cn_id.val == msg->id.val) {
0192             hvt_found = hvt;
0193             break;
0194         }
0195     }
0196     spin_unlock(&hvt_list_lock);
0197     if (!hvt_found) {
0198         pr_warn("hvt_cn_callback: spurious message received!\n");
0199         return;
0200     }
0201
0202     /*
0203      * Switching to NETLINK mode. Switching to CHARDEV happens when someone
0204      * opens the device.
0205      */
0206     mutex_lock(&hvt->lock);
0207     if (hvt->mode == HVUTIL_TRANSPORT_INIT)
0208         hvt->mode = HVUTIL_TRANSPORT_NETLINK;
0209
0210     if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
0211         hvt_found->on_msg(msg->data, msg->len);
0212     else
0213         pr_warn("hvt_cn_callback: unexpected netlink message!\n");
0214     mutex_unlock(&hvt->lock);
0215 }
0216
0217 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len,
0218               void (*on_read_cb)(void))
0219 {
0220     struct cn_msg *cn_msg;
0221     int ret = 0;
0222
0223     if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
0224         hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
0225         return -EINVAL;
0226     } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
0227         cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
0228         if (!cn_msg)
0229             return -ENOMEM;
0230         cn_msg->id.idx = hvt->cn_id.idx;
0231         cn_msg->id.val = hvt->cn_id.val;
0232         cn_msg->len = len;
0233         memcpy(cn_msg->data, msg, len);
0234         ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
0235         kfree(cn_msg);
0236         /*
0237          * We don't know when netlink messages are delivered but unlike
0238          * in CHARDEV mode we're not blocked and we can send next
0239          * messages right away.
0240          */
0241         if (on_read_cb)
0242             on_read_cb();
0243         return ret;
0244     }
0245     /* HVUTIL_TRANSPORT_CHARDEV */
0246     mutex_lock(&hvt->lock);
0247     if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
0248         ret = -EINVAL;
0249         goto out_unlock;
0250     }
0251
0252     if (hvt->outmsg) {
0253         /* Previous message wasn't received */
0254         ret = -EFAULT;
0255         goto out_unlock;
0256     }
0257     hvt->outmsg = kzalloc(len, GFP_KERNEL);
0258     if (hvt->outmsg) {
0259         memcpy(hvt->outmsg, msg, len);
0260         hvt->outmsg_len = len;
0261         hvt->on_read = on_read_cb;
0262         wake_up_interruptible(&hvt->outmsg_q);
0263     } else
0264         ret = -ENOMEM;
0265 out_unlock:
0266     mutex_unlock(&hvt->lock);
0267     return ret;
0268 }
0269
0270 struct hvutil_transport *hvutil_transport_init(const char *name,
0271                            u32 cn_idx, u32 cn_val,
0272                            int (*on_msg)(void *, int),
0273                            void (*on_reset)(void))
0274 {
0275     struct hvutil_transport *hvt;
0276
0277     hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
0278     if (!hvt)
0279         return NULL;
0280
0281     hvt->cn_id.idx = cn_idx;
0282     hvt->cn_id.val = cn_val;
0283
0284     hvt->mdev.minor = MISC_DYNAMIC_MINOR;
0285     hvt->mdev.name = name;
0286
0287     hvt->fops.owner = THIS_MODULE;
0288     hvt->fops.read = hvt_op_read;
0289     hvt->fops.write = hvt_op_write;
0290     hvt->fops.poll = hvt_op_poll;
0291     hvt->fops.open = hvt_op_open;
0292     hvt->fops.release = hvt_op_release;
0293
0294     hvt->mdev.fops = &hvt->fops;
0295
0296     init_waitqueue_head(&hvt->outmsg_q);
0297     mutex_init(&hvt->lock);
0298     init_completion(&hvt->release);
0299
0300     spin_lock(&hvt_list_lock);
0301     list_add(&hvt->list, &hvt_list);
0302     spin_unlock(&hvt_list_lock);
0303
0304     hvt->on_msg = on_msg;
0305     hvt->on_reset = on_reset;
0306
0307     if (misc_register(&hvt->mdev))
0308         goto err_free_hvt;
0309
0310     /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
0311     if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
0312         cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
0313         goto err_free_hvt;
0314
0315     return hvt;
0316
0317 err_free_hvt:
0318     spin_lock(&hvt_list_lock);
0319     list_del(&hvt->list);
0320     spin_unlock(&hvt_list_lock);
0321     kfree(hvt);
0322     return NULL;
0323 }
0324
0325 void hvutil_transport_destroy(struct hvutil_transport *hvt)
0326 {
0327     int mode_old;
0328
0329     mutex_lock(&hvt->lock);
0330     mode_old = hvt->mode;
0331     hvt->mode = HVUTIL_TRANSPORT_DESTROY;
0332     wake_up_interruptible(&hvt->outmsg_q);
0333     mutex_unlock(&hvt->lock);
0334
0335     /*
0336      * In case we were in 'chardev' mode we still have an open fd so we
0337      * have to defer freeing the device. Netlink interface can be freed
0338      * now.
0339      */
0340     spin_lock(&hvt_list_lock);
0341     list_del(&hvt->list);
0342     spin_unlock(&hvt_list_lock);
0343     if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
0344         cn_del_callback(&hvt->cn_id);
0345
0346     if (mode_old == HVUTIL_TRANSPORT_CHARDEV)
0347         wait_for_completion(&hvt->release);
0348
0349     hvt_transport_free(hvt);
0350 }