135 lines
3.0 KiB
C
135 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/slab.h>
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <linux/fs.h>
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#include <linux/miscdevice.h>
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#include <linux/init.h>
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#include <linux/capability.h>
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#include <xen/xen.h>
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#include <xen/page.h>
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#include <xen/xenbus.h>
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#include <xen/xenbus_dev.h>
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#include <xen/grant_table.h>
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#include <xen/events.h>
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#include <asm/xen/hypervisor.h>
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#include "xenbus.h"
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static int xenbus_backend_open(struct inode *inode, struct file *filp)
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{
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return nonseekable_open(inode, filp);
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}
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static long xenbus_alloc(domid_t domid)
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{
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struct evtchn_alloc_unbound arg;
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int err = -EEXIST;
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xs_suspend();
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/* If xenstored_ready is nonzero, that means we have already talked to
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* xenstore and set up watches. These watches will be restored by
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* xs_resume, but that requires communication over the port established
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* below that is not visible to anyone until the ioctl returns.
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*
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* This can be resolved by splitting the ioctl into two parts
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* (postponing the resume until xenstored is active) but this is
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* unnecessarily complex for the intended use where xenstored is only
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* started once - so return -EEXIST if it's already running.
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*/
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if (xenstored_ready)
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goto out_err;
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gnttab_grant_foreign_access_ref(GNTTAB_RESERVED_XENSTORE, domid,
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virt_to_gfn(xen_store_interface), 0 /* writable */);
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arg.dom = DOMID_SELF;
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arg.remote_dom = domid;
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err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &arg);
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if (err)
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goto out_err;
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if (xen_store_evtchn > 0)
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xb_deinit_comms();
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xen_store_evtchn = arg.port;
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xs_resume();
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return arg.port;
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out_err:
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xs_suspend_cancel();
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return err;
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}
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static long xenbus_backend_ioctl(struct file *file, unsigned int cmd,
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unsigned long data)
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{
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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switch (cmd) {
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case IOCTL_XENBUS_BACKEND_EVTCHN:
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if (xen_store_evtchn > 0)
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return xen_store_evtchn;
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return -ENODEV;
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case IOCTL_XENBUS_BACKEND_SETUP:
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return xenbus_alloc(data);
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default:
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return -ENOTTY;
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}
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}
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static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
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{
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size_t size = vma->vm_end - vma->vm_start;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
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return -EINVAL;
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if (remap_pfn_range(vma, vma->vm_start,
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virt_to_pfn(xen_store_interface),
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size, vma->vm_page_prot))
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return -EAGAIN;
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return 0;
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}
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static const struct file_operations xenbus_backend_fops = {
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.open = xenbus_backend_open,
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.mmap = xenbus_backend_mmap,
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.unlocked_ioctl = xenbus_backend_ioctl,
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};
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static struct miscdevice xenbus_backend_dev = {
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.minor = MISC_DYNAMIC_MINOR,
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.name = "xen/xenbus_backend",
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.fops = &xenbus_backend_fops,
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};
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static int __init xenbus_backend_init(void)
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{
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int err;
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if (!xen_initial_domain())
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return -ENODEV;
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err = misc_register(&xenbus_backend_dev);
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if (err)
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pr_err("Could not register xenbus backend device\n");
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return err;
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}
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device_initcall(xenbus_backend_init);
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