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134 lines
3.0 KiB
134 lines
3.0 KiB
// 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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