xref: /linux/drivers/xen/privcmd.c (revision 148f9bb87745ed45f7a11b2cbd3bc0f017d5d257) 
1 /******************************************************************************
2  * privcmd.c
3  *
4  * Interface to privileged domain-0 commands.
5  *
6  * Copyright (c) 2002-2004, K A Fraser, B Dragovic
7  */
8 
9 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
10 
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/slab.h>
15 #include <linux/string.h>
16 #include <linux/errno.h>
17 #include <linux/mm.h>
18 #include <linux/mman.h>
19 #include <linux/uaccess.h>
20 #include <linux/swap.h>
21 #include <linux/highmem.h>
22 #include <linux/pagemap.h>
23 #include <linux/seq_file.h>
24 #include <linux/miscdevice.h>
25 
26 #include <asm/pgalloc.h>
27 #include <asm/pgtable.h>
28 #include <asm/tlb.h>
29 #include <asm/xen/hypervisor.h>
30 #include <asm/xen/hypercall.h>
31 
32 #include <xen/xen.h>
33 #include <xen/privcmd.h>
34 #include <xen/interface/xen.h>
35 #include <xen/features.h>
36 #include <xen/page.h>
37 #include <xen/xen-ops.h>
38 #include <xen/balloon.h>
39 
40 #include "privcmd.h"
41 
42 MODULE_LICENSE("GPL");
43 
44 #define PRIV_VMA_LOCKED ((void *)1)
45 
46 #ifndef HAVE_ARCH_PRIVCMD_MMAP
47 static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma);
48 #endif
49 
50 static long privcmd_ioctl_hypercall(void __user *udata)
51 {
52 	struct privcmd_hypercall hypercall;
53 	long ret;
54 
55 	if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
56 		return -EFAULT;
57 
58 	ret = privcmd_call(hypercall.op,
59 			   hypercall.arg[0], hypercall.arg[1],
60 			   hypercall.arg[2], hypercall.arg[3],
61 			   hypercall.arg[4]);
62 
63 	return ret;
64 }
65 
66 static void free_page_list(struct list_head *pages)
67 {
68 	struct page *p, *n;
69 
70 	list_for_each_entry_safe(p, n, pages, lru)
71 		__free_page(p);
72 
73 	INIT_LIST_HEAD(pages);
74 }
75 
76 /*
77  * Given an array of items in userspace, return a list of pages
78  * containing the data.  If copying fails, either because of memory
79  * allocation failure or a problem reading user memory, return an
80  * error code; its up to the caller to dispose of any partial list.
81  */
82 static int gather_array(struct list_head *pagelist,
83 			unsigned nelem, size_t size,
84 			const void __user *data)
85 {
86 	unsigned pageidx;
87 	void *pagedata;
88 	int ret;
89 
90 	if (size > PAGE_SIZE)
91 		return 0;
92 
93 	pageidx = PAGE_SIZE;
94 	pagedata = NULL;	/* quiet, gcc */
95 	while (nelem--) {
96 		if (pageidx > PAGE_SIZE-size) {
97 			struct page *page = alloc_page(GFP_KERNEL);
98 
99 			ret = -ENOMEM;
100 			if (page == NULL)
101 				goto fail;
102 
103 			pagedata = page_address(page);
104 
105 			list_add_tail(&page->lru, pagelist);
106 			pageidx = 0;
107 		}
108 
109 		ret = -EFAULT;
110 		if (copy_from_user(pagedata + pageidx, data, size))
111 			goto fail;
112 
113 		data += size;
114 		pageidx += size;
115 	}
116 
117 	ret = 0;
118 
119 fail:
120 	return ret;
121 }
122 
123 /*
124  * Call function "fn" on each element of the array fragmented
125  * over a list of pages.
126  */
127 static int traverse_pages(unsigned nelem, size_t size,
128 			  struct list_head *pos,
129 			  int (*fn)(void *data, void *state),
130 			  void *state)
131 {
132 	void *pagedata;
133 	unsigned pageidx;
134 	int ret = 0;
135 
136 	BUG_ON(size > PAGE_SIZE);
137 
138 	pageidx = PAGE_SIZE;
139 	pagedata = NULL;	/* hush, gcc */
140 
141 	while (nelem--) {
142 		if (pageidx > PAGE_SIZE-size) {
143 			struct page *page;
144 			pos = pos->next;
145 			page = list_entry(pos, struct page, lru);
146 			pagedata = page_address(page);
147 			pageidx = 0;
148 		}
149 
150 		ret = (*fn)(pagedata + pageidx, state);
151 		if (ret)
152 			break;
153 		pageidx += size;
154 	}
155 
156 	return ret;
157 }
158 
159 struct mmap_mfn_state {
160 	unsigned long va;
161 	struct vm_area_struct *vma;
162 	domid_t domain;
163 };
164 
165 static int mmap_mfn_range(void *data, void *state)
166 {
167 	struct privcmd_mmap_entry *msg = data;
168 	struct mmap_mfn_state *st = state;
169 	struct vm_area_struct *vma = st->vma;
170 	int rc;
171 
172 	/* Do not allow range to wrap the address space. */
173 	if ((msg->npages > (LONG_MAX >> PAGE_SHIFT)) ||
174 	    ((unsigned long)(msg->npages << PAGE_SHIFT) >= -st->va))
175 		return -EINVAL;
176 
177 	/* Range chunks must be contiguous in va space. */
178 	if ((msg->va != st->va) ||
179 	    ((msg->va+(msg->npages<<PAGE_SHIFT)) > vma->vm_end))
180 		return -EINVAL;
181 
182 	rc = xen_remap_domain_mfn_range(vma,
183 					msg->va & PAGE_MASK,
184 					msg->mfn, msg->npages,
185 					vma->vm_page_prot,
186 					st->domain, NULL);
187 	if (rc < 0)
188 		return rc;
189 
190 	st->va += msg->npages << PAGE_SHIFT;
191 
192 	return 0;
193 }
194 
195 static long privcmd_ioctl_mmap(void __user *udata)
196 {
197 	struct privcmd_mmap mmapcmd;
198 	struct mm_struct *mm = current->mm;
199 	struct vm_area_struct *vma;
200 	int rc;
201 	LIST_HEAD(pagelist);
202 	struct mmap_mfn_state state;
203 
204 	/* We only support privcmd_ioctl_mmap_batch for auto translated. */
205 	if (xen_feature(XENFEAT_auto_translated_physmap))
206 		return -ENOSYS;
207 
208 	if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
209 		return -EFAULT;
210 
211 	rc = gather_array(&pagelist,
212 			  mmapcmd.num, sizeof(struct privcmd_mmap_entry),
213 			  mmapcmd.entry);
214 
215 	if (rc || list_empty(&pagelist))
216 		goto out;
217 
218 	down_write(&mm->mmap_sem);
219 
220 	{
221 		struct page *page = list_first_entry(&pagelist,
222 						     struct page, lru);
223 		struct privcmd_mmap_entry *msg = page_address(page);
224 
225 		vma = find_vma(mm, msg->va);
226 		rc = -EINVAL;
227 
228 		if (!vma || (msg->va != vma->vm_start) ||
229 		    !privcmd_enforce_singleshot_mapping(vma))
230 			goto out_up;
231 	}
232 
233 	state.va = vma->vm_start;
234 	state.vma = vma;
235 	state.domain = mmapcmd.dom;
236 
237 	rc = traverse_pages(mmapcmd.num, sizeof(struct privcmd_mmap_entry),
238 			    &pagelist,
239 			    mmap_mfn_range, &state);
240 
241 
242 out_up:
243 	up_write(&mm->mmap_sem);
244 
245 out:
246 	free_page_list(&pagelist);
247 
248 	return rc;
249 }
250 
251 struct mmap_batch_state {
252 	domid_t domain;
253 	unsigned long va;
254 	struct vm_area_struct *vma;
255 	int index;
256 	/* A tristate:
257 	 *      0 for no errors
258 	 *      1 if at least one error has happened (and no
259 	 *          -ENOENT errors have happened)
260 	 *      -ENOENT if at least 1 -ENOENT has happened.
261 	 */
262 	int global_error;
263 	int version;
264 
265 	/* User-space mfn array to store errors in the second pass for V1. */
266 	xen_pfn_t __user *user_mfn;
267 	/* User-space int array to store errors in the second pass for V2. */
268 	int __user *user_err;
269 };
270 
271 /* auto translated dom0 note: if domU being created is PV, then mfn is
272  * mfn(addr on bus). If it's auto xlated, then mfn is pfn (input to HAP).
273  */
274 static int mmap_batch_fn(void *data, void *state)
275 {
276 	xen_pfn_t *mfnp = data;
277 	struct mmap_batch_state *st = state;
278 	struct vm_area_struct *vma = st->vma;
279 	struct page **pages = vma->vm_private_data;
280 	struct page *cur_page = NULL;
281 	int ret;
282 
283 	if (xen_feature(XENFEAT_auto_translated_physmap))
284 		cur_page = pages[st->index++];
285 
286 	ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
287 					 st->vma->vm_page_prot, st->domain,
288 					 &cur_page);
289 
290 	/* Store error code for second pass. */
291 	if (st->version == 1) {
292 		if (ret < 0) {
293 			/*
294 			 * V1 encodes the error codes in the 32bit top nibble of the
295 			 * mfn (with its known limitations vis-a-vis 64 bit callers).
296 			 */
297 			*mfnp |= (ret == -ENOENT) ?
298 						PRIVCMD_MMAPBATCH_PAGED_ERROR :
299 						PRIVCMD_MMAPBATCH_MFN_ERROR;
300 		}
301 	} else { /* st->version == 2 */
302 		*((int *) mfnp) = ret;
303 	}
304 
305 	/* And see if it affects the global_error. */
306 	if (ret < 0) {
307 		if (ret == -ENOENT)
308 			st->global_error = -ENOENT;
309 		else {
310 			/* Record that at least one error has happened. */
311 			if (st->global_error == 0)
312 				st->global_error = 1;
313 		}
314 	}
315 	st->va += PAGE_SIZE;
316 
317 	return 0;
318 }
319 
320 static int mmap_return_errors(void *data, void *state)
321 {
322 	struct mmap_batch_state *st = state;
323 
324 	if (st->version == 1) {
325 		xen_pfn_t mfnp = *((xen_pfn_t *) data);
326 		if (mfnp & PRIVCMD_MMAPBATCH_MFN_ERROR)
327 			return __put_user(mfnp, st->user_mfn++);
328 		else
329 			st->user_mfn++;
330 	} else { /* st->version == 2 */
331 		int err = *((int *) data);
332 		if (err)
333 			return __put_user(err, st->user_err++);
334 		else
335 			st->user_err++;
336 	}
337 
338 	return 0;
339 }
340 
341 /* Allocate pfns that are then mapped with gmfns from foreign domid. Update
342  * the vma with the page info to use later.
343  * Returns: 0 if success, otherwise -errno
344  */
345 static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
346 {
347 	int rc;
348 	struct page **pages;
349 
350 	pages = kcalloc(numpgs, sizeof(pages[0]), GFP_KERNEL);
351 	if (pages == NULL)
352 		return -ENOMEM;
353 
354 	rc = alloc_xenballooned_pages(numpgs, pages, 0);
355 	if (rc != 0) {
356 		pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
357 			numpgs, rc);
358 		kfree(pages);
359 		return -ENOMEM;
360 	}
361 	BUG_ON(vma->vm_private_data != PRIV_VMA_LOCKED);
362 	vma->vm_private_data = pages;
363 
364 	return 0;
365 }
366 
367 static struct vm_operations_struct privcmd_vm_ops;
368 
369 static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
370 {
371 	int ret;
372 	struct privcmd_mmapbatch_v2 m;
373 	struct mm_struct *mm = current->mm;
374 	struct vm_area_struct *vma;
375 	unsigned long nr_pages;
376 	LIST_HEAD(pagelist);
377 	struct mmap_batch_state state;
378 
379 	switch (version) {
380 	case 1:
381 		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
382 			return -EFAULT;
383 		/* Returns per-frame error in m.arr. */
384 		m.err = NULL;
385 		if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
386 			return -EFAULT;
387 		break;
388 	case 2:
389 		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
390 			return -EFAULT;
391 		/* Returns per-frame error code in m.err. */
392 		if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
393 			return -EFAULT;
394 		break;
395 	default:
396 		return -EINVAL;
397 	}
398 
399 	nr_pages = m.num;
400 	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
401 		return -EINVAL;
402 
403 	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);
404 
405 	if (ret)
406 		goto out;
407 	if (list_empty(&pagelist)) {
408 		ret = -EINVAL;
409 		goto out;
410 	}
411 
412 	if (version == 2) {
413 		/* Zero error array now to only copy back actual errors. */
414 		if (clear_user(m.err, sizeof(int) * m.num)) {
415 			ret = -EFAULT;
416 			goto out;
417 		}
418 	}
419 
420 	down_write(&mm->mmap_sem);
421 
422 	vma = find_vma(mm, m.addr);
423 	if (!vma ||
424 	    vma->vm_ops != &privcmd_vm_ops ||
425 	    (m.addr != vma->vm_start) ||
426 	    ((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) ||
427 	    !privcmd_enforce_singleshot_mapping(vma)) {
428 		up_write(&mm->mmap_sem);
429 		ret = -EINVAL;
430 		goto out;
431 	}
432 	if (xen_feature(XENFEAT_auto_translated_physmap)) {
433 		ret = alloc_empty_pages(vma, m.num);
434 		if (ret < 0) {
435 			up_write(&mm->mmap_sem);
436 			goto out;
437 		}
438 	}
439 
440 	state.domain        = m.dom;
441 	state.vma           = vma;
442 	state.va            = m.addr;
443 	state.index         = 0;
444 	state.global_error  = 0;
445 	state.version       = version;
446 
447 	/* mmap_batch_fn guarantees ret == 0 */
448 	BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
449 			     &pagelist, mmap_batch_fn, &state));
450 
451 	up_write(&mm->mmap_sem);
452 
453 	if (state.global_error) {
454 		/* Write back errors in second pass. */
455 		state.user_mfn = (xen_pfn_t *)m.arr;
456 		state.user_err = m.err;
457 		ret = traverse_pages(m.num, sizeof(xen_pfn_t),
458 							 &pagelist, mmap_return_errors, &state);
459 	} else
460 		ret = 0;
461 
462 	/* If we have not had any EFAULT-like global errors then set the global
463 	 * error to -ENOENT if necessary. */
464 	if ((ret == 0) && (state.global_error == -ENOENT))
465 		ret = -ENOENT;
466 
467 out:
468 	free_page_list(&pagelist);
469 
470 	return ret;
471 }
472 
473 static long privcmd_ioctl(struct file *file,
474 			  unsigned int cmd, unsigned long data)
475 {
476 	int ret = -ENOSYS;
477 	void __user *udata = (void __user *) data;
478 
479 	switch (cmd) {
480 	case IOCTL_PRIVCMD_HYPERCALL:
481 		ret = privcmd_ioctl_hypercall(udata);
482 		break;
483 
484 	case IOCTL_PRIVCMD_MMAP:
485 		ret = privcmd_ioctl_mmap(udata);
486 		break;
487 
488 	case IOCTL_PRIVCMD_MMAPBATCH:
489 		ret = privcmd_ioctl_mmap_batch(udata, 1);
490 		break;
491 
492 	case IOCTL_PRIVCMD_MMAPBATCH_V2:
493 		ret = privcmd_ioctl_mmap_batch(udata, 2);
494 		break;
495 
496 	default:
497 		ret = -EINVAL;
498 		break;
499 	}
500 
501 	return ret;
502 }
503 
504 static void privcmd_close(struct vm_area_struct *vma)
505 {
506 	struct page **pages = vma->vm_private_data;
507 	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
508 
509 	if (!xen_feature(XENFEAT_auto_translated_physmap) || !numpgs || !pages)
510 		return;
511 
512 	xen_unmap_domain_mfn_range(vma, numpgs, pages);
513 	free_xenballooned_pages(numpgs, pages);
514 	kfree(pages);
515 }
516 
517 static int privcmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
518 {
519 	printk(KERN_DEBUG "privcmd_fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
520 	       vma, vma->vm_start, vma->vm_end,
521 	       vmf->pgoff, vmf->virtual_address);
522 
523 	return VM_FAULT_SIGBUS;
524 }
525 
526 static struct vm_operations_struct privcmd_vm_ops = {
527 	.close = privcmd_close,
528 	.fault = privcmd_fault
529 };
530 
531 static int privcmd_mmap(struct file *file, struct vm_area_struct *vma)
532 {
533 	/* DONTCOPY is essential for Xen because copy_page_range doesn't know
534 	 * how to recreate these mappings */
535 	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTCOPY |
536 			 VM_DONTEXPAND | VM_DONTDUMP;
537 	vma->vm_ops = &privcmd_vm_ops;
538 	vma->vm_private_data = NULL;
539 
540 	return 0;
541 }
542 
543 static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma)
544 {
545 	return !cmpxchg(&vma->vm_private_data, NULL, PRIV_VMA_LOCKED);
546 }
547 
548 const struct file_operations xen_privcmd_fops = {
549 	.owner = THIS_MODULE,
550 	.unlocked_ioctl = privcmd_ioctl,
551 	.mmap = privcmd_mmap,
552 };
553 EXPORT_SYMBOL_GPL(xen_privcmd_fops);
554 
555 static struct miscdevice privcmd_dev = {
556 	.minor = MISC_DYNAMIC_MINOR,
557 	.name = "xen/privcmd",
558 	.fops = &xen_privcmd_fops,
559 };
560 
561 static int __init privcmd_init(void)
562 {
563 	int err;
564 
565 	if (!xen_domain())
566 		return -ENODEV;
567 
568 	err = misc_register(&privcmd_dev);
569 	if (err != 0) {
570 		pr_err("Could not register Xen privcmd device\n");
571 		return err;
572 	}
573 	return 0;
574 }
575 
576 static void __exit privcmd_exit(void)
577 {
578 	misc_deregister(&privcmd_dev);
579 }
580 
581 module_init(privcmd_init);
582 module_exit(privcmd_exit);
583