xref: /linux/drivers/xen/privcmd.c (revision 9e9f60108423f18a99c9cc93ef7f23490ecc709b) 
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 static int privcmd_vma_range_is_mapped(
47                struct vm_area_struct *vma,
48                unsigned long addr,
49                unsigned long nr_pages);
50 
51 static long privcmd_ioctl_hypercall(void __user *udata)
52 {
53 	struct privcmd_hypercall hypercall;
54 	long ret;
55 
56 	if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
57 		return -EFAULT;
58 
59 	ret = privcmd_call(hypercall.op,
60 			   hypercall.arg[0], hypercall.arg[1],
61 			   hypercall.arg[2], hypercall.arg[3],
62 			   hypercall.arg[4]);
63 
64 	return ret;
65 }
66 
67 static void free_page_list(struct list_head *pages)
68 {
69 	struct page *p, *n;
70 
71 	list_for_each_entry_safe(p, n, pages, lru)
72 		__free_page(p);
73 
74 	INIT_LIST_HEAD(pages);
75 }
76 
77 /*
78  * Given an array of items in userspace, return a list of pages
79  * containing the data.  If copying fails, either because of memory
80  * allocation failure or a problem reading user memory, return an
81  * error code; its up to the caller to dispose of any partial list.
82  */
83 static int gather_array(struct list_head *pagelist,
84 			unsigned nelem, size_t size,
85 			const void __user *data)
86 {
87 	unsigned pageidx;
88 	void *pagedata;
89 	int ret;
90 
91 	if (size > PAGE_SIZE)
92 		return 0;
93 
94 	pageidx = PAGE_SIZE;
95 	pagedata = NULL;	/* quiet, gcc */
96 	while (nelem--) {
97 		if (pageidx > PAGE_SIZE-size) {
98 			struct page *page = alloc_page(GFP_KERNEL);
99 
100 			ret = -ENOMEM;
101 			if (page == NULL)
102 				goto fail;
103 
104 			pagedata = page_address(page);
105 
106 			list_add_tail(&page->lru, pagelist);
107 			pageidx = 0;
108 		}
109 
110 		ret = -EFAULT;
111 		if (copy_from_user(pagedata + pageidx, data, size))
112 			goto fail;
113 
114 		data += size;
115 		pageidx += size;
116 	}
117 
118 	ret = 0;
119 
120 fail:
121 	return ret;
122 }
123 
124 /*
125  * Call function "fn" on each element of the array fragmented
126  * over a list of pages.
127  */
128 static int traverse_pages(unsigned nelem, size_t size,
129 			  struct list_head *pos,
130 			  int (*fn)(void *data, void *state),
131 			  void *state)
132 {
133 	void *pagedata;
134 	unsigned pageidx;
135 	int ret = 0;
136 
137 	BUG_ON(size > PAGE_SIZE);
138 
139 	pageidx = PAGE_SIZE;
140 	pagedata = NULL;	/* hush, gcc */
141 
142 	while (nelem--) {
143 		if (pageidx > PAGE_SIZE-size) {
144 			struct page *page;
145 			pos = pos->next;
146 			page = list_entry(pos, struct page, lru);
147 			pagedata = page_address(page);
148 			pageidx = 0;
149 		}
150 
151 		ret = (*fn)(pagedata + pageidx, state);
152 		if (ret)
153 			break;
154 		pageidx += size;
155 	}
156 
157 	return ret;
158 }
159 
160 struct mmap_mfn_state {
161 	unsigned long va;
162 	struct vm_area_struct *vma;
163 	domid_t domain;
164 };
165 
166 static int mmap_mfn_range(void *data, void *state)
167 {
168 	struct privcmd_mmap_entry *msg = data;
169 	struct mmap_mfn_state *st = state;
170 	struct vm_area_struct *vma = st->vma;
171 	int rc;
172 
173 	/* Do not allow range to wrap the address space. */
174 	if ((msg->npages > (LONG_MAX >> PAGE_SHIFT)) ||
175 	    ((unsigned long)(msg->npages << PAGE_SHIFT) >= -st->va))
176 		return -EINVAL;
177 
178 	/* Range chunks must be contiguous in va space. */
179 	if ((msg->va != st->va) ||
180 	    ((msg->va+(msg->npages<<PAGE_SHIFT)) > vma->vm_end))
181 		return -EINVAL;
182 
183 	rc = xen_remap_domain_mfn_range(vma,
184 					msg->va & PAGE_MASK,
185 					msg->mfn, msg->npages,
186 					vma->vm_page_prot,
187 					st->domain, NULL);
188 	if (rc < 0)
189 		return rc;
190 
191 	st->va += msg->npages << PAGE_SHIFT;
192 
193 	return 0;
194 }
195 
196 static long privcmd_ioctl_mmap(void __user *udata)
197 {
198 	struct privcmd_mmap mmapcmd;
199 	struct mm_struct *mm = current->mm;
200 	struct vm_area_struct *vma;
201 	int rc;
202 	LIST_HEAD(pagelist);
203 	struct mmap_mfn_state state;
204 
205 	/* We only support privcmd_ioctl_mmap_batch for auto translated. */
206 	if (xen_feature(XENFEAT_auto_translated_physmap))
207 		return -ENOSYS;
208 
209 	if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
210 		return -EFAULT;
211 
212 	rc = gather_array(&pagelist,
213 			  mmapcmd.num, sizeof(struct privcmd_mmap_entry),
214 			  mmapcmd.entry);
215 
216 	if (rc || list_empty(&pagelist))
217 		goto out;
218 
219 	down_write(&mm->mmap_sem);
220 
221 	{
222 		struct page *page = list_first_entry(&pagelist,
223 						     struct page, lru);
224 		struct privcmd_mmap_entry *msg = page_address(page);
225 
226 		vma = find_vma(mm, msg->va);
227 		rc = -EINVAL;
228 
229 		if (!vma || (msg->va != vma->vm_start) || vma->vm_private_data)
230 			goto out_up;
231 		vma->vm_private_data = PRIV_VMA_LOCKED;
232 	}
233 
234 	state.va = vma->vm_start;
235 	state.vma = vma;
236 	state.domain = mmapcmd.dom;
237 
238 	rc = traverse_pages(mmapcmd.num, sizeof(struct privcmd_mmap_entry),
239 			    &pagelist,
240 			    mmap_mfn_range, &state);
241 
242 
243 out_up:
244 	up_write(&mm->mmap_sem);
245 
246 out:
247 	free_page_list(&pagelist);
248 
249 	return rc;
250 }
251 
252 struct mmap_batch_state {
253 	domid_t domain;
254 	unsigned long va;
255 	struct vm_area_struct *vma;
256 	int index;
257 	/* A tristate:
258 	 *      0 for no errors
259 	 *      1 if at least one error has happened (and no
260 	 *          -ENOENT errors have happened)
261 	 *      -ENOENT if at least 1 -ENOENT has happened.
262 	 */
263 	int global_error;
264 	int version;
265 
266 	/* User-space mfn array to store errors in the second pass for V1. */
267 	xen_pfn_t __user *user_mfn;
268 	/* User-space int array to store errors in the second pass for V2. */
269 	int __user *user_err;
270 };
271 
272 /* auto translated dom0 note: if domU being created is PV, then mfn is
273  * mfn(addr on bus). If it's auto xlated, then mfn is pfn (input to HAP).
274  */
275 static int mmap_batch_fn(void *data, void *state)
276 {
277 	xen_pfn_t *mfnp = data;
278 	struct mmap_batch_state *st = state;
279 	struct vm_area_struct *vma = st->vma;
280 	struct page **pages = vma->vm_private_data;
281 	struct page *cur_page = NULL;
282 	int ret;
283 
284 	if (xen_feature(XENFEAT_auto_translated_physmap))
285 		cur_page = pages[st->index++];
286 
287 	ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
288 					 st->vma->vm_page_prot, st->domain,
289 					 &cur_page);
290 
291 	/* Store error code for second pass. */
292 	if (st->version == 1) {
293 		if (ret < 0) {
294 			/*
295 			 * V1 encodes the error codes in the 32bit top nibble of the
296 			 * mfn (with its known limitations vis-a-vis 64 bit callers).
297 			 */
298 			*mfnp |= (ret == -ENOENT) ?
299 						PRIVCMD_MMAPBATCH_PAGED_ERROR :
300 						PRIVCMD_MMAPBATCH_MFN_ERROR;
301 		}
302 	} else { /* st->version == 2 */
303 		*((int *) mfnp) = ret;
304 	}
305 
306 	/* And see if it affects the global_error. */
307 	if (ret < 0) {
308 		if (ret == -ENOENT)
309 			st->global_error = -ENOENT;
310 		else {
311 			/* Record that at least one error has happened. */
312 			if (st->global_error == 0)
313 				st->global_error = 1;
314 		}
315 	}
316 	st->va += PAGE_SIZE;
317 
318 	return 0;
319 }
320 
321 static int mmap_return_errors(void *data, void *state)
322 {
323 	struct mmap_batch_state *st = state;
324 
325 	if (st->version == 1) {
326 		xen_pfn_t mfnp = *((xen_pfn_t *) data);
327 		if (mfnp & PRIVCMD_MMAPBATCH_MFN_ERROR)
328 			return __put_user(mfnp, st->user_mfn++);
329 		else
330 			st->user_mfn++;
331 	} else { /* st->version == 2 */
332 		int err = *((int *) data);
333 		if (err)
334 			return __put_user(err, st->user_err++);
335 		else
336 			st->user_err++;
337 	}
338 
339 	return 0;
340 }
341 
342 /* Allocate pfns that are then mapped with gmfns from foreign domid. Update
343  * the vma with the page info to use later.
344  * Returns: 0 if success, otherwise -errno
345  */
346 static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
347 {
348 	int rc;
349 	struct page **pages;
350 
351 	pages = kcalloc(numpgs, sizeof(pages[0]), GFP_KERNEL);
352 	if (pages == NULL)
353 		return -ENOMEM;
354 
355 	rc = alloc_xenballooned_pages(numpgs, pages, 0);
356 	if (rc != 0) {
357 		pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
358 			numpgs, rc);
359 		kfree(pages);
360 		return -ENOMEM;
361 	}
362 	BUG_ON(vma->vm_private_data != NULL);
363 	vma->vm_private_data = pages;
364 
365 	return 0;
366 }
367 
368 static struct vm_operations_struct privcmd_vm_ops;
369 
370 static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
371 {
372 	int ret;
373 	struct privcmd_mmapbatch_v2 m;
374 	struct mm_struct *mm = current->mm;
375 	struct vm_area_struct *vma;
376 	unsigned long nr_pages;
377 	LIST_HEAD(pagelist);
378 	struct mmap_batch_state state;
379 
380 	switch (version) {
381 	case 1:
382 		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
383 			return -EFAULT;
384 		/* Returns per-frame error in m.arr. */
385 		m.err = NULL;
386 		if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
387 			return -EFAULT;
388 		break;
389 	case 2:
390 		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
391 			return -EFAULT;
392 		/* Returns per-frame error code in m.err. */
393 		if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
394 			return -EFAULT;
395 		break;
396 	default:
397 		return -EINVAL;
398 	}
399 
400 	nr_pages = m.num;
401 	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
402 		return -EINVAL;
403 
404 	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);
405 
406 	if (ret)
407 		goto out;
408 	if (list_empty(&pagelist)) {
409 		ret = -EINVAL;
410 		goto out;
411 	}
412 
413 	if (version == 2) {
414 		/* Zero error array now to only copy back actual errors. */
415 		if (clear_user(m.err, sizeof(int) * m.num)) {
416 			ret = -EFAULT;
417 			goto out;
418 		}
419 	}
420 
421 	down_write(&mm->mmap_sem);
422 
423 	vma = find_vma(mm, m.addr);
424 	if (!vma ||
425 	    vma->vm_ops != &privcmd_vm_ops) {
426 		ret = -EINVAL;
427 		goto out_unlock;
428 	}
429 
430 	/*
431 	 * Caller must either:
432 	 *
433 	 * Map the whole VMA range, which will also allocate all the
434 	 * pages required for the auto_translated_physmap case.
435 	 *
436 	 * Or
437 	 *
438 	 * Map unmapped holes left from a previous map attempt (e.g.,
439 	 * because those foreign frames were previously paged out).
440 	 */
441 	if (vma->vm_private_data == NULL) {
442 		if (m.addr != vma->vm_start ||
443 		    m.addr + (nr_pages << PAGE_SHIFT) != vma->vm_end) {
444 			ret = -EINVAL;
445 			goto out_unlock;
446 		}
447 		if (xen_feature(XENFEAT_auto_translated_physmap)) {
448 			ret = alloc_empty_pages(vma, m.num);
449 			if (ret < 0)
450 				goto out_unlock;
451 		} else
452 			vma->vm_private_data = PRIV_VMA_LOCKED;
453 	} else {
454 		if (m.addr < vma->vm_start ||
455 		    m.addr + (nr_pages << PAGE_SHIFT) > vma->vm_end) {
456 			ret = -EINVAL;
457 			goto out_unlock;
458 		}
459 		if (privcmd_vma_range_is_mapped(vma, m.addr, nr_pages)) {
460 			ret = -EINVAL;
461 			goto out_unlock;
462 		}
463 	}
464 
465 	state.domain        = m.dom;
466 	state.vma           = vma;
467 	state.va            = m.addr;
468 	state.index         = 0;
469 	state.global_error  = 0;
470 	state.version       = version;
471 
472 	/* mmap_batch_fn guarantees ret == 0 */
473 	BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
474 			     &pagelist, mmap_batch_fn, &state));
475 
476 	up_write(&mm->mmap_sem);
477 
478 	if (state.global_error) {
479 		/* Write back errors in second pass. */
480 		state.user_mfn = (xen_pfn_t *)m.arr;
481 		state.user_err = m.err;
482 		ret = traverse_pages(m.num, sizeof(xen_pfn_t),
483 							 &pagelist, mmap_return_errors, &state);
484 	} else
485 		ret = 0;
486 
487 	/* If we have not had any EFAULT-like global errors then set the global
488 	 * error to -ENOENT if necessary. */
489 	if ((ret == 0) && (state.global_error == -ENOENT))
490 		ret = -ENOENT;
491 
492 out:
493 	free_page_list(&pagelist);
494 	return ret;
495 
496 out_unlock:
497 	up_write(&mm->mmap_sem);
498 	goto out;
499 }
500 
501 static long privcmd_ioctl(struct file *file,
502 			  unsigned int cmd, unsigned long data)
503 {
504 	int ret = -ENOSYS;
505 	void __user *udata = (void __user *) data;
506 
507 	switch (cmd) {
508 	case IOCTL_PRIVCMD_HYPERCALL:
509 		ret = privcmd_ioctl_hypercall(udata);
510 		break;
511 
512 	case IOCTL_PRIVCMD_MMAP:
513 		ret = privcmd_ioctl_mmap(udata);
514 		break;
515 
516 	case IOCTL_PRIVCMD_MMAPBATCH:
517 		ret = privcmd_ioctl_mmap_batch(udata, 1);
518 		break;
519 
520 	case IOCTL_PRIVCMD_MMAPBATCH_V2:
521 		ret = privcmd_ioctl_mmap_batch(udata, 2);
522 		break;
523 
524 	default:
525 		ret = -EINVAL;
526 		break;
527 	}
528 
529 	return ret;
530 }
531 
532 static void privcmd_close(struct vm_area_struct *vma)
533 {
534 	struct page **pages = vma->vm_private_data;
535 	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
536 	int rc;
537 
538 	if (!xen_feature(XENFEAT_auto_translated_physmap) || !numpgs || !pages)
539 		return;
540 
541 	rc = xen_unmap_domain_mfn_range(vma, numpgs, pages);
542 	if (rc == 0)
543 		free_xenballooned_pages(numpgs, pages);
544 	else
545 		pr_crit("unable to unmap MFN range: leaking %d pages. rc=%d\n",
546 			numpgs, rc);
547 	kfree(pages);
548 }
549 
550 static int privcmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
551 {
552 	printk(KERN_DEBUG "privcmd_fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
553 	       vma, vma->vm_start, vma->vm_end,
554 	       vmf->pgoff, vmf->virtual_address);
555 
556 	return VM_FAULT_SIGBUS;
557 }
558 
559 static struct vm_operations_struct privcmd_vm_ops = {
560 	.close = privcmd_close,
561 	.fault = privcmd_fault
562 };
563 
564 static int privcmd_mmap(struct file *file, struct vm_area_struct *vma)
565 {
566 	/* DONTCOPY is essential for Xen because copy_page_range doesn't know
567 	 * how to recreate these mappings */
568 	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTCOPY |
569 			 VM_DONTEXPAND | VM_DONTDUMP;
570 	vma->vm_ops = &privcmd_vm_ops;
571 	vma->vm_private_data = NULL;
572 
573 	return 0;
574 }
575 
576 /*
577  * For MMAPBATCH*. This allows asserting the singleshot mapping
578  * on a per pfn/pte basis. Mapping calls that fail with ENOENT
579  * can be then retried until success.
580  */
581 static int is_mapped_fn(pte_t *pte, struct page *pmd_page,
582 	                unsigned long addr, void *data)
583 {
584 	return pte_none(*pte) ? 0 : -EBUSY;
585 }
586 
587 static int privcmd_vma_range_is_mapped(
588 	           struct vm_area_struct *vma,
589 	           unsigned long addr,
590 	           unsigned long nr_pages)
591 {
592 	return apply_to_page_range(vma->vm_mm, addr, nr_pages << PAGE_SHIFT,
593 				   is_mapped_fn, NULL) != 0;
594 }
595 
596 const struct file_operations xen_privcmd_fops = {
597 	.owner = THIS_MODULE,
598 	.unlocked_ioctl = privcmd_ioctl,
599 	.mmap = privcmd_mmap,
600 };
601 EXPORT_SYMBOL_GPL(xen_privcmd_fops);
602 
603 static struct miscdevice privcmd_dev = {
604 	.minor = MISC_DYNAMIC_MINOR,
605 	.name = "xen/privcmd",
606 	.fops = &xen_privcmd_fops,
607 };
608 
609 static int __init privcmd_init(void)
610 {
611 	int err;
612 
613 	if (!xen_domain())
614 		return -ENODEV;
615 
616 	err = misc_register(&privcmd_dev);
617 	if (err != 0) {
618 		pr_err("Could not register Xen privcmd device\n");
619 		return err;
620 	}
621 	return 0;
622 }
623 
624 static void __exit privcmd_exit(void)
625 {
626 	misc_deregister(&privcmd_dev);
627 }
628 
629 module_init(privcmd_init);
630 module_exit(privcmd_exit);
631