1#include <linux/kernel.h>
  2#include <linux/errno.h>
  3#include <linux/err.h>
  4#include <linux/mm.h>
  5#include <linux/slab.h>
  6#include <linux/vmalloc.h>
  7#include <linux/pagemap.h>
  8#include <linux/sched.h>
  9
 10/**
 11 * get_vaddr_frames() - map virtual addresses to pfns
 12 * @start:	starting user address
 13 * @nr_frames:	number of pages / pfns from start to map
 14 * @write:	whether pages will be written to by the caller
 15 * @force:	whether to force write access even if user mapping is
 16 *		readonly. See description of the same argument of
 17		get_user_pages().
 18 * @vec:	structure which receives pages / pfns of the addresses mapped.
 19 *		It should have space for at least nr_frames entries.
 20 *
 21 * This function maps virtual addresses from @start and fills @vec structure
 22 * with page frame numbers or page pointers to corresponding pages (choice
 23 * depends on the type of the vma underlying the virtual address). If @start
 24 * belongs to a normal vma, the function grabs reference to each of the pages
 25 * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
 26 * touch page structures and the caller must make sure pfns aren't reused for
 27 * anything else while he is using them.
 28 *
 29 * The function returns number of pages mapped which may be less than
 30 * @nr_frames. In particular we stop mapping if there are more vmas of
 31 * different type underlying the specified range of virtual addresses.
 32 * When the function isn't able to map a single page, it returns error.
 33 *
 34 * This function takes care of grabbing mmap_sem as necessary.
 35 */
 36int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 37		     bool write, bool force, struct frame_vector *vec)
 38{
 39	struct mm_struct *mm = current->mm;
 40	struct vm_area_struct *vma;
 41	int ret = 0;
 42	int err;
 43	int locked;
 44
 45	if (nr_frames == 0)
 46		return 0;
 47
 48	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
 49		nr_frames = vec->nr_allocated;
 50
 51	down_read(&mm->mmap_sem);
 52	locked = 1;
 53	vma = find_vma_intersection(mm, start, start + 1);
 54	if (!vma) {
 55		ret = -EFAULT;
 56		goto out;
 57	}
 58	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
 59		vec->got_ref = true;
 60		vec->is_pfns = false;
 61		ret = get_user_pages_locked(start, nr_frames,
 62			write, force, (struct page **)(vec->ptrs), &locked);
 63		goto out;
 64	}
 65
 66	vec->got_ref = false;
 67	vec->is_pfns = true;
 68	do {
 69		unsigned long *nums = frame_vector_pfns(vec);
 70
 71		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
 72			err = follow_pfn(vma, start, &nums[ret]);
 73			if (err) {
 74				if (ret == 0)
 75					ret = err;
 76				goto out;
 77			}
 78			start += PAGE_SIZE;
 79			ret++;
 80		}
 81		/*
 82		 * We stop if we have enough pages or if VMA doesn't completely
 83		 * cover the tail page.
 84		 */
 85		if (ret >= nr_frames || start < vma->vm_end)
 86			break;
 87		vma = find_vma_intersection(mm, start, start + 1);
 88	} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
 89out:
 90	if (locked)
 91		up_read(&mm->mmap_sem);
 92	if (!ret)
 93		ret = -EFAULT;
 94	if (ret > 0)
 95		vec->nr_frames = ret;
 96	return ret;
 97}
 98EXPORT_SYMBOL(get_vaddr_frames);
 99
100/**
101 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
102 *			them
103 * @vec:	frame vector to put
104 *
105 * Drop references to pages if get_vaddr_frames() acquired them. We also
106 * invalidate the frame vector so that it is prepared for the next call into
107 * get_vaddr_frames().
108 */
109void put_vaddr_frames(struct frame_vector *vec)
110{
111	int i;
112	struct page **pages;
113
114	if (!vec->got_ref)
115		goto out;
116	pages = frame_vector_pages(vec);
117	/*
118	 * frame_vector_pages() might needed to do a conversion when
119	 * get_vaddr_frames() got pages but vec was later converted to pfns.
120	 * But it shouldn't really fail to convert pfns back...
121	 */
122	if (WARN_ON(IS_ERR(pages)))
123		goto out;
124	for (i = 0; i < vec->nr_frames; i++)
125		put_page(pages[i]);
126	vec->got_ref = false;
127out:
128	vec->nr_frames = 0;
129}
130EXPORT_SYMBOL(put_vaddr_frames);
131
132/**
133 * frame_vector_to_pages - convert frame vector to contain page pointers
134 * @vec:	frame vector to convert
135 *
136 * Convert @vec to contain array of page pointers.  If the conversion is
137 * successful, return 0. Otherwise return an error. Note that we do not grab
138 * page references for the page structures.
139 */
140int frame_vector_to_pages(struct frame_vector *vec)
141{
142	int i;
143	unsigned long *nums;
144	struct page **pages;
145
146	if (!vec->is_pfns)
147		return 0;
148	nums = frame_vector_pfns(vec);
149	for (i = 0; i < vec->nr_frames; i++)
150		if (!pfn_valid(nums[i]))
151			return -EINVAL;
152	pages = (struct page **)nums;
153	for (i = 0; i < vec->nr_frames; i++)
154		pages[i] = pfn_to_page(nums[i]);
155	vec->is_pfns = false;
156	return 0;
157}
158EXPORT_SYMBOL(frame_vector_to_pages);
159
160/**
161 * frame_vector_to_pfns - convert frame vector to contain pfns
162 * @vec:	frame vector to convert
163 *
164 * Convert @vec to contain array of pfns.
165 */
166void frame_vector_to_pfns(struct frame_vector *vec)
167{
168	int i;
169	unsigned long *nums;
170	struct page **pages;
171
172	if (vec->is_pfns)
173		return;
174	pages = (struct page **)(vec->ptrs);
175	nums = (unsigned long *)pages;
176	for (i = 0; i < vec->nr_frames; i++)
177		nums[i] = page_to_pfn(pages[i]);
178	vec->is_pfns = true;
179}
180EXPORT_SYMBOL(frame_vector_to_pfns);
181
182/**
183 * frame_vector_create() - allocate & initialize structure for pinned pfns
184 * @nr_frames:	number of pfns slots we should reserve
185 *
186 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
187 * pfns.
188 */
189struct frame_vector *frame_vector_create(unsigned int nr_frames)
190{
191	struct frame_vector *vec;
192	int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
193
194	if (WARN_ON_ONCE(nr_frames == 0))
195		return NULL;
196	/*
197	 * This is absurdly high. It's here just to avoid strange effects when
198	 * arithmetics overflows.
199	 */
200	if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
201		return NULL;
202	/*
203	 * Avoid higher order allocations, use vmalloc instead. It should
204	 * be rare anyway.
205	 */
206	if (size <= PAGE_SIZE)
207		vec = kmalloc(size, GFP_KERNEL);
208	else
209		vec = vmalloc(size);
210	if (!vec)
211		return NULL;
212	vec->nr_allocated = nr_frames;
213	vec->nr_frames = 0;
214	return vec;
215}
216EXPORT_SYMBOL(frame_vector_create);
217
218/**
219 * frame_vector_destroy() - free memory allocated to carry frame vector
220 * @vec:	Frame vector to free
221 *
222 * Free structure allocated by frame_vector_create() to carry frames.
223 */
224void frame_vector_destroy(struct frame_vector *vec)
225{
226	/* Make sure put_vaddr_frames() got called properly... */
227	VM_BUG_ON(vec->nr_frames > 0);
228	kvfree(vec);
229}
230EXPORT_SYMBOL(frame_vector_destroy);