1// SPDX-License-Identifier: GPL-2.0
  2#include <linux/kernel.h>
  3#include <linux/errno.h>
  4#include <linux/err.h>
  5#include <linux/mm.h>
  6#include <linux/slab.h>
  7#include <linux/vmalloc.h>
  8#include <linux/pagemap.h>
  9#include <linux/sched.h>
 10
 11/**
 12 * get_vaddr_frames() - map virtual addresses to pfns
 13 * @start:	starting user address
 14 * @nr_frames:	number of pages / pfns from start to map
 15 * @gup_flags:	flags modifying lookup behaviour
 16 * @vec:	structure which receives pages / pfns of the addresses mapped.
 17 *		It should have space for at least nr_frames entries.
 18 *
 19 * This function maps virtual addresses from @start and fills @vec structure
 20 * with page frame numbers or page pointers to corresponding pages (choice
 21 * depends on the type of the vma underlying the virtual address). If @start
 22 * belongs to a normal vma, the function grabs reference to each of the pages
 23 * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
 24 * touch page structures and the caller must make sure pfns aren't reused for
 25 * anything else while he is using them.
 26 *
 27 * The function returns number of pages mapped which may be less than
 28 * @nr_frames. In particular we stop mapping if there are more vmas of
 29 * different type underlying the specified range of virtual addresses.
 30 * When the function isn't able to map a single page, it returns error.
 31 *
 32 * This function takes care of grabbing mmap_sem as necessary.
 33 */
 34int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 35		     unsigned int gup_flags, struct frame_vector *vec)
 36{
 37	struct mm_struct *mm = current->mm;
 38	struct vm_area_struct *vma;
 39	int ret = 0;
 40	int err;
 41	int locked;
 42
 43	if (nr_frames == 0)
 44		return 0;
 45
 46	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
 47		nr_frames = vec->nr_allocated;
 48
 49	start = untagged_addr(start);
 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
 59	/*
 60	 * While get_vaddr_frames() could be used for transient (kernel
 61	 * controlled lifetime) pinning of memory pages all current
 62	 * users establish long term (userspace controlled lifetime)
 63	 * page pinning. Treat get_vaddr_frames() like
 64	 * get_user_pages_longterm() and disallow it for filesystem-dax
 65	 * mappings.
 66	 */
 67	if (vma_is_fsdax(vma)) {
 68		ret = -EOPNOTSUPP;
 69		goto out;
 70	}
 71
 72	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
 73		vec->got_ref = true;
 74		vec->is_pfns = false;
 75		ret = get_user_pages_locked(start, nr_frames,
 76			gup_flags, (struct page **)(vec->ptrs), &locked);
 77		goto out;
 78	}
 79
 80	vec->got_ref = false;
 81	vec->is_pfns = true;
 82	do {
 83		unsigned long *nums = frame_vector_pfns(vec);
 84
 85		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
 86			err = follow_pfn(vma, start, &nums[ret]);
 87			if (err) {
 88				if (ret == 0)
 89					ret = err;
 90				goto out;
 91			}
 92			start += PAGE_SIZE;
 93			ret++;
 94		}
 95		/*
 96		 * We stop if we have enough pages or if VMA doesn't completely
 97		 * cover the tail page.
 98		 */
 99		if (ret >= nr_frames || start < vma->vm_end)
100			break;
101		vma = find_vma_intersection(mm, start, start + 1);
102	} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
103out:
104	if (locked)
105		up_read(&mm->mmap_sem);
106	if (!ret)
107		ret = -EFAULT;
108	if (ret > 0)
109		vec->nr_frames = ret;
110	return ret;
111}
112EXPORT_SYMBOL(get_vaddr_frames);
113
114/**
115 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
116 *			them
117 * @vec:	frame vector to put
118 *
119 * Drop references to pages if get_vaddr_frames() acquired them. We also
120 * invalidate the frame vector so that it is prepared for the next call into
121 * get_vaddr_frames().
122 */
123void put_vaddr_frames(struct frame_vector *vec)
124{
125	int i;
126	struct page **pages;
127
128	if (!vec->got_ref)
129		goto out;
130	pages = frame_vector_pages(vec);
131	/*
132	 * frame_vector_pages() might needed to do a conversion when
133	 * get_vaddr_frames() got pages but vec was later converted to pfns.
134	 * But it shouldn't really fail to convert pfns back...
135	 */
136	if (WARN_ON(IS_ERR(pages)))
137		goto out;
138	for (i = 0; i < vec->nr_frames; i++)
139		put_page(pages[i]);
140	vec->got_ref = false;
141out:
142	vec->nr_frames = 0;
143}
144EXPORT_SYMBOL(put_vaddr_frames);
145
146/**
147 * frame_vector_to_pages - convert frame vector to contain page pointers
148 * @vec:	frame vector to convert
149 *
150 * Convert @vec to contain array of page pointers.  If the conversion is
151 * successful, return 0. Otherwise return an error. Note that we do not grab
152 * page references for the page structures.
153 */
154int frame_vector_to_pages(struct frame_vector *vec)
155{
156	int i;
157	unsigned long *nums;
158	struct page **pages;
159
160	if (!vec->is_pfns)
161		return 0;
162	nums = frame_vector_pfns(vec);
163	for (i = 0; i < vec->nr_frames; i++)
164		if (!pfn_valid(nums[i]))
165			return -EINVAL;
166	pages = (struct page **)nums;
167	for (i = 0; i < vec->nr_frames; i++)
168		pages[i] = pfn_to_page(nums[i]);
169	vec->is_pfns = false;
170	return 0;
171}
172EXPORT_SYMBOL(frame_vector_to_pages);
173
174/**
175 * frame_vector_to_pfns - convert frame vector to contain pfns
176 * @vec:	frame vector to convert
177 *
178 * Convert @vec to contain array of pfns.
179 */
180void frame_vector_to_pfns(struct frame_vector *vec)
181{
182	int i;
183	unsigned long *nums;
184	struct page **pages;
185
186	if (vec->is_pfns)
187		return;
188	pages = (struct page **)(vec->ptrs);
189	nums = (unsigned long *)pages;
190	for (i = 0; i < vec->nr_frames; i++)
191		nums[i] = page_to_pfn(pages[i]);
192	vec->is_pfns = true;
193}
194EXPORT_SYMBOL(frame_vector_to_pfns);
195
196/**
197 * frame_vector_create() - allocate & initialize structure for pinned pfns
198 * @nr_frames:	number of pfns slots we should reserve
199 *
200 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
201 * pfns.
202 */
203struct frame_vector *frame_vector_create(unsigned int nr_frames)
204{
205	struct frame_vector *vec;
206	int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
207
208	if (WARN_ON_ONCE(nr_frames == 0))
209		return NULL;
210	/*
211	 * This is absurdly high. It's here just to avoid strange effects when
212	 * arithmetics overflows.
213	 */
214	if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
215		return NULL;
216	/*
217	 * Avoid higher order allocations, use vmalloc instead. It should
218	 * be rare anyway.
219	 */
220	vec = kvmalloc(size, GFP_KERNEL);
221	if (!vec)
222		return NULL;
223	vec->nr_allocated = nr_frames;
224	vec->nr_frames = 0;
225	return vec;
226}
227EXPORT_SYMBOL(frame_vector_create);
228
229/**
230 * frame_vector_destroy() - free memory allocated to carry frame vector
231 * @vec:	Frame vector to free
232 *
233 * Free structure allocated by frame_vector_create() to carry frames.
234 */
235void frame_vector_destroy(struct frame_vector *vec)
236{
237	/* Make sure put_vaddr_frames() got called properly... */
238	VM_BUG_ON(vec->nr_frames > 0);
239	kvfree(vec);
240}
241EXPORT_SYMBOL(frame_vector_destroy);