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	down_read(&mm->mmap_sem);
 50	locked = 1;
 51	vma = find_vma_intersection(mm, start, start + 1);
 52	if (!vma) {
 53		ret = -EFAULT;
 54		goto out;
 55	}
 56
 57	/*
 58	 * While get_vaddr_frames() could be used for transient (kernel
 59	 * controlled lifetime) pinning of memory pages all current
 60	 * users establish long term (userspace controlled lifetime)
 61	 * page pinning. Treat get_vaddr_frames() like
 62	 * get_user_pages_longterm() and disallow it for filesystem-dax
 63	 * mappings.
 64	 */
 65	if (vma_is_fsdax(vma)) {
 66		ret = -EOPNOTSUPP;
 67		goto out;
 68	}
 69
 70	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
 71		vec->got_ref = true;
 72		vec->is_pfns = false;
 73		ret = get_user_pages_locked(start, nr_frames,
 74			gup_flags, (struct page **)(vec->ptrs), &locked);
 75		goto out;
 76	}
 77
 78	vec->got_ref = false;
 79	vec->is_pfns = true;
 80	do {
 81		unsigned long *nums = frame_vector_pfns(vec);
 82
 83		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
 84			err = follow_pfn(vma, start, &nums[ret]);
 85			if (err) {
 86				if (ret == 0)
 87					ret = err;
 88				goto out;
 89			}
 90			start += PAGE_SIZE;
 91			ret++;
 92		}
 93		/*
 94		 * We stop if we have enough pages or if VMA doesn't completely
 95		 * cover the tail page.
 96		 */
 97		if (ret >= nr_frames || start < vma->vm_end)
 98			break;
 99		vma = find_vma_intersection(mm, start, start + 1);
100	} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
101out:
102	if (locked)
103		up_read(&mm->mmap_sem);
104	if (!ret)
105		ret = -EFAULT;
106	if (ret > 0)
107		vec->nr_frames = ret;
108	return ret;
109}
110EXPORT_SYMBOL(get_vaddr_frames);
111
112/**
113 * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
114 *			them
115 * @vec:	frame vector to put
116 *
117 * Drop references to pages if get_vaddr_frames() acquired them. We also
118 * invalidate the frame vector so that it is prepared for the next call into
119 * get_vaddr_frames().
120 */
121void put_vaddr_frames(struct frame_vector *vec)
122{
123	int i;
124	struct page **pages;
125
126	if (!vec->got_ref)
127		goto out;
128	pages = frame_vector_pages(vec);
129	/*
130	 * frame_vector_pages() might needed to do a conversion when
131	 * get_vaddr_frames() got pages but vec was later converted to pfns.
132	 * But it shouldn't really fail to convert pfns back...
133	 */
134	if (WARN_ON(IS_ERR(pages)))
135		goto out;
136	for (i = 0; i < vec->nr_frames; i++)
137		put_page(pages[i]);
138	vec->got_ref = false;
139out:
140	vec->nr_frames = 0;
141}
142EXPORT_SYMBOL(put_vaddr_frames);
143
144/**
145 * frame_vector_to_pages - convert frame vector to contain page pointers
146 * @vec:	frame vector to convert
147 *
148 * Convert @vec to contain array of page pointers.  If the conversion is
149 * successful, return 0. Otherwise return an error. Note that we do not grab
150 * page references for the page structures.
151 */
152int frame_vector_to_pages(struct frame_vector *vec)
153{
154	int i;
155	unsigned long *nums;
156	struct page **pages;
157
158	if (!vec->is_pfns)
159		return 0;
160	nums = frame_vector_pfns(vec);
161	for (i = 0; i < vec->nr_frames; i++)
162		if (!pfn_valid(nums[i]))
163			return -EINVAL;
164	pages = (struct page **)nums;
165	for (i = 0; i < vec->nr_frames; i++)
166		pages[i] = pfn_to_page(nums[i]);
167	vec->is_pfns = false;
168	return 0;
169}
170EXPORT_SYMBOL(frame_vector_to_pages);
171
172/**
173 * frame_vector_to_pfns - convert frame vector to contain pfns
174 * @vec:	frame vector to convert
175 *
176 * Convert @vec to contain array of pfns.
177 */
178void frame_vector_to_pfns(struct frame_vector *vec)
179{
180	int i;
181	unsigned long *nums;
182	struct page **pages;
183
184	if (vec->is_pfns)
185		return;
186	pages = (struct page **)(vec->ptrs);
187	nums = (unsigned long *)pages;
188	for (i = 0; i < vec->nr_frames; i++)
189		nums[i] = page_to_pfn(pages[i]);
190	vec->is_pfns = true;
191}
192EXPORT_SYMBOL(frame_vector_to_pfns);
193
194/**
195 * frame_vector_create() - allocate & initialize structure for pinned pfns
196 * @nr_frames:	number of pfns slots we should reserve
197 *
198 * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
199 * pfns.
200 */
201struct frame_vector *frame_vector_create(unsigned int nr_frames)
202{
203	struct frame_vector *vec;
204	int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
205
206	if (WARN_ON_ONCE(nr_frames == 0))
207		return NULL;
208	/*
209	 * This is absurdly high. It's here just to avoid strange effects when
210	 * arithmetics overflows.
211	 */
212	if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
213		return NULL;
214	/*
215	 * Avoid higher order allocations, use vmalloc instead. It should
216	 * be rare anyway.
217	 */
218	vec = kvmalloc(size, GFP_KERNEL);
219	if (!vec)
220		return NULL;
221	vec->nr_allocated = nr_frames;
222	vec->nr_frames = 0;
223	return vec;
224}
225EXPORT_SYMBOL(frame_vector_create);
226
227/**
228 * frame_vector_destroy() - free memory allocated to carry frame vector
229 * @vec:	Frame vector to free
230 *
231 * Free structure allocated by frame_vector_create() to carry frames.
232 */
233void frame_vector_destroy(struct frame_vector *vec)
234{
235	/* Make sure put_vaddr_frames() got called properly... */
236	VM_BUG_ON(vec->nr_frames > 0);
237	kvfree(vec);
238}
239EXPORT_SYMBOL(frame_vector_destroy);