LXR linux/drivers/media/common/videobuf2/frame

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