arch/arm64/mm/mteswap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <linux/pagemap.h>
   4 #include <linux/xarray.h>
   5 #include <linux/slab.h>
   6 #include <linux/swap.h>
   7 #include <linux/swapops.h>
   8 #include <asm/mte.h>
   9
  10 static DEFINE_XARRAY(mte_pages);
  11
  12 void *mte_allocate_tag_storage(void)
  13 {
  14         /* tags granule is 16 bytes, 2 tags stored per byte */
  15         return kmalloc(PAGE_SIZE / 16 / 2, GFP_KERNEL);
  16 }
  17
  18 void mte_free_tag_storage(char *storage)
  19 {
  20         kfree(storage);
  21 }
  22
  23 int mte_save_tags(struct page *page)
  24 {
  25         void *tag_storage, *ret;
  26
  27         if (!test_bit(PG_mte_tagged, &page->flags))
  28                 return 0;
  29
  30         tag_storage = mte_allocate_tag_storage();
  31         if (!tag_storage)
  32                 return -ENOMEM;
  33
  34         mte_save_page_tags(page_address(page), tag_storage);
  35
  36         /* page_private contains the swap entry.val set in do_swap_page */
  37         ret = xa_store(&mte_pages, page_private(page), tag_storage, GFP_KERNEL);
  38         if (WARN(xa_is_err(ret), "Failed to store MTE tags")) {
  39                 mte_free_tag_storage(tag_storage);
  40                 return xa_err(ret);
  41         } else if (ret) {
  42                 /* Entry is being replaced, free the old entry */
  43                 mte_free_tag_storage(ret);
  44         }
  45
  46         return 0;
  47 }
  48
  49 bool mte_restore_tags(swp_entry_t entry, struct page *page)
  50 {
  51         void *tags = xa_load(&mte_pages, entry.val);
  52
  53         if (!tags)
  54                 return false;
  55
  56         page_kasan_tag_reset(page);
  57         /*
  58          * We need smp_wmb() in between setting the flags and clearing the
  59          * tags because if another thread reads page->flags and builds a
  60          * tagged address out of it, there is an actual dependency to the
  61          * memory access, but on the current thread we do not guarantee that
  62          * the new page->flags are visible before the tags were updated.
  63          */
  64         smp_wmb();
  65         mte_restore_page_tags(page_address(page), tags);
  66
  67         return true;
  68 }
  69
  70 void mte_invalidate_tags(int type, pgoff_t offset)
  71 {
  72         swp_entry_t entry = swp_entry(type, offset);
  73         void *tags = xa_erase(&mte_pages, entry.val);
  74
  75         mte_free_tag_storage(tags);
  76 }
  77
  78 void mte_invalidate_tags_area(int type)
  79 {
  80         swp_entry_t entry = swp_entry(type, 0);
  81         swp_entry_t last_entry = swp_entry(type + 1, 0);
  82         void *tags;
  83
  84         XA_STATE(xa_state, &mte_pages, entry.val);
  85
  86         xa_lock(&mte_pages);
  87         xas_for_each(&xa_state, tags, last_entry.val - 1) {
  88                 __xa_erase(&mte_pages, xa_state.xa_index);
  89                 mte_free_tag_storage(tags);
  90         }
  91         xa_unlock(&mte_pages);
  92 }