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
mte_allocate_tag_storage(void)12 void *mte_allocate_tag_storage(void)
13 {
14 /* tags granule is 16 bytes, 2 tags stored per byte */
15 return kmalloc(MTE_PAGE_TAG_STORAGE, GFP_KERNEL);
16 }
17
mte_free_tag_storage(char * storage)18 void mte_free_tag_storage(char *storage)
19 {
20 kfree(storage);
21 }
22
mte_save_tags(struct page * page)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
mte_restore_tags(swp_entry_t entry,struct page * page)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 /*
66 * Test PG_mte_tagged again in case it was racing with another
67 * set_pte_at().
68 */
69 if (!test_and_set_bit(PG_mte_tagged, &page->flags))
70 mte_restore_page_tags(page_address(page), tags);
71
72 return true;
73 }
74
mte_invalidate_tags(int type,pgoff_t offset)75 void mte_invalidate_tags(int type, pgoff_t offset)
76 {
77 swp_entry_t entry = swp_entry(type, offset);
78 void *tags = xa_erase(&mte_pages, entry.val);
79
80 mte_free_tag_storage(tags);
81 }
82
mte_invalidate_tags_area(int type)83 void mte_invalidate_tags_area(int type)
84 {
85 swp_entry_t entry = swp_entry(type, 0);
86 swp_entry_t last_entry = swp_entry(type + 1, 0);
87 void *tags;
88
89 XA_STATE(xa_state, &mte_pages, entry.val);
90
91 xa_lock(&mte_pages);
92 xas_for_each(&xa_state, tags, last_entry.val - 1) {
93 __xa_erase(&mte_pages, xa_state.xa_index);
94 mte_free_tag_storage(tags);
95 }
96 xa_unlock(&mte_pages);
97 }
98