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 } 93