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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/pagemap.h>
#include <linux/xarray.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <asm/mte.h>
static DEFINE_XARRAY(mte_pages);
void *mte_allocate_tag_storage(void)
{
/* tags granule is 16 bytes, 2 tags stored per byte */
return kmalloc(PAGE_SIZE / 16 / 2, GFP_KERNEL);
}
void mte_free_tag_storage(char *storage)
{
kfree(storage);
}
int mte_save_tags(struct page *page)
{
void *tag_storage, *ret;
if (!test_bit(PG_mte_tagged, &page->flags))
return 0;
tag_storage = mte_allocate_tag_storage();
if (!tag_storage)
return -ENOMEM;
mte_save_page_tags(page_address(page), tag_storage);
/* page_private contains the swap entry.val set in do_swap_page */
ret = xa_store(&mte_pages, page_private(page), tag_storage, GFP_KERNEL);
if (WARN(xa_is_err(ret), "Failed to store MTE tags")) {
mte_free_tag_storage(tag_storage);
return xa_err(ret);
} else if (ret) {
/* Entry is being replaced, free the old entry */
mte_free_tag_storage(ret);
}
return 0;
}
bool mte_restore_tags(swp_entry_t entry, struct page *page)
{
void *tags = xa_load(&mte_pages, entry.val);
if (!tags)
return false;
page_kasan_tag_reset(page);
/*
* We need smp_wmb() in between setting the flags and clearing the
* tags because if another thread reads page->flags and builds a
* tagged address out of it, there is an actual dependency to the
* memory access, but on the current thread we do not guarantee that
* the new page->flags are visible before the tags were updated.
*/
smp_wmb();
mte_restore_page_tags(page_address(page), tags);
return true;
}
void mte_invalidate_tags(int type, pgoff_t offset)
{
swp_entry_t entry = swp_entry(type, offset);
void *tags = xa_erase(&mte_pages, entry.val);
mte_free_tag_storage(tags);
}
void mte_invalidate_tags_area(int type)
{
swp_entry_t entry = swp_entry(type, 0);
swp_entry_t last_entry = swp_entry(type + 1, 0);
void *tags;
XA_STATE(xa_state, &mte_pages, entry.val);
xa_lock(&mte_pages);
xas_for_each(&xa_state, tags, last_entry.val - 1) {
__xa_erase(&mte_pages, xa_state.xa_index);
mte_free_tag_storage(tags);
}
xa_unlock(&mte_pages);
}
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