1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file contains hardware tag-based KASAN specific error reporting code.
4 *
5 * Copyright (c) 2020 Google, Inc.
6 * Author: Andrey Konovalov <andreyknvl@google.com>
7 */
8
9#include <linux/kasan.h>
10#include <linux/kernel.h>
11#include <linux/memory.h>
12#include <linux/mm.h>
13#include <linux/string.h>
14#include <linux/types.h>
15
16#include "kasan.h"
17
18const void *kasan_find_first_bad_addr(const void *addr, size_t size)
19{
20 /*
21 * Hardware Tag-Based KASAN only calls this function for normal memory
22 * accesses, and thus addr points precisely to the first bad address
23 * with an invalid (and present) memory tag. Therefore:
24 * 1. Return the address as is without walking memory tags.
25 * 2. Skip the addr_has_metadata check.
26 */
27 return kasan_reset_tag(addr);
28}
29
30size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache)
31{
32 size_t size = 0;
33 int i = 0;
34 u8 memory_tag;
35
36 /*
37 * Skip the addr_has_metadata check, as this function only operates on
38 * slab memory, which must have metadata.
39 */
40
41 /*
42 * The loop below returns 0 for freed objects, for which KASAN cannot
43 * calculate the allocation size based on the metadata.
44 */
45 while (size < cache->object_size) {
46 memory_tag = hw_get_mem_tag(object + i * KASAN_GRANULE_SIZE);
47 if (memory_tag != KASAN_TAG_INVALID)
48 size += KASAN_GRANULE_SIZE;
49 else
50 return size;
51 i++;
52 }
53
54 return cache->object_size;
55}
56
57void kasan_metadata_fetch_row(char *buffer, void *row)
58{
59 int i;
60
61 for (i = 0; i < META_BYTES_PER_ROW; i++)
62 buffer[i] = hw_get_mem_tag(row + i * KASAN_GRANULE_SIZE);
63}
64
65void kasan_print_tags(u8 addr_tag, const void *addr)
66{
67 u8 memory_tag = hw_get_mem_tag((void *)addr);
68
69 pr_err("Pointer tag: [%02x], memory tag: [%02x]\n",
70 addr_tag, memory_tag);
71}
72

source code of linux/mm/kasan/report_hw_tags.c