1/*
2 * Copyright (c) 2022 Apple Computer, Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28#ifndef _MACH_VM_MEMTAG_H_
29#define _MACH_VM_MEMTAG_H_
30
31#ifdef KERNEL
32
33#include <mach/vm_types.h>
34
35#if CONFIG_KERNEL_TAGGING
36
37/* Zero-out a tagged memory region. */
38extern void vm_memtag_bzero(void *tagged_buf, vm_size_t n);
39
40/* Retrieve the tag metadata associated to the target memory address */
41extern uint8_t vm_memtag_get_tag(vm_offset_t address);
42
43/*
44 * Given a naked address, extract the metadata from memory and add it to
45 * the correct pointer metadata.
46 */
47extern vm_offset_t vm_memtag_fixup_ptr(vm_offset_t naked_address);
48
49/*
50 * Given a tagged pointer and a size, update the associated backing metadata
51 * to match the pointer metadata.
52 */
53extern void
54vm_memtag_set_tag(vm_offset_t tagged_address, vm_offset_t size);
55
56/*
57 * Randomly assign a tag to the current chunk of memory. Memory metadata is
58 * not updated yet and must be committed through a call to vm_memtag_set_tag().
59 * This helper will implement a basic randomization algorithm that picks a
60 * random valid value for the tagging mechanism excluding the current and
61 * left/right adjacent metadata value. This approach is fault-conservative and
62 * only checks the adjacent memory locations if they fit within the same page.
63 */
64extern vm_offset_t
65vm_memtag_assign_tag(vm_offset_t address, vm_size_t size);
66
67/*
68 * When passed a tagged pointer, verify that the pointer metadata matches
69 * the backing storage metadata.
70 */
71extern void
72vm_memtag_verify_tag(vm_offset_t tagged_address);
73
74/*
75 * Temporarily enable/disable memtag checking.
76 */
77extern void
78vm_memtag_enable_checking(void);
79extern void
80vm_memtag_disable_checking(void);
81
82/*
83 * Helper functions to manipulate tagged pointers. If more implementors of
84 * the vm_memtag interface beyond KASAN-TBI were to come, then these definitions
85 * should be ifdef guarded properly.
86 */
87#define VM_MEMTAG_PTR_SIZE 56
88#define VM_MEMTAG_TAG_SIZE 4
89#define VM_MEMTAG_UPPER_SIZE 4
90
91union vm_memtag_ptr {
92 long value;
93
94 struct {
95 long ptr_bits: VM_MEMTAG_PTR_SIZE;
96 uint8_t ptr_tag: VM_MEMTAG_TAG_SIZE;
97 long ptr_upper: VM_MEMTAG_UPPER_SIZE;
98 };
99};
100
101static inline vm_offset_t
102vm_memtag_add_ptr_tag(vm_offset_t naked_ptr, uint8_t tag)
103{
104 union vm_memtag_ptr p = {
105 .value = (long)naked_ptr,
106 };
107
108 p.ptr_tag = tag;
109 return (vm_offset_t)p.value;
110}
111
112static inline uint8_t
113vm_memtag_extract_tag(vm_offset_t tagged_ptr)
114{
115 union vm_memtag_ptr p = {
116 .value = (long)tagged_ptr,
117 };
118
119 return p.ptr_tag;
120}
121
122/*
123 * when passed a tagged pointer, strip away the tag bits and return the
124 * canonical address. Since it's used in a number of frequently called checks
125 * (e.g. when packing VM pointers), the following definition hardcodes the
126 * tag value to achieve optimal codegen and no external calls.
127 */
128#define vm_memtag_canonicalize_address(addr) vm_memtag_add_ptr_tag(addr, 0xF)
129#define vm_memtag_canonicalize_user_address(addr) vm_memtag_add_ptr_tag(addr, 0x0)
130
131#else /* CONFIG_KERNEL_TAGGING */
132
133#define vm_memtag_bzero(p, s) bzero(p, s)
134#define vm_memtag_get_tag(a) (0xF)
135#define vm_memtag_fixup_ptr(a) (a)
136#define vm_memtag_set_tag(a, s) do { } while (0)
137#define vm_memtag_assign_tag(a, s) (a)
138#define vm_memtag_add_ptr_tag(p, t) (p)
139#define vm_memtag_extract_tag(p) (0xF)
140#define vm_memtag_canonicalize_address(a) (a)
141#define vm_memtag_enable_checking() do { } while (0)
142#define vm_memtag_disable_checking() do { } while (0)
143
144
145#endif /* CONFIG_KERNEL_TAGGING */
146
147#endif /* KERNEL */
148
149#endif /* _MACH_VM_MEMTAG_H_ */
150