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. */
38 extern void vm_memtag_bzero(void *tagged_buf, vm_size_t n);
39
40 /* Retrieve the tag metadata associated to the target memory address */
41 extern 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 */
47 extern 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 */
53 extern void
54 vm_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 */
64 extern vm_offset_t
65 vm_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 */
71 extern void
72 vm_memtag_verify_tag(vm_offset_t tagged_address);
73
74 /*
75 * Temporarily enable/disable memtag checking.
76 */
77 extern void
78 vm_memtag_enable_checking(void);
79 extern void
80 vm_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
91 union 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
101 static inline vm_offset_t
vm_memtag_add_ptr_tag(vm_offset_t naked_ptr,uint8_t tag)102 vm_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
112 static inline uint8_t
vm_memtag_extract_tag(vm_offset_t tagged_ptr)113 vm_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
130 #else /* CONFIG_KERNEL_TAGGING */
131
132 #define vm_memtag_bzero(p, s) bzero(p, s)
133 #define vm_memtag_get_tag(a) (0xF)
134 #define vm_memtag_fixup_ptr(a) (a)
135 #define vm_memtag_set_tag(a, s) do { } while (0)
136 #define vm_memtag_assign_tag(a, s) (a)
137 #define vm_memtag_add_ptr_tag(p, t) (p)
138 #define vm_memtag_extract_tag(p) (0xF)
139 #define vm_memtag_canonicalize_address(a) (a)
140 #define vm_memtag_enable_checking() do { } while (0)
141 #define vm_memtag_disable_checking() do { } while (0)
142
143 #endif /* CONFIG_KERNEL_TAGGING */
144
145 #endif /* KERNEL */
146
147 #endif /* _MACH_VM_MEMTAG_H_ */
148