1 /* SPDX-License-Identifier: GPL-2.0 */ 1
2 /*
3 * KCSAN watchpoint encoding.
4 *
5 * Copyright (C) 2019, Google LLC.
6 */
7
8 #ifndef _KERNEL_KCSAN_ENCODING_H
9 #define _KERNEL_KCSAN_ENCODING_H
10
11 #include <linux/bits.h>
12 #include <linux/log2.h>
13 #include <linux/mm.h>
14
15 #include "kcsan.h"
16
17 #define SLOT_RANGE PAGE_SIZE
18
19 #define INVALID_WATCHPOINT 0
20 #define CONSUMED_WATCHPOINT 1
21
22 /*
23 * The maximum useful size of accesses for whi
24 * max range of slots we check on an access.
25 */
26 #define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 +
27
28 /*
29 * Number of bits we use to store size info.
30 */
31 #define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCO
32 /*
33 * This encoding for addresses discards the up
34 * however, most 64-bit architectures do not u
35 * Also, in order for a false positive to be o
36 *
37 * 1. different addresses but with the sa
38 * 2. and both map onto the same watchpoi
39 *
40 * Both these are assumed to be very unlikely.
41 * happens, the report logic will filter out t
42 */
43 #define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1
44
45 /* Bitmasks for the encoded watchpoint access
46 #define WATCHPOINT_WRITE_MASK BIT(BITS_PER_L
47 #define WATCHPOINT_SIZE_MASK GENMASK(BITS_P
48 #define WATCHPOINT_ADDR_MASK GENMASK(WATCHP
49 static_assert(WATCHPOINT_ADDR_MASK == (1UL <<
50 static_assert((WATCHPOINT_WRITE_MASK ^ WATCHPO
51
52 static inline bool check_encodable(unsigned lo
53 {
54 /*
55 * While we can encode addrs<PAGE_SIZE
56 * pointer deref inside KCSAN.
57 */
58 return addr >= PAGE_SIZE && size <= MA
59 }
60
61 static inline long
62 encode_watchpoint(unsigned long addr, size_t s
63 {
64 return (long)((is_write ? WATCHPOINT_W
65 (size << WATCHPOINT_ADDR
66 (addr & WATCHPOINT_ADDR_
67 }
68
69 static __always_inline bool decode_watchpoint(
70
71
72
73 {
74 if (watchpoint == INVALID_WATCHPOINT |
75 watchpoint == CONSUMED_WATCHPOINT)
76 return false;
77
78 *addr_masked = (unsigned long)watch
79 *size = ((unsigned long)watch
80 *is_write = !!((unsigned long)watch
81
82 return true;
83 }
84
85 /*
86 * Return watchpoint slot for an address.
87 */
88 static __always_inline int watchpoint_slot(uns
89 {
90 return (addr / PAGE_SIZE) % CONFIG_KCS
91 }
92
93 static __always_inline bool matching_access(un
94 un
95 {
96 unsigned long end_range1 = addr1 + siz
97 unsigned long end_range2 = addr2 + siz
98
99 return addr1 <= end_range2 && addr2 <=
100 }
101
102 #endif /* _KERNEL_KCSAN_ENCODING_H */
103
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