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dfd402a4 ME |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | ||
3 | #ifndef _KERNEL_KCSAN_ENCODING_H | |
4 | #define _KERNEL_KCSAN_ENCODING_H | |
5 | ||
6 | #include <linux/bits.h> | |
7 | #include <linux/log2.h> | |
8 | #include <linux/mm.h> | |
9 | ||
10 | #include "kcsan.h" | |
11 | ||
12 | #define SLOT_RANGE PAGE_SIZE | |
5cbaefe9 IM |
13 | |
14 | #define INVALID_WATCHPOINT 0 | |
dfd402a4 ME |
15 | #define CONSUMED_WATCHPOINT 1 |
16 | ||
17 | /* | |
18 | * The maximum useful size of accesses for which we set up watchpoints is the | |
19 | * max range of slots we check on an access. | |
20 | */ | |
21 | #define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 + KCSAN_CHECK_ADJACENT)) | |
22 | ||
23 | /* | |
24 | * Number of bits we use to store size info. | |
25 | */ | |
26 | #define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCODABLE_SIZE) | |
27 | /* | |
28 | * This encoding for addresses discards the upper (1 for is-write + SIZE_BITS); | |
29 | * however, most 64-bit architectures do not use the full 64-bit address space. | |
30 | * Also, in order for a false positive to be observable 2 things need to happen: | |
31 | * | |
32 | * 1. different addresses but with the same encoded address race; | |
33 | * 2. and both map onto the same watchpoint slots; | |
34 | * | |
35 | * Both these are assumed to be very unlikely. However, in case it still happens | |
36 | * happens, the report logic will filter out the false positive (see report.c). | |
37 | */ | |
5cbaefe9 | 38 | #define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS) |
dfd402a4 ME |
39 | |
40 | /* | |
41 | * Masks to set/retrieve the encoded data. | |
42 | */ | |
5cbaefe9 | 43 | #define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1) |
dfd402a4 | 44 | #define WATCHPOINT_SIZE_MASK \ |
5cbaefe9 | 45 | GENMASK(BITS_PER_LONG-2, BITS_PER_LONG-2 - WATCHPOINT_SIZE_BITS) |
dfd402a4 | 46 | #define WATCHPOINT_ADDR_MASK \ |
5cbaefe9 | 47 | GENMASK(BITS_PER_LONG-3 - WATCHPOINT_SIZE_BITS, 0) |
dfd402a4 ME |
48 | |
49 | static inline bool check_encodable(unsigned long addr, size_t size) | |
50 | { | |
51 | return size <= MAX_ENCODABLE_SIZE; | |
52 | } | |
53 | ||
5cbaefe9 IM |
54 | static inline long |
55 | encode_watchpoint(unsigned long addr, size_t size, bool is_write) | |
dfd402a4 ME |
56 | { |
57 | return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) | | |
58 | (size << WATCHPOINT_ADDR_BITS) | | |
59 | (addr & WATCHPOINT_ADDR_MASK)); | |
60 | } | |
61 | ||
5c361425 ME |
62 | static __always_inline bool decode_watchpoint(long watchpoint, |
63 | unsigned long *addr_masked, | |
64 | size_t *size, | |
65 | bool *is_write) | |
dfd402a4 ME |
66 | { |
67 | if (watchpoint == INVALID_WATCHPOINT || | |
68 | watchpoint == CONSUMED_WATCHPOINT) | |
69 | return false; | |
70 | ||
5cbaefe9 IM |
71 | *addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK; |
72 | *size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >> WATCHPOINT_ADDR_BITS; | |
73 | *is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK); | |
dfd402a4 ME |
74 | |
75 | return true; | |
76 | } | |
77 | ||
78 | /* | |
79 | * Return watchpoint slot for an address. | |
80 | */ | |
5c361425 | 81 | static __always_inline int watchpoint_slot(unsigned long addr) |
dfd402a4 ME |
82 | { |
83 | return (addr / PAGE_SIZE) % CONFIG_KCSAN_NUM_WATCHPOINTS; | |
84 | } | |
85 | ||
5c361425 ME |
86 | static __always_inline bool matching_access(unsigned long addr1, size_t size1, |
87 | unsigned long addr2, size_t size2) | |
dfd402a4 ME |
88 | { |
89 | unsigned long end_range1 = addr1 + size1 - 1; | |
90 | unsigned long end_range2 = addr2 + size2 - 1; | |
91 | ||
92 | return addr1 <= end_range2 && addr2 <= end_range1; | |
93 | } | |
94 | ||
95 | #endif /* _KERNEL_KCSAN_ENCODING_H */ |