1 /* SPDX-License-Identifier: GPL-2.0 */
3 #ifndef _KERNEL_KCSAN_ENCODING_H
4 #define _KERNEL_KCSAN_ENCODING_H
6 #include <linux/bits.h>
7 #include <linux/log2.h>
12 #define SLOT_RANGE PAGE_SIZE
14 #define INVALID_WATCHPOINT 0
15 #define CONSUMED_WATCHPOINT 1
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.
21 #define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 + KCSAN_CHECK_ADJACENT))
24 * Number of bits we use to store size info.
26 #define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCODABLE_SIZE)
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:
32 * 1. different addresses but with the same encoded address race;
33 * 2. and both map onto the same watchpoint slots;
35 * Both these are assumed to be very unlikely. However, in case it still
36 * happens, the report logic will filter out the false positive (see report.c).
38 #define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS)
41 * Masks to set/retrieve the encoded data.
43 #define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
44 #define WATCHPOINT_SIZE_MASK \
45 GENMASK(BITS_PER_LONG-2, BITS_PER_LONG-2 - WATCHPOINT_SIZE_BITS)
46 #define WATCHPOINT_ADDR_MASK \
47 GENMASK(BITS_PER_LONG-3 - WATCHPOINT_SIZE_BITS, 0)
49 static inline bool check_encodable(unsigned long addr, size_t size)
51 return size <= MAX_ENCODABLE_SIZE;
55 encode_watchpoint(unsigned long addr, size_t size, bool is_write)
57 return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) |
58 (size << WATCHPOINT_ADDR_BITS) |
59 (addr & WATCHPOINT_ADDR_MASK));
62 static __always_inline bool decode_watchpoint(long watchpoint,
63 unsigned long *addr_masked,
67 if (watchpoint == INVALID_WATCHPOINT ||
68 watchpoint == CONSUMED_WATCHPOINT)
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);
79 * Return watchpoint slot for an address.
81 static __always_inline int watchpoint_slot(unsigned long addr)
83 return (addr / PAGE_SIZE) % CONFIG_KCSAN_NUM_WATCHPOINTS;
86 static __always_inline bool matching_access(unsigned long addr1, size_t size1,
87 unsigned long addr2, size_t size2)
89 unsigned long end_range1 = addr1 + size1 - 1;
90 unsigned long end_range2 = addr2 + size2 - 1;
92 return addr1 <= end_range2 && addr2 <= end_range1;
95 #endif /* _KERNEL_KCSAN_ENCODING_H */