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