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- /* SPDX-License-Identifier: GPL-2.0 */
- #ifndef _KERNEL_KCSAN_ENCODING_H
- #define _KERNEL_KCSAN_ENCODING_H
- #include <linux/bits.h>
- #include <linux/log2.h>
- #include <linux/mm.h>
- #include "kcsan.h"
- #define SLOT_RANGE PAGE_SIZE
- #define INVALID_WATCHPOINT 0
- #define CONSUMED_WATCHPOINT 1
- /*
- * The maximum useful size of accesses for which we set up watchpoints is the
- * max range of slots we check on an access.
- */
- #define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 + KCSAN_CHECK_ADJACENT))
- /*
- * Number of bits we use to store size info.
- */
- #define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCODABLE_SIZE)
- /*
- * This encoding for addresses discards the upper (1 for is-write + SIZE_BITS);
- * however, most 64-bit architectures do not use the full 64-bit address space.
- * Also, in order for a false positive to be observable 2 things need to happen:
- *
- * 1. different addresses but with the same encoded address race;
- * 2. and both map onto the same watchpoint slots;
- *
- * Both these are assumed to be very unlikely. However, in case it still
- * happens, the report logic will filter out the false positive (see report.c).
- */
- #define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS)
- /*
- * Masks to set/retrieve the encoded data.
- */
- #define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
- #define WATCHPOINT_SIZE_MASK \
- GENMASK(BITS_PER_LONG-2, BITS_PER_LONG-2 - WATCHPOINT_SIZE_BITS)
- #define WATCHPOINT_ADDR_MASK \
- GENMASK(BITS_PER_LONG-3 - WATCHPOINT_SIZE_BITS, 0)
- static inline bool check_encodable(unsigned long addr, size_t size)
- {
- return size <= MAX_ENCODABLE_SIZE;
- }
- static inline long
- encode_watchpoint(unsigned long addr, size_t size, bool is_write)
- {
- return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) |
- (size << WATCHPOINT_ADDR_BITS) |
- (addr & WATCHPOINT_ADDR_MASK));
- }
- static __always_inline bool decode_watchpoint(long watchpoint,
- unsigned long *addr_masked,
- size_t *size,
- bool *is_write)
- {
- if (watchpoint == INVALID_WATCHPOINT ||
- watchpoint == CONSUMED_WATCHPOINT)
- return false;
- *addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK;
- *size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >> WATCHPOINT_ADDR_BITS;
- *is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK);
- return true;
- }
- /*
- * Return watchpoint slot for an address.
- */
- static __always_inline int watchpoint_slot(unsigned long addr)
- {
- return (addr / PAGE_SIZE) % CONFIG_KCSAN_NUM_WATCHPOINTS;
- }
- static __always_inline bool matching_access(unsigned long addr1, size_t size1,
- unsigned long addr2, size_t size2)
- {
- unsigned long end_range1 = addr1 + size1 - 1;
- unsigned long end_range2 = addr2 + size2 - 1;
- return addr1 <= end_range2 && addr2 <= end_range1;
- }
- #endif /* _KERNEL_KCSAN_ENCODING_H */
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