1/* tnum: tracked (or tristate) numbers 2 * 3 * A tnum tracks knowledge about the bits of a value. Each bit can be either 4 * known (0 or 1), or unknown (x). Arithmetic operations on tnums will 5 * propagate the unknown bits such that the tnum result represents all the 6 * possible results for possible values of the operands. 7 */ 8 9#ifndef _LINUX_TNUM_H 10#define _LINUX_TNUM_H 11 12#include <linux/types.h> 13 14struct tnum { 15 u64 value; 16 u64 mask; 17}; 18 19/* Constructors */ 20/* Represent a known constant as a tnum. */ 21struct tnum tnum_const(u64 value); 22/* A completely unknown value */ 23extern const struct tnum tnum_unknown; 24/* An unknown value that is a superset of @min <= value <= @max. 25 * 26 * Could include values outside the range of [@min, @max]. 27 * For example tnum_range(0, 2) is represented by {0, 1, 2, *3*}, 28 * rather than the intended set of {0, 1, 2}. 29 */ 30struct tnum tnum_range(u64 min, u64 max); 31 32/* Arithmetic and logical ops */ 33/* Shift a tnum left (by a fixed shift) */ 34struct tnum tnum_lshift(struct tnum a, u8 shift); 35/* Shift (rsh) a tnum right (by a fixed shift) */ 36struct tnum tnum_rshift(struct tnum a, u8 shift); 37/* Shift (arsh) a tnum right (by a fixed min_shift) */ 38struct tnum tnum_arshift(struct tnum a, u8 min_shift, u8 insn_bitness); 39/* Add two tnums, return @a + @b */ 40struct tnum tnum_add(struct tnum a, struct tnum b); 41/* Subtract two tnums, return @a - @b */ 42struct tnum tnum_sub(struct tnum a, struct tnum b); 43/* Bitwise-AND, return @a & @b */ 44struct tnum tnum_and(struct tnum a, struct tnum b); 45/* Bitwise-OR, return @a | @b */ 46struct tnum tnum_or(struct tnum a, struct tnum b); 47/* Bitwise-XOR, return @a ^ @b */ 48struct tnum tnum_xor(struct tnum a, struct tnum b); 49/* Multiply two tnums, return @a * @b */ 50struct tnum tnum_mul(struct tnum a, struct tnum b); 51 52/* Return a tnum representing numbers satisfying both @a and @b */ 53struct tnum tnum_intersect(struct tnum a, struct tnum b); 54 55/* Return @a with all but the lowest @size bytes cleared */ 56struct tnum tnum_cast(struct tnum a, u8 size); 57 58/* Returns true if @a is a known constant */ 59static inline bool tnum_is_const(struct tnum a) 60{ 61 return !a.mask; 62} 63 64/* Returns true if @a == tnum_const(@b) */ 65static inline bool tnum_equals_const(struct tnum a, u64 b) 66{ 67 return tnum_is_const(a) && a.value == b; 68} 69 70/* Returns true if @a is completely unknown */ 71static inline bool tnum_is_unknown(struct tnum a) 72{ 73 return !~a.mask; 74} 75 76/* Returns true if @a is known to be a multiple of @size. 77 * @size must be a power of two. 78 */ 79bool tnum_is_aligned(struct tnum a, u64 size); 80 81/* Returns true if @b represents a subset of @a. 82 * 83 * Note that using tnum_range() as @a requires extra cautions as tnum_in() may 84 * return true unexpectedly due to tnum limited ability to represent tight 85 * range, e.g. 86 * 87 * tnum_in(tnum_range(0, 2), tnum_const(3)) == true 88 * 89 * As a rule of thumb, if @a is explicitly coded rather than coming from 90 * reg->var_off, it should be in form of tnum_const(), tnum_range(0, 2**n - 1), 91 * or tnum_range(2**n, 2**(n+1) - 1). 92 */ 93bool tnum_in(struct tnum a, struct tnum b); 94 95/* Formatting functions. These have snprintf-like semantics: they will write 96 * up to @size bytes (including the terminating NUL byte), and return the number 97 * of bytes (excluding the terminating NUL) which would have been written had 98 * sufficient space been available. (Thus tnum_sbin always returns 64.) 99 */ 100/* Format a tnum as a pair of hex numbers (value; mask) */ 101int tnum_strn(char *str, size_t size, struct tnum a); 102/* Format a tnum as tristate binary expansion */ 103int tnum_sbin(char *str, size_t size, struct tnum a); 104 105/* Returns the 32-bit subreg */ 106struct tnum tnum_subreg(struct tnum a); 107/* Returns the tnum with the lower 32-bit subreg cleared */ 108struct tnum tnum_clear_subreg(struct tnum a); 109/* Returns the tnum with the lower 32-bit subreg in *reg* set to the lower 110 * 32-bit subreg in *subreg* 111 */ 112struct tnum tnum_with_subreg(struct tnum reg, struct tnum subreg); 113/* Returns the tnum with the lower 32-bit subreg set to value */ 114struct tnum tnum_const_subreg(struct tnum a, u32 value); 115/* Returns true if 32-bit subreg @a is a known constant*/ 116static inline bool tnum_subreg_is_const(struct tnum a) 117{ 118 return !(tnum_subreg(a)).mask; 119} 120 121#endif /* _LINUX_TNUM_H */ 122