118 lines
4.0 KiB
C
118 lines
4.0 KiB
C
/* tnum: tracked (or tristate) numbers
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*
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* A tnum tracks knowledge about the bits of a value. Each bit can be either
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* known (0 or 1), or unknown (x). Arithmetic operations on tnums will
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* propagate the unknown bits such that the tnum result represents all the
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* possible results for possible values of the operands.
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*/
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#ifndef _LINUX_TNUM_H
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#define _LINUX_TNUM_H
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#include <linux/types.h>
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struct tnum {
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u64 value;
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u64 mask;
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};
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/* Constructors */
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/* Represent a known constant as a tnum. */
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struct tnum tnum_const(u64 value);
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/* A completely unknown value */
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extern const struct tnum tnum_unknown;
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/* An unknown value that is a superset of @min <= value <= @max.
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*
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* Could include values outside the range of [@min, @max].
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* For example tnum_range(0, 2) is represented by {0, 1, 2, *3*},
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* rather than the intended set of {0, 1, 2}.
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*/
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struct tnum tnum_range(u64 min, u64 max);
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/* Arithmetic and logical ops */
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/* Shift a tnum left (by a fixed shift) */
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struct tnum tnum_lshift(struct tnum a, u8 shift);
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/* Shift (rsh) a tnum right (by a fixed shift) */
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struct tnum tnum_rshift(struct tnum a, u8 shift);
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/* Shift (arsh) a tnum right (by a fixed min_shift) */
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struct tnum tnum_arshift(struct tnum a, u8 min_shift, u8 insn_bitness);
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/* Add two tnums, return @a + @b */
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struct tnum tnum_add(struct tnum a, struct tnum b);
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/* Subtract two tnums, return @a - @b */
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struct tnum tnum_sub(struct tnum a, struct tnum b);
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/* Bitwise-AND, return @a & @b */
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struct tnum tnum_and(struct tnum a, struct tnum b);
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/* Bitwise-OR, return @a | @b */
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struct tnum tnum_or(struct tnum a, struct tnum b);
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/* Bitwise-XOR, return @a ^ @b */
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struct tnum tnum_xor(struct tnum a, struct tnum b);
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/* Multiply two tnums, return @a * @b */
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struct tnum tnum_mul(struct tnum a, struct tnum b);
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/* Return a tnum representing numbers satisfying both @a and @b */
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struct tnum tnum_intersect(struct tnum a, struct tnum b);
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/* Return @a with all but the lowest @size bytes cleared */
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struct tnum tnum_cast(struct tnum a, u8 size);
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/* Returns true if @a is a known constant */
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static inline bool tnum_is_const(struct tnum a)
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{
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return !a.mask;
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}
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/* Returns true if @a == tnum_const(@b) */
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static inline bool tnum_equals_const(struct tnum a, u64 b)
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{
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return tnum_is_const(a) && a.value == b;
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}
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/* Returns true if @a is completely unknown */
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static inline bool tnum_is_unknown(struct tnum a)
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{
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return !~a.mask;
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}
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/* Returns true if @a is known to be a multiple of @size.
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* @size must be a power of two.
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*/
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bool tnum_is_aligned(struct tnum a, u64 size);
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/* Returns true if @b represents a subset of @a.
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*
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* Note that using tnum_range() as @a requires extra cautions as tnum_in() may
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* return true unexpectedly due to tnum limited ability to represent tight
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* range, e.g.
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*
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* tnum_in(tnum_range(0, 2), tnum_const(3)) == true
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*
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* As a rule of thumb, if @a is explicitly coded rather than coming from
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* reg->var_off, it should be in form of tnum_const(), tnum_range(0, 2**n - 1),
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* or tnum_range(2**n, 2**(n+1) - 1).
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*/
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bool tnum_in(struct tnum a, struct tnum b);
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/* Formatting functions. These have snprintf-like semantics: they will write
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* up to @size bytes (including the terminating NUL byte), and return the number
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* of bytes (excluding the terminating NUL) which would have been written had
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* sufficient space been available. (Thus tnum_sbin always returns 64.)
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*/
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/* Format a tnum as a pair of hex numbers (value; mask) */
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int tnum_strn(char *str, size_t size, struct tnum a);
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/* Format a tnum as tristate binary expansion */
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int tnum_sbin(char *str, size_t size, struct tnum a);
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/* Returns the 32-bit subreg */
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struct tnum tnum_subreg(struct tnum a);
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/* Returns the tnum with the lower 32-bit subreg cleared */
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struct tnum tnum_clear_subreg(struct tnum a);
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/* Returns the tnum with the lower 32-bit subreg set to value */
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struct tnum tnum_const_subreg(struct tnum a, u32 value);
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/* Returns true if 32-bit subreg @a is a known constant*/
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static inline bool tnum_subreg_is_const(struct tnum a)
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{
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return !(tnum_subreg(a)).mask;
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}
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#endif /* _LINUX_TNUM_H */
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