CasperSecurity
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MINMAX_H
#define _LINUX_MINMAX_H
#include <linux/build_bug.h>
#include <linux/compiler.h>
#include <linux/const.h>
#include <linux/types.h>
/*
* min()/max()/clamp() macros must accomplish several things:
*
* - Avoid multiple evaluations of the arguments (so side-effects like
* "x++" happen only once) when non-constant.
* - Perform signed v unsigned type-checking (to generate compile
* errors instead of nasty runtime surprises).
* - Unsigned char/short are always promoted to signed int and can be
* compared against signed or unsigned arguments.
* - Unsigned arguments can be compared against non-negative signed constants.
* - Comparison of a signed argument against an unsigned constant fails
* even if the constant is below __INT_MAX__ and could be cast to int.
*/
#define __typecheck(x, y) \
(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
/*
* __sign_use for integer expressions:
* bit #0 set if ok for unsigned comparisons
* bit #1 set if ok for signed comparisons
*
* In particular, statically non-negative signed integer expressions
* are ok for both.
*
* NOTE! Unsigned types smaller than 'int' are implicitly converted to 'int'
* in expressions, and are accepted for signed conversions for now.
* This is debatable.
*
* Note that 'x' is the original expression, and 'ux' is the unique variable
* that contains the value.
*
* We use 'ux' for pure type checking, and 'x' for when we need to look at the
* value (but without evaluating it for side effects!
* Careful to only ever evaluate it with sizeof() or __builtin_constant_p() etc).
*
* Pointers end up being checked by the normal C type rules at the actual
* comparison, and these expressions only need to be careful to not cause
* warnings for pointer use.
*/
#define __sign_use(ux) (is_signed_type(typeof(ux)) ? \
(2 + __is_nonneg(ux)) : (1 + 2 * (sizeof(ux) < 4)))
/*
* Check whether a signed value is always non-negative.
*
* A cast is needed to avoid any warnings from values that aren't signed
* integer types (in which case the result doesn't matter).
*
* On 64-bit any integer or pointer type can safely be cast to 'long long'.
* But on 32-bit we need to avoid warnings about casting pointers to integers
* of different sizes without truncating 64-bit values so 'long' or 'long long'
* must be used depending on the size of the value.
*
* This does not work for 128-bit signed integers since the cast would truncate
* them, but we do not use s128 types in the kernel (we do use 'u128',
* but they are handled by the !is_signed_type() case).
*/
#if __SIZEOF_POINTER__ == __SIZEOF_LONG_LONG__
#define __is_nonneg(ux) statically_true((long long)(ux) >= 0)
#else
#define __is_nonneg(ux) statically_true( \
(typeof(__builtin_choose_expr(sizeof(ux) > 4, 1LL, 1L)))(ux) >= 0)
#endif
#define __types_ok(ux, uy) \
(__sign_use(ux) & __sign_use(uy))
#define __types_ok3(ux, uy, uz) \
(__sign_use(ux) & __sign_use(uy) & __sign_use(uz))
#define __cmp_op_min <
#define __cmp_op_max >
#define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y))
#define __cmp_once_unique(op, type, x, y, ux, uy) \
({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
#define __cmp_once(op, type, x, y) \
__cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
#define __careful_cmp_once(op, x, y, ux, uy) ({ \
__auto_type ux = (x); __auto_type uy = (y); \
BUILD_BUG_ON_MSG(!__types_ok(ux, uy), \
#op"("#x", "#y") signedness error"); \
__cmp(op, ux, uy); })
#define __careful_cmp(op, x, y) \
__careful_cmp_once(op, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
/**
* min - return minimum of two values of the same or compatible types
* @x: first value
* @y: second value
*/
#define min(x, y) __careful_cmp(min, x, y)
/**
* max - return maximum of two values of the same or compatible types
* @x: first value
* @y: second value
*/
#define max(x, y) __careful_cmp(max, x, y)
/**
* umin - return minimum of two non-negative values
* Signed types are zero extended to match a larger unsigned type.
* @x: first value
* @y: second value
*/
#define umin(x, y) \
__careful_cmp(min, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull)
/**
* umax - return maximum of two non-negative values
* @x: first value
* @y: second value
*/
#define umax(x, y) \
__careful_cmp(max, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull)
#define __careful_op3(op, x, y, z, ux, uy, uz) ({ \
__auto_type ux = (x); __auto_type uy = (y);__auto_type uz = (z);\
BUILD_BUG_ON_MSG(!__types_ok3(ux, uy, uz), \
#op"3("#x", "#y", "#z") signedness error"); \
__cmp(op, ux, __cmp(op, uy, uz)); })
/**
* min3 - return minimum of three values
* @x: first value
* @y: second value
* @z: third value
*/
#define min3(x, y, z) \
__careful_op3(min, x, y, z, __UNIQUE_ID(x_), __UNIQUE_ID(y_), __UNIQUE_ID(z_))
/**
* max3 - return maximum of three values
* @x: first value
* @y: second value
* @z: third value
*/
#define max3(x, y, z) \
__careful_op3(max, x, y, z, __UNIQUE_ID(x_), __UNIQUE_ID(y_), __UNIQUE_ID(z_))
/**
* min_t - return minimum of two values, using the specified type
* @type: data type to use
* @x: first value
* @y: second value
*/
#define min_t(type, x, y) __cmp_once(min, type, x, y)
/**
* max_t - return maximum of two values, using the specified type
* @type: data type to use
* @x: first value
* @y: second value
*/
#define max_t(type, x, y) __cmp_once(max, type, x, y)
/**
* min_not_zero - return the minimum that is _not_ zero, unless both are zero
* @x: value1
* @y: value2
*/
#define min_not_zero(x, y) ({ \
typeof(x) __x = (x); \
typeof(y) __y = (y); \
__x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
#define __clamp(val, lo, hi) \
((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val)))
#define __clamp_once(type, val, lo, hi, uval, ulo, uhi) ({ \
type uval = (val); \
type ulo = (lo); \
type uhi = (hi); \
BUILD_BUG_ON_MSG(statically_true(ulo > uhi), \
"clamp() low limit " #lo " greater than high limit " #hi); \
BUILD_BUG_ON_MSG(!__types_ok3(uval, ulo, uhi), \
"clamp("#val", "#lo", "#hi") signedness error"); \
__clamp(uval, ulo, uhi); })
#define __careful_clamp(type, val, lo, hi) \
__clamp_once(type, val, lo, hi, __UNIQUE_ID(v_), __UNIQUE_ID(l_), __UNIQUE_ID(h_))
/**
* clamp - return a value clamped to a given range with typechecking
* @val: current value
* @lo: lowest allowable value
* @hi: highest allowable value
*
* This macro checks @val/@lo/@hi to make sure they have compatible
* signedness.
*/
#define clamp(val, lo, hi) __careful_clamp(__auto_type, val, lo, hi)
/**
* clamp_t - return a value clamped to a given range using a given type
* @type: the type of variable to use
* @val: current value
* @lo: minimum allowable value
* @hi: maximum allowable value
*
* This macro does no typechecking and uses temporary variables of type
* @type to make all the comparisons.
*/
#define clamp_t(type, val, lo, hi) __careful_clamp(type, val, lo, hi)
/**
* clamp_val - return a value clamped to a given range using val's type
* @val: current value
* @lo: minimum allowable value
* @hi: maximum allowable value
*
* This macro does no typechecking and uses temporary variables of whatever
* type the input argument @val is. This is useful when @val is an unsigned
* type and @lo and @hi are literals that will otherwise be assigned a signed
* integer type.
*/
#define clamp_val(val, lo, hi) __careful_clamp(typeof(val), val, lo, hi)
/*
* Do not check the array parameter using __must_be_array().
* In the following legit use-case where the "array" passed is a simple pointer,
* __must_be_array() will return a failure.
* --- 8< ---
* int *buff
* ...
* min = min_array(buff, nb_items);
* --- 8< ---
*
* The first typeof(&(array)[0]) is needed in order to support arrays of both
* 'int *buff' and 'int buff[N]' types.
*
* The array can be an array of const items.
* typeof() keeps the const qualifier. Use __unqual_scalar_typeof() in order
* to discard the const qualifier for the __element variable.
*/
#define __minmax_array(op, array, len) ({ \
typeof(&(array)[0]) __array = (array); \
typeof(len) __len = (len); \
__unqual_scalar_typeof(__array[0]) __element = __array[--__len];\
while (__len--) \
__element = op(__element, __array[__len]); \
__element; })
/**
* min_array - return minimum of values present in an array
* @array: array
* @len: array length
*
* Note that @len must not be zero (empty array).
*/
#define min_array(array, len) __minmax_array(min, array, len)
/**
* max_array - return maximum of values present in an array
* @array: array
* @len: array length
*
* Note that @len must not be zero (empty array).
*/
#define max_array(array, len) __minmax_array(max, array, len)
static inline bool in_range64(u64 val, u64 start, u64 len)
{
return (val - start) < len;
}
static inline bool in_range32(u32 val, u32 start, u32 len)
{
return (val - start) < len;
}
/**
* in_range - Determine if a value lies within a range.
* @val: Value to test.
* @start: First value in range.
* @len: Number of values in range.
*
* This is more efficient than "if (start <= val && val < (start + len))".
* It also gives a different answer if @start + @len overflows the size of
* the type by a sufficient amount to encompass @val. Decide for yourself
* which behaviour you want, or prove that start + len never overflow.
* Do not blindly replace one form with the other.
*/
#define in_range(val, start, len) \
((sizeof(start) | sizeof(len) | sizeof(val)) <= sizeof(u32) ? \
in_range32(val, start, len) : in_range64(val, start, len))
/**
* swap - swap values of @a and @b
* @a: first value
* @b: second value
*/
#define swap(a, b) \
do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
/*
* Use these carefully: no type checking, and uses the arguments
* multiple times. Use for obvious constants only.
*/
#define MIN(a, b) __cmp(min, a, b)
#define MAX(a, b) __cmp(max, a, b)
#define MIN_T(type, a, b) __cmp(min, (type)(a), (type)(b))
#define MAX_T(type, a, b) __cmp(max, (type)(a), (type)(b))
#endif /* _LINUX_MINMAX_H */