cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

word-at-a-time.h (2817B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2#ifndef _ASM_WORD_AT_A_TIME_H
      3#define _ASM_WORD_AT_A_TIME_H
      4
      5#include <linux/kernel.h>
      6#include <asm/byteorder.h>
      7
      8#ifdef __BIG_ENDIAN
      9
     10struct word_at_a_time {
     11	const unsigned long high_bits, low_bits;
     12};
     13
     14#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
     15
     16/* Bit set in the bytes that have a zero */
     17static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
     18{
     19	unsigned long mask = (val & c->low_bits) + c->low_bits;
     20	return ~(mask | rhs);
     21}
     22
     23#define create_zero_mask(mask) (mask)
     24
     25static inline long find_zero(unsigned long mask)
     26{
     27	long byte = 0;
     28#ifdef CONFIG_64BIT
     29	if (mask >> 32)
     30		mask >>= 32;
     31	else
     32		byte = 4;
     33#endif
     34	if (mask >> 16)
     35		mask >>= 16;
     36	else
     37		byte += 2;
     38	return (mask >> 8) ? byte : byte + 1;
     39}
     40
     41static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
     42{
     43	unsigned long rhs = val | c->low_bits;
     44	*data = rhs;
     45	return (val + c->high_bits) & ~rhs;
     46}
     47
     48#ifndef zero_bytemask
     49#define zero_bytemask(mask) (~1ul << __fls(mask))
     50#endif
     51
     52#else
     53
     54/*
     55 * The optimal byte mask counting is probably going to be something
     56 * that is architecture-specific. If you have a reliably fast
     57 * bit count instruction, that might be better than the multiply
     58 * and shift, for example.
     59 */
     60struct word_at_a_time {
     61	const unsigned long one_bits, high_bits;
     62};
     63
     64#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
     65
     66#ifdef CONFIG_64BIT
     67
     68/*
     69 * Jan Achrenius on G+: microoptimized version of
     70 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
     71 * that works for the bytemasks without having to
     72 * mask them first.
     73 */
     74static inline long count_masked_bytes(unsigned long mask)
     75{
     76	return mask*0x0001020304050608ul >> 56;
     77}
     78
     79#else	/* 32-bit case */
     80
     81/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
     82static inline long count_masked_bytes(long mask)
     83{
     84	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
     85	long a = (0x0ff0001+mask) >> 23;
     86	/* Fix the 1 for 00 case */
     87	return a & mask;
     88}
     89
     90#endif
     91
     92/* Return nonzero if it has a zero */
     93static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
     94{
     95	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
     96	*bits = mask;
     97	return mask;
     98}
     99
    100static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
    101{
    102	return bits;
    103}
    104
    105static inline unsigned long create_zero_mask(unsigned long bits)
    106{
    107	bits = (bits - 1) & ~bits;
    108	return bits >> 7;
    109}
    110
    111/* The mask we created is directly usable as a bytemask */
    112#define zero_bytemask(mask) (mask)
    113
    114static inline unsigned long find_zero(unsigned long mask)
    115{
    116	return count_masked_bytes(mask);
    117}
    118
    119#endif /* __BIG_ENDIAN */
    120
    121#endif /* _ASM_WORD_AT_A_TIME_H */