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#ifndef _BITS_BITOPS_H
#define _BITS_BITOPS_H
/** @file
*
* x86 bit operations
*
* We perform atomic bit set and bit clear operations using "lock bts"
* and "lock btr". We use the output constraint to inform the
* compiler that any memory from the start of the bit field up to and
* including the byte containing the bit may be modified. (This is
* overkill but shouldn't matter in practice since we're unlikely to
* subsequently read other bits from the same bit field.)
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <stdint.h>
/**
* Set bit atomically
*
* @v bit Bit to set
* @v bits Bit field
*/
static inline __attribute__ (( always_inline )) void
set_bit ( unsigned int bit, volatile void *bits ) {
volatile struct {
uint8_t byte[ ( bit / 8 ) + 1 ];
} *bytes = bits;
__asm__ __volatile__ ( "lock btsl %k1, %0"
: "+m" ( *bytes ) : "Ir" ( bit ) );
}
/**
* Clear bit atomically
*
* @v bit Bit to set
* @v bits Bit field
*/
static inline __attribute__ (( always_inline )) void
clear_bit ( unsigned int bit, volatile void *bits ) {
volatile struct {
uint8_t byte[ ( bit / 8 ) + 1 ];
} *bytes = bits;
__asm__ __volatile__ ( "lock btrl %k1, %0"
: "+m" ( *bytes ) : "Ir" ( bit ) );
}
/**
* Test and set bit atomically
*
* @v bit Bit to set
* @v bits Bit field
* @ret old Old value of bit (zero or non-zero)
*/
static inline __attribute__ (( always_inline )) int
test_and_set_bit ( unsigned int bit, volatile void *bits ) {
volatile struct {
uint8_t byte[ ( bit / 8 ) + 1 ];
} *bytes = bits;
int old;
__asm__ __volatile__ ( "lock btsl %k2, %0\n\t"
"sbb %1, %1\n\t"
: "+m" ( *bytes ), "=r" ( old )
: "Ir" ( bit ) );
return old;
}
/**
* Test and clear bit atomically
*
* @v bit Bit to set
* @v bits Bit field
* @ret old Old value of bit (zero or non-zero)
*/
static inline __attribute__ (( always_inline )) int
test_and_clear_bit ( unsigned int bit, volatile void *bits ) {
volatile struct {
uint8_t byte[ ( bit / 8 ) + 1 ];
} *bytes = bits;
int old;
__asm__ __volatile__ ( "lock btrl %k2, %0\n\t"
"sbb %1, %1\n\t"
: "+m" ( *bytes ), "=r" ( old )
: "Ir" ( bit ) );
return old;
}
#endif /* _BITS_BITOPS_H */
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