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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 bts %1, %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 btr %1, %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 bts %2, %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 btr %2, %0\n\t"
- "sbb %1, %1\n\t"
- : "+m" ( *bytes ), "=r" ( old )
- : "Ir" ( bit ) );
- return old;
- }
-
- #endif /* _BITS_BITOPS_H */
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