diff options
Diffstat (limited to 'gpxe/src/arch/i386/include/gpxe/rdtsc_timer.h')
-rw-r--r-- | gpxe/src/arch/i386/include/gpxe/rdtsc_timer.h | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/gpxe/src/arch/i386/include/gpxe/rdtsc_timer.h b/gpxe/src/arch/i386/include/gpxe/rdtsc_timer.h new file mode 100644 index 00000000..0e03d707 --- /dev/null +++ b/gpxe/src/arch/i386/include/gpxe/rdtsc_timer.h @@ -0,0 +1,37 @@ +#ifndef _GPXE_RDTSC_TIMER_H +#define _GPXE_RDTSC_TIMER_H + +/** @file + * + * RDTSC timer + * + */ + +#ifdef TIMER_RDTSC +#define TIMER_PREFIX_rdtsc +#else +#define TIMER_PREFIX_rdtsc __rdtsc_ +#endif + +/** + * RDTSC values can easily overflow an unsigned long. We discard the + * low-order bits in order to obtain sensibly-scaled values. + */ +#define TSC_SHIFT 8 + +/** + * Get current system time in ticks + * + * @ret ticks Current time, in ticks + */ +static inline __always_inline unsigned long +TIMER_INLINE ( rdtsc, currticks ) ( void ) { + unsigned long ticks; + + __asm__ __volatile__ ( "rdtsc\n\t" + "shrdl %1, %%edx, %%eax\n\t" + : "=a" ( ticks ) : "i" ( TSC_SHIFT ) : "edx" ); + return ticks; +} + +#endif /* _GPXE_RDTSC_TIMER_H */ |