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cpu cycles: on arm64 use clock_gettime and PMCCNTR_EL0 for freestanding #238

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cpu cycles: on arm64 use clock_gettime and PMCCNTR_EL0 for freestanding #238

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15 changes: 12 additions & 3 deletions src/native/entropy_cpu_stubs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -111,14 +111,23 @@ static inline uint32_t read_virtual_count (void)
#endif /* arm */

#if defined (__aarch64__)
#define isb() __asm__ __volatile__("isb" : : : "memory")
#if defined(__ocaml_freestanding__) || defined(__ocaml_solo5__)
static inline uint64_t read_virtual_count(void)
{
uint64_t c;
isb();
__asm__ __volatile__("mrs %0, cntvct_el0":"=r"(c));
__asm__ __volatile__("mrs %0, PMCCNTR_EL0":"=r"(c));
return c;
}
#else
/* see https://github.com/mirage/mirage-crypto/issues/216 */
#include <time.h>
static inline uint64_t read_virtual_count (void)
{
struct timespec now;
clock_gettime (CLOCK_MONOTONIC, &now);
return now.tv_nsec;
}
#endif /* __ocaml_freestanding__ || __ocaml_solo5__ */
#endif /* aarch64 */

#if defined (__powerpc64__)
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