xnu-3789.70.16.tar.gz

[apple/xnu.git] / libsyscall / wrappers / __commpage_gettimeofday.c

diff --git a/libsyscall/wrappers/__commpage_gettimeofday.c b/libsyscall/wrappers/__commpage_gettimeofday.c
index 0bc34b4ab6619c8b48f4d733634a8b9e2bb8d318..4967a2f8d375c04069bbea77d2b8522b408f94d0 100644 (file)
--- a/libsyscall/wrappers/__commpage_gettimeofday.c
+++ b/libsyscall/wrappers/__commpage_gettimeofday.c
@@ -21,3 +21,59 @@
  * @APPLE_LICENSE_HEADER_END@
  */
 
+#include <sys/time.h>
+#include <mach/mach_time.h>
+#include <machine/cpu_capabilities.h>
+
+int __commpage_gettimeofday(struct timeval *);
+
+__attribute__((visibility("hidden")))
+int __commpage_gettimeofday_internal(struct timeval *tp, uint64_t *tbr_out);
+
+#if   defined(__x86_64__) || defined(__i386__)
+
+// XXX: must be kept in sync with __commpage_gettimeofday.s
+int
+__commpage_gettimeofday_internal(struct timeval *tp, uint64_t *tbr_out)
+{
+       volatile uint32_t *gtod_generation_p = _COMM_PAGE_GTOD_GENERATION;
+       volatile uint64_t *gtod_sec_base_p = _COMM_PAGE_GTOD_SEC_BASE;
+       volatile uint64_t *gtod_ns_base_p = _COMM_PAGE_GTOD_NS_BASE;
+
+       uint64_t tbr, gen, tod_secs, tod_nsecs, elapsed;
+       while(1) {
+               gen = *gtod_generation_p;
+               tbr = mach_absolute_time();
+               tod_secs = *gtod_sec_base_p;
+               tod_nsecs = *gtod_ns_base_p;
+               uint64_t gen2 = *gtod_generation_p;
+               if(__builtin_expect(gen, gen2) == gen2)
+                       break;
+       }
+       if (gen == 0) return KERN_FAILURE;
+       elapsed = tbr - tod_nsecs;
+
+       unsigned long secs;
+       uint32_t nsec;
+#if defined(__x86_64__)
+       secs = elapsed/NSEC_PER_SEC;
+       nsec = elapsed % NSEC_PER_SEC;
+#elif defined(__i386__)
+       uint32_t secs1, secs2;
+       secs1 = elapsed >> 32;
+       secs2 = elapsed;
+       __asm__ (
+         "divl %4"
+         : "=a" (secs), "=d" (nsec)
+         : "0" (secs2), "1" (secs1), "rm" (NSEC_PER_SEC)
+       );
+#endif /* __i386 or __x86_64__ */
+       tp->tv_sec = tod_secs + secs;
+       tp->tv_usec = nsec / NSEC_PER_USEC;
+
+       if (tbr_out) *tbr_out = tbr;
+
+       return KERN_SUCCESS;
+}
+
+#endif