src: fix calculation of fuzzing time in statistics

When the computer is suspended during a fuzzing session,
the time spent in suspended state is counted as a "run time"
on a statistics screen.

The time returned by `gettimeofday(2)` is affected by discontinuous
jumps in the system time. It is better using `clock_gettime(2)`.

The patch replace `gettimeofday` with `clock_gettime` [1].
`clock_gettime` uses a CLOCK_MONOTONIC_COARSE clock type,
it is faster than CLOCK_MONOTONIC, but still has resolution (~1ms)
that is adequate for our purposes. However, CLOCK_MONOTONIC_COARSE
is a Linux-specific clock variant, so on macOS it is replaced
with CLOCK_MONOTONIC, and with CLOCK_MONOTONIC_FAST on FreeBSD [2].

Closes #1241

1. https://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_gettime.html
2. https://man.freebsd.org/cgi/man.cgi?query=clock_gettime

src/afl-common.c

@@ -34,6 +34,7 @@
 #endif
 #include <string.h>
 #include <strings.h>
+#include <time.h>
 #include <math.h>
 #include <sys/mman.h>
 
@@ -58,6 +59,26 @@ u8  last_intr = 0;
   #define AFL_PATH "/usr/local/lib/afl/"
 #endif
 
+/* - Some BSD (i.e.: FreeBSD) offer the FAST clock source as
+ *   equivalent to Linux COARSE clock source. Aliasing COARSE to
+ *   FAST on such systems when COARSE is not already defined.
+ * - macOS has no support of CLOCK_MONOTONIC_COARSE clock type.
+ */
+#if defined (OS_DARWIN) || defined (OS_SUNOS)
+#    define CLOCK_MONOTONIC_COARSE CLOCK_MONOTONIC
+#elif defined (OS_FREEBSD)
+#    define CLOCK_MONOTONIC_COARSE CLOCK_MONOTONIC_FAST
+#endif
+
+/* Convert seconds to milliseconds. */
+#define SEC_TO_MS(sec) ((sec)*1000)
+/* Convert seconds to microseconds. */
+#define SEC_TO_US(sec) ((sec)*1000000)
+/* Convert nanoseconds to milliseconds. */
+#define NS_TO_MS(ns)   ((ns)/1000000)
+/* Convert nanoseconds to microseconds. */
+#define NS_TO_US(ns)   ((ns)/1000)
+
 void *afl_memmem(const void *haystack, size_t haystacklen, const void *needle,
                  size_t needlelen) {
 
@@ -973,27 +994,27 @@ void read_bitmap(u8 *fname, u8 *map, size_t len) {
 /* Get unix time in milliseconds */
 
 inline u64 get_cur_time(void) {
+  struct timespec ts;
+  int rc = clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
+  if (rc == -1) {
+    PFATAL("Failed to obtain timestamp (errno = %i: %s)\n",
+           errno, strerror(errno));
+  }
 
-  struct timeval  tv;
+  return SEC_TO_MS((uint64_t)ts.tv_sec) + NS_TO_MS((uint64_t)ts.tv_nsec);
-  struct timezone tz;
-
-  gettimeofday(&tv, &tz);
-
-  return (tv.tv_sec * 1000ULL) + (tv.tv_usec / 1000);
-
 }
 
 /* Get unix time in microseconds */
 
 u64 get_cur_time_us(void) {
+  struct timespec ts;
+  int rc = clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
+  if (rc == -1) {
+    PFATAL("Failed to obtain timestamp (errno = %i: %s)\n",
+           errno, strerror(errno));
+  }
 
-  struct timeval  tv;
+  return SEC_TO_US((uint64_t)ts.tv_sec) + NS_TO_US((uint64_t)ts.tv_nsec);
-  struct timezone tz;
-
-  gettimeofday(&tv, &tz);
-
-  return (tv.tv_sec * 1000000ULL) + tv.tv_usec;
-
 }
 
 /* Describe integer. The buf should be