Use monotonic clock where appropriate

Author: catamorphism

libc-bottom-half/clocks/clock.c

@@ -14,13 +14,13 @@ _Static_assert(
 
 #ifdef __wasilibc_use_wasip2
 // Snapshot of the monotonic clock at the start of the program.
-static wall_clock_datetime_t start;
+static monotonic_clock_instant_t start;
 
 // Use a priority of 10 to run fairly early in the implementation-reserved
 // constructor priority range.
 __attribute__((constructor(10)))
 static void init(void) {
-    wall_clock_now(&start);
+    start = monotonic_clock_now();
 }
 
 // Define the libc symbol as `__clock` so that we can reliably call it
@@ -30,11 +30,8 @@ clock_t __clock(void) {
     // an inherent concept of a process. Note that this means we'll incorrectly
     // include time from other processes, so this function is only declared by
     // the headers if `_WASI_EMULATED_PROCESS_CLOCKS` is defined.
-    wall_clock_datetime_t now;
-    wall_clock_now(&now);
-    now.seconds -= start.seconds;
-    now.nanoseconds -= start.nanoseconds;
-    return (now.seconds + (now.nanoseconds * NSEC_PER_SEC));
+    monotonic_clock_instant_t now = monotonic_clock_now();
+    return now - start;
 }
 #else
 

libc-bottom-half/cloudlibc/src/libc/time/clock_getres.c

@@ -16,9 +16,17 @@
 int clock_getres(clockid_t clock_id, struct timespec *res) {
 #ifdef __wasilibc_use_wasip2
   if (res != NULL) {
-    wall_clock_datetime_t time_result;
-    wall_clock_resolution(&time_result);
-    *res = timestamp_to_timespec(&time_result);
+    if (clock_id == CLOCK_REALTIME) {
+        wall_clock_datetime_t time_result;
+        wall_clock_resolution(&time_result);
+        *res = timestamp_to_timespec(&time_result);
+    } else if (clock_id == CLOCK_MONOTONIC) {
+        monotonic_clock_duration_t time_result = monotonic_clock_resolution();
+        *res = instant_to_timespec(time_result);
+    } else {
+        errno = EINVAL; // wasip2 only supports wall and monotonic clocks
+        return -1;
+    }
   }
 #else
   __wasi_timestamp_t ts;

libc-bottom-half/cloudlibc/src/libc/time/clock_gettime.c

@@ -26,8 +26,8 @@ int __clock_gettime(clockid_t clock_id, struct timespec *tp) {
     wall_clock_now(&time_result);
     *tp = timestamp_to_timespec(&time_result);
   } else {
-    errno = __WASI_ERRNO_BADF;
-    return -1;
+    errno = EINVAL;
+    return -1; // wasip2 only supports wall and monotonic clocks
   }
 #else
   __wasi_timestamp_t ts;