posix: Add posix CLOCK_THREAD_CPUTIME_ID support

Add posix 'CLOCK_THREAD_CPUTIME_ID' support to measure the
total CPU execution time of the current thread.

Signed-off-by: James Roy <rruuaanng@outlook.com>

Author: rruuaanng

lib/posix/options/Kconfig.timer

@@ -17,6 +17,8 @@ if POSIX_TIMERS
 
 config POSIX_THREAD_CPUTIME
 	bool "POSIX per-thread CPU-time clocks"
+	select THREAD_RUNTIME_STATS
+	select SCHED_THREAD_USAGE_ANALYSIS
 	help
 	  This enables CLOCK_THREAD_CPUTIME_ID.
 

lib/posix/options/clock.c

@@ -27,6 +27,59 @@ int clock_gettime(clockid_t clock_id, struct timespec *ts)
 	return 0;
 }
 
+#ifdef CONFIG_USERSPACE
+int z_vrfy___posix_clock_get_base(clockid_t clock_id, struct timespec *ts)
+{
+	K_OOPS(K_SYSCALL_MEMORY_WRITE(ts, sizeof(*ts)));
+	return z_impl___posix_clock_get_base(clock_id, ts);
+}
+#include <zephyr/syscalls/__posix_clock_get_base_mrsh.c>
+#endif
+
+int clock_gettime(clockid_t clock_id, struct timespec *ts)
+{
+	struct timespec base;
+
+	switch (clock_id) {
+	case CLOCK_MONOTONIC:
+		base.tv_sec = 0;
+		base.tv_nsec = 0;
+		break;
+
+	case CLOCK_REALTIME:
+		(void)__posix_clock_get_base(clock_id, &base);
+		break;
+
+#ifdef CONFIG_POSIX_THREAD_CPUTIME
+	case CLOCK_THREAD_CPUTIME_ID:
+		(void)__posix_clock_get_base(clock_id, &base);
+		*ts = base;
+		return 0;
+#endif /* CONFIG_POSIX_THREAD_CPUTIME */
+
+	default:
+		errno = EINVAL;
+		return -1;
+	}
+
+	uint64_t ticks = k_uptime_ticks();
+	uint64_t elapsed_secs = ticks / CONFIG_SYS_CLOCK_TICKS_PER_SEC;
+	uint64_t nremainder = ticks - elapsed_secs * CONFIG_SYS_CLOCK_TICKS_PER_SEC;
+
+	ts->tv_sec = (time_t) elapsed_secs;
+	/* For ns 32 bit conversion can be used since its smaller than 1sec. */
+	ts->tv_nsec = (int32_t) k_ticks_to_ns_floor32(nremainder);
+
+	ts->tv_sec += base.tv_sec;
+	ts->tv_nsec += base.tv_nsec;
+	if (ts->tv_nsec >= NSEC_PER_SEC) {
+		ts->tv_sec++;
+		ts->tv_nsec -= NSEC_PER_SEC;
+	}
+
+	return 0;
+}
+
 int clock_getres(clockid_t clock_id, struct timespec *res)
 {
 	BUILD_ASSERT(CONFIG_SYS_CLOCK_TICKS_PER_SEC > 0 &&