posix: implement clock_getcpuclockid function

Implements clock_getcpuclockid function

Fixes zephyrproject-rtos#59954

Signed-off-by: Jai Arora <infolinesoni@gmail.com>

include/zephyr/posix/time.h

@@ -69,6 +69,10 @@ extern "C" {
 #define CLOCK_REALTIME 1
 #endif
 
+#ifndef CLOCK_PROCESS_CPUTIME_ID
+#define CLOCK_PROCESS_CPUTIME_ID 2
+#endif
+
 #ifndef CLOCK_MONOTONIC
 #define CLOCK_MONOTONIC 4
 #endif
@@ -88,6 +92,7 @@ int clock_gettime(clockid_t clock_id, struct timespec *ts);
 __syscall int clock_gettime(clockid_t clock_id, struct timespec *ts);
 #endif /* CONFIG_ARCH_POSIX */
 int clock_settime(clockid_t clock_id, const struct timespec *ts);
+int clock_getcpuclockid(pid_t pid, clockid_t *clock_id);
 /* Timer APIs */
 int timer_create(clockid_t clockId, struct sigevent *evp, timer_t *timerid);
 int timer_delete(timer_t timerid);

lib/posix/clock.c

@@ -9,6 +9,7 @@
 #include <zephyr/posix/sys/time.h>
 #include <zephyr/internal/syscall_handler.h>
 #include <zephyr/spinlock.h>
+#include <zephyr/posix/unistd.h>
 
 /*
  * `k_uptime_get` returns a timestamp based on an always increasing
@@ -195,3 +196,24 @@ int gettimeofday(struct timeval *tv, void *tz)
 
 	return res;
 }
+
+/**
+ * @brief Get current real time.
+ *
+ * See IEEE 1003.1
+ */
+int clock_getcpuclockid(pid_t pid, clockid_t *clock_id)
+{
+	/* We don't allow any process ID but our own.  */
+	if (pid != 0 && pid != getpid()) {
+		return EPERM;
+	}
+
+#ifdef CLOCK_PROCESS_CPUTIME_ID
+	*clock_id = CLOCK_PROCESS_CPUTIME_ID;
+	return 0;
+#endif
+
+	/* We don't have a timer for that.  */
+	return ENOENT;
+}