kernel: implement _sys_time()

After some consideration this seems like the most fitting way to handle
timekeeping. Directly, the syscall is only useful for keeping time within a
single process, but it is meant to be used for e.g. NTP clients, which will
provide the real time through the VFS.

5 files changed, 42 insertions, 0 deletions

diff --git a/src/cmd/tests/kernel/miscsyscall.c b/src/cmd/tests/kernel/miscsyscall.c
index 7c61392..3cf3f2e 100644
--- a/src/cmd/tests/kernel/miscsyscall.c
+++ b/src/cmd/tests/kernel/miscsyscall.c
@@ -287,6 +287,23 @@ static void test_badopen(void) {
 	test(_sys_open(TMPFILEPATH, strlen(TMPFILEPATH), OPEN_CREATE) == -EINVAL);
 }
 
+static void test_timer(void) {
+	uint64_t start = _sys_time(0);
+	test(start == 0);
+	_sys_sleep(10);
+	uint64_t delay = _sys_time(0) - start;
+	test(delay >= 10 * 1000000);
+	if (!fork()) {
+		uint64_t start = _sys_time(0);
+		test(start == 0);
+		_sys_sleep(10);
+		uint64_t delay = _sys_time(0) - start;
+		test(delay >= 10 * 1000000);
+	} else {
+		_sys_await();
+	}
+}
+
 void r_k_miscsyscall(void) {
 	run_test(test_await);
 	run_test(test_await2);
@@ -297,4 +314,5 @@ void r_k_miscsyscall(void) {
 	run_test(test_execbuf);
 	run_test(test_sleep);
 	run_test(test_badopen);
+	run_test(test_timer);
 }
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index bfe5cfc..5d95b52 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -98,6 +98,9 @@ struct Proc {
 		size_t len;
 		size_t pos;
 	} execbuf;
+
+	/* Time of the first _sys_time() call. 0 if not called yet. */
+	uint64_t basetime;
 };
 
 extern Proc *proc_cur;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index a2e0e27..3350796 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -418,6 +418,18 @@ hid_t _sys_getprocfs(int flags) {
 	SYSCALL_RETURN(hid);
 }
 
+uint64_t _sys_time(int flags) {
+	if (flags != 0) {
+		SYSCALL_RETURN(-ENOSYS);
+	}
+
+	uint64_t now = uptime_ns();
+	if (proc_cur->basetime == 0) {
+		proc_cur->basetime = now;
+	}
+	SYSCALL_RETURN(now - proc_cur->basetime);
+}
+
 long _sys_execbuf(void __user *ubuf, size_t len) {
 	if (len == 0) SYSCALL_RETURN(0);
 	if (len > EXECBUF_MAX_LEN)
@@ -473,6 +485,7 @@ long _syscall(long num, long a, long b, long c, long d, long e) {
 		break; case _SYS_GETPPID:	_sys_getppid();
 		break; case _SYS_WAIT2:	_sys_wait2(a, b, (userptr_t)c);
 		break; case _SYS_GETPROCFS:	_sys_getprocfs(a);
+		break; case _SYS_TIME:	_sys_time(a);
 		break; case _SYS_EXECBUF:	_sys_execbuf((userptr_t)a, b);
 		break; case _SYS_DEBUG_KLOG:	_sys_debug_klog((userptr_t)a, b);
 		break;
diff --git a/src/libc/syscall.c b/src/libc/syscall.c
index 706aec6..4cdbe6c 100644
--- a/src/libc/syscall.c
+++ b/src/libc/syscall.c
@@ -94,6 +94,10 @@ hid_t _sys_getprocfs(int flags) {
 	return (hid_t)_syscall(_SYS_GETPROCFS, (long)flags, 0, 0, 0, 0);
 }
 
+uint64_t _sys_time(int flags) {
+	return (uint64_t)_syscall(_SYS_TIME, (long)flags, 0, 0, 0, 0);
+}
+
 long _sys_execbuf(void __user *buf, size_t len) {
 	return _syscall(_SYS_EXECBUF, (long)buf, (long)len, 0, 0, 0);
 }
diff --git a/src/libk/include/camellia/syscalls.h b/src/libk/include/camellia/syscalls.h
index 58898d4..d27ae0c 100644
--- a/src/libk/include/camellia/syscalls.h
+++ b/src/libk/include/camellia/syscalls.h
@@ -22,6 +22,7 @@
 #define _SYS_GETPPID 20
 #define _SYS_WAIT2 21
 #define _SYS_GETPROCFS 22
+#define _SYS_TIME 23
 
 #define _SYS_EXECBUF 100
 #define _SYS_DEBUG_KLOG 101
@@ -84,6 +85,9 @@ int _sys_wait2(int pid, int flags, struct sys_wait2 __user *out);
 
 hid_t _sys_getprocfs(int flags);
 
+/** Returns the time in nanoseconds since the first _sys_time call in the process */
+uint64_t _sys_time(int flags);
+
 /* see shared/execbuf.h */
 long _sys_execbuf(void __user *buf, size_t len);