Kernel/Time: Improve time keeping

This makes use of TSC and now provides a file system interface for
userland programs to change the system time.

1 files changed, 69 insertions, 0 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
new file mode 100644
index 0000000..46a30d3
--- /dev/null
+++ b/kernel/timer.c
@@ -0,0 +1,69 @@
+#include <arch/i386/tsc.h>
+#include <drivers/cmos.h>
+#include <fs/devfs.h>
+#include <math.h>
+#include <time.h>
+#include <typedefs.h>
+
+i64 start_unix_time;
+u64 start_tsc_time;
+
+void timer_init(void) {
+  tsc_init();
+  start_tsc_time = tsc_get();
+  start_unix_time = cmos_get_time();
+}
+
+u64 timer_get_uptime(void) {
+  return tsc_calculate_ms(tsc_get());
+}
+
+void timer_get(struct timespec *tp) {
+  u64 offset_tsc = tsc_get() - start_tsc_time;
+  i64 current_unix_time_seconds =
+      start_unix_time + tsc_calculate_ms(offset_tsc) / 1000;
+  tp->tv_sec = current_unix_time_seconds;
+  tp->tv_nsec = tsc_calculate_ms(offset_tsc);
+}
+
+u64 timer_get_ms(void) {
+  u64 offset_tsc = tsc_get() - start_tsc_time;
+  return start_unix_time * 1000 + tsc_calculate_ms(offset_tsc);
+}
+
+int clock_read(u8 *buffer, u64 offset, u64 len, vfs_fd_t *fd) {
+  (void)offset;
+  u64 r = timer_get_ms();
+  u64 l = min(len, sizeof(u64));
+  memcpy(buffer, &r, l);
+  return l;
+}
+
+int clock_write(u8 *buffer, u64 offset, u64 len, vfs_fd_t *fd) {
+  (void)offset;
+  if (len != sizeof(i64)) {
+    return 0;
+  }
+
+  i64 new_value_ms;
+  memcpy(&new_value_ms, buffer, sizeof(i64));
+  i64 new_value_seconds = new_value_ms / 1000;
+
+  u64 offset_tsc = tsc_get() - start_tsc_time;
+  i64 current_unix_time_seconds =
+      start_unix_time + tsc_calculate_ms(offset_tsc) / 1000;
+
+  i64 delta = new_value_seconds - current_unix_time_seconds;
+  start_unix_time += delta;
+  cmos_set_time(new_value_seconds);
+  return sizeof(i64);
+}
+
+int always_has_data(vfs_inode_t *inode);
+int always_can_write(vfs_inode_t *inode);
+
+int timer_add_clock(void) {
+  devfs_add_file("/clock", clock_read, clock_write, NULL, always_has_data,
+                 always_can_write, FS_TYPE_CHAR_DEVICE);
+  return 1;
+}