5 files changed, 77 insertions, 7 deletions
diff --git a/src/kernel/cmos.c b/src/kernel/cmos.c
new file mode 100644
index 0000000..39f7c4f
--- /dev/null
+++ b/src/kernel/cmos.c
@@ -0,0 +1,34 @@
+#include "cmos.h"
+#include "util.h"
+
+static inline uint8_t read_cmos(uint8_t reg) {
+  outb(0x0070, reg);
+  return inb(0x0071);
+}
+
+//The idea of reading until you get the same value twice, and checking the status register
+//  is from the OSDev Wiki page at <https://wiki.osdev.org/CMOS#The_Real-Time_Clock>.
+struct rtc_time get_rtc_time() {
+  uint8_t prev_sec = -1;
+  struct rtc_time ret;
+get_sec:
+  while (read_cmos(0x0a) & 0x80)
+    ;//spin while rtc is being updated
+  ret.seconds      = read_cmos(0x00);
+  if (ret.seconds != prev_sec) {
+    prev_sec = ret.seconds;
+    goto get_sec;
+  }
+  ret.minutes      = read_cmos(0x02);
+  ret.hours        = read_cmos(0x04);
+  if (ret.hours & 0x80) {
+    ret.hours -= 0x80 - 12;
+    if (ret.hours == 24)
+      ret.hours = 0;
+  }
+  ret.day_of_week  = read_cmos(0x06);
+  ret.day_of_month = read_cmos(0x07);
+  ret.month        = read_cmos(0x08);
+  ret.year         = read_cmos(0x09);
+  return ret;
+}
+\ No newline at end of file
diff --git a/src/kernel/cmos.h b/src/kernel/cmos.h
new file mode 100644
index 0000000..53ec398
--- /dev/null
+++ b/src/kernel/cmos.h
@@ -0,0 +1,18 @@
+#ifndef CMOS_H
+#define CMOS_H
+
+#include <stdint.h>
+
+struct rtc_time {
+  uint8_t seconds;
+  uint8_t minutes;
+  uint8_t hours;
+  uint8_t day_of_week;
+  uint8_t day_of_month;
+  uint8_t month;
+  uint8_t year;
+};
+
+struct rtc_time get_rtc_time();
+
+#endif
+\ No newline at end of file
diff --git a/src/kernel/idt.c b/src/kernel/idt.c
index 9b3ba96..99284ac 100644
--- a/src/kernel/idt.c
+++ b/src/kernel/idt.c
@@ -2,6 +2,7 @@
 #include "window.h"
 #include "drive.h"
 #include "panic.h"
+#include "cmos.h"
 #include "pmap.h"
 #include "task.h"
 #include "util.h"
@@ -141,6 +142,21 @@ uint32_t sc_is_task_running(uint32_t handle) {
   return tasks[handle - 1].page_directory ? 1 : 0;
 }
 
+static const uint16_t days_into_four_years_per_month[] = {
+     0,      31,      60,      91,      121,      152,      182,      213,      244,      274,      305,      335,
+   366,  366+31,  366+59,  366+90,  366+120,  366+151,  366+181,  366+212,  366+243,  366+273,  366+304,  366+334,
+   731,  731+31,  731+59,  731+90,  731+120,  731+151,  731+181,  731+212,  731+243,  731+273,  731+304,  731+334,
+  1096, 1096+31, 1096+59, 1096+90, 1096+120, 1096+151, 1096+181, 1096+212, 1096+243, 1096+273, 1096+304, 1096+334
+};
+
+//gregorian, assumes year is in 2001 to 2099
+uint32_t sc_get_timestamp() {
+  const struct rtc_time time = get_rtc_time();
+  const uint32_t secs_into_month = time.seconds + time.minutes * 60 + time.hours * 3600 + (time.day_of_month - 1) * 86400;
+  const uint32_t days_to_month_into_four_years = days_into_four_years_per_month[time.month + (time.year % 4) * 12 - 1];
+  return secs_into_month + days_to_month_into_four_years * 86400 + (time.year / 4) * (365 * 4 + 1) * 86400;
+}
+
 void const *syscall_table[] = {
   &sc_open_file,
   &sc_close_file,
@@ -166,7 +182,8 @@ void const *syscall_table[] = {
   &sc_wait_any_ipc_sent,
   &find_unread_ipc,
   &sc_wait_ipc_read,
-  &sc_is_task_running
+  &sc_is_task_running,
+  &sc_get_timestamp
 };
 
 //these aren't really void ()'s, but gcc complains if we take an address of a void, so we give it a type
diff --git a/src/kernel/isrs.asm b/src/kernel/isrs.asm
index a4eb988..f547bfb 100644
--- a/src/kernel/isrs.asm
+++ b/src/kernel/isrs.asm
@@ -25,7 +25,7 @@ extern exception_halt
 extern pf_check_stack
 extern dump
 
-n_syscalls equ 0x19
+n_syscalls equ 0x1a
 
 ;section .bss
 ;_debug_is_start_task resb 1
diff --git a/src/kernel/main.c b/src/kernel/main.c
index 26cc5e4..1fd3182 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -4,16 +4,17 @@
 #include "window.h"
 #include "panic.h"
 #include "boot.h"
+#include "cmos.h"
+#include "pmap.h"
+#include "task.h"
 #include "util.h"
+#include "elf.h"
 #include "fat.h"
 #include "ide.h"
 #include "idt.h"
-#include "pmap.h"
-#include "task.h"
-#include "pci.h"
-#include "elf.h"
-#include "log.h"
 #include "kbd.h"
+#include "log.h"
+#include "pci.h"
 
 void _start_user_mode() __attribute__ ((noreturn));