feat: add time syscall & command in shell

programs/include/Api/Syscall.hpp

@@ -39,6 +39,16 @@ namespace Zenith {
     static constexpr uint64_t SYS_GETARGS         = 25;
     static constexpr uint64_t SYS_RESET           = 26;
     static constexpr uint64_t SYS_SHUTDOWN        = 27;
+    static constexpr uint64_t SYS_GETTIME         = 28;
+
+    struct DateTime {
+        uint16_t Year;
+        uint8_t Month;
+        uint8_t Day;
+        uint8_t Hour;
+        uint8_t Minute;
+        uint8_t Second;
+    };
 
     struct FbInfo {
         uint64_t width;

programs/include/zenith/syscall.h

@@ -176,6 +176,9 @@ namespace zenith {
         if (rows) *rows = (int)(r >> 32);
     }
 
+    // Timekeeping (wall-clock)
+    inline void gettime(Zenith::DateTime* out) { syscall1(Zenith::SYS_GETTIME, (uint64_t)out); }
+
     // Power management
     [[noreturn]] inline void reset() {
         syscall0(Zenith::SYS_RESET);