feat: add support for shutdown/reboot via UEFI Runtime Services

kernel/src/Api/Power.hpp

@@ -6,23 +6,33 @@
 
 #pragma once
 #include <cstdint>
+#include <Efi/UEFI.hpp>
+#include <Memory/Paging.hpp>
 
 namespace Zenith {
 
     static void Sys_Reset() {
-        /*
-            Triple fault for now; TODO: implement UEFI runtime function for clean reboot.
+        if (Efi::g_ResetSystem) {
+            /* Switch to kernel PML4 which has identity-mapped UEFI runtime regions */
+            Memory::VMM::LoadCR3(Memory::VMM::g_paging->PML4);
+            Efi::g_ResetSystem(Efi::EfiResetCold, 0, 0, nullptr);
+        }
 
-            We implement the triple fault by loading a null IDT into the IDT register,
-            and then immediately triggering an interrupt.
-
-            This technique should pretty much work across the board but it's of course
-            better to use the UEFI runtime API as it has a method for this purpose,
-            along with shutdown.
-        */
-       
+        /* Fallback: triple fault via null IDT */
         struct [[gnu::packed]] { uint16_t limit; uint64_t base; } nullIdt = {0, 0};
         asm volatile("lidt %0; int $0x03" :: "m"(nullIdt));
         __builtin_unreachable();
     }
+
+    static void Sys_Shutdown() {
+        if (Efi::g_ResetSystem) {
+            /* Switch to kernel PML4 which has identity-mapped UEFI runtime regions */
+            Memory::VMM::LoadCR3(Memory::VMM::g_paging->PML4);
+            Efi::g_ResetSystem(Efi::EfiResetShutdown, 0, 0, nullptr);
+        }
+
+        /* No fallback for shutdown; halt the CPU */
+        asm volatile("cli; hlt");
+        __builtin_unreachable();
+    }
 };

kernel/src/Api/Syscall.cpp

@@ -109,8 +109,8 @@ namespace Zenith {
                 Sys_Reset();
                 return 0;
             case SYS_SHUTDOWN:
-                /* Unimplemented */
-                return -1;
+                Sys_Shutdown();
+                return 0;
             case SYS_GETTIME:
                 Sys_GetTime((DateTime*)frame->arg1);
                 return 0;