From 0aac6c888d23d70fb4792ce42c90b150cc464f85 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Thu, 5 Jan 2023 21:53:48 +0100
Subject: [PATCH] x86_64: Basic exit() syscall!

User processes need to do something, amirite?
---
 kernel/src/arch/x86_64/CPU.asm      | 3 ++-
 kernel/src/arch/x86_64/CPU.cpp      | 6 ++++++
 kernel/src/arch/x86_64/init/IDT.cpp | 5 ++++-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/src/arch/x86_64/CPU.asm b/kernel/src/arch/x86_64/CPU.asm
index f5a2c98a..00b58b7e 100644
--- a/kernel/src/arch/x86_64/CPU.asm
+++ b/kernel/src/arch/x86_64/CPU.asm
@@ -187,4 +187,5 @@ ISR 20 ; virtualization exception (#VE)
 ISR_ERROR 21 ; control-protection exception (#CP)
 ; ISR 22-31 reserved
 IRQ 32, 0 ; timer interrupt
-IRQ 33, 0 ; keyboard interrupt
\ No newline at end of file
+IRQ 33, 0 ; keyboard interrupt
+ISR 66 ; user exit
diff --git a/kernel/src/arch/x86_64/CPU.cpp b/kernel/src/arch/x86_64/CPU.cpp
index bb0455d8..8dca8b89 100644
--- a/kernel/src/arch/x86_64/CPU.cpp
+++ b/kernel/src/arch/x86_64/CPU.cpp
@@ -107,6 +107,12 @@ extern "C" void arch_interrupt_entry(Registers* regs)
         scancode_queue.try_push(scancode);
         pic_eoi(regs);
     }
+    else if (regs->isr == 66) // Exit!!
+    {
+        kdbgln("exiting from user task!!");
+        Scheduler::current()->state = ThreadState::Dying;
+        kernel_yield();
+    }
     else
     {
         kwarnln("IRQ catched! Halting.");
diff --git a/kernel/src/arch/x86_64/init/IDT.cpp b/kernel/src/arch/x86_64/init/IDT.cpp
index e507613e..22ea980a 100644
--- a/kernel/src/arch/x86_64/init/IDT.cpp
+++ b/kernel/src/arch/x86_64/init/IDT.cpp
@@ -36,7 +36,7 @@ u64 IDTEntry::get_offset() const
 static IDTEntry idt[256];
 
 #define IDT_TA_InterruptGate 0b10001110
-#define IDT_TA_UserInterruptGate 0b11101110
+#define IDT_TA_UserCallableInterruptGate 0b11101110
 #define IDT_TA_TrapGate 0b10001111
 
 struct [[gnu::packed]] IDTR
@@ -60,6 +60,7 @@ static void idt_add_handler(short num, void* handler, u8 type_attr)
 #define INT(x) extern "C" void _isr##x()
 #define TRAP(x) idt_add_handler(x, (void*)_isr##x, IDT_TA_TrapGate)
 #define IRQ(x) idt_add_handler(x, (void*)_isr##x, IDT_TA_InterruptGate)
+#define SYS(x) idt_add_handler(x, (void*)_isr##x, IDT_TA_UserCallableInterruptGate)
 
 INT(0);
 INT(1);
@@ -83,6 +84,7 @@ INT(20);
 INT(21);
 INT(32);
 INT(33);
+INT(66);
 
 void setup_idt()
 {
@@ -110,6 +112,7 @@ void setup_idt()
     TRAP(21);
     IRQ(32);
     IRQ(33);
+    SYS(66);
 
     static IDTR idtr;
     idtr.limit = 0x0FFF;