Kernel: Jump to userspace and back!

corigan01 · Jan 15, 2025 · 6e79673 · 6e79673
1 parent f7e3b42
commit 6e79673
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Showing 4 changed files with 13 additions and 8 deletions.
diff --git a/crates/arch/src/gdt.rs b/crates/arch/src/gdt.rs
@@ -191,6 +191,7 @@ impl TaskStateSegmentPtr {
         task.set_base(tss as *const _ as u64);
         task.set_limit(size_of::<crate::tss64::TaskStateSegment>() as u32);
 
+        task.set_accessed_flag(true);
         task.set_present_flag(true);
         task.set_code_segment_flag(true);
         task.set_accessed_flag(true);

diff --git a/kernel/src/int.rs b/kernel/src/int.rs
@@ -40,14 +40,17 @@ use lldebug::{log, logln, sync::Mutex};
 static INTERRUPT_TABLE: Mutex<InterruptDescTable> = Mutex::new(InterruptDescTable::new());
 static IRQ_HANDLERS: Mutex<[Option<fn(&InterruptInfo)>; 32]> = Mutex::new([None; 32]);
 
-#[interrupt(0..48)]
+#[interrupt(0..50)]
 fn main_handler(args: InterruptInfo) {
     match args.flags {
         // IRQ
         InterruptFlags::Irq(irq_num) if irq_num - PIC_IRQ_OFFSET <= 16 => {
             call_attached_irq(irq_num - PIC_IRQ_OFFSET, &args);
             unsafe { pic_eoi(irq_num - PIC_IRQ_OFFSET) };
         }
+        InterruptFlags::Irq(irq_num) if irq_num == 49 => unsafe {
+            task_start();
+        },
         InterruptFlags::Debug => (),
         exception => {
             panic!("UNHANDLED FAULT\n{:#016x?}", args)
@@ -104,7 +107,8 @@ pub fn attach_syscall() {
     gate.set_privilege(arch::CpuPrivilege::Ring3);
     gate.set_offset(syscall_entry as u64);
     gate.set_gate_kind(arch::idt64::GateKind::InterruptGate);
-    gate.set_code_segment(Segment::new(3, arch::CpuPrivilege::Ring3));
+    gate.set_code_segment(Segment::new(1, arch::CpuPrivilege::Ring0));
+    // gate.set_code_segment(Segment::new(3, arch::CpuPrivilege::Ring3));
 
     idt.attach_raw(0x80, gate);
     unsafe { idt.submit_table().load() };
@@ -127,7 +131,7 @@ unsafe extern "C" {
 
 #[unsafe(no_mangle)]
 extern "C" fn syscall_handler() {
-    todo!()
+    logln!("Hello from userspace!");
 }
 
 global_asm!(
@@ -170,7 +174,6 @@ global_asm!(
     r#"
     .global task_start
     task_start:
-        cli
         # Save our state to the stack
         push rax
         push rbx

diff --git a/kernel/src/main.rs b/kernel/src/main.rs
@@ -73,7 +73,8 @@ fn main(kbh: &KernelBootHeader) {
     );
 
     gdt::init_kernel_gdt();
-    gdt::set_stack_for_privl(0x200000000000 as *mut u8, Ring0);
+    // gdt::set_stack_for_privl(0x200000000000 as *mut u8, Ring0);
+    gdt::set_stack_for_privl(0x3000 as *mut u8, Ring0);
     unsafe { gdt::load_tss() };
     int::attach_interrupts();
     int::attach_syscall();
@@ -136,9 +137,8 @@ fn main(kbh: &KernelBootHeader) {
         })
         .unwrap();
 
-    unsafe {
-        task_start();
-    }
+    logln!("Attempting to jump to userspace!");
+    unsafe { core::arch::asm!("int 0x31") };
     loop {}
 
     logln!("Finished in {}ms", kernel_ticks());

diff --git a/user/dummy/src/main.rs b/user/dummy/src/main.rs
@@ -50,4 +50,5 @@ extern "C" fn _start() {
     unsafe {
         test_syscall();
     }
+    loop {}
 }
-Original file line number
+Diff line change
@@ Expand Up / @@ -50,4 +50,5 @@ extern "C" fn _start() { @@
         unsafe {
             test_syscall();
         }
+        loop {}
     }