Boot to desktop on aarch64.

src/arch/aarch64/interrupt/handler.rs

@@ -113,9 +113,7 @@ pub struct InterruptStack {
 }
 
 impl InterruptStack {
-    pub fn setup_minimal(&mut self, ip: usize, _singlestep: bool) {
-        self.set_instr_pointer(ip);
-    }
+    pub fn init(&mut self) {}
     pub fn set_stack_pointer(&mut self, sp: usize) {
         self.iret.sp_el0 = sp;
     }
@@ -405,6 +403,7 @@ macro_rules! exception_stack {
 #[naked]
 pub unsafe extern "C" fn enter_usermode() -> ! {
     core::arch::asm!(concat!(
+        "blr x28\n",
         // Restore all userspace registers
         pop_special!(),
         pop_scratch!(),

src/arch/aarch64/start.rs

@@ -218,19 +218,3 @@ pub struct KernelArgsAp {
 pub unsafe extern "C" fn kstart_ap(args_ptr: *const KernelArgsAp) -> ! {
     loop {}
 }
-
-#[naked]
-//TODO: AbiCompatBool
-//TODO: clear all regs?
-pub unsafe extern "C" fn usermode(_ip: usize, _sp: usize, _arg: usize, _is_singlestep: usize) -> ! {
-    core::arch::asm!(
-        "
-        msr spsr_el1, xzr // spsr
-        msr elr_el1, x0 // ip
-        msr sp_el0, x1 // sp
-        mov x0, x2 // arg
-        eret
-        ",
-        options(noreturn),
-    );
-}

src/context/arch/aarch64.rs

@@ -80,6 +80,10 @@ impl Context {
         self.sp = address;
     }
 
+    pub fn set_x28(&mut self, x28: usize) {
+        self.x28 = x28;
+    }
+
     pub fn set_lr(&mut self, address: usize) {
         self.lr = address;
     }

src/context/list.rs

@@ -117,14 +117,19 @@ impl ContextList {
 
             let mut stack_top = unsafe { stack.as_mut_ptr().add(KSTACK_SIZE) };
 
-            unsafe {
-                if userspace_allowed {
+            const INT_REGS_SIZE: usize = core::mem::size_of::<crate::interrupt::InterruptStack>();
+
+            if userspace_allowed {
+                unsafe {
                     // Zero-initialize InterruptStack registers.
-                    const INT_REGS_SIZE: usize = core::mem::size_of::<crate::interrupt::InterruptStack>();
                     stack_top = stack_top.sub(INT_REGS_SIZE);
                     stack_top.write_bytes(0_u8, INT_REGS_SIZE);
                     (&mut *stack_top.cast::<InterruptStack>()).init();
-
+                }
+            }
+            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+            unsafe {
+                if userspace_allowed {
                     stack_top = stack_top.sub(core::mem::size_of::<usize>());
                     stack_top.cast::<usize>().write(crate::interrupt::syscall::enter_usermode as usize);
                 }
@@ -134,8 +139,9 @@ impl ContextList {
             }
 
             #[cfg(target_arch = "aarch64")]
-            {
-                context.arch.set_lr(func as usize);
+            unsafe {
+                context.arch.set_lr(crate::interrupt::syscall::enter_usermode as usize);
+                context.arch.set_x28(func as usize);
                 context.arch.set_context_handle();
             }