arch: aarch64 fp context save, proper single-step

kernel/arch/x86_64/src/context.rs

@@ -443,13 +443,7 @@ impl<K: KernelTableManager, PA: PhysicalMemoryAllocator<Address = PhysicalAddres
         })
     }
 
-    fn user(
-        context: UserContextInfo, // entry: usize,
-                                  // arg: usize,
-                                  // cr3: u64,
-                                  // user_stack_sp: usize,
-                                  // fs_base: usize,
-    ) -> Result<Self, Error> {
+    fn user(context: UserContextInfo) -> Result<Self, Error> {
         const USER_TASK_PAGES: usize = 8;
 
         let stack_base_phys = PA::allocate_contiguous_pages(USER_TASK_PAGES)?;
@@ -457,7 +451,12 @@ impl<K: KernelTableManager, PA: PhysicalMemoryAllocator<Address = PhysicalAddres
 
         let mut stack = StackBuilder::new(stack_base, USER_TASK_PAGES * 0x1000);
 
-        stack.push(0x200);
+        let mut flags = 0x200;
+        if context.single_step {
+            flags |= 1 << 8;
+        }
+
+        stack.push(flags);
         stack.push(context.entry as _);
         stack.push(context.argument);
         stack.push(context.stack_pointer);

kernel/arch/x86_64/src/lib.rs

@@ -89,6 +89,9 @@ impl ArchitectureImpl {
 impl Architecture for ArchitectureImpl {
     type PerCpuData = PerCpuData;
     type CpuFeatures = CpuFeatures;
+    type BreakpointType = u8;
+
+    const BREAKPOINT_VALUE: Self::BreakpointType = 0xCC;
 
     unsafe fn set_local_cpu(cpu: *mut ()) {
         MSR_IA32_KERNEL_GS_BASE.set(cpu as u64);