Add code for “Returning from Exceptions”

Makefile

@@ -8,7 +8,7 @@
 # except according to those terms.
 
 arch ?= x86_64
-target ?= $(arch)-unknown-linux-gnu
+target ?= $(arch)-blog_os
 kernel := build/kernel-$(arch).bin
 iso := build/os-$(arch).iso
 
@@ -49,7 +49,7 @@ $(kernel): cargo $(rust_os) $(assembly_object_files) $(linker_script)
 	@ld -n --gc-sections -T $(linker_script) -o $(kernel) $(assembly_object_files) $(rust_os)
 
 cargo:
-	@cargo build --target $(target)
+	@xargo build --target $(target)
 
 # compile assembly files
 build/arch/$(arch)/%.o: src/arch/$(arch)/%.asm

src/interrupts/mod.rs

@@ -1,16 +1,50 @@
 mod idt;
 
+macro_rules! save_scratch_registers {
+    () => {
+        asm!("push rax
+              push rcx
+              push rdx
+              push rsi
+              push rdi
+              push r8
+              push r9
+              push r10
+              push r11
+        " :::: "intel", "volatile");
+    }
+}
+
+macro_rules! restore_scratch_registers {
+    () => {
+        asm!("pop r11
+              pop r10
+              pop r9
+              pop r8
+              pop rdi
+              pop rsi
+              pop rdx
+              pop rcx
+              pop rax
+            " :::: "intel", "volatile");
+    }
+}
+
 macro_rules! handler {
     ($name: ident) => {{
         #[naked]
         extern "C" fn wrapper() -> ! {
             unsafe {
+                save_scratch_registers!();
                 asm!("mov rdi, rsp
-                      sub rsp, 8 // align the stack pointer
+                      add rdi, 9*8 // calculate exception stack frame pointer
                       call $0"
                       :: "i"($name as extern "C" fn(
-                          *const ExceptionStackFrame) -> !)
+                          *const ExceptionStackFrame))
                       : "rdi" : "intel");
+
+                restore_scratch_registers!();
+                asm!("iretq" :::: "intel", "volatile");
                 ::core::intrinsics::unreachable();
             }
         }
@@ -23,13 +57,19 @@ macro_rules! handler_with_error_code {
         #[naked]
         extern "C" fn wrapper() -> ! {
             unsafe {
-                asm!("pop rsi // pop error code into rsi
+                save_scratch_registers!();
+                asm!("mov rsi, [rsp + 9*8] // load error code into rsi
                       mov rdi, rsp
+                      add rdi, 10*8 // calculate exception stack frame pointer
                       sub rsp, 8 // align the stack pointer
-                      call $0"
-                      :: "i"($name as extern "C" fn(
-                          *const ExceptionStackFrame, u64) -> !)
+                      call $0
+                      add rsp, 8 // undo stack pointer alignment
+                      " :: "i"($name as extern "C" fn(
+                          *const ExceptionStackFrame, u64))
                       : "rdi","rsi" : "intel");
+                restore_scratch_registers!();
+                asm!("add rsp, 8 // pop error code
+                      iretq" :::: "intel", "volatile");
                 ::core::intrinsics::unreachable();
             }
         }
@@ -42,6 +82,7 @@ lazy_static! {
         let mut idt = idt::Idt::new();
 
         idt.set_handler(0, handler!(divide_by_zero_handler));
+        idt.set_handler(3, handler!(breakpoint_handler));
         idt.set_handler(6, handler!(invalid_opcode_handler));
         idt.set_handler(14, handler_with_error_code!(page_fault_handler));
 
@@ -65,14 +106,22 @@ struct ExceptionStackFrame {
 
 use vga_buffer::print_error;
 
-extern "C" fn divide_by_zero_handler(stack_frame: *const ExceptionStackFrame) -> ! {
+extern "C" fn divide_by_zero_handler(stack_frame: *const ExceptionStackFrame) {
     unsafe {
         print_error(format_args!("EXCEPTION: DIVIDE BY ZERO\n{:#?}", *stack_frame));
     }
     loop {}
 }
 
-extern "C" fn invalid_opcode_handler(stack_frame: *const ExceptionStackFrame) -> ! {
+extern "C" fn breakpoint_handler(stack_frame: *const ExceptionStackFrame) {
+    unsafe {
+        print_error(format_args!("EXCEPTION: BREAKPOINT at {:#x}\n{:#?}",
+                                 (*stack_frame).instruction_pointer,
+                                 *stack_frame));
+    }
+}
+
+extern "C" fn invalid_opcode_handler(stack_frame: *const ExceptionStackFrame) {
     unsafe {
         print_error(format_args!("EXCEPTION: INVALID OPCODE at {:#x}\n{:#?}",
                                  (*stack_frame).instruction_pointer,
@@ -91,7 +140,7 @@ bitflags! {
     }
 }
 
-extern "C" fn page_fault_handler(stack_frame: *const ExceptionStackFrame, error_code: u64) -> ! {
+extern "C" fn page_fault_handler(stack_frame: *const ExceptionStackFrame, error_code: u64) {
     use x86::controlregs;
     unsafe {
         print_error(format_args!("EXCEPTION: PAGE FAULT while accessing {:#x}\nerror code: \

src/lib.rs

@@ -20,6 +20,7 @@ extern crate spin;
 extern crate multiboot2;
 #[macro_use]
 extern crate bitflags;
+#[macro_use]
 extern crate x86;
 #[macro_use]
 extern crate once;
@@ -54,9 +55,8 @@ pub extern "C" fn rust_main(multiboot_information_address: usize) {
     // initialize our IDT
     interrupts::init();
 
-    // provoke a page fault
-    unsafe { *(0xdeadbeaf as *mut u64) = 42 };
-
+    // trigger a breakpoint exception
+    unsafe { int!(3) };
 
     println!("It did not crash!");
     loop {}

x86_64-blog_os.json

@@ -0,0 +1,10 @@
+{
+  "llvm-target": "x86_64-unknown-linux-gnu",
+  "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
+  "target-endian": "little",
+  "target-pointer-width": "64",
+  "arch": "x86_64",
+  "os": "none",
+  "features": "-mmx,-sse,+soft-float",
+  "disable-redzone": true
+}