src/main.rs

@@ -6,14 +6,12 @@
 use core::panic::PanicInfo;
 
 mod heap;
-mod trap;
 mod uart;
 
 #[naked]
 #[no_mangle]
 #[link_section = ".text.init"]
 unsafe extern "C" fn _enter() -> ! {
-    // TODO see if possible to replace this somehow...
     use core::arch::asm;
     asm!(
         // load hartid into t0; if t0 =/= 0, then jump to busy loop
@@ -31,17 +29,9 @@ unsafe extern "C" fn _enter() -> ! {
         "la gp, _global_pointer",
         ".option pop", // pops the current option stack
 
-        // delegate all traps to S-mode trap handler
-        "li t5, 0xffff",
-        "csrw medeleg, t5", // delegate all machine exceptions
-        "csrw mideleg, t5", // delegate all machine interrupts
-
         // set the stack pointer
         "la sp, _init_stack_top",
 
-        "la t2, {trap_vector}",
-        "csrw mtvec, t2",
-
         // clear the BSS
         "la t0, _bss_start",
         "la t1, _bss_end",
@@ -51,8 +41,8 @@ unsafe extern "C" fn _enter() -> ! {
         "addi t0, t0, 1",
         "bne t0, t1, 1b",
     "2:",
-        "j 4f",
         // BSS is clear!
+        "j 4f",
     
     // busy loop if hartid =/= 0
     "3:",
@@ -63,7 +53,6 @@ unsafe extern "C" fn _enter() -> ! {
         // "tail-call" to {start} (call without saving a return address)
         "tail {start}",
         start = sym start, // {start} refers to the function [start] below
-        trap_vector = sym trap::trap_handler, // {trap_vector} refers to function [trap::trap_handler]
         options(noreturn) // we must handle "returning" from assembly
     );
 }

src/script.ld

@@ -38,7 +38,7 @@ SECTIONS {
   } >ram AT>ram :bss # and this goes into the bss segment
 
   . = ALIGN(16); # our stack needs to be 16-byte aligned, per the C calling convention
-  PROVIDE(_init_stack_top = . + 0x1000); # reserve 0x1000 bytes (4 kB) for the initialisation stack
+  PROVIDE(_init_stack_top = . + 0x1000); # reserve 0x1000 bytes for the initialisation stack
 
   PROVIDE(_kernel_heap_bottom = _init_stack_top); # allocate heap to remaining physical memory
   PROVIDE(_kernel_heap_top = ORIGIN(ram) + LENGTH(ram)); # top of heap is end of ram

src/trap.rs

@@ -1,8 +0,0 @@
-#[naked]
-pub unsafe extern "C" fn trap_handler() -> ! {
-    use core::arch::asm;
-    asm!(
-        "mret",
-        options(noreturn)
-    );
-}