Add exception handling

kernel.s

@@ -2,7 +2,8 @@
 
 .section .rodata
 
-hello_world: .asciz "\nHello world!\n"
+panic_message: .asciz "\nPanic"
+.equ PANIC_MESSAGE_SIZE, . - panic_message
 
 .section .text
 
@@ -18,21 +19,6 @@ bzero:
 .Lbzero_end:
 	ret
 
-# Arguments:
-# a0 - Character.
-.type putchar, @function
-putchar:
-	li a1, 0
-	li a2, 0
-	li a3, 0
-	li a4, 0
-	li a5, 0
-	li a6, 0
-	li a7, 1 # sbi_console_putchar.
-
-	ecall
-	ret
-
 .type kernel_main, @function
 kernel_main:
 	# Prologue.
@@ -41,28 +27,156 @@ kernel_main:
 	sw s0, 24(sp)
 	addi s0, sp, 32
 
-	sw s1, 20(sp)
+	la t0, kernel_entry
+	csrw stvec, t0
 
-	la s1, hello_world
-
-.Lkernel_main_if:
-	lw a0, (s1)
-	beqz a0, .Lkernel_main
-
-	call putchar
-	addi s1, s1, 1
-
-	j .Lkernel_main_if
+	unimp
 
 .Lkernel_main:
 	j .Lkernel_main
 
-	lw s1, 20(sp)
+	# Epilogue.
+	lw ra, 28(sp)
+	lw s0, 24(sp)
+	addi sp, sp, 32
+	ret
+
+.balign 4
+.type kernel_entry, @function
+kernel_entry:
+	csrw sscratch, sp
+	addi sp, sp, -4 * 31
+
+	sw ra, 0(sp)
+	sw gp, 4(sp)
+	sw tp, 8(sp)
+	sw t0, 12(sp)
+	sw t1, 16(sp)
+	sw t2, 20(sp)
+	sw t3, 24(sp)
+	sw t4, 28(sp)
+	sw t5, 32(sp)
+	sw t6, 36(sp)
+	sw a0, 40(sp)
+	sw a1, 44(sp)
+	sw a2, 48(sp)
+	sw a3, 52(sp)
+	sw a4, 56(sp)
+	sw a5, 60(sp)
+	sw a6, 64(sp)
+	sw a7, 68(sp)
+	sw s0, 72(sp)
+	sw s1, 76(sp)
+	sw s2, 80(sp)
+	sw s3, 84(sp)
+	sw s4, 88(sp)
+	sw s5, 92(sp)
+	sw s6, 96(sp)
+	sw s7, 100(sp)
+	sw s8, 104(sp)
+	sw s9, 108(sp)
+	sw s10, 112(sp)
+	sw s11, 116(sp)
+
+	csrr a0, sscratch
+	sw a0, 120(sp)
+
+	mv a0, sp
+	call handle_trap
+
+	lw ra, 0(sp)
+	lw gp, 4(sp)
+	lw tp, 8(sp)
+	lw t0, 12(sp)
+	lw t1, 16(sp)
+	lw t2, 20(sp)
+	lw t3, 24(sp)
+	lw t4, 28(sp)
+	lw t5, 32(sp)
+	lw t6, 36(sp)
+	lw a0, 40(sp)
+	lw a1, 44(sp)
+	lw a2, 48(sp)
+	lw a3, 52(sp)
+	lw a4, 56(sp)
+	lw a5, 60(sp)
+	lw a6, 64(sp)
+	lw a7, 68(sp)
+	lw s0, 72(sp)
+	lw s1, 76(sp)
+	lw s2, 80(sp)
+	lw s3, 84(sp)
+	lw s4, 88(sp)
+	lw s5, 92(sp)
+	lw s6, 96(sp)
+	lw s7, 100(sp)
+	lw s8, 104(sp)
+	lw s9, 108(sp)
+	lw s10, 112(sp)
+	lw s11, 116(sp)
+	lw sp, 120(sp)
+
+	sret
+
+.type handle_trap, @function
+handle_trap:
+	# Prologue.
+	addi sp, sp, -32
+	sw ra, 28(sp)
+	sw s0, 24(sp)
+	addi s0, sp, 32
+
+	csrr t0, scause
+	csrr t1, stval
+	csrr t2, sepc
+
+	li a0, PANIC_MESSAGE_SIZE
+	la a1, panic_message
+	call write_s
+
+	li a0, ' '
+	call write_c
+
+	csrr a0, scause
+	call write_i
+
+	li a0, ','
+	call write_c
+
+	csrr a0, stval
+	call write_i
+
+	li a0, ','
+	call write_c
+
+	csrr a0, sepc
+	call write_i
+
+	call panic
 
 	# Epilogue.
 	lw ra, 28(sp)
 	lw s0, 24(sp)
-	add sp, sp, 32
+	addi sp, sp, 32
+	ret
+
+.type panic, @function
+panic:
+	# Prologue.
+	addi sp, sp, -32
+	sw ra, 28(sp)
+	sw s0, 24(sp)
+	addi s0, sp, 32
+
+	li a0, '\n'
+	call write_c
+.Lpanic:
+	j .Lpanic
+
+	# Epilogue.
+	lw ra, 28(sp)
+	lw s0, 24(sp)
+	addi sp, sp, 32
 	ret
 
 .section .text.boot