Add exception handling

common.s

@@ -3,7 +3,7 @@
 # obtain one at https://mozilla.org/MPL/2.0/.
 
 .global _is_alpha, _is_digit, _is_alnum, _is_upper, _is_lower
-.global _write_s, _read_file, _write_error, _write_c, _write_i, _print_i
+.global write_s, _read_file, _write_error, write_c, write_i, _print_i
 .global _memcmp, _memchr, _memmem, _memcpy, _mmap
 .global _current, _get, _advance, _label_counter
 .global _divide_by_zero_error, _exit, _strings_index, _string_equal
@@ -175,28 +175,44 @@ _is_alnum:
 	addi sp, sp, 16
 	ret
 
-# Writes a string to the standard output.
+# Prints a string.
 #
 # Parameters:
 # a0 - Length of the string.
 # a1 - String pointer.
-.type _write_s, @function
-_write_s:
+.type write_s, @function
+write_s:
 	# Prologue.
-	addi sp, sp, -8
-	sw ra, 4(sp)
-	sw s0, 0(sp)
-	addi s0, sp, 8
+	addi sp, sp, -32
+	sw ra, 28(sp)
+	sw s0, 24(sp)
+	addi s0, sp, 32
 
-	mv a2, a0
-	li a0, STDOUT
-	li a7, SYS_WRITE
-	ecall
+	sw s1, 20(sp)
+	sw s2, 16(sp)
+
+	mv s1, a0
+	mv s2, a1
+
+.Lwrite_s_if:
+	beqz s1, .Lwrite_s_end
+
+	lw a0, (s2)
+	call write_c
+
+	addi s1, s1, -1
+	addi s2, s2, 1
+
+	j .Lwrite_s_if
+
+.Lwrite_s_end:
+	lw s1, 20(sp)
+	lw s2, 16(sp)
 
 	# Epilogue.
-	lw ra, 4(sp)
-	lw s0, 0(sp)
-	addi sp, sp, 8
+	lw ra, 28(sp)
+	lw s0, 24(sp)
+	addi sp, sp, 32
 	ret
 
 # Reads standard input into a buffer.
@@ -308,8 +324,8 @@ _print_i:
 #
 # Parameters:
 # a0 - Whole number.
-.type _write_i, @function
-_write_i:
+.type write_i, @function
+write_i:
     addi sp, sp, -32
     sw ra, 28(sp)
     sw s0, 24(sp)
@@ -319,33 +335,28 @@ _write_i:
 	call _print_i
 
 	addi a1, sp, 0
-	call _write_s
+	call write_s
 
     lw ra, 28(sp)
     lw s0, 24(sp)
     addi sp, sp, 32
     ret
 
-# Writes a character from a0 into the standard output.
-.type _write_c, @function
-_write_c:
-	# Prologue
-	addi sp, sp, -16
-	sw ra, 12(sp)
-	sw s0, 8(sp)
-	addi s0, sp, 16
+# Prints a character from a0.
+#
+# Arguments:
+# a0 - Character.
+.type write_c, @function
+write_c:
+	li a1, 0
+	li a2, 0
+	li a3, 0
+	li a4, 0
+	li a5, 0
+	li a6, 0
+	li a7, 1 # sbi_console_putchar.
 
-	sb a0, 4(sp)
-	li a0, STDOUT
-	addi a1, sp, 4
-	li a2, 1
-	li a7, SYS_WRITE
 	ecall
-
-	# Epilogue.
-	lw ra, 12(sp)
-	lw s0, 8(sp)
-	add sp, sp, 16
 	ret
 
 # a0 - Pointer to an array to get the first element.

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

run.sh

@@ -7,7 +7,7 @@ QEMU=qemu-system-riscv32
 
 # Path to clang and compiler flags
 CC=../riscv32-ilp32d--glibc/bin/riscv32-linux-gcc
-CFLAGS="-O2 -g3 -Wall -march=rv32im -mabi=ilp32 -fno-stack-protector -ffreestanding -nostdlib -static"
+CFLAGS="-O2 -g3 -Wall -march=rv32imzicsr -mabi=ilp32 -fno-stack-protector -ffreestanding -nostdlib -static"
 
 # Build the kernel
 $CC $CFLAGS -T kernel.ld -Wl,-Map=kernel.map -o kernel.elf kernel.s common.s