.global kernel_main, __bss, __bss_end, __stack_top

.section .rodata

panic_message: .asciz "\nPanic"
.equ PANIC_MESSAGE_SIZE, . - panic_message

.section .text

bzero:
	la t0, __bss
	la t1, __bss_end

.Lbzero_loop:
	bgt t0, t1, .Lbzero_end
	sw zero, (t0)
	addi t0, t0, 4

.Lbzero_end:
	ret

.type kernel_main, @function
kernel_main:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	la t0, kernel_entry
	csrw stvec, t0

	mv a0, a1
	call device_tree

	# Prepare the kernel root memory table.
	la a0, __free_ram
	li a1, 8
	call write_x

	la t0, __free_ram
	srli t0, t0, 10
	li t1, 0xf0000000
	or t0, t0, t1

	la t1, __free_ram
	sw t0, (t1)

	la t0, __free_ram
	ori t0, t0, 1

	csrw satp, t0
	sfence.vma zero, zero


	# Do nothing in a loop.
.Lkernel_main:
	j .Lkernel_main

	# 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 a1, PANIC_MESSAGE_SIZE
	la a0, panic_message
	call write_s

	li a0, ' '
	call write_c

	csrr a0, scause
	call write_i

	call separator
	call write_c

	csrr a0, stval
	call write_i

	call separator
	call write_c

	csrr a0, sepc
	call write_i

	call panic

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	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
boot:
	la t0, __stack_top
	mv sp, t0 # Set the stack pointer

	lw t0, (__free_ram)
	la t1, next_paddr
	sw t0, (t1)

	call bzero
	j kernel_main