## Copyright (C) 2021 Andrius Štikonas
## Copyright (C) 2023 Janneke Nieuwenhuizen <janneke@gnu.org>
##
## This file is part of stage0.
##
## stage0 is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## stage0 is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with stage0.  If not, see <http://www.gnu.org/licenses/>.

:_start
	RD_FP RS1_SP MV        ; Protect stack pointer

	; Prepare argv
	RD_A0 RS1_FP !8 ADDI   ; ARGV_address = FP + 8
	RD_SP RS1_SP !-8 ADDI
	RS1_SP RS2_A0 SD       ; Put argv on the stack

	; Prepare envp
	RD_A0 RS1_FP MV        ; Address we need to load from
	RD_A0 RS1_A0 LD        ; Get ARGC
	RD_A0 RS1_A0 !2 ADDI   ; OFFSET = ARGC + 2
	RD_A0 RS1_A0 RS2_X3 SLLI ; OFFSET = OFFSET * WORDSIZE
	RD_A0 RS1_FP RS2_A0 ADD ; ENVP_address = RSP + OFFSET
	RD_SP RS1_SP !-8 ADDI
	RS1_SP RS2_A0 SD       ; Put envp on the stack

        # AAARG, this also does not work!?
        # pop____%t0 ; envp
        # push___%t0
        # li_____%t0,$i32 &GLOBAL_environ

        # li_____%t0,$i16_0000 @0
        # XXX avoid Illegal instruction
        # li_____%t1,$i32 &GLOBAL___stdin
        # sw_____%t0,0(%t1)

        # li_____%t0,$i16_0000 @1
        # srai___%t0,16
        # li_____%t1,$i32 &GLOBAL___stdout
        # sw_____%t0,0(%t1)

        # li_____%t0,$i16_0000 @2
        # XXX avoid Segmentation fault
        # srai___%t0,16
        # li_____%t1,$i32 &GLOBAL___stderr
        # sw_____%t0,0(%t1)

	; Stack offset
	RD_FP RS1_FP !8 ADDI

        ; Init libc
        RD_RA $FUNCTION___init_io JAL

	; Call main function
	RD_RA $FUNCTION_main JAL

	; Put return value on the stack so that _exit gets it
	RD_SP RS1_SP !-16 ADDI
	RS1_SP RS2_A0 SD

	; Exit to kernel

	RD_A0 RS1_SP LD
	RD_A7 !93 ADDI         ; Syscall for exit
	ECALL                  ; Exit with code in a0