X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fstartup.s;h=ebf5fdf3cd474056f11de924a97207b6c3cd2e4d;hp=8e2c2ea3f5e1833cbb59d82cc126c7ddacc7d8f6;hb=7b6f6de2124e28ae7da5599a7cdaf2c171c4f15e;hpb=e5b5905eb3134a409638a5a20462000ef159e1e6

diff --git a/src/startup.s b/src/startup.s
index 8e2c2ea..ebf5fdf 100644
--- a/src/startup.s
+++ b/src/startup.s
@@ -1,11 +1,76 @@
+# pcboot - bootable PC demo/game kernel
+# Copyright (C) 2018-2019  John Tsiombikas <nuclear@member.fsf.org>
+# 
+# This program 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.
+# 
+# This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
+
 	.code32
-	.section .startup
+	.section .startup,"ax"
 
 	.extern _bss_start
 	.extern _bss_end
+	.extern pcboot_main
+	.extern wait_vsync
+	.extern kb_getkey
+
+	.equ STACKTOP,0x80000
 
+	# move the stack to the top of the conventional memory
+	cli
+	movl $STACKTOP, %esp
+	# push a 0 ret-addr to terminate gdb backtraces
+	pushl $0
+
+	# zero the BSS section
 	xor %eax, %eax
-	mov _bss_start, %edi
-	mov _bss_size, %ecx
+	mov $_bss_start, %edi
+	mov $_bss_size, %ecx
+	cmp $0, %ecx
+	jz skip_bss_zero
 	shr $4, %ecx
 	rep stosl
+skip_bss_zero:
+
+	call pcboot_main
+	# pcboot_main never returns
+0:	cli
+	hlt
+	jmp 0b
+
+	# this is called once after memory init, to move the protected mode
+	# stack to the top of usable memory, to avoid interference from 16bit
+	# programs (as much as possible)
+	.global move_stack
+move_stack:
+	# calculate the currently used lowest address of the stack (rounded
+	# down to 4-byte alignment), to see where to start copying
+	mov %esp, %esi
+	and $0xfffffffc, %esi
+	# calculate the size we need to copy
+	mov $STACKTOP, %ecx
+	sub %esi, %ecx
+	# load the destination address to edi
+	mov 4(%esp), %edi
+	sub %ecx, %edi
+	# size in longwords
+	shr $2, %ecx
+
+	# change esp to the new stack
+	mov $STACKTOP, %ecx
+	sub %esp, %ecx
+	mov 4(%esp), %eax
+	mov %eax, %esp
+	sub %ecx, %esp
+
+	rep movsd
+	ret