# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1485839477 -7200
# Node ID 54739a11be66dfbe19281b62b110a9f57db1bd7f
# Parent  51d1d6761601723f84e92d52fa202120fe05ca84
- .data copy and .bss clearing
- also made sure .data and .bss start and end markers are dword-aligned to make
  sure I can copy 4bytes at a time

diff -r 51d1d6761601 -r 54739a11be66 megadrive.ldscript
--- a/megadrive.ldscript	Mon Jan 30 16:57:51 2017 +0200
+++ b/megadrive.ldscript	Tue Jan 31 07:11:17 2017 +0200
@@ -21,23 +21,26 @@
 	.rodata : { * (.rodata); } >rom
 
 	/* place the load address of the .data section after .rodata */
+	. = ALIGN(4);
 	_data_lma = .;
 	_rom_end = _data_lma + _data_size;
 
 	/* ---- start of RAM ---- */
 	. = 0xff0000;
 	/* place the .data section at the start of RAM */
-	.data : AT (_data_lma) {
+	.data ALIGN(4): AT (_data_lma) {
 		_data_start = .;
 		* (.data);
+		. = ALIGN(4);
 		_data_end = .;
 	} >ram
 	_data_size = SIZEOF(.data);
 
 	/* place the .bss section at the end */
-	.bss : {
+	.bss ALIGN(4): {
 		_bss_start = .;
 		* (.bss);
+		. = ALIGN(4);
 		_bss_end = .;
 	} >ram
 	_bss_size = SIZEOF(.bss);
diff -r 51d1d6761601 -r 54739a11be66 src/startup.s
--- a/src/startup.s	Mon Jan 30 16:57:51 2017 +0200
+++ b/src/startup.s	Tue Jan 31 07:11:17 2017 +0200
@@ -1,8 +1,27 @@
-| TODO: copy .data and zero .bss
 	.text
 	.extern main
 
 	.global start
 start:
+	| copy .data section from ROM to RAM
+	move.l #_data_lma, %a0
+	move.l #_data_start, %a1
+	move.l #_data_end, %a2
+	cmp.l %a1, %a2
+	beq.s 1f	| skip data copy if the section is empty
+0:	move.l (%a0)+, (%a1)+
+	cmp.l %a1, %a2
+	bne.s 0b
+1:
+
+	| zero the .bss section
+	move.l #_bss_start, %a0
+	move.l #_bss_end, %a1
+	cmp.l %a0, %a1
+	beq.s 1f	| skip bss zeroing if the section is empty
+0:	clr.l (%a0)+
+	cmp.l %a0, %a1
+	bne.s 0b
+1:
 	jsr main
 	stop #0x2700