From 086f9155f793cc3683af6abb37f1bc7fc0442551 Mon Sep 17 00:00:00 2001
From: Steins7 <steinsset@gmail.com>
Date: Mon, 18 Sep 2023 11:45:12 +0200
Subject: [PATCH] Fix RAM initialisation

The reset handler is responsible for loading the variables default values. This
includes variables initialized to 0, although they are handed through bss and
not data
---
 linker.ld |  3 +++
 startup.s | 24 ++++++++++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/linker.ld b/linker.ld
index 4f30b65..55cadad 100644
--- a/linker.ld
+++ b/linker.ld
@@ -64,7 +64,10 @@ SECTIONS
 	.bss :
 	{
 		. = ALIGN(4);
+		_sbss = .;
 		*(.bss)
+		. = ALIGN(4);
+		_ebss = .;
 	} > RAM
 
 	/* memory space allocated to stack. The stack is situated at the very end of
diff --git a/startup.s b/startup.s
index 3a3b5a1..8f48739 100644
--- a/startup.s
+++ b/startup.s
@@ -34,19 +34,35 @@ hdr_reset:
 	ldr r1, = _sdata
 	ldr r2, = _edata
 	subs r2, r2, r1
-	bcc startup_init_end
+	bcc data_init_end
 	ldr r3, = _sromdata
 
 	movs r0, #0
 
-startup_init_loop:
+data_init_loop:
 	ldr r4, [r3, r0]
 	str r4, [r1, r0]
 	adds r0, r0, #4
 	cmp r0, r2
-	bcc startup_init_loop
+	bcc data_init_loop
 
-startup_init_end:
+data_init_end:
+//initialize RAM to zero
+	ldr r1, = _sbss
+	ldr r2, = _ebss
+	subs r2, r2, r1
+	bcc bss_init_end
+	movs r3, #0
+
+	movs r0, #0
+
+bss_init_loop:
+	str r3, [r1, r0]
+	adds r0, r0, #4
+	cmp r0, r2
+	bcc bss_init_loop
+
+bss_init_end:
 	b main
 	b hdr_reset