From 2ff96443107914a1233284db6b67a32e3057393d Mon Sep 17 00:00:00 2001
From: Corwin Kuiper <corwin@kuiper.dev>
Date: Wed, 23 Jun 2021 19:06:24 +0100
Subject: [PATCH] disable interrupts during the interrupt handler

---
 agb/interrupt_simple.s | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/agb/interrupt_simple.s b/agb/interrupt_simple.s
index 817fd0b1..c86495a5 100644
--- a/agb/interrupt_simple.s
+++ b/agb/interrupt_simple.s
@@ -3,33 +3,43 @@
     .global InterruptHandlerSimple
     .align
 InterruptHandlerSimple:
-    ldr r2, =0x04000200 @ interrupt enable register location
-    ldrh r1, [r2] @ load 16 bit interrupt enable to r1
-    ldrh r3, [r2, #2] @ load 16 bit interrupt request to r3
+    ldr r4, =0x04000200 @ interrupt enable register location
+
+    @ disable interrupts by setting bit 0 to 0
+    strh r2, [r4, #8]
+
+    ldrh r1, [r4] @ load 16 bit interrupt enable to r1
+    ldrh r3, [r4, #2] @ load 16 bit interrupt request to r3
     and r0, r1, r3 @ interrupts both enabled and requested
-    strh r0, [r2, #2] @ store to interrupt request
+    strh r0, [r4, #2] @ store to interrupt request
 
     ldr r2, =0x03007FF8 @ load bios interrupt request location
     ldrh r1, [r2] @ load bios interrupt requests
     orr r1, r1, r0 @ or with enabled and requested interrupts
     strh r1, [r2] @ acknowlege bios requests
 
+    @ change to user mode
     mrs r2, cpsr
     orr r2, r2, #0xD
     msr cpsr_c, r2
 
-
+    @ call the rust interrupt handler with r0 set to the triggered interrupts
     ldr r1, =__RUST_INTERRUPT_HANDLER
-    push {lr}
+    push {lr, r4}
     adr lr, .IReturn
     bx r1
 .IReturn:
-    pop {lr}
+    pop {lr, r4}
 
+    @ change back to interuupt mode
     mrs r2, cpsr
     bic r2, r2, #0xD
     orr r2, r2, #0x92
     msr cpsr_c, r2
 
+    @ reenable interrupts by setting bit 0 to 1
+    mov r0, #1
+    strh r0, [r4, #8]
+
     bx lr @ return to bios
 .pool