From 21c6fe3075bf31da11e4d9a2f98eaf98a684664d Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Sat, 5 Feb 2022 00:12:59 -0700
Subject: Fixed undefined handler

---
 src/exceptions/undefined.S |  3 +--
 src/sys/kernel.S           | 22 ++++++++--------------
 2 files changed, 9 insertions(+), 16 deletions(-)

(limited to 'src')

diff --git a/src/exceptions/undefined.S b/src/exceptions/undefined.S
index b8eab29..ef00735 100644
--- a/src/exceptions/undefined.S
+++ b/src/exceptions/undefined.S
@@ -17,8 +17,7 @@ undefined:
 	ldr r2, =undefined_at
 	bl draw_string
 	// Output lr
-	mov r1, #0x1000
-	ldr r0, [r1, #-4]
+	ldr r0, [sp, #0x34]
 	sub r2, r0, #4
 	mov r0, #31
 	mov r1, #17
diff --git a/src/sys/kernel.S b/src/sys/kernel.S
index 93074b6..119a00d 100644
--- a/src/sys/kernel.S
+++ b/src/sys/kernel.S
@@ -3,20 +3,14 @@
 .globl kernel_main
 kernel_main:
 	bl sysinit
-	// ///https://wiki.osdev.org/ARM_Paging
-	// // Query the ID_MMFR0 register
-	// mrc p15, 0, r0, c0, c1, 4
-	// bl uart_hexn
-	// // Switch to user mode
-	// cps #0x10
-	// // Intentional undefined instruction
-	// //.word 0xf7f0a000
-	// // This will fail in user mode
-	// mrc p15, 3, r0, c15, c0, 0
-	// // Supervisor Call #1 - Does nothing special
-	// svc #1
-	// mrs r0, cpsr
-	// bl uart_hexn
+	///https://wiki.osdev.org/ARM_Paging
+	// Query the ID_MMFR0 register
+	mrc p15, 0, r2, c0, c1, 4
+	mov r0, #0
+	mov r1, #7
+	bl draw_hex32
+	// Intentional undefined instruction
+	// .word 0xf7f0a000
 	cpsie aif, #0x10
 	svc #2 // Start scheduling!
 1:
-- 
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