From 0f82ae884f3ac2683db9fb4abd0d9be12bb83606 Mon Sep 17 00:00:00 2001
From: Perry Hung <iperry@gmail.com>
Date: Fri, 17 Sep 2010 03:57:52 -0400
Subject: Forgot to add exc.S

whoops.
---
 libmaple/exc.S | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 libmaple/exc.S

diff --git a/libmaple/exc.S b/libmaple/exc.S
new file mode 100644
index 0000000..541a61a
--- /dev/null
+++ b/libmaple/exc.S
@@ -0,0 +1,38 @@
+.text
+
+# On an exception, push a fake stack thread mode stack frame and redirect
+# thread execution to a thread mode error handler
+
+# From RM008:
+# The SP is decremented by eight words by the completion of the stack push.
+# Figure 5-1 shows the contents of the stack after an exception pre-empts the
+# current program flow.
+#
+# Old SP--> <previous>
+#           xPSR
+#           PC
+#           LR
+#           r12
+#           r3
+#           r2
+#           r1
+#    SP-->  r0
+
+.globl HardFaultException
+.thumb_func
+HardFaultException:
+   ldr r0, CPSR_MASK           @ Set default CPSR
+   push {r0}
+   ldr r0, TARGET_PC           @ Set target pc
+   push {r0}
+   sub sp, sp, #24             @ its not like i even care
+   ldr r0, EXC_RETURN          @ Return to thread mode
+   mov lr, r0
+   bx lr                       @ Exception exit
+
+ .align 4
+ CPSR_MASK:  .word 0x61000000
+ EXC_RETURN: .word 0xFFFFFFF9
+ TARGET_PC:  .word throb
+
+
-- 
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