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-rw-r--r--libmaple/exc.S38
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+.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
+
+