Diff: myasm.s

Revision:

8:ad00c9036add

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/myasm.s	Thu Nov 09 14:43:39 2017 +0000
@@ -0,0 +1,29 @@
+    AREA asm_func, CODE, READONLY
+; Export my_asm function location so that C compiler can find it and link
+    EXPORT myasm
+myasm
+    
+    ; Write assmebler here
+    MOV R1, #0x20000000
+    BX      R1              ; THIS IS BAD
+    BX      LR
+    
+    EXPORT spinlock
+spinlock
+    LDREX   R1,[R0]     ;Read counter
+    SUBS    R1, #1      ;Subtract 1
+    ITT     PL          ;IF True True >= 0
+    STREXPL R2,R1,[R0]      ;TRY UPDATE
+    CMPPL   R2,#0           ;SUCCEED?
+    BNE     spinlock
+    BX      LR
+
+    EXPORT spinunlock
+spinunlock
+    LDREX   R1,[R0]
+    ADD     R1,#1
+    STREX   R2,R1,[R0]
+    CMP     R2,#0
+    BNE     spinunlock
+    BX      LR
+    END
\ No newline at end of file