fix: Fix kernel page fault exception handling causing system exception.

Close #I3RAN4

Change-Id: Ice9bc67371ad85476ec99b46b7555d41abd93e94

arch/arm/arm/src/los_hw_exc.S

@@ -181,6 +181,7 @@ _osExceptUndefInstrHdl:
     MOV     R2, #0
     MOV     R3, #0
     STMFD   SP!, {R2-R3}                                      @ far and fsr fields, are 0 under this anomaly
+    STMFD   SP!, {R4-R11}
 
     MOV     R0, #OS_EXCEPT_UNDEF_INSTR                        @ Set exception ID to OS_EXCEPT_UNDEF_INSTR.
     B       _osExceptDispatch                                 @ Branch to global exception handler.
@@ -240,6 +241,7 @@ _osKernelSVCHandler:
     MOV     R0, #0
     STR     R0, [SP, #0]
     STR     R0, [SP, #4]
+    STMFD   SP!, {R4-R11}
     MOV     R0, #OS_EXCEPT_SWI                               @ Set exception ID to OS_EXCEPT_SWI.
     B       _osExceptDispatch                                @ Branch to global exception handler.
 
@@ -261,9 +263,10 @@ _osExceptPrefetchAbortHdl:
     MRC     P15, 0, R2, C6, C0, 2
     MRC     P15, 0, R3, C5, C0, 1
     STMFD   SP!, {R2-R3}                                     @ Save far and fsr
+    STMFD   SP!, {R4-R11}
 
 #ifdef LOSCFG_KERNEL_VM
-    LDR     R0, [SP, #(11 * 4)]
+    LDR     R0, [SP, #(19 * 4)]
     AND     R0, R0, #CPSR_MASK_MODE                          @ Interrupted mode
     CMP     R0, #CPSR_USER_MODE                              @ User mode
     BNE     _osKernelExceptPrefetchAbortHdl
@@ -302,6 +305,7 @@ _osExceptDataAbortHdl:
     MRC     P15, 0, R2, C6, C0, 0
     MRC     P15, 0, R3, C5, C0, 0
     STMFD   SP!, {R2-R3}                                     @ Save far and fsr
+    STMFD   SP!, {R4-R11}
 
 #ifdef LOSCFG_KERNEL_VM
     MOV    R1, SP
@@ -320,6 +324,7 @@ _osExceptDataAbortHdl:
 
 #ifdef LOSCFG_KERNEL_VM
 _osExcPageFaultReturn:
+    LDMFD  SP!, {R4-R11}
     ADD    SP, SP, #(2 * 4)
     LDMFD  SP, {R13, R14}^
     ADD    SP, SP, #(2 * 4)                                  @ Jump reserved fileds
@@ -340,6 +345,7 @@ _osExceptAddrAbortHdl:
     MOV     R2, #0
     MOV     R3, #0
     STMFD   SP!, {R2-R3}                                     @ far and fsr fields, are 0 under this anomaly
+    STMFD   SP!, {R4-R11}
 
     MOV     R0, #OS_EXCEPT_ADDR_ABORT                        @ Set exception ID to OS_EXCEPT_ADDR_ABORT.
     B       _osExceptDispatch                                @ Branch to global exception handler.
@@ -357,12 +363,12 @@ _osExceptFiqHdl:
     MOV     R2, #0
     MOV     R3, #0
     STMFD   SP!, {R2-R3}                                     @ far and fsr fields, are 0 under this anomaly
+    STMFD   SP!, {R4-R11}
 
 @ Description: Exception handler
 @ Parameter  : R0     Exception Type
 @ Regs Hold  : R3     Exception`s CPSR
 _osExceptDispatch:
-    STMFD   SP!, {R4-R11}
     LDR     R8, [SP, #(8 * 4)]                               @ Get far
     LDR     R9, [SP, #(9 * 4)]                               @ Get fsr