about Keil MDK "step-out" in debug mode

Hi

I use ULINK2 to debug S3C2440. I notice that the start-up code provided by Keil S3C2440.s, it change the cpu mode one by one to setup the stack, and finally enter the user mode then jump to the C code:

; Setup Stack for each mode ----------------------------------------------------

                LDR     R0, =Stack_Top
                MOV     SP, R0

;  Enter Undefined Instruction Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_UND:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #UND_Stack_Size

;  Enter Abort Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_ABT:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #ABT_Stack_Size

;  Enter FIQ Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_FIQ:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #FIQ_Stack_Size

;  Enter IRQ Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_IRQ:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #IRQ_Stack_Size

;  Enter Supervisor Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_SVC:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #SVC_Stack_Size

;  Enter User Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_USR
                MOV     SP, R0
                SUB     SL, SP, #USR_Stack_Size

;  Enter User Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_USR
                IF      :DEF:__MICROLIB

                EXPORT __initial_sp

                ELSE

                MOV     SP, R0
                SUB     SL, SP, #USR_Stack_Size

                ENDIF

; Enter the C code -------------------------------------------------------------

                IMPORT  __main
                LDR     R0, =__main
                BX      R0

but in my application i don't want to enter the user-mode before jump to the C code becase i need to do some MMU operation in the main() function. so i modified the S3C2440.s as follow:

;  Enter Supervisor Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_SVC:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #SVC_Stack_Size

;-----------------------------------------------------------
;  Not Enter User Mode and set its Stack Pointer
;                MSR     CPSR_c, #Mode_USR
;                MOV     SP, R0
;                SUB     SL, SP, #USR_Stack_Size
;-----------------------------------------------------------

;  Enter User Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_USR
                IF      :DEF:__MICROLIB

                EXPORT __initial_sp

                ELSE

                MOV     SP, R0
                SUB     SL, SP, #USR_Stack_Size

                ENDIF

; Enter the C code -------------------------------------------------------------

                IMPORT  __main
                LDR     R0, =__main
                BX      R0

My program works well, but when i debug the code, it seems that the "Step-Out" function provided by the Keil IDE do not work, the program did not stop in the next instruction after one function return, it just continue running until i press the "Stop" button or insert a new breakpoint. But this did not happen in the original version of S3C2440.s without my modification.

Is there anything wrong in my code?

Any suggestion will be appreciated!

Eric