Sets the processor to Supervisor mode and disables all interrupts
by setting both interrupt mask bits in the new CPSR.
With a debug hardware unit, such as ARM
RVI™ debug unit or ARM DSTREAM™ debug
and trace unit:
the User stack pointer,
R13_USR, is copied to the Supervisor mode stack pointer,R13_SVCthe I and F bits in the current
CPSRare set, which disables normal and fast interrupts.
Note
If debugging with RealView ARMulator ISS:
R0is set to zero indicating that no function is available for returning to User modethe User mode stack pointer is not copied to the Supervisor mode stack pointer.
EntryOn exit, R0 contains the address of a function
to be called to return to User mode. The function has the following
prototype:
void ReturnToUSR(void)
If EnterSVC is called in User mode, this
routine returns the caller to User mode and restores the interrupt
flags. Otherwise, the action of this routine is undefined.
If entered in User mode, the Supervisor mode stack is lost
as a result of copying the user stack pointer. The return to User
routine restores R13_SVC to the Supervisor mode
stack value, but this stack must not be used by applications.
After executing the SVC, the current link register is R14_SVC,
not R14_USR. If the value of R14_USR is
required after the call, it must be pushed onto the stack before
the call and popped afterwards, as for a BL function
call.
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