SRS
Store Return State onto a stack.
Syntax
SRS{addr_modecondmodenum
SRS{addr_modecondmodenum
where:
addr_modeis any one of the following:
IAIncrement address After each transfer
IBIncrement address Before each transfer (A32 only)
DADecrement address After each transfer (A32 only)
DBDecrement address Before each transfer (Full Descending stack).
If
addr_modecondis an optional condition code.
Note
condITinstruction, but this is deprecated in ARMv8. This is an unconditional instruction in A32.!is an optional suffix. If ! is present, the final address is written back into the SP of the mode specified by
modenummodenumspecifies the number of the mode whose banked SP is used as the base register. You must use only the defined mode numbers.
Operation
SRS stores the LR and the SPSR
of the current mode, at the address contained in SP of the mode specified
by modenummodenumSTM instruction
for stack accesses.
Note
For full descending stack, you must useSRSFD or SRSDB.Usage
You can use SRS to store return
state for an exception handler on a different stack from the one automatically
selected.
Notes
Where addresses are not word-aligned, SRS ignores
the least significant two bits of the specified address.
The time order of the accesses to individual words of memory
generated by SRS is not architecturally
defined. Do not use this instruction on memory-mapped I/O locations
where access order matters.
Do not use SRS in User and System
modes because these modes do not have a SPSR.
SRS is not permitted in a non-secure state if
modenum
Availability
This 32-bit instruction is available in A32 and T32.
There is no 16-bit version of this instruction in T32.
Example
R13_usr EQU 16
SRSFD sp,#R13_usr