The header <__armlib.h> defines a number of useful ARM specific functions.

Interrupt functions
__ARMLIB_enableIRQ | Enable IRQ interrupts.
__ARMLIB_disableIRQ | Disable IRQ interrupts.
__ARMLIB_isrEnableIRQ | Re-enable IRQ interrupts from within an IRQ ISR.
__ARMLIB_isrDisableIRQ | Re-disable IRQ interrupts from within an IRQ ISR.
__ARMLIB_enableFIQ | Enable FIQ interrupts.
__ARMLIB_disableFIQ | Disable FIQ interrupts.
Debug I/O functions
__ARMLIB_commTX | Send a word of data down the ARM debug communications channel.
__ARMLIB_commRX | Read a word of data from the ARM debug communications channel.
__ARMLIB_runCommPortServer | Serve ARMCPS commands from the ARM's debug communications channel.
Miscellaneous Functions
__ARMLIB_crc32 | Compute a CRC-32 checksum of a block of data.