trezor-firmware/core/embed/trezorhal/supervise.h

// supervisor call functions

#define SVC_ENABLE_IRQ 0
#define SVC_DISABLE_IRQ 1
#define SVC_SET_PRIORITY 2

inline void svc_enableIRQ(uint32_t IRQn) {
  register uint32_t r0 __asm__("r0") = IRQn;
  __asm__ __volatile__("svc %0" ::"i"(SVC_ENABLE_IRQ), "r"(r0) : "memory");
}

inline void svc_disableIRQ(uint32_t IRQn) {
  register uint32_t r0 __asm__("r0") = IRQn;
  __asm__ __volatile__("svc %0" ::"i"(SVC_DISABLE_IRQ), "r"(r0) : "memory");
}

inline void svc_setpriority(uint32_t IRQn, uint32_t priority) {
  register uint32_t r0 __asm__("r0") = IRQn;
  register uint32_t r1 __asm__("r1") = priority;
  __asm__ __volatile__("svc %0" ::"i"(SVC_SET_PRIORITY), "r"(r0), "r"(r1)
                       : "memory");
}