+ /*
+ * To be called by C code which needs to do some operations with MMU
+ * disabled. Note that interrupts have to be disabled by the caller
+ * prior to calling us. The code called _MUST_ be in the RMO of course
+ * and part of the linear mapping as we don't attempt to translate the
+ * stack pointer at all. The function is called with the stack switched
+ * to this CPU emergency stack
+ *
+ * prototype is void *call_with_mmu_off(void *func, void *data);
+ *
+ * the called function is expected to be of the form
+ *
+ * void *called(void *data);
+ */
+_GLOBAL(call_with_mmu_off)
+ mflr r0 /* get link, save it on stackframe */
+ std r0,16(r1)
+ mr r1,r5 /* save old stack ptr */
+ ld r1,PACAEMERGSP(r13) /* get emerg. stack */
+ subi r1,r1,STACK_FRAME_OVERHEAD
+ std r0,16(r1) /* save link on emerg. stack */
+ std r5,0(r1) /* save old stack ptr in backchain */
+ ld r3,0(r3) /* get to real function ptr (assume same TOC) */
+ bl 2f /* we need LR to return, continue at label 2 */
+
+ ld r0,16(r1) /* we return here from the call, get LR and */
+ ld r1,0(r1) /* .. old stack ptr */
+ mtspr SPRN_SRR0,r0 /* and get back to virtual mode with these */
+ mfmsr r4
+ ori r4,r4,MSR_IR|MSR_DR
+ mtspr SPRN_SRR1,r4
+ rfid
+
+2: mtspr SPRN_SRR0,r3 /* coming from above, enter real mode */
+ mr r3,r4 /* get parameter */
+ mfmsr r0
+ ori r0,r0,MSR_IR|MSR_DR
+ xori r0,r0,MSR_IR|MSR_DR
+ mtspr SPRN_SRR1,r0
+ rfid
+