OpenRISC fixes for 4.18

Two fixes here which were breaking OpenRISC boot.
  - Fix bug in __pte_free_tlb() exposed in 4.18 by Matthew Wilcox's page
    table flag addition.
  - Fix issue booting on real hardware if delay slot detection emulation
    is disabled.
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Merge tag 'for-linus' of git://github.com/stffrdhrn/linux

Pull OpenRISC fixes from Stafford Horne:
 "Two fixes for issues which were breaking OpenRISC boot:

   - Fix bug in __pte_free_tlb() exposed in 4.18 by Matthew Wilcox's
     page table flag addition.

   - Fix issue booting on real hardware if delay slot detection
     emulation is disabled"

* tag 'for-linus' of git://github.com/stffrdhrn/linux:
  openrisc: entry: Fix delay slot exception detection
  openrisc: Call destructor during __pte_free_tlb

arch/openrisc/include/asm/pgalloc.h

@@ -98,8 +98,12 @@ static inline void pte_free(struct mm_struct *mm, struct page *pte)
 	__free_page(pte);
 }
 
+#define __pte_free_tlb(tlb, pte, addr)	\
+do {					\
+	pgtable_page_dtor(pte);		\
+	tlb_remove_page((tlb), (pte));	\
+} while (0)
 
-#define __pte_free_tlb(tlb, pte, addr) tlb_remove_page((tlb), (pte))
 #define pmd_pgtable(pmd) pmd_page(pmd)
 
 #define check_pgt_cache()          do { } while (0)

arch/openrisc/kernel/entry.S

@@ -277,12 +277,6 @@ EXCEPTION_ENTRY(_data_page_fault_handler)
 	l.addi  r3,r1,0                    // pt_regs
 	/* r4 set be EXCEPTION_HANDLE */   // effective address of fault
 
-	/*
-	 * __PHX__: TODO
-	 *
-	 * all this can be written much simpler. look at
-	 * DTLB miss handler in the CONFIG_GUARD_PROTECTED_CORE part
-	 */
 #ifdef CONFIG_OPENRISC_NO_SPR_SR_DSX
 	l.lwz   r6,PT_PC(r3)               // address of an offending insn
 	l.lwz   r6,0(r6)                   // instruction that caused pf
@@ -314,7 +308,7 @@ EXCEPTION_ENTRY(_data_page_fault_handler)
 
 #else
 
-	l.lwz   r6,PT_SR(r3)               // SR
+	l.mfspr r6,r0,SPR_SR               // SR
 	l.andi  r6,r6,SPR_SR_DSX           // check for delay slot exception
 	l.sfne  r6,r0                      // exception happened in delay slot
 	l.bnf   7f

arch/openrisc/kernel/head.S

@@ -210,8 +210,7 @@
  *	 r4  - EEAR     exception EA
  *	 r10 - current	pointing to current_thread_info struct
  *	 r12 - syscall  0, since we didn't come from syscall
- *	 r13 - temp	it actually contains new SR, not needed anymore
- *	 r31 - handler	address of the handler we'll jump to
+ *	 r30 - handler	address of the handler we'll jump to
  *
  *	 handler has to save remaining registers to the exception
  *	 ksp frame *before* tainting them!
@@ -244,6 +243,7 @@
 	/* r1 is KSP, r30 is __pa(KSP) */			;\
 	tophys  (r30,r1)					;\
 	l.sw    PT_GPR12(r30),r12				;\
+	/* r4 use for tmp before EA */				;\
 	l.mfspr r12,r0,SPR_EPCR_BASE				;\
 	l.sw    PT_PC(r30),r12					;\
 	l.mfspr r12,r0,SPR_ESR_BASE				;\
@@ -263,7 +263,10 @@
 	/* r12 == 1 if we come from syscall */			;\
 	CLEAR_GPR(r12)						;\
 	/* ----- turn on MMU ----- */				;\
-	l.ori	r30,r0,(EXCEPTION_SR)				;\
+	/* Carry DSX into exception SR */			;\
+	l.mfspr r30,r0,SPR_SR					;\
+	l.andi	r30,r30,SPR_SR_DSX				;\
+	l.ori	r30,r30,(EXCEPTION_SR)				;\
 	l.mtspr	r0,r30,SPR_ESR_BASE				;\
 	/* r30:	EA address of handler */			;\
 	LOAD_SYMBOL_2_GPR(r30,handler)				;\

arch/openrisc/kernel/traps.c

@@ -300,7 +300,7 @@ static inline int in_delay_slot(struct pt_regs *regs)
 		return 0;
 	}
 #else
-	return regs->sr & SPR_SR_DSX;
+	return mfspr(SPR_SR) & SPR_SR_DSX;
 #endif
 }