powerpc/nohash: Add _PAGE_WRITE to supplement _PAGE_RW

Several places, _PAGE_RW maps to write permission and don't
always imply read. To make it more clear, do as book3s/64 in
commit c7d54842 ("powerpc/mm: Use _PAGE_READ to indicate
Read access") and use _PAGE_WRITE when more relevant.

For the time being _PAGE_WRITE is equivalent to _PAGE_RW but that
will change when _PAGE_READ gets added in following patches.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/1f79b88db54d030ada776dc9845e0e88345bfc28.1695659959.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/nohash/32/pte-40x.h

@@ -49,6 +49,8 @@
 #define _PAGE_EXEC	0x200	/* hardware: EX permission */
 #define _PAGE_ACCESSED	0x400	/* software: R: page referenced */
 
+#define _PAGE_WRITE	_PAGE_RW
+
 /* No page size encoding in the linux PTE */
 #define _PAGE_PSIZE		0
 

arch/powerpc/include/asm/nohash/32/pte-44x.h

@@ -75,6 +75,8 @@
 #define _PAGE_NO_CACHE	0x00000400		/* H: I bit */
 #define _PAGE_WRITETHRU	0x00000800		/* H: W bit */
 
+#define _PAGE_WRITE	_PAGE_RW
+
 /* No page size encoding in the linux PTE */
 #define _PAGE_PSIZE		0
 

arch/powerpc/include/asm/nohash/32/pte-85xx.h

@@ -31,6 +31,8 @@
 #define _PAGE_WRITETHRU	0x00400	/* H: W bit */
 #define _PAGE_SPECIAL	0x00800 /* S: Special page */
 
+#define _PAGE_WRITE	_PAGE_RW
+
 #define _PAGE_KERNEL_RO		0
 #define _PAGE_KERNEL_ROX	_PAGE_EXEC
 #define _PAGE_KERNEL_RW		(_PAGE_DIRTY | _PAGE_RW)

arch/powerpc/include/asm/nohash/64/pgtable.h

@@ -149,7 +149,7 @@ static inline void p4d_set(p4d_t *p4dp, unsigned long val)
 static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
 					   unsigned long addr, pte_t *ptep)
 {
-	pte_update(mm, addr, ptep, _PAGE_RW, 0, 1);
+	pte_update(mm, addr, ptep, _PAGE_WRITE, 0, 1);
 }
 
 #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH

arch/powerpc/include/asm/nohash/pgtable.h

@@ -84,7 +84,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
 static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 				      pte_t *ptep)
 {
-	pte_update(mm, addr, ptep, _PAGE_RW, 0, 0);
+	pte_update(mm, addr, ptep, _PAGE_WRITE, 0, 0);
 }
 #endif
 #define __HAVE_ARCH_PTEP_SET_WRPROTECT
@@ -122,6 +122,9 @@ static inline void __ptep_set_access_flags(struct vm_area_struct *vma,
 #ifndef pte_mkwrite_novma
 static inline pte_t pte_mkwrite_novma(pte_t pte)
 {
+	/*
+	 * write implies read, hence set both
+	 */
 	return __pte(pte_val(pte) | _PAGE_RW);
 }
 #endif
@@ -139,7 +142,7 @@ static inline pte_t pte_mkyoung(pte_t pte)
 #ifndef pte_wrprotect
 static inline pte_t pte_wrprotect(pte_t pte)
 {
-	return __pte(pte_val(pte) & ~_PAGE_RW);
+	return __pte(pte_val(pte) & ~_PAGE_WRITE);
 }
 #endif
 
@@ -153,7 +156,7 @@ static inline pte_t pte_mkexec(pte_t pte)
 #ifndef pte_write
 static inline int pte_write(pte_t pte)
 {
-	return pte_val(pte) & _PAGE_RW;
+	return pte_val(pte) & _PAGE_WRITE;
 }
 #endif
 #ifndef pte_read

arch/powerpc/include/asm/nohash/pte-e500.h

@@ -55,6 +55,8 @@
 #define _PAGE_KERNEL_ROX	(_PAGE_BAP_SR | _PAGE_BAP_SX)
 #define _PAGE_USER		(_PAGE_BAP_UR | _PAGE_BAP_SR) /* Can be read */
 
+#define _PAGE_WRITE	_PAGE_RW
+
 #define _PAGE_SPECIAL	_PAGE_SW0
 
 /* Base page size */

arch/powerpc/kernel/head_40x.S

@@ -316,9 +316,9 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt)
 	andc.	r9, r9, r11		/* Check permission */
 	bne	5f
 
-	rlwinm	r9, r11, 1, _PAGE_RW	/* dirty => rw */
-	and	r9, r9, r11		/* hwwrite = dirty & rw */
-	rlwimi	r11, r9, 0, _PAGE_RW	/* replace rw by hwwrite */
+	rlwinm	r9, r11, 1, _PAGE_WRITE	/* dirty => w */
+	and	r9, r9, r11		/* hwwrite = dirty & w */
+	rlwimi	r11, r9, 0, _PAGE_WRITE	/* replace w by hwwrite */
 
 	/* Create TLB tag.  This is the faulting address plus a static
 	 * set of bits.  These are size, valid, E, U0.
@@ -400,9 +400,9 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt)
 	andc.	r9, r9, r11		/* Check permission */
 	bne	5f
 
-	rlwinm	r9, r11, 1, _PAGE_RW	/* dirty => rw */
-	and	r9, r9, r11		/* hwwrite = dirty & rw */
-	rlwimi	r11, r9, 0, _PAGE_RW	/* replace rw by hwwrite */
+	rlwinm	r9, r11, 1, _PAGE_WRITE	/* dirty => w */
+	and	r9, r9, r11		/* hwwrite = dirty & w */
+	rlwimi	r11, r9, 0, _PAGE_WRITE	/* replace w by hwwrite */
 
 	/* Create TLB tag.  This is the faulting address plus a static
 	 * set of bits.  These are size, valid, E, U0.

arch/powerpc/kernel/head_44x.S

@@ -342,7 +342,7 @@ interrupt_base:
 	mtspr	SPRN_MMUCR,r12
 
 	/* Mask of required permission bits. Note that while we
-	 * do copy ESR:ST to _PAGE_RW position as trying to write
+	 * do copy ESR:ST to _PAGE_WRITE position as trying to write
 	 * to an RO page is pretty common, we don't do it with
 	 * _PAGE_DIRTY. We could do it, but it's a fairly rare
 	 * event so I'd rather take the overhead when it happens
@@ -586,7 +586,7 @@ finish_tlb_load_44x:
 4:	mtspr	SPRN_MMUCR,r12		/* Set MMUCR */
 
 	/* Mask of required permission bits. Note that while we
-	 * do copy ESR:ST to _PAGE_RW position as trying to write
+	 * do copy ESR:ST to _PAGE_WRITE position as trying to write
 	 * to an RO page is pretty common, we don't do it with
 	 * _PAGE_DIRTY. We could do it, but it's a fairly rare
 	 * event so I'd rather take the overhead when it happens

arch/powerpc/kernel/head_85xx.S

@@ -471,7 +471,7 @@ END_BTB_FLUSH_SECTION
 
 4:
 	/* Mask of required permission bits. Note that while we
-	 * do copy ESR:ST to _PAGE_RW position as trying to write
+	 * do copy ESR:ST to _PAGE_WRITE position as trying to write
 	 * to an RO page is pretty common, we don't do it with
 	 * _PAGE_DIRTY. We could do it, but it's a fairly rare
 	 * event so I'd rather take the overhead when it happens

arch/powerpc/mm/nohash/e500.c

@@ -117,7 +117,7 @@ static void settlbcam(int index, unsigned long virt, phys_addr_t phys,
 	TLBCAM[index].MAS2 |= (flags & _PAGE_ENDIAN) ? MAS2_E : 0;
 
 	TLBCAM[index].MAS3 = (phys & MAS3_RPN) | MAS3_SR;
-	TLBCAM[index].MAS3 |= (flags & _PAGE_RW) ? MAS3_SW : 0;
+	TLBCAM[index].MAS3 |= (flags & _PAGE_WRITE) ? MAS3_SW : 0;
 	if (mmu_has_feature(MMU_FTR_BIG_PHYS))
 		TLBCAM[index].MAS7 = (u64)phys >> 32;
 
@@ -125,7 +125,7 @@ static void settlbcam(int index, unsigned long virt, phys_addr_t phys,
 	if (!is_kernel_addr(virt)) {
 		TLBCAM[index].MAS3 |= MAS3_UR;
 		TLBCAM[index].MAS3 |= (flags & _PAGE_EXEC) ? MAS3_UX : 0;
-		TLBCAM[index].MAS3 |= (flags & _PAGE_RW) ? MAS3_UW : 0;
+		TLBCAM[index].MAS3 |= (flags & _PAGE_WRITE) ? MAS3_UW : 0;
 	} else {
 		TLBCAM[index].MAS3 |= (flags & _PAGE_EXEC) ? MAS3_SX : 0;
 	}