[PATCH 07/14] powerpc/mm: Update _PAGE_KERNEL_RO

[Aneesh Kumar K.V]

PS3 had used PPP bit hack to implement a read only mapping in the
kernel area. Since we are bolt mapping the ioremap area, it used
the pte flags _PAGE_PRESENT | _PAGE_USER to get a PPP value of 0x3
there by resulting in a read only mapping. This means the area
can be accessed by user space, but kernel will never return such an
address to user space.

Fix this by doing a read only kernel mapping using PPP bits 0b110

This also allows us to do read only kernel mapping for radix in later
patches.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/hash.h |  4 ++--
 arch/powerpc/mm/hash_utils_64.c           | 17 +++++++++++------
 arch/powerpc/platforms/ps3/spu.c          |  2 +-
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 8ccb2970f30f..c2b567456796 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -115,10 +115,10 @@
 #endif /* CONFIG_PPC_MM_SLICES */
 
 /*
- * No separate kernel read-only, user access blocked by key
+ * user access blocked by key
  */
 #define _PAGE_KERNEL_RW		(_PAGE_PRIVILEGED | _PAGE_RW | _PAGE_DIRTY)
-#define _PAGE_KERNEL_RO		 _PAGE_KERNEL_RW
+#define _PAGE_KERNEL_RO		 (_PAGE_PRIVILEGED | _PAGE_READ)
 #define _PAGE_KERNEL_RWX	(_PAGE_PRIVILEGED | _PAGE_DIRTY | \
 				 _PAGE_RW | _PAGE_EXEC)
 
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 630603f74056..c81c08aaff0e 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -167,14 +167,19 @@ unsigned long htab_convert_pte_flags(unsigned long pteflags)
 	if ((pteflags & _PAGE_EXEC) == 0)
 		rflags |= HPTE_R_N;
 	/*
-	 * PP bits:
+	 * PPP bits:
 	 * Linux uses slb key 0 for kernel and 1 for user.
-	 * kernel areas are mapped with PP=00
-	 * and there is no kernel RO (_PAGE_KERNEL_RO).
-	 * User area is mapped with PP=0x2 for read/write
-	 * or PP=0x3 for read-only (including writeable but clean pages).
+	 * kernel RW areas are mapped with PPP=0b000
+	 * User area is mapped with PPP=0b010 for read/write
+	 * or PPP=0b011 for read-only (including writeable but clean pages).
 	 */
-	if (!(pteflags & _PAGE_PRIVILEGED)) {
+	if (pteflags & _PAGE_PRIVILEGED) {
+		/*
+		 * Kernel read only mapped with ppp bits 0b110
+		 */
+		if (!(pteflags & _PAGE_WRITE))
+			rflags |= (HPTE_R_PP0 | 0x2);
+	} else {
 		if (pteflags & _PAGE_RWX)
 			rflags |= 0x2;
 		if (!((pteflags & _PAGE_WRITE) && (pteflags & _PAGE_DIRTY)))
diff --git a/arch/powerpc/platforms/ps3/spu.c b/arch/powerpc/platforms/ps3/spu.c
index a0bca05e26b0..5e8a40f9739f 100644
--- a/arch/powerpc/platforms/ps3/spu.c
+++ b/arch/powerpc/platforms/ps3/spu.c
@@ -205,7 +205,7 @@ static void spu_unmap(struct spu *spu)
 static int __init setup_areas(struct spu *spu)
 {
 	struct table {char* name; unsigned long addr; unsigned long size;};
-	static const unsigned long shadow_flags = _PAGE_NO_CACHE | 3;
+	unsigned long shadow_flags = pgprot_val(pgprot_noncached_wc(PAGE_KERNEL_RO));
 
 	spu_pdata(spu)->shadow = __ioremap(spu_pdata(spu)->shadow_addr,
 					   sizeof(struct spe_shadow),
-- 
2.5.0