powerpc/e500: Introduce _PAGE_READ and remove _PAGE_USER

e500 MMU has 6 page protection bits:
- R, W, X for supervisor
- R, W, X for user

It means that it can support X without R.

To do that, _PAGE_READ flag is needed.

With 32 bits PTE there is no bit available for it in PTE. On the
other hand the only real use of _PAGE_USER is to implement PAGE_NONE
by clearing _PAGE_USER. As _PAGE_NONE can also be implemented by
clearing _PAGE_READ, remove _PAGE_USER and add _PAGE_READ. Move
_PAGE_PRESENT into bit 30 so that _PAGE_READ can match SR bit.

With 64 bits PTE _PAGE_USER is already the combination of SR and UR
so all we need to do is to rename it _PAGE_READ.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/0849ab6bf7ae2af23f94b0457fa40d0ea3983fe4.1695659959.git.christophe.leroy@csgroup.eu

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

@@ -17,9 +17,9 @@
 */
 
 /* Definitions for FSL Book-E Cores */
-#define _PAGE_PRESENT	0x00001	/* S: PTE contains a translation */
-#define _PAGE_USER	0x00002	/* S: User page (maps to UR) */
-#define _PAGE_RW	0x00004	/* S: Write permission (SW) */
+#define _PAGE_READ	0x00001	/* H: Read permission (SR) */
+#define _PAGE_PRESENT	0x00002	/* S: PTE contains a translation */
+#define _PAGE_WRITE	0x00004	/* S: Write permission (SW) */
 #define _PAGE_DIRTY	0x00008	/* S: Page dirty */
 #define _PAGE_EXEC	0x00010	/* H: SX permission */
 #define _PAGE_ACCESSED	0x00020	/* S: Page referenced */
@@ -31,13 +31,6 @@
 #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)
-#define _PAGE_KERNEL_RWX	(_PAGE_DIRTY | _PAGE_RW | _PAGE_EXEC)
-
 /* No page size encoding in the linux PTE */
 #define _PAGE_PSIZE		0
 
@@ -63,14 +56,7 @@
 #define _PAGE_BASE	(_PAGE_BASE_NC)
 #endif
 
-/* Permission masks used to generate the __P and __S table */
-#define PAGE_NONE	__pgprot(_PAGE_BASE)
-#define PAGE_SHARED	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW)
-#define PAGE_SHARED_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW | _PAGE_EXEC)
-#define PAGE_COPY	__pgprot(_PAGE_BASE | _PAGE_USER)
-#define PAGE_COPY_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
-#define PAGE_READONLY	__pgprot(_PAGE_BASE | _PAGE_USER)
-#define PAGE_READONLY_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
+#include <asm/pgtable-masks.h>
 
 #endif /* __KERNEL__ */
 #endif /*  _ASM_POWERPC_NOHASH_32_PTE_FSL_85xx_H */

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

@@ -48,14 +48,19 @@
 
 /* "Higher level" linux bit combinations */
 #define _PAGE_EXEC		(_PAGE_BAP_SX | _PAGE_BAP_UX) /* .. and was cache cleaned */
-#define _PAGE_RW		(_PAGE_BAP_SW | _PAGE_BAP_UW) /* User write permission */
+#define _PAGE_READ		(_PAGE_BAP_SR | _PAGE_BAP_UR) /* User read permission */
+#define _PAGE_WRITE		(_PAGE_BAP_SW | _PAGE_BAP_UW) /* User write permission */
+
 #define _PAGE_KERNEL_RW		(_PAGE_BAP_SW | _PAGE_BAP_SR | _PAGE_DIRTY)
 #define _PAGE_KERNEL_RO		(_PAGE_BAP_SR)
 #define _PAGE_KERNEL_RWX	(_PAGE_BAP_SW | _PAGE_BAP_SR | _PAGE_DIRTY | _PAGE_BAP_SX)
 #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_NA	0
+#define _PAGE_RO	_PAGE_READ
+#define _PAGE_ROX	(_PAGE_READ | _PAGE_BAP_UX)
+#define _PAGE_RW	(_PAGE_READ | _PAGE_WRITE)
+#define _PAGE_RWX	(_PAGE_READ | _PAGE_WRITE | _PAGE_BAP_UX)
 
 #define _PAGE_SPECIAL	_PAGE_SW0
 
@@ -90,14 +95,7 @@
 #define _PAGE_BASE	(_PAGE_BASE_NC)
 #endif
 
-/* Permission masks used to generate the __P and __S table */
-#define PAGE_NONE	__pgprot(_PAGE_BASE)
-#define PAGE_SHARED	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW)
-#define PAGE_SHARED_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW | _PAGE_BAP_UX)
-#define PAGE_COPY	__pgprot(_PAGE_BASE | _PAGE_USER)
-#define PAGE_COPY_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_BAP_UX)
-#define PAGE_READONLY	__pgprot(_PAGE_BASE | _PAGE_USER)
-#define PAGE_READONLY_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_BAP_UX)
+#include <asm/pgtable-masks.h>
 
 #ifndef __ASSEMBLY__
 static inline pte_t pte_mkexec(pte_t pte)

arch/powerpc/kernel/head_85xx.S

@@ -485,10 +485,10 @@ END_BTB_FLUSH_SECTION
 	 */
 	mfspr	r12,SPRN_ESR
 #ifdef CONFIG_PTE_64BIT
-	li	r13,_PAGE_PRESENT
+	li	r13,_PAGE_PRESENT|_PAGE_BAP_SR
 	oris	r13,r13,_PAGE_ACCESSED@h
 #else
-	li	r13,_PAGE_PRESENT|_PAGE_ACCESSED
+	li	r13,_PAGE_PRESENT|_PAGE_READ|_PAGE_ACCESSED
 #endif
 	rlwimi	r13,r12,11,29,29
 
@@ -783,15 +783,15 @@ BEGIN_MMU_FTR_SECTION
 	mtspr	SPRN_MAS7, r10
 END_MMU_FTR_SECTION_IFSET(MMU_FTR_BIG_PHYS)
 #else
-	li	r10, (_PAGE_EXEC | _PAGE_PRESENT)
+	li	r10, (_PAGE_EXEC | _PAGE_READ)
 	mr	r13, r11
 	rlwimi	r10, r11, 31, 29, 29	/* extract _PAGE_DIRTY into SW */
 	and	r12, r11, r10
-	andi.	r10, r11, _PAGE_USER	/* Test for _PAGE_USER */
+	mcrf	cr0, cr5		/* Test for user page */
 	slwi	r10, r12, 1
 	or	r10, r10, r12
 	rlwinm	r10, r10, 0, ~_PAGE_EXEC	/* Clear SX on user pages */
-	iseleq	r12, r12, r10
+	isellt	r12, r10, r12
 	rlwimi	r13, r12, 0, 20, 31	/* Get RPN from PTE, merge w/ perms */
 	mtspr	SPRN_MAS3, r13
 #endif