linux-kernel - [PATCH] powerpc/8xx: Fix pte_access_permitted() for PAGE

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Message-ID: <30de3838862d1a7d55582963ca5fe567b3a91b28.1692962717.git.christophe.leroy@csgroup.eu>
Date:   Fri, 25 Aug 2023 13:25:36 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/8xx: Fix pte_access_permitted() for PAGE_NONE

On 8xx, PAGE_NONE is handled by setting _PAGE_NA instead of clearing
_PAGE_USER.

But then pte_user() returns 1 also for PAGE_NONE.

As _PAGE_NA prevent reads, add a specific version of pte_read()
that returns 0 when _PAGE_NA is set instead of always returning 1.

Fixes: 351750331fc1 ("powerpc/mm: Introduce _PAGE_NA")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/nohash/32/pte-8xx.h | 7 +++++++
 arch/powerpc/include/asm/nohash/pgtable.h    | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
index 1a89ebdc3acc..0238e6bd0d6c 100644
--- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
@@ -94,6 +94,13 @@ static inline pte_t pte_wrprotect(pte_t pte)
 
 #define pte_wrprotect pte_wrprotect
 
+static inline int pte_read(pte_t pte)
+{
+	return (pte_val(pte) & _PAGE_RO) != _PAGE_NA;
+}
+
+#define pte_read pte_read
+
 static inline int pte_write(pte_t pte)
 {
 	return !(pte_val(pte) & _PAGE_RO);
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index a6caaaab6f92..3af11981fcd5 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -25,7 +25,9 @@ static inline int pte_write(pte_t pte)
 	return pte_val(pte) & _PAGE_RW;
 }
 #endif
+#ifndef pte_read
 static inline int pte_read(pte_t pte)		{ return 1; }
+#endif
 static inline int pte_dirty(pte_t pte)		{ return pte_val(pte) & _PAGE_DIRTY; }
 static inline int pte_special(pte_t pte)	{ return pte_val(pte) & _PAGE_SPECIAL; }
 static inline int pte_none(pte_t pte)		{ return (pte_val(pte) & ~_PTE_NONE_MASK) == 0; }
-- 
2.41.0