From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH] powerpc/603: Clear C bit when PTE is read only
Date: Mon, 31 Jan 2022 07:17:57 +0000 [thread overview]
Message-ID: <bbb13848ff0100a76ee9ea95118058c30ae95f2c.1643613343.git.christophe.leroy@csgroup.eu> (raw)
On book3s/32 MMU, PP bits don't offer kernel RO protection,
kernel pages are always RW.
However, on the 603 a page fault is always generated when the
C bit (change bit = dirty bit) is not set.
Enforce kernel RO protection by clearing C bit in TLB miss
handler when the page doesn't have _PAGE_RW flag.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/kernel/head_book3s_32.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 7f4f3a52b730..6c739beb938c 100644
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -504,7 +504,9 @@ DataLoadTLBMiss:
/* Convert linux-style PTE to low word of PPC-style PTE */
rlwinm r1,r0,32-9,30,30 /* _PAGE_RW -> PP msb */
rlwimi r0,r0,32-1,30,30 /* _PAGE_USER -> PP msb */
+ rlwimi r1,r0,32-3,24,24 /* _PAGE_RW -> _PAGE_DIRTY */
rlwimi r0,r0,32-1,31,31 /* _PAGE_USER -> PP lsb */
+ xori r1,r1,_PAGE_DIRTY /* clear dirty when not rw */
ori r1,r1,0xe04 /* clear out reserved bits */
andc r1,r0,r1 /* PP = user? rw? 1: 3: 0 */
BEGIN_FTR_SECTION
--
2.33.1
next reply other threads:[~2022-01-31 7:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-31 7:17 Christophe Leroy [this message]
2022-02-15 5:26 ` [PATCH] powerpc/603: Clear C bit when PTE is read only Michael Ellerman
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