Messages in this thread Patch in this message | | | From | Christophe Leroy <> | Subject | [PATCH] powerpc/603: Clear C bit when PTE is read only | Date | Mon, 31 Jan 2022 07:17:57 +0000 |
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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
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