From: Christophe Leroy Date: Mon, 31 Jan 2022 07:17:57 +0000 (+0000) Subject: powerpc/603: Clear C bit when PTE is read only X-Git-Tag: v6.6.17~7919^2~136 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4634bf4455fe26f07dabf97c3585c9ccb86353c4;p=platform%2Fkernel%2Flinux-rpi.git powerpc/603: Clear C bit when PTE is read only 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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/bbb13848ff0100a76ee9ea95118058c30ae95f2c.1643613343.git.christophe.leroy@csgroup.eu --- diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S index 7e27b44..d489b96 100644 --- a/arch/powerpc/kernel/head_book3s_32.S +++ b/arch/powerpc/kernel/head_book3s_32.S @@ -507,7 +507,9 @@ 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