From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Tue, 16 Nov 2010 18:19:06 +0000 Subject: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE_NOWRITE In-Reply-To: References: <1289584840-18097-1-git-send-email-catalin.marinas@arm.com> <1289584840-18097-6-git-send-email-catalin.marinas@arm.com> <20101115183014.GD31421@n2100.arm.linux.org.uk> Message-ID: <20101116181906.GA21926@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Nov 16, 2010 at 03:18:03PM +0000, Catalin Marinas wrote: > On 15 November 2010 18:30, Russell King - ARM Linux > wrote: > > Let's not make this more complicated than it has to be. ?If we need the > > inverse of WRITE and EXEC, then that's what we should change everyone to, > > not invent a new system to work along side the old system. > > This adds an additional instruction in set_pte_ext, unless you can > write the bit checking in a better way: It actually results in the same number of instructions. From memory: ARMv3-ARMv5: - eor r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY - tst r3, #L_PTE_WRITE | L_PTE_DIRTY @ write and dirty? - orreq r2, r2, #PTE_SMALL_AP_UNO_SRW + eor r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY + tst r3, #L_PTE_RDONLY | L_PTE_DIRTY @ write and dirty? + orreq r2, r2, #PTE_SMALL_AP_UNO_SRW and for ARMv6+: - tst r1, #L_PTE_WRITE - tstne r1, #L_PTE_DIRTY - orreq r3, r3, #PTE_EXT_APX + eor r1, r1, #L_PTE_DIRTY + tst r1, #L_PTE_RDONLY | L_PTE_DIRTY + orrne r3, r3, #PTE_EXT_APX