Messages in this thread | | | Date | Tue, 16 Nov 2010 18:19:06 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE_NOWRITE |
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On Tue, Nov 16, 2010 at 03:18:03PM +0000, Catalin Marinas wrote: > On 15 November 2010 18:30, Russell King - ARM Linux > <linux@arm.linux.org.uk> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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