Re: [PATCH 26/35] kasan, arm64: Enable TBI EL1
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2020-09-08 20:00:41
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On Tue, Sep 08, 2020 at 04:12:49PM +0200, Andrey Konovalov wrote:
On Tue, Sep 8, 2020 at 4:06 PM Catalin Marinas [off-list ref] wrote:quoted
On Tue, Sep 08, 2020 at 03:18:04PM +0200, Andrey Konovalov wrote:quoted
On Thu, Aug 27, 2020 at 12:40 PM Catalin Marinas [off-list ref] wrote:quoted
On Fri, Aug 14, 2020 at 07:27:08PM +0200, Andrey Konovalov wrote:quoted
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 152d74f2cc9c..6880ddaa5144 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S@@ -38,7 +38,7 @@ /* PTWs cacheable, inner/outer WBWA */ #define TCR_CACHE_FLAGS TCR_IRGN_WBWA | TCR_ORGN_WBWA -#ifdef CONFIG_KASAN_SW_TAGS +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) #define TCR_KASAN_FLAGS TCR_TBI1 #else #define TCR_KASAN_FLAGS 0I prefer to turn TBI1 on only if MTE is present. So on top of the v8 user series, just do this in __cpu_setup.Started working on this, but realized that I don't understand what exactly is suggested here. TCR_KASAN_FLAGS are used in __cpu_setup(), so this already happens in __cpu_setup(). Do you mean that TBI1 should be enabled when CONFIG_ARM64_MTE is enabled, but CONFIG_KASAN_HW_TAGS is disabled?What I meant is that we should turn TBI1 only when the MTE is present in hardware (and the ARM64_MTE option is on). But I probably missed the way MTE is used with KASAN. So what happens if CONFIG_KASAN_HW_TAGS and CONFIG_ARM64_MTE are both on but the hardware does not support MTE? Does KASAN still generate tagged pointers? If yes, then the current patch is fine, we should always set TBI1.No, the tag is always 0xFF when MTE is not supported. Should we then only enable TBI1 if system_supports_mte() or something like that?
You could add it do this block in __cpu_setup: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/tree/arch/arm64/mm/proc.S?h=for-next/mte#n429 It needs a few changes to have "mov_q x10, TCR_..." before the MTE check so that you can add the TBI1 bit in there. system_supports_mte() would be called too late, you want this set before the MMU is turned on. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel