Re: [PATCH v3 3/4] arm64: mte: Enable async tag check fault
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-01-18 13:02:21
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On Fri, Jan 15, 2021 at 12:00:42PM +0000, Vincenzo Frascino wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index d02aff9f493d..1a715963d909 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h@@ -92,5 +92,26 @@ static inline void mte_assign_mem_tag_range(void *addr, size_t size) #endif /* CONFIG_ARM64_MTE */ +#ifdef CONFIG_KASAN_HW_TAGS +void mte_check_tfsr_el1_no_sync(void); +static inline void mte_check_tfsr_el1(void) +{ + mte_check_tfsr_el1_no_sync(); + /* + * The asynchronous faults are synch'ed automatically with + * TFSR_EL1 on kernel entry but for exit an explicit dsb() + * is required. + */ + dsb(ish); +}
Mark commented already, the barrier should be above mte_check_tfsr_el1_no_sync(). Regarding the ISB, we are waiting for confirmation from the architects.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index df7a1ae26d7c..6cb92e9d6ad1 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c@@ -180,6 +180,32 @@ void mte_enable_kernel(enum kasan_hw_tags_mode mode) isb(); } +#ifdef CONFIG_KASAN_HW_TAGS +void mte_check_tfsr_el1_no_sync(void) +{ + u64 tfsr_el1; + + if (!system_supports_mte()) + return; + + tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1); + + /* + * The kernel should never hit the condition TF0 == 1 + * at this point because for the futex code we set + * PSTATE.TCO. + */ + WARN_ON(tfsr_el1 & SYS_TFSR_EL1_TF0);
I'd change this to a WARN_ON_ONCE() in case we trip over this due to model bugs etc. and it floods the log.
+ if (tfsr_el1 & SYS_TFSR_EL1_TF1) {
+ write_sysreg_s(0, SYS_TFSR_EL1);
+ isb();While in general we use ISB after a sysreg update, I haven't convinced myself it's needed here. There's no side-effect to updating this reg and a subsequent TFSR access should see the new value. If a speculated load is allowed to update this reg, we'd probably need an ISB+DSB (I don't think it does, something to check with the architects).
+
+ pr_err("MTE: Asynchronous tag exception detected!");We discussed this already, I think we should replace this pr_err() with a call to kasan_report(). In principle, kasan already knows the mode as it asked for sync/async but we could make this explicit and expand the kasan API to take some argument (or have separate function like kasan_report_async()). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel