Re: [PATCH v2 2/4] arm64: mte: Add asynchronous mode support
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-01-13 17:23:15
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On Thu, Jan 07, 2021 at 05:29:06PM +0000, Vincenzo Frascino wrote:
MTE provides an asynchronous mode for detecting tag exceptions. In particular instead of triggering a fault the arm64 core updates a register which is checked by the kernel at the first entry after the tag exception has occurred.
Just rephrase the "tag exception" here as there's no exception taken. Also we don't check this only when the kernel is first entered after a tag check fault, as per patch 3.
quoted hunk ↗ jump to hunk
--- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c@@ -153,8 +153,35 @@ void mte_init_tags(u64 max_tag) void mte_enable_kernel(enum kasan_arg_mode mode) { - /* Enable MTE Sync Mode for EL1. */ - sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC); + const char *m; + + /* Preset parameter values based on the mode. */ + switch (mode) { + case KASAN_ARG_MODE_OFF: + return; + case KASAN_ARG_MODE_LIGHT: + /* Enable MTE Async Mode for EL1. */ + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_ASYNC); + m = "asynchronous"; + break; + case KASAN_ARG_MODE_DEFAULT: + case KASAN_ARG_MODE_PROD: + case KASAN_ARG_MODE_FULL: + /* Enable MTE Sync Mode for EL1. */ + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC); + m = "synchronous"; + break; + default: + /* + * kasan mode should be always set hence we should + * not reach this condition. + */ + WARN_ON_ONCE(1); + return; + }
I guess the switch statement here will be re-written as we want kasan to drive the actual sync/async modes as it sees fit rather than MTE guessing what PROD/FULL/LIGHT means. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel