Messages in this thread | | | Subject | Re: [PATCH 2/4] arm64: mte: Add asynchronous mode support | From | Vincenzo Frascino <> | Date | Thu, 7 Jan 2021 17:29:24 +0000 |
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Hi Andrey,
On 1/7/21 4:29 PM, Andrey Konovalov wrote: > On Wed, Jan 6, 2021 at 12:56 PM Vincenzo Frascino > <vincenzo.frascino@arm.com> 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. >> >> Add support for MTE asynchronous mode. >> >> The exception handling mechanism will be added with a future patch. >> >> Note: KASAN HW activates async mode via kasan.mode kernel parameter. >> The default mode is set to synchronous. >> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: Will Deacon <will.deacon@arm.com> >> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> >> --- >> arch/arm64/kernel/mte.c | 31 +++++++++++++++++++++++++++++-- >> 1 file changed, 29 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c >> index 24a273d47df1..5d992e16b420 100644 >> --- 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; >> + } >> + >> + pr_info_once("MTE: enabled in %s mode at EL1\n", m); >> + >> isb(); >> } >> >> -- >> 2.29.2 >> > > Hi Vincenzo, > > It would be cleaner to pass a bool to mte_enable_kernel() and have it > indicate sync/async mode. This way you don't have to pull all these > KASAN constants into the arm64 code. >
Boolean arguments are generally bad for legibility, hence I tend to avoid them. In this case exposing the constants does not seem a big issue especially because the only user of this code is "KASAN_HW_TAGS" and definitely improves its legibility hence I would prefer to keep it as is. > Thanks! >
-- Regards, Vincenzo
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