Commit 8c8a3b5b authored Sep 15, 2021 by Peter Collingbourne Committed by Catalin Marinas Sep 21, 2021

arm64: add MTE supported check to thread switching and syscall entry/exit



This lets us avoid doing unnecessary work on hardware that does not
support MTE, and will allow us to freely use MTE instructions in the
code called by mte_thread_switch().

Since this would mean that we do a redundant check in
mte_check_tfsr_el1(), remove it and add two checks now required in its
callers. This also avoids an unnecessary DSB+ISB sequence on the syscall
exit path for hardware not supporting MTE.

Fixes: 65812c69 ("arm64: mte: Enable async tag check fault")
Cc: <stable@vger.kernel.org> # 5.13.x
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I02fd000d1ef2c86c7d2952a7f099b254ec227a5d
Link: https://lore.kernel.org/r/20210915190336.398390-1-pcc@google.com


[catalin.marinas@arm.com: adjust the commit log slightly]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 9fcb2e93

arch/arm64/include/asm/mte.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -99,11 +99,17 @@ void mte_check_tfsr_el1(void);

		static inline void mte_check_tfsr_entry(void)
		{
		if (!system_supports_mte())
		return;

		mte_check_tfsr_el1();
		}

		static inline void mte_check_tfsr_exit(void)
		{
		if (!system_supports_mte())
		return;

		/*
		* The asynchronous faults are sync'ed automatically with
		* TFSR_EL1 on kernel entry but for exit an explicit dsb()

arch/arm64/kernel/mte.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -142,12 +142,7 @@ void mte_enable_kernel_async(void)
		#ifdef CONFIG_KASAN_HW_TAGS
		void mte_check_tfsr_el1(void)
		{
		u64 tfsr_el1;

		if (!system_supports_mte())
		return;

		tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1);
		u64 tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1);

		if (unlikely(tfsr_el1 & SYS_TFSR_EL1_TF1)) {
		/*
		@@ -199,6 +194,9 @@ void mte_thread_init_user(void)

		void mte_thread_switch(struct task_struct *next)
		{
		if (!system_supports_mte())
		return;

		mte_update_sctlr_user(next);

		/*