arm64: mte: Add asymmetric mode support

MTE provides an asymmetric mode for detecting tag exceptions. In
particular, when such a mode is present, the CPU triggers a fault
on a tag mismatch during a load operation and asynchronously updates
a register when a tag mismatch is detected during a store operation.

Add support for MTE asymmetric mode.

Note: If the CPU does not support MTE asymmetric mode the kernel falls
back on synchronous mode which is the default for kasan=on.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20211006154751.4463-5-vincenzo.frascino@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index 02511650cffe..075539f5f1c8 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -88,11 +88,11 @@ static inline int mte_ptrace_copy_tags(struct task_struct *child,
 
 #ifdef CONFIG_KASAN_HW_TAGS
 /* Whether the MTE asynchronous mode is enabled. */
-DECLARE_STATIC_KEY_FALSE(mte_async_mode);
+DECLARE_STATIC_KEY_FALSE(mte_async_or_asymm_mode);
 
-static inline bool system_uses_mte_async_mode(void)
+static inline bool system_uses_mte_async_or_asymm_mode(void)
 {
-	return static_branch_unlikely(&mte_async_mode);
+	return static_branch_unlikely(&mte_async_or_asymm_mode);
 }
 
 void mte_check_tfsr_el1(void);
@@ -121,7 +121,7 @@ static inline void mte_check_tfsr_exit(void)
 	mte_check_tfsr_el1();
 }
 #else
-static inline bool system_uses_mte_async_mode(void)
+static inline bool system_uses_mte_async_or_asymm_mode(void)
 {
 	return false;
 }