arm64: mte: Add asynchronous mode support

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 after the asynchronous tag
check fault 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.
The code that verifies the status of TFSR_EL1 will be added with a
future patch.

Cc: Will Deacon <will@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20210315132019.33202-2-vincenzo.frascino@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
index 7ab500e2ad17..4acf8bf41cad 100644
--- a/arch/arm64/include/asm/mte-kasan.h
+++ b/arch/arm64/include/asm/mte-kasan.h
@@ -77,7 +77,8 @@ static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
 	} while (curr != end);
 }
 
-void mte_enable_kernel(void);
+void mte_enable_kernel_sync(void);
+void mte_enable_kernel_async(void);
 void mte_init_tags(u64 max_tag);
 
 void mte_set_report_once(bool state);
@@ -104,7 +105,11 @@ static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
 {
 }
 
-static inline void mte_enable_kernel(void)
+static inline void mte_enable_kernel_sync(void)
+{
+}
+
+static inline void mte_enable_kernel_async(void)
 {
 }