Add address tag related macro and function to test MTE_FAR feature.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 .../testing/selftests/arm64/mte/mte_common_util.c  | 14 ++++++++++++++
 .../testing/selftests/arm64/mte/mte_common_util.h  |  2 ++
 tools/testing/selftests/arm64/mte/mte_def.h        |  8 ++++++++
 3 files changed, 24 insertions(+)

diff --git a/tools/testing/selftests/arm64/mte/mte_common_util.c b/tools/testing/selftests/arm64/mte/mte_common_util.c
index 048b8a507b70..c21f86143a6f 100644
--- a/tools/testing/selftests/arm64/mte/mte_common_util.c
+++ b/tools/testing/selftests/arm64/mte/mte_common_util.c
@@ -131,6 +131,20 @@ void mte_clear_tags(void *ptr, size_t size)
 	mte_clear_tag_address_range(ptr, size);
 }
 
+void *mte_insert_atag(void *ptr)
+{
+	unsigned char atag;
+
+	srandom(time(NULL));
+	atag =  mtefar_support ? (random() % MT_ATAG_MASK) + 1 : 0;
+	return (void *)MT_SET_ATAG((unsigned long)ptr, atag);
+}
+
+void *mte_clear_atag(void *ptr)
+{
+	return (void *)MT_CLEAR_ATAG((unsigned long)ptr);
+}
+
 static void *__mte_allocate_memory_range(size_t size, int mem_type, int mapping,
 					 size_t range_before, size_t range_after,
 					 bool tags, int fd)
diff --git a/tools/testing/selftests/arm64/mte/mte_common_util.h b/tools/testing/selftests/arm64/mte/mte_common_util.h
index 4e1dd959df9b..045e4ad2f018 100644
--- a/tools/testing/selftests/arm64/mte/mte_common_util.h
+++ b/tools/testing/selftests/arm64/mte/mte_common_util.h
@@ -56,6 +56,8 @@ void mte_free_memory_tag_range(void *ptr, size_t size, int mem_type,
 			       size_t range_before, size_t range_after);
 void *mte_insert_tags(void *ptr, size_t size);
 void mte_clear_tags(void *ptr, size_t size);
+void *mte_insert_atag(void *ptr);
+void *mte_clear_atag(void *ptr);
 int mte_default_setup(void);
 void mte_restore_setup(void);
 int mte_switch_mode(int mte_option, unsigned long incl_mask);
diff --git a/tools/testing/selftests/arm64/mte/mte_def.h b/tools/testing/selftests/arm64/mte/mte_def.h
index 9b188254b61a..6ad22f07c9b8 100644
--- a/tools/testing/selftests/arm64/mte/mte_def.h
+++ b/tools/testing/selftests/arm64/mte/mte_def.h
@@ -42,6 +42,8 @@
 #define MT_TAG_COUNT		16
 #define MT_INCLUDE_TAG_MASK	0xFFFF
 #define MT_EXCLUDE_TAG_MASK	0x0
+#define MT_ATAG_SHIFT		60
+#define MT_ATAG_MASK		0xFUL
 
 #define MT_ALIGN_GRANULE	(MT_GRANULE_SIZE - 1)
 #define MT_CLEAR_TAG(x)		((x) & ~(MT_TAG_MASK << MT_TAG_SHIFT))
@@ -49,6 +51,12 @@
 #define MT_FETCH_TAG(x)		((x >> MT_TAG_SHIFT) & (MT_TAG_MASK))
 #define MT_ALIGN_UP(x)		((x + MT_ALIGN_GRANULE) & ~(MT_ALIGN_GRANULE))
 
+#define MT_CLEAR_ATAG(x)	((x) & ~(MT_TAG_MASK << MT_ATAG_SHIFT))
+#define MT_SET_ATAG(x, y)	((x) | (((y) & MT_ATAG_MASK) << MT_ATAG_SHIFT))
+#define MT_FETCH_ATAG(x)	((x >> MT_ATAG_SHIFT) & (MT_ATAG_MASK))
+
+#define MT_CLEAR_TAGS(x) 	(MT_CLEAR_ATAG(MT_CLEAR_TAG(x)))
+
 #define MT_PSTATE_TCO_SHIFT	25
 #define MT_PSTATE_TCO_MASK	~(0x1 << MT_PSTATE_TCO_SHIFT)
 #define MT_PSTATE_TCO_EN	1
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

On Wed, Jun 11, 2025 at 10:41:04AM +0100, Yeoreum Yun wrote:
> Add address tag related macro and function to test MTE_FAR feature.

> +void *mte_insert_atag(void *ptr)
> +{
> +	unsigned char atag;
> +
> +	srandom(time(NULL));
> +	atag =  mtefar_support ? (random() % MT_ATAG_MASK) + 1 : 0;
> +	return (void *)MT_SET_ATAG((unsigned long)ptr, atag);
> +}

Ah, this is where the time.h inclusion came from - it just got split
into the wrong patch.  I would move that srandom() into the main()
function, we don't need to reset the RNG every time we generate a tag
and since time() has a resolution of a second depending on how fast the
machine is we might manage to end up setting exactly the same value for
every tag insertion the program does which would seem to defeat the
point of using a RNG here.