[PATCH v2] uaccess: add noop untagged_addr definition

[Andrey Konovalov]

Architectures that support memory tagging have a need to perform untagging
(stripping the tag) in various parts of the kernel. This patch adds an
untagged_addr() macro, which is defined as noop for architectures that do
not support memory tagging. The oncoming patch series will define it at
least for sparc64 and arm64.

Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
 include/linux/mm.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834ac32b7..dd0b5f4e1e45 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly;
 #include <asm/pgtable.h>
 #include <asm/processor.h>
 
+/*
+ * Architectures that support memory tagging (assigning tags to memory regions,
+ * embedding these tags into addresses that point to these memory regions, and
+ * checking that the memory and the pointer tags match on memory accesses)
+ * redefine this macro to strip tags from pointers.
+ * It's defined as noop for arcitectures that don't support memory tagging.
+ */
+#ifndef untagged_addr
+#define untagged_addr(addr) (addr)
+#endif
+
 #ifndef __pa_symbol
 #define __pa_symbol(x)  __pa(RELOC_HIDE((unsigned long)(x), 0))
 #endif
-- 
2.22.0.rc1.311.g5d7573a151-goog