[PATCH] uio, lib: Fix CONFIG_ARCH_HAS_UACCESS_MCSAFE compilation

[Dan Williams]

Add a common Kconfig CONFIG_ARCH_HAS_UACCESS_MCSAFE that archs can
optionally select, and fixup the declaration of _copy_to_iter_mcsafe().

Fixes: 8780356ef630 ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()")
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Ingo, Thomas, fyi, here is a trivial compilation fixup I will carry in
my tree based on tip/x86/dax. I missed defining the Kconfig symbol, and
my unit test was only dependent on the low level implementation.

 include/linux/uio.h |    2 +-
 lib/Kconfig         |    3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index f5766e853a77..409c845d4cd3 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -155,7 +155,7 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
 #endif
 
 #ifdef CONFIG_ARCH_HAS_UACCESS_MCSAFE
-size_t _copy_to_iter_mcsafe(void *addr, size_t bytes, struct iov_iter *i);
+size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i);
 #else
 #define _copy_to_iter_mcsafe _copy_to_iter
 #endif
diff --git a/lib/Kconfig b/lib/Kconfig
index 5fe577673b98..907f6e4f1cf2 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -586,6 +586,9 @@ config ARCH_HAS_PMEM_API
 config ARCH_HAS_UACCESS_FLUSHCACHE
 	bool
 
+config ARCH_HAS_UACCESS_MCSAFE
+	bool
+
 config STACKDEPOT
 	bool
 	select STACKTRACE