arm64: uaccess: Implement *_flushcache variants

Implement the set of copy functions with guarantees of a clean cache
upon completion necessary to support the pmem driver.
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -963,6 +963,7 @@ config ARM64_UAO
 config ARM64_PMEM
 	bool "Enable support for persistent memory"
 	select ARCH_HAS_PMEM_API
+	select ARCH_HAS_UACCESS_FLUSHCACHE
 	help
 	  Say Y to enable support for the persistent memory API based on the
 	  ARMv8.2 DCPoP feature.

arch/arm64/include/asm/string.h

@@ -52,6 +52,10 @@ extern void *__memset(void *, int, __kernel_size_t);
 #define __HAVE_ARCH_MEMCMP
 extern int memcmp(const void *, const void *, size_t);
 
+#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
+#define __HAVE_ARCH_MEMCPY_FLUSHCACHE
+void memcpy_flushcache(void *dst, const void *src, size_t cnt);
+#endif
 
 #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
 

arch/arm64/include/asm/uaccess.h

@@ -347,4 +347,16 @@ extern long strncpy_from_user(char *dest, const char __user *src, long count);
 
 extern __must_check long strnlen_user(const char __user *str, long n);
 
+#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
+struct page;
+void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
+extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
+
+static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
+{
+	kasan_check_write(dst, size);
+	return __copy_user_flushcache(dst, src, size);
+}
+#endif
+
 #endif /* __ASM_UACCESS_H */

arch/arm64/lib/Makefile

@@ -17,3 +17,5 @@ CFLAGS_atomic_ll_sc.o	:= -fcall-used-x0 -ffixed-x1 -ffixed-x2		\
 		   -fcall-saved-x10 -fcall-saved-x11 -fcall-saved-x12	\
 		   -fcall-saved-x13 -fcall-saved-x14 -fcall-saved-x15	\
 		   -fcall-saved-x18
+
+lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o