arm64: avoid multiple evaluation of ptr in get_user/put_user()

get_user() is defined as a function macro in arm64, and trace_get_user()
calls it as followed:
     get_user(ch, ptr++);
Since the second parameter occurs twice in the definition, 'ptr++' is
unexpectedly evaluated twice and trace_get_user() will generate a bogus
string from user-provided one. As a result, some ftrace sysfs operations,
like "echo FUNCNAME > set_ftrace_filter," hit this case and eventually fail.
This patch fixes the issue both in get_user() and put_user().

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[catalin.marinas@arm.com: added __user type annotation and s/optr/__p/]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/uaccess.h

@@ -166,9 +166,10 @@ do {									\
 
 #define get_user(x, ptr)						\
 ({									\
+	__typeof__(*(ptr)) __user *__p = (ptr);				\
 	might_fault();							\
-	access_ok(VERIFY_READ, (ptr), sizeof(*(ptr))) ?			\
-		__get_user((x), (ptr)) :				\
+	access_ok(VERIFY_READ, __p, sizeof(*__p)) ?			\
+		__get_user((x), __p) :					\
 		((x) = 0, -EFAULT);					\
 })
 
@@ -227,9 +228,10 @@ do {									\
 
 #define put_user(x, ptr)						\
 ({									\
+	__typeof__(*(ptr)) __user *__p = (ptr);				\
 	might_fault();							\
-	access_ok(VERIFY_WRITE, (ptr), sizeof(*(ptr))) ?		\
-		__put_user((x), (ptr)) :				\
+	access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?			\
+		__put_user((x), __p) :					\
 		-EFAULT;						\
 })