ARM: 7528/1: uaccess: annotate [__]{get,put}_user functions with might_fault()

The user access functions may generate a fault, resulting in invocation
of a handler that may sleep.

This patch annotates the accessors with might_fault() so that we print a
warning if they are invoked from atomic context and help lockdep keep
track of mmap_sem.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/uaccess.h

@@ -118,7 +118,7 @@ extern int __get_user_4(void *);
 		: "0" (__p), "r" (__l)					\
 		: __GUP_CLOBBER_##__s)
 
-#define get_user(x,p)							\
+#define __get_user_check(x,p)							\
 	({								\
 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
 		register const typeof(*(p)) __user *__p asm("r0") = (p);\
@@ -141,6 +141,12 @@ extern int __get_user_4(void *);
 		__e;							\
 	})
 
+#define get_user(x,p)							\
+	({								\
+		might_fault();						\
+		__get_user_check(x,p);					\
+	 })
+
 extern int __put_user_1(void *, unsigned int);
 extern int __put_user_2(void *, unsigned int);
 extern int __put_user_4(void *, unsigned int);
@@ -155,7 +161,7 @@ extern int __put_user_8(void *, unsigned long long);
 		: "0" (__p), "r" (__r2), "r" (__l)			\
 		: "ip", "lr", "cc")
 
-#define put_user(x,p)							\
+#define __put_user_check(x,p)							\
 	({								\
 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
 		register const typeof(*(p)) __r2 asm("r2") = (x);	\
@@ -180,6 +186,12 @@ extern int __put_user_8(void *, unsigned long long);
 		__e;							\
 	})
 
+#define put_user(x,p)							\
+	({								\
+		might_fault();						\
+		__put_user_check(x,p);					\
+	 })
+
 #else /* CONFIG_MMU */
 
 /*
@@ -233,6 +245,7 @@ do {									\
 	unsigned long __gu_addr = (unsigned long)(ptr);			\
 	unsigned long __gu_val;						\
 	__chk_user_ptr(ptr);						\
+	might_fault();							\
 	switch (sizeof(*(ptr))) {					\
 	case 1:	__get_user_asm_byte(__gu_val,__gu_addr,err);	break;	\
 	case 2:	__get_user_asm_half(__gu_val,__gu_addr,err);	break;	\
@@ -314,6 +327,7 @@ do {									\
 	unsigned long __pu_addr = (unsigned long)(ptr);			\
 	__typeof__(*(ptr)) __pu_val = (x);				\
 	__chk_user_ptr(ptr);						\
+	might_fault();							\
 	switch (sizeof(*(ptr))) {					\
 	case 1: __put_user_asm_byte(__pu_val,__pu_addr,err);	break;	\
 	case 2: __put_user_asm_half(__pu_val,__pu_addr,err);	break;	\