usercopy: fold builtin_const check into inline function

Instead of having each caller of check_object_size() need to remember to
check for a const size parameter, move the check into check_object_size()
itself. This actually matches the original implementation in PaX, though
this commit cleans up the now-redundant builtin_const() calls in the
various architectures.
Signed-off-by: Kees Cook <keescook@chromium.org>

arch/ia64/include/asm/uaccess.h

@@ -241,7 +241,6 @@ extern unsigned long __must_check __copy_user (void __user *to, const void __use
 static inline unsigned long
 __copy_to_user (void __user *to, const void *from, unsigned long count)
 {
-	if (!__builtin_constant_p(count))
 	check_object_size(from, count, true);
 
 	return __copy_user(to, (__force void __user *) from, count);
@@ -250,7 +249,6 @@ __copy_to_user (void __user *to, const void *from, unsigned long count)
 static inline unsigned long
 __copy_from_user (void *to, const void __user *from, unsigned long count)
 {
-	if (!__builtin_constant_p(count))
 	check_object_size(to, count, false);
 
 	return __copy_user((__force void __user *) to, from, count);
@@ -265,7 +263,6 @@ __copy_from_user (void *to, const void __user *from, unsigned long count)
 	long __cu_len = (n);								\
 											\
 	if (__access_ok(__cu_to, __cu_len, get_fs())) {					\
-		if (!__builtin_constant_p(n))						\
 		check_object_size(__cu_from, __cu_len, true);			\
 		__cu_len = __copy_user(__cu_to, (__force void __user *)  __cu_from, __cu_len);	\
 	}										\
@@ -280,7 +277,6 @@ __copy_from_user (void *to, const void __user *from, unsigned long count)
 											\
 	__chk_user_ptr(__cu_from);							\
 	if (__access_ok(__cu_from, __cu_len, get_fs())) {				\
-		if (!__builtin_constant_p(n))						\
 		check_object_size(__cu_to, __cu_len, false);			\
 		__cu_len = __copy_user((__force void __user *) __cu_to, __cu_from, __cu_len);	\
 	}										\

arch/powerpc/include/asm/uaccess.h

@@ -311,13 +311,11 @@ static inline unsigned long copy_from_user(void *to,
 	unsigned long over;
 
 	if (access_ok(VERIFY_READ, from, n)) {
-		if (!__builtin_constant_p(n))
 		check_object_size(to, n, false);
 		return __copy_tofrom_user((__force void __user *)to, from, n);
 	}
 	if ((unsigned long)from < TASK_SIZE) {
 		over = (unsigned long)from + n - TASK_SIZE;
-		if (!__builtin_constant_p(n - over))
 		check_object_size(to, n - over, false);
 		return __copy_tofrom_user((__force void __user *)to, from,
 				n - over) + over;
@@ -331,13 +329,11 @@ static inline unsigned long copy_to_user(void __user *to,
 	unsigned long over;
 
 	if (access_ok(VERIFY_WRITE, to, n)) {
-		if (!__builtin_constant_p(n))
 		check_object_size(from, n, true);
 		return __copy_tofrom_user(to, (__force void __user *)from, n);
 	}
 	if ((unsigned long)to < TASK_SIZE) {
 		over = (unsigned long)to + n - TASK_SIZE;
-		if (!__builtin_constant_p(n))
 		check_object_size(from, n - over, true);
 		return __copy_tofrom_user(to, (__force void __user *)from,
 				n - over) + over;
@@ -383,7 +379,6 @@ static inline unsigned long __copy_from_user_inatomic(void *to,
 			return 0;
 	}
 
-	if (!__builtin_constant_p(n))
 	check_object_size(to, n, false);
 
 	return __copy_tofrom_user((__force void __user *)to, from, n);
@@ -412,7 +407,7 @@ static inline unsigned long __copy_to_user_inatomic(void __user *to,
 		if (ret == 0)
 			return 0;
 	}
-	if (!__builtin_constant_p(n))
+
 	check_object_size(from, n, true);
 
 	return __copy_tofrom_user(to, (__force const void __user *)from, n);

arch/sparc/include/asm/uaccess_32.h

@@ -249,7 +249,6 @@ unsigned long __copy_user(void __user *to, const void __user *from, unsigned lon
 static inline unsigned long copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	if (n && __access_ok((unsigned long) to, n)) {
-		if (!__builtin_constant_p(n))
 		check_object_size(from, n, true);
 		return __copy_user(to, (__force void __user *) from, n);
 	} else
@@ -258,7 +257,6 @@ static inline unsigned long copy_to_user(void __user *to, const void *from, unsi
 
 static inline unsigned long __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	if (!__builtin_constant_p(n))
 	check_object_size(from, n, true);
 	return __copy_user(to, (__force void __user *) from, n);
 }
@@ -266,7 +264,6 @@ static inline unsigned long __copy_to_user(void __user *to, const void *from, un
 static inline unsigned long copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	if (n && __access_ok((unsigned long) from, n)) {
-		if (!__builtin_constant_p(n))
 		check_object_size(to, n, false);
 		return __copy_user((__force void __user *) to, from, n);
 	} else

arch/sparc/include/asm/uaccess_64.h

@@ -212,7 +212,6 @@ copy_from_user(void *to, const void __user *from, unsigned long size)
 {
 	unsigned long ret;
 
-	if (!__builtin_constant_p(size))
 	check_object_size(to, size, false);
 
 	ret = ___copy_from_user(to, from, size);
@@ -233,8 +232,8 @@ copy_to_user(void __user *to, const void *from, unsigned long size)
 {
 	unsigned long ret;
 
-	if (!__builtin_constant_p(size))
 	check_object_size(from, size, true);
+
 	ret = ___copy_to_user(to, from, size);
 	if (unlikely(ret))
 		ret = copy_to_user_fixup(to, from, size);

include/linux/thread_info.h

@@ -121,6 +121,7 @@ extern void __check_object_size(const void *ptr, unsigned long n,
 static inline void check_object_size(const void *ptr, unsigned long n,
 				     bool to_user)
 {
+	if (!__builtin_constant_p(n))
 		__check_object_size(ptr, n, to_user);
 }
 #else