s390/uaccess: fix __put_get_user_asm define

The __put_get_user_asm defines an inline assmembly which makes use of
the asm register construct. The parameters passed to that define may
also contain function calls.

It is a gcc restriction that between register asm statements and the
use of any such annotated variables function calls may clobber the
register / variable contents. Or in other words: gcc would generate
broken code.

This can be achieved e.g. with the following code:

    get_user(x, func() ? a : b);

where the call of func would clobber register zero which is used by
the __put_get_user_asm define.
To avoid this add two static inline functions which don't have these
side effects.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 59 insertions, 2 deletions

diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index 2ea7f32..9b49cf1 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -151,8 +151,65 @@ unsigned long __must_check __copy_to_user(void __user *to, const void *from,
 	__rc;							\
 })
 
-#define __put_user_fn(x, ptr, size) __put_get_user_asm(ptr, x, size, 0x810000UL)
-#define __get_user_fn(x, ptr, size) __put_get_user_asm(x, ptr, size, 0x81UL)
+static inline int __put_user_fn(void *x, void __user *ptr, unsigned long size)
+{
+	unsigned long spec = 0x810000UL;
+	int rc;
+
+	switch (size) {
+	case 1:
+		rc = __put_get_user_asm((unsigned char __user *)ptr,
+					(unsigned char *)x,
+					size, spec);
+		break;
+	case 2:
+		rc = __put_get_user_asm((unsigned short __user *)ptr,
+					(unsigned short *)x,
+					size, spec);
+		break;
+	case 4:
+		rc = __put_get_user_asm((unsigned int __user *)ptr,
+					(unsigned int *)x,
+					size, spec);
+		break;
+	case 8:
+		rc = __put_get_user_asm((unsigned long __user *)ptr,
+					(unsigned long *)x,
+					size, spec);
+		break;
+	};
+	return rc;
+}
+
+static inline int __get_user_fn(void *x, const void __user *ptr, unsigned long size)
+{
+	unsigned long spec = 0x81UL;
+	int rc;
+
+	switch (size) {
+	case 1:
+		rc = __put_get_user_asm((unsigned char *)x,
+					(unsigned char __user *)ptr,
+					size, spec);
+		break;
+	case 2:
+		rc = __put_get_user_asm((unsigned short *)x,
+					(unsigned short __user *)ptr,
+					size, spec);
+		break;
+	case 4:
+		rc = __put_get_user_asm((unsigned int *)x,
+					(unsigned int __user *)ptr,
+					size, spec);
+		break;
+	case 8:
+		rc = __put_get_user_asm((unsigned long *)x,
+					(unsigned long __user *)ptr,
+					size, spec);
+		break;
+	};
+	return rc;
+}
 
 #else /* CONFIG_HAVE_MARCH_Z10_FEATURES */