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Commit dc4aace1 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 109ab954

arch/s390/include/asm/uaccess.h

+59 −2
Original line number Diff line number Diff line
@@ -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 */