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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>
This commit is contained in:
Heiko Carstens 2016-06-20 10:35:20 +02:00 committed by Martin Schwidefsky
parent 109ab95471
commit dc4aace160
1 changed files with 59 additions and 2 deletions
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61
arch/s390/include/asm/uaccess.h
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@ -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 */