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x86: introduce copy_user_handle_tail() routine

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Introduce generic C routine for handling necessary tail operations after
protection fault in copy_*_user on x86.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Vitaly Mayatskikh 2008-07-02 15:48:21 +02:00 committed by Ingo Molnar
parent de989ef093
commit 1129585a08
2 changed files with 26 additions and 0 deletions
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23
arch/x86/lib/usercopy_64.c
View file

@ -158,3 +158,26 @@ unsigned long copy_in_user(void __user *to, const void __user *from, unsigned le
}
EXPORT_SYMBOL(copy_in_user);
/*
* Try to copy last bytes and clear the rest if needed.
* Since protection fault in copy_from/to_user is not a normal situation,
* it is not necessary to optimize tail handling.
*/
unsigned long
copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
{
char c;
unsigned zero_len;
for (; len; --len) {
if (__get_user_nocheck(c, from++, sizeof(char)))
break;
if (__put_user_nocheck(c, to++, sizeof(char)))
break;
}
for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
if (__put_user_nocheck(c, to++, sizeof(char)))
break;
return len;
}

3
include/asm-x86/uaccess_64.h
View file

@ -195,4 +195,7 @@ static inline int __copy_from_user_inatomic_nocache(void *dst,
return __copy_user_nocache(dst, src, size, 0);
}
unsigned long
copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest);
#endif /* __X86_64_UACCESS_H */