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kmemcheck: make bitfield annotations truly no-ops when disabled 

It turns out that even zero-sized struct members (int foo[0];) will affect
the struct layout, causing us in particular to lose 4 bytes in struct
sock.

This patch fixes the regression in CONFIG_KMEMCHECK=n case.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vegard Nossum 2010-01-08 14:42:35 -08:00 committed by Linus Torvalds
parent cb5a8b2c92
commit e992cd9b72
1 changed files with 59 additions and 53 deletions
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112
include/linux/kmemcheck.h
View File

@ -36,6 +36,56 @@ int kmemcheck_hide_addr(unsigned long address);
bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size);
/*
* Bitfield annotations
*
* How to use: If you have a struct using bitfields, for example
*
* struct a {
* int x:8, y:8;
* };
*
* then this should be rewritten as
*
* struct a {
* kmemcheck_bitfield_begin(flags);
* int x:8, y:8;
* kmemcheck_bitfield_end(flags);
* };
*
* Now the "flags_begin" and "flags_end" members may be used to refer to the
* beginning and end, respectively, of the bitfield (and things like
* &x.flags_begin is allowed). As soon as the struct is allocated, the bit-
* fields should be annotated:
*
* struct a *a = kmalloc(sizeof(struct a), GFP_KERNEL);
* kmemcheck_annotate_bitfield(a, flags);
*/
#define kmemcheck_bitfield_begin(name) \
int name##_begin[0];
#define kmemcheck_bitfield_end(name) \
int name##_end[0];
#define kmemcheck_annotate_bitfield(ptr, name) \
do { \
int _n; \
\
if (!ptr) \
break; \
\
_n = (long) &((ptr)->name##_end) \
- (long) &((ptr)->name##_begin); \
MAYBE_BUILD_BUG_ON(_n < 0); \
\
kmemcheck_mark_initialized(&((ptr)->name##_begin), _n); \
} while (0)
#define kmemcheck_annotate_variable(var) \
do { \
kmemcheck_mark_initialized(&(var), sizeof(var)); \
} while (0) \
#else
#define kmemcheck_enabled 0
@ -106,60 +156,16 @@ static inline bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size)
return true;
}
#endif /* CONFIG_KMEMCHECK */
/*
* Bitfield annotations
*
* How to use: If you have a struct using bitfields, for example
*
* struct a {
* int x:8, y:8;
* };
*
* then this should be rewritten as
*
* struct a {
* kmemcheck_bitfield_begin(flags);
* int x:8, y:8;
* kmemcheck_bitfield_end(flags);
* };
*
* Now the "flags_begin" and "flags_end" members may be used to refer to the
* beginning and end, respectively, of the bitfield (and things like
* &x.flags_begin is allowed). As soon as the struct is allocated, the bit-
* fields should be annotated:
*
* struct a *a = kmalloc(sizeof(struct a), GFP_KERNEL);
* kmemcheck_annotate_bitfield(a, flags);
*
* Note: We provide the same definitions for both kmemcheck and non-
* kmemcheck kernels. This makes it harder to introduce accidental errors. It
* is also allowed to pass NULL pointers to kmemcheck_annotate_bitfield().
*/
#define kmemcheck_bitfield_begin(name) \
int name##_begin[0];
#define kmemcheck_bitfield_end(name) \
int name##_end[0];
#define kmemcheck_annotate_bitfield(ptr, name) \
do { \
int _n; \
\
if (!ptr) \
break; \
\
_n = (long) &((ptr)->name##_end) \
- (long) &((ptr)->name##_begin); \
MAYBE_BUILD_BUG_ON(_n < 0); \
\
kmemcheck_mark_initialized(&((ptr)->name##_begin), _n); \
#define kmemcheck_bitfield_begin(name)
#define kmemcheck_bitfield_end(name)
#define kmemcheck_annotate_bitfield(ptr, name) \
do { \
} while (0)
#define kmemcheck_annotate_variable(var) \
do { \
kmemcheck_mark_initialized(&(var), sizeof(var)); \
} while (0) \
#define kmemcheck_annotate_variable(var) \
do { \
} while (0)
#endif /* CONFIG_KMEMCHECK */
#endif /* LINUX_KMEMCHECK_H */