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Commit e992cd9b authored by Vegard Nossum's avatar Vegard Nossum Committed by Linus Torvalds
Browse files

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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarVegard Nossum <vegard.nossum@gmail.com>
Acked-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cb5a8b2c

include/linux/kmemcheck.h

+58 −52
Original line number Diff line number Diff line
@@ -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_bitfield_begin(name)

#define kmemcheck_bitfield_end(name)

#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)							\

	} while (0)



#endif /* CONFIG_KMEMCHECK */



#endif /* LINUX_KMEMCHECK_H */