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Commit ad315455 authored by Boqun Feng's avatar Boqun Feng Committed by Paul E. McKenney
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sparse: Add __private to privatize members of structs 



In C programming language, we don't have a easy way to privatize a
member of a structure. However in kernel, sometimes there is a need to
privatize a member in case of potential bugs or misuses.

Fortunately, the noderef attribute of sparse is a way to privatize a
member, as by defining a member as noderef, the address-of operator on
the member will produce a noderef pointer to that member, and if anyone
wants to dereference that kind of pointers to read or modify the member,
sparse will yell.

Based on this, __private modifier and related operation ACCESS_PRIVATE()
are introduced, which could help detect undesigned public uses of
private members of structs. Here is an example of sparse's output if it
detect an undersigned public use:

| kernel/rcu/tree.c:4453:25: warning: incorrect type in argument 1 (different modifiers)
| kernel/rcu/tree.c:4453:25:    expected struct raw_spinlock [usertype] *lock
| kernel/rcu/tree.c:4453:25:    got struct raw_spinlock [noderef] *<noident>

Also, this patch improves compiler.h a little bit by adding comments for
"#else" and "#endif".

Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 1914aab5

include/linux/compiler.h

+8 −4
Original line number Diff line number Diff line
@@ -20,12 +20,14 @@ 
# define __pmem		__attribute__((noderef, address_space(5)))

#ifdef CONFIG_SPARSE_RCU_POINTER

# define __rcu		__attribute__((noderef, address_space(4)))

#else

#else /* CONFIG_SPARSE_RCU_POINTER */

# define __rcu

#endif

#endif /* CONFIG_SPARSE_RCU_POINTER */

# define __private	__attribute__((noderef))

extern void __chk_user_ptr(const volatile void __user *);

extern void __chk_io_ptr(const volatile void __iomem *);

#else

# define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member))

#else /* __CHECKER__ */

# define __user

# define __kernel

# define __safe
@@ -44,7 +46,9 @@ extern void __chk_io_ptr(const volatile void __iomem *); 
# define __percpu

# define __rcu

# define __pmem

#endif

# define __private

# define ACCESS_PRIVATE(p, member) ((p)->member)

#endif /* __CHECKER__ */



/* Indirect macros required for expanded argument pasting, eg. __LINE__. */

#define ___PASTE(a,b) a##b

scripts/checkpatch.pl

+2 −1
Original line number Diff line number Diff line
@@ -269,7 +269,8 @@ our $Sparse = qr{ 
			__init_refok|

			__kprobes|

			__ref|

			__rcu

			__rcu|

			__private

		}x;

our $InitAttributePrefix = qr{__(?:mem|cpu|dev|net_|)};

our $InitAttributeData = qr{$InitAttributePrefix(?:initdata\b)};