From: Boqun Feng <[email protected]> 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: Boqun Feng <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- include/linux/compiler.h | 12 ++++++++---- scripts/checkpatch.pl | 3 ++- 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 00b042c49ccd..c845356952bb 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -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 diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 0147c91fa549..874132b26d23 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -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)}; -- 2.5.2
