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 <boqun.feng@xxxxxxxxx>
---
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 4dac103..e4a4fb1 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 2b3c228..fda1c61 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)};
--
2.6.4
--
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