The patch titled
Subject: kernel.h: disable type-checks in container_of() for Sparse
has been added to the -mm tree. Its filename is
kernelh-disable-type-checks-in-container_of-for-sparse.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernelh-disable-type-checks-in-container_of-for-sparse.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernelh-disable-type-checks-in-container_of-for-sparse.patch
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From: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Subject: kernel.h: disable type-checks in container_of() for Sparse
When I tried to enable BUILD_BUG_ON for Sparse, the kbuild test robot
reported lots of "unknown expression" warnings from container_of(), which
seemed false positive.
I addressed this in [1], but fixing Sparse is the right thing to do.
The issue was fixed by Sparse commit 0eb8175d3e9c ("fix expansion of
function designator"), but it will take time until the fixed version of
Sparse is widely available.
Disable the container_of() type checks for Sparse for now.
[1] https://lore.kernel.org/lkml/1542623503-3755-1-git-send-email-yamada.masahiro@xxxxxxxxxxxxx/
Link: http://lkml.kernel.org/r/1542856462-18836-1-git-send-email-yamada.masahiro@xxxxxxxxxxxxx
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/kernel.h~kernelh-disable-type-checks-in-container_of-for-sparse
+++ a/include/linux/kernel.h
@@ -985,6 +985,21 @@ static inline void ftrace_dump(enum ftra
#define __CONCAT(a, b) a ## b
#define CONCATENATE(a, b) __CONCAT(a, b)
+/*
+ * TODO:
+ * Sparse emits "unknown expression" warnings.
+ * It was fixed by commit 0eb8175d3e9c0d20354763d07ce3d4c0e543d988 in Sparse.
+ * Remove the following workaround when the fixed Sparse is widely available.
+ */
+#ifdef __CHECKER__
+#define TYPE_CHECK_CONTAINER_OF(ptr, type, member) do {} while (0)
+#else
+#define TYPE_CHECK_CONTAINER_OF(ptr, type, member) \
+ BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
+ !__same_type(*(ptr), void), \
+ "pointer type mismatch in container_of()")
+#endif
+
/**
* container_of - cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
@@ -994,9 +1009,7 @@ static inline void ftrace_dump(enum ftra
*/
#define container_of(ptr, type, member) ({ \
void *__mptr = (void *)(ptr); \
- BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
- !__same_type(*(ptr), void), \
- "pointer type mismatch in container_of()"); \
+ TYPE_CHECK_CONTAINER_OF(ptr, type, member); \
((type *)(__mptr - offsetof(type, member))); })
/**
@@ -1009,9 +1022,7 @@ static inline void ftrace_dump(enum ftra
*/
#define container_of_safe(ptr, type, member) ({ \
void *__mptr = (void *)(ptr); \
- BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
- !__same_type(*(ptr), void), \
- "pointer type mismatch in container_of()"); \
+ TYPE_CHECK_CONTAINER_OF(ptr, type, member); \
IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) : \
((type *)(__mptr - offsetof(type, member))); })
_
Patches currently in -mm which might be from yamada.masahiro@xxxxxxxxxxxxx are
kernelh-disable-type-checks-in-container_of-for-sparse.patch
build_bugh-remove-negative-array-fallback-for-build_bug_on.patch
build_bugh-remove-most-of-dummy-build_bug_on-stubs-for-sparse.patch
