This is like container_of_const() but it contains an assert to ensure that it's using the first member in the structure.
Co-developed-by: Dan Carpenter <dan.carpen...@linaro.org> Signed-off-by: Dan Carpenter <dan.carpen...@linaro.org> Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org> --- I will be using this in my -Wflex-array-member-not-at-end patches. :) Changes in v2: - Base this on container_of_const(). v1: - Link: https://lore.kernel.org/linux-hardening/Zu1vekikKNR5oUoM@elsanto/ include/linux/container_of.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/container_of.h b/include/linux/container_of.h index 713890c867be..1a5e5f32db92 100644 --- a/include/linux/container_of.h +++ b/include/linux/container_of.h @@ -35,4 +35,15 @@ default: ((type *)container_of(ptr, type, member)) \ ) +/** + * container_first - cast first member of a structure out to the containing + * structure and preserve the const-ness of the pointer. + * @ptr: the pointer to the member. + * @type: the type of the container struct this is embedded in. + * @member: the name of the member within the struct. + */ +#define container_first(ptr, type, member) ({ \ + static_assert(offsetof(type, member) == 0, "not first member"); \ + container_of_const(ptr, type, member); }) + #endif /* _LINUX_CONTAINER_OF_H */ -- 2.43.0
