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container_of does not preserve the const-ness of a pointer that is passed into it, which can cause C code that passes in a const pointer to get a pointer back that is not const and then scribble all over the data in it. To prevent this, container_of_const() will preserve the const status of the pointer passed into it using the newly available _Generic() method. Suggested-by: Jason Gunthorpe <jgg@ziepe.ca> Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com> Acked-by: Rafael J. Wysocki <rafael@kernel.org> Link: https://lore.kernel.org/r/20221205121206.166576-1-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
38 lines
1.3 KiB
C
38 lines
1.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_CONTAINER_OF_H
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#define _LINUX_CONTAINER_OF_H
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#include <linux/build_bug.h>
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#include <linux/err.h>
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#define typeof_member(T, m) typeof(((T*)0)->m)
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/**
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* container_of - cast a member of a structure out to the containing structure
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* @ptr: the pointer to the member.
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* @type: the type of the container struct this is embedded in.
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* @member: the name of the member within the struct.
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*
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* WARNING: any const qualifier of @ptr is lost.
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*/
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#define container_of(ptr, type, member) ({ \
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void *__mptr = (void *)(ptr); \
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static_assert(__same_type(*(ptr), ((type *)0)->member) || \
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__same_type(*(ptr), void), \
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"pointer type mismatch in container_of()"); \
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((type *)(__mptr - offsetof(type, member))); })
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/**
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* container_of_const - cast a member of a structure out to the containing
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* structure and preserve the const-ness of the pointer
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* @ptr: the pointer to the member
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* @type: the type of the container struct this is embedded in.
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* @member: the name of the member within the struct.
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*/
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#define container_of_const(ptr, type, member) \
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_Generic(ptr, \
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const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
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default: ((type *)container_of(ptr, type, member)) \
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)
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#endif /* _LINUX_CONTAINER_OF_H */
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