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lib min_heap: improve type safety in min_heap macros by using contain…
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…er_of

Patch series "lib min_heap: Improve min_heap safety, testing, and
documentation".

Improve the min heap implementation by enhancing type safety with
container_of, reducing the attack vector by replacing test function calls
with inline variants, and adding a brief API introduction in min_heap.h. 
It also includes author information in
Documentation/core-api/min_heap.rst.


This patch (of 4):

The current implementation of min_heap macros uses explicit casting to
min_heap_char *, which prevents the compiler from detecting incorrect
pointer types.  This can lead to errors if non-min_heap pointers are
passed inadvertently.

To enhance safety, replace all explicit casts to min_heap_char * with the
use of container_of(&(_heap)->nr, min_heap_char, nr).  This approach
ensures that the _heap parameter is indeed a min_heap_char-compatible
structure, allowing the compiler to catch improper usages.

Link: https://lkml.kernel.org/r/20241129181222.646855-1-visitorckw@gmail.com
Link: https://lore.kernel.org/lkml/CAMuHMdVO5DPuD9HYWBFqKDHphx7+0BEhreUxtVC40A=8p6VAhQ@mail.gmail.com
Link: https://lkml.kernel.org/r/20241129181222.646855-2-visitorckw@gmail.com
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Kuan-Wei Chiu authored and Andrew Morton committed Jan 13, 2025
1 parent cd6313b commit ec01e9d
Showing 1 changed file with 35 additions and 26 deletions.
61 changes: 35 additions & 26 deletions include/linux/min_heap.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -218,7 +218,7 @@ void __min_heap_init_inline(min_heap_char *heap, void *data, int size)
}

#define min_heap_init_inline(_heap, _data, _size) \
__min_heap_init_inline((min_heap_char *)_heap, _data, _size)
__min_heap_init_inline(container_of(&(_heap)->nr, min_heap_char, nr), _data, _size)

/* Get the minimum element from the heap. */
static __always_inline
Expand All @@ -228,7 +228,8 @@ void *__min_heap_peek_inline(struct min_heap_char *heap)
}

#define min_heap_peek_inline(_heap) \
(__minheap_cast(_heap) __min_heap_peek_inline((min_heap_char *)_heap))
(__minheap_cast(_heap) \
__min_heap_peek_inline(container_of(&(_heap)->nr, min_heap_char, nr)))

/* Check if the heap is full. */
static __always_inline
Expand All @@ -238,7 +239,7 @@ bool __min_heap_full_inline(min_heap_char *heap)
}

#define min_heap_full_inline(_heap) \
__min_heap_full_inline((min_heap_char *)_heap)
__min_heap_full_inline(container_of(&(_heap)->nr, min_heap_char, nr))

/* Sift the element at pos down the heap. */
static __always_inline
Expand Down Expand Up @@ -277,8 +278,8 @@ void __min_heap_sift_down_inline(min_heap_char *heap, int pos, size_t elem_size,
}

#define min_heap_sift_down_inline(_heap, _pos, _func, _args) \
__min_heap_sift_down_inline((min_heap_char *)_heap, _pos, __minheap_obj_size(_heap), \
_func, _args)
__min_heap_sift_down_inline(container_of(&(_heap)->nr, min_heap_char, nr), _pos, \
__minheap_obj_size(_heap), _func, _args)

/* Sift up ith element from the heap, O(log2(nr)). */
static __always_inline
Expand All @@ -304,8 +305,8 @@ void __min_heap_sift_up_inline(min_heap_char *heap, size_t elem_size, size_t idx
}

#define min_heap_sift_up_inline(_heap, _idx, _func, _args) \
__min_heap_sift_up_inline((min_heap_char *)_heap, __minheap_obj_size(_heap), _idx, \
_func, _args)
__min_heap_sift_up_inline(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _idx, _func, _args)

/* Floyd's approach to heapification that is O(nr). */
static __always_inline
Expand All @@ -319,7 +320,8 @@ void __min_heapify_all_inline(min_heap_char *heap, size_t elem_size,
}

#define min_heapify_all_inline(_heap, _func, _args) \
__min_heapify_all_inline((min_heap_char *)_heap, __minheap_obj_size(_heap), _func, _args)
__min_heapify_all_inline(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _func, _args)

/* Remove minimum element from the heap, O(log2(nr)). */
static __always_inline
Expand All @@ -340,7 +342,8 @@ bool __min_heap_pop_inline(min_heap_char *heap, size_t elem_size,
}

#define min_heap_pop_inline(_heap, _func, _args) \
__min_heap_pop_inline((min_heap_char *)_heap, __minheap_obj_size(_heap), _func, _args)
__min_heap_pop_inline(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _func, _args)

/*
* Remove the minimum element and then push the given element. The
Expand All @@ -356,8 +359,8 @@ void __min_heap_pop_push_inline(min_heap_char *heap, const void *element, size_t
}

#define min_heap_pop_push_inline(_heap, _element, _func, _args) \
__min_heap_pop_push_inline((min_heap_char *)_heap, _element, __minheap_obj_size(_heap), \
_func, _args)
__min_heap_pop_push_inline(container_of(&(_heap)->nr, min_heap_char, nr), _element, \
__minheap_obj_size(_heap), _func, _args)

/* Push an element on to the heap, O(log2(nr)). */
static __always_inline
Expand All @@ -382,8 +385,8 @@ bool __min_heap_push_inline(min_heap_char *heap, const void *element, size_t ele
}

#define min_heap_push_inline(_heap, _element, _func, _args) \
__min_heap_push_inline((min_heap_char *)_heap, _element, __minheap_obj_size(_heap), \
_func, _args)
__min_heap_push_inline(container_of(&(_heap)->nr, min_heap_char, nr), _element, \
__minheap_obj_size(_heap), _func, _args)

/* Remove ith element from the heap, O(log2(nr)). */
static __always_inline
Expand Down Expand Up @@ -411,8 +414,8 @@ bool __min_heap_del_inline(min_heap_char *heap, size_t elem_size, size_t idx,
}

#define min_heap_del_inline(_heap, _idx, _func, _args) \
__min_heap_del_inline((min_heap_char *)_heap, __minheap_obj_size(_heap), _idx, \
_func, _args)
__min_heap_del_inline(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _idx, _func, _args)

void __min_heap_init(min_heap_char *heap, void *data, int size);
void *__min_heap_peek(struct min_heap_char *heap);
Expand All @@ -433,25 +436,31 @@ bool __min_heap_del(min_heap_char *heap, size_t elem_size, size_t idx,
const struct min_heap_callbacks *func, void *args);

#define min_heap_init(_heap, _data, _size) \
__min_heap_init((min_heap_char *)_heap, _data, _size)
__min_heap_init(container_of(&(_heap)->nr, min_heap_char, nr), _data, _size)
#define min_heap_peek(_heap) \
(__minheap_cast(_heap) __min_heap_peek((min_heap_char *)_heap))
(__minheap_cast(_heap) __min_heap_peek(container_of(&(_heap)->nr, min_heap_char, nr)))
#define min_heap_full(_heap) \
__min_heap_full((min_heap_char *)_heap)
__min_heap_full(container_of(&(_heap)->nr, min_heap_char, nr))
#define min_heap_sift_down(_heap, _pos, _func, _args) \
__min_heap_sift_down((min_heap_char *)_heap, _pos, __minheap_obj_size(_heap), _func, _args)
__min_heap_sift_down(container_of(&(_heap)->nr, min_heap_char, nr), _pos, \
__minheap_obj_size(_heap), _func, _args)
#define min_heap_sift_up(_heap, _idx, _func, _args) \
__min_heap_sift_up((min_heap_char *)_heap, __minheap_obj_size(_heap), _idx, _func, _args)
__min_heap_sift_up(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _idx, _func, _args)
#define min_heapify_all(_heap, _func, _args) \
__min_heapify_all((min_heap_char *)_heap, __minheap_obj_size(_heap), _func, _args)
__min_heapify_all(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _func, _args)
#define min_heap_pop(_heap, _func, _args) \
__min_heap_pop((min_heap_char *)_heap, __minheap_obj_size(_heap), _func, _args)
__min_heap_pop(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _func, _args)
#define min_heap_pop_push(_heap, _element, _func, _args) \
__min_heap_pop_push((min_heap_char *)_heap, _element, __minheap_obj_size(_heap), \
_func, _args)
__min_heap_pop_push(container_of(&(_heap)->nr, min_heap_char, nr), _element, \
__minheap_obj_size(_heap), _func, _args)
#define min_heap_push(_heap, _element, _func, _args) \
__min_heap_push((min_heap_char *)_heap, _element, __minheap_obj_size(_heap), _func, _args)
__min_heap_push(container_of(&(_heap)->nr, min_heap_char, nr), _element, \
__minheap_obj_size(_heap), _func, _args)
#define min_heap_del(_heap, _idx, _func, _args) \
__min_heap_del((min_heap_char *)_heap, __minheap_obj_size(_heap), _idx, _func, _args)
__min_heap_del(container_of(&(_heap)->nr, min_heap_char, nr), \
__minheap_obj_size(_heap), _idx, _func, _args)

#endif /* _LINUX_MIN_HEAP_H */

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