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The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
67 lines
1.7 KiB
C
67 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef __LINUX_CPU_RMAP_H
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#define __LINUX_CPU_RMAP_H
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/*
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* cpu_rmap.c: CPU affinity reverse-map support
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* Copyright 2011 Solarflare Communications Inc.
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*/
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#include <linux/cpumask.h>
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#include <linux/gfp.h>
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#include <linux/slab.h>
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#include <linux/kref.h>
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/**
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* struct cpu_rmap - CPU affinity reverse-map
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* @refcount: kref for object
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* @size: Number of objects to be reverse-mapped
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* @used: Number of objects added
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* @obj: Pointer to array of object pointers
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* @near: For each CPU, the index and distance to the nearest object,
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* based on affinity masks
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*/
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struct cpu_rmap {
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struct kref refcount;
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u16 size, used;
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void **obj;
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struct {
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u16 index;
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u16 dist;
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} near[];
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};
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#define CPU_RMAP_DIST_INF 0xffff
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extern struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags);
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extern int cpu_rmap_put(struct cpu_rmap *rmap);
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extern int cpu_rmap_add(struct cpu_rmap *rmap, void *obj);
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extern int cpu_rmap_update(struct cpu_rmap *rmap, u16 index,
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const struct cpumask *affinity);
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static inline u16 cpu_rmap_lookup_index(struct cpu_rmap *rmap, unsigned int cpu)
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{
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return rmap->near[cpu].index;
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}
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static inline void *cpu_rmap_lookup_obj(struct cpu_rmap *rmap, unsigned int cpu)
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{
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return rmap->obj[rmap->near[cpu].index];
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}
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/**
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* alloc_irq_cpu_rmap - allocate CPU affinity reverse-map for IRQs
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* @size: Number of objects to be mapped
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*
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* Must be called in process context.
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*/
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static inline struct cpu_rmap *alloc_irq_cpu_rmap(unsigned int size)
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{
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return alloc_cpu_rmap(size, GFP_KERNEL);
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}
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extern void free_irq_cpu_rmap(struct cpu_rmap *rmap);
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extern int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq);
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#endif /* __LINUX_CPU_RMAP_H */
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