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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")
Link: https://lkml.kernel.org/r/20200221150612.GA9717@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
113 lines
2.5 KiB
C
113 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright IBM Corp. 2007, 2012
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* Author(s): Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
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*/
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#include <linux/vmalloc.h>
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#include <linux/bitmap.h>
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#include <linux/bitops.h>
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#include "idset.h"
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#include "css.h"
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struct idset {
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int num_ssid;
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int num_id;
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unsigned long bitmap[];
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};
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static inline unsigned long bitmap_size(int num_ssid, int num_id)
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{
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return BITS_TO_LONGS(num_ssid * num_id) * sizeof(unsigned long);
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}
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static struct idset *idset_new(int num_ssid, int num_id)
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{
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struct idset *set;
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set = vmalloc(sizeof(struct idset) + bitmap_size(num_ssid, num_id));
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if (set) {
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set->num_ssid = num_ssid;
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set->num_id = num_id;
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memset(set->bitmap, 0, bitmap_size(num_ssid, num_id));
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}
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return set;
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}
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void idset_free(struct idset *set)
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{
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vfree(set);
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}
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void idset_fill(struct idset *set)
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{
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memset(set->bitmap, 0xff, bitmap_size(set->num_ssid, set->num_id));
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}
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static inline void idset_add(struct idset *set, int ssid, int id)
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{
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set_bit(ssid * set->num_id + id, set->bitmap);
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}
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static inline void idset_del(struct idset *set, int ssid, int id)
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{
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clear_bit(ssid * set->num_id + id, set->bitmap);
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}
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static inline int idset_contains(struct idset *set, int ssid, int id)
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{
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return test_bit(ssid * set->num_id + id, set->bitmap);
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}
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static inline int idset_get_first(struct idset *set, int *ssid, int *id)
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{
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int bitnum;
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bitnum = find_first_bit(set->bitmap, set->num_ssid * set->num_id);
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if (bitnum >= set->num_ssid * set->num_id)
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return 0;
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*ssid = bitnum / set->num_id;
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*id = bitnum % set->num_id;
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return 1;
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}
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struct idset *idset_sch_new(void)
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{
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return idset_new(max_ssid + 1, __MAX_SUBCHANNEL + 1);
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}
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void idset_sch_add(struct idset *set, struct subchannel_id schid)
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{
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idset_add(set, schid.ssid, schid.sch_no);
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}
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void idset_sch_del(struct idset *set, struct subchannel_id schid)
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{
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idset_del(set, schid.ssid, schid.sch_no);
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}
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/* Clear ids starting from @schid up to end of subchannel set. */
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void idset_sch_del_subseq(struct idset *set, struct subchannel_id schid)
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{
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int pos = schid.ssid * set->num_id + schid.sch_no;
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bitmap_clear(set->bitmap, pos, set->num_id - schid.sch_no);
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}
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int idset_sch_contains(struct idset *set, struct subchannel_id schid)
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{
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return idset_contains(set, schid.ssid, schid.sch_no);
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}
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int idset_is_empty(struct idset *set)
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{
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return bitmap_empty(set->bitmap, set->num_ssid * set->num_id);
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}
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void idset_add_set(struct idset *to, struct idset *from)
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{
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int len = min(to->num_ssid * to->num_id, from->num_ssid * from->num_id);
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bitmap_or(to->bitmap, to->bitmap, from->bitmap, len);
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}
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