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bpf: Avoid -Wflex-array-members-not-at-end warnings

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Apparently, struct bpf_empty_prog_array exists entirely to populate a
single element of "items" in a global variable. "null_prog" is only
used during the initializer.

None of this is needed; globals will be correctly sized with an array
initializer of a flexible-array member.

So, remove struct bpf_empty_prog_array and adjust the rest of the code,
accordingly.

With these changes, fix the following warnings:

./include/linux/bpf.h:2369:31: warning: structure containing a flexible
array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/acr7Whmn0br3xeBP@kspp
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Gustavo A. R. Silva 2026-03-30 16:38:18 -06:00 committed by Alexei Starovoitov
parent 42e33c9af4
commit 18474aed5d
3 changed files with 9 additions and 12 deletions
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2
include/linux/bpf-cgroup.h
View File

@ -184,7 +184,7 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk,
struct bpf_prog_array *array;
array = rcu_access_pointer(cgrp->bpf.effective[type]);
return array != &bpf_empty_prog_array.hdr;
return array != &bpf_empty_prog_array;
}
/* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */

7
include/linux/bpf.h
View File

@ -2369,18 +2369,13 @@ struct bpf_prog_array {
struct bpf_prog_array_item items[];
};
struct bpf_empty_prog_array {
struct bpf_prog_array hdr;
struct bpf_prog *null_prog;
};
/* to avoid allocating empty bpf_prog_array for cgroups that
* don't have bpf program attached use one global 'bpf_empty_prog_array'
* It will not be modified the caller of bpf_prog_array_alloc()
* (since caller requested prog_cnt == 0)
* that pointer should be 'freed' by bpf_prog_array_free()
*/
extern struct bpf_empty_prog_array bpf_empty_prog_array;
extern struct bpf_prog_array bpf_empty_prog_array;
struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
void bpf_prog_array_free(struct bpf_prog_array *progs);

12
kernel/bpf/core.c
View File

@ -2614,8 +2614,10 @@ static struct bpf_prog_dummy {
},
};
struct bpf_empty_prog_array bpf_empty_prog_array = {
.null_prog = NULL,
struct bpf_prog_array bpf_empty_prog_array = {
.items = {
{ .prog = NULL },
},
};
EXPORT_SYMBOL(bpf_empty_prog_array);
@ -2626,14 +2628,14 @@ struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags)
if (prog_cnt)
p = kzalloc_flex(*p, items, prog_cnt + 1, flags);
else
p = &bpf_empty_prog_array.hdr;
p = &bpf_empty_prog_array;
return p;
}
void bpf_prog_array_free(struct bpf_prog_array *progs)
{
if (!progs || progs == &bpf_empty_prog_array.hdr)
if (!progs || progs == &bpf_empty_prog_array)
return;
kfree_rcu(progs, rcu);
}
@ -2654,7 +2656,7 @@ static void __bpf_prog_array_free_sleepable_cb(struct rcu_head *rcu)
void bpf_prog_array_free_sleepable(struct bpf_prog_array *progs)
{
if (!progs || progs == &bpf_empty_prog_array.hdr)
if (!progs || progs == &bpf_empty_prog_array)
return;
call_rcu_tasks_trace(&progs->rcu, __bpf_prog_array_free_sleepable_cb);
}