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author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2022-08-31 14:12:42 -0500 |
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committer | David S. Miller <davem@davemloft.net> | 2022-09-03 09:51:10 +0100 |
commit | 5854a09b49574da5a77a0f36ad7b021a2661321d (patch) | |
tree | ec3173bf11696cd1db2c3866a5690844f72ab9b6 /include/uapi/linux/in.h | |
parent | net/sched: cls_api: remove redundant 0 check in tcf_qevent_init() (diff) | |
download | linux-5854a09b49574da5a77a0f36ad7b021a2661321d.tar.xz linux-5854a09b49574da5a77a0f36ad7b021a2661321d.zip |
net/ipv4: Use __DECLARE_FLEX_ARRAY() helper
We now have a cleaner way to keep compatibility with user-space
(a.k.a. not breaking it) when we need to keep in place a one-element
array (for its use in user-space) together with a flexible-array
member (for its use in kernel-space) without making it hard to read
at the source level. This is through the use of the new
__DECLARE_FLEX_ARRAY() helper macro.
The size and memory layout of the structure is preserved after the
changes. See below.
Before changes:
$ pahole -C ip_msfilter net/ipv4/igmp.o
struct ip_msfilter {
union {
struct {
__be32 imsf_multiaddr_aux; /* 0 4 */
__be32 imsf_interface_aux; /* 4 4 */
__u32 imsf_fmode_aux; /* 8 4 */
__u32 imsf_numsrc_aux; /* 12 4 */
__be32 imsf_slist[1]; /* 16 4 */
}; /* 0 20 */
struct {
__be32 imsf_multiaddr; /* 0 4 */
__be32 imsf_interface; /* 4 4 */
__u32 imsf_fmode; /* 8 4 */
__u32 imsf_numsrc; /* 12 4 */
__be32 imsf_slist_flex[0]; /* 16 0 */
}; /* 0 16 */
}; /* 0 20 */
/* size: 20, cachelines: 1, members: 1 */
/* last cacheline: 20 bytes */
};
After changes:
$ pahole -C ip_msfilter net/ipv4/igmp.o
struct ip_msfilter {
__be32 imsf_multiaddr; /* 0 4 */
__be32 imsf_interface; /* 4 4 */
__u32 imsf_fmode; /* 8 4 */
__u32 imsf_numsrc; /* 12 4 */
union {
__be32 imsf_slist[1]; /* 16 4 */
struct {
struct {
} __empty_imsf_slist_flex; /* 16 0 */
__be32 imsf_slist_flex[0]; /* 16 0 */
}; /* 16 0 */
}; /* 16 4 */
/* size: 20, cachelines: 1, members: 5 */
/* last cacheline: 20 bytes */
};
In the past, we had to duplicate the whole original structure within
a union, and update the names of all the members. Now, we just need to
declare the flexible-array member to be used in kernel-space through
the __DECLARE_FLEX_ARRAY() helper together with the one-element array,
within a union. This makes the source code more clean and easier to read.
Link: https://github.com/KSPP/linux/issues/193
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/uapi/linux/in.h')
-rw-r--r-- | include/uapi/linux/in.h | 20 |
1 files changed, 6 insertions, 14 deletions
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h index 14168225cecd..578daa6f816b 100644 --- a/include/uapi/linux/in.h +++ b/include/uapi/linux/in.h @@ -188,21 +188,13 @@ struct ip_mreq_source { }; struct ip_msfilter { + __be32 imsf_multiaddr; + __be32 imsf_interface; + __u32 imsf_fmode; + __u32 imsf_numsrc; union { - struct { - __be32 imsf_multiaddr_aux; - __be32 imsf_interface_aux; - __u32 imsf_fmode_aux; - __u32 imsf_numsrc_aux; - __be32 imsf_slist[1]; - }; - struct { - __be32 imsf_multiaddr; - __be32 imsf_interface; - __u32 imsf_fmode; - __u32 imsf_numsrc; - __be32 imsf_slist_flex[]; - }; + __be32 imsf_slist[1]; + __DECLARE_FLEX_ARRAY(__be32, imsf_slist_flex); }; }; |