During refactor in commit 9e478066eae4 ("mac80211: fix MU-MIMO
follow-MAC mode") a new struct 'action' was declared with packed
attribute as:
struct {
struct ieee80211_hdr_3addr hdr;
u8 category;
u8 action_code;
} __packed action;
But since struct 'ieee80211_hdr_3addr' is declared with an aligned
keyword as:
struct ieee80211_hdr {
__le16 frame_control;
__le16 duration_id;
u8 addr1[ETH_ALEN];
u8 addr2[ETH_ALEN];
u8 addr3[ETH_ALEN];
__le16 seq_ctrl;
u8 addr4[ETH_ALEN];
} __packed __aligned(2);
Solve the ambiguity of placing aligned structure in a packed one by
removing the packed attribute from struct. This seems to be the behavior
of gcc anyway, since the following is still compiling:
BUILD_BUG_ON(sizeof(action) != IEEE80211_MIN_ACTION_SIZE + 1);
This removes the following warning (W=1):
net/mac80211/rx.c:234:2: warning: alignment 1 of 'struct <anonymous>' is less than 2 [-Wpacked-not-aligned]
Cc: Johannes Berg <[email protected]>
Signed-off-by: Mathieu Malaterre <[email protected]>
---
net/mac80211/rx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 45aad3d3108c..709359650149 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -231,7 +231,7 @@ static void ieee80211_handle_mu_mimo_mon(struct ieee80211_sub_if_data *sdata,
struct ieee80211_hdr_3addr hdr;
u8 category;
u8 action_code;
- } __packed action;
+ } action;
if (!sdata)
return;
--
2.19.2
On Thu, Jan 24, 2019 at 7:08 PM Johannes Berg <[email protected]> wrote:
>
> On Thu, 2019-01-24 at 19:05 +0100, Mathieu Malaterre wrote:
> > During refactor in commit 9e478066eae4 ("mac80211: fix MU-MIMO
> > follow-MAC mode") a new struct 'action' was declared with packed
> > attribute as:
> >
> > struct {
> > struct ieee80211_hdr_3addr hdr;
> > u8 category;
> > u8 action_code;
> > } __packed action;
> >
> > But since struct 'ieee80211_hdr_3addr' is declared with an aligned
> > keyword as:
> >
> > struct ieee80211_hdr {
> > __le16 frame_control;
> > __le16 duration_id;
> > u8 addr1[ETH_ALEN];
> > u8 addr2[ETH_ALEN];
> > u8 addr3[ETH_ALEN];
> > __le16 seq_ctrl;
> > u8 addr4[ETH_ALEN];
> > } __packed __aligned(2);
> >
> > Solve the ambiguity of placing aligned structure in a packed one by
> > removing the packed attribute from struct. This seems to be the behavior
> > of gcc anyway, since the following is still compiling:
> >
> > BUILD_BUG_ON(sizeof(action) != IEEE80211_MIN_ACTION_SIZE + 1);
>
> I'm not sure this will work on all platforms, didn't something like
> alpha pad out u8's to u32 when not requiring packing?
I was not aware of that.
> I guess I'd feel better about using __packed __aligned(2) here as well,
> which should solve the warning too?
Indeed, I will re-spin a v2 then.
During refactor in commit 9e478066eae4 ("mac80211: fix MU-MIMO
follow-MAC mode") a new struct 'action' was declared with packed
attribute as:
struct {
struct ieee80211_hdr_3addr hdr;
u8 category;
u8 action_code;
} __packed action;
But since struct 'ieee80211_hdr_3addr' is declared with an aligned
keyword as:
struct ieee80211_hdr {
__le16 frame_control;
__le16 duration_id;
u8 addr1[ETH_ALEN];
u8 addr2[ETH_ALEN];
u8 addr3[ETH_ALEN];
__le16 seq_ctrl;
u8 addr4[ETH_ALEN];
} __packed __aligned(2);
Solve the ambiguity of placing aligned structure in a packed one by
adding the aligned(2) attribute to struct 'action'. This seems to be the
behavior of gcc anyway, since the following is still compiling:
BUILD_BUG_ON(sizeof(action) != IEEE80211_MIN_ACTION_SIZE + 1);
This removes the following warning (W=1):
net/mac80211/rx.c:234:2: warning: alignment 1 of 'struct <anonymous>' is less than 2 [-Wpacked-not-aligned]
Cc: Johannes Berg <[email protected]>
Suggested-by: Johannes Berg <[email protected]>
Signed-off-by: Mathieu Malaterre <[email protected]>
---
v2: It was suggested by Johannes that an arch actually need the pack attribute (alpha).
net/mac80211/rx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 45aad3d3108c..885df250b67e 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -231,7 +231,7 @@ static void ieee80211_handle_mu_mimo_mon(struct ieee80211_sub_if_data *sdata,
struct ieee80211_hdr_3addr hdr;
u8 category;
u8 action_code;
- } __packed action;
+ } __packed __aligned(2) action;
if (!sdata)
return;
--
2.19.2
On Thu, 2019-01-24 at 19:14 +0100, Mathieu Malaterre wrote:
> > I'm not sure this will work on all platforms, didn't something like
> > alpha pad out u8's to u32 when not requiring packing?
>
> I was not aware of that.
TBH, I'm not actually sure about that. Pure hearsay. If anyone knows,
I'd like to know too :)
johannes
On Thu, 2019-01-24 at 19:05 +0100, Mathieu Malaterre wrote:
> During refactor in commit 9e478066eae4 ("mac80211: fix MU-MIMO
> follow-MAC mode") a new struct 'action' was declared with packed
> attribute as:
>
> struct {
> struct ieee80211_hdr_3addr hdr;
> u8 category;
> u8 action_code;
> } __packed action;
>
> But since struct 'ieee80211_hdr_3addr' is declared with an aligned
> keyword as:
>
> struct ieee80211_hdr {
> __le16 frame_control;
> __le16 duration_id;
> u8 addr1[ETH_ALEN];
> u8 addr2[ETH_ALEN];
> u8 addr3[ETH_ALEN];
> __le16 seq_ctrl;
> u8 addr4[ETH_ALEN];
> } __packed __aligned(2);
>
> Solve the ambiguity of placing aligned structure in a packed one by
> removing the packed attribute from struct. This seems to be the behavior
> of gcc anyway, since the following is still compiling:
>
> BUILD_BUG_ON(sizeof(action) != IEEE80211_MIN_ACTION_SIZE + 1);
I'm not sure this will work on all platforms, didn't something like
alpha pad out u8's to u32 when not requiring packing?
I guess I'd feel better about using __packed __aligned(2) here as well,
which should solve the warning too?
johannes