[PATCH] [-next] net: marvell: prestera: Add explicit padding

[PATCH] [-next] net: marvell: prestera: Add explicit padding

[Geert Uytterhoeven]

On m68k:

    In function ‘prestera_hw_build_tests’,
	inlined from ‘prestera_hw_switch_init’ at drivers/net/ethernet/marvell/prestera/prestera_hw.c:788:2:
    ././include/linux/compiler_types.h:335:38: error: call to ‘__compiletime_assert_345’ declared with attribute error: BUILD_BUG_ON failed: sizeof(struct prestera_msg_switch_attr_req) != 16
    ...

The driver assumes structure members are naturally aligned, but does not
add explicit padding, thus breaking architectures where integral values
are not always naturally aligned (e.g. on m68k, __alignof(int) is 2, not
4).

Fixes: bb5dbf2cc64d5cfa ("net: marvell: prestera: add firmware v4.0 support")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Compile-tested only.

BTW, I sincerely doubt the use of __packed on structs like:

    union prestera_msg_switch_param {
	    u8 mac[ETH_ALEN];
	    __le32 ageing_timeout_ms;
    } __packed;

This struct is only used as a member in another struct, where it is
be naturally aligned anyway.

Some of the other __packed attributes look fishy to me, too.
---
 drivers/net/ethernet/marvell/prestera/prestera_hw.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/marvell/prestera/prestera_hw.c b/drivers/net/ethernet/marvell/prestera/prestera_hw.c
index 41ba17cb29657392..4f5f52dcdd9d2814 100644
--- a/drivers/net/ethernet/marvell/prestera/prestera_hw.c
+++ b/drivers/net/ethernet/marvell/prestera/prestera_hw.c
@@ -189,6 +189,7 @@ struct prestera_msg_switch_attr_req {
 	struct prestera_msg_cmd cmd;
 	__le32 attr;
 	union prestera_msg_switch_param param;
+	u8 pad[2];
 };
 
 struct prestera_msg_switch_init_resp {
@@ -313,6 +314,7 @@ struct prestera_msg_port_info_resp {
 	__le32 hw_id;
 	__le32 dev_id;
 	__le16 fp_id;
+	u8 pad[2];
 };
 
 struct prestera_msg_vlan_req {
@@ -345,11 +347,13 @@ struct prestera_msg_bridge_req {
 	__le32 port;
 	__le32 dev;
 	__le16 bridge;
+	u8 pad[2];
 };
 
 struct prestera_msg_bridge_resp {
 	struct prestera_msg_ret ret;
 	__le16 bridge;
+	u8 pad[2];
 };
 
 struct prestera_msg_acl_action {
@@ -408,16 +412,19 @@ struct prestera_msg_acl_ruleset_bind_req {
 	__le32 port;
 	__le32 dev;
 	__le16 ruleset_id;
+	u8 pad[2];
 };
 
 struct prestera_msg_acl_ruleset_req {
 	struct prestera_msg_cmd cmd;
 	__le16 id;
+	u8 pad[2];
 };
 
 struct prestera_msg_acl_ruleset_resp {
 	struct prestera_msg_ret ret;
 	__le16 id;
+	u8 pad[2];
 };
 
 struct prestera_msg_span_req {
@@ -425,11 +432,13 @@ struct prestera_msg_span_req {
 	__le32 port;
 	__le32 dev;
 	u8 id;
+	u8 pad[3];
 };
 
 struct prestera_msg_span_resp {
 	struct prestera_msg_ret ret;
 	u8 id;
+	u8 pad[3];
 };
 
 struct prestera_msg_stp_req {
@@ -443,6 +452,7 @@ struct prestera_msg_stp_req {
 struct prestera_msg_rxtx_req {
 	struct prestera_msg_cmd cmd;
 	u8 use_sdma;
+	u8 pad[3];
 };
 
 struct prestera_msg_rxtx_resp {
@@ -455,12 +465,14 @@ struct prestera_msg_lag_req {
 	__le32 port;
 	__le32 dev;
 	__le16 lag_id;
+	u8 pad[2];
 };
 
 struct prestera_msg_cpu_code_counter_req {
 	struct prestera_msg_cmd cmd;
 	u8 counter_type;
 	u8 code;
+	u8 pad[2];
 };
 
 struct mvsw_msg_cpu_code_counter_ret {
-- 
2.25.1

Re: [PATCH] [-next] net: marvell: prestera: Add explicit padding

[Arnd Bergmann]

On Tue, Nov 2, 2021 at 9:24 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> On m68k:
>
>     In function ‘prestera_hw_build_tests’,
>         inlined from ‘prestera_hw_switch_init’ at drivers/net/ethernet/marvell/prestera/prestera_hw.c:788:2:
>     ././include/linux/compiler_types.h:335:38: error: call to ‘__compiletime_assert_345’ declared with attribute error: BUILD_BUG_ON failed: sizeof(struct prestera_msg_switch_attr_req) != 16
>     ...
>
> The driver assumes structure members are naturally aligned, but does not
> add explicit padding, thus breaking architectures where integral values
> are not always naturally aligned (e.g. on m68k, __alignof(int) is 2, not
> 4).
>
> Fixes: bb5dbf2cc64d5cfa ("net: marvell: prestera: add firmware v4.0 support")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Looks good to me,

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

> Compile-tested only.
>
> BTW, I sincerely doubt the use of __packed on structs like:
>
>     union prestera_msg_switch_param {
>             u8 mac[ETH_ALEN];
>             __le32 ageing_timeout_ms;
>     } __packed;
>
> This struct is only used as a member in another struct, where it is
> be naturally aligned anyway.

Agreed, this __packed attribute is clearly bogus and should be removed.

Same for

+struct prestera_msg_event_port_param {
+       union {
+               struct {
+                       u8 oper;
+                       __le32 mode;
+                       __le32 speed;
+                       u8 duplex;
+                       u8 fc;
+                       u8 fec;
+               } __packed mac;
+               struct {
+                       u8 mdix;
+                       __le64 lmode_bmap;
+                       u8 fc;
+               } __packed phy;
+       } __packed;
+} __packed __aligned(4);

This makes no sense at all. I would suggest marking only
the individual fields that are misaligned as __packed, but
not the structure itself.

and then there is this

+       union {
+               struct {
+                       u8 admin:1;
+                       u8 fc;
+                       u8 ap_enable;
+                       union {
+                               struct {
+                                       __le32 mode;
+                                       u8  inband:1;
+                                       __le32 speed;
+                                       u8  duplex;
+                                       u8  fec;
+                                       u8  fec_supp;
+                               } __packed reg_mode;
+                               struct {
+                                       __le32 mode;
+                                       __le32 speed;
+                                       u8  fec;
+                                       u8  fec_supp;
+                               } __packed ap_modes[PRESTERA_AP_PORT_MAX];
+                       } __packed;
+               } __packed mac;
+               struct {
+                       u8 admin:1;
+                       u8 adv_enable;
+                       __le64 modes;
+                       __le32 mode;
+                       u8 mdix;
+               } __packed phy;
+       } __packed link;

which puts misaligned bit fields in the middle of a packed structure!

       Arnd

Re: [PATCH] [-next] net: marvell: prestera: Add explicit padding

[Volodymyr Mytnyk [C]]

Hi All,

For some unknown reason, the bb5dbf2cc64d5cfa ("net: marvell: prestera: add firmware v4.0 support") changes have been merged into net-next w/o review comments addressed and waiting for the final patch set to be uploaded. Any idea why ?

Right now, I'm working on fixing all the issues/comments and rebasing them based on latest net-next master. Also, my changes include those posted in this thread to fix m68k build and comments related to structure pack/align.

Should I rebase my changes based on yours now ? Is it possible to make a relation chain ?

The bb5dbf2cc64d5cfa mail thread discussion (waiting for new v5 patchset to be uploaded) can be found at:

    [PATCH net-next v4] net: marvell: prestera: add firmware v4.0 support
    https://www.spinics.net/lists/kernel/msg4127689.html

Regards,
  Volodymyr

> On Tue, Nov 2, 2021 at 9:24 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >
> > On m68k:
> >
> >     In function ‘prestera_hw_build_tests’,
> >         inlined from ‘prestera_hw_switch_init’ at drivers/net/ethernet/marvell/prestera/prestera_hw.c:788:2:
> >     ././include/linux/compiler_types.h:335:38: error: call to ‘__compiletime_assert_345’ declared with attribute error: BUILD_BUG_ON failed: sizeof(struct prestera_msg_switch_attr_req) != 16
> >     ...
> >
> > The driver assumes structure members are naturally aligned, but does not
> > add explicit padding, thus breaking architectures where integral values
> > are not always naturally aligned (e.g. on m68k, __alignof(int) is 2, not
> > 4).
> >
> > Fixes: bb5dbf2cc64d5cfa ("net: marvell: prestera: add firmware v4.0 support")
> > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> 
> Looks good to me,
> 
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> 
> > Compile-tested only.
> >
> > BTW, I sincerely doubt the use of __packed on structs like:
> >
> >     union prestera_msg_switch_param {
> >             u8 mac[ETH_ALEN];
> >             __le32 ageing_timeout_ms;
> >     } __packed;
> >
> > This struct is only used as a member in another struct, where it is
> > be naturally aligned anyway.
> 
> Agreed, this __packed attribute is clearly bogus and should be removed.
> 
> Same for
> 
> +struct prestera_msg_event_port_param {
> +       union {
> +               struct {
> +                       u8 oper;
> +                       __le32 mode;
> +                       __le32 speed;
> +                       u8 duplex;
> +                       u8 fc;
> +                       u8 fec;
> +               } __packed mac;
> +               struct {
> +                       u8 mdix;
> +                       __le64 lmode_bmap;
> +                       u8 fc;
> +               } __packed phy;
> +       } __packed;
> +} __packed __aligned(4);
> 
> This makes no sense at all. I would suggest marking only
> the individual fields that are misaligned as __packed, but
> not the structure itself.
> 
> and then there is this
> 
> +       union {
> +               struct {
> +                       u8 admin:1;
> +                       u8 fc;
> +                       u8 ap_enable;
> +                       union {
> +                               struct {
> +                                       __le32 mode;
> +                                       u8  inband:1;
> +                                       __le32 speed;
> +                                       u8  duplex;
> +                                       u8  fec;
> +                                       u8  fec_supp;
> +                               } __packed reg_mode;
> +                               struct {
> +                                       __le32 mode;
> +                                       __le32 speed;
> +                                       u8  fec;
> +                                       u8  fec_supp;
> +                               } __packed ap_modes[PRESTERA_AP_PORT_MAX];
> +                       } __packed;
> +               } __packed mac;
> +               struct {
> +                       u8 admin:1;
> +                       u8 adv_enable;
> +                       __le64 modes;
> +                       __le32 mode;
> +                       u8 mdix;
> +               } __packed phy;
> +       } __packed link;
> 
> which puts misaligned bit fields in the middle of a packed structure!
>
>       Arnd

Re: [PATCH] [-next] net: marvell: prestera: Add explicit padding

[Jakub Kicinski]

On Tue, 2 Nov 2021 11:36:19 +0000 Volodymyr Mytnyk [C] wrote:
> Should I rebase my changes based on yours now ? Is it possible to make a relation chain ?

Please rebase your changes on top of net/master.

Re: [PATCH] [-next] net: marvell: prestera: Add explicit padding

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Tue,  2 Nov 2021 09:24:33 +0100 you wrote:
> On m68k:
> 
>     In function ‘prestera_hw_build_tests’,
> 	inlined from ‘prestera_hw_switch_init’ at drivers/net/ethernet/marvell/prestera/prestera_hw.c:788:2:
>     ././include/linux/compiler_types.h:335:38: error: call to ‘__compiletime_assert_345’ declared with attribute error: BUILD_BUG_ON failed: sizeof(struct prestera_msg_switch_attr_req) != 16
>     ...
> 
> [...]

Here is the summary with links:
  - [-next] net: marvell: prestera: Add explicit padding
    https://git.kernel.org/netdev/net/c/236f57fe1b88

You are awesome, thank you!
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