* [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings
@ 2019-07-26 20:57 Qian Cai
2019-07-26 21:30 ` Marcelo Ricardo Leitner
2019-07-29 10:39 ` David Laight
0 siblings, 2 replies; 6+ messages in thread
From: Qian Cai @ 2019-07-26 20:57 UTC (permalink / raw)
To: vyasevich, nhorman, marcelo.leitner; +Cc: linux-sctp, linux-kernel, Qian Cai
There are a lot of those warnings with GCC8+ 64bit,
In file included from ./include/linux/sctp.h:42,
from net/core/skbuff.c:47:
./include/uapi/linux/sctp.h:395:1: warning: alignment 4 of 'struct
sctp_paddr_change' is less than 8 [-Wpacked-not-aligned]
} __attribute__((packed, aligned(4)));
^
./include/uapi/linux/sctp.h:728:1: warning: alignment 4 of 'struct
sctp_setpeerprim' is less than 8 [-Wpacked-not-aligned]
} __attribute__((packed, aligned(4)));
^
./include/uapi/linux/sctp.h:727:26: warning: 'sspp_addr' offset 4 in
'struct sctp_setpeerprim' isn't aligned to 8 [-Wpacked-not-aligned]
struct sockaddr_storage sspp_addr;
^~~~~~~~~
./include/uapi/linux/sctp.h:741:1: warning: alignment 4 of 'struct
sctp_prim' is less than 8 [-Wpacked-not-aligned]
} __attribute__((packed, aligned(4)));
^
./include/uapi/linux/sctp.h:740:26: warning: 'ssp_addr' offset 4 in
'struct sctp_prim' isn't aligned to 8 [-Wpacked-not-aligned]
struct sockaddr_storage ssp_addr;
^~~~~~~~
./include/uapi/linux/sctp.h:792:1: warning: alignment 4 of 'struct
sctp_paddrparams' is less than 8 [-Wpacked-not-aligned]
} __attribute__((packed, aligned(4)));
^
./include/uapi/linux/sctp.h:784:26: warning: 'spp_address' offset 4 in
'struct sctp_paddrparams' isn't aligned to 8 [-Wpacked-not-aligned]
struct sockaddr_storage spp_address;
^~~~~~~~~~~
./include/uapi/linux/sctp.h:905:1: warning: alignment 4 of 'struct
sctp_paddrinfo' is less than 8 [-Wpacked-not-aligned]
} __attribute__((packed, aligned(4)));
^
./include/uapi/linux/sctp.h:899:26: warning: 'spinfo_address' offset 4
in 'struct sctp_paddrinfo' isn't aligned to 8 [-Wpacked-not-aligned]
struct sockaddr_storage spinfo_address;
^~~~~~~~~~~~~~
Fix them by aligning the structures and fields to 8 bytes instead.
Signed-off-by: Qian Cai <cai@lca.pw>
---
include/uapi/linux/sctp.h | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index b8f2c4d56532..e7bd71cde882 100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h
@@ -392,7 +392,7 @@ struct sctp_paddr_change {
int spc_state;
int spc_error;
sctp_assoc_t spc_assoc_id;
-} __attribute__((packed, aligned(4)));
+} __attribute__((packed, aligned(8)));
/*
* spc_state: 32 bits (signed integer)
@@ -724,8 +724,8 @@ struct sctp_assocparams {
*/
struct sctp_setpeerprim {
sctp_assoc_t sspp_assoc_id;
- struct sockaddr_storage sspp_addr;
-} __attribute__((packed, aligned(4)));
+ struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
+} __attribute__((packed, aligned(8)));
/*
* 7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR)
@@ -737,8 +737,8 @@ struct sctp_setpeerprim {
*/
struct sctp_prim {
sctp_assoc_t ssp_assoc_id;
- struct sockaddr_storage ssp_addr;
-} __attribute__((packed, aligned(4)));
+ struct sockaddr_storage ssp_addr __attribute__((aligned(8)));
+} __attribute__((packed, aligned(8)));
/* For backward compatibility use, define the old name too */
#define sctp_setprim sctp_prim
@@ -781,7 +781,7 @@ enum sctp_spp_flags {
struct sctp_paddrparams {
sctp_assoc_t spp_assoc_id;
- struct sockaddr_storage spp_address;
+ struct sockaddr_storage spp_address __attribute__((aligned(8)));
__u32 spp_hbinterval;
__u16 spp_pathmaxrxt;
__u32 spp_pathmtu;
@@ -789,7 +789,7 @@ struct sctp_paddrparams {
__u32 spp_flags;
__u32 spp_ipv6_flowlabel;
__u8 spp_dscp;
-} __attribute__((packed, aligned(4)));
+} __attribute__((packed, aligned(8)));
/*
* 7.1.18. Add a chunk that must be authenticated (SCTP_AUTH_CHUNK)
@@ -896,13 +896,13 @@ struct sctp_stream_value {
*/
struct sctp_paddrinfo {
sctp_assoc_t spinfo_assoc_id;
- struct sockaddr_storage spinfo_address;
+ struct sockaddr_storage spinfo_address __attribute__((aligned(8)));
__s32 spinfo_state;
__u32 spinfo_cwnd;
__u32 spinfo_srtt;
__u32 spinfo_rto;
__u32 spinfo_mtu;
-} __attribute__((packed, aligned(4)));
+} __attribute__((packed, aligned(8)));
/* Peer addresses's state. */
/* UNKNOWN: Peer address passed by the upper layer in sendmsg or connect[x]
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings
2019-07-26 20:57 [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings Qian Cai
@ 2019-07-26 21:30 ` Marcelo Ricardo Leitner
2019-07-28 17:05 ` Qian Cai
2019-07-29 10:39 ` David Laight
1 sibling, 1 reply; 6+ messages in thread
From: Marcelo Ricardo Leitner @ 2019-07-26 21:30 UTC (permalink / raw)
To: Qian Cai; +Cc: vyasevich, nhorman, linux-sctp, linux-kernel
On Fri, Jul 26, 2019 at 04:57:39PM -0400, Qian Cai wrote:
> There are a lot of those warnings with GCC8+ 64bit,
>
> In file included from ./include/linux/sctp.h:42,
> from net/core/skbuff.c:47:
> ./include/uapi/linux/sctp.h:395:1: warning: alignment 4 of 'struct
> sctp_paddr_change' is less than 8 [-Wpacked-not-aligned]
> } __attribute__((packed, aligned(4)));
> ^
> ./include/uapi/linux/sctp.h:728:1: warning: alignment 4 of 'struct
> sctp_setpeerprim' is less than 8 [-Wpacked-not-aligned]
> } __attribute__((packed, aligned(4)));
> ^
> ./include/uapi/linux/sctp.h:727:26: warning: 'sspp_addr' offset 4 in
> 'struct sctp_setpeerprim' isn't aligned to 8 [-Wpacked-not-aligned]
> struct sockaddr_storage sspp_addr;
> ^~~~~~~~~
> ./include/uapi/linux/sctp.h:741:1: warning: alignment 4 of 'struct
> sctp_prim' is less than 8 [-Wpacked-not-aligned]
> } __attribute__((packed, aligned(4)));
> ^
> ./include/uapi/linux/sctp.h:740:26: warning: 'ssp_addr' offset 4 in
> 'struct sctp_prim' isn't aligned to 8 [-Wpacked-not-aligned]
> struct sockaddr_storage ssp_addr;
> ^~~~~~~~
> ./include/uapi/linux/sctp.h:792:1: warning: alignment 4 of 'struct
> sctp_paddrparams' is less than 8 [-Wpacked-not-aligned]
> } __attribute__((packed, aligned(4)));
> ^
> ./include/uapi/linux/sctp.h:784:26: warning: 'spp_address' offset 4 in
> 'struct sctp_paddrparams' isn't aligned to 8 [-Wpacked-not-aligned]
> struct sockaddr_storage spp_address;
> ^~~~~~~~~~~
> ./include/uapi/linux/sctp.h:905:1: warning: alignment 4 of 'struct
> sctp_paddrinfo' is less than 8 [-Wpacked-not-aligned]
> } __attribute__((packed, aligned(4)));
> ^
> ./include/uapi/linux/sctp.h:899:26: warning: 'spinfo_address' offset 4
> in 'struct sctp_paddrinfo' isn't aligned to 8 [-Wpacked-not-aligned]
> struct sockaddr_storage spinfo_address;
> ^~~~~~~~~~~~~~
> Fix them by aligning the structures and fields to 8 bytes instead.
>
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> include/uapi/linux/sctp.h | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> index b8f2c4d56532..e7bd71cde882 100644
> --- a/include/uapi/linux/sctp.h
> +++ b/include/uapi/linux/sctp.h
These changes gotta be more careful, if possible at all. As is, it's breaking UAPI.
-before
+after patch
struct sctp_paddrparams {
sctp_assoc_t spp_assoc_id; /* 0 4 */
- struct __kernel_sockaddr_storage spp_address __attribute__((__aligned__(1))); /* 4 128 */
- /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
- __u32 spp_hbinterval; /* 132 4 */
- __u16 spp_pathmaxrxt; /* 136 2 */
- __u32 spp_pathmtu; /* 138 4 */
- __u32 spp_sackdelay; /* 142 4 */
- __u32 spp_flags; /* 146 4 */
- __u32 spp_ipv6_flowlabel; /* 150 4 */
- __u8 spp_dscp; /* 154 1 */
- /* size: 156, cachelines: 3, members: 9 */
+ /* XXX 4 bytes hole, try to pack */
+
+ struct __kernel_sockaddr_storage spp_address __attribute__((__aligned__(8))); /* 8 128 */
+ /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
+ __u32 spp_hbinterval; /* 136 4 */
+ __u16 spp_pathmaxrxt; /* 140 2 */
+ __u32 spp_pathmtu; /* 142 4 */
+ __u32 spp_sackdelay; /* 146 4 */
+ __u32 spp_flags; /* 150 4 */
+ __u32 spp_ipv6_flowlabel; /* 154 4 */
+ __u8 spp_dscp; /* 158 1 */
+
+ /* size: 160, cachelines: 3, members: 9 */
+ /* sum members: 155, holes: 1, sum holes: 4 */
/* padding: 1 */
- /* forced alignments: 1 */
- /* last cacheline: 28 bytes */
-} __attribute__((__aligned__(4)));
+ /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
+ /* last cacheline: 32 bytes */
+} __attribute__((__aligned__(8)));
> @@ -392,7 +392,7 @@ struct sctp_paddr_change {
> int spc_state;
> int spc_error;
> sctp_assoc_t spc_assoc_id;
> -} __attribute__((packed, aligned(4)));
> +} __attribute__((packed, aligned(8)));
>
> /*
> * spc_state: 32 bits (signed integer)
> @@ -724,8 +724,8 @@ struct sctp_assocparams {
> */
> struct sctp_setpeerprim {
> sctp_assoc_t sspp_assoc_id;
> - struct sockaddr_storage sspp_addr;
> -} __attribute__((packed, aligned(4)));
> + struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
> +} __attribute__((packed, aligned(8)));
>
> /*
> * 7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR)
> @@ -737,8 +737,8 @@ struct sctp_setpeerprim {
> */
> struct sctp_prim {
> sctp_assoc_t ssp_assoc_id;
> - struct sockaddr_storage ssp_addr;
> -} __attribute__((packed, aligned(4)));
> + struct sockaddr_storage ssp_addr __attribute__((aligned(8)));
> +} __attribute__((packed, aligned(8)));
>
> /* For backward compatibility use, define the old name too */
> #define sctp_setprim sctp_prim
> @@ -781,7 +781,7 @@ enum sctp_spp_flags {
>
> struct sctp_paddrparams {
> sctp_assoc_t spp_assoc_id;
> - struct sockaddr_storage spp_address;
> + struct sockaddr_storage spp_address __attribute__((aligned(8)));
> __u32 spp_hbinterval;
> __u16 spp_pathmaxrxt;
> __u32 spp_pathmtu;
> @@ -789,7 +789,7 @@ struct sctp_paddrparams {
> __u32 spp_flags;
> __u32 spp_ipv6_flowlabel;
> __u8 spp_dscp;
> -} __attribute__((packed, aligned(4)));
> +} __attribute__((packed, aligned(8)));
>
> /*
> * 7.1.18. Add a chunk that must be authenticated (SCTP_AUTH_CHUNK)
> @@ -896,13 +896,13 @@ struct sctp_stream_value {
> */
> struct sctp_paddrinfo {
> sctp_assoc_t spinfo_assoc_id;
> - struct sockaddr_storage spinfo_address;
> + struct sockaddr_storage spinfo_address __attribute__((aligned(8)));
> __s32 spinfo_state;
> __u32 spinfo_cwnd;
> __u32 spinfo_srtt;
> __u32 spinfo_rto;
> __u32 spinfo_mtu;
> -} __attribute__((packed, aligned(4)));
> +} __attribute__((packed, aligned(8)));
>
> /* Peer addresses's state. */
> /* UNKNOWN: Peer address passed by the upper layer in sendmsg or connect[x]
> --
> 1.8.3.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings
2019-07-26 21:30 ` Marcelo Ricardo Leitner
@ 2019-07-28 17:05 ` Qian Cai
2019-07-28 19:41 ` Marcelo Ricardo Leitner
0 siblings, 1 reply; 6+ messages in thread
From: Qian Cai @ 2019-07-28 17:05 UTC (permalink / raw)
To: Marcelo Ricardo Leitner; +Cc: vyasevich, nhorman, linux-sctp, linux-kernel
> On Jul 26, 2019, at 5:30 PM, Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> wrote:
>
> On Fri, Jul 26, 2019 at 04:57:39PM -0400, Qian Cai wrote:
>> There are a lot of those warnings with GCC8+ 64bit,
>>
>> In file included from ./include/linux/sctp.h:42,
>> from net/core/skbuff.c:47:
>> ./include/uapi/linux/sctp.h:395:1: warning: alignment 4 of 'struct
>> sctp_paddr_change' is less than 8 [-Wpacked-not-aligned]
>> } __attribute__((packed, aligned(4)));
>> ^
>> ./include/uapi/linux/sctp.h:728:1: warning: alignment 4 of 'struct
>> sctp_setpeerprim' is less than 8 [-Wpacked-not-aligned]
>> } __attribute__((packed, aligned(4)));
>> ^
>> ./include/uapi/linux/sctp.h:727:26: warning: 'sspp_addr' offset 4 in
>> 'struct sctp_setpeerprim' isn't aligned to 8 [-Wpacked-not-aligned]
>> struct sockaddr_storage sspp_addr;
>> ^~~~~~~~~
>> ./include/uapi/linux/sctp.h:741:1: warning: alignment 4 of 'struct
>> sctp_prim' is less than 8 [-Wpacked-not-aligned]
>> } __attribute__((packed, aligned(4)));
>> ^
>> ./include/uapi/linux/sctp.h:740:26: warning: 'ssp_addr' offset 4 in
>> 'struct sctp_prim' isn't aligned to 8 [-Wpacked-not-aligned]
>> struct sockaddr_storage ssp_addr;
>> ^~~~~~~~
>> ./include/uapi/linux/sctp.h:792:1: warning: alignment 4 of 'struct
>> sctp_paddrparams' is less than 8 [-Wpacked-not-aligned]
>> } __attribute__((packed, aligned(4)));
>> ^
>> ./include/uapi/linux/sctp.h:784:26: warning: 'spp_address' offset 4 in
>> 'struct sctp_paddrparams' isn't aligned to 8 [-Wpacked-not-aligned]
>> struct sockaddr_storage spp_address;
>> ^~~~~~~~~~~
>> ./include/uapi/linux/sctp.h:905:1: warning: alignment 4 of 'struct
>> sctp_paddrinfo' is less than 8 [-Wpacked-not-aligned]
>> } __attribute__((packed, aligned(4)));
>> ^
>> ./include/uapi/linux/sctp.h:899:26: warning: 'spinfo_address' offset 4
>> in 'struct sctp_paddrinfo' isn't aligned to 8 [-Wpacked-not-aligned]
>> struct sockaddr_storage spinfo_address;
>> ^~~~~~~~~~~~~~
>> Fix them by aligning the structures and fields to 8 bytes instead.
>>
>> Signed-off-by: Qian Cai <cai@lca.pw>
>> ---
>> include/uapi/linux/sctp.h | 18 +++++++++---------
>> 1 file changed, 9 insertions(+), 9 deletions(-)
>>
>> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
>> index b8f2c4d56532..e7bd71cde882 100644
>> --- a/include/uapi/linux/sctp.h
>> +++ b/include/uapi/linux/sctp.h
>
> These changes gotta be more careful, if possible at all. As is, it's breaking UAPI.
Could you please elaborate how this breaks userspace? I read through all the information
I can find about UAPI and still have no clue. All I can see if that some field alignments changed
which are expected, and it still take on 3 cachelines which should not hurt the performance.
>
> -before
> +after patch
>
> struct sctp_paddrparams {
> sctp_assoc_t spp_assoc_id; /* 0 4 */
> - struct __kernel_sockaddr_storage spp_address __attribute__((__aligned__(1))); /* 4 128 */
> - /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
> - __u32 spp_hbinterval; /* 132 4 */
> - __u16 spp_pathmaxrxt; /* 136 2 */
> - __u32 spp_pathmtu; /* 138 4 */
> - __u32 spp_sackdelay; /* 142 4 */
> - __u32 spp_flags; /* 146 4 */
> - __u32 spp_ipv6_flowlabel; /* 150 4 */
> - __u8 spp_dscp; /* 154 1 */
>
> - /* size: 156, cachelines: 3, members: 9 */
> + /* XXX 4 bytes hole, try to pack */
> +
> + struct __kernel_sockaddr_storage spp_address __attribute__((__aligned__(8))); /* 8 128 */
> + /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
> + __u32 spp_hbinterval; /* 136 4 */
> + __u16 spp_pathmaxrxt; /* 140 2 */
> + __u32 spp_pathmtu; /* 142 4 */
> + __u32 spp_sackdelay; /* 146 4 */
> + __u32 spp_flags; /* 150 4 */
> + __u32 spp_ipv6_flowlabel; /* 154 4 */
> + __u8 spp_dscp; /* 158 1 */
> +
> + /* size: 160, cachelines: 3, members: 9 */
> + /* sum members: 155, holes: 1, sum holes: 4 */
> /* padding: 1 */
> - /* forced alignments: 1 */
> - /* last cacheline: 28 bytes */
> -} __attribute__((__aligned__(4)));
> + /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
> + /* last cacheline: 32 bytes */
> +} __attribute__((__aligned__(8)));
>
>
>> @@ -392,7 +392,7 @@ struct sctp_paddr_change {
>> int spc_state;
>> int spc_error;
>> sctp_assoc_t spc_assoc_id;
>> -} __attribute__((packed, aligned(4)));
>> +} __attribute__((packed, aligned(8)));
>>
>> /*
>> * spc_state: 32 bits (signed integer)
>> @@ -724,8 +724,8 @@ struct sctp_assocparams {
>> */
>> struct sctp_setpeerprim {
>> sctp_assoc_t sspp_assoc_id;
>> - struct sockaddr_storage sspp_addr;
>> -} __attribute__((packed, aligned(4)));
>> + struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
>> +} __attribute__((packed, aligned(8)));
>>
>> /*
>> * 7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR)
>> @@ -737,8 +737,8 @@ struct sctp_setpeerprim {
>> */
>> struct sctp_prim {
>> sctp_assoc_t ssp_assoc_id;
>> - struct sockaddr_storage ssp_addr;
>> -} __attribute__((packed, aligned(4)));
>> + struct sockaddr_storage ssp_addr __attribute__((aligned(8)));
>> +} __attribute__((packed, aligned(8)));
>>
>> /* For backward compatibility use, define the old name too */
>> #define sctp_setprim sctp_prim
>> @@ -781,7 +781,7 @@ enum sctp_spp_flags {
>>
>> struct sctp_paddrparams {
>> sctp_assoc_t spp_assoc_id;
>> - struct sockaddr_storage spp_address;
>> + struct sockaddr_storage spp_address __attribute__((aligned(8)));
>> __u32 spp_hbinterval;
>> __u16 spp_pathmaxrxt;
>> __u32 spp_pathmtu;
>> @@ -789,7 +789,7 @@ struct sctp_paddrparams {
>> __u32 spp_flags;
>> __u32 spp_ipv6_flowlabel;
>> __u8 spp_dscp;
>> -} __attribute__((packed, aligned(4)));
>> +} __attribute__((packed, aligned(8)));
>>
>> /*
>> * 7.1.18. Add a chunk that must be authenticated (SCTP_AUTH_CHUNK)
>> @@ -896,13 +896,13 @@ struct sctp_stream_value {
>> */
>> struct sctp_paddrinfo {
>> sctp_assoc_t spinfo_assoc_id;
>> - struct sockaddr_storage spinfo_address;
>> + struct sockaddr_storage spinfo_address __attribute__((aligned(8)));
>> __s32 spinfo_state;
>> __u32 spinfo_cwnd;
>> __u32 spinfo_srtt;
>> __u32 spinfo_rto;
>> __u32 spinfo_mtu;
>> -} __attribute__((packed, aligned(4)));
>> +} __attribute__((packed, aligned(8)));
>>
>> /* Peer addresses's state. */
>> /* UNKNOWN: Peer address passed by the upper layer in sendmsg or connect[x]
>> --
>> 1.8.3.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings
2019-07-28 17:05 ` Qian Cai
@ 2019-07-28 19:41 ` Marcelo Ricardo Leitner
0 siblings, 0 replies; 6+ messages in thread
From: Marcelo Ricardo Leitner @ 2019-07-28 19:41 UTC (permalink / raw)
To: Qian Cai; +Cc: vyasevich, nhorman, linux-sctp, linux-kernel
On Sun, Jul 28, 2019 at 01:05:25PM -0400, Qian Cai wrote:
>
>
> > On Jul 26, 2019, at 5:30 PM, Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> wrote:
> >
> > On Fri, Jul 26, 2019 at 04:57:39PM -0400, Qian Cai wrote:
> >> There are a lot of those warnings with GCC8+ 64bit,
> >>
> >> In file included from ./include/linux/sctp.h:42,
> >> from net/core/skbuff.c:47:
> >> ./include/uapi/linux/sctp.h:395:1: warning: alignment 4 of 'struct
> >> sctp_paddr_change' is less than 8 [-Wpacked-not-aligned]
> >> } __attribute__((packed, aligned(4)));
> >> ^
> >> ./include/uapi/linux/sctp.h:728:1: warning: alignment 4 of 'struct
> >> sctp_setpeerprim' is less than 8 [-Wpacked-not-aligned]
> >> } __attribute__((packed, aligned(4)));
> >> ^
> >> ./include/uapi/linux/sctp.h:727:26: warning: 'sspp_addr' offset 4 in
> >> 'struct sctp_setpeerprim' isn't aligned to 8 [-Wpacked-not-aligned]
> >> struct sockaddr_storage sspp_addr;
> >> ^~~~~~~~~
> >> ./include/uapi/linux/sctp.h:741:1: warning: alignment 4 of 'struct
> >> sctp_prim' is less than 8 [-Wpacked-not-aligned]
> >> } __attribute__((packed, aligned(4)));
> >> ^
> >> ./include/uapi/linux/sctp.h:740:26: warning: 'ssp_addr' offset 4 in
> >> 'struct sctp_prim' isn't aligned to 8 [-Wpacked-not-aligned]
> >> struct sockaddr_storage ssp_addr;
> >> ^~~~~~~~
> >> ./include/uapi/linux/sctp.h:792:1: warning: alignment 4 of 'struct
> >> sctp_paddrparams' is less than 8 [-Wpacked-not-aligned]
> >> } __attribute__((packed, aligned(4)));
> >> ^
> >> ./include/uapi/linux/sctp.h:784:26: warning: 'spp_address' offset 4 in
> >> 'struct sctp_paddrparams' isn't aligned to 8 [-Wpacked-not-aligned]
> >> struct sockaddr_storage spp_address;
> >> ^~~~~~~~~~~
> >> ./include/uapi/linux/sctp.h:905:1: warning: alignment 4 of 'struct
> >> sctp_paddrinfo' is less than 8 [-Wpacked-not-aligned]
> >> } __attribute__((packed, aligned(4)));
> >> ^
> >> ./include/uapi/linux/sctp.h:899:26: warning: 'spinfo_address' offset 4
> >> in 'struct sctp_paddrinfo' isn't aligned to 8 [-Wpacked-not-aligned]
> >> struct sockaddr_storage spinfo_address;
> >> ^~~~~~~~~~~~~~
> >> Fix them by aligning the structures and fields to 8 bytes instead.
> >>
> >> Signed-off-by: Qian Cai <cai@lca.pw>
> >> ---
> >> include/uapi/linux/sctp.h | 18 +++++++++---------
> >> 1 file changed, 9 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> >> index b8f2c4d56532..e7bd71cde882 100644
> >> --- a/include/uapi/linux/sctp.h
> >> +++ b/include/uapi/linux/sctp.h
> >
> > These changes gotta be more careful, if possible at all. As is, it's breaking UAPI.
>
> Could you please elaborate how this breaks userspace? I read through all the information
> I can find about UAPI and still have no clue. All I can see if that some field alignments changed
> which are expected, and it still take on 3 cachelines which should not hurt the performance.
For example on the struct I pointed below, if an application is
compiled using the old headers, sctp_paddrparams->spp_hbinterval is at
offset 132. But with this patch, it will change to 136. Then with a
kernel with this patch, it will look for the field at the wrong place.
>
> >
> > -before
> > +after patch
> >
> > struct sctp_paddrparams {
> > sctp_assoc_t spp_assoc_id; /* 0 4 */
> > - struct __kernel_sockaddr_storage spp_address __attribute__((__aligned__(1))); /* 4 128 */
> > - /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
> > - __u32 spp_hbinterval; /* 132 4 */
> > - __u16 spp_pathmaxrxt; /* 136 2 */
> > - __u32 spp_pathmtu; /* 138 4 */
> > - __u32 spp_sackdelay; /* 142 4 */
> > - __u32 spp_flags; /* 146 4 */
> > - __u32 spp_ipv6_flowlabel; /* 150 4 */
> > - __u8 spp_dscp; /* 154 1 */
> >
> > - /* size: 156, cachelines: 3, members: 9 */
> > + /* XXX 4 bytes hole, try to pack */
> > +
> > + struct __kernel_sockaddr_storage spp_address __attribute__((__aligned__(8))); /* 8 128 */
> > + /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
> > + __u32 spp_hbinterval; /* 136 4 */
> > + __u16 spp_pathmaxrxt; /* 140 2 */
> > + __u32 spp_pathmtu; /* 142 4 */
> > + __u32 spp_sackdelay; /* 146 4 */
> > + __u32 spp_flags; /* 150 4 */
> > + __u32 spp_ipv6_flowlabel; /* 154 4 */
> > + __u8 spp_dscp; /* 158 1 */
> > +
> > + /* size: 160, cachelines: 3, members: 9 */
> > + /* sum members: 155, holes: 1, sum holes: 4 */
> > /* padding: 1 */
> > - /* forced alignments: 1 */
> > - /* last cacheline: 28 bytes */
> > -} __attribute__((__aligned__(4)));
> > + /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
> > + /* last cacheline: 32 bytes */
> > +} __attribute__((__aligned__(8)));
> >
> >
> >> @@ -392,7 +392,7 @@ struct sctp_paddr_change {
> >> int spc_state;
> >> int spc_error;
> >> sctp_assoc_t spc_assoc_id;
> >> -} __attribute__((packed, aligned(4)));
> >> +} __attribute__((packed, aligned(8)));
> >>
> >> /*
> >> * spc_state: 32 bits (signed integer)
> >> @@ -724,8 +724,8 @@ struct sctp_assocparams {
> >> */
> >> struct sctp_setpeerprim {
> >> sctp_assoc_t sspp_assoc_id;
> >> - struct sockaddr_storage sspp_addr;
> >> -} __attribute__((packed, aligned(4)));
> >> + struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
> >> +} __attribute__((packed, aligned(8)));
> >>
> >> /*
> >> * 7.1.10 Set Primary Address (SCTP_PRIMARY_ADDR)
> >> @@ -737,8 +737,8 @@ struct sctp_setpeerprim {
> >> */
> >> struct sctp_prim {
> >> sctp_assoc_t ssp_assoc_id;
> >> - struct sockaddr_storage ssp_addr;
> >> -} __attribute__((packed, aligned(4)));
> >> + struct sockaddr_storage ssp_addr __attribute__((aligned(8)));
> >> +} __attribute__((packed, aligned(8)));
> >>
> >> /* For backward compatibility use, define the old name too */
> >> #define sctp_setprim sctp_prim
> >> @@ -781,7 +781,7 @@ enum sctp_spp_flags {
> >>
> >> struct sctp_paddrparams {
> >> sctp_assoc_t spp_assoc_id;
> >> - struct sockaddr_storage spp_address;
> >> + struct sockaddr_storage spp_address __attribute__((aligned(8)));
> >> __u32 spp_hbinterval;
> >> __u16 spp_pathmaxrxt;
> >> __u32 spp_pathmtu;
> >> @@ -789,7 +789,7 @@ struct sctp_paddrparams {
> >> __u32 spp_flags;
> >> __u32 spp_ipv6_flowlabel;
> >> __u8 spp_dscp;
> >> -} __attribute__((packed, aligned(4)));
> >> +} __attribute__((packed, aligned(8)));
> >>
> >> /*
> >> * 7.1.18. Add a chunk that must be authenticated (SCTP_AUTH_CHUNK)
> >> @@ -896,13 +896,13 @@ struct sctp_stream_value {
> >> */
> >> struct sctp_paddrinfo {
> >> sctp_assoc_t spinfo_assoc_id;
> >> - struct sockaddr_storage spinfo_address;
> >> + struct sockaddr_storage spinfo_address __attribute__((aligned(8)));
> >> __s32 spinfo_state;
> >> __u32 spinfo_cwnd;
> >> __u32 spinfo_srtt;
> >> __u32 spinfo_rto;
> >> __u32 spinfo_mtu;
> >> -} __attribute__((packed, aligned(4)));
> >> +} __attribute__((packed, aligned(8)));
> >>
> >> /* Peer addresses's state. */
> >> /* UNKNOWN: Peer address passed by the upper layer in sendmsg or connect[x]
> >> --
> >> 1.8.3.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings
2019-07-26 20:57 [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings Qian Cai
2019-07-26 21:30 ` Marcelo Ricardo Leitner
@ 2019-07-29 10:39 ` David Laight
2019-07-29 15:16 ` Qian Cai
1 sibling, 1 reply; 6+ messages in thread
From: David Laight @ 2019-07-29 10:39 UTC (permalink / raw)
To: 'Qian Cai', vyasevich, nhorman, marcelo.leitner
Cc: linux-sctp, linux-kernel
From: Qian Cai
> Sent: 26 July 2019 21:58
>
> There are a lot of those warnings with GCC8+ 64bit,
>
...
> Fix them by aligning the structures and fields to 8 bytes instead.
...
> struct sctp_setpeerprim {
> sctp_assoc_t sspp_assoc_id;
> - struct sockaddr_storage sspp_addr;
> -} __attribute__((packed, aligned(4)));
> + struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
> +} __attribute__((packed, aligned(8)));
What happens to this one if you change both to aligned(4) ?
Much the same way as:
struct {
int a;
long b __attribute__((aligned(4));
};
is only 12 bytes on (most) 64bit systems.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings
2019-07-29 10:39 ` David Laight
@ 2019-07-29 15:16 ` Qian Cai
0 siblings, 0 replies; 6+ messages in thread
From: Qian Cai @ 2019-07-29 15:16 UTC (permalink / raw)
To: David Laight, vyasevich, nhorman, marcelo.leitner
Cc: linux-sctp, linux-kernel
On Mon, 2019-07-29 at 10:39 +0000, David Laight wrote:
> From: Qian Cai
> > Sent: 26 July 2019 21:58
> >
> > There are a lot of those warnings with GCC8+ 64bit,
> >
>
> ...
> > Fix them by aligning the structures and fields to 8 bytes instead.
>
> ...
> > struct sctp_setpeerprim {
> > sctp_assoc_t sspp_assoc_id;
> > - struct sockaddr_storage sspp_addr;
> > -} __attribute__((packed, aligned(4)));
> > + struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
> > +} __attribute__((packed, aligned(8)));
>
> What happens to this one if you change both to aligned(4) ?
> Much the same way as:
> struct {
> int a;
> long b __attribute__((aligned(4));
> };
> is only 12 bytes on (most) 64bit systems.
No, that won't work. It because that,
#define sockaddr_storage __kernel_sockaddr_storage
struct __kernel_sockaddr_storage {
...
} __attribute__ ((aligned(_K_SS_ALIGNSIZE)))
#define _K_SS_ALIGNSIZE (__alignof__ (struct sockaddr *))
A pointer is 8-byte on 64-bit systems. If changed "struct
__kernel_sockaddr_storage" to use,
__attribute__ ((aligned((4)))
it then silence the warnings.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-07-29 15:16 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-26 20:57 [PATCH] net/sctp: fix GCC8+ -Wpacked-not-aligned warnings Qian Cai
2019-07-26 21:30 ` Marcelo Ricardo Leitner
2019-07-28 17:05 ` Qian Cai
2019-07-28 19:41 ` Marcelo Ricardo Leitner
2019-07-29 10:39 ` David Laight
2019-07-29 15:16 ` Qian Cai
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