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* [PATCH v2] net/socket: fix GCC8+ Wpacked-not-aligned warnings
@ 2019-07-30 14:38 ` Qian Cai
  0 siblings, 0 replies; 5+ messages in thread
From: Qian Cai @ 2019-07-30 14:38 UTC (permalink / raw)
  To: davem
  Cc: vyasevich, nhorman, marcelo.leitner, David.Laight, linux-sctp,
	netdev, linux-kernel, Qian Cai

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;
                          ^~~~~~~~~~~~~~

This is because the commit 20c9c825b12f ("[SCTP] Fix SCTP socket options
to work with 32-bit apps on 64-bit kernels.") added "packed, aligned(4)"
GCC attributes to some structures but one of the members, i.e, "struct
sockaddr_storage" in those structures has the attribute,
"aligned(__alignof__ (struct sockaddr *)" which is 8-byte on 64-bit
systems, so the commit overwrites the designed alignments for
"sockaddr_storage".

To fix this, "struct sockaddr_storage" needs to be aligned to 4-byte as
it is only used in those packed sctp structure which is part of UAPI,
and "struct __kernel_sockaddr_storage" is used in some other
places of UAPI that need not to change alignments in order to not
breaking userspace.

Use an implicit alignment for "struct __kernel_sockaddr_storage" so it
can keep the same alignments as a member in both packed and un-packed
structures without breaking UAPI.

Suggested-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Qian Cai <cai@lca.pw>
---

v2: Use an implicit alignment for "struct __kernel_sockaddr_storage".

 include/uapi/linux/socket.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index 8eb96021709c..caf6c4d5f6ad 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h
@@ -6,17 +6,20 @@
  * Desired design of maximum size and alignment (see RFC2553)
  */
 #define _K_SS_MAXSIZE	128	/* Implementation specific max size */
-#define _K_SS_ALIGNSIZE	(__alignof__ (struct sockaddr *))
-				/* Implementation specific desired alignment */
 
 typedef unsigned short __kernel_sa_family_t;
 
 struct __kernel_sockaddr_storage {
-	__kernel_sa_family_t	ss_family;		/* address family */
-	/* Following field(s) are implementation specific */
-	char		__data[_K_SS_MAXSIZE - sizeof(unsigned short)];
+	union {
+		void *__align; /* implementation specific desired alignment */
+		struct {
+			__kernel_sa_family_t	ss_family; /* address family */
+			/* Following field(s) are implementation specific */
+			char __data[_K_SS_MAXSIZE - sizeof(unsigned short)];
 				/* space to achieve desired size, */
 				/* _SS_MAXSIZE value minus size of ss_family */
-} __attribute__ ((aligned(_K_SS_ALIGNSIZE)));	/* force desired alignment */
+			};
+		};
+};
 
 #endif /* _UAPI_LINUX_SOCKET_H */
-- 
1.8.3.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH v2] net/socket: fix GCC8+ Wpacked-not-aligned warnings
@ 2019-07-30 14:38 ` Qian Cai
  0 siblings, 0 replies; 5+ messages in thread
From: Qian Cai @ 2019-07-30 14:38 UTC (permalink / raw)
  To: davem
  Cc: vyasevich, nhorman, marcelo.leitner, David.Laight, linux-sctp,
	netdev, linux-kernel, Qian Cai

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;
                          ^~~~~~~~~~~~~~

This is because the commit 20c9c825b12f ("[SCTP] Fix SCTP socket options
to work with 32-bit apps on 64-bit kernels.") added "packed, aligned(4)"
GCC attributes to some structures but one of the members, i.e, "struct
sockaddr_storage" in those structures has the attribute,
"aligned(__alignof__ (struct sockaddr *)" which is 8-byte on 64-bit
systems, so the commit overwrites the designed alignments for
"sockaddr_storage".

To fix this, "struct sockaddr_storage" needs to be aligned to 4-byte as
it is only used in those packed sctp structure which is part of UAPI,
and "struct __kernel_sockaddr_storage" is used in some other
places of UAPI that need not to change alignments in order to not
breaking userspace.

Use an implicit alignment for "struct __kernel_sockaddr_storage" so it
can keep the same alignments as a member in both packed and un-packed
structures without breaking UAPI.

Suggested-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Qian Cai <cai@lca.pw>
---

v2: Use an implicit alignment for "struct __kernel_sockaddr_storage".

 include/uapi/linux/socket.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index 8eb96021709c..caf6c4d5f6ad 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h
@@ -6,17 +6,20 @@
  * Desired design of maximum size and alignment (see RFC2553)
  */
 #define _K_SS_MAXSIZE	128	/* Implementation specific max size */
-#define _K_SS_ALIGNSIZE	(__alignof__ (struct sockaddr *))
-				/* Implementation specific desired alignment */
 
 typedef unsigned short __kernel_sa_family_t;
 
 struct __kernel_sockaddr_storage {
-	__kernel_sa_family_t	ss_family;		/* address family */
-	/* Following field(s) are implementation specific */
-	char		__data[_K_SS_MAXSIZE - sizeof(unsigned short)];
+	union {
+		void *__align; /* implementation specific desired alignment */
+		struct {
+			__kernel_sa_family_t	ss_family; /* address family */
+			/* Following field(s) are implementation specific */
+			char __data[_K_SS_MAXSIZE - sizeof(unsigned short)];
 				/* space to achieve desired size, */
 				/* _SS_MAXSIZE value minus size of ss_family */
-} __attribute__ ((aligned(_K_SS_ALIGNSIZE)));	/* force desired alignment */
+			};
+		};
+};
 
 #endif /* _UAPI_LINUX_SOCKET_H */
-- 
1.8.3.1

^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH v2] net/socket: fix GCC8+ Wpacked-not-aligned warnings
  2019-07-30 14:38 ` Qian Cai
@ 2019-07-30 14:45   ` Marcelo Ricardo Leitner
  -1 siblings, 0 replies; 5+ messages in thread
From: Marcelo Ricardo Leitner @ 2019-07-30 14:45 UTC (permalink / raw)
  To: Qian Cai
  Cc: davem, vyasevich, nhorman, David.Laight, linux-sctp, netdev,
	linux-kernel

On Tue, Jul 30, 2019 at 10:38:08AM -0400, Qian Cai wrote:
> 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;
>                           ^~~~~~~~~~~~~~
> 
> This is because the commit 20c9c825b12f ("[SCTP] Fix SCTP socket options
> to work with 32-bit apps on 64-bit kernels.") added "packed, aligned(4)"
> GCC attributes to some structures but one of the members, i.e, "struct
> sockaddr_storage" in those structures has the attribute,
> "aligned(__alignof__ (struct sockaddr *)" which is 8-byte on 64-bit
> systems, so the commit overwrites the designed alignments for
> "sockaddr_storage".
> 
> To fix this, "struct sockaddr_storage" needs to be aligned to 4-byte as
> it is only used in those packed sctp structure which is part of UAPI,
> and "struct __kernel_sockaddr_storage" is used in some other
> places of UAPI that need not to change alignments in order to not
> breaking userspace.
> 
> Use an implicit alignment for "struct __kernel_sockaddr_storage" so it
> can keep the same alignments as a member in both packed and un-packed
> structures without breaking UAPI.
> 
> Suggested-by: David Laight <David.Laight@ACULAB.COM>
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> 
> v2: Use an implicit alignment for "struct __kernel_sockaddr_storage".
> 
>  include/uapi/linux/socket.h | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 

SCTP-wise, LGTM.

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH v2] net/socket: fix GCC8+ Wpacked-not-aligned warnings
@ 2019-07-30 14:45   ` Marcelo Ricardo Leitner
  0 siblings, 0 replies; 5+ messages in thread
From: Marcelo Ricardo Leitner @ 2019-07-30 14:45 UTC (permalink / raw)
  To: Qian Cai
  Cc: davem, vyasevich, nhorman, David.Laight, linux-sctp, netdev,
	linux-kernel

On Tue, Jul 30, 2019 at 10:38:08AM -0400, Qian Cai wrote:
> 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;
>                           ^~~~~~~~~~~~~~
> 
> This is because the commit 20c9c825b12f ("[SCTP] Fix SCTP socket options
> to work with 32-bit apps on 64-bit kernels.") added "packed, aligned(4)"
> GCC attributes to some structures but one of the members, i.e, "struct
> sockaddr_storage" in those structures has the attribute,
> "aligned(__alignof__ (struct sockaddr *)" which is 8-byte on 64-bit
> systems, so the commit overwrites the designed alignments for
> "sockaddr_storage".
> 
> To fix this, "struct sockaddr_storage" needs to be aligned to 4-byte as
> it is only used in those packed sctp structure which is part of UAPI,
> and "struct __kernel_sockaddr_storage" is used in some other
> places of UAPI that need not to change alignments in order to not
> breaking userspace.
> 
> Use an implicit alignment for "struct __kernel_sockaddr_storage" so it
> can keep the same alignments as a member in both packed and un-packed
> structures without breaking UAPI.
> 
> Suggested-by: David Laight <David.Laight@ACULAB.COM>
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> 
> v2: Use an implicit alignment for "struct __kernel_sockaddr_storage".
> 
>  include/uapi/linux/socket.h | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 

SCTP-wise, LGTM.

^ permalink raw reply	[flat|nested] 5+ messages in thread
* RE: [PATCH v2] net/socket: fix GCC8+ Wpacked-not-aligned warnings
  2019-07-30 14:38 ` Qian Cai
  (?)
  (?)
@ 2019-07-30 14:59 ` David Laight
  -1 siblings, 0 replies; 5+ messages in thread
From: David Laight @ 2019-07-30 14:59 UTC (permalink / raw)
  To: 'Qian Cai', davem
  Cc: vyasevich, nhorman, marcelo.leitner, linux-sctp, netdev, linux-kernel

From: Qian Cai
> Sent: 30 July 2019 15:38
...
> Use an implicit alignment for "struct __kernel_sockaddr_storage" so it
> can keep the same alignments as a member in both packed and un-packed
> structures without breaking UAPI.
> 
> Suggested-by: David Laight <David.Laight@ACULAB.COM>
...

Although I suggested it needs a bit of tidy up.

Add a comment maybe:

/* The definition uses anonymous union and struct in order to
 * control the default alignment. */

>  struct __kernel_sockaddr_storage {
> -	__kernel_sa_family_t	ss_family;		/* address family */
> -	/* Following field(s) are implementation specific */
> -	char		__data[_K_SS_MAXSIZE - sizeof(unsigned short)];
> +	union {
> +		void *__align; /* implementation specific desired alignment */

Move the 'void *' below the struct so the first member is the 'public one.

> +		struct {
> +			__kernel_sa_family_t	ss_family; /* address family */
> +			/* Following field(s) are implementation specific */
> +			char __data[_K_SS_MAXSIZE - sizeof(unsigned short)];
>  				/* space to achieve desired size, */
>  				/* _SS_MAXSIZE value minus size of ss_family */
> -} __attribute__ ((aligned(_K_SS_ALIGNSIZE)));	/* force desired alignment */
> +			};
> +		};
> +};
> 
>  #endif /* _UAPI_LINUX_SOCKET_H */
> --
> 1.8.3.1

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-07-30 14:59 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-07-30 14:38 [PATCH v2] net/socket: fix GCC8+ Wpacked-not-aligned warnings Qian Cai
2019-07-30 14:38 ` Qian Cai
2019-07-30 14:45 ` Marcelo Ricardo Leitner
2019-07-30 14:45   ` Marcelo Ricardo Leitner
2019-07-30 14:59 ` David Laight

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