2005-09-26 20:03:34

by Alex Williamson

Subject: [PATCH] sys_sendmsg() alignment bug fix

The patch below adds an alignment attribute to the buffer used in
sys_sendmsg(). This eliminates an unaligned access warning on ia64.

Signed-off-by: Alex Williamson <[email protected]>

diff -r db9b9552a2b4 net/socket.c
--- a/net/socket.c Sat Sep 24 23:56:08 2005
+++ b/net/socket.c Mon Sep 26 13:44:09 2005
@@ -1700,7 +1700,9 @@
struct socket *sock;
char address[MAX_SOCK_ADDR];
struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
- unsigned char ctl[sizeof(struct cmsghdr) + 20]; /* 20 is size of ipv6_pktinfo */
+ unsigned char ctl[sizeof(struct cmsghdr) + 20]
+ __attribute__ ((aligned (sizeof(__kernel_size_t))));
+ /* 20 is size of ipv6_pktinfo */
unsigned char *ctl_buf = ctl;
struct msghdr msg_sys;
int err, ctl_len, iov_size, total_len;

2005-09-26 20:36:36

by Andrew Morton

Subject: Re: [PATCH] sys_sendmsg() alignment bug fix

Alex Williamson <[email protected]> wrote:
>
> The patch below adds an alignment attribute to the buffer used in
> sys_sendmsg(). This eliminates an unaligned access warning on ia64.
>

Vaguely surprised that the compiler cannot be taught to do this.

>
> diff -r db9b9552a2b4 net/socket.c
> --- a/net/socket.c Sat Sep 24 23:56:08 2005
> +++ b/net/socket.c Mon Sep 26 13:44:09 2005
> @@ -1700,7 +1700,9 @@
> struct socket *sock;
> char address[MAX_SOCK_ADDR];
> struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
> - unsigned char ctl[sizeof(struct cmsghdr) + 20]; /* 20 is size of ipv6_pktinfo */
> + unsigned char ctl[sizeof(struct cmsghdr) + 20]
> + __attribute__ ((aligned (sizeof(__kernel_size_t))));
> + /* 20 is size of ipv6_pktinfo */
> unsigned char *ctl_buf = ctl;
> struct msghdr msg_sys;
> int err, ctl_len, iov_size, total_len;

OK, thanks - I'll send this on to davem. It seems odd to be using
__kernel_size_t rather than size_t, but that's what struct cmshdr does
(also oddly).

2005-09-26 21:28:33

by David Miller

Subject: Re: [PATCH] sys_sendmsg() alignment bug fix

From: Andrew Morton <[email protected]>
Date: Mon, 26 Sep 2005 13:36:34 -0700

> OK, thanks - I'll send this on to davem. It seems odd to be using
> __kernel_size_t rather than size_t, but that's what struct cmshdr does
> (also oddly).

Applied, thanks.

2005-09-27 03:40:42

by Coywolf Qi Hunt

Subject: Re: [PATCH] sys_sendmsg() alignment bug fix

On 9/27/05, Alex Williamson <[email protected]> wrote:
> The patch below adds an alignment attribute to the buffer used in
> sys_sendmsg(). This eliminates an unaligned access warning on ia64.

Is this a warning fix or bug fix?
--
Coywolf Qi Hunt
http://sosdg.org/~coywolf/

2005-09-27 03:59:42

by Alex Williamson

Subject: Re: [PATCH] sys_sendmsg() alignment bug fix

On Tue, 2005-09-27 at 11:40 +0800, Coywolf Qi Hunt wrote:
> On 9/27/05, Alex Williamson <[email protected]> wrote:
> > The patch below adds an alignment attribute to the buffer used in
> > sys_sendmsg(). This eliminates an unaligned access warning on ia64.
>
> Is this a warning fix or bug fix?

Guess I'd have to classify it as a warning fix. ia64 is fairly
verbose about unaligned accesses by default, so the warning is printed
out runtime.

Alex

2005-09-27 04:50:35

by David Miller

Subject: Re: [PATCH] sys_sendmsg() alignment bug fix

From: Coywolf Qi Hunt <[email protected]>
Date: Tue, 27 Sep 2005 11:40:38 +0800

> On 9/27/05, Alex Williamson <[email protected]> wrote:
> > The patch below adds an alignment attribute to the buffer used in
> > sys_sendmsg(). This eliminates an unaligned access warning on ia64.
>
> Is this a warning fix or bug fix?

It doesn't generate a warning, but it does generate totally
unnecessary unaligned access traps on RISC systems.