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SubjectRe: [PATCH] Fix an inproper alignment accessing in irda protocol stack
Hi Andrew,

Thanks. I modified the patch (don't know if there is any way better
to solve this).

Signed-off-by: Luke Yang <luke.adi@gmail.com>

irlmp.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletion(-)

--- net/irda/irlmp.c.old 2006-06-08 14:49:20.000000000 +0800
+++ net/irda/irlmp.c 2006-06-09 19:43:58.000000000 +0800
@@ -849,7 +849,13 @@
}

/* Construct new discovery info to be used by IrLAP, */
- u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
+#ifdef __LITTLE_ENDIAN
+ irlmp->discovery_cmd.data.hints[0] = irlmp->hints.word & 0xff;
+ irlmp->discovery_cmd.data.hints[1] = (irlmp->hints.word & 0xff00) >> 8;
+#else /* ifdef __BIG_ENDIAN */
+ irlmp->discovery_cmd.data.hints[0] = (irlmp->hints.word & 0xff00) >> 8;
+ irlmp->discovery_cmd.data.hints[1] = irlmp->hints.word & 0xff;
+#endif

/*
* Set character set for device name (we use ASCII), and
On 6/8/06, Andrew Morton <akpm@osdl.org> wrote:
> On Thu, 8 Jun 2006 15:15:11 +0800
> "Luke Yang" <luke.adi@gmail.com> wrote:
>
> > Hi all,
> >
> > For "struct irda_device_info" in irda.h:
> > struct irda_device_info {
> > __u32 saddr; /* Address of local interface */
> > __u32 daddr; /* Address of remote device */
> > char info[22]; /* Description */
> > __u8 charset; /* Charset used for description */
> > __u8 hints[2]; /* Hint bits */
> > };
> > The "hints" member aligns at the third byte of a word, an odd
> > address. So if we visit "hints" as a short in irlmp.c:
> >
> > u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
> >
> > will cause alignment problem on some machines. Architectures with
> > strict alignment rules do not allow 16-bit read on an odd address.
> >
> > Signed-off-by: Luke Yang <luke.adi@gmail.com>
> >
> > irlmp.c | 3 ++-
> > 1 files changed, 2 insertions(+), 1 deletion(-)
> >
> > --- net/irda/irlmp.c.old 2006-06-08 14:49:20.000000000 +0800
> > +++ net/irda/irlmp.c 2006-06-08 14:54:29.000000000 +0800
> > @@ -849,7 +849,8 @@
> > }
> >
> > /* Construct new discovery info to be used by IrLAP, */
> > - u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
> > + irlmp->discovery_cmd.data.hints[0] = irlmp->hints.word & 0xff;
> > + irlmp->discovery_cmd.data.hints[1] = (irlmp->hints.word & 0xff00) >> 8;
>
> This change will have the effect of swapping those two bytes on big-endian
> machines.
>
>


--
Best regards,
Luke Yang
luke.adi@gmail.com
--- net/irda/irlmp.c.old 2006-06-08 14:49:20.000000000 +0800
+++ net/irda/irlmp.c 2006-06-09 19:43:58.000000000 +0800
@@ -849,7 +849,13 @@
}

/* Construct new discovery info to be used by IrLAP, */
- u16ho(irlmp->discovery_cmd.data.hints) = irlmp->hints.word;
+#ifdef __LITTLE_ENDIAN
+ irlmp->discovery_cmd.data.hints[0] = irlmp->hints.word & 0xff;
+ irlmp->discovery_cmd.data.hints[1] = (irlmp->hints.word & 0xff00) >> 8;
+#else /* ifdef __BIG_ENDIAN */
+ irlmp->discovery_cmd.data.hints[0] = (irlmp->hints.word & 0xff00) >> 8;
+ irlmp->discovery_cmd.data.hints[1] = irlmp->hints.word & 0xff;
+#endif

/*
* Set character set for device name (we use ASCII), and
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