Date: Thu, 9 Jan 2014 15:38:58 -0800 From: John-Mark Gurney <jmg@funkthat.com> To: Guy Yur <guyyur@gmail.com> Cc: freebsd-net@freebsd.org, freebsd-arm@freebsd.org, Gleb Smirnoff <glebius@freebsd.org> Subject: Re: 10.0-RC1, armv6: "pfctl -s state" crashes on BeagleBone Black due to unaligned access Message-ID: <20140109233858.GL46596@funkthat.com> In-Reply-To: <CAC67Hz--9ur8wLbqkB=aw8fK9MXjokZi9qULVa-ox_uubUz0vQ@mail.gmail.com> References: <CAC67Hz_QXcHHSFOLLgUGqLWRQpzhRRv_b%2BWGMMQsfk-VQp74RA@mail.gmail.com> <20140109104223.GS71033@FreeBSD.org> <CAC67Hz-Rz557COtyE1AurduZrstOqaMaA_H9VzBypsaHfSc=cg@mail.gmail.com> <20140109222610.GJ46596@funkthat.com> <CAC67Hz--9ur8wLbqkB=aw8fK9MXjokZi9qULVa-ox_uubUz0vQ@mail.gmail.com>
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Guy Yur wrote this message on Fri, Jan 10, 2014 at 01:04 +0200:
> On Fri, Jan 10, 2014 at 12:26 AM, John-Mark Gurney <jmg@funkthat.com> wrote:
> > Guy Yur wrote this message on Fri, Jan 10, 2014 at 00:17 +0200:
> >> On Thu, Jan 9, 2014 at 12:42 PM, Gleb Smirnoff <glebius@freebsd.org> wrote:
> >> > Guy,
> >> >
> >> > On Sat, Jan 04, 2014 at 03:06:02PM +0200, Guy Yur wrote:
> >> > G> I am running 10.0-RC1 arm.armv6 on the BeagleBone Black.
> >> > G> The "pfctl -s state" command is crashing when trying to print the
> >> > G> second entry.
> >>
>
> > Ok, that makes sense... so, either we mark struct pf_addr as __packed,
> > or we do some nasty stuff, like the following in print_host:
> > struct {
> > struct pf_addr a
> > } *uaddr __packed;
> >
> > uaddr = addr;
> > aw.v.a.addr = uaddr->a;
> >
> > it's not pretty, but I believe it would work...
>
> For performance reasons, I don't think pf_addr should be marked as __packed.
>
> I attached the changes I am now using in print_state() since there is
> no need to copy
> the full pfsync_state, only pf_addr.
> I converted sk and nk from pointers to structs on the stack and using
> struct copy.
> pf_addr is 16 bytes.
Did you look at using the above trick?
Since we are iterating over a list, that'll be a lot of copies, plus,
I'm not sure that your fix will be guaranteed to work for ever.. since
there isn't a requirement that the copy happens w/ bcopy/memcpy or some
other copy routine that assumes things might not be aligned...
Specificly these:
- sk = &s->key[PF_SK_STACK];
- nk = &s->key[PF_SK_WIRE];
+ sk = s->key[PF_SK_STACK];
+ nk = s->key[PF_SK_WIRE];
since s->key is already assumed to be aligned, a future compiler could
be smart enough to say, I'm not going to use the stack.. That
would/could happen if print_host's addr arg grew a const which it
could...
Also, I just realized that some of the lines modify sk (setting port),
but you don't write those modifications back to s->key[PF_SK_STACK]...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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