Date: Sun, 22 Dec 2013 00:46:04 +0200 From: Guy Yur <guyyur@gmail.com> To: freebsd-arm@freebsd.org, freebsd-net@freebsd.org Subject: Re: 10.0-RC1: net/mpd5 crashes in NgMkSockNode due to stack alignment on ARM EABI Message-ID: <CAC67Hz-U-CgC6VgTsj4WpKGdGh7aGWVmBneiN8sangVwuh_4pw@mail.gmail.com> In-Reply-To: <20131221191552.GE99167@funkthat.com> References: <CAC67Hz82VBT1_BBH6E18ycDxUdWbgFcahNo1W0kH-TcH7iB=8Q@mail.gmail.com> <20131221191552.GE99167@funkthat.com>
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[-- Attachment #1 --]
On Sat, Dec 21, 2013 at 9:15 PM, John-Mark Gurney <jmg@funkthat.com> wrote:
> Guy Yur wrote this message on Sat, Dec 21, 2013 at 19:24 +0200:
>> I am running 10.0-RC1 on the BeagleBone Black and the net/mpd5 port is
>> crashing in libnetgraph NgMkSockNode due to stack alignment.
>>
>> 10.0-RC1 World and kernel were compiled in a VirtualBox VM running
>> 9.2-RELEASE-p2 i386.
>> clang and ARM_EABI used as the default make options.
>>
>> Added prints in NgMkSockNode show rbuf is aligned on 2-byte and not
>> 4-byte which is needed to access ni->id (a uint32_t).
>>
>> ni = 0xbfffe87a
>> rbuf = 0xbfffe842
>> sizeof(resp->header) = 56
>>
>>
>> (gdb) bt
>> #0 0x201529a0 in NgMkSockNode (name=<value optimized out>, csp=0xbfffe95c,
>> dsp=0xbfffe958) at /usr/src/lib/libnetgraph/sock.c:134
>> #1 0x00037b9c in MppcTestCap () at ccp_mppc.c:754
>> #2 0x0007c1f4 in main (ac=4, av=0xbfffeb90) at main.c:248
>> #3 0x0000d1b0 in __start (argc=4, argv=0xbfffeb90, env=0xbfffeba4,
>> ps_strings=<value optimized out>, obj=<value optimized out>,
>> cleanup=<value optimized out>) at /usr/src/lib/csu/arm/crt1.c:115
>> #4 0x203e9dc0 in _thr_ast (curthread=0x200fd000)
>> at /usr/src/lib/libthr/thread/thr_sig.c:265
>>
>>
>> Putting rbuf in a union with struct ng_mesg sorted the alignment to
>> 4-byte and mpd5 didn't crash.
>> I attached the changes I used to test mpd5 doesn't crash with correct alignment.
>
> The patch looks correct, but lets make sure that the -net people don't
> have an issue with it...
>
> I've reattached Guy's patch for review.
>
> Guy, bug me in a week or so if I haven't committed it, and I will...
>
> Thanks for tracking this down.
>
> --
> John-Mark Gurney Voice: +1 415 225 5579
>
> "All that I will do, has been done, All that I have, has not."
Hi John,
Should I still file a PR?
1. I noticed my patch causes a style bug with the rbuf line now taking
87 columns.
2. Since the union now has a ng_mesg struct, the casting to resp can
be skipped and the union member used directly.
Attached new patch breaking the rbuf line and swapping resp usage with
res.res and &res.res
Maybe a different name than res should be used for the union or the member.
I only tested the new patch compiles for arm.armv6, haven't verified it.
Thanks,
Guy
[-- Attachment #2 --]
Index: lib/libnetgraph/sock.c
===================================================================
--- lib/libnetgraph/sock.c (revision 259250)
+++ lib/libnetgraph/sock.c (working copy)
@@ -111,9 +111,12 @@
/* Save node name */
strlcpy(namebuf, name, sizeof(namebuf));
} else if (dsp != NULL) {
- u_char rbuf[sizeof(struct ng_mesg) + sizeof(struct nodeinfo)];
- struct ng_mesg *const resp = (struct ng_mesg *) rbuf;
- struct nodeinfo *const ni = (struct nodeinfo *) resp->data;
+ union {
+ u_char rbuf[sizeof(struct ng_mesg) +
+ sizeof(struct nodeinfo)];
+ struct ng_mesg res;
+ } res;
+ struct nodeinfo *const ni = (struct nodeinfo *) res.res.data;
/* Find out the node ID */
if (NgSendMsg(cs, ".", NGM_GENERIC_COOKIE,
@@ -123,7 +126,7 @@
NGLOG("send nodeinfo");
goto errout;
}
- if (NgRecvMsg(cs, resp, sizeof(rbuf), NULL) < 0) {
+ if (NgRecvMsg(cs, &res.res, sizeof(res.rbuf), NULL) < 0) {
errnosv = errno;
if (_gNgDebugLevel >= 1)
NGLOG("recv nodeinfo");
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