10.0-RC1: net/mpd5 crashes in NgMkSockNode due to stack alignment on ARM EABI

[Guy Yur]

Hi,

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.


Regards,
Guy
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