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Date:      Mon, 30 Apr 2018 12:07:35 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 227552] w, uptime i386 cordeump
Message-ID:  <bug-227552-227-lE7MDwvtyL@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-227552-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-227552-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D227552

--- Comment #12 from Dimitry Andric <dim@FreeBSD.org> ---
I bisected, and it turns out r331838 (the merge of clang 6.0.0 and follow-up
fixes) is the first revision with those segfaults:

# ulimit -c 0; for i in /jail/test-r*; do echo "Using jail: $i"; chroot $i
/usr/bin/w; done
Using jail: /jail/test-r331837
12:00PM  up 13:47, 0 users, load averages: 0.23, 0.24, 0.60
USER       TTY      FROM                                      LOGIN@  IDLE =
WHAT
Using jail: /jail/test-r331838
Segmentation fault

Since all of the jail in r331837 has been compiled with clang 5.0.1, and al=
l of
r331838 with clang 6.0.0, it is hard to say what is the exact cause.

Interestingly, moving around the libraries used by w seems to influence the
crash, at least for me.  So for example:

$ ldd /usr/bin/w
/usr/bin/w:
        libkvm.so.7 =3D> /lib/libkvm.so.7 (0x28070000)
        libsbuf.so.6 =3D> /lib/libsbuf.so.6 (0x2807d000)
        libxo.so.0 =3D> /lib/libxo.so.0 (0x28080000)
        libutil.so.9 =3D> /lib/libutil.so.9 (0x28099000)
        libc.so.7 =3D> /lib/libc.so.7 (0x280ab000)
        libelf.so.2 =3D> /lib/libelf.so.2 (0x2820a000)

$ /usr/bin/w
 2:05PM  up 13:53, 2 users, load averages: 2.31, 0.76, 0.66
USER       TTY      FROM                                      LOGIN@  IDLE =
WHAT
dim        pts/2    coleburn.home.andric.com                  2:02PM     - w

$ mkdir ~/foo

$ cp /lib/libkvm.so.7 /lib/libsbuf.so.6 /lib/libxo.so.0 /lib/libutil.so.9
/lib/libc.so.7 /lib/libelf.so.2 ~/foo

$ LD_LIBRARY_PATH=3D~/foo /usr/bin/w
Segmentation fault (core dumped)

Meaning, the exact same .so files, but in a different path, crash!  Current=
ly,
I'm thinking that this may be something in the dynamic linker, but I'm still
not sure.

--=20
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