From: Andres Freund <andres@anarazel.de>
To: xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org,
       Jeremy Fitzhardinge <jeremy@goop.org>
Subject: "hwcap 0 nosegneg" doesnt work with paravirt_ops xen as of 2.6.23.9
Date: Wed, 28 Nov 2007 18:29:24 +0100
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Hi all,

after converting a host from using a ubuntu patched 2.6.22 domU to using=20
2.6.23 xen via paravirt_ops (no configuration change except devicename chan=
ge=20
in fstab, and another getty running) ldconfig no longer picks up the nosegn=
eg=20
libc leading to segfaults for some programs.

/etc/ld.so.conf.d/xen.conf:
hwcap 0 nosegneg

On ubuntu's 2.6.22-xen:
ldd /usr/bin/perl
        linux-gate.so.1 =3D>  (0xf57fe000)
        libdl.so.2 =3D> /lib/tls/i686/nosegneg/libdl.so.2 (0xb7f90000)
        libm.so.6 =3D> /lib/tls/i686/nosegneg/libm.so.6 (0xb7f6b000)
        libpthread.so.0 =3D> /lib/tls/i686/nosegneg/libpthread.so.0 (0xb7f5=
3000)
        libc.so.6 =3D> /lib/tls/i686/nosegneg/libc.so.6 (0xb7e05000)
        libcrypt.so.1 =3D> /lib/tls/i686/nosegneg/libcrypt.so.1 (0xb7dd7000)
        /lib/ld-linux.so.2 (0xb7f9d000)

On selfcompiled 2.6.23.9:
ldd /usr/bin/perl
        linux-gate.so.1 =3D>  (0xf57fc000)
        libdl.so.2 =3D> /lib/tls/i686/cmov/libdl.so.2 (0xb7f3b000)
        libm.so.6 =3D> /lib/tls/i686/cmov/libm.so.6 (0xb7f16000)
        libpthread.so.0 =3D> /lib/tls/i686/cmov/libpthread.so.0 (0xb7efe000)
        libc.so.6 =3D> /lib/tls/i686/cmov/libc.so.6 (0xb7db3000)
        libcrypt.so.1 =3D> /lib/tls/i686/cmov/libcrypt.so.1 (0xb7d85000)
        /lib/ld-linux.so.2 (0xb7f46000)


I now discover, that after some playing around (during discovering what the=
=20
problem is) i must have changed something, because ldd still shows the use =
of=20
the i686/cmov libraries, but applications reliably causing crashes earlier,=
=20
dont do so anymore.

Perhaps Im all wrong, and paravirt_ops doesnt need the nosegneg versions an=
d=20
just a ldconfig or so (which seems strange because the result before and=20
after the ldconfig were the same).

Greetings,=20

Andres Freund


PS: I did this conversion mainly, because I was getting quite random crashe=
s=20
inside the domU. I guess, as this was a vendor kernel + xensource xen kerne=
l,=20
this isnt appropriate for lkml? As well as the crashes of the Dom0 (ubuntu=
=20
again)?

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