[libvirt] [RFC] libvirt-admin: Mark symbols as local

[Guido Günther]

On Wed, Aug 12, 2015 at 01:07:46PM +0100, Daniel P. Berrange wrote:
> On Wed, Aug 12, 2015 at 01:49:46PM +0200, Guido Günther wrote:
> > On Wed, Aug 12, 2015 at 11:15:58AM +0100, Daniel P. Berrange wrote:
> > > On Tue, Aug 11, 2015 at 09:24:59PM +0200, Guido Günther wrote:
> > > > Otherwise we're leaking some 30+ symbols like
> > > > 
> > > >    virAdmConnectClass
> > > >    virAdmConnectNew
> > > >    virConnectClass
> > > >    virConnectCloseCallbackDataClass
> > > >    virDomainClass
> > > >    ...
> > > > 
> > > > I marked the one symbol needed by the deamon as
> > > > LIBVIRT_ADMIN_PRIVATE_<VERSION> for now.
> > > 
> > > How are you identifying those as leaked ?
> > 
> > I tripped on this by dpkg-gensymbols[1] which uses objdump.
> > 
> >     objdump -w --dynamic-syms src/.libs/libvirt-admin.so | grep " g "
> > 
> > The g meaning global visibility. A similar result can be achieved with
> > "nm -D".
> > 
> > > IIRC, exports are those symbols marked with 'T' in the nm
> > > output:
> > > 
> > > [man nm]
> > >        ·   The symbol type.  At least the following types are used;
> > >            others are, as well, depending on the object file format.
> > >            If lowercase, the symbol is usually local; if uppercase,
> > >            the symbol is global (external).  There are however a few
> > >            lowercase symbols that are shown for special global
> > >            symbols ("u", "v" and "w").
> > > 
> > >            "T"
> > >            "t" The symbol is in the text (code) section.
> > > [/man]
> > > 
> > > # nm -a .libs/libvirt-admin.so | grep ' T '
> > > 0000000000001c80 T virAdmConnectClose
> > > 00000000000017d0 T virAdmConnectOpen
> > > 0000000000001d30 T virAdmConnectRef
> > > 
> > > # nm -a .libs/libvirt-admin.so | grep virAdmConnectNew
> > > 00000000000037c0 t virAdmConnectNew
> > > 
> > > So, IIUC, that lowercase 't' means the symol is local, and
> > > exported.
> > 
> > I'm seeing
> > 
> >     0000000000003f00 T virAdmConnectNew
> > 
> > so this is consistent with the above but different from what you're
> > seeing. This binutils 2.25 in case this matters. I think having a
> > 
> >   local:
> >      *;
> > 
> > Is a good think to have in any case.
> 
> Yeah, that's probably right. BTW, can you check libvirt-lxc.so and
> libvirt-qemu.so too as they don't have the 'local: *' bit in their
> syms files either AFAICT.

They look good:

$ objdump -w --dynamic-syms src/.libs/libvirt-lxc.so | grep " g "
0000000000000000 g    DO *ABS*	0000000000000000  LIBVIRT_LXC_1.0.4 LIBVIRT_LXC_1.0.4
0000000000001360 g    DF .text	0000000000000226  LIBVIRT_LXC_1.0.2 virDomainLxcEnterNamespace
0000000000001590 g    DF .text	000000000000044d  LIBVIRT_LXC_1.0.4 virDomainLxcEnterSecurityLabel
00000000000010e0 g    DF .text	000000000000027b  LIBVIRT_LXC_1.0.2 virDomainLxcOpenNamespace
0000000000203030 g    D  .bss	0000000000000000  Base        _end
0000000000203028 g    D  .data	0000000000000000  Base        _edata
0000000000203028 g    D  .bss	0000000000000000  Base        __bss_start
0000000000000000 g    DO *ABS*	0000000000000000  LIBVIRT_LXC_1.0.2 LIBVIRT_LXC_1.0.2
0000000000000e20 g    DF .init	0000000000000000  Base        _init
00000000000019e0 g    DF .fini	0000000000000000  Base        _fini

$ objdump -w --dynamic-syms src/.libs/libvirt-qemu.so | grep " g "
0000000000000000 g    DO *ABS*	0000000000000000  LIBVIRT_QEMU_0.9.4 LIBVIRT_QEMU_0.9.4
0000000000001410 g    DF .text	00000000000003a9  LIBVIRT_QEMU_1.2.3 virConnectDomainQemuMonitorEventRegister
0000000000203030 g    D  .bss	0000000000000000  Base        _end
0000000000203028 g    D  .data	0000000000000000  Base        _edata
00000000000011e0 g    DF .text	0000000000000226  LIBVIRT_QEMU_0.10.0 virDomainQemuAgentCommand
0000000000000d80 g    DF .text	000000000000028b  LIBVIRT_QEMU_0.8.3 virDomainQemuMonitorCommand
0000000000000000 g    DO *ABS*	0000000000000000  LIBVIRT_QEMU_0.10.0 LIBVIRT_QEMU_0.10.0
0000000000203028 g    D  .bss	0000000000000000  Base        __bss_start
0000000000000b98 g    DF .init	0000000000000000  Base        _init
0000000000001010 g    DF .text	00000000000001ca  LIBVIRT_QEMU_0.9.4 virDomainQemuAttach
0000000000001984 g    DF .fini	0000000000000000  Base        _fini
00000000000017c0 g    DF .text	00000000000001c1  LIBVIRT_QEMU_1.2.3 virConnectDomainQemuMonitorEventDeregister
0000000000000000 g    DO *ABS*	0000000000000000  LIBVIRT_QEMU_0.8.3 LIBVIRT_QEMU_0.8.3
0000000000000000 g    DO *ABS*	0000000000000000  LIBVIRT_QEMU_1.2.3 LIBVIRT_QEMU_1.2.3

Cheers,
 -- Guido