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