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Re: [PATCH 2/3] libdwfl: Add minisymtab support.
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Tue, 22 Jan 2013 16:46:48 +0100
- Subject: Re: [PATCH 2/3] libdwfl: Add minisymtab support.
On Fri, 2013-01-18 at 18:48 +0100, Jan Kratochvil wrote:
> On Wed, 16 Jan 2013 15:54:13 +0100, Mark Wielaard wrote:
> > diff --git a/libdwfl/dwfl_module_addrsym.c b/libdwfl/dwfl_module_addrsym.c
> > index fdc95fc..0e4de9f 100644
> > --- a/libdwfl/dwfl_module_addrsym.c
> > +++ b/libdwfl/dwfl_module_addrsym.c
> [...]
> > @@ -168,17 +173,19 @@ dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
> > }
> > }
> >
> > - /* First go through global symbols. mod->first_global is setup by
> > - dwfl_module_getsymtab to the index of the first global symbol in
> > - the module's symbol table, or -1 when unknown. All symbols with
> > - local binding come first in the symbol table, then all globals. */
> > - search_table (mod->first_global < 0 ? 1 : mod->first_global, syments);
> > + /* First go through global symbols. mod->first_global and
> > + mod->aux_first_global are setup by dwfl_module_getsymtab to the
> > + index of the first global symbol in the module's symbol table, or
> > + -1 when unknown. All symbols with local binding come first in
> > + the symbol table, then all globals. */
> > + int first_global = mod->first_global + mod->aux_first_global - 1;
>
> aux_first_global is not initialized to -1 anywhere so in the normal case
> without minisymtab it is left initialized as 0.
Yeah, good catch. And although first_global was initialized to -1 that
was really unnecessary (as you point out below load_symtab now always
sets it), because we don't use that as marker anymore. I have updated
the comment and removed that -1 initialization.
> I have found for example /usr/bin/loginctl from systemd-44-23.fc17.x86_64:
>
> Symbol table '.dynsym' contains 147 entries:
> Num: Value Size Type Bind Vis Ndx Name
> 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
> 1: 0000000000614444 0 NOTYPE LOCAL DEFAULT ABS _edata
> 2: 0000000000614cd0 0 NOTYPE LOCAL DEFAULT ABS _end
> 3: 0000000000614444 0 NOTYPE LOCAL DEFAULT ABS __bss_start
>
> So I agree now .dynsym may contain local symbols, but I still do not
> understand how that happens (systemd does not rebuild for me locally).
>
> Isn't it rather a bug of the build toolchain for systemd?
I thought it was a toolchain bug but understand now that if there are
relocations that depend on local symbols those symbols need to be
in .dynsym.
> Otherwise it looks OK to me.
Thanks. I have merged it into master.
Cheers,
Mark