[PATCH] Use GCC LTO wrapper to get real symbols from LTO IR objects

[H.J. Lu]

On Mon, Feb 10, 2020 at 3:02 PM Alan Modra <amodra@gmail.com> wrote:
>
> Wow, that's a lot of work to get proper symbol type.  What happens if

Very true.  I couldn't come up with a better solution without changing plugin
API.

> you run nm on a system where gcc isn't installed?  Or where the lto
> version doesn't match?

I assume standard GCC installation directory layout like

PREFIX/libexec/gcc/TARGET/VERSION/liblto_plugin.so
PREFIX/libexec/gcc/TARGET/VERSION/lto-wrapper

and

PREFIX/bin/TARGET-gcc

or

PREFIX/bin/gcc

If there is no gcc nor lto-wrapper at expected location, no real
symbols will be used.  If LTO version doesn't match, it is a
GCC installation problem.

> On Mon, Feb 10, 2020 at 01:31:16PM -0800, H.J. Lu wrote:
> > +  gcc_name = bfd_malloc (length + target_length + sizeof ("gcc"));
> > +  memcpy (gcc_name, real_name, length);
>
> No check of bfd_malloc return value before use.

Fixed.

> > +  wrapper_name = bfd_malloc (length + sizeof ("lto-wrapper"));
> > +  memcpy (wrapper_name, real_name, length);
>
> Again.

Fixed.

> > +  real_syms = (asymbol **) xmalloc (real_symsize);
>
> xmalloc shouldn't be used in libbfd.

Fixed.

> >    struct plugin_data_struct *plugin_data =
> >      bfd_alloc (abfd, sizeof (plugin_data_struct));
>
> This also doesn't check for NULL, preexisting bug.

Fixed.

> > +  int i;
> > +
> > +  /* NB: LTO symbols are owned by LTO plugin.  Create a copy so that we
> > +     can use it in bfd_plugin_canonicalize_symtab.  */
> > +  copy_of_syms = bfd_alloc (abfd, nsyms * sizeof (*syms));
> > +  memcpy (copy_of_syms, syms, nsyms * sizeof (*syms));
> > +  for (i = 0; i < nsyms; i++)
> > +    copy_of_syms[i].name = xstrdup (syms[i].name);
>
> xstrdup shouldn't be used in libbfd.

Fixed.

Here is the updated patch.

-- 
H.J.
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