On Thu, Mar 18, 2021 at 06:04:25PM +0100, Peter Zijlstra wrote:
> On Thu, Mar 18, 2021 at 11:36:40AM -0500, Josh Poimboeuf wrote:
> > > I was thinking you could get a section changed without touching
> > > relocations, but while that is theoretically possible, it is exceedingly
> > > unlikely (and objtool doesn't do that).
> >
> > Hm? This is a *relocation* section, not a normal one. So by
> > definition, it only changes when its relocations change.
>
> The way I read this code:
>
> list_for_each_entry(sec, &elf->sections, list) {
> if (sec->changed) {
> + if (sec->reloc &&
> + elf_rebuild_reloc_section(elf, sec->reloc)) {
> + WARN_ELF("elf_rebuild_reloc_section");
> + return -1;
> + }
>
> is that we iterate the regular sections (which could be dirtied because
> we changed some data), and if that section has a relocation section, we
> rebuild that for good measure (even though it might not have altered
> relocations).
>
> Or am I just totally confused ?
Ah, you're right. I'm the one that's confused. I guess I was also
confused when I wrote that hunk, but it just happens to work anyway.
It would be cleaner to do something like
if ((is_reloc_sec(sec) &&
elf_rebuild_reloc_section(elf, sec)) {
so we process the changed reloc section directly, instead of relying on
the (most likely) fact that the corresponding text section also changed.
--
Josh
