Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding

On Thu, Oct 31, 2024 at 1:57 PM Andrii Nakryiko
<[email protected]> wrote:
>
> On Tue, Oct 29, 2024 at 10:53 PM Josh Poimboeuf <[email protected]> wrote:
> >
> > On Tue, Oct 29, 2024 at 04:32:40PM -0700, Andrii Nakryiko wrote:
> > > > +static int find_fde(struct sframe_section *sec, unsigned long ip,
> > > > +                   struct sframe_fde *fde)
> > > > +{
> > > > +       struct sframe_fde __user *first, *last, *found = NULL;
> > > > +       u32 ip_off, func_off_low = 0, func_off_high = -1;
> > > > +
> > > > +       ip_off = ip - sec->sframe_addr;
> > >
> > > what if ip_off is larger than 4GB? ELF section can be bigger than 4GB, right?
> >
> > That's baked into sframe v2.
>
> I believe we do have large production binaries with more than 4GB of
> text, what are we going to do about them? It would be interesting to
> hear sframe people's opinion. Adding such a far-reaching new format in
> 2024 with these limitations is kind of sad. At the very least maybe we
> should allow some form of chaining sframe definitions to cover more
> than 4GB segments? Please CC relevant folks, I'm wondering what
> they're thinking about this.

FWIW, Google has such large binaries, too.
https://llvm.org/devmtg/2023-10/slides/quicktalks/Eubanks-CompromisesWithLargeX86-64Binaries.pdf
-- 
Thanks,
~Nick Desaulniers