Re: [PATCH v4 17/39] unwind_user/sframe: Add support for reading .sframe headers

Steven Rostedt
2025-01-24T20:13:33Z

On Fri, 24 Jan 2025 11:21:59 -0800
Josh Poimboeuf <jpoimboe@kernel.org> wrote:

> > given SFRAME_F_FRAME_POINTER in the header, is it really that
> > nonsensical and illegal to have zero FDEs/FREs? Maybe we should allow
> > that?
>
> It would seem a bit silly to create an empty .sframe section just to set
> that SFRAME_F_FRAME_POINTER bit. Regardless, there's nothing the kernel
> can do with that.
>
> > > + dbg("no fde/fre entries\n");
> > > + return -EINVAL;
> > > + }
> > > +
> > > + header_end = sec->sframe_start + SFRAME_HEADER_SIZE(shdr);
> > > + if (header_end >= sec->sframe_end) {
> >
> > if we allow zero FDEs/FREs, header_end == sec->sframe_end is legal, right?
>
> I suppose so, but again I'm not seeing any reason to support that.

Hmm, could that be useful for implementing a way to dynamically grow or
shrink an sframe because of jits? I'm just thinking about placeholders or
something.

-- Steve