Re: [RFC PATCH 7/9] hurd: Generalize init-first.c to support x86_64

[Samuel Thibault]

Sergey Bugaev, le lun. 20 févr. 2023 20:10:29 +0300, a ecrit:
> - the implementation does not seem to actually switch stacks (in fact,
> I have removed the unused switch_stacks function in the last commit)
> -- so the "gets called with the stack just as the application's entry
> point will see it" property may not be important anymore?

That's possible, yes.

> So my thinking goes, why don't we just hook into _dl_start, which
> already has this very pointer? And in fact, _dl_start calls
> _dl_sysdep_start, for which there is already a Hurd version. Can't we
> just call our logic from there, and not worry about the stack layout
> and overwriting return addresses?

Possibly, yes.

> That would work for the SHARED case; we also need to do something for
> the static case. In that case, we are invoked by static-start.S; do I
> understand it right that the argc/argv/whatever is still located
> on-stack even on x86_64 in this case, and not passed in registers
> according to the calling convention?

I don't know. But you can check on Linux, we'll probably want to use the
same ABI.

Samuel