[Skiboot] [PATCH 02/10] Introduce hwprobe facility to avoid hard-coding probe functions

[Dan Horák]

On Tue, 29 Jun 2021 06:23:19 +1000
Nicholas Piggin <npiggin at gmail.com> wrote:

> Excerpts from Dan Horák's message of June 29, 2021 1:11 am:
> > On Sat, 26 Jun 2021 12:38:16 +1000
> > Nicholas Piggin <npiggin at gmail.com> wrote:
> > 
> >> From: Stewart Smith <stewart at flamingspork.com>
> >> 
> >> hwprobe is a little system to have different hardware probing modules
> >> run in the dependency order they choose rather than hard coding
> >> that order in core/init.c.
> > 
> > I already commented in January, but the special linker section plus
> > start/end label style is not compatible with LTO and possibly relies on
> > undefined behaviour in the C language. I don't think LTO is hot topic
> > for system firmware, but it could change. So at minimum it should be
> > documented in the commit message.
> > 
> > https://lists.ozlabs.org/pipermail/skiboot/2021-January/017470.html
> > https://bugzilla.redhat.com/show_bug.cgi?id=1877485#c14
> > https://sigrok.org/bugzilla/show_bug.cgi?id=1433
> 
> It looks like placing the section with the linker script as this patch 
> does works okay, just not what they were doing before which seems to be
> trying to define the section start/end symbols in C. AFAIKS.
> 
> The linker script method is the normal one including Linux kernel which
> is being compiled with LTO AFAIK.
> 
> LTO might be interesting for skiboot for space reduction particularly.
> We have a link time dead code elimination option (a basic kind of LTO)
> already which can save quite a bit of space. A modern LTO might be able
> to save even more.

thanks, Nick, this clears my concerns


		Dan