Re: [PATCH 17/22] arm64: vdso: disable LTO

Andi Kleen
2020-06-24T23:52:05Z

On Wed, Jun 24, 2020 at 02:09:40PM -0700, Nick Desaulniers wrote:
> On Wed, Jun 24, 2020 at 1:58 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samitolvanen@google.com> wrote:
> > >
> > > Filter out CC_FLAGS_LTO for the vDSO.
> >
> > Just curious about this patch (and the following one for x86's vdso),
> > do you happen to recall specifically what the issues with the vdso's
> > are?
>
> + Andi (tangential, I actually have a bunch of tabs open with slides
> from http://halobates.de/ right now)
> 58edae3aac9f2
> 67424d5a22124
> $ git log -S DISABLE_LTO

I think I did it originally because the vDSO linker step didn't do
all the magic needed for gcc LTO. But it also doesn't seem to be
very useful for just a few functions that don't have complex
interactions, and somewhat risky for violating some assumptions.

-Andi