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Date: Thu, 25 Jun 2020 20:33:51 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>, Will Deacon <will@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Kees Cook <keescook@...omium.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
clang-built-linux@...glegroups.com,
kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
x86@...nel.org
Subject: Re: [PATCH 05/22] kbuild: lto: postpone objtool
On Thu, Jun 25, 2020 at 09:22:26AM -0700, Sami Tolvanen wrote:
> On Thu, Jun 25, 2020 at 09:47:16AM +0200, Peter Zijlstra wrote:
> > Right, then we need to make --no-vmlinux work properly when
> > !DEBUG_ENTRY, which I think might be buggered due to us overriding the
> > argument when the objname ends with "vmlinux.o".
>
> Right. Can we just remove that and pass --vmlinux to objtool in
> link-vmlinux.sh, or is the override necessary somewhere else?
Think we can remove it; it was just convenient when running manually.
> > > > > +ifdef CONFIG_STACK_VALIDATION
> > > > > +ifneq ($(SKIP_STACK_VALIDATION),1)
> > > > > +cmd_ld_ko_o += \
> > > > > + $(objtree)/tools/objtool/objtool \
> > > > > + $(if $(CONFIG_UNWINDER_ORC),orc generate,check) \
> > > > > + --module \
> > > > > + $(if $(CONFIG_FRAME_POINTER),,--no-fp) \
> > > > > + $(if $(CONFIG_GCOV_KERNEL),--no-unreachable,) \
> > > > > + $(if $(CONFIG_RETPOLINE),--retpoline,) \
> > > > > + $(if $(CONFIG_X86_SMAP),--uaccess,) \
> > > > > + $(@:.ko=$(prelink-ext).o);
> > > > > +
> > > > > +endif # SKIP_STACK_VALIDATION
> > > > > +endif # CONFIG_STACK_VALIDATION
> > > >
> > > > What about the objtool invocation from link-vmlinux.sh ?
> > >
> > > What about it? The existing objtool_link invocation in link-vmlinux.sh
> > > works fine for our purposes as well.
> >
> > Well, I was wondering why you're adding yet another objtool invocation
> > while we already have one.
>
> Because we can't run objtool until we have compiled bitcode to native
> code, so for modules, we're need another invocation after everything has
> been compiled.
Well, that I understand, my question was why we need one in
scripts/link-vmlinux.sh and an additional one. I think we're just
talking past one another and agree we only need one.
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