linux-kernel - Re: [PATCH v5 0/3] bootconfig: Support embedding a bootconfig in kernel for non initrd boot

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Message-ID: <CAKwvOdmbMPBOGvcZNURK6qMx8gm7dGFiWmtX_yXheEqQ8CNLsA@mail.gmail.com>
Date:   Thu, 31 Mar 2022 10:31:02 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Padmanabha Srinivasaiah <treasure4paddy@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev,
        Masahiro Yamada <masahiroy@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v5 0/3] bootconfig: Support embedding a bootconfig in
 kernel for non initrd boot

On Wed, Mar 30, 2022 at 6:45 PM Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> Hi Nick,
>
> On Wed, 30 Mar 2022 11:04:50 -0700
> Nick Desaulniers <ndesaulniers@...gle.com> wrote:
>
> >
> > Any chance we can use
> >
> > CFLAGS_REMOVE_<file>.o := $(CC_FLAGS_LTO)
> >
> > a la
> > commit d2dcd3e37475 ("x86, cpu: disable LTO for cpu.c")
>
> Hm, this looks good to me. Let me confirm that works.
> (Does this mean the bootconfig.o will be compiled to elf binary?)

I know we went with Masahiro's suggestion, which is clever and better,
but to answer this question; yes, under LTO, the linker can link
together inputs that are a mix of ELF object files (basically, no LTO
optimizations) with LLVM IR (w/ LTO optimizations between such files).
-- 
Thanks,
~Nick Desaulniers