linux-kernel - Re: linux-next: manual merge of the tip tree with the kbuild tree

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Date:   Fri, 27 May 2022 11:19:02 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: manual merge of the tip tree with the kbuild tree

Hi Stephen, Josh,

On Tue, May 24, 2022 at 1:23 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> On Mon, May 23, 2022 at 03:47:58PM +1000, Stephen Rothwell wrote:
> > Hi all,
> >
> > On Mon, 23 May 2022 14:24:31 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> > >
> > > Today's linux-next merge of the tip tree got a conflict in:
> > >
> > >   scripts/Makefile.build
> > >
> > > between commit:
> > >
> > >   0212301af7bb ("kbuild: do not create *.prelink.o for Clang LTO or IBT")
> > >
> > > from the kbuild tree and commit:
> > >
> > >   753da4179d08 ("objtool: Remove --lto and --vmlinux in favor of --link")
> > >
> > > from the tip tree.
> > >
> > > I am not sure if I fixed this up correctly, please check the final result
> > > when linux-next is released.
> > >
> > > I fixed it up (I used the former version) and can carry the fix as
> > > necessary. This is now fixed as far as linux-next is concerned, but any
> > > non trivial conflicts should be mentioned to your upstream maintainer
> > > when your tree is submitted for merging.  You may also want to consider
> > > cooperating with the maintainer of the conflicting tree to minimise any
> > > particularly complex conflicts.
> >
> > That produced may warnings :-(   so I tried the below resolution instead.
>
> Looks good to me.  I guess the confusing bit was that in most cases,
> CONFIG_STACK_VALIDATION has been replaced with CONFIG_OBJTOOL.
>
> --
> Josh


Is this really a correct fix up?

I checked the linux-next.

It added:

$(obj)/%.o: linked-object := y

so, --linked is always passed.


Apparently, it changed the behavior.



[1] original behavior in Josh's commit

$ git checkout 753da4179d08b625d8df72e97724e22749969fd3
$ make defconfig
$ make -j8 kernel/
$ head -n 1   kernel/.fork.o.cmd


I do not see the "--linked" parameter in the objtool command.




[2] behavior in linux-next


$ git checkout next-20220523
$ make defconfig
$ make -j8 kernel/
$ head -n 1   kernel/.fork.o.cmd

I see the "--linked" parameter in the objtool command.

kernel/fork.o  is a direct output from GCC,
not from linker.






Josh,
Could you tell me:
when should --linked be added?
(and when should --linked not be added?)








--
Best Regards
Masahiro Yamada