linux-kernel - Re: [PATCH v1 0/3] objtool build improvements

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Message-ID: <CAP-5=fWQYzwEfzK0jW3FGAZwv4H7x3gXsDi1Dhiaj81odfKahw@mail.gmail.com>
Date:   Sat, 19 Nov 2022 15:01:05 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Stephane Eranian <eranian@...gle.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH v1 0/3] objtool build improvements

On Fri, Nov 18, 2022 at 9:47 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Thu, Nov 17, 2022 at 2:03 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > Install libsubcmd and then get headers from there, this avoids
> > inadvertent dependencies on things in tools/lib. Fix V=1
> > support. Clean up how HOSTCC is used to override CC to avoid CFLAGS
> > being set for say gcc, and then CC being overridden to clang. Support
> > HOSTCFLAGS as a make option.
>
> Hi Ian,
> Thanks for the patch set! I'm particularly interested in fixing the
> plumbing of HOSTCFLAGS into objtool properly.
>
> Does this patch series depend on recent work you were doing to perf
> and libsubcmd? When I apply it to mainline (84368d882b96) or
> linux-next (20221118), I observe build failures with it.
>
> ```
> /bin/sh: line 1: cd:
> /android0/kernel-all/tools/objtool/libsubcmd/tools/objtool/: No such
> file or directory
> ../../scripts/Makefile.include:17: *** output directory
> "/android0/kernel-all/tools/objtool/libsubcmd/tools/objtool/" does not
> exist.  Stop.
> make[3]: *** [Makefile:82:
> /android0/kernel-all/tools/objtool/libsubcmd/libsubcmd.a] Error 2
> make[3]: *** Waiting for unfinished jobs....
> builtin-check.c:6:10: fatal error: 'subcmd/parse-options.h' file not found
> #include <subcmd/parse-options.h>
>          ^~~~~~~~~~~~~~~~~~~~~~~~
> ```
> Which I also observe when just doing a regular kernel build and not
> just tools/objtool/.
>
> I tried to apply other recent series first, like
> https://lore.kernel.org/lkml/20221109184914.1357295-1-irogers@google.com/
> https://lore.kernel.org/linux-perf-users/20221116072211.2837834-2-irogers@google.com/
> but wasn't quite able to get the result to build.
>
> My plan to validate HOSTCFLAGS is:
> $ make LLVM=1 -j128 mrproper defconfig tools/objtool HOSTCFLAGS=-Os
> V=1 1> before.txt
> $ <apply patch series>
> $ make LLVM=1 -j128 mrproper defconfig tools/objtool HOSTCFLAGS=-Os
> V=1 1> after.txt
> $ meld before.txt after.txt

Thanks Nick! I think:
https://lore.kernel.org/lkml/20221109184914.1357295-3-irogers@google.com/
is necessary and already in Arnaldo's tree:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=perf%2Fcore
However, with that the output directory in libsubcmd is calculated
incorrectly and results in the error you see. I'll work on a v2 patch
set.

Thanks,
Ian

> >
> > Ian Rogers (3):
> >   objtool: Install libsubcmd in build
> >   objtool: Properly support make V=1
> >   objtool: Alter how HOSTCC is forced
> >
> >  tools/objtool/Build    |  2 --
> >  tools/objtool/Makefile | 68 +++++++++++++++++++++++++++++-------------
> >  2 files changed, 48 insertions(+), 22 deletions(-)
> >
> > --
> > 2.38.1.584.g0f3c55d4c2-goog
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers