Date:   Fri, 2 Sep 2022 09:01:47 +0800
From:   Philip Li <philip.li@...el.com>
To:     "Chen, Rong A" <rong.a.chen@...el.com>
CC:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "kernel test robot" <lkp@...el.com>,
        Kees Cook <keescook@...omium.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        "kbuild-all@...ts.01.org" <kbuild-all@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Masahiro Yamada" <masahiroy@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [kbuild-all] Re: powerpc-linux-objdump: Warning: Unrecognized
 form: 0x23

On Fri, Sep 02, 2022 at 08:54:14AM +0800, Chen, Rong A wrote:
> 
> 
> On 9/2/2022 1:04 AM, Nick Desaulniers wrote:
> > On Thu, Sep 1, 2022 at 9:55 AM Nathan Chancellor <nathan@...nel.org> wrote:
> > > 
> > > On Thu, Sep 01, 2022 at 01:52:42PM +0800, Chen, Rong A wrote:
> > > > 
> > > > 
> > > > On 9/1/2022 1:45 PM, Christophe Leroy wrote:
> > > > > 
> > > > > 
> > > > > Le 01/09/2022 à 06:59, Chen, Rong A a écrit :
> > > > > > 
> > > > > > 
> > > > > > On 9/1/2022 10:03 AM, Nathan Chancellor wrote:
> > > > > > > Hi Rong,
> > > > > > > 
> > > > > > > On Thu, Sep 01, 2022 at 09:15:58AM +0800, Chen, Rong A wrote:
> > > > > > > > 
> > > > > > > > 
> > > > > > > > On 8/31/2022 11:40 PM, Nathan Chancellor wrote:
> > > > > > > > > On Wed, Aug 31, 2022 at 02:52:36PM +0800, kernel test robot wrote:
> > > > > > > > > > tree:
> > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > > > > > > > > master
> > > > > > > > > > head:   dcf8e5633e2e69ad60b730ab5905608b756a032f
> > > > > > > > > > commit: f9b3cd24578401e7a392974b3353277286e49cee Kconfig.debug:
> > > > > > > > > > make DEBUG_INFO selectable from a choice
> > > > > > > > > > date:   5 months ago
> > > > > > > > > > config: powerpc-buildonly-randconfig-r003-20220830
> > > > > > > > > > (https://download.01.org/0day-ci/archive/20220831/202208311414.4OPuYS9K-lkp@intel.com/config)
> > > > > > > > > > compiler: clang version 16.0.0
> > > > > > > > > > (https://github.com/llvm/llvm-project
> > > > > > > > > > c7df82e4693c19e3fd2e25c83eb04d9deb7b7b59)
> > > > > > > > > > reproduce (this is a W=1 build):
> > > > > > > > > >             wget
> > > > > > > > > > https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > > > > > > > > >             chmod +x ~/bin/make.cross
> > > > > > > > > >             # install powerpc cross compiling tool for clang build
> > > > > > > > > >             # apt-get install binutils-powerpc-linux-gnu
> > > > > > > > > >             #
> > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f9b3cd24578401e7a392974b3353277286e49cee
> > > > > > > > > >             git remote add linus
> > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > > > > > > > >             git fetch --no-tags linus master
> > > > > > > > > >             git checkout f9b3cd24578401e7a392974b3353277286e49cee
> > > > > > > > > >             # save the config file
> > > > > > > > > >             mkdir build_dir && cp config build_dir/.config
> > > > > > > > > >             COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang
> > > > > > > > > > make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash
> > > > > > > > > > 
> > > > > > > > > > If you fix the issue, kindly add following tag where applicable
> > > > > > > > > > Reported-by: kernel test robot <lkp@...el.com>
> > > > > > > > > > 
> > > > > > > > > > All warnings (new ones prefixed by >>):
> > > > > > > > > > 
> > > > > > > > > > > > powerpc-linux-objdump: Warning: Unrecognized form: 0x23
> > > > > > > > > 
> > > > > > > > > Given this is clang 16.0.0 with
> > > > > > > > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y, which uses DWARF5 by
> > > > > > > > > default instead of DWARF4, it looks like older binutils not
> > > > > > > > > understanding DWARF5. What version of binutils is being used by the
> > > > > > > > > bot?
> > > > > > > > 
> > > > > > > > Hi Nathan,
> > > > > > > > 
> > > > > > > > We're using binutils v2.38.90.20220713-2
> > > > > > > > 
> > > > > > > > ||/ Name           Version            Architecture Description
> > > > > > > > +++-==============-==================-============-==========================================
> > > > > > > > ii  binutils       2.38.90.20220713-2 amd64        GNU assembler,
> > > > > > > > linker and binary utilities
> > > > > > > 
> > > > > > > Thanks for chiming in! This looks like the output of 'dpkg -l', right? I
> > > > > > 
> > > > > > Hi Nathan,
> > > > > > 
> > > > > > oh, yes, I misunderstood, it's not related to this package.
> > > > > > 
> > > > > > > noticed on second glance that the tuple for the objdump warning above is
> > > > > > > 'powerpc-linux-', which leads me to believe that a kernel.org toolchain
> > > > > > > (or a self compiled one) is being used. I would expect the tuple to be
> > > > > > > 'powerpc-linux-gnu-' if Debian's package was being used. Is that
> > > > > > > possible?
> > > > > > 
> > > > > > you are right, we used a self-compiled toolchain, we'll try the binutils
> > > > > > from debian package.
> > > > > 
> > > > > Can you first tell us the version you are using ?
> > > > > 
> > > > >      powerpc-linux-objdump -v
> > > > > 
> > > > > That will tell you the version.
> > > > 
> > > > Hi Christophe,
> > > > 
> > > > the version is v2.38:
> > > > 
> > > > $ ./powerpc-linux-objdump -v
> > > > GNU objdump (GNU Binutils) 2.38
> > > > Copyright (C) 2022 Free Software Foundation, Inc.
> > > > This program is free software; you may redistribute it under the terms of
> > > > the GNU General Public License version 3 or (at your option) any later
> > > > version.
> > > > This program has absolutely no warranty.
> > > 
> > > Thanks! I did some research and it seems like this warning is expected
> > > with binutils older than 2.39. The warning appears to come from
> > > read_and_display_attr_value() in binutils/dwarf.c. 0x22 and 0x23 are
> > > DW_FORM_loclistx and DW_FORM_rnglistx, which were only recently
> > > supported in that function.
> > > 
> > > https://sourceware.org/bugzilla/show_bug.cgi?id=28981
> > > https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=19c26da69d68d5d863f37c06ad73ab6292d02ffa
> > > 
> > > That change shipped in binutils 2.39. I am not really sure how we should
> > > work around this in the kernel, other than maybe requiring binutils
> > > 2.39+ for CONFIG_DEBUG_INFO_DWARF5. Unfortunately, that will not fix
> > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT when DWARF5 is the default
> > > version...
> > 
> > I've been working on a series that will encode the default implicit
> > dwarf version based on compiler version check. Maybe that can be
> > extended/reused here once that lands?
> > https://lore.kernel.org/llvm/20220831184408.2778264-1-ndesaulniers@google.com/
> > Series needs revision, but it's on the right track.
> > 
> > > Alternatively, switching to llvm-objdump for clang builds
> > > would help :) I am not aware of any issues that would affect that switch
> > > for PowerPC:
> > > 
> > > https://github.com/ClangBuiltLinux/linux/labels/%5BTOOL%5D%20llvm-objdump
> > 
> > Oh, is 0day doing `make CC=clang` rather than `make LLVM=1`?  Rong,
> > any chance we get 0day folks to test LLVM=1 for more architectures?
> > Ideally we'd test both, preferably LLVM=1 if we had to choose.
> 
> Hi Nick,
> 
> Thanks for your advice, yes, we are doing `make CC=clang`, we'll plan it
> recently.

Hi Nick, add one question here, if we switch to LLVM=1, as not all old kernel
commits can support this option, do you suggest we only focus clang build on the kernel
that supports LLVM=1 or we need switch to CC=clang if LLVM is not supported?

> 
> Best Regards,
> Rong Chen
> 
> > 
> > > 
> > > Cheers,
> > > Nathan
> > 
> > 
> > 
> 

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