Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210129194318.2125748-1-ndesaulniers@google.com>
 <20210129194318.2125748-3-ndesaulniers@google.com> <CA+icZUX4q-JhCo+UZ9T3FhbC_gso-oaB0OR9KdH5iEpoGZyqVw@mail.gmail.com>
 <CAKwvOdnj1Np62+eOiTOCRXSW6GLSv4hmvtWaz=0aTZEEot_dhw@mail.gmail.com>
 <CA+icZUWsyjDY58ZZ0MAVfWqBJ8FUSpM6=_5aqPcRTfX2W8Y-+Q@mail.gmail.com>
 <CAKwvOd=mHvEtto37rzFMfsFYe2e-Cp2MAiyRYxHWPdc-HbT8EA@mail.gmail.com>
 <CA+icZUWxK9fdV8PNGqbQrOFmSZ2Ts4nNqfVMMNUh5u79Ld7hjA@mail.gmail.com>
 <CA+icZUUo6URpxHh6_Tppv9_Z1dyhGDB2OqSCY3yRw72aA0EbMQ@mail.gmail.com>
 <CAKwvOdmWx0reabY-S3nXfTZuhs-_SP7pbb0uHyGeaNSQnm8eRQ@mail.gmail.com> <CA+icZUWsncyKvxPZ5g=a3ssWy=cYahsU6hprM3n=jFUmnjPC6w@mail.gmail.com>
In-Reply-To: <CA+icZUWsncyKvxPZ5g=a3ssWy=cYahsU6hprM3n=jFUmnjPC6w@mail.gmail.com>
From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Fri, 29 Jan 2021 14:20:51 -0800
Message-ID: <CAKwvOdk4kG-_c3inNj9ry_xUU9SQE-2AqQp40YL_V=6SHU6E=Q@mail.gmail.com>
Subject: Re: [PATCH v6 2/2] Kbuild: implement support for DWARF v5
To:     Sedat Dilek <sedat.dilek@gmail.com>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Jakub Jelinek <jakub@redhat.com>,
        Fangrui Song <maskray@google.com>,
        Caroline Tice <cmtice@google.com>,
        Nick Clifton <nickc@redhat.com>, Yonghong Song <yhs@fb.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Arvind Sankar <nivedita@alum.mit.edu>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Jan 29, 2021 at 2:11 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Fri, Jan 29, 2021 at 11:09 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > On Fri, Jan 29, 2021 at 1:20 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > >
> > > On Fri, Jan 29, 2021 at 10:13 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > > >
> > > > On Fri, Jan 29, 2021 at 10:09 PM Nick Desaulniers
> > > > <ndesaulniers@google.com> wrote:
> > > > >
> > > > > On Fri, Jan 29, 2021 at 12:55 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > > > > >
> > > > > > On Fri, Jan 29, 2021 at 9:48 PM Nick Desaulniers
> > > > > > <ndesaulniers@google.com> wrote:
> > > > > > >
> > > > > > > On Fri, Jan 29, 2021 at 12:41 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > > > > > > >
> > > > > > > > On Fri, Jan 29, 2021 at 8:43 PM Nick Desaulniers
> > > > > > > > <ndesaulniers@google.com> wrote:
> > > > > > > > >
> > > > > > > > > diff --git a/Makefile b/Makefile
> > > > > > > > > index 20141cd9319e..bed8b3b180b8 100644
> > > > > > > > > --- a/Makefile
> > > > > > > > > +++ b/Makefile
> > > > > > > > > @@ -832,8 +832,20 @@ endif
> > > > > > > > >
> > > > > > > > >  dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2
> > > > > > > > >  dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
> > > > > > > > > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5
> > > > > > > > >  DEBUG_CFLAGS   += -gdwarf-$(dwarf-version-y)
> > > > > > > > >
> > > > > > > > > +# If using clang without the integrated assembler, we need to explicitly tell
> > > > > > > > > +# GAS that we will be feeding it DWARF v5 assembler directives. Kconfig should
> > > > > > > > > +# detect whether the version of GAS supports DWARF v5.
> > > > > > > > > +ifdef CONFIG_CC_IS_CLANG
> > > > > > > > > +ifneq ($(LLVM_IAS),1)
> > > > > > > > > +ifeq ($(dwarf-version-y),5)
> > > > > > > > > +DEBUG_CFLAGS   += -Wa,-gdwarf-5
> > > > > > > >
> > > > > > > > I noticed double "-g -gdwarf-5 -g -gdwarf-5" (a different issue) and
> > > > > > > > that's why I looked again into the top-level Makefile.
> > > > > > >
> > > > > > > That's...unexpected.  I don't see where that could be coming from.
> > > > > > > Can you tell me please what is the precise command line invocation of
> > > > > > > make and which source file you observed this on so that I can
> > > > > > > reproduce?
> > > > > > >
> > > > > >
> > > > > > That's everywhere...
> > > > > >
> > > > > > $ zstdgrep --color '\-g -gdwarf-5 -g -gdwarf-5'
> > > > > > build-log_5.11.0-rc5-8-amd64-clang12-lto.txt.zst
> > > > > > | wc -l
> > > > > > 29529
> > > > >
> > > > > I'm not able to reproduce.
> > > > >
> > > > > $ make LLVM=1 -j72 V=1 2>&1 | grep dwarf
> > > > > ...
> > > > > clang ... -g -gdwarf-5 -Wa,-gdwarf-5 ...
> > > > > ...
> > > > >
> > > > > $ make LLVM=1 LLVM_IAS=1 -j72 V=1 2>&1 | grep dwarf
> > > > > ...
> > > > > clang ... -g -gdwarf-5 ...
> > > > > ...
> > > > >
> > > >
> > > > Hmm...
> > > >
> > > > I do not see in my current build "-Wa,-gdwarf-5" is passed with v6.
> > > >
> > > > $ grep '\-Wa,-gdwarf-5' build-log_5.11.0-rc5-10-amd64-clang12-lto-pgo.txt
> > > > [ empty ]
> > > >
> > >
> > > That's the diff v5 -> v6...
> > >
> > > There is no more a dwarf-aflag / KBUILD_AFLAGS += $(dwarf-aflag) used.
> >
> > Yep; not sure that's relevant though to duplicate flags?
> >
> > > > > Can you tell me please what is the precise command line invocation of
> > > > > make and which source file you observed this on so that I can
> > > > > reproduce?
> >
> > If you don't send me your invocation of `make`, I cannot help you.
> >
>
> /usr/bin/perf_5.10 stat make V=1 -j4 LLVM=1 LLVM_IAS=1
> PAHOLE=/opt/pahole/bin/pahole LOCALVERSION=-10-amd64-clang12
> -lto-pgo KBUILD_VERBOSE=1 KBUILD_BUILD_HOST=iniza
> KBUILD_BUILD_USER=sedat.dilek@gmail.com
> KBUILD_BUILD_TIMESTAMP=2021-01-29 bindeb-pkg
> KDEB_PKGVERSION=5.11.0~rc5-10~bullseye+dileks1

$ make LLVM=1 LLVM_IAS=1 -j72 defconfig
$ make LLVM=1 LLVM_IAS=1 -j72 menuconfig
<enable CONFIG_DEBUG_INFO and CONFIG_DEBUG_INFO_DWARF5>
$ make LLVM=1 LLVM_IAS=1 -j72 V=1 &> log.txt
$ grep '\-g -gdwarf-5 -g -gdwarf-5' log.txt | wc -l
0
$ grep '\-g -gdwarf-5' log.txt | wc -l
2517

Do have the patch applied twice, perhaps?

Is your compiler haunted, or is mine? (haha! they both are; false
dichotomy; they are one in the same).  Is zstdgrep haunted, or is GNU
grep haunted? :P
-- 
Thanks,
~Nick Desaulniers