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From:   Ian Rogers <irogers@google.com>
Date:   Wed, 26 Jul 2023 21:20:33 -0700
Message-ID: <CAP-5=fX2ar7Pfj9it8pX_ohgC7OzY59iuDFSQTY7Kcnkc3-S5g@mail.gmail.com>
Subject: Re: [perf] Build error when using LTO on 6.4
To:     Bagas Sanjaya <bagasdotme@gmail.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        John Garry <john.g.garry@oracle.com>,
        Marcus Seyfarth <m.seyfarth@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Regressions <regressions@lists.linux.dev>,
        Linux Perf <linux-perf-users@vger.kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>
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On Wed, Jul 26, 2023 at 8:55=E2=80=AFPM Bagas Sanjaya <bagasdotme@gmail.com=
> wrote:
>
> Hi,
>
> I notice a build regression on Bugzilla [1]. Quoting from it:
>
> > Starting with Kernel 6.4, I see a build error when using "-flto" to bui=
ld perf. This used to work fine with earlier Kernels when using either bfd =
or mold as linker when using GCC 13.1.1.

Hmm.. strange I've never seen this work with GCC.

> >
> > This is the PKGBUILD I use as my build recipe: https://github.com/ms178=
/archpkgbuilds/blob/main/packages/bpf/PKGBUILD

If this binary is for distribution BUILD_BPF_SKEL=3D1 should be set. We
need to make this an opt-out rather than opt-in. The last time we did
this there was some friction:
https://lore.kernel.org/lkml/CAHk-=3DwjY_3cBELRSLMpqCt6Eb71Qei2agfKSNsrr5Kc=
pdEQCaA@mail.gmail.com/

> >
> > This is the konsole output I get now with Kernel 6.4.5:
> >
> > [CODE]
> > CFLAGS=3D'-Wno-error=3Dbad-function-cast -Wno-error=3Ddeclaration-after=
-statement -Wno-error=3Dswitch-enum -Wbad-function-cast -Wdeclaration-after=
-statement -Wformat-security -Wformat-y2k -Winit-self -Wmissing-declaration=
s -Wmissing-prototypes -Wno-system-headers -Wold-style-definition -Wpacked =
-Wredundant-decls -Wstrict-prototypes -Wswitch-default -Wswitch-enum -Wunde=
f -Wwrite-strings -Wformat -Wno-type-limits -Wstrict-aliasing=3D3 -Wshadow =
-DHAVE_SYSCALL_TABLE_SUPPORT -DHAVE_ARCH_X86_64_SUPPORT -Iarch/x86/include/=
generated -DHAVE_PERF_REGS_SUPPORT -DHAVE_ARCH_REGS_QUERY_REGISTER_OFFSET -=
Werror -DNDEBUG=3D1 -O6 -fno-omit-frame-pointer -ggdb3 -funwind-tables -Wal=
l -Wextra -std=3Dgnu11 -fstack-protector-all -U_FORTIFY_SOURCE -D_FORTIFY_S=
OURCE=3D2 -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=3D64 -D_GNU_SOURCE -I/t=
mp/makepkg/linux-tools/src/linux/tools/perf/util/include -I/tmp/makepkg/lin=
ux-tools/src/linux/tools/perf/arch/x86/include -I/tmp/makepkg/linux-tools/s=
rc/linux/tools/include/ -I/tmp/makepkg/linux-tools/src/linux/tools/arch/x86=
/include/uapi -I/tmp/makepkg/linux-tools/src/linux/tools/include/uapi -I/tm=
p/makepkg/linux-tools/src/linux/tools/arch/x86/include/ -I/tmp/makepkg/linu=
x-tools/src/linux/tools/arch/x86/ -I/tmp/makepkg/linux-tools/src/linux/tool=
s/perf/util -I/tmp/makepkg/linux-tools/src/linux/tools/perf -DHAVE_PTHREAD_=
ATTR_SETAFFINITY_NP -DHAVE_PTHREAD_BARRIER -DHAVE_EVENTFD_SUPPORT -DHAVE_GE=
T_CURRENT_DIR_NAME -DHAVE_GETTID -DHAVE_FILE_HANDLE -DHAVE_DWARF_GETLOCATIO=
NS_SUPPORT -DHAVE_AIO_SUPPORT -DHAVE_SCANDIRAT_SUPPORT -DHAVE_SCHED_GETCPU_=
SUPPORT -DHAVE_SETNS_SUPPORT -DHAVE_LIBELF_SUPPORT -DHAVE_ELF_GETPHDRNUM_SU=
PPORT -DHAVE_GELF_GETNOTE_SUPPORT -DHAVE_ELF_GETSHDRSTRNDX_SUPPORT -DHAVE_D=
EBUGINFOD_SUPPORT -DHAVE_DWARF_SUPPORT  -DHAVE_LIBBPF_SUPPORT -DHAVE_BPF_PR=
OLOGUE -DHAVE_JITDUMP -DHAVE_DWARF_UNWIND_SUPPORT -DNO_LIBUNWIND_DEBUG_FRAM=
E -DHAVE_LIBUNWIND_SUPPORT -DHAVE_LIBCRYPTO_SUPPORT -DHAVE_SLANG_SUPPORT -D=
NO_LIBPERL -DHAVE_TIMERFD_SUPPORT -DHAVE_LIBPYTHON_SUPPORT -DHAVE_CXA_DEMAN=
GLE_SUPPORT -DHAVE_ZLIB_SUPPORT -DHAVE_LZMA_SUPPORT -DHAVE_ZSTD_SUPPORT -DH=
AVE_LIBCAP_SUPPORT -DHAVE_BACKTRACE_SUPPORT -DHAVE_LIBNUMA_SUPPORT -DHAVE_K=
VM_STAT_SUPPORT -DDISASM_FOUR_ARGS_SIGNATURE -DDISASM_INIT_STYLED -DHAVE_PE=
RF_READ_VDSO32 -DHAVE_AUXTRACE_SUPPORT -DHAVE_LIBTRACEEVENT -DLIBTRACEEVENT=
_VERSION=3D66813 -I/tmp/makepkg/linux-tools/src/linux/tools/perf/libapi/inc=
lude -I/tmp/makepkg/linux-tools/src/linux/tools/perf/libbpf/include -I/tmp/=
makepkg/linux-tools/src/linux/tools/perf/libsubcmd/include -I/tmp/makepkg/l=
inux-tools/src/linux/tools/perf/libsymbol/include -I/tmp/makepkg/linux-tool=
s/src/linux/tools/perf/libperf/include' LDFLAGS=3D'-Wl,-O3,--as-needed,-Bsy=
mbolic-functions,--sort-common,-flto=3Dauto -fopenmp -fuse-ld=3Dmold -march=
=3Dnative -mtune=3Dnative -maes -mbmi2 -mpclmul -Wl,-zmax-page-size=3D0x200=
000 -Wl,-z,noexecstack  -lunwind-x86_64 -lunwind -llzma  -L/usr/lib ' \
> >   '/usr/bin/python' util/setup.py \
> >   --quiet build_ext; \
> > cp python_ext_build/lib/perf*.so python/
> > rm -f -f /tmp/makepkg/linux-tools/src/linux/tools/perf/libbpf/libbpf.a;=
 ar rcs /tmp/makepkg/linux-tools/src/linux/tools/perf/libbpf/libbpf.a /tmp/=
makepkg/linux-tools/src/linux/tools/perf/libbpf/staticobjs/libbpf-in.o
> > [snip]
> > gcc -Wno-error=3Dbad-function-cast -Wno-error=3Ddeclaration-after-state=
ment -Wno-error=3Dswitch-enum -Wbad-function-cast -Wdeclaration-after-state=
ment -Wformat-security -Wformat-y2k -Winit-self -Wmissing-declarations -Wmi=
ssing-prototypes -Wno-system-headers -Wold-style-definition -Wpacked -Wredu=
ndant-decls -Wstrict-prototypes -Wswitch-default -Wswitch-enum -Wundef -Wwr=
ite-strings -Wformat -Wno-type-limits -Wstrict-aliasing=3D3 -Wshadow -DHAVE=
_SYSCALL_TABLE_SUPPORT -DHAVE_ARCH_X86_64_SUPPORT -Iarch/x86/include/genera=
ted -DHAVE_PERF_REGS_SUPPORT -DHAVE_ARCH_REGS_QUERY_REGISTER_OFFSET -Werror=
 -DNDEBUG=3D1 -O6 -fno-omit-frame-pointer -ggdb3 -funwind-tables -Wall -Wex=
tra -std=3Dgnu11 -fstack-protector-all -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=
=3D2 -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=3D64 -D_GNU_SOURCE -I/tmp/ma=
kepkg/linux-tools/src/linux/tools/perf/util/include -I/tmp/makepkg/linux-to=
ols/src/linux/tools/perf/arch/x86/include -I/tmp/makepkg/linux-tools/src/li=
nux/tools/include/ -I/tmp/makepkg/linux-tools/src/linux/tools/arch/x86/incl=
ude/uapi -I/tmp/makepkg/linux-tools/src/linux/tools/include/uapi -I/tmp/mak=
epkg/linux-tools/src/linux/tools/arch/x86/include/ -I/tmp/makepkg/linux-too=
ls/src/linux/tools/arch/x86/ -I/tmp/makepkg/linux-tools/src/linux/tools/per=
f/util -I/tmp/makepkg/linux-tools/src/linux/tools/perf -DHAVE_PTHREAD_ATTR_=
SETAFFINITY_NP -DHAVE_PTHREAD_BARRIER -DHAVE_EVENTFD_SUPPORT -DHAVE_GET_CUR=
RENT_DIR_NAME -DHAVE_GETTID -DHAVE_FILE_HANDLE -DHAVE_DWARF_GETLOCATIONS_SU=
PPORT -DHAVE_AIO_SUPPORT -DHAVE_SCANDIRAT_SUPPORT -DHAVE_SCHED_GETCPU_SUPPO=
RT -DHAVE_SETNS_SUPPORT -DHAVE_LIBELF_SUPPORT -DHAVE_ELF_GETPHDRNUM_SUPPORT=
 -DHAVE_GELF_GETNOTE_SUPPORT -DHAVE_ELF_GETSHDRSTRNDX_SUPPORT -DHAVE_DEBUGI=
NFOD_SUPPORT -DHAVE_DWARF_SUPPORT  -DHAVE_LIBBPF_SUPPORT -DHAVE_BPF_PROLOGU=
E -DHAVE_JITDUMP -DHAVE_DWARF_UNWIND_SUPPORT -DNO_LIBUNWIND_DEBUG_FRAME -DH=
AVE_LIBUNWIND_SUPPORT -DHAVE_LIBCRYPTO_SUPPORT -DHAVE_SLANG_SUPPORT -DNO_LI=
BPERL -DHAVE_TIMERFD_SUPPORT -DHAVE_LIBPYTHON_SUPPORT -DHAVE_CXA_DEMANGLE_S=
UPPORT -DHAVE_ZLIB_SUPPORT -DHAVE_LZMA_SUPPORT -DHAVE_ZSTD_SUPPORT -DHAVE_L=
IBCAP_SUPPORT -DHAVE_BACKTRACE_SUPPORT -DHAVE_LIBNUMA_SUPPORT -DHAVE_KVM_ST=
AT_SUPPORT -DDISASM_FOUR_ARGS_SIGNATURE -DDISASM_INIT_STYLED -DHAVE_PERF_RE=
AD_VDSO32 -DHAVE_AUXTRACE_SUPPORT -DHAVE_LIBTRACEEVENT -DLIBTRACEEVENT_VERS=
ION=3D66813 -I/tmp/makepkg/linux-tools/src/linux/tools/perf/libapi/include =
-I/tmp/makepkg/linux-tools/src/linux/tools/perf/libbpf/include -I/tmp/makep=
kg/linux-tools/src/linux/tools/perf/libsubcmd/include -I/tmp/makepkg/linux-=
tools/src/linux/tools/perf/libsymbol/include -I/tmp/makepkg/linux-tools/src=
/linux/tools/perf/libperf/include -Wl,-O3,--as-needed,-Bsymbolic-functions,=
--sort-common,-flto=3Dauto -fopenmp -fuse-ld=3Dmold -march=3Dnative -mtune=
=3Dnative -maes -mbmi2 -mpclmul -Wl,-zmax-page-size=3D0x200000 -Wl,-z,noexe=
cstack  -lunwind-x86_64 -lunwind -llzma  -L/usr/lib  \
> >         perf-in.o pmu-events/pmu-events-in.o -Wl,--whole-archive /tmp/m=
akepkg/linux-tools/src/linux/tools/perf/libapi/libapi.a /tmp/makepkg/linux-=
tools/src/linux/tools/perf/libperf/libperf.a /tmp/makepkg/linux-tools/src/l=
inux/tools/perf/libsubcmd/libsubcmd.a /tmp/makepkg/linux-tools/src/linux/to=
ols/perf/libsymbol/libsymbol.a /tmp/makepkg/linux-tools/src/linux/tools/per=
f/libbpf/libbpf.a  -Wl,--no-whole-archive -Wl,--start-group -lpthread -lrt =
-lm -ldl -lelf -ldebuginfod -ldw -lunwind-x86_64 -lunwind -llzma -lcrypto -=
lslang -lpython3.11 -ldl -lm -lutil -lstdc++ -lz -llzma -lzstd -lcap -lnuma=
 -ltraceevent -Wl,--end-group -o perf
> > mold: error: undefined symbol: main
>
> >>>> referenced by /usr/lib/Scrt1.o:(.text)
> >>>>               /usr/lib/Scrt1.o:(_start)
> > mold: error: undefined symbol: perf_pmu__getcpuid
> >>>> referenced by pmu-events.c
> >>>>               pmu-events/pmu-events-in.o:(perf_pmu__find_events_tabl=
e)>>>
> >>>>               referenced by pmu-events.c
> >>>>               pmu-events/pmu-events-in.o:(perf_pmu__find_metrics_tab=
le)
> > mold: error: undefined symbol: strcmp_cpuid_str
> >>>> referenced by pmu-events.c
> >>>>               pmu-events/pmu-events-in.o:(perf_pmu__find_events_tabl=
e)>>>
> >>>>               referenced by pmu-events.c
> >>>>               pmu-events/pmu-events-in.o:(perf_pmu__find_metrics_tab=
le)>>>
> >>>>               referenced by pmu-events.c
> >>>>               pmu-events/pmu-events-in.o:(find_core_events_table)>>>
> >>>>               referenced 1 more times
> >
> > mold: error: undefined symbol: _ctype
> >>>> referenced by kallsyms.c
> >>>>
> >>>>               /tmp/makepkg/linux-tools/src/linux/tools/perf/libsymbo=
l/libsymbol.a(libsymbol-in.o):(__tolower)>>>
> >>>>               referenced by kallsyms.c
> >>>>
> >>>>               /tmp/makepkg/linux-tools/src/linux/tools/perf/libsymbo=
l/libsymbol.a(libsymbol-in.o):(__toupper)
> > mold: error: undefined symbol: strlcpy
> >>>> referenced by exec-cmd.c
> >>>>
> >>>>               /tmp/makepkg/linux-tools/src/linux/tools/perf/libsubcm=
d/libsubcmd.a(libsubcmd-in.o):(get_pwd_cwd)
> > [/CODE]
> >
> > I have noticed a patch series of Ian Rodgers that might adress this iss=
ue, but his reported errors were different to mine, see: https://www.spinic=
s.net/lists/kernel/msg4872566.html
> >
> > Compiler: gcc-version 13.1.1 20230714 (GCC)
>
> See Bugzilla for the full thread.
>
> Anyway, I'm adding this regression to regzbot:
>
> #regzbot introduced: v6.3..v6.4.5 https://bugzilla.kernel.org/show_bug.cg=
i?id=3D217706

Thanks, I'm not sure there is anything actionable for the bug.
clang/llvm has always worked with LTO at Google. With my changes gcc
works for me with some non-zero effort.

Thanks,
Ian

> Thanks.
>
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=3D217706
>
> --
> An old man doll... just what I always wanted! - Clara