On Sat, Jul 27, 2019 at 7:08 PM Yonghong Song <yhs@xxxxxx> wrote: > > > > On 7/27/19 12:36 AM, Sedat Dilek wrote: > > On Sat, Jul 27, 2019 at 4:24 AM Alexei Starovoitov > > <alexei.starovoitov@xxxxxxxxx> wrote: > >> > >> On Fri, Jul 26, 2019 at 2:19 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > >>> > >>> On Fri, Jul 26, 2019 at 11:10 PM Yonghong Song <yhs@xxxxxx> wrote: > >>>> > >>>> > >>>> > >>>> On 7/26/19 2:02 PM, Sedat Dilek wrote: > >>>>> On Fri, Jul 26, 2019 at 10:38 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > >>>>>> > >>>>>> Hi Yonghong Song, > >>>>>> > >>>>>> On Fri, Jul 26, 2019 at 5:45 PM Yonghong Song <yhs@xxxxxx> wrote: > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> On 7/26/19 1:26 AM, Sedat Dilek wrote: > >>>>>>>> Hi, > >>>>>>>> > >>>>>>>> I have opened a new issue in the ClangBuiltLinux issue tracker. > >>>>>>> > >>>>>>> Glad to know clang 9 has asm goto support and now It can compile > >>>>>>> kernel again. > >>>>>>> > >>>>>> > >>>>>> Yupp. > >>>>>> > >>>>>>>> > >>>>>>>> I am seeing a problem in the area bpf/seccomp causing > >>>>>>>> systemd/journald/udevd services to fail. > >>>>>>>> > >>>>>>>> [Fri Jul 26 08:08:43 2019] systemd[453]: systemd-udevd.service: Failed > >>>>>>>> to connect stdout to the journal socket, ignoring: Connection refused > >>>>>>>> > >>>>>>>> This happens when I use the (LLVM) LLD ld.lld-9 linker but not with > >>>>>>>> BFD linker ld.bfd on Debian/buster AMD64. > >>>>>>>> In both cases I use clang-9 (prerelease). > >>>>>>> > >>>>>>> Looks like it is a lld bug. > >>>>>>> > >>>>>>> I see the stack trace has __bpf_prog_run32() which is used by > >>>>>>> kernel bpf interpreter. Could you try to enable bpf jit > >>>>>>> sysctl net.core.bpf_jit_enable = 1 > >>>>>>> If this passed, it will prove it is interpreter related. > >>>>>>> > >>>>>> > >>>>>> After... > >>>>>> > >>>>>> sysctl -w net.core.bpf_jit_enable=1 > >>>>>> > >>>>>> I can start all failed systemd services. > >>>>>> > >>>>>> systemd-journald.service > >>>>>> systemd-udevd.service > >>>>>> haveged.service > >>>>>> > >>>>>> This is in maintenance mode. > >>>>>> > >>>>>> What is next: Do set a permanent sysctl setting for net.core.bpf_jit_enable? > >>>>>> > >>>>> > >>>>> This is what I did: > >>>> > >>>> I probably won't have cycles to debug this potential lld issue. > >>>> Maybe you already did, I suggest you put enough reproducible > >>>> details in the bug you filed against lld so they can take a look. > >>>> > >>> > >>> I understand and will put the journalctl-log into the CBL issue > >>> tracker and update informations. > >>> > >>> Thanks for your help understanding the BPF correlations. > >>> > >>> Is setting 'net.core.bpf_jit_enable = 2' helpful here? > >> > >> jit_enable=1 is enough. > >> Or use CONFIG_BPF_JIT_ALWAYS_ON to workaround. > >> > >> It sounds like clang miscompiles interpreter. > >> modprobe test_bpf > >> should be able to point out which part of interpreter is broken. > > > > Maybe we need something like... > > > > "bpf: Disable GCC -fgcse optimization for ___bpf_prog_run()" > > > > ...for clang? > > Not sure how do you get conclusion it is gcse causing the problem. > But anyway, adding such flag in the kernel is not a good idea. > clang/llvm should be fixed instead. Esp. there is still time > for 9.0.0 release to fix bugs. > To clarify: This is a snapshot release of clang-9 built with tc-build. Building with -O0 is not possible as I see asm-goto failing. - Sedat - [1] https://github.com/ClangBuiltLinux/tc-build > > > > - Sedat - > > > > [1] https://git.kernel.org/linus/3193c0836f203a91bef96d88c64cccf0be090d9c > >
