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? - Sedat - [1] https://git.kernel.org/linus/3193c0836f203a91bef96d88c64cccf0be090d9c
