Arnaldo,
On Thu, Sep 14, 2023 at 06:37:17AM +0300, Vitaly Chikunov wrote:
> On Mon, Jul 10, 2023 at 11:00:02PM +0300, Vitaly Chikunov wrote:
> > On Mon, Jul 10, 2023 at 10:42:43AM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Wed, Jul 05, 2023 at 05:00:40AM +0300, Vitaly Chikunov escreveu:
> > > >
> > > > After updating Dwarves to v1.25 we are getting SIGSEGV while building
> > > > kernel on 32-bit x86 architecture. It looks like this:
> > >
> > > 128 cores, 32-bit system? Interesting :-)
> >
> > This is just AMD Zen in 32-bit personality.
>
> This started to reappear for v6.5 on armv7hf with 64 cores (Cortex-A72
> aarch64 which supports linux32 personality) even with your proposed
> patch. But with different error messages:
>
> BTF .btf.vmlinux.bin.o
> [24982] STRUCT super_block's field 's_bdev' offset=1120 bit_size=0 type=25296 Error emitting field
> Encountered error while encoding BTF.
> LD .tmp_vmlinux.kallsyms1
> NM .tmp_vmlinux.kallsyms1.syms
> KSYMS .tmp_vmlinux.kallsyms1.S
> AS .tmp_vmlinux.kallsyms1.S
> LD .tmp_vmlinux.kallsyms2
> NM .tmp_vmlinux.kallsyms2.syms
> KSYMS .tmp_vmlinux.kallsyms2.S
> AS .tmp_vmlinux.kallsyms2.S
> LD vmlinux
> BTFIDS vmlinux
> libbpf: failed to find '.BTF' ELF section in vmlinux
> FAILED: load BTF from vmlinux: No data available
>
> With V=1:
>
> + info BTF .btf.vmlinux.bin.o
> + printf ' %-7s %s\n' BTF .btf.vmlinux.bin.o
> BTF .btf.vmlinux.bin.o
> + LLVM_OBJCOPY=objcopy
> + pahole -J --btf_gen_floats -j --lang_exclude=rust --skip_encoding_btf_inconsistent_proto --btf_gen_optimized .tmp_vmlinux.btf
> [26109] STRUCT kiocb's field 'ki_waitq' offset=256 bit_size=0 type=26179 Error emitting field
> Encountered error while encoding BTF.
>
> Restricting -j to 32 helped, though.
FYI. This tuned out to be more weird than that. Adding -j32 causes arm32
to not boot in qemu properly with BPF errors (which I did not investigate
further, log below), -j16 with timeouts, so I resorted to just removing
-j for 32-bit architectures from `scripts/pahole-flags.sh`.
Test boot after build with pahole -j32:
[00:23:50] + timeout 300 vm-run uname -a
[00:23:52] + time qemu-system-aarch64-bundle -M accel=kvm:tcg -m 3072 -smp cores=6 -serial mon:stdio -nodefaults -nographic -no-reboot -fsdev local,id=root,path=/,security_model=none,multidevs=remap -device virtio-9p-pci,fsdev=root,mount_tag=virtio-9p:/ -device virtio-rng-pci -kernel /usr/src/tmp/kernel-image-un-def-buildroot/boot/vmlinuz-6.5.3-un-def-alt1 -initrd /usr/src/tmp/initramfs-6.5.3-un-def-alt1.img -sandbox on,spawn=deny -M virt,highmem=off -cpu host,aarch64=off -append 'console=ttyAMA0 mitigations=off nokaslr quiet panic=-1 SCRIPT=/usr/src/tmp/vm.eKPHAvWlYq watchdog_thresh=60'
[00:23:55] [ 0.240771] BPF: type_id=0 offset=2944 size=4864
[00:23:55] [ 0.242126] BPF:
[00:23:55] [ 0.242681] BPF: Invalid type_id
[00:23:55] [ 0.243557] BPF:
[00:23:55] init_module 'netfs.ko' Invalid argument
[00:23:55] init_module '9pnet.ko' Invalid argument
[00:23:55] init_module 'virtio.ko' Invalid argument
[00:23:55] init_module 'virtio_ring.ko' Invalid argument
[00:23:56] init_module 'virtio_pci_modern_dev.ko' Invalid argument
[00:23:56] init_module 'virtio_pci_legacy_dev.ko' Invalid argument
[00:23:56] glob: 9p mount_tag not found (ret: 3): No such file or directory
[00:23:56] rootfs not found.
[00:23:57] [ 2.000050] reboot: Power down
(qemu-system-aarch64-bundle is special qemu wrapper to run aarch64 qemu
on arm32 system - which actually is aarch64 with linux32 personality.)
Also in this build, there is 264 errors after `BTFIDS vmlinux` like
this:
[00:04:49] WARN: resolve_btfids: unresolved symbol udp6_sock
[00:04:49] WARN: resolve_btfids: unresolved symbol reuseport_array
[00:04:49] WARN: resolve_btfids: unresolved symbol bpf_ringbuf_map
[00:04:49] WARN: resolve_btfids: unresolved symbol vfs_truncate
[00:04:49] WARN: resolve_btfids: unresolved symbol tcp_slow_start
[00:04:49] WARN: resolve_btfids: unresolved symbol tcp_reno_undo_cwnd
[00:04:49] WARN: resolve_btfids: unresolved symbol tcp_reno_ssthresh
[00:04:49] WARN: resolve_btfids: unresolved symbol tcp_reno_cong_avoid
[00:04:49] WARN: resolve_btfids: unresolved symbol tcp_cong_avoid_ai
[00:04:49] WARN: resolve_btfids: unresolved symbol should_failslab
[00:04:49] WARN: resolve_btfids: unresolved symbol crash_kexec
[00:04:49] WARN: resolve_btfids: unresolved symbol bpf_sock_destroy
[00:04:49] WARN: resolve_btfids: unresolved symbol bpf_obj_new_impl
[00:04:49] WARN: resolve_btfids: unresolved symbol bpf_lsm_xfrm_state_pol_flow_match
[00:04:49] WARN: resolve_btfids: unresolved symbol bpf_lsm_xfrm_state_free_security
... &c.
With -j removed there is still errors like this but a lot less (7):
[00:04:36] WARN: resolve_btfids: unresolved symbol vfs_truncate
[00:04:36] WARN: resolve_btfids: unresolved symbol bpf_obj_new_impl
[00:04:36] WARN: resolve_btfids: unresolved symbol bpf_lsm_path_notify
[00:04:36] WARN: resolve_btfids: unresolved symbol bpf_lsm_kernel_post_load_data
[00:04:36] WARN: resolve_btfids: unresolved symbol bpf_lookup_user_key
[00:04:36] WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_xdp
[00:04:36] WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_skb
(There are no such errors on the i586 build.)
Thanks,
>
> Thanks,
>
>
>
> >
> > >
> > > > BTF .btf.vmlinux.bin.o
> > > > scripts/link-vmlinux.sh: line 111: 395728 Segmentation fault LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
> > > > LD .tmp_vmlinux.kallsyms1
> > > > NM .tmp_vmlinux.kallsyms1.syms
> > > > KSYMS .tmp_vmlinux.kallsyms1.S
> > > > AS .tmp_vmlinux.kallsyms1.S
> > > > LD .tmp_vmlinux.kallsyms2
> > > > NM .tmp_vmlinux.kallsyms2.syms
> > > > KSYMS .tmp_vmlinux.kallsyms2.S
> > > > AS .tmp_vmlinux.kallsyms2.S
> > > > LD vmlinux
> > > > BTFIDS vmlinux
> > > > libbpf: failed to find '.BTF' ELF section in vmlinux
> > > > FAILED: load BTF from vmlinux: No data available
> > > >
> > > > What crashes is this command:
> > > >
> > > > pahole -J --btf_gen_floats -j --lang_exclude=rust .tmp_vmlinux.btf
> > > >
> > > > I found that cause of the crash is that build box having 128 cores. By
> > > > experiment I found that with -j81 pahole works OK, but with -j82 or
> > > > greater it crashes.
> > > >
> > > > $ gdb -q --args pahole -J --btf_gen_floats -j111 --lang_exclude=rust .tmp_vmlinux.btf
> > > > Thread 15 "pahole" received signal SIGSEGV, Segmentation fault.
> > > > [Switching to Thread 0xda5ffb40 (LWP 3102466)]
> > > > 0xf7f3c944 in btf_encoder__btf (encoder=0x0) at /usr/src/debug/dwarves-1.25/btf_encoder.c:1890
> > > > 1890 return encoder->btf;
> > > > (gdb) bt
> > > > #0 0xf7f3c944 in btf_encoder__btf (encoder=0x0) at /usr/src/debug/dwarves-1.25/btf_encoder.c:1890
> > > > #1 0x5655c25d in pahole_stealer (cu=0xd9a01f80, conf_load=0x565640c0 <conf_load>, thr_data=0x56567c18) at /usr/src/debug/dwarves-1.25/pahole.c:3100
> > > > #2 0xf7f452d7 in cu__finalize (cu=cu@entry=0xd9a01f80, conf=0x565640c0 <conf_load>, thr_data=thr_data@entry=0x56567c18)
> > > > at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3001
> > > > #3 0xf7f4541d in cus__finalize (thr_data=0x56567c18, conf=<optimized out>, cu=0xd9a01f80, cus=0x565651c0) at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3008
> > > > #4 dwarf_cus__create_and_process_cu (dcus=dcus@entry=0xffffd19c, cu_die=cu_die@entry=0xda5ff38c, pointer_size=<optimized out>, thr_data=0x56567c18)
> > > > at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3207
> > > > #5 0xf7f461af in dwarf_cus__process_cu_thread (arg=0xffffcbf8) at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3250
> > > > #6 0xf7db4258 in start_thread (arg=<optimized out>) at pthread_create.c:444
> > > > #7 0xf7e3a878 in clone3 () from /lib/libc.so.6
> > > > (gdb) p encoder
> > > > $1 = (struct btf_encoder *) 0x0
> > > > (gdb) f 1
> > > > #1 0x5655c25d in pahole_stealer (cu=0xd9a01f80, conf_load=0x565640c0 <conf_load>, thr_data=0x56567c18) at /usr/src/debug/dwarves-1.25/pahole.c:3100
> > > > 3100 thread->btf = btf_encoder__btf(thread->encoder);
> > > > (gdb) list -2
> > > > 3093 thread->encoder =
> > > > 3094 btf_encoder__new(cu, detached_btf_filename,
> > > > 3095 NULL,
> > > > 3096 skip_encoding_btf_vars,
> > > > 3097 btf_encode_force,
> > > > 3098 btf_gen_floats,
> > > > 3099 global_verbose);
> > > > 3100 thread->btf = btf_encoder__btf(thread->encoder);
> > > > 3101 }
> > > > 3102 encoder = thread->encoder;
> > > >
> > > > I think that return value of btf_encoder__new is not checked. But did
> > > > not investigate further why is this happening. It would be great to have
> > > > this fixed.
> > >
> > > Can you try with this minimal patch? Maybe we can with some more work
> > > auto-limit the number of threads or make the threads without a
> > > btf_encoder be processed at the end, reusing the main btf_encoder, but
> > > this first patch would at least help diagnosing the problem more
> > > quickly.
> >
> > With this patch applied and run on 20 core:
> >
> > builder@i586:kernel-source-6.3$ pahole -J --btf_gen_floats -j111 --lang_exclude=rust .tmp_vmlinux.btf
> > Not enough memory to instantiate new BTF encoder.
> > HINT: Maybe reduce the -j/--jobs command line value?.
> > ... 40 times this message ....
> > Not enough memory to instantiate new BTF encoder.
> > HINT: Maybe reduce the -j/--jobs command line value?.
> > builder@i586:kernel-source-6.3$ echo $?
> > 0
> >
> > Thanks,
> >
> > >
> > > - Arnaldo
> > >
> > > diff --git a/pahole.c b/pahole.c
> > > index e843999fde2a8a37..887b3403dcff18c0 100644
> > > --- a/pahole.c
> > > +++ b/pahole.c
> > > @@ -3097,6 +3097,15 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
> > > btf_encode_force,
> > > btf_gen_floats,
> > > global_verbose);
> > > + if (thread->encoder == NULL) {
> > > + fprintf(stderr, "Not enough memory to instantiate new BTF encoder.\n");
> > > +
> > > + if (conf_load->nr_jobs > 1)
> > > + fprintf(stderr, "HINT: Maybe reduce the -j/--jobs command line value?.\n");
> > > +
> > > + ret = LSK__STOP_LOADING;
> > > + goto out_btf;
> > > + }
> > > thread->btf = btf_encoder__btf(thread->encoder);
> > > }
> > > encoder = thread->encoder;
