On Fri, Sep 17, 2021 at 8:00 PM Yonghong Song <yhs@xxxxxx> wrote: > > > > On 9/17/21 6:34 PM, Vincent Li wrote: > > Hi, > > > > I am supposed to file a bug report in https://bugs.llvm.org/ but the > > site requires account login, while waiting for my account setup, and > > since this is related to BPF, I will try my luck here :) > > > > This is cilium environment, when I use llvm-objdump to disassemble the > > bpf_lxc.o like below, it core dumps > > > > #llvm-objdump -S -D /var/run/cilium/state/2799/bpf_lxc.o > > > /home/bpf_lxc-5.4.txt > > Any particular reason you are using '-D' here? > > "llvm-objdump --help" gives: > > --disassemble-all Display assembler mnemonics for the machine > instructions > > --disassemble Display assembler mnemonics for the machine > instructions > > > -D Alias for --disassemble-all > > > -d Alias for --disassemble > > It gives the same description about -D and -d but actually -D tries to > disassemble *all* sections and -d tries to disassemble *only* executable > sections. > > The following is an example to disassemble a selftest bpf program > bpf_iter_tcp4.o: > > [yhs@devbig003.ftw2 ~/work/bpf-next/tools/testing/selftests/bpf] > llvm-objdump -D bpf_iter_tcp4.o >& ~/log > [yhs@devbig003.ftw2 ~/work/bpf-next/tools/testing/selftests/bpf] grep > "Disassembly of section" ~/log > Disassembly of section .strtab: > Disassembly of section iter/tcp: > Disassembly of section .reliter/tcp: > Disassembly of section license: > Disassembly of section .rodata: > Disassembly of section .debug_loc: > Disassembly of section .debug_abbrev: > Disassembly of section .debug_info: > Disassembly of section .rel.debug_info: > Disassembly of section .debug_ranges: > Disassembly of section .debug_str: > Disassembly of section .BTF: > Disassembly of section .rel.BTF: > Disassembly of section .BTF.ext: > Disassembly of section .rel.BTF.ext: > Disassembly of section .debug_frame: > Disassembly of section .rel.debug_frame: > Disassembly of section .debug_line: > Disassembly of section .rel.debug_line: > Disassembly of section .llvm_addrsig: > Disassembly of section .symtab: > [yhs@devbig003.ftw2 ~/work/bpf-next/tools/testing/selftests/bpf] > llvm-objdump -d bpf_iter_tcp4.o >& ~/log > [yhs@devbig003.ftw2 ~/work/bpf-next/tools/testing/selftests/bpf] grep > "Disassembly of section" ~/log > Disassembly of section iter/tcp: > [yhs@devbig003.ftw2 ~/work/bpf-next/tools/testing/selftests/bpf] > > You can see, "-D" tries to disassemble *all* sections and "-d" only > tries to disassemble "iter/tcp" section which is the *text* section. > > I suspect llvm BPF backend may have some loose end which didn't handle > well for illegal insn, which I will put up a task so we can fix it. > > I guess you tries to disassemble for non-text sections because you want > to compare contents of sections with text file? If this is the case, > you may want to compare section data directly, because disassemble > illegal insn will result in "<unknown>" insn which may hide the > actual data difference. In any case, it would be good to know what you > try to do with "-D" result so we may discuss to find a proper solution. > Yonghong, thank you for the detail explanation, it is me not clear about the usage of llvm-objdump, should have read the manual or try different argument before this post, thought better reporting the crash dump than doing nothing :) Vincent > > > > PLEASE submit a bug report to https://bugs.llvm.org/ and include the > > crash backtrace. > > > > Stack dump: > > > > 0. Program arguments: llvm-objdump -S -D /var/run/cilium/state/2799/bpf_lxc.o > > > > #0 0x00000000006336bc llvm::sys::PrintStackTrace(llvm::raw_ostream&, > > int) (/usr/local/bin/llvm-objdump+0x6336bc) > > > > #1 0x00000000006318a4 llvm::sys::RunSignalHandlers() > > (/usr/local/bin/llvm-objdump+0x6318a4) > > > > #2 0x0000000000631efd SignalHandler(int) (/usr/local/bin/llvm-objdump+0x631efd) > > > > #3 0x00007f9f39a7fb20 __restore_rt (/lib64/libpthread.so.0+0x12b20) > > > > #4 0x0000000000492e8b > > llvm::BPFInstPrinter::printMemOperand(llvm::MCInst const*, int, > > llvm::raw_ostream&, char const*) > > (/usr/local/bin/llvm-objdump+0x492e8b) > > > > #5 0x00000000004946c0 llvm::BPFInstPrinter::printInst(llvm::MCInst > > const*, unsigned long, llvm::StringRef, llvm::MCSubtargetInfo const&, > > llvm::raw_ostream&) (/usr/local/bin/llvm-objdump+0x4946c0) > > > > #6 0x0000000000432351 (anonymous > > namespace)::BPFPrettyPrinter::printInst(llvm::MCInstPrinter&, > > llvm::MCInst const*, llvm::ArrayRef<unsigned char>, > > llvm::object::SectionedAddress, llvm::formatted_raw_ostream&, > > llvm::StringRef, llvm::MCSubtargetInfo const&, (anonymous > > namespace)::SourcePrinter*, llvm::StringRef, > > std::vector<llvm::object::RelocationRef, > > std::allocator<llvm::object::RelocationRef> >*, (anonymous > > namespace)::LiveVariablePrinter&) > > (/usr/local/bin/llvm-objdump+0x432351) > > > > #7 0x00000000004400b8 disassembleObject(llvm::Target const*, > > llvm::object::ObjectFile const*, llvm::MCContext&, > > llvm::MCDisassembler*, llvm::MCDisassembler*, llvm::MCInstrAnalysis > > const*, llvm::MCInstPrinter*, llvm::MCSubtargetInfo const*, > > llvm::MCSubtargetInfo const*, (anonymous namespace)::PrettyPrinter&, > > (anonymous namespace)::SourcePrinter&, bool) > > (/usr/local/bin/llvm-objdump+0x4400b8) > > > > #8 0x000000000044444e disassembleObject(llvm::object::ObjectFile > > const*, bool) (/usr/local/bin/llvm-objdump+0x44444e) > > > > #9 0x00000000004454e2 dumpObject(llvm::object::ObjectFile*, > > llvm::object::Archive const*, llvm::object::Archive::Child const*) > > (/usr/local/bin/llvm-objdump+0x4454e2) > > > > #10 0x0000000000409910 main (/usr/local/bin/llvm-objdump+0x409910) > > > > #11 0x00007f9f3854c493 __libc_start_main (/lib64/libc.so.6+0x23493) > > > > #12 0x000000000042384e _start (/usr/local/bin/llvm-objdump+0x42384e) > > > > Segmentation fault (core dumped) > > > > I compiled and installed llvm and clang 12.0.1 myself > >
