Re: runqslower build failed on Debian9

Re: runqslower build failed on Debian9

[Andrii Nakryiko]

On 3/25/20 10:26 PM, Liu Yiding wrote:
> Hi, Andrii.
> 
> I noticed you had added runqslower tool to tools/bpf, so drop this 
> problem to you.
> 
> 
> Now i failed to run bpf tests since i can't build runqslower.
> 
> Testing env: "Debian GNU/Linux 9 (stretch)"
> 
> kernel: 5.6.0-rc5
> 
> gcc: gcc 6.3
> 
> clang: clang-11.
> 
> 
> Description: Build runqslower failed due to build error "incomplete 
> type" and libbpf show unsupported BTF_KIND:7.
> 
> Whole build log please see the attatchment.
> 
> 
> Error info
> 
> ```
> 
> root@vm-snb-144 ~/linus/tools/bpf# make
> 
> Auto-detecting system features:
> ...                        libbfd: [ on  ]
> ...        disassembler-four-args: [ OFF ]
> 
> [snip]
> 
>    INSTALL  bpftool
>    LINK     bpf_asm
>    GEN      vmlinux.h
> libbpf: unsupported BTF_KIND:7    (Many unsupported errors)
> libbpf: unsupported BTF_KIND:7
> libbpf: unsupported BTF_KIND:7
> 

Would you be able to share BTF of vmlinux that is used to generate 
vmlinux.h? Please run in verbose mode: `make V=1` and search for 
`bpftool btf dump file` command. It should point either to
/sys/kernel/btf/vmlinux or some other location, depending on how things 
are set up on your side.

If it's /sys/kernel/btf/vmlinux, you can just `cat 
/sys/kernel/btf/vmlinux > my_btf.bin`. If it's some other file, easiest 
would be to just share that file. If not, it's possible to extract .BTF 
ELF section, let me know if you need help with that.


> [snip]
> 
> (Many incomplete type errors)
> 
> .output/vmlinux.h:8401:18: error: field has incomplete type 'struct 
> idt_bits'
>          struct idt_bits bits;
>                          ^
> .output/vmlinux.h:8396:8: note: forward declaration of 'struct idt_bits'
> struct idt_bits;
>         ^
> .output/vmlinux.h:8598:21: error: field has incomplete type 'struct 
> trace_entry'
>          struct trace_entry ent;
>                             ^
> .output/vmlinux.h:8595:8: note: forward declaration of 'struct trace_entry'
> struct trace_entry;
>         ^
> .output/vmlinux.h:9006:25: error: array has incomplete element type 
> 'struct cyc2ns_data'
>          struct cyc2ns_data data[2];
>                                 ^
> .output/vmlinux.h:3669:8: note: forward declaration of 'struct cyc2ns_data'
> struct cyc2ns_data;
>         ^
> fatal error: too many errors emitted, stopping now [-ferror-limit=]
> 20 errors generated.
> Makefile:56: recipe for target '.output/runqslower.bpf.o' failed
> make[1]: *** [.output/runqslower.bpf.o] Error 1
> Makefile:119: recipe for target 'runqslower' failed
> make: *** [runqslower] Error 2
> 
> ```
> 
> 

Re: runqslower build failed on Debian9

[Liu Yiding]

Something wrong with my smtp and this email missed.

Send again.


On 3/27/20 11:09 AM, Liu Yiding wrote:
> Hi, Andrii.
>
> Thanks for your prompt reply!
>
> Please check attatchment for my_btf.bin.
>
>
> On 3/27/20 4:28 AM, Andrii Nakryiko wrote:
>> Would you be able to share BTF of vmlinux that is used to generate 
>> vmlinux.h? Please run in verbose mode: `make V=1` and search for 
>> `bpftool btf dump file` command. It should point either to
>> /sys/kernel/btf/vmlinux or some other location, depending on how 
>> things are set up on your side.
>>
>> If it's /sys/kernel/btf/vmlinux, you can just `cat 
>> /sys/kernel/btf/vmlinux > my_btf.bin`. If it's some other file, 
>> easiest would be to just share that file. If not, it's possible to 
>> extract .BTF ELF section, let me know if you need help with that. 
>
-- 
Best Regards.
Liu Yiding

Re: runqslower build failed on Debian9

[Andrii Nakryiko]

On 3/29/20 5:48 PM, Liu Yiding wrote:
> Add attachment.
> 

Your BTF seems to be invalid. It has struct perf_ibs, which has a first 
field `struct pmu pmu` field with valid-looking size of 296 bytes, 
**but** the type that field points to is not a complete `struct pmu` 
definition, but rather just forward declaration. The way it is it 
shouldn't be even compilable, because forward declaration of a struct 
doesn't specify the size of a struct, so compiler should have rejected 
it. So it must be that either DWARF generated by compiler isn't correct, 
or there is DWARF -> BTF conversion bug somewhere. Are you using any 
special DWARF Kconfig settings? Maybe you can share your full .config 
and I might try to repro it on my machine.

But either way, that warning you get is a valid one, it should be 
illegal to have non-pointer forward-declared struct as a type for a 
struct member.

> 
> On 3/30/20 8:46 AM, Liu Yiding wrote:
>> Something wrong with my smtp and this email missed.
>>
>> Send again.
>>
>>
>> On 3/27/20 11:09 AM, Liu Yiding wrote:
>>> Hi, Andrii.
>>>
>>> Thanks for your prompt reply!
>>>
>>> Please check attatchment for my_btf.bin.
>>>
>>>
>>> On 3/27/20 4:28 AM, Andrii Nakryiko wrote:
>>>> Would you be able to share BTF of vmlinux that is used to generate 
>>>> vmlinux.h? Please run in verbose mode: `make V=1` and search for 
>>>> `bpftool btf dump file` command. It should point either to
>>>> /sys/kernel/btf/vmlinux or some other location, depending on how 
>>>> things are set up on your side.
>>>>
>>>> If it's /sys/kernel/btf/vmlinux, you can just `cat 
>>>> /sys/kernel/btf/vmlinux > my_btf.bin`. If it's some other file, 
>>>> easiest would be to just share that file. If not, it's possible to 
>>>> extract .BTF ELF section, let me know if you need help with that. 
>>>

Re: runqslower build failed on Debian9

[Andrii Nakryiko]

On Mon, Mar 30, 2020 at 5:19 PM Liu Yiding <liuyd.fnst@cn.fujitsu.com> wrote:
>
>
> On 3/30/20 2:09 PM, Andrii Nakryiko wrote:
> > On 3/29/20 5:48 PM, Liu Yiding wrote:
> >> Add attachment.
> >>
> >
> > Your BTF seems to be invalid. It has struct perf_ibs, which has a
> > first field `struct pmu pmu` field with valid-looking size of 296
> > bytes, **but** the type that field points to is not a complete `struct
> > pmu` definition, but rather just forward declaration. The way it is it
> > shouldn't be even compilable, because forward declaration of a struct
> > doesn't specify the size of a struct, so compiler should have rejected
> > it. So it must be that either DWARF generated by compiler isn't
> > correct, or there is DWARF -> BTF conversion bug somewhere. Are you
> > using any special DWARF Kconfig settings? Maybe you can share your
> > full .config and I might try to repro it on my machine.
> >
>
>  >> Are you using any special DWARF Kconfig settings?
>
> Sorry, i'm a newbie at this. I don't know which settings are related to
> DWARF.
>
> Just search keywords.
>
> ```
>
> liuyd@localhost:~$ cat config-5.6.0-rc5 | grep DWARF
> # CONFIG_DEBUG_INFO_DWARF4 is not set
>
> ```
>
> I built attached config on a clear ubuntu machine. Error could be
> reproduced. So you are right, there is a conflict between kconfigs.
>
>
>  >> Maybe you can share your full .config and I might try to repro it on
> my machine.
>
> Thanks a lot. I attached the broken config.

Thanks a lot! I think it's due to DEBUG_INFO_REDUCED which produces
not entirely correct DWARF. I'm asking Slava to disable this config
when BTF is requested in [0].

  [0] https://lore.kernel.org/bpf/CAEf4BzadnfAwfa1D0jZb=01Ou783GpK_U7PAYeEJca-L9kdnVA@mail.gmail.com


>
>
> > But either way, that warning you get is a valid one, it should be
> > illegal to have non-pointer forward-declared struct as a type for a
> > struct member.
> >
> >>
> >> On 3/30/20 8:46 AM, Liu Yiding wrote:
> >>> Something wrong with my smtp and this email missed.
> >>>
> >>> Send again.
> >>>
> >>>
> >>> On 3/27/20 11:09 AM, Liu Yiding wrote:
> >>>> Hi, Andrii.
> >>>>
> >>>> Thanks for your prompt reply!
> >>>>
> >>>> Please check attatchment for my_btf.bin.
> >>>>
> >>>>
> >>>> On 3/27/20 4:28 AM, Andrii Nakryiko wrote:
> >>>>> Would you be able to share BTF of vmlinux that is used to generate
> >>>>> vmlinux.h? Please run in verbose mode: `make V=1` and search for
> >>>>> `bpftool btf dump file` command. It should point either to
> >>>>> /sys/kernel/btf/vmlinux or some other location, depending on how
> >>>>> things are set up on your side.
> >>>>>
> >>>>> If it's /sys/kernel/btf/vmlinux, you can just `cat
> >>>>> /sys/kernel/btf/vmlinux > my_btf.bin`. If it's some other file,
> >>>>> easiest would be to just share that file. If not, it's possible to
> >>>>> extract .BTF ELF section, let me know if you need help with that.
> >>>>
> >
> >
> >
> --
> Best Regards.
> Liu Yiding
>
>
>