linux-kernel - Re: [bpf-next:master 8/9] FAILED: load BTF from .tmp_vmlinux1.BTF.1: No such file or directory

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Message-ID: <eb33f1da-bba4-44e3-9585-a94d4dbbdf75@oracle.com>
Date: Mon, 5 Jan 2026 16:47:05 +0000
From: Alan Maguire <alan.maguire@...cle.com>
To: Ihor Solodrai <ihor.solodrai@...ux.dev>,
        kernel test robot
 <lkp@...el.com>, Dinh Nguyen <dinguyen@...nel.org>
Cc: oe-kbuild-all@...ts.linux.dev, Andrii Nakryiko <andrii@...nel.org>,
        bpf <bpf@...r.kernel.org>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, dwarves <dwarves@...r.kernel.org>
Subject: Re: [bpf-next:master 8/9] FAILED: load BTF from .tmp_vmlinux1.BTF.1:
 No such file or directory

On 29/12/2025 19:28, Ihor Solodrai wrote:
> On 12/24/25 5:01 PM, kernel test robot wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
>> head:   f14cdb1367b947d373215e36cfe9c69768dbafc9
>> commit: 522397d05e7d4a7c30b91841492360336b24f833 [8/9] resolve_btfids: Change in-place update with raw binary output
>> config: nios2-randconfig-001-20251224 (https://download.01.org/0day-ci/archive/20251225/202512250932.X7mdviuH-lkp@intel.com/config)
>> compiler: nios2-linux-gcc (GCC) 11.5.0
>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251225/202512250932.X7mdviuH-lkp@intel.com/reproduce)
>>
>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>> the same patch/commit), kindly add following tags
>> | Reported-by: kernel test robot <lkp@...el.com>
>> | Closes: https://lore.kernel.org/oe-kbuild-all/202512250932.X7mdviuH-lkp@intel.com/
>>
>> All errors (new ones prefixed by >>):
>>
>>    Complex, interval and imaginary float types are not supported
>>    Error while encoding BTF.
> 
> Hi Dinh, Alan,
> 
> Not sure why this has surfaced only now, but it appears that kernel
> build with ARCH=nios2 and CONFIG_DEBUG_INFO_BTF=y has been broken for
> a long time.
> 
> I tried the following revisions:
>   - bpf-next @ 522397d05e7d as in bug report
>   - bpf-next @ 014e1cdb5fad without the gen-btf.sh patch
>   - v6.18
>   - v6.17
>   - v6.12 (~1y ago)
> 
> All fail with the same error in pahole [1]:
> 
> 	Complex, interval and imaginary float types are not supported
> 	Encountered error while encoding BTF.
> 
> I used v1.24 in most experiments, the default debian:bookworm
> installation.  Upgrading pahole to v1.31 doesn't change this behavior.
> 
> I also stumbled on a phoronix article [2], saying Nios II support has
> ended with GCC 15. Is it actively supported in Linux?
> 
> Not clear to me if anything needs to be fixed here. I'd appreciate any input.
> 
> Thanks.

hi Ihor, it's probably worth separating the issue of complex/interval/imaginary
support from nios2 support. In terms of the latter, if the breakage is old I agree
that it is at least a lower priority. Did you figure out where the problematic
type comes from? Might be a workaround we could apply there.

It also does raise a valid issue about supporting a larger menu of floating-point
types supported by GNU C/C++. To do so it looks like we'd need 2 bits 
to support the range of possibilities 

- standard floating point
- complex floating point
- interval floating point
- imaginary floating point

Is there interest in supporting these? Thanks!

Alan
 
> 
> [1] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/tree/btf_encoder.c?h=v1.31#n469
> [2] https://www.phoronix.com/news/GCC-15-Drops-Altera-Nios-II
> 
> 
>>>> FAILED: load BTF from .tmp_vmlinux1.BTF.1: No such file or directory
>>
> 
>