linux-kernel - Re: [PATCH bpf-next v1 4/4] resolve_btfids: change in-place update with raw binary output

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Message-ID: <7fb4b953-449d-4f72-8bc7-2becae3cc639@linux.dev>
Date: Wed, 26 Nov 2025 10:32:30 -0800
From: Ihor Solodrai <ihor.solodrai@...ux.dev>
To: Donglin Peng <dolinux.peng@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
 Nicolas Schier <nicolas.schier@...ux.dev>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 bpf@...r.kernel.org, dwarves@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-kbuild@...r.kernel.org, Alan Maguire <alan.maguire@...cle.com>
Subject: Re: [PATCH bpf-next v1 4/4] resolve_btfids: change in-place update
 with raw binary output

On 11/25/25 8:46 PM, Donglin Peng wrote:
> On Wed, Nov 26, 2025 at 9:29 AM Ihor Solodrai <ihor.solodrai@...ux.dev> wrote:
>>
>> [...]
>>  static const char * const resolve_btfids_usage[] = {
>> @@ -823,12 +875,13 @@ int main(int argc, const char **argv)
>>                 .funcs    = RB_ROOT,
>>                 .sets     = RB_ROOT,
>>         };
>> +       char out_path[PATH_MAX];
>>         bool fatal_warnings = false;
>>         struct option btfid_options[] = {
>>                 OPT_INCR('v', "verbose", &verbose,
>>                          "be more verbose (show errors, etc)"),
>>                 OPT_STRING(0, "btf", &obj.btf_path, "BTF data",
>> -                          "BTF data"),
>> +                          "input BTF data"),
>>                 OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
>>                            "path of file providing base BTF"),
>>                 OPT_BOOLEAN(0, "fatal_warnings", &fatal_warnings,
>> @@ -844,6 +897,9 @@ int main(int argc, const char **argv)
>>
>>         obj.path = argv[0];
>>
>> +       if (load_btf(&obj))
>> +               goto out;
> 
> I think I can add the BTF sorting function here based on your patch.

Correct. Any btf2btf transformations will have to happen before the
symbols resolution.

> 
> Thanks,
> Donglin
>> +
>>         if (elf_collect(&obj))
>>                 goto out;
>>
>> @@ -853,23 +909,37 @@ int main(int argc, const char **argv)
>>          */
>>         if (obj.efile.idlist_shndx == -1 ||
>>             obj.efile.symbols_shndx == -1) {
>> -               pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
>> -               err = 0;
>> -               goto out;
>> +               pr_debug("Cannot find .BTF_ids or symbols sections, skip symbols resolution\n");
>> +               goto dump_btf;
>>         }
>>
>>         if (symbols_collect(&obj))
>>                 goto out;
>>
>> -       if (load_btf(&obj))
>> -               goto out;
>> -
>>         if (symbols_resolve(&obj))
>>                 goto out;
>>
>>         if (symbols_patch(&obj))
>>                 goto out;
>>
>> +       strcpy(out_path, obj.path);
>> +       strcat(out_path, ".btf_ids");
>> +       if (dump_raw_btf_ids(&obj, out_path))
>> +               goto out;
>> +
>> +dump_btf:
>> +       strcpy(out_path, obj.path);
>> +       strcat(out_path, ".btf");
> 
> Do we need to add .btf files to the .gitignore file?

I don't know. Probably?

I take care to cleanup temporary files in the gen-btf.sh, but it makes
sense to .gitignore them anyways, since those are temporary build
artifacts.

> 
> Thanks,
> Donglin
> 
>> +       if (dump_raw_btf(obj.btf, out_path))
>> +               goto out;
>> +
>> +       if (obj.base_btf) {
>> +               strcpy(out_path, obj.path);
>> +               strcat(out_path, ".distilled_base.btf");
>> +               if (dump_raw_btf(obj.base_btf, out_path))
>> +                       goto out;
>> +       }
>> +
>>         if (!(fatal_warnings && warnings))
>>                 err = 0;
>>  out:
>> --
>> 2.52.0
>>