On Tue, 2024-05-21 at 10:15 +0100, Alan Maguire wrote: [...] > This is a neat approach, and as you say it eliminates the need to modify > bpftool to handle distilled base BTF and relocation. The only wrinkle > is resolve_btfids; we call resolve_btfids for modules with a "-B > vmlinux" argument, so in that case we'd be calling btf_parse_elf() with > both a split and base BTF. According to the approach outlined above, > we'd relocate split BTF - originally relative to .BTF.base - to be > relative to vmlinux BTF, but in the case of resolve_btfids we don't want > that relocation. We want the BTF ids to reflect the distilled base BTF > ids since they will be relocated later on module load along with the > split BTF references themselves. You are correct, I missed this detail, resolve_btfids needs distilled base instead of vmlinux for out of tree modules. > We can handle this by having a -R flag to skip relocation; it would > simply ensure we first try calling btf__parse(), falling back to > btf__parse_split(); we need the fallback logic as it is possible the > pahole version didn't add .BTF.base sections. This logic would only be > activated for out-of-tree module builds so seems acceptable to me. If > that makes sense, with your permission I can rework the series to > include your BTF parsing patch. Makes sense to me, but I'm curious whether you and Andrii consider this a good interface, compared to _opts version. Thanks, Eduard
