netdev - Re: [PATCH 01/11] bpf: Add btfid tool to resolve BTF IDs in ELF object

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Message-ID: <20200622085926.GC2556590@krava>
Date:   Mon, 22 Jun 2020 10:59:26 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>,
        David Miller <davem@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Wenbo Zhang <ethercflow@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Andrii Nakryiko <andriin@...com>,
        Brendan Gregg <bgregg@...flix.com>,
        Florent Revest <revest@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 01/11] bpf: Add btfid tool to resolve BTF IDs in ELF
 object

On Fri, Jun 19, 2020 at 11:12:29AM -0700, Andrii Nakryiko wrote:

SNIP

> >
> > ok
> >
> > >
> > > > +                       root = &obj->funcs;
> > > > +                       nr = &nr_funcs;
> > > > +               } else if (BTF_INFO_KIND(type->info) == BTF_KIND_STRUCT && nr_structs) {
> > >
> > > same as above: btf_is_struct
> > >
> > > But I think you also need to support unions?
> > >
> > > Also what about typedefs? A lot of types are typedefs to struct/func_proto/etc.
> >
> > I added only types which are needed at the moment, but maybe
> > we can add the basic types now, so we don't need to bother later,
> > when we forget how this all work ;-)
> 
> yeah, exactly. Once this works, no one will want to go and revisit it,
> so I'd rather make it generic from the get go, especially that it's
> really easy in this case, right?

right, I'll add the basic types

SNIP

> > >
> > > nit: should these elf_end/close properly on error?
> >
> > I wrote in the comment above that I intentionaly do not cleanup
> > on error path.. I wanted to save some time, but actualy I think
> > that would not be so expensive, I can add it
> 
> as in save CPU time in error case? Who cares about that? If saving
> developer time, well... `goto cleanup` is common and simple pattern ;)

the sooner you see the error the better ;-) ok

jirka