On Mon, May 23, 2022 at 03:02:31PM -0700, Andrii Nakryiko wrote:
> On Mon, May 23, 2022 at 1:26 PM Michael Mullin <masmullin@xxxxxxxxx> wrote:
> >
> > When generating a skeleton which has an mmaped map field, bpftool's
> > output is missing the map structure. This causes a compile break when
> > the generated skeleton is compiled as the field belongs to the internal
> > struct maps, not directly to the obj.
> >
> > Signed-off-by: Michael Mullin <masmullin@xxxxxxxxx>
> > ---
> > tools/bpf/bpftool/gen.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> > index f158dc1c2149..b49293795ba0 100644
> > --- a/tools/bpf/bpftool/gen.c
> > +++ b/tools/bpf/bpftool/gen.c
> > @@ -853,7 +853,7 @@ codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped)
> > i, bpf_map__name(map), i, ident);
> > /* memory-mapped internal maps */
> > if (mmaped && is_internal_mmapable_map(map, ident, sizeof(ident))) {
> > - printf("\ts->maps[%zu].mmaped = (void **)&obj->%s;\n",
> > + printf("\ts->maps[%zu].mmaped = (void **)&obj->maps.%s;\n",
>
> That's not right. maps.my_map is struct bpf_map *, but mmaped is
> supposed to be a blob of memory that is memory-mapped into map.
>
> Can you elaborate on how you trigger that compilation error with a
> small example?
I have an a very small example on github. I have added some sed fixes to
my Makefile make my sample program compile.
https://github.com/masmullin2000/libbpf-sample/tree/main/c/simple
https://github.com/masmullin2000/libbpf-sample/tree/02c7f945bf9027daedec04f485a320ba2df28204/c/simple
contains broken code.
I apologize if this is an incorrect way to share external code. I
haven't found the proper way to share example code from
kernelnewbies.org
>
> > i, ident);
> > }
> > i++;
> > --
> > 2.36.1
> >
