On Fri, Apr 28, 2017 at 04:25:04PM +0200, Jesper Dangaard Brouer wrote:
> The struct bpf_map_def was extended in commit fb30d4b71214 ("bpf: Add tests
> for map-in-map") with member unsigned int inner_map_idx. This changed the
> size
> of the maps section in the generated ELF _kern.o files.
>
> Unfortunately the loader in bpf_load.c does not detect or handle this. Thus,
> older _kern.o files became incompatible, and caused hard-to-debug errors
> where the syscall validation rejected BPF_MAP_CREATE request.
>
> This patch only detect the situation and aborts load_bpf_file(). It also
> add code comments warning people that read this loader for inspiration
> for these pitfalls.
>
> Fixes: fb30d4b71214 ("bpf: Add tests for map-in-map")
> Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
Thanks!
Acked-by: Alexei Starovoitov <a...@kernel.org>
> Is it worth to implement proper backward-compat loading of older ELF objects
> with this bpf-loader?
probably yes, since it looks like a bunch of code in samples/bpf/ still
depend on it and some features are missing in tools/lib/bpf,
so unless we actively work on improving libbpf.a
we won't be able to get rid of this 'sample' loader for some time.
