On Tue, 30 May 2017 09:34:12 -0700 Alexei Starovoitov <alexei.starovoi...@gmail.com> wrote:
> On Tue, May 30, 2017 at 02:37:51PM +0200, Jesper Dangaard Brouer wrote: > > An eBPF ELF file generated with LLVM can contain several program > > section, which can be used for bpf tail calls. The bpf prog file > > descriptors are accessible via array prog_fd[]. > > > > At-least XDP samples assume ordering, and uses prog_fd[0] is the main > > XDP program to attach. The actual order of array prog_fd[] depend on > > whether or not a bpf program section is referencing any maps or not. > > Not using a map result in being loaded/processed after all other > > prog section. Thus, this can lead to some very strange and hard to > > debug situation, as the user can only see a FD and cannot correlated > > that with the ELF section name. > > > > The fix is rather simple, and even removes duplicate memcmp code. > > Simply load program sections as the last step, instead of > > load_and_attach while processing the relocation section. > > > > When working with tail calls, it become even more essential that the > > order of prog_fd[] is consistant, like the current dependency of the > > map_fd[] order. > > > > Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com> > > Looks fine, but imo net-next is better, since it's not a bugfix > to anything in the net tree, but a general improvement. Okay, I'm fine with this going into net-next. I'm running with own fix[1] in my git-tree, so I can get my tail call example[2] working. [1] https://github.com/netoptimizer/prototype-kernel/commit/e785522d84d5bf [2] https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/samples/bpf > Acked-by: Alexei Starovoitov <a...@kernel.org> Thanks! -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
