Re: [PATCH net-next] libbpf: use map_flags when creating maps

On 09/28/2017 07:33 PM, Craig Gallek wrote:

On Wed, Sep 27, 2017 at 6:03 PM, Daniel Borkmann [off-list ref] wrote:

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On 09/27/2017 06:29 PM, Alexei Starovoitov wrote:

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On 9/27/17 7:04 AM, Craig Gallek wrote:

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From: Craig Gallek <redacted>

[...]

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yes it will break loading of pre-compiled .o
Instead of breaking, let's fix the loader to do it the way
samples/bpf/bpf_load.c does.
See commit 156450d9d964 ("samples/bpf: make bpf_load.c code compatible
with ELF maps section changes")

+1, iproute2 loader also does map spec fixup

For libbpf it would be good also such that it reduces the diff
further between the libbpf and bpf_load so that it allows move
to libbpf for samples in future.

Fair enough, I'll try to get this to work more dynamically.  I did
noticed that the fields of struct bpf_map_def in
selftests/.../bpf_helpers.h and iproute2's struct bpf_elf_map have
diverged. The flags field is the only thing missing from libbpf right
now (and they are at the same offset for both), so it won't be an
issue for this change, but it is going to make unifying all of these
things under libbpf not trivial at some point...

Yes, iproute2 uses its own loader with own specifics related to
iproute2. With the above I rather meant that we can reduce the
gap between libbpf and bpf_load from the BPF samples, so that
it would allow us to migrate samples over entirely, there was
unfortunately never a follow-up on 156450d9d964 though, but given
there is need to extend libbpf (I guess mostly due to lpm map
handling ;)), we need to do a similar thing there as well to not
break existing obj files.