On Mon, 28 Oct 2019 15:32:26 +0000
Yonghong Song <yhs@xxxxxx> wrote:
> On 10/28/19 6:15 AM, Toke Høiland-Jørgensen wrote:
> > Jesper Dangaard Brouer <brouer@xxxxxxxxxx> writes:
> >
> >> On Sun, 27 Oct 2019 21:53:19 +0100
> >> Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
> >>
> >>> diff --git a/tools/testing/selftests/bpf/progs/test_pinning.c b/tools/testing/selftests/bpf/progs/test_pinning.c
> >>> new file mode 100644
> >>> index 000000000000..ff2d7447777e
> >>> --- /dev/null
> >>> +++ b/tools/testing/selftests/bpf/progs/test_pinning.c
> >>> @@ -0,0 +1,29 @@
> >>> +// SPDX-License-Identifier: GPL-2.0
> >>> +
> >>> +#include <linux/bpf.h>
> >>> +#include "bpf_helpers.h"
> >>> +
> >>> +int _version SEC("version") = 1;
> >>> +
> >>> +struct {
> >>> + __uint(type, BPF_MAP_TYPE_ARRAY);
> >>> + __uint(max_entries, 1);
> >>> + __type(key, __u32);
> >>> + __type(value, __u64);
> >>> + __uint(pinning, LIBBPF_PIN_BY_NAME);
> >>> +} pinmap SEC(".maps");
> >>
> >> So, this is the new BTF-defined maps syntax.
> >>
> >> Please remind me, what version of LLVM do we need to compile this?
> >
> > No idea what the minimum version is. I'm running LLVM 9.0 :)
>
> LLVM 9.0 starts to support .maps.
> There is no dependency on pahole.
LLVM 9.0.0 is still very new:
- 19 September 2019: LLVM 9.0.0 is now available
For my XDP-tutorial[1], I cannot required people to have this new llvm
version. But I would like to teach people about this new syntax (note,
I can upgrade libbpf version via git-submodule, and update bpf_helpers.h).
To Andrii, any recommendations on how I can do the transition?
I'm thinking, it should be possible to define both ELF-object sections
SEC "maps" and ".maps" at the same time. But how does libbpf handle that?
(Who takes precedence?)
(Alternatively, I can detect the LLVM version, in the Makefile, and have
a #ifdef define in the code)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
[1] https://github.com/xdp-project/xdp-tutorial
