Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes: > On Fri, Nov 1, 2019 at 12:27 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: >> >> On Thu, Oct 31, 2019 at 01:39:12PM -0700, Alexei Starovoitov wrote: >> > On Thu, Oct 31, 2019 at 12:18 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: >> > > > >> > > > yes. older vmlinux and newer installed libbpf.so >> > > > or any version of libbpf.a that is statically linked into apps >> > > > is something that libbpf code has to support. >> > > > The server can be rebooted into older than libbpf kernel and >> > > > into newer than libbpf kernel. libbpf has to recognize all these >> > > > combinations and work appropriately. >> > > > That's what backward and forward compatibility is. >> > > > That's what makes libbpf so difficult to test, develop and code review. >> > > > What that particular server has in /usr/include is irrelevant. >> > > >> > > sure, anyway we can't compile following: >> > > >> > > tredaell@aldebaran ~ $ echo "#include <bpf/xsk.h>" | gcc -x c - >> > > In file included from <stdin>:1: >> > > /usr/include/bpf/xsk.h: In function ‘xsk_ring_prod__needs_wakeup’: >> > > /usr/include/bpf/xsk.h:82:21: error: ‘XDP_RING_NEED_WAKEUP’ undeclared (first use in this function) >> > > 82 | return *r->flags & XDP_RING_NEED_WAKEUP; >> > > ... >> > > >> > > XDP_RING_NEED_WAKEUP is defined in kernel v5.4-rc1 (77cd0d7b3f257fd0e3096b4fdcff1a7d38e99e10). >> > > XSK_UNALIGNED_BUF_ADDR_MASK and XSK_UNALIGNED_BUF_OFFSET_SHIFT are defined in kernel v5.4-rc1 (c05cd3645814724bdeb32a2b4d953b12bdea5f8c). >> > > >> > > with: >> > > kernel-headers-5.3.6-300.fc31.x86_64 >> > > libbpf-0.0.5-1.fc31.x86_64 >> > > >> > > if you're saying this is not supported, I guess we could be postponing >> > > libbpf rpm releases until we have the related fedora kernel released >> > >> > why? github/libbpf is the source of truth for building packages >> > and afaik it builds fine. >> >> because we will get issues like above if there's no kernel >> avilable that we could compile libbpf against > > what is the issue again? > bpf-next builds fine. github/libbpf builds fine. > If distro is doing something else it's distro's mistake. With that you're saying that distros should always keep their kernel headers and libbpf version in sync. Which is fine in itself; they can certainly do that. The only concern with this is that without a flow of bugfixes into the 'bpf' tree (and stable), users may end up with buggy versions of libbpf. Which is in no one's interest. So how do we avoid that? -Toke
