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 > > > or how about inluding uapi headers in libbpf-devel.. but that might > > actualy cause more confusion > > Libraries (libbpf or any other) should not install headers that > typically go into /usr/include/ > if_xdp.h case is not unique. > We'll surely add another #define, enum, etc to uapi/linux/bpf.h tomorrow. > And we will not copy paste these constants and types into tools/lib/bpf/. > In kernel tree libbpf development is using kernel tree headers. > No problem there for libbpf developers. > Packages are built out of github/libbpf that has a copy of uapi headers > necessary to create packages. > No problem there for package builders either. > But libbpf package is not going to install those uapi headers. > libbpf package installs only libbpf own headers (like libbpf.h) > The users that want to build against the latest libbpf package need > to install corresponding uapi headers package. > I don't think such dependency is specified in rpm scripts. > May be it is something to fix? Or may be not. I'll check if we can add some kernel version/package dependency > Some folks might not want to update all of /usr/include to bring libbpf-devel. > Then it would be their responsibility to get fresh /usr/include headers. jirka
