Toke Høiland-Jørgensen wrote: > Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes: > > > 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. > > > >> 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. > > 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. > > We can certainly tie libbpf to the kernel version. The obvious way to do > that is to just ship the version of libbpf that's in the kernel tree of > whatever kernel version the distro ships. But how will we handle > bugfixes, then? You've explicitly stated that libbpf gets no bugfixes > outside of bpf-next... > > -Toke We use libbpf and build for a wide variety of kernels so I don't think we want to make libbpf kernel version specific. I always want the latest libbpf features even when building on older kernels. I generally use the bpf-next version though so maybe I'm not the target user. .John
