On Wed, Feb 23, 2022 at 12:18 PM Marco Vedovati <marco.vedovati@xxxxxxxxxxxxxxx> wrote: > > From: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > Sent: Thursday, February 17, 2022 11:08 PM > To: Marco Vedovati > Cc: bpf@xxxxxxxxxxxxxxx; toke@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; kernel-team@xxxxxx; Martin Kelly; ast@xxxxxxxxxx; daniel@xxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; Andrii Nakryiko > Subject: [External] Re: Clarifications on linux/types.h used with libbpf > > > On Tue, Feb 15, 2022 at 4:58 AM Marco Vedovati > > <marco.vedovati@xxxxxxxxxxxxxxx> wrote: > > > > > > Hi, > > > > > > I have few questions about the linux/types.h file used to build bpf > > [cut] > > > > > > include/uapi/linux/types.h (UAPI header) is different from > > include/linux/types.h (kernel-internal header). Libbpf has to > > reimplement minimum amount of declarations from kernel-internal > > include/linux/types.h to build outside of the kernel. But short answer > > is they are different headers, so I suspect that no, libbpf can't use > > just UAPI version. > > Thank you for clarifying some of my confusions. > > So if I understood correctly, the only use of libbpf:include/linux/types.h > is to allow building the library out of the kernel tree. > > An ambiguity I have found is about what version of linux/types.h to use > use when building bpf source code (that includes <linux/bpf.h>). > I saw 2 options: > > - do like libbpf-bootstrap C examples, that uses whatever linux/types.h > version available on the building host. This is however adding more > dependencies that are satisfied with extra "-idirafter" compiler options. > > - do like bpftool's makefile, that builds bpf source code by including > tools/include/uapi/. This does not require the "-idirafter" trick. Applications shouldn't be building against Linux-internal include/linux/types.h. It should always be resolved to include/uapi/linux/types.h. > > Anyway, checking the history of "tools/include/uapi/linux/types.h", I > believe that this file is mistakenly licensed as "GPL-2.0" instead of > "GPL-2.0 WITH Linux-syscall-note". I may come up with a patch to fix it. > > > > > Thanks, > > Marco >
