On Wed, Jan 6, 2021 at 3:27 AM Qais Yousef <qais.yousef@xxxxxxx> wrote: > > On 01/05/21 08:44, Alexei Starovoitov wrote: > > > Any pointer to an example test I could base this on? > > > > selftests/bpf/ > > I was hoping for something more elaborate. I thought there's something already > there that do some verification for raw tracepoint that I could either extend > or replicate. Otherwise this could end up being a time sink for me and I'm not > keen on jumping down this rabbit hole. One way would be to add either another custom tracepoint definition to a test module or modify the existing one to be a bare tracepoint. See links below. If it's easy to trigger those tracepoints from user-space on demand, writing a similar (to module_attach) selftest for in-kernel tracepoint is trivial. [0] https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h [1] https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/progs/test_module_attach.c#L12-L18 [2] https://github.com/torvalds/linux/blob/master/tools/testing/selftests/bpf/prog_tests/module_attach.c > > > > > - add a doc with contents from commit log. > > > > > > You're referring to the ABI part of the changelog, right? > > > > > > > The "Does bpf make things into an abi ?" question keeps coming back > > > > over and over again. > > > > Everytime we have the same answer that No, bpf cannot bake things into abi. > > > > I think once it's spelled out somewhere in Documentation/ it would be easier to > > > > repeat this message. > > > > > > How about a new Documentation/bpf/ABI.rst? I can write something up initially > > > for us to discuss in detail when I post. > > > > There is Documentation/bpf/bpf_design_QA.rst > > and we already have this text in there that was added back in 2017: > > > > Q: Does BPF have a stable ABI? > > ------------------------------ > > A: YES. BPF instructions, arguments to BPF programs, set of helper > > functions and their arguments, recognized return codes are all part > > of ABI. However there is one specific exception to tracing programs > > which are using helpers like bpf_probe_read() to walk kernel internal > > data structures and compile with kernel internal headers. Both of these > > kernel internals are subject to change and can break with newer kernels > > such that the program needs to be adapted accordingly. > > > > I'm suggesting to add an additional section to this Q/A doc to include > > more or less > > the same text you had in the commit log. > > Works for me. > > Thanks > > -- > Qais Yousef
