On Tue, 31 Jan 2017 20:54:10 -0800 Alexei Starovoitov <[email protected]> wrote:
> On Tue, Jan 31, 2017 at 9:54 AM, Jesper Dangaard Brouer via > iovisor-dev <[email protected]> wrote: > > > > On Sat, 28 Jan 2017 10:14:58 +1100 Brendan Gregg > > <[email protected]> wrote: > > > >> I did some in the bcc ref guide, but it's incomplete, and the bcc versions: > >> https://github.com/iovisor/bcc/blob/master/docs/reference_guide.md > > > > Thanks! - this seem rather BCC specific syntax, and I'm looking for > > documentation close for the kernel (samples/bpf/). > > > > The best documentation I found was the man-page for the syscall bpf(2): > > http://man7.org/linux/man-pages/man2/bpf.2.html > > > > In lack of a better place, I've started documenting eBPF here: > > https://prototype-kernel.readthedocs.io/en/latest/bpf/index.html > > > > This doc is compatible with the kernels doc format, and I hope we can > > push this into the kernel tree, if it turns out to be valuable? > > (https://www.kernel.org/doc/html/latest/) > > yeah. definitely would be great to add map descriptions to the kernel docs. > So far most of it is in commit logs. > git log kernel/bpf/arraymap.c|tail -33 > git log kernel/bpf/hashtab.c|tail -33 > will give an overview of key hash and array map principles. Thanks, I'm using that to write some doc. http://prototype-kernel.readthedocs.io/en/latest/bpf/ebpf_maps.html Gotten to BPF_MAP_TYPE_ARRAY http://prototype-kernel.readthedocs.io/en/latest/bpf/ebpf_maps.html#bpf-map-type-array Can you explain the difference between the kernel and userspace side of the call bpf_map_lookup_elem() ? Kernel side: long *value = bpf_map_lookup_elem(&my_map, &key); Userspace side: long long value; bpf_map_lookup_elem(map_fd[0], &key, &value) Looks like userspace gets a copy of the memory... If so, how can userspace then increment the value safely? -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer _______________________________________________ iovisor-dev mailing list [email protected] https://lists.iovisor.org/mailman/listinfo/iovisor-dev
