On 2/27/20 10:11 PM, Daniel Borkmann wrote:
[ +tj ]
On 2/27/20 7:26 PM, Andrey Ignatov wrote:
Stanislav Fomichev <sdf@xxxxxxxxxxx> [Thu, 2020-02-27 10:01 -0800]:
On 02/26, Andrey Ignatov wrote:
drgn is a debugger that reads kernel memory and uses DWARF to get types
and symbols. See [1], [2] and [3] for more details on drgn.
Since drgn operates on kernel memory it has access to kernel internals
that user space doesn't. It allows to get extended info about various
kernel data structures.
Introduce bpf.py drgn script to list BPF programs and maps and their
properties unavailable to user space via kernel API.
Any reason this is not pushed to https://github.com/osandov/drgn/ ?
I have a bunch of networking helpers for drgn as well, but I was
thinking about contributing them to the drgn github, not the kernel.
IMO, seems like a better place to consolidate all drgn stuff.
I have this part in the commit message:
The script can be sent to drgn repo where it's easier to maintain its
"drgn-ness", but in kernel tree it should be easier to maintain BPF
functionality itself what can be more important in this case.
That's being said it's debatable which place is better and I'm still
trying to figure it out myself since, from what i see, there is no
widely adopted practice.
I've been contributing to drgn as well mostly in two forms:
* helpers [1];
* examples [2]
And so far I used examples/ dir as a place to keep small useful "tools"
(tcp_sock.py, cgroup.py, bpf.py).
But there is no place for bigger "scripts" or "tools" in drgn (yet?). On
the other hand I see two drgn scripts in kernel tree already:
* tools/cgroup/iocost_coef_gen.py
* tools/cgroup/iocost_monitor.py
So maybe it's time to discuss where to keep tools like this in the
future.
In this specifc case I'd love to see feedback from Omar and BPF
maintainers.
I can certainly see both sides given that drgn tools have been added to
tools/cgroup/ already. I presume if so, then these could live in tools/drgn/
which would also make it more clear what is needed to run as dependency
plus there should be be a proper high-level readme to document what developers
need to run in order to run them. But from looking at [1], I can also see that
those scripts would depend on new helpers being added/updated/deleted, so it
might be easier to add drgn/tools/ directory where scripts could be updated
in one go with updates to drgn helpers. Either way, I think it would be nice
to add documentation somewhere for getting people started.
One example that should definitely be avoided is 9ea37e24d4a9 ("iocost: Fix
iocost_monitor.py due to helper type mismatch") due to both living in separate
places. A third option to think about (if this is to be adapted by more subsystems)
could be to have all the kernel-specific helpers from drgn/helpers/linux under
tools/drgn/helpers/ in the kernel tree and the tools living under
tools/drgn/<subsys>/ e.g. tools/drgn/bpf/.
[1] https://github.com/osandov/drgn/tree/master/drgn/helpers/linux
[2] https://github.com/osandov/drgn/tree/master/examples/linux
