netdev - Re: [PATCH bpf-next v2 0/5] bpftool: Switch to libbpf's hashmap for referencing BPF objects

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Date:   Mon, 25 Oct 2021 17:32:49 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Quentin Monnet <quentin@...valent.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 0/5] bpftool: Switch to libbpf's hashmap for
 referencing BPF objects

On Sat, Oct 23, 2021 at 1:52 PM Quentin Monnet <quentin@...valent.com> wrote:
>
> When listing BPF objects, bpftool can print a number of properties about
> items holding references to these objects. For example, it can show pinned
> paths for BPF programs, maps, and links; or programs and maps using a given
> BTF object; or the names and PIDs of processes referencing BPF objects. To
> collect this information, bpftool uses hash maps (to be clear: the data
> structures, inside bpftool - we are not talking of BPF maps). It uses the
> implementation available from the kernel, and picks it up from
> tools/include/linux/hashtable.h.
>
> This patchset converts bpftool's hash maps to a distinct implementation
> instead, the one coming with libbpf. The main motivation for this change is
> that it should ease the path towards a potential out-of-tree mirror for
> bpftool, like the one libbpf already has. Although it's not perfect to
> depend on libbpf's internal components, bpftool is intimately tied with the
> library anyway, and this looks better than depending too much on (non-UAPI)
> kernel headers.
>
> The first two patches contain preparatory work on the Makefile and on the
> initialisation of the hash maps for collecting pinned paths for objects.
> Then the transition is split into several steps, one for each kind of
> properties for which the collection is backed by hash maps.
>
> v2:
>   - Move hashmap cleanup for pinned paths for links from do_detach() to
>     do_show().
>   - Handle errors on hashmap__append() (in three of the patches).
>   - Rename bpftool_hash_fn() and bpftool_equal_fn() as hash_fn_for_key_id()
>     and equal_fn_for_key_id(), respectively.
>   - Add curly braces for hashmap__for_each_key_entry() { } in
>     show_btf_plain() and show_btf_json(), where the flow was difficult to
>     read.
>
> Quentin Monnet (5):
>   bpftool: Remove Makefile dep. on $(LIBBPF) for $(LIBBPF_INTERNAL_HDRS)
>   bpftool: Do not expose and init hash maps for pinned path in main.c
>   bpftool: Switch to libbpf's hashmap for pinned paths of BPF objects
>   bpftool: Switch to libbpf's hashmap for programs/maps in BTF listing
>   bpftool: Switch to libbpf's hashmap for PIDs/names references
>
>  tools/bpf/bpftool/Makefile |  12 ++--
>  tools/bpf/bpftool/btf.c    | 132 +++++++++++++++++--------------------
>  tools/bpf/bpftool/common.c |  50 ++++++++------
>  tools/bpf/bpftool/link.c   |  45 ++++++++-----
>  tools/bpf/bpftool/main.c   |  17 +----
>  tools/bpf/bpftool/main.h   |  54 +++++++--------
>  tools/bpf/bpftool/map.c    |  45 ++++++++-----
>  tools/bpf/bpftool/pids.c   |  90 ++++++++++++++-----------
>  tools/bpf/bpftool/prog.c   |  45 ++++++++-----
>  9 files changed, 262 insertions(+), 228 deletions(-)
>
> --
> 2.30.2
>

Applied to bpf-next, thanks.