On Mon, May 23, 2022 at 1:14 PM Maciej Żenczykowski
<zenczykowski@xxxxxxxxx> wrote:
>
> On Mon, May 23, 2022 at 12:32 PM Alexei Starovoitov
> <alexei.starovoitov@xxxxxxxxx> wrote:
> >
> > On Sat, May 21, 2022 at 12:57 AM Maciej Żenczykowski
> > <zenczykowski@xxxxxxxxx> wrote:
> > >
> > > From: Maciej Żenczykowski <maze@xxxxxxxxxx>
> > >
> > > While this information can be fetched via bpftool,
> > > the cli tool itself isn't always available on more limited systems.
> > >
> > > From the information printed particularly the 'id' is useful since
> > > when combined with /proc/pid/fd/X and /proc/pid/fdinfo/X it allows
> > > tracking down which bpf maps a process has open (which can be
> > > useful for tracking down fd leaks).
> > >
> > > Signed-off-by: Maciej Żenczykowski <maze@xxxxxxxxxx>
> > > ---
> > > kernel/bpf/inode.c | 3 +++
> > > 1 file changed, 3 insertions(+)
> > >
> > > diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
> > > index 4f841e16779e..784266e258fe 100644
> > > --- a/kernel/bpf/inode.c
> > > +++ b/kernel/bpf/inode.c
> > > @@ -257,6 +257,9 @@ static int map_seq_show(struct seq_file *m, void *v)
> > > if (unlikely(v == SEQ_START_TOKEN)) {
> > > seq_puts(m, "# WARNING!! The output is for debug purpose only\n");
> > > seq_puts(m, "# WARNING!! The output format will change\n");
> > > + seq_printf(m, "# type: %d, key_size: %d, value_size: %d, max_entries: %d, id: %d\n",
> > > + map->map_type, map->key_size, map->value_size, map->max_entries,
> > > + map->id);
> >
> > Maybe use cat /sys/fs/bpf/maps.debug instead?
> > It prints map id.
>
> Is this something that was very recently added?
> I'm not seeing it on my 5.16 machine with bpffs mounted at /sys/fs/bpf.
It was there since 2020.
Make sure you have CONFIG_BPF_PRELOAD.
