* [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name
@ 2022-05-21 7:57 Maciej Żenczykowski
2022-05-23 19:32 ` Alexei Starovoitov
0 siblings, 1 reply; 6+ messages in thread
From: Maciej Żenczykowski @ 2022-05-21 7:57 UTC (permalink / raw)
To: Maciej Żenczykowski, Alexei Starovoitov, Daniel Borkmann
Cc: Linux Network Development Mailing List,
Linux Kernel Mailing List, BPF Mailing List, David S . Miller
From: Maciej Żenczykowski <maze@google.com>
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@google.com>
---
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);
} else {
map->ops->map_seq_show_elem(map, key, m);
}
--
2.36.1.124.g0e6072fb45-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name
2022-05-21 7:57 [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name Maciej Żenczykowski
@ 2022-05-23 19:32 ` Alexei Starovoitov
2022-05-23 20:14 ` Maciej Żenczykowski
0 siblings, 1 reply; 6+ messages in thread
From: Alexei Starovoitov @ 2022-05-23 19:32 UTC (permalink / raw)
To: Maciej Żenczykowski
Cc: Maciej Żenczykowski, Alexei Starovoitov, Daniel Borkmann,
Linux Network Development Mailing List,
Linux Kernel Mailing List, BPF Mailing List, David S . Miller
On Sat, May 21, 2022 at 12:57 AM Maciej Żenczykowski
<zenczykowski@gmail.com> wrote:
>
> From: Maciej Żenczykowski <maze@google.com>
>
> 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@google.com>
> ---
> 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.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name
2022-05-23 19:32 ` Alexei Starovoitov
@ 2022-05-23 20:14 ` Maciej Żenczykowski
2022-05-23 20:21 ` Alexei Starovoitov
0 siblings, 1 reply; 6+ messages in thread
From: Maciej Żenczykowski @ 2022-05-23 20:14 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: Alexei Starovoitov, Daniel Borkmann,
Linux Network Development Mailing List,
Linux Kernel Mailing List, BPF Mailing List, David S . Miller
On Mon, May 23, 2022 at 12:32 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Sat, May 21, 2022 at 12:57 AM Maciej Żenczykowski
> <zenczykowski@gmail.com> wrote:
> >
> > From: Maciej Żenczykowski <maze@google.com>
> >
> > 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@google.com>
> > ---
> > 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.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name
2022-05-23 20:14 ` Maciej Żenczykowski
@ 2022-05-23 20:21 ` Alexei Starovoitov
2022-05-25 16:14 ` Maciej Żenczykowski
0 siblings, 1 reply; 6+ messages in thread
From: Alexei Starovoitov @ 2022-05-23 20:21 UTC (permalink / raw)
To: Maciej Żenczykowski
Cc: Alexei Starovoitov, Daniel Borkmann,
Linux Network Development Mailing List,
Linux Kernel Mailing List, BPF Mailing List, David S . Miller
On Mon, May 23, 2022 at 1:14 PM Maciej Żenczykowski
<zenczykowski@gmail.com> wrote:
>
> On Mon, May 23, 2022 at 12:32 PM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > On Sat, May 21, 2022 at 12:57 AM Maciej Żenczykowski
> > <zenczykowski@gmail.com> wrote:
> > >
> > > From: Maciej Żenczykowski <maze@google.com>
> > >
> > > 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@google.com>
> > > ---
> > > 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.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name
2022-05-23 20:21 ` Alexei Starovoitov
@ 2022-05-25 16:14 ` Maciej Żenczykowski
2022-05-25 16:32 ` Alexei Starovoitov
0 siblings, 1 reply; 6+ messages in thread
From: Maciej Żenczykowski @ 2022-05-25 16:14 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: Alexei Starovoitov, Daniel Borkmann,
Linux Network Development Mailing List,
Linux Kernel Mailing List, BPF Mailing List, David S . Miller
On Mon, May 23, 2022 at 1:21 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Mon, May 23, 2022 at 1:14 PM Maciej Żenczykowski
> <zenczykowski@gmail.com> wrote:
> >
> > On Mon, May 23, 2022 at 12:32 PM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > On Sat, May 21, 2022 at 12:57 AM Maciej Żenczykowski
> > > <zenczykowski@gmail.com> wrote:
> > > >
> > > > From: Maciej Żenczykowski <maze@google.com>
> > > >
> > > > 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@google.com>
> > > > ---
> > > > 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.
Hmm. This seems very annoying to use in practice.
* it seems to default to disabled, and as such is disabled on:
- my Debian laptop and desktop (well google's corp Linux distro, but
it should be close enough to Debian here)
- my latest Fedora 36 Desktop and VMs
- our production (server) kernels
- all current Android Common Kernel / Generic Kernel Image / Pixel kernel trees
- Android UML test image kernel build scripts
* enabling it on our server kernels results in a compilation failure
(probably some missing backports, they're backported up the wazoo)
* enabling it on ACK 5.10 tree results in a very different build failure
* enabling it on ACK 5.15 successfully builds, but doesn't seem to work:
# uname -r
5.15.41-04342-g39bba8f6b9fe
# zcat /proc/config.gz | egrep BPF_PRELOAD
CONFIG_BPF_PRELOAD=y
CONFIG_BPF_PRELOAD_UMD=y
# cat /proc/mounts | egrep sys
none /sys sysfs rw,relatime 0 0
none /sys/fs/bpf bpf rw,relatime 0 0
# cd /sys/fs/bpf
root@uml-x86-64:/sys/fs/bpf# ls -al
total 0
drwxrwxrwt 2 root root 0 May 25 15:13 .
drwxr-xr-x 6 root root 0 May 25 15:13 ..
Perhaps a limitation of UML, or something funky in the build process,
or the files don't show up until maps/progs are pinned?
Hard to say - this is after running our bpf (python) test suite
(though it might not use pinned maps/programs)...
* finally.. I think it increases kernel size by a lot since I see:
120K ./kernel/bpf/preload/bpf_preload_kern.o
and in a different tree:
232K ./kernel/bpf/preload/bpf_preload.ko
I did get it to work by building a net next tree with the option
manually enabled and installing it on some dev servers.
Those by default have some pinned progs/maps, and I do see the debug files.
When it works it's really nice... but I don't think I'm willing to pay
the complexity/memory costs.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name
2022-05-25 16:14 ` Maciej Żenczykowski
@ 2022-05-25 16:32 ` Alexei Starovoitov
0 siblings, 0 replies; 6+ messages in thread
From: Alexei Starovoitov @ 2022-05-25 16:32 UTC (permalink / raw)
To: Maciej Żenczykowski
Cc: Alexei Starovoitov, Daniel Borkmann,
Linux Network Development Mailing List,
Linux Kernel Mailing List, BPF Mailing List, David S . Miller
On Wed, May 25, 2022 at 9:14 AM Maciej Żenczykowski
<zenczykowski@gmail.com> wrote:
>
> When it works it's really nice...
Load your own bpf map iterator program and pin anywhere
in bpffs under name of choice and your own access permissions.
See selftests/bpf/progs/bpf_iter_bpf_map.c
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-05-25 16:33 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2022-05-21 7:57 [PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name Maciej Żenczykowski
2022-05-23 19:32 ` Alexei Starovoitov
2022-05-23 20:14 ` Maciej Żenczykowski
2022-05-23 20:21 ` Alexei Starovoitov
2022-05-25 16:14 ` Maciej Żenczykowski
2022-05-25 16:32 ` Alexei Starovoitov
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