linux-stable.git/include/uapi/linux/bpf.h, branch v4.8.2

bpf: fix bpf_skb_in_cgroup helper naming

2016-08-13T04:53:33+00:00

While hashing out BPF's current_task_under_cgroup helper bits, it came
to discussion that the skb_in_cgroup helper name was suboptimally chosen.

Tejun says:

  So, I think in_cgroup should mean that the object is in that
  particular cgroup while under_cgroup in the subhierarchy of that
  cgroup. Let's rename the other subhierarchy test to under too. I
  think that'd be a lot less confusing going forward.

  [...]

  It's more intuitive and gives us the room to implement the real
  "in" test if ever necessary in the future.

Since this touches uapi bits, we need to change this as long as v4.8
is not yet officially released. Thus, change the helper enum and rename
related bits.

Fixes: 4a482f34afcc ("cgroup: bpf: Add bpf_skb_in_cgroup_proto")
Reference: http://patchwork.ozlabs.org/patch/658500/
Suggested-by: Sargun Dhillon 
Suggested-by: Tejun Heo 
Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov

bpf: Add bpf_probe_write_user BPF helper to be called in tracers

2016-07-26T01:07:48+00:00

This allows user memory to be written to during the course of a kprobe.
It shouldn't be used to implement any kind of security mechanism
because of TOC-TOU attacks, but rather to debug, divert, and
manipulate execution of semi-cooperative processes.

Although it uses probe_kernel_write, we limit the address space
the probe can write into by checking the space with access_ok.
We do this as opposed to calling copy_to_user directly, in order
to avoid sleeping. In addition we ensure the threads's current fs
/ segment is USER_DS and the thread isn't exiting nor a kernel thread.

Given this feature is meant for experiments, and it has a risk of
crashing the system, and running programs, we print a warning on
when a proglet that attempts to use this helper is installed,
along with the pid and process name.

Signed-off-by: Sargun Dhillon 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: add XDP_TX xdp_action for direct forwarding

2016-07-20T04:46:32+00:00

XDP enabled drivers must transmit received packets back out on the same
port they were received on when a program returns this action.

Signed-off-by: Brenden Blanco 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: add XDP prog type for early driver filter

2016-07-20T04:46:31+00:00

Add a new bpf prog type that is intended to run in early stages of the
packet rx path. Only minimal packet metadata will be available, hence a
new context type, struct xdp_md, is exposed to userspace. So far only
expose the packet start and end pointers, and only in read mode.

An XDP program must return one of the well known enum values, all other
return codes are reserved for future use. Unfortunately, this
restriction is hard to enforce at verification time, so take the
approach of warning at runtime when such programs are encountered. Out
of bounds return codes should alias to XDP_ABORTED.

Signed-off-by: Brenden Blanco 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: avoid stack copy and use skb ctx for event output

2016-07-15T21:23:56+00:00

This work addresses a couple of issues bpf_skb_event_output()
helper currently has: i) We need two copies instead of just a
single one for the skb data when it should be part of a sample.
The data can be non-linear and thus needs to be extracted via
bpf_skb_load_bytes() helper first, and then copied once again
into the ring buffer slot. ii) Since bpf_skb_load_bytes()
currently needs to be used first, the helper needs to see a
constant size on the passed stack buffer to make sure BPF
verifier can do sanity checks on it during verification time.
Thus, just passing skb->len (or any other non-constant value)
wouldn't work, but changing bpf_skb_load_bytes() is also not
the proper solution, since the two copies are generally still
needed. iii) bpf_skb_load_bytes() is just for rather small
buffers like headers, since they need to sit on the limited
BPF stack anyway. Instead of working around in bpf_skb_load_bytes(),
this work improves the bpf_skb_event_output() helper to address
all 3 at once.

We can make use of the passed in skb context that we have in
the helper anyway, and use some of the reserved flag bits as
a length argument. The helper will use the new __output_custom()
facility from perf side with bpf_skb_copy() as callback helper
to walk and extract the data. It will pass the data for setup
to bpf_event_output(), which generates and pushes the raw record
with an additional frag part. The linear data used in the first
frag of the record serves as programmatically defined meta data
passed along with the appended sample.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: introduce bpf_get_current_task() helper

2016-07-09T04:00:16+00:00

over time there were multiple requests to access different data
structures and fields of task_struct current, so finally add
the helper to access 'current' as-is. Tracing bpf programs will do
the rest of walking the pointers via bpf_probe_read().
Note that current can be null and bpf program has to deal it with,
but even dumb passing null into bpf_probe_read() is still safe.

Suggested-by: Brendan Gregg 
Signed-off-by: Alexei Starovoitov 
Acked-by: Daniel Borkmann 
Signed-off-by: David S. Miller

bpf: add bpf_get_hash_recalc helper

2016-07-04T23:08:40+00:00

If skb_clear_hash() was invoked due to mangling of relevant headers and
BPF program needs skb->hash later on, we can add a helper to trigger hash
recalculation via bpf_get_hash_recalc().

The helper will return the newly retrieved hash directly, but later access
can also be done via skb context again through skb->hash directly (inline)
without needing to call the helper once more.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

cgroup: bpf: Add bpf_skb_in_cgroup_proto

2016-07-01T20:32:13+00:00

Adds a bpf helper, bpf_skb_in_cgroup, to decide if a skb->sk
belongs to a descendant of a cgroup2.  It is similar to the
feature added in netfilter:
commit c38c4597e4bf ("netfilter: implement xt_cgroup cgroup2 path match")

The user is expected to populate a BPF_MAP_TYPE_CGROUP_ARRAY
which will be used by the bpf_skb_in_cgroup.

Modifications to the bpf verifier is to ensure BPF_MAP_TYPE_CGROUP_ARRAY
and bpf_skb_in_cgroup() are always used together.

Signed-off-by: Martin KaFai Lau 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: Tejun Heo 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

cgroup: bpf: Add BPF_MAP_TYPE_CGROUP_ARRAY

2016-07-01T20:30:38+00:00

Add a BPF_MAP_TYPE_CGROUP_ARRAY and its bpf_map_ops's implementations.
To update an element, the caller is expected to obtain a cgroup2 backed
fd by open(cgroup2_dir) and then update the array with that fd.

Signed-off-by: Martin KaFai Lau 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
Cc: Tejun Heo 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: add bpf_skb_change_type helper

2016-06-30T09:54:40+00:00

This work adds a helper for changing skb->pkt_type in a controlled way.
We only allow a subset of possible values and can extend that in future
should other use cases come up. Doing this as a helper has the advantage
that errors can be handeled gracefully and thus helper kept extensible.

It's a write counterpart to pkt_type member we can already read from
struct __sk_buff context. Major use case is to change incoming skbs to
PACKET_HOST in a programmatic way instead of having to recirculate via
redirect(..., BPF_F_INGRESS), for example.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller