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  1. 26 9月, 2020 6 次提交
    • J
      bpf: Add comment to document BTF type PTR_TO_BTF_ID_OR_NULL · ba5f4cfe
      由 John Fastabend 提交于 
      The meaning of PTR_TO_BTF_ID_OR_NULL differs slightly from other types
denoted with the *_OR_NULL type. For example the types PTR_TO_SOCKET
and PTR_TO_SOCKET_OR_NULL can be used for branch analysis because the
type PTR_TO_SOCKET is guaranteed to _not_ have a null value.

In contrast PTR_TO_BTF_ID and BTF_TO_BTF_ID_OR_NULL have slightly
different meanings. A PTR_TO_BTF_TO_ID may be a pointer to NULL value,
but it is safe to read this pointer in the program context because
the program context will handle any faults. The fallout is for
PTR_TO_BTF_ID the verifier can assume reads are safe, but can not
use the type in branch analysis. Additionally, authors need to be
extra careful when passing PTR_TO_BTF_ID into helpers. In general
helpers consuming type PTR_TO_BTF_ID will need to assume it may
be null.

Seeing the above is not obvious to readers without the back knowledge
lets add a comment in the type definition.

Editorial comment, as networking and tracing programs get closer
and more tightly merged we may need to consider a new type that we
can ensure is non-null for branch analysis and also passing into
helpers.
Signed-off-by: NJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NLorenz Bauer <lmb@cloudflare.com>
      ba5f4cfe
    • M
      bpf: Change bpf_sk_assign to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON · 27e5203b
      由 Martin KaFai Lau 提交于 
      This patch changes the bpf_sk_assign() to take
ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will work with the pointer
returned by the bpf_skc_to_*() helpers also.

The bpf_sk_lookup_assign() is taking ARG_PTR_TO_SOCKET_"OR_NULL".  Meaning
it specifically takes a literal NULL.  ARG_PTR_TO_BTF_ID_SOCK_COMMON
does not allow a literal NULL, so another ARG type is required
for this purpose and another follow-up patch can be used if
there is such need.
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200925000415.3857374-1-kafai@fb.com
      27e5203b
    • M
      bpf: Change bpf_tcp_*_syncookie to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON · c0df236e
      由 Martin KaFai Lau 提交于 
      This patch changes the bpf_tcp_*_syncookie() to take
ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will work with the pointer
returned by the bpf_skc_to_*() helpers also.
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NLorenz Bauer <lmb@cloudflare.com>
Link: https://lore.kernel.org/bpf/20200925000409.3856725-1-kafai@fb.com
      c0df236e
    • M
      bpf: Change bpf_sk_storage_*() to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON · 592a3498
      由 Martin KaFai Lau 提交于 
      This patch changes the bpf_sk_storage_*() to take
ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will work with the pointer
returned by the bpf_skc_to_*() helpers also.

A micro benchmark has been done on a "cgroup_skb/egress" bpf program
which does a bpf_sk_storage_get().  It was driven by netperf doing
a 4096 connected UDP_STREAM test with 64bytes packet.
The stats from "kernel.bpf_stats_enabled" shows no meaningful difference.

The sk_storage_get_btf_proto, sk_storage_delete_btf_proto,
btf_sk_storage_get_proto, and btf_sk_storage_delete_proto are
no longer needed, so they are removed.
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NLorenz Bauer <lmb@cloudflare.com>
Link: https://lore.kernel.org/bpf/20200925000402.3856307-1-kafai@fb.com
      592a3498
    • M
      bpf: Change bpf_sk_release and bpf_sk_*cgroup_id to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON · a5fa25ad
      由 Martin KaFai Lau 提交于 
      The previous patch allows the networking bpf prog to use the
bpf_skc_to_*() helpers to get a PTR_TO_BTF_ID socket pointer,
e.g. "struct tcp_sock *".  It allows the bpf prog to read all the
fields of the tcp_sock.

This patch changes the bpf_sk_release() and bpf_sk_*cgroup_id()
to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will
work with the pointer returned by the bpf_skc_to_*() helpers
also.  For example, the following will work:

	sk = bpf_skc_lookup_tcp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0);
	if (!sk)
		return;
	tp = bpf_skc_to_tcp_sock(sk);
	if (!tp) {
		bpf_sk_release(sk);
		return;
	}
	lsndtime = tp->lsndtime;
	/* Pass tp to bpf_sk_release() will also work */
	bpf_sk_release(tp);

Since PTR_TO_BTF_ID could be NULL, the helper taking
ARG_PTR_TO_BTF_ID_SOCK_COMMON has to check for NULL at runtime.

A btf_id of "struct sock" may not always mean a fullsock.  Regardless
the helper's running context may get a non-fullsock or not,
considering fullsock check/handling is pretty cheap, it is better to
keep the same verifier expectation on helper that takes ARG_PTR_TO_BTF_ID*
will be able to handle the minisock situation.  In the bpf_sk_*cgroup_id()
case,  it will try to get a fullsock by using sk_to_full_sk() as its
skb variant bpf_sk"b"_*cgroup_id() has already been doing.

bpf_sk_release can already handle minisock, so nothing special has to
be done.
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200925000356.3856047-1-kafai@fb.com
      a5fa25ad
    • M
      bpf: Enable bpf_skc_to_* sock casting helper to networking prog type · 1df8f55a
      由 Martin KaFai Lau 提交于 
      There is a constant need to add more fields into the bpf_tcp_sock
for the bpf programs running at tc, sock_ops...etc.

A current workaround could be to use bpf_probe_read_kernel().  However,
other than making another helper call for reading each field and missing
CO-RE, it is also not as intuitive to use as directly reading
"tp->lsndtime" for example.  While already having perfmon cap to do
bpf_probe_read_kernel(), it will be much easier if the bpf prog can
directly read from the tcp_sock.

This patch tries to do that by using the existing casting-helpers
bpf_skc_to_*() whose func_proto returns a btf_id.  For example, the
func_proto of bpf_skc_to_tcp_sock returns the btf_id of the
kernel "struct tcp_sock".

These helpers are also added to is_ptr_cast_function().
It ensures the returning reg (BPF_REF_0) will also carries the ref_obj_id.
That will keep the ref-tracking works properly.

The bpf_skc_to_* helpers are made available to most of the bpf prog
types in filter.c. The bpf_skc_to_* helpers will be limited by
perfmon cap.

This patch adds a ARG_PTR_TO_BTF_ID_SOCK_COMMON.  The helper accepting
this arg can accept a btf-id-ptr (PTR_TO_BTF_ID + &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON])
or a legacy-ctx-convert-skc-ptr (PTR_TO_SOCK_COMMON).  The bpf_skc_to_*()
helpers are changed to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that
they will accept pointer obtained from skb->sk.

Instead of specifying both arg_type and arg_btf_id in the same func_proto
which is how the current ARG_PTR_TO_BTF_ID does, the arg_btf_id of
the new ARG_PTR_TO_BTF_ID_SOCK_COMMON is specified in the
compatible_reg_types[] in verifier.c.  The reason is the arg_btf_id is
always the same.  Discussion in this thread:
https://lore.kernel.org/bpf/20200922070422.1917351-1-kafai@fb.com/

The ARG_PTR_TO_BTF_ID_ part gives a clear expectation that the helper is
expecting a PTR_TO_BTF_ID which could be NULL.  This is the same
behavior as the existing helper taking ARG_PTR_TO_BTF_ID.

The _SOCK_COMMON part means the helper is also expecting the legacy
SOCK_COMMON pointer.

By excluding the _OR_NULL part, the bpf prog cannot call helper
with a literal NULL which doesn't make sense in most cases.
e.g. bpf_skc_to_tcp_sock(NULL) will be rejected.  All PTR_TO_*_OR_NULL
reg has to do a NULL check first before passing into the helper or else
the bpf prog will be rejected.  This behavior is nothing new and
consistent with the current expectation during bpf-prog-load.

[ ARG_PTR_TO_BTF_ID_SOCK_COMMON will be used to replace
  ARG_PTR_TO_SOCK* of other existing helpers later such that
  those existing helpers can take the PTR_TO_BTF_ID returned by
  the bpf_skc_to_*() helpers.

  The only special case is bpf_sk_lookup_assign() which can accept a
  literal NULL ptr.  It has to be handled specially in another follow
  up patch if there is a need (e.g. by renaming ARG_PTR_TO_SOCKET_OR_NULL
  to ARG_PTR_TO_BTF_ID_SOCK_COMMON_OR_NULL). ]

[ When converting the older helpers that take ARG_PTR_TO_SOCK* in
  the later patch, if the kernel does not support BTF,
  ARG_PTR_TO_BTF_ID_SOCK_COMMON will behave like ARG_PTR_TO_SOCK_COMMON
  because no reg->type could have PTR_TO_BTF_ID in this case.

  It is not a concern for the newer-btf-only helper like the bpf_skc_to_*()
  here though because these helpers must require BTF vmlinux to begin
  with. ]
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200925000350.3855720-1-kafai@fb.com
      1df8f55a
  3. 24 9月, 2020 7 次提交
  5. 22 9月, 2020 5 次提交
  7. 21 9月, 2020 6 次提交
  9. 20 9月, 2020 4 次提交
  11. 19 9月, 2020 12 次提交