Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Daniel Borkmann says:

====================
bpf-next 2021-10-02

We've added 85 non-merge commits during the last 15 day(s) which contain
a total of 132 files changed, 13779 insertions(+), 6724 deletions(-).

The main changes are:

1) Massive update on test_bpf.ko coverage for JITs as preparatory work for
   an upcoming MIPS eBPF JIT, from Johan Almbladh.

2) Add a batched interface for RX buffer allocation in AF_XDP buffer pool,
   with driver support for i40e and ice from Magnus Karlsson.

3) Add legacy uprobe support to libbpf to complement recently merged legacy
   kprobe support, from Andrii Nakryiko.

4) Add bpf_trace_vprintk() as variadic printk helper, from Dave Marchevsky.

5) Support saving the register state in verifier when spilling <8byte bounded
   scalar to the stack, from Martin Lau.

6) Add libbpf opt-in for stricter BPF program section name handling as part
   of libbpf 1.0 effort, from Andrii Nakryiko.

7) Add a document to help clarifying BPF licensing, from Alexei Starovoitov.

8) Fix skel_internal.h to propagate errno if the loader indicates an internal
   error, from Kumar Kartikeya Dwivedi.

9) Fix build warnings with -Wcast-function-type so that the option can later
   be enabled by default for the kernel, from Kees Cook.

10) Fix libbpf to ignore STT_SECTION symbols in legacy map definitions as it
    otherwise errors out when encountering them, from Toke Høiland-Jørgensen.

11) Teach libbpf to recognize specialized maps (such as for perf RB) and
    internally remove BTF type IDs when creating them, from Hengqi Chen.

12) Various fixes and improvements to BPF selftests.
====================

Link: https://lore.kernel.org/r/20211002001327.15169-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 101 insertions, 0 deletions

diff --git a/Documentation/bpf/bpf_licensing.rst b/Documentation/bpf/bpf_licensing.rst
new file mode 100644
index 000000000000..b19c433f41d2
--- /dev/null
+++ b/Documentation/bpf/bpf_licensing.rst
@@ -0,0 +1,92 @@
+=============
+BPF licensing
+=============
+
+Background
+==========
+
+* Classic BPF was BSD licensed
+
+"BPF" was originally introduced as BSD Packet Filter in
+http://www.tcpdump.org/papers/bpf-usenix93.pdf. The corresponding instruction
+set and its implementation came from BSD with BSD license. That original
+instruction set is now known as "classic BPF".
+
+However an instruction set is a specification for machine-language interaction,
+similar to a programming language.  It is not a code. Therefore, the
+application of a BSD license may be misleading in a certain context, as the
+instruction set may enjoy no copyright protection.
+
+* eBPF (extended BPF) instruction set continues to be BSD
+
+In 2014, the classic BPF instruction set was significantly extended. We
+typically refer to this instruction set as eBPF to disambiguate it from cBPF.
+The eBPF instruction set is still BSD licensed.
+
+Implementations of eBPF
+=======================
+
+Using the eBPF instruction set requires implementing code in both kernel space
+and user space.
+
+In Linux Kernel
+---------------
+
+The reference implementations of the eBPF interpreter and various just-in-time
+compilers are part of Linux and are GPLv2 licensed. The implementation of
+eBPF helper functions is also GPLv2 licensed. Interpreters, JITs, helpers,
+and verifiers are called eBPF runtime.
+
+In User Space
+-------------
+
+There are also implementations of eBPF runtime (interpreter, JITs, helper
+functions) under
+Apache2 (https://github.com/iovisor/ubpf),
+MIT (https://github.com/qmonnet/rbpf), and
+BSD (https://github.com/DPDK/dpdk/blob/main/lib/librte_bpf).
+
+In HW
+-----
+
+The HW can choose to execute eBPF instruction natively and provide eBPF runtime
+in HW or via the use of implementing firmware with a proprietary license.
+
+In other operating systems
+--------------------------
+
+Other kernels or user space implementations of eBPF instruction set and runtime
+can have proprietary licenses.
+
+Using BPF programs in the Linux kernel
+======================================
+
+Linux Kernel (while being GPLv2) allows linking of proprietary kernel modules
+under these rules:
+Documentation/process/license-rules.rst
+
+When a kernel module is loaded, the linux kernel checks which functions it
+intends to use. If any function is marked as "GPL only," the corresponding
+module or program has to have GPL compatible license.
+
+Loading BPF program into the Linux kernel is similar to loading a kernel
+module. BPF is loaded at run time and not statically linked to the Linux
+kernel. BPF program loading follows the same license checking rules as kernel
+modules. BPF programs can be proprietary if they don't use "GPL only" BPF
+helper functions.
+
+Further, some BPF program types - Linux Security Modules (LSM) and TCP
+Congestion Control (struct_ops), as of Aug 2021 - are required to be GPL
+compatible even if they don't use "GPL only" helper functions directly. The
+registration step of LSM and TCP congestion control modules of the Linux
+kernel is done through EXPORT_SYMBOL_GPL kernel functions. In that sense LSM
+and struct_ops BPF programs are implicitly calling "GPL only" functions.
+The same restriction applies to BPF programs that call kernel functions
+directly via unstable interface also known as "kfunc".
+
+Packaging BPF programs with user space applications
+====================================================
+
+Generally, proprietary-licensed applications and GPL licensed BPF programs
+written for the Linux kernel in the same package can co-exist because they are
+separate executable processes. This applies to both cBPF and eBPF programs.
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 1ceb5d704a97..37f273a7e8b6 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -82,6 +82,15 @@ Testing and debugging BPF
    s390
 
 
+Licensing
+=========
+
+.. toctree::
+   :maxdepth: 1
+
+   bpf_licensing
+
+
 Other
 =====