netdev - [PATCH bpf 1/2] bpf, doc: update design qa to reflect kern

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Message-Id: <20190107215718.2902-2-daniel@iogearbox.net>
Date:   Mon,  7 Jan 2019 22:57:17 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     ast@...nel.org
Cc:     netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf 1/2] bpf, doc: update design qa to reflect kern_version requirement

Update the bpf_design_QA.rst to also reflect recent changes in
6c4fc209fcf9 ("bpf: remove useless version check for prog load").

Suggested-by: Quentin Monnet <quentin.monnet@...ronome.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Alexei Starovoitov <ast@...nel.org>
---
 Documentation/bpf/bpf_design_QA.rst | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst
index 6780a6d..7cc9e36 100644
--- a/Documentation/bpf/bpf_design_QA.rst
+++ b/Documentation/bpf/bpf_design_QA.rst
@@ -157,12 +157,11 @@ Q: Does BPF have a stable ABI?
 ------------------------------
 A: YES. BPF instructions, arguments to BPF programs, set of helper
 functions and their arguments, recognized return codes are all part
-of ABI. However when tracing programs are using bpf_probe_read() helper
-to walk kernel internal datastructures and compile with kernel
-internal headers these accesses can and will break with newer
-kernels. The union bpf_attr -> kern_version is checked at load time
-to prevent accidentally loading kprobe-based bpf programs written
-for a different kernel. Networking programs don't do kern_version check.
+of ABI. However there is one specific exception to tracing programs
+which are using helpers like bpf_probe_read() to walk kernel internal
+data structures and compile with kernel internal headers. Both of these
+kernel internals are subject to change and can break with newer kernels
+such that the program needs to be adapted accordingly.
 
 Q: How much stack space a BPF program uses?
 -------------------------------------------
-- 
2.9.5