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* [PATCH v3] docs: sysctl/kernel: document BPF entries
@ 2020-03-10 21:58 Stephen Kitt
  2020-03-13  1:08 ` Alexei Starovoitov
  0 siblings, 1 reply; 2+ messages in thread
From: Stephen Kitt @ 2020-03-10 21:58 UTC (permalink / raw)
  To: Alexei Starovoitov, Daniel Borkmann, Martin KaFai Lau, Song Liu,
	Yonghong Song, Andrii Nakryiko, bpf
  Cc: linux-doc, linux-kernel, Stephen Kitt

Based on the implementation in kernel/bpf/syscall.c,
kernel/bpf/trampoline.c, include/linux/filter.h, and the documentation
in bpftool-prog.rst.

The section style doesn't match the surrounding sections; it matches
the style of the reworked kernel.rst queued up in docs-next.

Signed-off-by: Stephen Kitt <steve@sk2.org>

    Changes since v2:
    - fixed "will disabled" typo.
    Changes since v1:
    - rebased on bpf-next instead of docs-next.

 Documentation/admin-guide/sysctl/kernel.rst | 24 +++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index def074807cee..9e1417628572 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -174,6 +174,20 @@ See the type_of_loader and ext_loader_ver fields in
 Documentation/x86/boot.rst for additional information.
+Controls whether the kernel should collect statistics on BPF programs
+(total time spent running, number of times run...). Enabling
+statistics causes a slight reduction in performance on each program
+run. The statistics can be seen using ``bpftool``.
+= ===================================
+0 Don't collect statistics (default).
+1 Collect statistics.
+= ===================================
@@ -1123,6 +1137,16 @@ NMI switch that most IA32 servers have fires unknown NMI up, for
 example.  If a system hangs up, try pressing the NMI switch.
+Writing 1 to this entry will disable unprivileged calls to ``bpf()``;
+once disabled, calling ``bpf()`` without ``CAP_SYS_ADMIN`` will return
+Once set, this can't be cleared.

base-commit: 3e7c67d90e3ed2f34fce42699f11b150dd1d3999

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