[PATCH v4] docs: sysctl/kernel: document BPF entries

[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.

Signed-off-by: Stephen Kitt <steve@xxxxxxx>
---

Notes:
    This patch is intended for docs-next, but I'd appreciate reviews from
    BPF developers.
    
    Changes since v3:
    - moved back to docs-next.
    
    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 335696d3360d..88c51c0a5ce6 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -102,6 +102,20 @@ See the ``type_of_loader`` and ``ext_loader_ver`` fields in
 :doc:`/x86/boot` for additional information.
 
 
+bpf_stats_enabled
+=================
+
+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.
+= ===================================
+
+
 cap_last_cap
 ============
 
@@ -1166,6 +1180,16 @@ NMI switch that most IA32 servers have fires unknown NMI up, for
 example.  If a system hangs up, try pressing the NMI switch.
 
 
+unprivileged_bpf_disabled
+=========================
+
+Writing 1 to this entry will disable unprivileged calls to ``bpf()``;
+once disabled, calling ``bpf()`` without ``CAP_SYS_ADMIN`` will return
+``-EPERM``.
+
+Once set, this can't be cleared.
+
+
 watchdog
 ========
 

base-commit: 7d3d3254adaa61cba896f71497f56901deb618e5
-- 
2.20.1