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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 01:45:27 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 01:45:27 +0300
commitb23c4771ff62de8ca9b5e4a2d64491b2fb6f8f69 (patch)
tree3ff6b2bdfec161fbc383bba06bab6329e81b02f7 /Documentation/admin-guide/sysctl
parentc2b0fc847f3122e5a4176c3772626a7a8facced0 (diff)
parente35b5a4c494a75a683ddf4901a43e0a128d5bfe3 (diff)
downloadlinux-b23c4771ff62de8ca9b5e4a2d64491b2fb6f8f69.tar.xz
Merge tag 'docs-5.8' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet: "A fair amount of stuff this time around, dominated by yet another massive set from Mauro toward the completion of the RST conversion. I *really* hope we are getting close to the end of this. Meanwhile, those patches reach pretty far afield to update document references around the tree; there should be no actual code changes there. There will be, alas, more of the usual trivial merge conflicts. Beyond that we have more translations, improvements to the sphinx scripting, a number of additions to the sysctl documentation, and lots of fixes" * tag 'docs-5.8' of git://git.lwn.net/linux: (130 commits) Documentation: fixes to the maintainer-entry-profile template zswap: docs/vm: Fix typo accept_threshold_percent in zswap.rst tracing: Fix events.rst section numbering docs: acpi: fix old http link and improve document format docs: filesystems: add info about efivars content Documentation: LSM: Correct the basic LSM description mailmap: change email for Ricardo Ribalda docs: sysctl/kernel: document unaligned controls Documentation: admin-guide: update bug-hunting.rst docs: sysctl/kernel: document ngroups_max nvdimm: fixes to maintainter-entry-profile Documentation/features: Correct RISC-V kprobes support entry Documentation/features: Refresh the arch support status files Revert "docs: sysctl/kernel: document ngroups_max" docs: move locking-specific documents to locking/ docs: move digsig docs to the security book docs: move the kref doc into the core-api book docs: add IRQ documentation at the core-api book docs: debugging-via-ohci1394.txt: add it to the core-api book docs: fix references for ipmi.rst file ...
Diffstat (limited to 'Documentation/admin-guide/sysctl')
-rw-r--r--Documentation/admin-guide/sysctl/kernel.rst157
1 files changed, 156 insertions, 1 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 8d25892a18f8..1ebf68d01141 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -102,6 +102,30 @@ 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.
+= ===================================
+
+
+cad_pid
+=======
+
+This is the pid which will be signalled on reboot (notably, by
+Ctrl-Alt-Delete). Writing a value to this file which doesn't
+correspond to a running process will result in ``-ESRCH``.
+
+See also `ctrl-alt-del`_.
+
+
cap_last_cap
============
@@ -241,6 +265,40 @@ domain names are in general different. For a detailed discussion
see the ``hostname(1)`` man page.
+firmware_config
+===============
+
+See :doc:`/driver-api/firmware/fallback-mechanisms`.
+
+The entries in this directory allow the firmware loader helper
+fallback to be controlled:
+
+* ``force_sysfs_fallback``, when set to 1, forces the use of the
+ fallback;
+* ``ignore_sysfs_fallback``, when set to 1, ignores any fallback.
+
+
+ftrace_dump_on_oops
+===================
+
+Determines whether ``ftrace_dump()`` should be called on an oops (or
+kernel panic). This will output the contents of the ftrace buffers to
+the console. This is very useful for capturing traces that lead to
+crashes and outputting them to a serial console.
+
+= ===================================================
+0 Disabled (default).
+1 Dump buffers of all CPUs.
+2 Dump the buffer of the CPU that triggered the oops.
+= ===================================================
+
+
+ftrace_enabled, stack_tracer_enabled
+====================================
+
+See :doc:`/trace/ftrace`.
+
+
hardlockup_all_cpu_backtrace
============================
@@ -344,6 +402,25 @@ Controls whether the panic kmsg data should be reported to Hyper-V.
= =========================================================
+ignore-unaligned-usertrap
+=========================
+
+On architectures where unaligned accesses cause traps, and where this
+feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN``;
+currently, ``arc`` and ``ia64``), controls whether all unaligned traps
+are logged.
+
+= =============================================================
+0 Log all unaligned accesses.
+1 Only warn the first time a process traps. This is the default
+ setting.
+= =============================================================
+
+See also `unaligned-trap`_ and `unaligned-dump-stack`_. On ``ia64``,
+this allows system administrators to override the
+``IA64_THREAD_UAC_NOPRINT`` ``prctl`` and avoid logs being flooded.
+
+
kexec_load_disabled
===================
@@ -459,6 +536,15 @@ Notes:
successful IPC object allocation. If an IPC object allocation syscall
fails, it is undefined if the value remains unmodified or is reset to -1.
+
+ngroups_max
+===========
+
+Maximum number of supplementary groups, _i.e._ the maximum size which
+``setgroups`` will accept. Exports ``NGROUPS_MAX`` from the kernel.
+
+
+
nmi_watchdog
============
@@ -877,7 +963,7 @@ this sysctl interface anymore.
pty
===
-See Documentation/filesystems/devpts.txt.
+See Documentation/filesystems/devpts.rst.
randomize_va_space
@@ -1173,6 +1259,65 @@ If a value outside of this range is written to ``threads-max`` an
``EINVAL`` error occurs.
+traceoff_on_warning
+===================
+
+When set, disables tracing (see :doc:`/trace/ftrace`) when a
+``WARN()`` is hit.
+
+
+tracepoint_printk
+=================
+
+When tracepoints are sent to printk() (enabled by the ``tp_printk``
+boot parameter), this entry provides runtime control::
+
+ echo 0 > /proc/sys/kernel/tracepoint_printk
+
+will stop tracepoints from being sent to printk(), and::
+
+ echo 1 > /proc/sys/kernel/tracepoint_printk
+
+will send them to printk() again.
+
+This only works if the kernel was booted with ``tp_printk`` enabled.
+
+See :doc:`/admin-guide/kernel-parameters` and
+:doc:`/trace/boottime-trace`.
+
+
+.. _unaligned-dump-stack:
+
+unaligned-dump-stack (ia64)
+===========================
+
+When logging unaligned accesses, controls whether the stack is
+dumped.
+
+= ===================================================
+0 Do not dump the stack. This is the default setting.
+1 Dump the stack.
+= ===================================================
+
+See also `ignore-unaligned-usertrap`_.
+
+
+unaligned-trap
+==============
+
+On architectures where unaligned accesses cause traps, and where this
+feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW``; currently,
+``arc`` and ``parisc``), controls whether unaligned traps are caught
+and emulated (instead of failing).
+
+= ========================================================
+0 Do not emulate unaligned accesses.
+1 Emulate unaligned accesses. This is the default setting.
+= ========================================================
+
+See also `ignore-unaligned-usertrap`_.
+
+
unknown_nmi_panic
=================
@@ -1184,6 +1329,16 @@ 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
========