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Diffstat (limited to 'Documentation/admin-guide/sysctl/kernel.rst')
| -rw-r--r-- | Documentation/admin-guide/sysctl/kernel.rst | 173 |
1 files changed, 167 insertions, 6 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 0d427fd10941..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 ============ @@ -721,7 +807,13 @@ perf_event_paranoid =================== Controls use of the performance events system by unprivileged -users (without CAP_SYS_ADMIN). The default value is 2. +users (without CAP_PERFMON). The default value is 2. + +For backward compatibility reasons access to system performance +monitoring and observability remains open for CAP_SYS_ADMIN +privileged processes but CAP_SYS_ADMIN usage for secure system +performance monitoring and observability operations is discouraged +with respect to CAP_PERFMON use cases. === ================================================================== -1 Allow use of (almost) all events by all users. @@ -730,13 +822,13 @@ users (without CAP_SYS_ADMIN). The default value is 2. ``CAP_IPC_LOCK``. >=0 Disallow ftrace function tracepoint by users without - ``CAP_SYS_ADMIN``. + ``CAP_PERFMON``. - Disallow raw tracepoint access by users without ``CAP_SYS_ADMIN``. + Disallow raw tracepoint access by users without ``CAP_PERFMON``. ->=1 Disallow CPU event access by users without ``CAP_SYS_ADMIN``. +>=1 Disallow CPU event access by users without ``CAP_PERFMON``. ->=2 Disallow kernel profiling by users without ``CAP_SYS_ADMIN``. +>=2 Disallow kernel profiling by users without ``CAP_PERFMON``. === ================================================================== @@ -871,7 +963,7 @@ this sysctl interface anymore. pty === -See Documentation/filesystems/devpts.txt. +See Documentation/filesystems/devpts.rst. randomize_va_space @@ -1167,6 +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 ================= @@ -1178,6 +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 ======== |