path: root/init/Kconfig (plain)
blob: d505d9067c898409487739c831cfcff50a1a4693

1	config ARCH
2	string
3	option env="ARCH"
4
5	config KERNELVERSION
6	string
7	option env="KERNELVERSION"
8
9	config DEFCONFIG_LIST
10	string
11	depends on !UML
12	option defconfig_list
13	default "/lib/modules/$UNAME_RELEASE/.config"
14	default "/etc/kernel-config"
15	default "/boot/config-$UNAME_RELEASE"
16	default "$ARCH_DEFCONFIG"
17	default "arch/$ARCH/defconfig"
18
19	config CONSTRUCTORS
20	bool
21	depends on !UML
22
23	config IRQ_WORK
24	bool
25
26	config BUILDTIME_EXTABLE_SORT
27	bool
28
29	config THREAD_INFO_IN_TASK
30	bool
31	help
32	Select this to move thread_info off the stack into task_struct. To
33	make this work, an arch will need to remove all thread_info fields
34	except flags and fix any runtime bugs.
35
36	One subtle change that will be needed is to use try_get_task_stack()
37	and put_task_stack() in save_thread_stack_tsk() and get_wchan().
38
39	menu "General setup"
40
41	config BROKEN
42	bool
43
44	config BROKEN_ON_SMP
45	bool
46	depends on BROKEN || !SMP
47	default y
48
49	config INIT_ENV_ARG_LIMIT
50	int
51	default 32 if !UML
52	default 128 if UML
53	help
54	Maximum of each of the number of arguments and environment
55	variables passed to init from the kernel command line.
56
57
58	config CROSS_COMPILE
59	string "Cross-compiler tool prefix"
60	help
61	Same as running 'make CROSS_COMPILE=prefix-' but stored for
62	default make runs in this kernel build directory. You don't
63	need to set this unless you want the configured kernel build
64	directory to select the cross-compiler automatically.
65
66	config COMPILE_TEST
67	bool "Compile also drivers which will not load"
68	depends on !UML
69	default n
70	help
71	Some drivers can be compiled on a different platform than they are
72	intended to be run on. Despite they cannot be loaded there (or even
73	when they load they cannot be used due to missing HW support),
74	developers still, opposing to distributors, might want to build such
75	drivers to compile-test them.
76
77	If you are a developer and want to build everything available, say Y
78	here. If you are a user/distributor, say N here to exclude useless
79	drivers to be distributed.
80
81	config LOCALVERSION
82	string "Local version - append to kernel release"
83	help
84	Append an extra string to the end of your kernel version.
85	This will show up when you type uname, for example.
86	The string you set here will be appended after the contents of
87	any files with a filename matching localversion* in your
88	object and source tree, in that order. Your total string can
89	be a maximum of 64 characters.
90
91	config LOCALVERSION_AUTO
92	bool "Automatically append version information to the version string"
93	default y
94	depends on !COMPILE_TEST
95	help
96	This will try to automatically determine if the current tree is a
97	release tree by looking for git tags that belong to the current
98	top of tree revision.
99
100	A string of the format -gxxxxxxxx will be added to the localversion
101	if a git-based tree is found. The string generated by this will be
102	appended after any matching localversion* files, and after the value
103	set in CONFIG_LOCALVERSION.
104
105	(The actual string used here is the first eight characters produced
106	by running the command:
107
108	$ git rev-parse --verify HEAD
109
110	which is done within the script "scripts/setlocalversion".)
111
112	config HAVE_KERNEL_GZIP
113	bool
114
115	config HAVE_KERNEL_BZIP2
116	bool
117
118	config HAVE_KERNEL_LZMA
119	bool
120
121	config HAVE_KERNEL_XZ
122	bool
123
124	config HAVE_KERNEL_LZO
125	bool
126
127	config HAVE_KERNEL_LZ4
128	bool
129
130	choice
131	prompt "Kernel compression mode"
132	default KERNEL_GZIP
133	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
134	help
135	The linux kernel is a kind of self-extracting executable.
136	Several compression algorithms are available, which differ
137	in efficiency, compression and decompression speed.
138	Compression speed is only relevant when building a kernel.
139	Decompression speed is relevant at each boot.
140
141	If you have any problems with bzip2 or lzma compressed
142	kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
143	version of this functionality (bzip2 only), for 2.4, was
144	supplied by Christian Ludwig)
145
146	High compression options are mostly useful for users, who
147	are low on disk space (embedded systems), but for whom ram
148	size matters less.
149
150	If in doubt, select 'gzip'
151
152	config KERNEL_GZIP
153	bool "Gzip"
154	depends on HAVE_KERNEL_GZIP
155	help
156	The old and tried gzip compression. It provides a good balance
157	between compression ratio and decompression speed.
158
159	config KERNEL_BZIP2
160	bool "Bzip2"
161	depends on HAVE_KERNEL_BZIP2
162	help
163	Its compression ratio and speed is intermediate.
164	Decompression speed is slowest among the choices. The kernel
165	size is about 10% smaller with bzip2, in comparison to gzip.
166	Bzip2 uses a large amount of memory. For modern kernels you
167	will need at least 8MB RAM or more for booting.
168
169	config KERNEL_LZMA
170	bool "LZMA"
171	depends on HAVE_KERNEL_LZMA
172	help
173	This compression algorithm's ratio is best. Decompression speed
174	is between gzip and bzip2. Compression is slowest.
175	The kernel size is about 33% smaller with LZMA in comparison to gzip.
176
177	config KERNEL_XZ
178	bool "XZ"
179	depends on HAVE_KERNEL_XZ
180	help
181	XZ uses the LZMA2 algorithm and instruction set specific
182	BCJ filters which can improve compression ratio of executable
183	code. The size of the kernel is about 30% smaller with XZ in
184	comparison to gzip. On architectures for which there is a BCJ
185	filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
186	will create a few percent smaller kernel than plain LZMA.
187
188	The speed is about the same as with LZMA: The decompression
189	speed of XZ is better than that of bzip2 but worse than gzip
190	and LZO. Compression is slow.
191
192	config KERNEL_LZO
193	bool "LZO"
194	depends on HAVE_KERNEL_LZO
195	help
196	Its compression ratio is the poorest among the choices. The kernel
197	size is about 10% bigger than gzip; however its speed
198	(both compression and decompression) is the fastest.
199
200	config KERNEL_LZ4
201	bool "LZ4"
202	depends on HAVE_KERNEL_LZ4
203	help
204	LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
205	A preliminary version of LZ4 de/compression tool is available at
206	<https://code.google.com/p/lz4/>.
207
208	Its compression ratio is worse than LZO. The size of the kernel
209	is about 8% bigger than LZO. But the decompression speed is
210	faster than LZO.
211
212	endchoice
213
214	config DEFAULT_HOSTNAME
215	string "Default hostname"
216	default "(none)"
217	help
218	This option determines the default system hostname before userspace
219	calls sethostname(2). The kernel traditionally uses "(none)" here,
220	but you may wish to use a different default here to make a minimal
221	system more usable with less configuration.
222
223	config SWAP
224	bool "Support for paging of anonymous memory (swap)"
225	depends on MMU && BLOCK
226	default y
227	help
228	This option allows you to choose whether you want to have support
229	for so called swap devices or swap files in your kernel that are
230	used to provide more virtual memory than the actual RAM present
231	in your computer. If unsure say Y.
232
233	config SYSVIPC
234	bool "System V IPC"
235	---help---
236	Inter Process Communication is a suite of library functions and
237	system calls which let processes (running programs) synchronize and
238	exchange information. It is generally considered to be a good thing,
239	and some programs won't run unless you say Y here. In particular, if
240	you want to run the DOS emulator dosemu under Linux (read the
241	DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
242	you'll need to say Y here.
243
244	You can find documentation about IPC with "info ipc" and also in
245	section 6.4 of the Linux Programmer's Guide, available from
246	<http://www.tldp.org/guides.html>.
247
248	config SYSVIPC_SYSCTL
249	bool
250	depends on SYSVIPC
251	depends on SYSCTL
252	default y
253
254	config POSIX_MQUEUE
255	bool "POSIX Message Queues"
256	depends on NET
257	---help---
258	POSIX variant of message queues is a part of IPC. In POSIX message
259	queues every message has a priority which decides about succession
260	of receiving it by a process. If you want to compile and run
261	programs written e.g. for Solaris with use of its POSIX message
262	queues (functions mq_*) say Y here.
263
264	POSIX message queues are visible as a filesystem called 'mqueue'
265	and can be mounted somewhere if you want to do filesystem
266	operations on message queues.
267
268	If unsure, say Y.
269
270	config POSIX_MQUEUE_SYSCTL
271	bool
272	depends on POSIX_MQUEUE
273	depends on SYSCTL
274	default y
275
276	config CROSS_MEMORY_ATTACH
277	bool "Enable process_vm_readv/writev syscalls"
278	depends on MMU
279	default y
280	help
281	Enabling this option adds the system calls process_vm_readv and
282	process_vm_writev which allow a process with the correct privileges
283	to directly read from or write to another process' address space.
284	See the man page for more details.
285
286	config FHANDLE
287	bool "open by fhandle syscalls" if EXPERT
288	select EXPORTFS
289	default y
290	help
291	If you say Y here, a user level program will be able to map
292	file names to handle and then later use the handle for
293	different file system operations. This is useful in implementing
294	userspace file servers, which now track files using handles instead
295	of names. The handle would remain the same even if file names
296	get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
297	syscalls.
298
299	config USELIB
300	bool "uselib syscall"
301	def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
302	help
303	This option enables the uselib syscall, a system call used in the
304	dynamic linker from libc5 and earlier. glibc does not use this
305	system call. If you intend to run programs built on libc5 or
306	earlier, you may need to enable this syscall. Current systems
307	running glibc can safely disable this.
308
309	config AUDIT
310	bool "Auditing support"
311	depends on NET
312	help
313	Enable auditing infrastructure that can be used with another
314	kernel subsystem, such as SELinux (which requires this for
315	logging of avc messages output). System call auditing is included
316	on architectures which support it.
317
318	config HAVE_ARCH_AUDITSYSCALL
319	bool
320
321	config AUDITSYSCALL
322	def_bool y
323	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
324
325	config AUDIT_WATCH
326	def_bool y
327	depends on AUDITSYSCALL
328	select FSNOTIFY
329
330	config AUDIT_TREE
331	def_bool y
332	depends on AUDITSYSCALL
333	select FSNOTIFY
334
335	source "kernel/irq/Kconfig"
336	source "kernel/time/Kconfig"
337
338	menu "CPU/Task time and stats accounting"
339
340	config VIRT_CPU_ACCOUNTING
341	bool
342
343	choice
344	prompt "Cputime accounting"
345	default TICK_CPU_ACCOUNTING if !PPC64
346	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
347
348	# Kind of a stub config for the pure tick based cputime accounting
349	config TICK_CPU_ACCOUNTING
350	bool "Simple tick based cputime accounting"
351	depends on !S390 && !NO_HZ_FULL
352	help
353	This is the basic tick based cputime accounting that maintains
354	statistics about user, system and idle time spent on per jiffies
355	granularity.
356
357	If unsure, say Y.
358
359	config VIRT_CPU_ACCOUNTING_NATIVE
360	bool "Deterministic task and CPU time accounting"
361	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
362	select VIRT_CPU_ACCOUNTING
363	help
364	Select this option to enable more accurate task and CPU time
365	accounting. This is done by reading a CPU counter on each
366	kernel entry and exit and on transitions within the kernel
367	between system, softirq and hardirq state, so there is a
368	small performance impact. In the case of s390 or IBM POWER > 5,
369	this also enables accounting of stolen time on logically-partitioned
370	systems.
371
372	config VIRT_CPU_ACCOUNTING_GEN
373	bool "Full dynticks CPU time accounting"
374	depends on HAVE_CONTEXT_TRACKING
375	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
376	select VIRT_CPU_ACCOUNTING
377	select CONTEXT_TRACKING
378	help
379	Select this option to enable task and CPU time accounting on full
380	dynticks systems. This accounting is implemented by watching every
381	kernel-user boundaries using the context tracking subsystem.
382	The accounting is thus performed at the expense of some significant
383	overhead.
384
385	For now this is only useful if you are working on the full
386	dynticks subsystem development.
387
388	If unsure, say N.
389
390	endchoice
391
392	config IRQ_TIME_ACCOUNTING
393	bool "Fine granularity task level IRQ time accounting"
394	depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
395	help
396	Select this option to enable fine granularity task irq time
397	accounting. This is done by reading a timestamp on each
398	transitions between softirq and hardirq state, so there can be a
399	small performance impact.
400
401	If in doubt, say N here.
402
403	config SCHED_WALT
404	bool "Support window based load tracking"
405	depends on SMP
406	help
407	This feature will allow the scheduler to maintain a tunable window
408	based set of metrics for tasks and runqueues. These metrics can be
409	used to guide task placement as well as task frequency requirements
410	for cpufreq governors.
411
412	config BSD_PROCESS_ACCT
413	bool "BSD Process Accounting"
414	depends on MULTIUSER
415	help
416	If you say Y here, a user level program will be able to instruct the
417	kernel (via a special system call) to write process accounting
418	information to a file: whenever a process exits, information about
419	that process will be appended to the file by the kernel. The
420	information includes things such as creation time, owning user,
421	command name, memory usage, controlling terminal etc. (the complete
422	list is in the struct acct in <file:include/linux/acct.h>). It is
423	up to the user level program to do useful things with this
424	information. This is generally a good idea, so say Y.
425
426	config BSD_PROCESS_ACCT_V3
427	bool "BSD Process Accounting version 3 file format"
428	depends on BSD_PROCESS_ACCT
429	default n
430	help
431	If you say Y here, the process accounting information is written
432	in a new file format that also logs the process IDs of each
433	process and it's parent. Note that this file format is incompatible
434	with previous v0/v1/v2 file formats, so you will need updated tools
435	for processing it. A preliminary version of these tools is available
436	at <http://www.gnu.org/software/acct/>.
437
438	config TASKSTATS
439	bool "Export task/process statistics through netlink"
440	depends on NET
441	depends on MULTIUSER
442	default n
443	help
444	Export selected statistics for tasks/processes through the
445	generic netlink interface. Unlike BSD process accounting, the
446	statistics are available during the lifetime of tasks/processes as
447	responses to commands. Like BSD accounting, they are sent to user
448	space on task exit.
449
450	Say N if unsure.
451
452	config TASK_DELAY_ACCT
453	bool "Enable per-task delay accounting"
454	depends on TASKSTATS
455	select SCHED_INFO
456	help
457	Collect information on time spent by a task waiting for system
458	resources like cpu, synchronous block I/O completion and swapping
459	in pages. Such statistics can help in setting a task's priorities
460	relative to other tasks for cpu, io, rss limits etc.
461
462	Say N if unsure.
463
464	config TASK_XACCT
465	bool "Enable extended accounting over taskstats"
466	depends on TASKSTATS
467	help
468	Collect extended task accounting data and send the data
469	to userland for processing over the taskstats interface.
470
471	Say N if unsure.
472
473	config TASK_IO_ACCOUNTING
474	bool "Enable per-task storage I/O accounting"
475	depends on TASK_XACCT
476	help
477	Collect information on the number of bytes of storage I/O which this
478	task has caused.
479
480	Say N if unsure.
481
482	config PSI
483	bool "Pressure stall information tracking"
484	help
485	Collect metrics that indicate how overcommitted the CPU, memory,
486	and IO capacity are in the system.
487
488	If you say Y here, the kernel will create /proc/pressure/ with the
489	pressure statistics files cpu, memory, and io. These will indicate
490	the share of walltime in which some or all tasks in the system are
491	delayed due to contention of the respective resource.
492
493	In kernels with cgroup support, cgroups (cgroup2 only) will
494	have cpu.pressure, memory.pressure, and io.pressure files,
495	which aggregate pressure stalls for the grouped tasks only.
496
497	For more details see Documentation/accounting/psi.txt.
498
499	Say N if unsure.
500
501	config PSI_DEFAULT_DISABLED
502	bool "Require boot parameter to enable pressure stall information tracking"
503	default n
504	depends on PSI
505	help
506	If set, pressure stall information tracking will be disabled
507	per default but can be enabled through passing psi=1 on the
508	kernel commandline during boot.
509
510	This feature adds some code to the task wakeup and sleep
511	paths of the scheduler. The overhead is too low to affect
512	common scheduling-intense workloads in practice (such as
513	webservers, memcache), but it does show up in artificial
514	scheduler stress tests, such as hackbench.
515
516	If you are paranoid and not sure what the kernel will be
517	used for, say Y.
518
519	Say N if unsure.
520
521	endmenu # "CPU/Task time and stats accounting"
522
523	menu "RCU Subsystem"
524
525	config TREE_RCU
526	bool
527	default y if !PREEMPT && SMP
528	help
529	This option selects the RCU implementation that is
530	designed for very large SMP system with hundreds or
531	thousands of CPUs. It also scales down nicely to
532	smaller systems.
533
534	config PREEMPT_RCU
535	bool
536	default y if PREEMPT
537	help
538	This option selects the RCU implementation that is
539	designed for very large SMP systems with hundreds or
540	thousands of CPUs, but for which real-time response
541	is also required. It also scales down nicely to
542	smaller systems.
543
544	Select this option if you are unsure.
545
546	config TINY_RCU
547	bool
548	default y if !PREEMPT && !SMP
549	help
550	This option selects the RCU implementation that is
551	designed for UP systems from which real-time response
552	is not required. This option greatly reduces the
553	memory footprint of RCU.
554
555	config RCU_EXPERT
556	bool "Make expert-level adjustments to RCU configuration"
557	default n
558	help
559	This option needs to be enabled if you wish to make
560	expert-level adjustments to RCU configuration. By default,
561	no such adjustments can be made, which has the often-beneficial
562	side-effect of preventing "make oldconfig" from asking you all
563	sorts of detailed questions about how you would like numerous
564	obscure RCU options to be set up.
565
566	Say Y if you need to make expert-level adjustments to RCU.
567
568	Say N if you are unsure.
569
570	config SRCU
571	bool
572	help
573	This option selects the sleepable version of RCU. This version
574	permits arbitrary sleeping or blocking within RCU read-side critical
575	sections.
576
577	config TASKS_RCU
578	bool
579	default n
580	depends on !UML
581	select SRCU
582	help
583	This option enables a task-based RCU implementation that uses
584	only voluntary context switch (not preemption!), idle, and
585	user-mode execution as quiescent states.
586
587	config RCU_STALL_COMMON
588	def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
589	help
590	This option enables RCU CPU stall code that is common between
591	the TINY and TREE variants of RCU. The purpose is to allow
592	the tiny variants to disable RCU CPU stall warnings, while
593	making these warnings mandatory for the tree variants.
594
595	config CONTEXT_TRACKING
596	bool
597
598	config CONTEXT_TRACKING_FORCE
599	bool "Force context tracking"
600	depends on CONTEXT_TRACKING
601	default y if !NO_HZ_FULL
602	help
603	The major pre-requirement for full dynticks to work is to
604	support the context tracking subsystem. But there are also
605	other dependencies to provide in order to make the full
606	dynticks working.
607
608	This option stands for testing when an arch implements the
609	context tracking backend but doesn't yet fullfill all the
610	requirements to make the full dynticks feature working.
611	Without the full dynticks, there is no way to test the support
612	for context tracking and the subsystems that rely on it: RCU
613	userspace extended quiescent state and tickless cputime
614	accounting. This option copes with the absence of the full
615	dynticks subsystem by forcing the context tracking on all
616	CPUs in the system.
617
618	Say Y only if you're working on the development of an
619	architecture backend for the context tracking.
620
621	Say N otherwise, this option brings an overhead that you
622	don't want in production.
623
624
625	config RCU_FANOUT
626	int "Tree-based hierarchical RCU fanout value"
627	range 2 64 if 64BIT
628	range 2 32 if !64BIT
629	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
630	default 64 if 64BIT
631	default 32 if !64BIT
632	help
633	This option controls the fanout of hierarchical implementations
634	of RCU, allowing RCU to work efficiently on machines with
635	large numbers of CPUs. This value must be at least the fourth
636	root of NR_CPUS, which allows NR_CPUS to be insanely large.
637	The default value of RCU_FANOUT should be used for production
638	systems, but if you are stress-testing the RCU implementation
639	itself, small RCU_FANOUT values allow you to test large-system
640	code paths on small(er) systems.
641
642	Select a specific number if testing RCU itself.
643	Take the default if unsure.
644
645	config RCU_FANOUT_LEAF
646	int "Tree-based hierarchical RCU leaf-level fanout value"
647	range 2 64 if 64BIT
648	range 2 32 if !64BIT
649	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
650	default 16
651	help
652	This option controls the leaf-level fanout of hierarchical
653	implementations of RCU, and allows trading off cache misses
654	against lock contention. Systems that synchronize their
655	scheduling-clock interrupts for energy-efficiency reasons will
656	want the default because the smaller leaf-level fanout keeps
657	lock contention levels acceptably low. Very large systems
658	(hundreds or thousands of CPUs) will instead want to set this
659	value to the maximum value possible in order to reduce the
660	number of cache misses incurred during RCU's grace-period
661	initialization. These systems tend to run CPU-bound, and thus
662	are not helped by synchronized interrupts, and thus tend to
663	skew them, which reduces lock contention enough that large
664	leaf-level fanouts work well.
665
666	Select a specific number if testing RCU itself.
667
668	Select the maximum permissible value for large systems.
669
670	Take the default if unsure.
671
672	config RCU_FAST_NO_HZ
673	bool "Accelerate last non-dyntick-idle CPU's grace periods"
674	depends on NO_HZ_COMMON && SMP && RCU_EXPERT
675	default n
676	help
677	This option permits CPUs to enter dynticks-idle state even if
678	they have RCU callbacks queued, and prevents RCU from waking
679	these CPUs up more than roughly once every four jiffies (by
680	default, you can adjust this using the rcutree.rcu_idle_gp_delay
681	parameter), thus improving energy efficiency. On the other
682	hand, this option increases the duration of RCU grace periods,
683	for example, slowing down synchronize_rcu().
684
685	Say Y if energy efficiency is critically important, and you
686	don't care about increased grace-period durations.
687
688	Say N if you are unsure.
689
690	config TREE_RCU_TRACE
691	def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
692	select DEBUG_FS
693	help
694	This option provides tracing for the TREE_RCU and
695	PREEMPT_RCU implementations, permitting Makefile to
696	trivially select kernel/rcutree_trace.c.
697
698	config RCU_BOOST
699	bool "Enable RCU priority boosting"
700	depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
701	default n
702	help
703	This option boosts the priority of preempted RCU readers that
704	block the current preemptible RCU grace period for too long.
705	This option also prevents heavy loads from blocking RCU
706	callback invocation for all flavors of RCU.
707
708	Say Y here if you are working with real-time apps or heavy loads
709	Say N here if you are unsure.
710
711	config RCU_KTHREAD_PRIO
712	int "Real-time priority to use for RCU worker threads"
713	range 1 99 if RCU_BOOST
714	range 0 99 if !RCU_BOOST
715	default 1 if RCU_BOOST
716	default 0 if !RCU_BOOST
717	depends on RCU_EXPERT
718	help
719	This option specifies the SCHED_FIFO priority value that will be
720	assigned to the rcuc/n and rcub/n threads and is also the value
721	used for RCU_BOOST (if enabled). If you are working with a
722	real-time application that has one or more CPU-bound threads
723	running at a real-time priority level, you should set
724	RCU_KTHREAD_PRIO to a priority higher than the highest-priority
725	real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
726	value of 1 is appropriate in the common case, which is real-time
727	applications that do not have any CPU-bound threads.
728
729	Some real-time applications might not have a single real-time
730	thread that saturates a given CPU, but instead might have
731	multiple real-time threads that, taken together, fully utilize
732	that CPU. In this case, you should set RCU_KTHREAD_PRIO to
733	a priority higher than the lowest-priority thread that is
734	conspiring to prevent the CPU from running any non-real-time
735	tasks. For example, if one thread at priority 10 and another
736	thread at priority 5 are between themselves fully consuming
737	the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
738	set to priority 6 or higher.
739
740	Specify the real-time priority, or take the default if unsure.
741
742	config RCU_BOOST_DELAY
743	int "Milliseconds to delay boosting after RCU grace-period start"
744	range 0 3000
745	depends on RCU_BOOST
746	default 500
747	help
748	This option specifies the time to wait after the beginning of
749	a given grace period before priority-boosting preempted RCU
750	readers blocking that grace period. Note that any RCU reader
751	blocking an expedited RCU grace period is boosted immediately.
752
753	Accept the default if unsure.
754
755	config RCU_NOCB_CPU
756	bool "Offload RCU callback processing from boot-selected CPUs"
757	depends on TREE_RCU || PREEMPT_RCU
758	depends on RCU_EXPERT || NO_HZ_FULL
759	default n
760	help
761	Use this option to reduce OS jitter for aggressive HPC or
762	real-time workloads. It can also be used to offload RCU
763	callback invocation to energy-efficient CPUs in battery-powered
764	asymmetric multiprocessors.
765
766	This option offloads callback invocation from the set of
767	CPUs specified at boot time by the rcu_nocbs parameter.
768	For each such CPU, a kthread ("rcuox/N") will be created to
769	invoke callbacks, where the "N" is the CPU being offloaded,
770	and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
771	"s" for RCU-sched. Nothing prevents this kthread from running
772	on the specified CPUs, but (1) the kthreads may be preempted
773	between each callback, and (2) affinity or cgroups can be used
774	to force the kthreads to run on whatever set of CPUs is desired.
775
776	Say Y here if you want to help to debug reduced OS jitter.
777	Say N here if you are unsure.
778
779	choice
780	prompt "Build-forced no-CBs CPUs"
781	default RCU_NOCB_CPU_NONE
782	depends on RCU_NOCB_CPU
783	help
784	This option allows no-CBs CPUs (whose RCU callbacks are invoked
785	from kthreads rather than from softirq context) to be specified
786	at build time. Additional no-CBs CPUs may be specified by
787	the rcu_nocbs= boot parameter.
788
789	config RCU_NOCB_CPU_NONE
790	bool "No build_forced no-CBs CPUs"
791	help
792	This option does not force any of the CPUs to be no-CBs CPUs.
793	Only CPUs designated by the rcu_nocbs= boot parameter will be
794	no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
795	kthreads whose names begin with "rcuo". All other CPUs will
796	invoke their own RCU callbacks in softirq context.
797
798	Select this option if you want to choose no-CBs CPUs at
799	boot time, for example, to allow testing of different no-CBs
800	configurations without having to rebuild the kernel each time.
801
802	config RCU_NOCB_CPU_ZERO
803	bool "CPU 0 is a build_forced no-CBs CPU"
804	help
805	This option forces CPU 0 to be a no-CBs CPU, so that its RCU
806	callbacks are invoked by a per-CPU kthread whose name begins
807	with "rcuo". Additional CPUs may be designated as no-CBs
808	CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
809	All other CPUs will invoke their own RCU callbacks in softirq
810	context.
811
812	Select this if CPU 0 needs to be a no-CBs CPU for real-time
813	or energy-efficiency reasons, but the real reason it exists
814	is to ensure that randconfig testing covers mixed systems.
815
816	config RCU_NOCB_CPU_ALL
817	bool "All CPUs are build_forced no-CBs CPUs"
818	help
819	This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
820	boot parameter will be ignored. All CPUs' RCU callbacks will
821	be executed in the context of per-CPU rcuo kthreads created for
822	this purpose. Assuming that the kthreads whose names start with
823	"rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
824	on the remaining CPUs, but might decrease memory locality during
825	RCU-callback invocation, thus potentially degrading throughput.
826
827	Select this if all CPUs need to be no-CBs CPUs for real-time
828	or energy-efficiency reasons.
829
830	endchoice
831
832	config RCU_EXPEDITE_BOOT
833	bool
834	default n
835	help
836	This option enables expedited grace periods at boot time,
837	as if rcu_expedite_gp() had been invoked early in boot.
838	The corresponding rcu_unexpedite_gp() is invoked from
839	rcu_end_inkernel_boot(), which is intended to be invoked
840	at the end of the kernel-only boot sequence, just before
841	init is exec'ed.
842
843	Accept the default if unsure.
844
845	endmenu # "RCU Subsystem"
846
847	config BUILD_BIN2C
848	bool
849	default n
850
851	config IKCONFIG
852	tristate "Kernel .config support"
853	select BUILD_BIN2C
854	---help---
855	This option enables the complete Linux kernel ".config" file
856	contents to be saved in the kernel. It provides documentation
857	of which kernel options are used in a running kernel or in an
858	on-disk kernel. This information can be extracted from the kernel
859	image file with the script scripts/extract-ikconfig and used as
860	input to rebuild the current kernel or to build another kernel.
861	It can also be extracted from a running kernel by reading
862	/proc/config.gz if enabled (below).
863
864	config IKCONFIG_PROC
865	bool "Enable access to .config through /proc/config.gz"
866	depends on IKCONFIG && PROC_FS
867	---help---
868	This option enables access to the kernel configuration file
869	through /proc/config.gz.
870
871	config LOG_BUF_SHIFT
872	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
873	range 12 25
874	default 17
875	depends on PRINTK
876	help
877	Select the minimal kernel log buffer size as a power of 2.
878	The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
879	parameter, see below. Any higher size also might be forced
880	by "log_buf_len" boot parameter.
881
882	Examples:
883	17 => 128 KB
884	16 => 64 KB
885	15 => 32 KB
886	14 => 16 KB
887	13 => 8 KB
888	12 => 4 KB
889
890	config LOG_CPU_MAX_BUF_SHIFT
891	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
892	depends on SMP
893	range 0 21
894	default 12 if !BASE_SMALL
895	default 0 if BASE_SMALL
896	depends on PRINTK
897	help
898	This option allows to increase the default ring buffer size
899	according to the number of CPUs. The value defines the contribution
900	of each CPU as a power of 2. The used space is typically only few
901	lines however it might be much more when problems are reported,
902	e.g. backtraces.
903
904	The increased size means that a new buffer has to be allocated and
905	the original static one is unused. It makes sense only on systems
906	with more CPUs. Therefore this value is used only when the sum of
907	contributions is greater than the half of the default kernel ring
908	buffer as defined by LOG_BUF_SHIFT. The default values are set
909	so that more than 64 CPUs are needed to trigger the allocation.
910
911	Also this option is ignored when "log_buf_len" kernel parameter is
912	used as it forces an exact (power of two) size of the ring buffer.
913
914	The number of possible CPUs is used for this computation ignoring
915	hotplugging making the computation optimal for the worst case
916	scenario while allowing a simple algorithm to be used from bootup.
917
918	Examples shift values and their meaning:
919	17 => 128 KB for each CPU
920	16 => 64 KB for each CPU
921	15 => 32 KB for each CPU
922	14 => 16 KB for each CPU
923	13 => 8 KB for each CPU
924	12 => 4 KB for each CPU
925
926	config NMI_LOG_BUF_SHIFT
927	int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
928	range 10 21
929	default 13
930	depends on PRINTK_NMI
931	help
932	Select the size of a per-CPU buffer where NMI messages are temporary
933	stored. They are copied to the main log buffer in a safe context
934	to avoid a deadlock. The value defines the size as a power of 2.
935
936	NMI messages are rare and limited. The largest one is when
937	a backtrace is printed. It usually fits into 4KB. Select
938	8KB if you want to be on the safe side.
939
940	Examples:
941	17 => 128 KB for each CPU
942	16 => 64 KB for each CPU
943	15 => 32 KB for each CPU
944	14 => 16 KB for each CPU
945	13 => 8 KB for each CPU
946	12 => 4 KB for each CPU
947
948	#
949	# Architectures with an unreliable sched_clock() should select this:
950	#
951	config HAVE_UNSTABLE_SCHED_CLOCK
952	bool
953
954	config GENERIC_SCHED_CLOCK
955	bool
956
957	#
958	# For architectures that want to enable the support for NUMA-affine scheduler
959	# balancing logic:
960	#
961	config ARCH_SUPPORTS_NUMA_BALANCING
962	bool
963
964	#
965	# For architectures that prefer to flush all TLBs after a number of pages
966	# are unmapped instead of sending one IPI per page to flush. The architecture
967	# must provide guarantees on what happens if a clean TLB cache entry is
968	# written after the unmap. Details are in mm/rmap.c near the check for
969	# should_defer_flush. The architecture should also consider if the full flush
970	# and the refill costs are offset by the savings of sending fewer IPIs.
971	config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
972	bool
973
974	#
975	# For architectures that know their GCC __int128 support is sound
976	#
977	config ARCH_SUPPORTS_INT128
978	bool
979
980	# For architectures that (ab)use NUMA to represent different memory regions
981	# all cpu-local but of different latencies, such as SuperH.
982	#
983	config ARCH_WANT_NUMA_VARIABLE_LOCALITY
984	bool
985
986	config NUMA_BALANCING
987	bool "Memory placement aware NUMA scheduler"
988	depends on ARCH_SUPPORTS_NUMA_BALANCING
989	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
990	depends on SMP && NUMA && MIGRATION
991	help
992	This option adds support for automatic NUMA aware memory/task placement.
993	The mechanism is quite primitive and is based on migrating memory when
994	it has references to the node the task is running on.
995
996	This system will be inactive on UMA systems.
997
998	config NUMA_BALANCING_DEFAULT_ENABLED
999	bool "Automatically enable NUMA aware memory/task placement"
1000	default y
1001	depends on NUMA_BALANCING
1002	help
1003	If set, automatic NUMA balancing will be enabled if running on a NUMA
1004	machine.
1005
1006	menuconfig CGROUPS
1007	bool "Control Group support"
1008	select KERNFS
1009	help
1010	This option adds support for grouping sets of processes together, for
1011	use with process control subsystems such as Cpusets, CFS, memory
1012	controls or device isolation.
1013	See
1014	- Documentation/scheduler/sched-design-CFS.txt (CFS)
1015	- Documentation/cgroup-v1/ (features for grouping, isolation
1016	and resource control)
1017
1018	Say N if unsure.
1019
1020	if CGROUPS
1021
1022	config CGROUP_DEBUG
1023	bool "Example debug cgroup subsystem"
1024	default n
1025	help
1026	This option enables a simple cgroup subsystem that
1027	exports useful debugging information about the cgroups
1028	framework.
1029
1030	Say N if unsure.
1031
1032	config CGROUP_FREEZER
1033	bool "Freezer cgroup subsystem"
1034	help
1035	Provides a way to freeze and unfreeze all tasks in a
1036	cgroup.
1037
1038	config CGROUP_PIDS
1039	bool "PIDs cgroup subsystem"
1040	help
1041	Provides enforcement of process number limits in the scope of a
1042	cgroup. Any attempt to fork more processes than is allowed in the
1043	cgroup will fail. PIDs are fundamentally a global resource because it
1044	is fairly trivial to reach PID exhaustion before you reach even a
1045	conservative kmemcg limit. As a result, it is possible to grind a
1046	system to halt without being limited by other cgroup policies. The
1047	PIDs cgroup subsystem is designed to stop this from happening.
1048
1049	It should be noted that organisational operations (such as attaching
1050	to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
1051	since the PIDs limit only affects a process's ability to fork, not to
1052	attach to a cgroup.
1053
1054	config CGROUP_DEVICE
1055	bool "Device controller for cgroups"
1056	help
1057	Provides a cgroup implementing whitelists for devices which
1058	a process in the cgroup can mknod or open.
1059
1060	config CPUSETS
1061	bool "Cpuset support"
1062	help
1063	This option will let you create and manage CPUSETs which
1064	allow dynamically partitioning a system into sets of CPUs and
1065	Memory Nodes and assigning tasks to run only within those sets.
1066	This is primarily useful on large SMP or NUMA systems.
1067
1068	Say N if unsure.
1069
1070	config PROC_PID_CPUSET
1071	bool "Include legacy /proc/<pid>/cpuset file"
1072	depends on CPUSETS
1073	default y
1074
1075	config CGROUP_CPUACCT
1076	bool "Simple CPU accounting cgroup subsystem"
1077	help
1078	Provides a simple Resource Controller for monitoring the
1079	total CPU consumed by the tasks in a cgroup.
1080
1081	config CGROUP_SCHEDTUNE
1082	bool "CFS tasks boosting cgroup subsystem (EXPERIMENTAL)"
1083	depends on SCHED_TUNE
1084	help
1085	This option provides the "schedtune" controller which improves the
1086	flexibility of the task boosting mechanism by introducing the support
1087	to define "per task" boost values.
1088
1089	This new controller:
1090	1. allows only a two layers hierarchy, where the root defines the
1091	system-wide boost value and its direct childrens define each one a
1092	different "class of tasks" to be boosted with a different value
1093	2. supports up to 16 different task classes, each one which could be
1094	configured with a different boost value
1095
1096	Say N if unsure.
1097
1098	config PAGE_COUNTER
1099	bool
1100
1101	config MEMCG
1102	bool "Memory controller"
1103	select PAGE_COUNTER
1104	select EVENTFD
1105	help
1106	Provides control over the memory footprint of tasks in a cgroup.
1107
1108	config MEMCG_SWAP
1109	bool "Swap controller"
1110	depends on MEMCG && SWAP
1111	help
1112	Provides control over the swap space consumed by tasks in a cgroup.
1113
1114	config MEMCG_SWAP_ENABLED
1115	bool "Swap controller enabled by default"
1116	depends on MEMCG_SWAP
1117	default y
1118	help
1119	Memory Resource Controller Swap Extension comes with its price in
1120	a bigger memory consumption. General purpose distribution kernels
1121	which want to enable the feature but keep it disabled by default
1122	and let the user enable it by swapaccount=1 boot command line
1123	parameter should have this option unselected.
1124	For those who want to have the feature enabled by default should
1125	select this option (if, for some reason, they need to disable it
1126	then swapaccount=0 does the trick).
1127
1128	config BLK_CGROUP
1129	bool "IO controller"
1130	depends on BLOCK
1131	default n
1132	---help---
1133	Generic block IO controller cgroup interface. This is the common
1134	cgroup interface which should be used by various IO controlling
1135	policies.
1136
1137	Currently, CFQ IO scheduler uses it to recognize task groups and
1138	control disk bandwidth allocation (proportional time slice allocation)
1139	to such task groups. It is also used by bio throttling logic in
1140	block layer to implement upper limit in IO rates on a device.
1141
1142	This option only enables generic Block IO controller infrastructure.
1143	One needs to also enable actual IO controlling logic/policy. For
1144	enabling proportional weight division of disk bandwidth in CFQ, set
1145	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1146	CONFIG_BLK_DEV_THROTTLING=y.
1147
1148	See Documentation/cgroup-v1/blkio-controller.txt for more information.
1149
1150	config DEBUG_BLK_CGROUP
1151	bool "IO controller debugging"
1152	depends on BLK_CGROUP
1153	default n
1154	---help---
1155	Enable some debugging help. Currently it exports additional stat
1156	files in a cgroup which can be useful for debugging.
1157
1158	config CGROUP_WRITEBACK
1159	bool
1160	depends on MEMCG && BLK_CGROUP
1161	default y
1162
1163	menuconfig CGROUP_SCHED
1164	bool "CPU controller"
1165	default n
1166	help
1167	This feature lets CPU scheduler recognize task groups and control CPU
1168	bandwidth allocation to such task groups. It uses cgroups to group
1169	tasks.
1170
1171	if CGROUP_SCHED
1172	config FAIR_GROUP_SCHED
1173	bool "Group scheduling for SCHED_OTHER"
1174	depends on CGROUP_SCHED
1175	default CGROUP_SCHED
1176
1177	config CFS_BANDWIDTH
1178	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1179	depends on FAIR_GROUP_SCHED
1180	default n
1181	help
1182	This option allows users to define CPU bandwidth rates (limits) for
1183	tasks running within the fair group scheduler. Groups with no limit
1184	set are considered to be unconstrained and will run with no
1185	restriction.
1186	See tip/Documentation/scheduler/sched-bwc.txt for more information.
1187
1188	config RT_GROUP_SCHED
1189	bool "Group scheduling for SCHED_RR/FIFO"
1190	depends on CGROUP_SCHED
1191	default n
1192	help
1193	This feature lets you explicitly allocate real CPU bandwidth
1194	to task groups. If enabled, it will also make it impossible to
1195	schedule realtime tasks for non-root users until you allocate
1196	realtime bandwidth for them.
1197	See Documentation/scheduler/sched-rt-group.txt for more information.
1198
1199	endif #CGROUP_SCHED
1200
1201	config CGROUP_PIDS
1202	bool "PIDs controller"
1203	help
1204	Provides enforcement of process number limits in the scope of a
1205	cgroup. Any attempt to fork more processes than is allowed in the
1206	cgroup will fail. PIDs are fundamentally a global resource because it
1207	is fairly trivial to reach PID exhaustion before you reach even a
1208	conservative kmemcg limit. As a result, it is possible to grind a
1209	system to halt without being limited by other cgroup policies. The
1210	PIDs controller is designed to stop this from happening.
1211
1212	It should be noted that organisational operations (such as attaching
1213	to a cgroup hierarchy will *not* be blocked by the PIDs controller),
1214	since the PIDs limit only affects a process's ability to fork, not to
1215	attach to a cgroup.
1216
1217	config CGROUP_FREEZER
1218	bool "Freezer controller"
1219	help
1220	Provides a way to freeze and unfreeze all tasks in a
1221	cgroup.
1222
1223	This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1224	controller includes important in-kernel memory consumers per default.
1225
1226	If you're using cgroup2, say N.
1227
1228	config CGROUP_HUGETLB
1229	bool "HugeTLB controller"
1230	depends on HUGETLB_PAGE
1231	select PAGE_COUNTER
1232	default n
1233	help
1234	Provides a cgroup controller for HugeTLB pages.
1235	When you enable this, you can put a per cgroup limit on HugeTLB usage.
1236	The limit is enforced during page fault. Since HugeTLB doesn't
1237	support page reclaim, enforcing the limit at page fault time implies
1238	that, the application will get SIGBUS signal if it tries to access
1239	HugeTLB pages beyond its limit. This requires the application to know
1240	beforehand how much HugeTLB pages it would require for its use. The
1241	control group is tracked in the third page lru pointer. This means
1242	that we cannot use the controller with huge page less than 3 pages.
1243
1244	config CPUSETS
1245	bool "Cpuset controller"
1246	help
1247	This option will let you create and manage CPUSETs which
1248	allow dynamically partitioning a system into sets of CPUs and
1249	Memory Nodes and assigning tasks to run only within those sets.
1250	This is primarily useful on large SMP or NUMA systems.
1251
1252	Say N if unsure.
1253
1254	config PROC_PID_CPUSET
1255	bool "Include legacy /proc/<pid>/cpuset file"
1256	depends on CPUSETS
1257	default y
1258
1259	config CGROUP_DEVICE
1260	bool "Device controller"
1261	help
1262	Provides a cgroup controller implementing whitelists for
1263	devices which a process in the cgroup can mknod or open.
1264
1265	config CGROUP_CPUACCT
1266	bool "Simple CPU accounting controller"
1267	help
1268	Provides a simple controller for monitoring the
1269	total CPU consumed by the tasks in a cgroup.
1270
1271	config CGROUP_PERF
1272	bool "Perf controller"
1273	depends on PERF_EVENTS
1274	help
1275	This option extends the perf per-cpu mode to restrict monitoring
1276	to threads which belong to the cgroup specified and run on the
1277	designated cpu.
1278
1279	Say N if unsure.
1280
1281	config CGROUP_BPF
1282	bool "Support for eBPF programs attached to cgroups"
1283	depends on BPF_SYSCALL
1284	select SOCK_CGROUP_DATA
1285	help
1286	Allow attaching eBPF programs to a cgroup using the bpf(2)
1287	syscall command BPF_PROG_ATTACH.
1288
1289	In which context these programs are accessed depends on the type
1290	of attachment. For instance, programs that are attached using
1291	BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1292	inet sockets.
1293
1294	config CGROUP_DEBUG
1295	bool "Example controller"
1296	default n
1297	help
1298	This option enables a simple controller that exports
1299	debugging information about the cgroups framework.
1300
1301	Say N.
1302
1303	config SOCK_CGROUP_DATA
1304	bool
1305	default n
1306
1307	endif # CGROUPS
1308
1309	config CHECKPOINT_RESTORE
1310	bool "Checkpoint/restore support" if EXPERT
1311	select PROC_CHILDREN
1312	default n
1313	help
1314	Enables additional kernel features in a sake of checkpoint/restore.
1315	In particular it adds auxiliary prctl codes to setup process text,
1316	data and heap segment sizes, and a few additional /proc filesystem
1317	entries.
1318
1319	If unsure, say N here.
1320
1321	menuconfig NAMESPACES
1322	bool "Namespaces support" if EXPERT
1323	depends on MULTIUSER
1324	default !EXPERT
1325	help
1326	Provides the way to make tasks work with different objects using
1327	the same id. For example same IPC id may refer to different objects
1328	or same user id or pid may refer to different tasks when used in
1329	different namespaces.
1330
1331	if NAMESPACES
1332
1333	config UTS_NS
1334	bool "UTS namespace"
1335	default y
1336	help
1337	In this namespace tasks see different info provided with the
1338	uname() system call
1339
1340	config IPC_NS
1341	bool "IPC namespace"
1342	depends on (SYSVIPC || POSIX_MQUEUE)
1343	default y
1344	help
1345	In this namespace tasks work with IPC ids which correspond to
1346	different IPC objects in different namespaces.
1347
1348	config USER_NS
1349	bool "User namespace"
1350	default n
1351	help
1352	This allows containers, i.e. vservers, to use user namespaces
1353	to provide different user info for different servers.
1354
1355	When user namespaces are enabled in the kernel it is
1356	recommended that the MEMCG option also be enabled and that
1357	user-space use the memory control groups to limit the amount
1358	of memory a memory unprivileged users can use.
1359
1360	If unsure, say N.
1361
1362	config PID_NS
1363	bool "PID Namespaces"
1364	default y
1365	help
1366	Support process id namespaces. This allows having multiple
1367	processes with the same pid as long as they are in different
1368	pid namespaces. This is a building block of containers.
1369
1370	config NET_NS
1371	bool "Network namespace"
1372	depends on NET
1373	default y
1374	help
1375	Allow user space to create what appear to be multiple instances
1376	of the network stack.
1377
1378	endif # NAMESPACES
1379
1380	config SCHED_AUTOGROUP
1381	bool "Automatic process group scheduling"
1382	select CGROUPS
1383	select CGROUP_SCHED
1384	select FAIR_GROUP_SCHED
1385	help
1386	This option optimizes the scheduler for common desktop workloads by
1387	automatically creating and populating task groups. This separation
1388	of workloads isolates aggressive CPU burners (like build jobs) from
1389	desktop applications. Task group autogeneration is currently based
1390	upon task session.
1391
1392	config SCHED_TUNE
1393	bool "Boosting for CFS tasks (EXPERIMENTAL)"
1394	depends on SMP
1395	help
1396	This option enables the system-wide support for task boosting.
1397	When this support is enabled a new sysctl interface is exposed to
1398	userspace via:
1399	/proc/sys/kernel/sched_cfs_boost
1400	which allows to set a system-wide boost value in range [0..100].
1401
1402	The currently boosting strategy is implemented in such a way that:
1403	- a 0% boost value requires to operate in "standard" mode by
1404	scheduling all tasks at the minimum capacities required by their
1405	workload demand
1406	- a 100% boost value requires to push at maximum the task
1407	performances, "regardless" of the incurred energy consumption
1408
1409	A boost value in between these two boundaries is used to bias the
1410	power/performance trade-off, the higher the boost value the more the
1411	scheduler is biased toward performance boosting instead of energy
1412	efficiency.
1413
1414	Since this support exposes a single system-wide knob, the specified
1415	boost value is applied to all (CFS) tasks in the system.
1416
1417	If unsure, say N.
1418
1419	config DEFAULT_USE_ENERGY_AWARE
1420	bool "Default to enabling the Energy Aware Scheduler feature"
1421	default n
1422	help
1423	This option defaults the ENERGY_AWARE scheduling feature to true,
1424	as without SCHED_DEBUG set this feature can't be enabled or disabled
1425	via sysctl.
1426
1427	Say N if unsure.
1428
1429	config SYSFS_DEPRECATED
1430	bool "Enable deprecated sysfs features to support old userspace tools"
1431	depends on SYSFS
1432	default n
1433	help
1434	This option adds code that switches the layout of the "block" class
1435	devices, to not show up in /sys/class/block/, but only in
1436	/sys/block/.
1437
1438	This switch is only active when the sysfs.deprecated=1 boot option is
1439	passed or the SYSFS_DEPRECATED_V2 option is set.
1440
1441	This option allows new kernels to run on old distributions and tools,
1442	which might get confused by /sys/class/block/. Since 2007/2008 all
1443	major distributions and tools handle this just fine.
1444
1445	Recent distributions and userspace tools after 2009/2010 depend on
1446	the existence of /sys/class/block/, and will not work with this
1447	option enabled.
1448
1449	Only if you are using a new kernel on an old distribution, you might
1450	need to say Y here.
1451
1452	config SYSFS_DEPRECATED_V2
1453	bool "Enable deprecated sysfs features by default"
1454	default n
1455	depends on SYSFS
1456	depends on SYSFS_DEPRECATED
1457	help
1458	Enable deprecated sysfs by default.
1459
1460	See the CONFIG_SYSFS_DEPRECATED option for more details about this
1461	option.
1462
1463	Only if you are using a new kernel on an old distribution, you might
1464	need to say Y here. Even then, odds are you would not need it
1465	enabled, you can always pass the boot option if absolutely necessary.
1466
1467	config RELAY
1468	bool "Kernel->user space relay support (formerly relayfs)"
1469	select IRQ_WORK
1470	help
1471	This option enables support for relay interface support in
1472	certain file systems (such as debugfs).
1473	It is designed to provide an efficient mechanism for tools and
1474	facilities to relay large amounts of data from kernel space to
1475	user space.
1476
1477	If unsure, say N.
1478
1479	config BLK_DEV_INITRD
1480	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1481	depends on BROKEN || !FRV
1482	help
1483	The initial RAM filesystem is a ramfs which is loaded by the
1484	boot loader (loadlin or lilo) and that is mounted as root
1485	before the normal boot procedure. It is typically used to
1486	load modules needed to mount the "real" root file system,
1487	etc. See <file:Documentation/initrd.txt> for details.
1488
1489	If RAM disk support (BLK_DEV_RAM) is also included, this
1490	also enables initial RAM disk (initrd) support and adds
1491	15 Kbytes (more on some other architectures) to the kernel size.
1492
1493	If unsure say Y.
1494
1495	if BLK_DEV_INITRD
1496
1497	source "usr/Kconfig"
1498
1499	endif
1500
1501	choice
1502	prompt "Compiler optimization level"
1503	default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
1504
1505	config CC_OPTIMIZE_FOR_PERFORMANCE
1506	bool "Optimize for performance"
1507	help
1508	This is the default optimization level for the kernel, building
1509	with the "-O2" compiler flag for best performance and most
1510	helpful compile-time warnings.
1511
1512	config CC_OPTIMIZE_FOR_SIZE
1513	bool "Optimize for size"
1514	help
1515	Enabling this option will pass "-Os" instead of "-O2" to
1516	your compiler resulting in a smaller kernel.
1517
1518	If unsure, say N.
1519
1520	endchoice
1521
1522	config SYSCTL
1523	bool
1524
1525	config ANON_INODES
1526	bool
1527
1528	config HAVE_UID16
1529	bool
1530
1531	config SYSCTL_EXCEPTION_TRACE
1532	bool
1533	help
1534	Enable support for /proc/sys/debug/exception-trace.
1535
1536	config SYSCTL_ARCH_UNALIGN_NO_WARN
1537	bool
1538	help
1539	Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1540	Allows arch to define/use @no_unaligned_warning to possibly warn
1541	about unaligned access emulation going on under the hood.
1542
1543	config SYSCTL_ARCH_UNALIGN_ALLOW
1544	bool
1545	help
1546	Enable support for /proc/sys/kernel/unaligned-trap
1547	Allows arches to define/use @unaligned_enabled to runtime toggle
1548	the unaligned access emulation.
1549	see arch/parisc/kernel/unaligned.c for reference
1550
1551	config HAVE_PCSPKR_PLATFORM
1552	bool
1553
1554	# interpreter that classic socket filters depend on
1555	config BPF
1556	bool
1557
1558	menuconfig EXPERT
1559	bool "Configure standard kernel features (expert users)"
1560	# Unhide debug options, to make the on-by-default options visible
1561	select DEBUG_KERNEL
1562	help
1563	This option allows certain base kernel options and settings
1564	to be disabled or tweaked. This is for specialized
1565	environments which can tolerate a "non-standard" kernel.
1566	Only use this if you really know what you are doing.
1567
1568	config UID16
1569	bool "Enable 16-bit UID system calls" if EXPERT
1570	depends on HAVE_UID16 && MULTIUSER
1571	default y
1572	help
1573	This enables the legacy 16-bit UID syscall wrappers.
1574
1575	config MULTIUSER
1576	bool "Multiple users, groups and capabilities support" if EXPERT
1577	default y
1578	help
1579	This option enables support for non-root users, groups and
1580	capabilities.
1581
1582	If you say N here, all processes will run with UID 0, GID 0, and all
1583	possible capabilities. Saying N here also compiles out support for
1584	system calls related to UIDs, GIDs, and capabilities, such as setuid,
1585	setgid, and capset.
1586
1587	If unsure, say Y here.
1588
1589	config SGETMASK_SYSCALL
1590	bool "sgetmask/ssetmask syscalls support" if EXPERT
1591	def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1592	---help---
1593	sys_sgetmask and sys_ssetmask are obsolete system calls
1594	no longer supported in libc but still enabled by default in some
1595	architectures.
1596
1597	If unsure, leave the default option here.
1598
1599	config SYSFS_SYSCALL
1600	bool "Sysfs syscall support" if EXPERT
1601	default y
1602	---help---
1603	sys_sysfs is an obsolete system call no longer supported in libc.
1604	Note that disabling this option is more secure but might break
1605	compatibility with some systems.
1606
1607	If unsure say Y here.
1608
1609	config SYSCTL_SYSCALL
1610	bool "Sysctl syscall support" if EXPERT
1611	depends on PROC_SYSCTL
1612	default n
1613	select SYSCTL
1614	---help---
1615	sys_sysctl uses binary paths that have been found challenging
1616	to properly maintain and use. The interface in /proc/sys
1617	using paths with ascii names is now the primary path to this
1618	information.
1619
1620	Almost nothing using the binary sysctl interface so if you are
1621	trying to save some space it is probably safe to disable this,
1622	making your kernel marginally smaller.
1623
1624	If unsure say N here.
1625
1626	config KALLSYMS
1627	bool "Load all symbols for debugging/ksymoops" if EXPERT
1628	default y
1629	help
1630	Say Y here to let the kernel print out symbolic crash information and
1631	symbolic stack backtraces. This increases the size of the kernel
1632	somewhat, as all symbols have to be loaded into the kernel image.
1633
1634	config KALLSYMS_ALL
1635	bool "Include all symbols in kallsyms"
1636	depends on DEBUG_KERNEL && KALLSYMS
1637	help
1638	Normally kallsyms only contains the symbols of functions for nicer
1639	OOPS messages and backtraces (i.e., symbols from the text and inittext
1640	sections). This is sufficient for most cases. And only in very rare
1641	cases (e.g., when a debugger is used) all symbols are required (e.g.,
1642	names of variables from the data sections, etc).
1643
1644	This option makes sure that all symbols are loaded into the kernel
1645	image (i.e., symbols from all sections) in cost of increased kernel
1646	size (depending on the kernel configuration, it may be 300KiB or
1647	something like this).
1648
1649	Say N unless you really need all symbols.
1650
1651	config KALLSYMS_ABSOLUTE_PERCPU
1652	bool
1653	depends on KALLSYMS
1654	default X86_64 && SMP
1655
1656	config KALLSYMS_BASE_RELATIVE
1657	bool
1658	depends on KALLSYMS
1659	default !IA64 && !(TILE && 64BIT)
1660	help
1661	Instead of emitting them as absolute values in the native word size,
1662	emit the symbol references in the kallsyms table as 32-bit entries,
1663	each containing a relative value in the range [base, base + U32_MAX]
1664	or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1665	an absolute value in the range [0, S32_MAX] or a relative value in the
1666	range [base, base + S32_MAX], where base is the lowest relative symbol
1667	address encountered in the image.
1668
1669	On 64-bit builds, this reduces the size of the address table by 50%,
1670	but more importantly, it results in entries whose values are build
1671	time constants, and no relocation pass is required at runtime to fix
1672	up the entries based on the runtime load address of the kernel.
1673
1674	config PRINTK
1675	default y
1676	bool "Enable support for printk" if EXPERT
1677	select IRQ_WORK
1678	help
1679	This option enables normal printk support. Removing it
1680	eliminates most of the message strings from the kernel image
1681	and makes the kernel more or less silent. As this makes it
1682	very difficult to diagnose system problems, saying N here is
1683	strongly discouraged.
1684
1685	config PRINTK_NMI
1686	def_bool y
1687	depends on PRINTK
1688	depends on HAVE_NMI
1689
1690	config BUG
1691	bool "BUG() support" if EXPERT
1692	default y
1693	help
1694	Disabling this option eliminates support for BUG and WARN, reducing
1695	the size of your kernel image and potentially quietly ignoring
1696	numerous fatal conditions. You should only consider disabling this
1697	option for embedded systems with no facilities for reporting errors.
1698	Just say Y.
1699
1700	config ELF_CORE
1701	depends on COREDUMP
1702	default y
1703	bool "Enable ELF core dumps" if EXPERT
1704	help
1705	Enable support for generating core dumps. Disabling saves about 4k.
1706
1707
1708	config PCSPKR_PLATFORM
1709	bool "Enable PC-Speaker support" if EXPERT
1710	depends on HAVE_PCSPKR_PLATFORM
1711	select I8253_LOCK
1712	default y
1713	help
1714	This option allows to disable the internal PC-Speaker
1715	support, saving some memory.
1716
1717	config BASE_FULL
1718	default y
1719	bool "Enable full-sized data structures for core" if EXPERT
1720	help
1721	Disabling this option reduces the size of miscellaneous core
1722	kernel data structures. This saves memory on small machines,
1723	but may reduce performance.
1724
1725	config FUTEX
1726	bool "Enable futex support" if EXPERT
1727	default y
1728	select RT_MUTEXES
1729	help
1730	Disabling this option will cause the kernel to be built without
1731	support for "fast userspace mutexes". The resulting kernel may not
1732	run glibc-based applications correctly.
1733
1734	config HAVE_FUTEX_CMPXCHG
1735	bool
1736	depends on FUTEX
1737	help
1738	Architectures should select this if futex_atomic_cmpxchg_inatomic()
1739	is implemented and always working. This removes a couple of runtime
1740	checks.
1741
1742	config EPOLL
1743	bool "Enable eventpoll support" if EXPERT
1744	default y
1745	select ANON_INODES
1746	help
1747	Disabling this option will cause the kernel to be built without
1748	support for epoll family of system calls.
1749
1750	config SIGNALFD
1751	bool "Enable signalfd() system call" if EXPERT
1752	select ANON_INODES
1753	default y
1754	help
1755	Enable the signalfd() system call that allows to receive signals
1756	on a file descriptor.
1757
1758	If unsure, say Y.
1759
1760	config TIMERFD
1761	bool "Enable timerfd() system call" if EXPERT
1762	select ANON_INODES
1763	default y
1764	help
1765	Enable the timerfd() system call that allows to receive timer
1766	events on a file descriptor.
1767
1768	If unsure, say Y.
1769
1770	config EVENTFD
1771	bool "Enable eventfd() system call" if EXPERT
1772	select ANON_INODES
1773	default y
1774	help
1775	Enable the eventfd() system call that allows to receive both
1776	kernel notification (ie. KAIO) or userspace notifications.
1777
1778	If unsure, say Y.
1779
1780	# syscall, maps, verifier
1781	config BPF_SYSCALL
1782	bool "Enable bpf() system call"
1783	select ANON_INODES
1784	select BPF
1785	default n
1786	help
1787	Enable the bpf() system call that allows to manipulate eBPF
1788	programs and maps via file descriptors.
1789
1790	config BPF_JIT_ALWAYS_ON
1791	bool "Permanently enable BPF JIT and remove BPF interpreter"
1792	depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1793	help
1794	Enables BPF JIT and removes BPF interpreter to avoid
1795	speculative execution of BPF instructions by the interpreter
1796
1797	config SHMEM
1798	bool "Use full shmem filesystem" if EXPERT
1799	default y
1800	depends on MMU
1801	help
1802	The shmem is an internal filesystem used to manage shared memory.
1803	It is backed by swap and manages resource limits. It is also exported
1804	to userspace as tmpfs if TMPFS is enabled. Disabling this
1805	option replaces shmem and tmpfs with the much simpler ramfs code,
1806	which may be appropriate on small systems without swap.
1807
1808	config AIO
1809	bool "Enable AIO support" if EXPERT
1810	default y
1811	help
1812	This option enables POSIX asynchronous I/O which may by used
1813	by some high performance threaded applications. Disabling
1814	this option saves about 7k.
1815
1816	config ADVISE_SYSCALLS
1817	bool "Enable madvise/fadvise syscalls" if EXPERT
1818	default y
1819	help
1820	This option enables the madvise and fadvise syscalls, used by
1821	applications to advise the kernel about their future memory or file
1822	usage, improving performance. If building an embedded system where no
1823	applications use these syscalls, you can disable this option to save
1824	space.
1825
1826	config USERFAULTFD
1827	bool "Enable userfaultfd() system call"
1828	select ANON_INODES
1829	depends on MMU
1830	help
1831	Enable the userfaultfd() system call that allows to intercept and
1832	handle page faults in userland.
1833
1834	config PCI_QUIRKS
1835	default y
1836	bool "Enable PCI quirk workarounds" if EXPERT
1837	depends on PCI
1838	help
1839	This enables workarounds for various PCI chipset
1840	bugs/quirks. Disable this only if your target machine is
1841	unaffected by PCI quirks.
1842
1843	config MEMBARRIER
1844	bool "Enable membarrier() system call" if EXPERT
1845	default y
1846	help
1847	Enable the membarrier() system call that allows issuing memory
1848	barriers across all running threads, which can be used to distribute
1849	the cost of user-space memory barriers asymmetrically by transforming
1850	pairs of memory barriers into pairs consisting of membarrier() and a
1851	compiler barrier.
1852
1853	If unsure, say Y.
1854
1855	config EMBEDDED
1856	bool "Embedded system"
1857	option allnoconfig_y
1858	select EXPERT
1859	help
1860	This option should be enabled if compiling the kernel for
1861	an embedded system so certain expert options are available
1862	for configuration.
1863
1864	config HAVE_PERF_EVENTS
1865	bool
1866	help
1867	See tools/perf/design.txt for details.
1868
1869	config PERF_USE_VMALLOC
1870	bool
1871	help
1872	See tools/perf/design.txt for details
1873
1874	menu "Kernel Performance Events And Counters"
1875
1876	config PERF_EVENTS
1877	bool "Kernel performance events and counters"
1878	default y if PROFILING
1879	depends on HAVE_PERF_EVENTS
1880	select ANON_INODES
1881	select IRQ_WORK
1882	select SRCU
1883	help
1884	Enable kernel support for various performance events provided
1885	by software and hardware.
1886
1887	Software events are supported either built-in or via the
1888	use of generic tracepoints.
1889
1890	Most modern CPUs support performance events via performance
1891	counter registers. These registers count the number of certain
1892	types of hw events: such as instructions executed, cachemisses
1893	suffered, or branches mis-predicted - without slowing down the
1894	kernel or applications. These registers can also trigger interrupts
1895	when a threshold number of events have passed - and can thus be
1896	used to profile the code that runs on that CPU.
1897
1898	The Linux Performance Event subsystem provides an abstraction of
1899	these software and hardware event capabilities, available via a
1900	system call and used by the "perf" utility in tools/perf/. It
1901	provides per task and per CPU counters, and it provides event
1902	capabilities on top of those.
1903
1904	Say Y if unsure.
1905
1906	config DEBUG_PERF_USE_VMALLOC
1907	default n
1908	bool "Debug: use vmalloc to back perf mmap() buffers"
1909	depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1910	select PERF_USE_VMALLOC
1911	help
1912	Use vmalloc memory to back perf mmap() buffers.
1913
1914	Mostly useful for debugging the vmalloc code on platforms
1915	that don't require it.
1916
1917	Say N if unsure.
1918
1919	endmenu
1920
1921	config VM_EVENT_COUNTERS
1922	default y
1923	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1924	help
1925	VM event counters are needed for event counts to be shown.
1926	This option allows the disabling of the VM event counters
1927	on EXPERT systems. /proc/vmstat will only show page counts
1928	if VM event counters are disabled.
1929
1930	config SLUB_DEBUG
1931	default y
1932	bool "Enable SLUB debugging support" if EXPERT
1933	depends on SLUB && SYSFS
1934	help
1935	SLUB has extensive debug support features. Disabling these can
1936	result in significant savings in code size. This also disables
1937	SLUB sysfs support. /sys/slab will not exist and there will be
1938	no support for cache validation etc.
1939
1940	config SLUB_MEMCG_SYSFS_ON
1941	default n
1942	bool "Enable memcg SLUB sysfs support by default" if EXPERT
1943	depends on SLUB && SYSFS && MEMCG
1944	help
1945	SLUB creates a directory under /sys/kernel/slab for each
1946	allocation cache to host info and debug files. If memory
1947	cgroup is enabled, each cache can have per memory cgroup
1948	caches. SLUB can create the same sysfs directories for these
1949	caches under /sys/kernel/slab/CACHE/cgroup but it can lead
1950	to a very high number of debug files being created. This is
1951	controlled by slub_memcg_sysfs boot parameter and this
1952	config option determines the parameter's default value.
1953
1954	config COMPAT_BRK
1955	bool "Disable heap randomization"
1956	default y
1957	help
1958	Randomizing heap placement makes heap exploits harder, but it
1959	also breaks ancient binaries (including anything libc5 based).
1960	This option changes the bootup default to heap randomization
1961	disabled, and can be overridden at runtime by setting
1962	/proc/sys/kernel/randomize_va_space to 2.
1963
1964	On non-ancient distros (post-2000 ones) N is usually a safe choice.
1965
1966	choice
1967	prompt "Choose SLAB allocator"
1968	default SLUB
1969	help
1970	This option allows to select a slab allocator.
1971
1972	config SLAB
1973	bool "SLAB"
1974	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1975	help
1976	The regular slab allocator that is established and known to work
1977	well in all environments. It organizes cache hot objects in
1978	per cpu and per node queues.
1979
1980	config SLUB
1981	bool "SLUB (Unqueued Allocator)"
1982	select HAVE_HARDENED_USERCOPY_ALLOCATOR
1983	help
1984	SLUB is a slab allocator that minimizes cache line usage
1985	instead of managing queues of cached objects (SLAB approach).
1986	Per cpu caching is realized using slabs of objects instead
1987	of queues of objects. SLUB can use memory efficiently
1988	and has enhanced diagnostics. SLUB is the default choice for
1989	a slab allocator.
1990
1991	config SLOB
1992	depends on EXPERT
1993	bool "SLOB (Simple Allocator)"
1994	help
1995	SLOB replaces the stock allocator with a drastically simpler
1996	allocator. SLOB is generally more space efficient but
1997	does not perform as well on large systems.
1998
1999	endchoice
2000
2001	config SLAB_FREELIST_RANDOM
2002	default n
2003	depends on SLAB || SLUB
2004	bool "SLAB freelist randomization"
2005	help
2006	Randomizes the freelist order used on creating new pages. This
2007	security feature reduces the predictability of the kernel slab
2008	allocator against heap overflows.
2009
2010	config SLUB_CPU_PARTIAL
2011	default y
2012	depends on SLUB && SMP
2013	bool "SLUB per cpu partial cache"
2014	help
2015	Per cpu partial caches accellerate objects allocation and freeing
2016	that is local to a processor at the price of more indeterminism
2017	in the latency of the free. On overflow these caches will be cleared
2018	which requires the taking of locks that may cause latency spikes.
2019	Typically one would choose no for a realtime system.
2020
2021	config MMAP_ALLOW_UNINITIALIZED
2022	bool "Allow mmapped anonymous memory to be uninitialized"
2023	depends on EXPERT && !MMU
2024	default n
2025	help
2026	Normally, and according to the Linux spec, anonymous memory obtained
2027	from mmap() has it's contents cleared before it is passed to
2028	userspace. Enabling this config option allows you to request that
2029	mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
2030	providing a huge performance boost. If this option is not enabled,
2031	then the flag will be ignored.
2032
2033	This is taken advantage of by uClibc's malloc(), and also by
2034	ELF-FDPIC binfmt's brk and stack allocator.
2035
2036	Because of the obvious security issues, this option should only be
2037	enabled on embedded devices where you control what is run in
2038	userspace. Since that isn't generally a problem on no-MMU systems,
2039	it is normally safe to say Y here.
2040
2041	See Documentation/nommu-mmap.txt for more information.
2042
2043	config SYSTEM_DATA_VERIFICATION
2044	def_bool n
2045	select SYSTEM_TRUSTED_KEYRING
2046	select KEYS
2047	select CRYPTO
2048	select CRYPTO_RSA
2049	select ASYMMETRIC_KEY_TYPE
2050	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
2051	select ASN1
2052	select OID_REGISTRY
2053	select X509_CERTIFICATE_PARSER
2054	select PKCS7_MESSAGE_PARSER
2055	help
2056	Provide PKCS#7 message verification using the contents of the system
2057	trusted keyring to provide public keys. This then can be used for
2058	module verification, kexec image verification and firmware blob
2059	verification.
2060
2061	config PROFILING
2062	bool "Profiling support"
2063	help
2064	Say Y here to enable the extended profiling support mechanisms used
2065	by profilers such as OProfile.
2066
2067	#
2068	# Place an empty function call at each tracepoint site. Can be
2069	# dynamically changed for a probe function.
2070	#
2071	config TRACEPOINTS
2072	bool
2073
2074	source "arch/Kconfig"
2075
2076	endmenu # General setup
2077
2078	config HAVE_GENERIC_DMA_COHERENT
2079	bool
2080	default n
2081
2082	config SLABINFO
2083	bool
2084	depends on PROC_FS
2085	depends on SLAB || SLUB_DEBUG
2086	default y
2087
2088	config RT_MUTEXES
2089	bool
2090
2091	config BASE_SMALL
2092	int
2093	default 0 if BASE_FULL
2094	default 1 if !BASE_FULL
2095
2096	menuconfig MODULES
2097	bool "Enable loadable module support"
2098	option modules
2099	help
2100	Kernel modules are small pieces of compiled code which can
2101	be inserted in the running kernel, rather than being
2102	permanently built into the kernel. You use the "modprobe"
2103	tool to add (and sometimes remove) them. If you say Y here,
2104	many parts of the kernel can be built as modules (by
2105	answering M instead of Y where indicated): this is most
2106	useful for infrequently used options which are not required
2107	for booting. For more information, see the man pages for
2108	modprobe, lsmod, modinfo, insmod and rmmod.
2109
2110	If you say Y here, you will need to run "make
2111	modules_install" to put the modules under /lib/modules/
2112	where modprobe can find them (you may need to be root to do
2113	this).
2114
2115	If unsure, say Y.
2116
2117	if MODULES
2118
2119	config MODULE_FORCE_LOAD
2120	bool "Forced module loading"
2121	default n
2122	help
2123	Allow loading of modules without version information (ie. modprobe
2124	--force). Forced module loading sets the 'F' (forced) taint flag and
2125	is usually a really bad idea.
2126
2127	config MODULE_UNLOAD
2128	bool "Module unloading"
2129	help
2130	Without this option you will not be able to unload any
2131	modules (note that some modules may not be unloadable
2132	anyway), which makes your kernel smaller, faster
2133	and simpler. If unsure, say Y.
2134
2135	config MODULE_FORCE_UNLOAD
2136	bool "Forced module unloading"
2137	depends on MODULE_UNLOAD
2138	help
2139	This option allows you to force a module to unload, even if the
2140	kernel believes it is unsafe: the kernel will remove the module
2141	without waiting for anyone to stop using it (using the -f option to
2142	rmmod). This is mainly for kernel developers and desperate users.
2143	If unsure, say N.
2144
2145	config MODVERSIONS
2146	bool "Module versioning support"
2147	help
2148	Usually, you have to use modules compiled with your kernel.
2149	Saying Y here makes it sometimes possible to use modules
2150	compiled for different kernels, by adding enough information
2151	to the modules to (hopefully) spot any changes which would
2152	make them incompatible with the kernel you are running. If
2153	unsure, say N.
2154
2155	config MODULE_SRCVERSION_ALL
2156	bool "Source checksum for all modules"
2157	help
2158	Modules which contain a MODULE_VERSION get an extra "srcversion"
2159	field inserted into their modinfo section, which contains a
2160	sum of the source files which made it. This helps maintainers
2161	see exactly which source was used to build a module (since
2162	others sometimes change the module source without updating
2163	the version). With this option, such a "srcversion" field
2164	will be created for all modules. If unsure, say N.
2165
2166	config MODULE_SIG
2167	bool "Module signature verification"
2168	depends on MODULES
2169	select SYSTEM_DATA_VERIFICATION
2170	help
2171	Check modules for valid signatures upon load: the signature
2172	is simply appended to the module. For more information see
2173	Documentation/module-signing.txt.
2174
2175	Note that this option adds the OpenSSL development packages as a
2176	kernel build dependency so that the signing tool can use its crypto
2177	library.
2178
2179	!!!WARNING!!! If you enable this option, you MUST make sure that the
2180	module DOES NOT get stripped after being signed. This includes the
2181	debuginfo strip done by some packagers (such as rpmbuild) and
2182	inclusion into an initramfs that wants the module size reduced.
2183
2184	config MODULE_SIG_FORCE
2185	bool "Require modules to be validly signed"
2186	depends on MODULE_SIG
2187	help
2188	Reject unsigned modules or signed modules for which we don't have a
2189	key. Without this, such modules will simply taint the kernel.
2190
2191	config MODULE_SIG_ALL
2192	bool "Automatically sign all modules"
2193	default y
2194	depends on MODULE_SIG
2195	help
2196	Sign all modules during make modules_install. Without this option,
2197	modules must be signed manually, using the scripts/sign-file tool.
2198
2199	comment "Do not forget to sign required modules with scripts/sign-file"
2200	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2201
2202	choice
2203	prompt "Which hash algorithm should modules be signed with?"
2204	depends on MODULE_SIG
2205	help
2206	This determines which sort of hashing algorithm will be used during
2207	signature generation. This algorithm _must_ be built into the kernel
2208	directly so that signature verification can take place. It is not
2209	possible to load a signed module containing the algorithm to check
2210	the signature on that module.
2211
2212	config MODULE_SIG_SHA1
2213	bool "Sign modules with SHA-1"
2214	select CRYPTO_SHA1
2215
2216	config MODULE_SIG_SHA224
2217	bool "Sign modules with SHA-224"
2218	select CRYPTO_SHA256
2219
2220	config MODULE_SIG_SHA256
2221	bool "Sign modules with SHA-256"
2222	select CRYPTO_SHA256
2223
2224	config MODULE_SIG_SHA384
2225	bool "Sign modules with SHA-384"
2226	select CRYPTO_SHA512
2227
2228	config MODULE_SIG_SHA512
2229	bool "Sign modules with SHA-512"
2230	select CRYPTO_SHA512
2231
2232	endchoice
2233
2234	config MODULE_SIG_HASH
2235	string
2236	depends on MODULE_SIG
2237	default "sha1" if MODULE_SIG_SHA1
2238	default "sha224" if MODULE_SIG_SHA224
2239	default "sha256" if MODULE_SIG_SHA256
2240	default "sha384" if MODULE_SIG_SHA384
2241	default "sha512" if MODULE_SIG_SHA512
2242
2243	config MODULE_COMPRESS
2244	bool "Compress modules on installation"
2245	depends on MODULES
2246	help
2247
2248	Compresses kernel modules when 'make modules_install' is run; gzip or
2249	xz depending on "Compression algorithm" below.
2250
2251	module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2252
2253	Out-of-tree kernel modules installed using Kbuild will also be
2254	compressed upon installation.
2255
2256	Note: for modules inside an initrd or initramfs, it's more efficient
2257	to compress the whole initrd or initramfs instead.
2258
2259	Note: This is fully compatible with signed modules.
2260
2261	If in doubt, say N.
2262
2263	choice
2264	prompt "Compression algorithm"
2265	depends on MODULE_COMPRESS
2266	default MODULE_COMPRESS_GZIP
2267	help
2268	This determines which sort of compression will be used during
2269	'make modules_install'.
2270
2271	GZIP (default) and XZ are supported.
2272
2273	config MODULE_COMPRESS_GZIP
2274	bool "GZIP"
2275
2276	config MODULE_COMPRESS_XZ
2277	bool "XZ"
2278
2279	endchoice
2280
2281	config TRIM_UNUSED_KSYMS
2282	bool "Trim unused exported kernel symbols"
2283	depends on MODULES && !UNUSED_SYMBOLS
2284	help
2285	The kernel and some modules make many symbols available for
2286	other modules to use via EXPORT_SYMBOL() and variants. Depending
2287	on the set of modules being selected in your kernel configuration,
2288	many of those exported symbols might never be used.
2289
2290	This option allows for unused exported symbols to be dropped from
2291	the build. In turn, this provides the compiler more opportunities
2292	(especially when using LTO) for optimizing the code and reducing
2293	binary size. This might have some security advantages as well.
2294
2295	If unsure, or if you need to build out-of-tree modules, say N.
2296
2297	endif # MODULES
2298
2299	config MODULES_TREE_LOOKUP
2300	def_bool y
2301	depends on PERF_EVENTS || TRACING || CFI_CLANG
2302
2303	config INIT_ALL_POSSIBLE
2304	bool
2305	help
2306	Back when each arch used to define their own cpu_online_mask and
2307	cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2308	with all 1s, and others with all 0s. When they were centralised,
2309	it was better to provide this option than to break all the archs
2310	and have several arch maintainers pursuing me down dark alleys.
2311
2312	source "block/Kconfig"
2313
2314	config PREEMPT_NOTIFIERS
2315	bool
2316
2317	config PADATA
2318	depends on SMP
2319	bool
2320
2321	config ASN1
2322	tristate
2323	help
2324	Build a simple ASN.1 grammar compiler that produces a bytecode output
2325	that can be interpreted by the ASN.1 stream decoder and used to
2326	inform it as to what tags are to be expected in a stream and what
2327	functions to call on what tags.
2328
2329	source "kernel/Kconfig.locks"
2330