xref: /openbmc/linux/arch/Kconfig (revision eb3fcf00)
1#
2# General architecture dependent options
3#
4
5config KEXEC_CORE
6	bool
7
8config OPROFILE
9	tristate "OProfile system profiling"
10	depends on PROFILING
11	depends on HAVE_OPROFILE
12	select RING_BUFFER
13	select RING_BUFFER_ALLOW_SWAP
14	help
15	  OProfile is a profiling system capable of profiling the
16	  whole system, include the kernel, kernel modules, libraries,
17	  and applications.
18
19	  If unsure, say N.
20
21config OPROFILE_EVENT_MULTIPLEX
22	bool "OProfile multiplexing support (EXPERIMENTAL)"
23	default n
24	depends on OPROFILE && X86
25	help
26	  The number of hardware counters is limited. The multiplexing
27	  feature enables OProfile to gather more events than counters
28	  are provided by the hardware. This is realized by switching
29	  between events at an user specified time interval.
30
31	  If unsure, say N.
32
33config HAVE_OPROFILE
34	bool
35
36config OPROFILE_NMI_TIMER
37	def_bool y
38	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
39
40config KPROBES
41	bool "Kprobes"
42	depends on MODULES
43	depends on HAVE_KPROBES
44	select KALLSYMS
45	help
46	  Kprobes allows you to trap at almost any kernel address and
47	  execute a callback function.  register_kprobe() establishes
48	  a probepoint and specifies the callback.  Kprobes is useful
49	  for kernel debugging, non-intrusive instrumentation and testing.
50	  If in doubt, say "N".
51
52config JUMP_LABEL
53       bool "Optimize very unlikely/likely branches"
54       depends on HAVE_ARCH_JUMP_LABEL
55       help
56         This option enables a transparent branch optimization that
57	 makes certain almost-always-true or almost-always-false branch
58	 conditions even cheaper to execute within the kernel.
59
60	 Certain performance-sensitive kernel code, such as trace points,
61	 scheduler functionality, networking code and KVM have such
62	 branches and include support for this optimization technique.
63
64         If it is detected that the compiler has support for "asm goto",
65	 the kernel will compile such branches with just a nop
66	 instruction. When the condition flag is toggled to true, the
67	 nop will be converted to a jump instruction to execute the
68	 conditional block of instructions.
69
70	 This technique lowers overhead and stress on the branch prediction
71	 of the processor and generally makes the kernel faster. The update
72	 of the condition is slower, but those are always very rare.
73
74	 ( On 32-bit x86, the necessary options added to the compiler
75	   flags may increase the size of the kernel slightly. )
76
77config STATIC_KEYS_SELFTEST
78	bool "Static key selftest"
79	depends on JUMP_LABEL
80	help
81	  Boot time self-test of the branch patching code.
82
83config OPTPROBES
84	def_bool y
85	depends on KPROBES && HAVE_OPTPROBES
86	depends on !PREEMPT
87
88config KPROBES_ON_FTRACE
89	def_bool y
90	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
91	depends on DYNAMIC_FTRACE_WITH_REGS
92	help
93	 If function tracer is enabled and the arch supports full
94	 passing of pt_regs to function tracing, then kprobes can
95	 optimize on top of function tracing.
96
97config UPROBES
98	def_bool n
99	help
100	  Uprobes is the user-space counterpart to kprobes: they
101	  enable instrumentation applications (such as 'perf probe')
102	  to establish unintrusive probes in user-space binaries and
103	  libraries, by executing handler functions when the probes
104	  are hit by user-space applications.
105
106	  ( These probes come in the form of single-byte breakpoints,
107	    managed by the kernel and kept transparent to the probed
108	    application. )
109
110config HAVE_64BIT_ALIGNED_ACCESS
111	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
112	help
113	  Some architectures require 64 bit accesses to be 64 bit
114	  aligned, which also requires structs containing 64 bit values
115	  to be 64 bit aligned too. This includes some 32 bit
116	  architectures which can do 64 bit accesses, as well as 64 bit
117	  architectures without unaligned access.
118
119	  This symbol should be selected by an architecture if 64 bit
120	  accesses are required to be 64 bit aligned in this way even
121	  though it is not a 64 bit architecture.
122
123	  See Documentation/unaligned-memory-access.txt for more
124	  information on the topic of unaligned memory accesses.
125
126config HAVE_EFFICIENT_UNALIGNED_ACCESS
127	bool
128	help
129	  Some architectures are unable to perform unaligned accesses
130	  without the use of get_unaligned/put_unaligned. Others are
131	  unable to perform such accesses efficiently (e.g. trap on
132	  unaligned access and require fixing it up in the exception
133	  handler.)
134
135	  This symbol should be selected by an architecture if it can
136	  perform unaligned accesses efficiently to allow different
137	  code paths to be selected for these cases. Some network
138	  drivers, for example, could opt to not fix up alignment
139	  problems with received packets if doing so would not help
140	  much.
141
142	  See Documentation/unaligned-memory-access.txt for more
143	  information on the topic of unaligned memory accesses.
144
145config ARCH_USE_BUILTIN_BSWAP
146       bool
147       help
148	 Modern versions of GCC (since 4.4) have builtin functions
149	 for handling byte-swapping. Using these, instead of the old
150	 inline assembler that the architecture code provides in the
151	 __arch_bswapXX() macros, allows the compiler to see what's
152	 happening and offers more opportunity for optimisation. In
153	 particular, the compiler will be able to combine the byteswap
154	 with a nearby load or store and use load-and-swap or
155	 store-and-swap instructions if the architecture has them. It
156	 should almost *never* result in code which is worse than the
157	 hand-coded assembler in <asm/swab.h>.  But just in case it
158	 does, the use of the builtins is optional.
159
160	 Any architecture with load-and-swap or store-and-swap
161	 instructions should set this. And it shouldn't hurt to set it
162	 on architectures that don't have such instructions.
163
164config KRETPROBES
165	def_bool y
166	depends on KPROBES && HAVE_KRETPROBES
167
168config USER_RETURN_NOTIFIER
169	bool
170	depends on HAVE_USER_RETURN_NOTIFIER
171	help
172	  Provide a kernel-internal notification when a cpu is about to
173	  switch to user mode.
174
175config HAVE_IOREMAP_PROT
176	bool
177
178config HAVE_KPROBES
179	bool
180
181config HAVE_KRETPROBES
182	bool
183
184config HAVE_OPTPROBES
185	bool
186
187config HAVE_KPROBES_ON_FTRACE
188	bool
189
190config HAVE_NMI_WATCHDOG
191	bool
192#
193# An arch should select this if it provides all these things:
194#
195#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
196#	arch_has_single_step()	if there is hardware single-step support
197#	arch_has_block_step()	if there is hardware block-step support
198#	asm/syscall.h		supplying asm-generic/syscall.h interface
199#	linux/regset.h		user_regset interfaces
200#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
201#	TIF_SYSCALL_TRACE	calls tracehook_report_syscall_{entry,exit}
202#	TIF_NOTIFY_RESUME	calls tracehook_notify_resume()
203#	signal delivery		calls tracehook_signal_handler()
204#
205config HAVE_ARCH_TRACEHOOK
206	bool
207
208config HAVE_DMA_ATTRS
209	bool
210
211config HAVE_DMA_CONTIGUOUS
212	bool
213
214config GENERIC_SMP_IDLE_THREAD
215       bool
216
217config GENERIC_IDLE_POLL_SETUP
218       bool
219
220# Select if arch init_task initializer is different to init/init_task.c
221config ARCH_INIT_TASK
222       bool
223
224# Select if arch has its private alloc_task_struct() function
225config ARCH_TASK_STRUCT_ALLOCATOR
226	bool
227
228# Select if arch has its private alloc_thread_info() function
229config ARCH_THREAD_INFO_ALLOCATOR
230	bool
231
232# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
233config ARCH_WANTS_DYNAMIC_TASK_STRUCT
234	bool
235
236config HAVE_REGS_AND_STACK_ACCESS_API
237	bool
238	help
239	  This symbol should be selected by an architecure if it supports
240	  the API needed to access registers and stack entries from pt_regs,
241	  declared in asm/ptrace.h
242	  For example the kprobes-based event tracer needs this API.
243
244config HAVE_CLK
245	bool
246	help
247	  The <linux/clk.h> calls support software clock gating and
248	  thus are a key power management tool on many systems.
249
250config HAVE_DMA_API_DEBUG
251	bool
252
253config HAVE_HW_BREAKPOINT
254	bool
255	depends on PERF_EVENTS
256
257config HAVE_MIXED_BREAKPOINTS_REGS
258	bool
259	depends on HAVE_HW_BREAKPOINT
260	help
261	  Depending on the arch implementation of hardware breakpoints,
262	  some of them have separate registers for data and instruction
263	  breakpoints addresses, others have mixed registers to store
264	  them but define the access type in a control register.
265	  Select this option if your arch implements breakpoints under the
266	  latter fashion.
267
268config HAVE_USER_RETURN_NOTIFIER
269	bool
270
271config HAVE_PERF_EVENTS_NMI
272	bool
273	help
274	  System hardware can generate an NMI using the perf event
275	  subsystem.  Also has support for calculating CPU cycle events
276	  to determine how many clock cycles in a given period.
277
278config HAVE_PERF_REGS
279	bool
280	help
281	  Support selective register dumps for perf events. This includes
282	  bit-mapping of each registers and a unique architecture id.
283
284config HAVE_PERF_USER_STACK_DUMP
285	bool
286	help
287	  Support user stack dumps for perf event samples. This needs
288	  access to the user stack pointer which is not unified across
289	  architectures.
290
291config HAVE_ARCH_JUMP_LABEL
292	bool
293
294config HAVE_RCU_TABLE_FREE
295	bool
296
297config ARCH_HAVE_NMI_SAFE_CMPXCHG
298	bool
299
300config HAVE_ALIGNED_STRUCT_PAGE
301	bool
302	help
303	  This makes sure that struct pages are double word aligned and that
304	  e.g. the SLUB allocator can perform double word atomic operations
305	  on a struct page for better performance. However selecting this
306	  might increase the size of a struct page by a word.
307
308config HAVE_CMPXCHG_LOCAL
309	bool
310
311config HAVE_CMPXCHG_DOUBLE
312	bool
313
314config ARCH_WANT_IPC_PARSE_VERSION
315	bool
316
317config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
318	bool
319
320config ARCH_WANT_OLD_COMPAT_IPC
321	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
322	bool
323
324config HAVE_ARCH_SECCOMP_FILTER
325	bool
326	help
327	  An arch should select this symbol if it provides all of these things:
328	  - syscall_get_arch()
329	  - syscall_get_arguments()
330	  - syscall_rollback()
331	  - syscall_set_return_value()
332	  - SIGSYS siginfo_t support
333	  - secure_computing is called from a ptrace_event()-safe context
334	  - secure_computing return value is checked and a return value of -1
335	    results in the system call being skipped immediately.
336	  - seccomp syscall wired up
337
338	  For best performance, an arch should use seccomp_phase1 and
339	  seccomp_phase2 directly.  It should call seccomp_phase1 for all
340	  syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not
341	  need to be called from a ptrace-safe context.  It must then
342	  call seccomp_phase2 if seccomp_phase1 returns anything other
343	  than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP.
344
345	  As an additional optimization, an arch may provide seccomp_data
346	  directly to seccomp_phase1; this avoids multiple calls
347	  to the syscall_xyz helpers for every syscall.
348
349config SECCOMP_FILTER
350	def_bool y
351	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
352	help
353	  Enable tasks to build secure computing environments defined
354	  in terms of Berkeley Packet Filter programs which implement
355	  task-defined system call filtering polices.
356
357	  See Documentation/prctl/seccomp_filter.txt for details.
358
359config HAVE_CC_STACKPROTECTOR
360	bool
361	help
362	  An arch should select this symbol if:
363	  - its compiler supports the -fstack-protector option
364	  - it has implemented a stack canary (e.g. __stack_chk_guard)
365
366config CC_STACKPROTECTOR
367	def_bool n
368	help
369	  Set when a stack-protector mode is enabled, so that the build
370	  can enable kernel-side support for the GCC feature.
371
372choice
373	prompt "Stack Protector buffer overflow detection"
374	depends on HAVE_CC_STACKPROTECTOR
375	default CC_STACKPROTECTOR_NONE
376	help
377	  This option turns on the "stack-protector" GCC feature. This
378	  feature puts, at the beginning of functions, a canary value on
379	  the stack just before the return address, and validates
380	  the value just before actually returning.  Stack based buffer
381	  overflows (that need to overwrite this return address) now also
382	  overwrite the canary, which gets detected and the attack is then
383	  neutralized via a kernel panic.
384
385config CC_STACKPROTECTOR_NONE
386	bool "None"
387	help
388	  Disable "stack-protector" GCC feature.
389
390config CC_STACKPROTECTOR_REGULAR
391	bool "Regular"
392	select CC_STACKPROTECTOR
393	help
394	  Functions will have the stack-protector canary logic added if they
395	  have an 8-byte or larger character array on the stack.
396
397	  This feature requires gcc version 4.2 or above, or a distribution
398	  gcc with the feature backported ("-fstack-protector").
399
400	  On an x86 "defconfig" build, this feature adds canary checks to
401	  about 3% of all kernel functions, which increases kernel code size
402	  by about 0.3%.
403
404config CC_STACKPROTECTOR_STRONG
405	bool "Strong"
406	select CC_STACKPROTECTOR
407	help
408	  Functions will have the stack-protector canary logic added in any
409	  of the following conditions:
410
411	  - local variable's address used as part of the right hand side of an
412	    assignment or function argument
413	  - local variable is an array (or union containing an array),
414	    regardless of array type or length
415	  - uses register local variables
416
417	  This feature requires gcc version 4.9 or above, or a distribution
418	  gcc with the feature backported ("-fstack-protector-strong").
419
420	  On an x86 "defconfig" build, this feature adds canary checks to
421	  about 20% of all kernel functions, which increases the kernel code
422	  size by about 2%.
423
424endchoice
425
426config HAVE_CONTEXT_TRACKING
427	bool
428	help
429	  Provide kernel/user boundaries probes necessary for subsystems
430	  that need it, such as userspace RCU extended quiescent state.
431	  Syscalls need to be wrapped inside user_exit()-user_enter() through
432	  the slow path using TIF_NOHZ flag. Exceptions handlers must be
433	  wrapped as well. Irqs are already protected inside
434	  rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
435	  irq exit still need to be protected.
436
437config HAVE_VIRT_CPU_ACCOUNTING
438	bool
439
440config HAVE_VIRT_CPU_ACCOUNTING_GEN
441	bool
442	default y if 64BIT
443	help
444	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
445	  Before enabling this option, arch code must be audited
446	  to ensure there are no races in concurrent read/write of
447	  cputime_t. For example, reading/writing 64-bit cputime_t on
448	  some 32-bit arches may require multiple accesses, so proper
449	  locking is needed to protect against concurrent accesses.
450
451
452config HAVE_IRQ_TIME_ACCOUNTING
453	bool
454	help
455	  Archs need to ensure they use a high enough resolution clock to
456	  support irq time accounting and then call enable_sched_clock_irqtime().
457
458config HAVE_ARCH_TRANSPARENT_HUGEPAGE
459	bool
460
461config HAVE_ARCH_HUGE_VMAP
462	bool
463
464config HAVE_ARCH_SOFT_DIRTY
465	bool
466
467config HAVE_MOD_ARCH_SPECIFIC
468	bool
469	help
470	  The arch uses struct mod_arch_specific to store data.  Many arches
471	  just need a simple module loader without arch specific data - those
472	  should not enable this.
473
474config MODULES_USE_ELF_RELA
475	bool
476	help
477	  Modules only use ELF RELA relocations.  Modules with ELF REL
478	  relocations will give an error.
479
480config MODULES_USE_ELF_REL
481	bool
482	help
483	  Modules only use ELF REL relocations.  Modules with ELF RELA
484	  relocations will give an error.
485
486config HAVE_UNDERSCORE_SYMBOL_PREFIX
487	bool
488	help
489	  Some architectures generate an _ in front of C symbols; things like
490	  module loading and assembly files need to know about this.
491
492config HAVE_IRQ_EXIT_ON_IRQ_STACK
493	bool
494	help
495	  Architecture doesn't only execute the irq handler on the irq stack
496	  but also irq_exit(). This way we can process softirqs on this irq
497	  stack instead of switching to a new one when we call __do_softirq()
498	  in the end of an hardirq.
499	  This spares a stack switch and improves cache usage on softirq
500	  processing.
501
502config PGTABLE_LEVELS
503	int
504	default 2
505
506config ARCH_HAS_ELF_RANDOMIZE
507	bool
508	help
509	  An architecture supports choosing randomized locations for
510	  stack, mmap, brk, and ET_DYN. Defined functions:
511	  - arch_mmap_rnd()
512	  - arch_randomize_brk()
513
514config HAVE_COPY_THREAD_TLS
515	bool
516	help
517	  Architecture provides copy_thread_tls to accept tls argument via
518	  normal C parameter passing, rather than extracting the syscall
519	  argument from pt_regs.
520
521#
522# ABI hall of shame
523#
524config CLONE_BACKWARDS
525	bool
526	help
527	  Architecture has tls passed as the 4th argument of clone(2),
528	  not the 5th one.
529
530config CLONE_BACKWARDS2
531	bool
532	help
533	  Architecture has the first two arguments of clone(2) swapped.
534
535config CLONE_BACKWARDS3
536	bool
537	help
538	  Architecture has tls passed as the 3rd argument of clone(2),
539	  not the 5th one.
540
541config ODD_RT_SIGACTION
542	bool
543	help
544	  Architecture has unusual rt_sigaction(2) arguments
545
546config OLD_SIGSUSPEND
547	bool
548	help
549	  Architecture has old sigsuspend(2) syscall, of one-argument variety
550
551config OLD_SIGSUSPEND3
552	bool
553	help
554	  Even weirder antique ABI - three-argument sigsuspend(2)
555
556config OLD_SIGACTION
557	bool
558	help
559	  Architecture has old sigaction(2) syscall.  Nope, not the same
560	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
561	  but fairly different variant of sigaction(2), thanks to OSF/1
562	  compatibility...
563
564config COMPAT_OLD_SIGACTION
565	bool
566
567source "kernel/gcov/Kconfig"
568