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v4.17
  1# SPDX-License-Identifier: GPL-2.0
  2#
  3# General architecture dependent options
  4#
  5
  6config CRASH_CORE
  7	bool
  8
  9config KEXEC_CORE
 10	select CRASH_CORE
 11	bool
 12
 13config HAVE_IMA_KEXEC
 14	bool
 15
 16config OPROFILE
 17	tristate "OProfile system profiling"
 18	depends on PROFILING
 19	depends on HAVE_OPROFILE
 20	select RING_BUFFER
 21	select RING_BUFFER_ALLOW_SWAP
 22	help
 23	  OProfile is a profiling system capable of profiling the
 24	  whole system, include the kernel, kernel modules, libraries,
 25	  and applications.
 26
 27	  If unsure, say N.
 28
 29config OPROFILE_EVENT_MULTIPLEX
 30	bool "OProfile multiplexing support (EXPERIMENTAL)"
 31	default n
 32	depends on OPROFILE && X86
 33	help
 34	  The number of hardware counters is limited. The multiplexing
 35	  feature enables OProfile to gather more events than counters
 36	  are provided by the hardware. This is realized by switching
 37	  between events at a user specified time interval.
 38
 39	  If unsure, say N.
 40
 41config HAVE_OPROFILE
 42	bool
 43
 44config OPROFILE_NMI_TIMER
 45	def_bool y
 46	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
 47
 48config KPROBES
 49	bool "Kprobes"
 50	depends on MODULES
 51	depends on HAVE_KPROBES
 52	select KALLSYMS
 53	help
 54	  Kprobes allows you to trap at almost any kernel address and
 55	  execute a callback function.  register_kprobe() establishes
 56	  a probepoint and specifies the callback.  Kprobes is useful
 57	  for kernel debugging, non-intrusive instrumentation and testing.
 58	  If in doubt, say "N".
 59
 60config JUMP_LABEL
 61       bool "Optimize very unlikely/likely branches"
 62       depends on HAVE_ARCH_JUMP_LABEL
 63       help
 64         This option enables a transparent branch optimization that
 65	 makes certain almost-always-true or almost-always-false branch
 66	 conditions even cheaper to execute within the kernel.
 67
 68	 Certain performance-sensitive kernel code, such as trace points,
 69	 scheduler functionality, networking code and KVM have such
 70	 branches and include support for this optimization technique.
 71
 72         If it is detected that the compiler has support for "asm goto",
 73	 the kernel will compile such branches with just a nop
 74	 instruction. When the condition flag is toggled to true, the
 75	 nop will be converted to a jump instruction to execute the
 76	 conditional block of instructions.
 77
 78	 This technique lowers overhead and stress on the branch prediction
 79	 of the processor and generally makes the kernel faster. The update
 80	 of the condition is slower, but those are always very rare.
 81
 82	 ( On 32-bit x86, the necessary options added to the compiler
 83	   flags may increase the size of the kernel slightly. )
 84
 85config STATIC_KEYS_SELFTEST
 86	bool "Static key selftest"
 87	depends on JUMP_LABEL
 88	help
 89	  Boot time self-test of the branch patching code.
 90
 91config OPTPROBES
 92	def_bool y
 93	depends on KPROBES && HAVE_OPTPROBES
 94	select TASKS_RCU if PREEMPT
 95
 96config KPROBES_ON_FTRACE
 97	def_bool y
 98	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 99	depends on DYNAMIC_FTRACE_WITH_REGS
100	help
101	 If function tracer is enabled and the arch supports full
102	 passing of pt_regs to function tracing, then kprobes can
103	 optimize on top of function tracing.
104
105config UPROBES
106	def_bool n
107	depends on ARCH_SUPPORTS_UPROBES
108	help
109	  Uprobes is the user-space counterpart to kprobes: they
110	  enable instrumentation applications (such as 'perf probe')
111	  to establish unintrusive probes in user-space binaries and
112	  libraries, by executing handler functions when the probes
113	  are hit by user-space applications.
114
115	  ( These probes come in the form of single-byte breakpoints,
116	    managed by the kernel and kept transparent to the probed
117	    application. )
118
119config HAVE_64BIT_ALIGNED_ACCESS
120	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
121	help
122	  Some architectures require 64 bit accesses to be 64 bit
123	  aligned, which also requires structs containing 64 bit values
124	  to be 64 bit aligned too. This includes some 32 bit
125	  architectures which can do 64 bit accesses, as well as 64 bit
126	  architectures without unaligned access.
127
128	  This symbol should be selected by an architecture if 64 bit
129	  accesses are required to be 64 bit aligned in this way even
130	  though it is not a 64 bit architecture.
131
132	  See Documentation/unaligned-memory-access.txt for more
133	  information on the topic of unaligned memory accesses.
134
135config HAVE_EFFICIENT_UNALIGNED_ACCESS
136	bool
137	help
138	  Some architectures are unable to perform unaligned accesses
139	  without the use of get_unaligned/put_unaligned. Others are
140	  unable to perform such accesses efficiently (e.g. trap on
141	  unaligned access and require fixing it up in the exception
142	  handler.)
143
144	  This symbol should be selected by an architecture if it can
145	  perform unaligned accesses efficiently to allow different
146	  code paths to be selected for these cases. Some network
147	  drivers, for example, could opt to not fix up alignment
148	  problems with received packets if doing so would not help
149	  much.
150
151	  See Documentation/unaligned-memory-access.txt for more
152	  information on the topic of unaligned memory accesses.
153
154config ARCH_USE_BUILTIN_BSWAP
155       bool
156       help
157	 Modern versions of GCC (since 4.4) have builtin functions
158	 for handling byte-swapping. Using these, instead of the old
159	 inline assembler that the architecture code provides in the
160	 __arch_bswapXX() macros, allows the compiler to see what's
161	 happening and offers more opportunity for optimisation. In
162	 particular, the compiler will be able to combine the byteswap
163	 with a nearby load or store and use load-and-swap or
164	 store-and-swap instructions if the architecture has them. It
165	 should almost *never* result in code which is worse than the
166	 hand-coded assembler in <asm/swab.h>.  But just in case it
167	 does, the use of the builtins is optional.
168
169	 Any architecture with load-and-swap or store-and-swap
170	 instructions should set this. And it shouldn't hurt to set it
171	 on architectures that don't have such instructions.
172
173config KRETPROBES
174	def_bool y
175	depends on KPROBES && HAVE_KRETPROBES
176
177config USER_RETURN_NOTIFIER
178	bool
179	depends on HAVE_USER_RETURN_NOTIFIER
180	help
181	  Provide a kernel-internal notification when a cpu is about to
182	  switch to user mode.
183
184config HAVE_IOREMAP_PROT
185	bool
186
187config HAVE_KPROBES
188	bool
189
190config HAVE_KRETPROBES
191	bool
192
193config HAVE_OPTPROBES
194	bool
195
196config HAVE_KPROBES_ON_FTRACE
197	bool
198
199config HAVE_FUNCTION_ERROR_INJECTION
200	bool
201
202config HAVE_NMI
203	bool
204
 
 
 
205#
206# An arch should select this if it provides all these things:
207#
208#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
209#	arch_has_single_step()	if there is hardware single-step support
210#	arch_has_block_step()	if there is hardware block-step support
211#	asm/syscall.h		supplying asm-generic/syscall.h interface
212#	linux/regset.h		user_regset interfaces
213#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
214#	TIF_SYSCALL_TRACE	calls tracehook_report_syscall_{entry,exit}
215#	TIF_NOTIFY_RESUME	calls tracehook_notify_resume()
216#	signal delivery		calls tracehook_signal_handler()
217#
218config HAVE_ARCH_TRACEHOOK
219	bool
220
221config HAVE_DMA_CONTIGUOUS
222	bool
223
224config GENERIC_SMP_IDLE_THREAD
225       bool
226
227config GENERIC_IDLE_POLL_SETUP
228       bool
229
230config ARCH_HAS_FORTIFY_SOURCE
231	bool
232	help
233	  An architecture should select this when it can successfully
234	  build and run with CONFIG_FORTIFY_SOURCE.
235
236# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
237config ARCH_HAS_SET_MEMORY
238	bool
239
240# Select if arch init_task must go in the __init_task_data section
241config ARCH_TASK_STRUCT_ON_STACK
242       bool
243
244# Select if arch has its private alloc_task_struct() function
245config ARCH_TASK_STRUCT_ALLOCATOR
246	bool
247
248config HAVE_ARCH_THREAD_STRUCT_WHITELIST
249	bool
250	depends on !ARCH_TASK_STRUCT_ALLOCATOR
251	help
252	  An architecture should select this to provide hardened usercopy
253	  knowledge about what region of the thread_struct should be
254	  whitelisted for copying to userspace. Normally this is only the
255	  FPU registers. Specifically, arch_thread_struct_whitelist()
256	  should be implemented. Without this, the entire thread_struct
257	  field in task_struct will be left whitelisted.
258
259# Select if arch has its private alloc_thread_stack() function
260config ARCH_THREAD_STACK_ALLOCATOR
261	bool
262
263# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
264config ARCH_WANTS_DYNAMIC_TASK_STRUCT
265	bool
266
267config HAVE_REGS_AND_STACK_ACCESS_API
268	bool
269	help
270	  This symbol should be selected by an architecure if it supports
271	  the API needed to access registers and stack entries from pt_regs,
272	  declared in asm/ptrace.h
273	  For example the kprobes-based event tracer needs this API.
274
275config HAVE_CLK
276	bool
277	help
278	  The <linux/clk.h> calls support software clock gating and
279	  thus are a key power management tool on many systems.
280
281config HAVE_DMA_API_DEBUG
282	bool
283
284config HAVE_HW_BREAKPOINT
285	bool
286	depends on PERF_EVENTS
287
288config HAVE_MIXED_BREAKPOINTS_REGS
289	bool
290	depends on HAVE_HW_BREAKPOINT
291	help
292	  Depending on the arch implementation of hardware breakpoints,
293	  some of them have separate registers for data and instruction
294	  breakpoints addresses, others have mixed registers to store
295	  them but define the access type in a control register.
296	  Select this option if your arch implements breakpoints under the
297	  latter fashion.
298
299config HAVE_USER_RETURN_NOTIFIER
300	bool
301
302config HAVE_PERF_EVENTS_NMI
303	bool
304	help
305	  System hardware can generate an NMI using the perf event
306	  subsystem.  Also has support for calculating CPU cycle events
307	  to determine how many clock cycles in a given period.
308
309config HAVE_HARDLOCKUP_DETECTOR_PERF
310	bool
311	depends on HAVE_PERF_EVENTS_NMI
312	help
313	  The arch chooses to use the generic perf-NMI-based hardlockup
314	  detector. Must define HAVE_PERF_EVENTS_NMI.
315
316config HAVE_NMI_WATCHDOG
317	depends on HAVE_NMI
318	bool
319	help
320	  The arch provides a low level NMI watchdog. It provides
321	  asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
322
323config HAVE_HARDLOCKUP_DETECTOR_ARCH
324	bool
325	select HAVE_NMI_WATCHDOG
326	help
327	  The arch chooses to provide its own hardlockup detector, which is
328	  a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
329	  interfaces and parameters provided by hardlockup detector subsystem.
330
331config HAVE_PERF_REGS
332	bool
333	help
334	  Support selective register dumps for perf events. This includes
335	  bit-mapping of each registers and a unique architecture id.
336
337config HAVE_PERF_USER_STACK_DUMP
338	bool
339	help
340	  Support user stack dumps for perf event samples. This needs
341	  access to the user stack pointer which is not unified across
342	  architectures.
343
344config HAVE_ARCH_JUMP_LABEL
345	bool
346
347config HAVE_RCU_TABLE_FREE
348	bool
349
350config ARCH_HAVE_NMI_SAFE_CMPXCHG
351	bool
352
353config HAVE_ALIGNED_STRUCT_PAGE
354	bool
355	help
356	  This makes sure that struct pages are double word aligned and that
357	  e.g. the SLUB allocator can perform double word atomic operations
358	  on a struct page for better performance. However selecting this
359	  might increase the size of a struct page by a word.
360
361config HAVE_CMPXCHG_LOCAL
362	bool
363
364config HAVE_CMPXCHG_DOUBLE
365	bool
366
367config ARCH_WEAK_RELEASE_ACQUIRE
368	bool
369
370config ARCH_WANT_IPC_PARSE_VERSION
371	bool
372
373config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
374	bool
375
376config ARCH_WANT_OLD_COMPAT_IPC
377	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
378	bool
379
380config HAVE_ARCH_SECCOMP_FILTER
381	bool
382	help
383	  An arch should select this symbol if it provides all of these things:
384	  - syscall_get_arch()
385	  - syscall_get_arguments()
386	  - syscall_rollback()
387	  - syscall_set_return_value()
388	  - SIGSYS siginfo_t support
389	  - secure_computing is called from a ptrace_event()-safe context
390	  - secure_computing return value is checked and a return value of -1
391	    results in the system call being skipped immediately.
392	  - seccomp syscall wired up
393
394config SECCOMP_FILTER
395	def_bool y
396	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
397	help
398	  Enable tasks to build secure computing environments defined
399	  in terms of Berkeley Packet Filter programs which implement
400	  task-defined system call filtering polices.
401
402	  See Documentation/prctl/seccomp_filter.txt for details.
403
404config HAVE_GCC_PLUGINS
405	bool
406	help
407	  An arch should select this symbol if it supports building with
408	  GCC plugins.
409
410menuconfig GCC_PLUGINS
411	bool "GCC plugins"
412	depends on HAVE_GCC_PLUGINS
413	depends on !COMPILE_TEST
414	help
415	  GCC plugins are loadable modules that provide extra features to the
416	  compiler. They are useful for runtime instrumentation and static analysis.
417
418	  See Documentation/gcc-plugins.txt for details.
419
420config GCC_PLUGIN_CYC_COMPLEXITY
421	bool "Compute the cyclomatic complexity of a function" if EXPERT
422	depends on GCC_PLUGINS
423	depends on !COMPILE_TEST
424	help
425	  The complexity M of a function's control flow graph is defined as:
426	   M = E - N + 2P
427	  where
428
429	  E = the number of edges
430	  N = the number of nodes
431	  P = the number of connected components (exit nodes).
432
433	  Enabling this plugin reports the complexity to stderr during the
434	  build. It mainly serves as a simple example of how to create a
435	  gcc plugin for the kernel.
436
437config GCC_PLUGIN_SANCOV
438	bool
439	depends on GCC_PLUGINS
440	help
441	  This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
442	  basic blocks. It supports all gcc versions with plugin support (from
443	  gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
444	  by Dmitry Vyukov <dvyukov@google.com>.
445
446config GCC_PLUGIN_LATENT_ENTROPY
447	bool "Generate some entropy during boot and runtime"
448	depends on GCC_PLUGINS
449	help
450	  By saying Y here the kernel will instrument some kernel code to
451	  extract some entropy from both original and artificially created
452	  program state.  This will help especially embedded systems where
453	  there is little 'natural' source of entropy normally.  The cost
454	  is some slowdown of the boot process (about 0.5%) and fork and
455	  irq processing.
456
457	  Note that entropy extracted this way is not cryptographically
458	  secure!
459
460	  This plugin was ported from grsecurity/PaX. More information at:
461	   * https://grsecurity.net/
462	   * https://pax.grsecurity.net/
463
464config GCC_PLUGIN_STRUCTLEAK
465	bool "Force initialization of variables containing userspace addresses"
466	depends on GCC_PLUGINS
467	# Currently STRUCTLEAK inserts initialization out of live scope of
468	# variables from KASAN point of view. This leads to KASAN false
469	# positive reports. Prohibit this combination for now.
470	depends on !KASAN_EXTRA
471	help
472	  This plugin zero-initializes any structures containing a
473	  __user attribute. This can prevent some classes of information
474	  exposures.
475
476	  This plugin was ported from grsecurity/PaX. More information at:
477	   * https://grsecurity.net/
478	   * https://pax.grsecurity.net/
479
480config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
481	bool "Force initialize all struct type variables passed by reference"
482	depends on GCC_PLUGIN_STRUCTLEAK
483	help
484	  Zero initialize any struct type local variable that may be passed by
485	  reference without having been initialized.
486
487config GCC_PLUGIN_STRUCTLEAK_VERBOSE
488	bool "Report forcefully initialized variables"
489	depends on GCC_PLUGIN_STRUCTLEAK
490	depends on !COMPILE_TEST
491	help
492	  This option will cause a warning to be printed each time the
493	  structleak plugin finds a variable it thinks needs to be
494	  initialized. Since not all existing initializers are detected
495	  by the plugin, this can produce false positive warnings.
496
497config GCC_PLUGIN_RANDSTRUCT
498	bool "Randomize layout of sensitive kernel structures"
499	depends on GCC_PLUGINS
500	select MODVERSIONS if MODULES
501	help
502	  If you say Y here, the layouts of structures that are entirely
503	  function pointers (and have not been manually annotated with
504	  __no_randomize_layout), or structures that have been explicitly
505	  marked with __randomize_layout, will be randomized at compile-time.
506	  This can introduce the requirement of an additional information
507	  exposure vulnerability for exploits targeting these structure
508	  types.
509
510	  Enabling this feature will introduce some performance impact,
511	  slightly increase memory usage, and prevent the use of forensic
512	  tools like Volatility against the system (unless the kernel
513	  source tree isn't cleaned after kernel installation).
514
515	  The seed used for compilation is located at
516	  scripts/gcc-plgins/randomize_layout_seed.h.  It remains after
517	  a make clean to allow for external modules to be compiled with
518	  the existing seed and will be removed by a make mrproper or
519	  make distclean.
520
521	  Note that the implementation requires gcc 4.7 or newer.
522
523	  This plugin was ported from grsecurity/PaX. More information at:
524	   * https://grsecurity.net/
525	   * https://pax.grsecurity.net/
526
527config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
528	bool "Use cacheline-aware structure randomization"
529	depends on GCC_PLUGIN_RANDSTRUCT
530	depends on !COMPILE_TEST
531	help
532	  If you say Y here, the RANDSTRUCT randomization will make a
533	  best effort at restricting randomization to cacheline-sized
534	  groups of elements.  It will further not randomize bitfields
535	  in structures.  This reduces the performance hit of RANDSTRUCT
536	  at the cost of weakened randomization.
537
538config HAVE_CC_STACKPROTECTOR
539	bool
540	help
541	  An arch should select this symbol if:
542	  - its compiler supports the -fstack-protector option
543	  - it has implemented a stack canary (e.g. __stack_chk_guard)
544
 
 
 
 
 
 
545choice
546	prompt "Stack Protector buffer overflow detection"
547	depends on HAVE_CC_STACKPROTECTOR
548	default CC_STACKPROTECTOR_AUTO
549	help
550	  This option turns on the "stack-protector" GCC feature. This
551	  feature puts, at the beginning of functions, a canary value on
552	  the stack just before the return address, and validates
553	  the value just before actually returning.  Stack based buffer
554	  overflows (that need to overwrite this return address) now also
555	  overwrite the canary, which gets detected and the attack is then
556	  neutralized via a kernel panic.
557
558config CC_STACKPROTECTOR_NONE
559	bool "None"
560	help
561	  Disable "stack-protector" GCC feature.
562
563config CC_STACKPROTECTOR_REGULAR
564	bool "Regular"
 
565	help
566	  Functions will have the stack-protector canary logic added if they
567	  have an 8-byte or larger character array on the stack.
568
569	  This feature requires gcc version 4.2 or above, or a distribution
570	  gcc with the feature backported ("-fstack-protector").
571
572	  On an x86 "defconfig" build, this feature adds canary checks to
573	  about 3% of all kernel functions, which increases kernel code size
574	  by about 0.3%.
575
576config CC_STACKPROTECTOR_STRONG
577	bool "Strong"
 
578	help
579	  Functions will have the stack-protector canary logic added in any
580	  of the following conditions:
581
582	  - local variable's address used as part of the right hand side of an
583	    assignment or function argument
584	  - local variable is an array (or union containing an array),
585	    regardless of array type or length
586	  - uses register local variables
587
588	  This feature requires gcc version 4.9 or above, or a distribution
589	  gcc with the feature backported ("-fstack-protector-strong").
590
591	  On an x86 "defconfig" build, this feature adds canary checks to
592	  about 20% of all kernel functions, which increases the kernel code
593	  size by about 2%.
594
595config CC_STACKPROTECTOR_AUTO
596	bool "Automatic"
597	help
598	  If the compiler supports it, the best available stack-protector
599	  option will be chosen.
600
601endchoice
602
 
 
 
 
 
 
603config LD_DEAD_CODE_DATA_ELIMINATION
604	bool
605	help
606	  Select this if the architecture wants to do dead code and
607	  data elimination with the linker by compiling with
608	  -ffunction-sections -fdata-sections and linking with
609	  --gc-sections.
610
611	  This requires that the arch annotates or otherwise protects
612	  its external entry points from being discarded. Linker scripts
613	  must also merge .text.*, .data.*, and .bss.* correctly into
614	  output sections. Care must be taken not to pull in unrelated
615	  sections (e.g., '.text.init'). Typically '.' in section names
616	  is used to distinguish them from label names / C identifiers.
617
618config HAVE_ARCH_WITHIN_STACK_FRAMES
619	bool
620	help
621	  An architecture should select this if it can walk the kernel stack
622	  frames to determine if an object is part of either the arguments
623	  or local variables (i.e. that it excludes saved return addresses,
624	  and similar) by implementing an inline arch_within_stack_frames(),
625	  which is used by CONFIG_HARDENED_USERCOPY.
626
627config HAVE_CONTEXT_TRACKING
628	bool
629	help
630	  Provide kernel/user boundaries probes necessary for subsystems
631	  that need it, such as userspace RCU extended quiescent state.
632	  Syscalls need to be wrapped inside user_exit()-user_enter() through
633	  the slow path using TIF_NOHZ flag. Exceptions handlers must be
634	  wrapped as well. Irqs are already protected inside
635	  rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
636	  irq exit still need to be protected.
637
638config HAVE_VIRT_CPU_ACCOUNTING
639	bool
640
641config ARCH_HAS_SCALED_CPUTIME
642	bool
643
644config HAVE_VIRT_CPU_ACCOUNTING_GEN
645	bool
646	default y if 64BIT
647	help
648	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
649	  Before enabling this option, arch code must be audited
650	  to ensure there are no races in concurrent read/write of
651	  cputime_t. For example, reading/writing 64-bit cputime_t on
652	  some 32-bit arches may require multiple accesses, so proper
653	  locking is needed to protect against concurrent accesses.
654
655
656config HAVE_IRQ_TIME_ACCOUNTING
657	bool
658	help
659	  Archs need to ensure they use a high enough resolution clock to
660	  support irq time accounting and then call enable_sched_clock_irqtime().
661
662config HAVE_ARCH_TRANSPARENT_HUGEPAGE
663	bool
664
665config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
666	bool
667
668config HAVE_ARCH_HUGE_VMAP
669	bool
670
671config HAVE_ARCH_SOFT_DIRTY
672	bool
673
674config HAVE_MOD_ARCH_SPECIFIC
675	bool
676	help
677	  The arch uses struct mod_arch_specific to store data.  Many arches
678	  just need a simple module loader without arch specific data - those
679	  should not enable this.
680
681config MODULES_USE_ELF_RELA
682	bool
683	help
684	  Modules only use ELF RELA relocations.  Modules with ELF REL
685	  relocations will give an error.
686
687config MODULES_USE_ELF_REL
688	bool
689	help
690	  Modules only use ELF REL relocations.  Modules with ELF RELA
691	  relocations will give an error.
692
693config HAVE_UNDERSCORE_SYMBOL_PREFIX
694	bool
695	help
696	  Some architectures generate an _ in front of C symbols; things like
697	  module loading and assembly files need to know about this.
698
699config HAVE_IRQ_EXIT_ON_IRQ_STACK
700	bool
701	help
702	  Architecture doesn't only execute the irq handler on the irq stack
703	  but also irq_exit(). This way we can process softirqs on this irq
704	  stack instead of switching to a new one when we call __do_softirq()
705	  in the end of an hardirq.
706	  This spares a stack switch and improves cache usage on softirq
707	  processing.
708
709config PGTABLE_LEVELS
710	int
711	default 2
712
713config ARCH_HAS_ELF_RANDOMIZE
714	bool
715	help
716	  An architecture supports choosing randomized locations for
717	  stack, mmap, brk, and ET_DYN. Defined functions:
718	  - arch_mmap_rnd()
719	  - arch_randomize_brk()
720
721config HAVE_ARCH_MMAP_RND_BITS
722	bool
723	help
724	  An arch should select this symbol if it supports setting a variable
725	  number of bits for use in establishing the base address for mmap
726	  allocations, has MMU enabled and provides values for both:
727	  - ARCH_MMAP_RND_BITS_MIN
728	  - ARCH_MMAP_RND_BITS_MAX
729
730config HAVE_EXIT_THREAD
731	bool
732	help
733	  An architecture implements exit_thread.
734
735config ARCH_MMAP_RND_BITS_MIN
736	int
737
738config ARCH_MMAP_RND_BITS_MAX
739	int
740
741config ARCH_MMAP_RND_BITS_DEFAULT
742	int
743
744config ARCH_MMAP_RND_BITS
745	int "Number of bits to use for ASLR of mmap base address" if EXPERT
746	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
747	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
748	default ARCH_MMAP_RND_BITS_MIN
749	depends on HAVE_ARCH_MMAP_RND_BITS
750	help
751	  This value can be used to select the number of bits to use to
752	  determine the random offset to the base address of vma regions
753	  resulting from mmap allocations. This value will be bounded
754	  by the architecture's minimum and maximum supported values.
755
756	  This value can be changed after boot using the
757	  /proc/sys/vm/mmap_rnd_bits tunable
758
759config HAVE_ARCH_MMAP_RND_COMPAT_BITS
760	bool
761	help
762	  An arch should select this symbol if it supports running applications
763	  in compatibility mode, supports setting a variable number of bits for
764	  use in establishing the base address for mmap allocations, has MMU
765	  enabled and provides values for both:
766	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
767	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
768
769config ARCH_MMAP_RND_COMPAT_BITS_MIN
770	int
771
772config ARCH_MMAP_RND_COMPAT_BITS_MAX
773	int
774
775config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
776	int
777
778config ARCH_MMAP_RND_COMPAT_BITS
779	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
780	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
781	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
782	default ARCH_MMAP_RND_COMPAT_BITS_MIN
783	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
784	help
785	  This value can be used to select the number of bits to use to
786	  determine the random offset to the base address of vma regions
787	  resulting from mmap allocations for compatible applications This
788	  value will be bounded by the architecture's minimum and maximum
789	  supported values.
790
791	  This value can be changed after boot using the
792	  /proc/sys/vm/mmap_rnd_compat_bits tunable
793
794config HAVE_ARCH_COMPAT_MMAP_BASES
795	bool
796	help
797	  This allows 64bit applications to invoke 32-bit mmap() syscall
798	  and vice-versa 32-bit applications to call 64-bit mmap().
799	  Required for applications doing different bitness syscalls.
800
801config HAVE_COPY_THREAD_TLS
802	bool
803	help
804	  Architecture provides copy_thread_tls to accept tls argument via
805	  normal C parameter passing, rather than extracting the syscall
806	  argument from pt_regs.
807
808config HAVE_STACK_VALIDATION
809	bool
810	help
811	  Architecture supports the 'objtool check' host tool command, which
812	  performs compile-time stack metadata validation.
813
814config HAVE_RELIABLE_STACKTRACE
815	bool
816	help
817	  Architecture has a save_stack_trace_tsk_reliable() function which
818	  only returns a stack trace if it can guarantee the trace is reliable.
819
820config HAVE_ARCH_HASH
821	bool
822	default n
823	help
824	  If this is set, the architecture provides an <asm/hash.h>
825	  file which provides platform-specific implementations of some
826	  functions in <linux/hash.h> or fs/namei.c.
827
828config ISA_BUS_API
829	def_bool ISA
830
831#
832# ABI hall of shame
833#
834config CLONE_BACKWARDS
835	bool
836	help
837	  Architecture has tls passed as the 4th argument of clone(2),
838	  not the 5th one.
839
840config CLONE_BACKWARDS2
841	bool
842	help
843	  Architecture has the first two arguments of clone(2) swapped.
844
845config CLONE_BACKWARDS3
846	bool
847	help
848	  Architecture has tls passed as the 3rd argument of clone(2),
849	  not the 5th one.
850
851config ODD_RT_SIGACTION
852	bool
853	help
854	  Architecture has unusual rt_sigaction(2) arguments
855
856config OLD_SIGSUSPEND
857	bool
858	help
859	  Architecture has old sigsuspend(2) syscall, of one-argument variety
860
861config OLD_SIGSUSPEND3
862	bool
863	help
864	  Even weirder antique ABI - three-argument sigsuspend(2)
865
866config OLD_SIGACTION
867	bool
868	help
869	  Architecture has old sigaction(2) syscall.  Nope, not the same
870	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
871	  but fairly different variant of sigaction(2), thanks to OSF/1
872	  compatibility...
873
874config COMPAT_OLD_SIGACTION
875	bool
876
877config ARCH_NO_COHERENT_DMA_MMAP
878	bool
879
880config CPU_NO_EFFICIENT_FFS
881	def_bool n
882
883config HAVE_ARCH_VMAP_STACK
884	def_bool n
885	help
886	  An arch should select this symbol if it can support kernel stacks
887	  in vmalloc space.  This means:
888
889	  - vmalloc space must be large enough to hold many kernel stacks.
890	    This may rule out many 32-bit architectures.
891
892	  - Stacks in vmalloc space need to work reliably.  For example, if
893	    vmap page tables are created on demand, either this mechanism
894	    needs to work while the stack points to a virtual address with
895	    unpopulated page tables or arch code (switch_to() and switch_mm(),
896	    most likely) needs to ensure that the stack's page table entries
897	    are populated before running on a possibly unpopulated stack.
898
899	  - If the stack overflows into a guard page, something reasonable
900	    should happen.  The definition of "reasonable" is flexible, but
901	    instantly rebooting without logging anything would be unfriendly.
902
903config VMAP_STACK
904	default y
905	bool "Use a virtually-mapped stack"
906	depends on HAVE_ARCH_VMAP_STACK && !KASAN
907	---help---
908	  Enable this if you want the use virtually-mapped kernel stacks
909	  with guard pages.  This causes kernel stack overflows to be
910	  caught immediately rather than causing difficult-to-diagnose
911	  corruption.
912
913	  This is presently incompatible with KASAN because KASAN expects
914	  the stack to map directly to the KASAN shadow map using a formula
915	  that is incorrect if the stack is in vmalloc space.
916
917config ARCH_OPTIONAL_KERNEL_RWX
918	def_bool n
919
920config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
921	def_bool n
922
923config ARCH_HAS_STRICT_KERNEL_RWX
924	def_bool n
925
926config STRICT_KERNEL_RWX
927	bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
928	depends on ARCH_HAS_STRICT_KERNEL_RWX
929	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
930	help
931	  If this is set, kernel text and rodata memory will be made read-only,
932	  and non-text memory will be made non-executable. This provides
933	  protection against certain security exploits (e.g. executing the heap
934	  or modifying text)
935
936	  These features are considered standard security practice these days.
937	  You should say Y here in almost all cases.
938
939config ARCH_HAS_STRICT_MODULE_RWX
940	def_bool n
941
942config STRICT_MODULE_RWX
943	bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
944	depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
945	default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
946	help
947	  If this is set, module text and rodata memory will be made read-only,
948	  and non-text memory will be made non-executable. This provides
949	  protection against certain security exploits (e.g. writing to text)
950
951# select if the architecture provides an asm/dma-direct.h header
952config ARCH_HAS_PHYS_TO_DMA
953	bool
954
955config ARCH_HAS_REFCOUNT
956	bool
957	help
958	  An architecture selects this when it has implemented refcount_t
959	  using open coded assembly primitives that provide an optimized
960	  refcount_t implementation, possibly at the expense of some full
961	  refcount state checks of CONFIG_REFCOUNT_FULL=y.
962
963	  The refcount overflow check behavior, however, must be retained.
964	  Catching overflows is the primary security concern for protecting
965	  against bugs in reference counts.
966
967config REFCOUNT_FULL
968	bool "Perform full reference count validation at the expense of speed"
969	help
970	  Enabling this switches the refcounting infrastructure from a fast
971	  unchecked atomic_t implementation to a fully state checked
972	  implementation, which can be (slightly) slower but provides protections
973	  against various use-after-free conditions that can be used in
974	  security flaw exploits.
975
976source "kernel/gcov/Kconfig"
v4.10.11
 
  1#
  2# General architecture dependent options
  3#
  4
 
 
 
  5config KEXEC_CORE
 
  6	bool
  7
  8config HAVE_IMA_KEXEC
  9	bool
 10
 11config OPROFILE
 12	tristate "OProfile system profiling"
 13	depends on PROFILING
 14	depends on HAVE_OPROFILE
 15	select RING_BUFFER
 16	select RING_BUFFER_ALLOW_SWAP
 17	help
 18	  OProfile is a profiling system capable of profiling the
 19	  whole system, include the kernel, kernel modules, libraries,
 20	  and applications.
 21
 22	  If unsure, say N.
 23
 24config OPROFILE_EVENT_MULTIPLEX
 25	bool "OProfile multiplexing support (EXPERIMENTAL)"
 26	default n
 27	depends on OPROFILE && X86
 28	help
 29	  The number of hardware counters is limited. The multiplexing
 30	  feature enables OProfile to gather more events than counters
 31	  are provided by the hardware. This is realized by switching
 32	  between events at an user specified time interval.
 33
 34	  If unsure, say N.
 35
 36config HAVE_OPROFILE
 37	bool
 38
 39config OPROFILE_NMI_TIMER
 40	def_bool y
 41	depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
 42
 43config KPROBES
 44	bool "Kprobes"
 45	depends on MODULES
 46	depends on HAVE_KPROBES
 47	select KALLSYMS
 48	help
 49	  Kprobes allows you to trap at almost any kernel address and
 50	  execute a callback function.  register_kprobe() establishes
 51	  a probepoint and specifies the callback.  Kprobes is useful
 52	  for kernel debugging, non-intrusive instrumentation and testing.
 53	  If in doubt, say "N".
 54
 55config JUMP_LABEL
 56       bool "Optimize very unlikely/likely branches"
 57       depends on HAVE_ARCH_JUMP_LABEL
 58       help
 59         This option enables a transparent branch optimization that
 60	 makes certain almost-always-true or almost-always-false branch
 61	 conditions even cheaper to execute within the kernel.
 62
 63	 Certain performance-sensitive kernel code, such as trace points,
 64	 scheduler functionality, networking code and KVM have such
 65	 branches and include support for this optimization technique.
 66
 67         If it is detected that the compiler has support for "asm goto",
 68	 the kernel will compile such branches with just a nop
 69	 instruction. When the condition flag is toggled to true, the
 70	 nop will be converted to a jump instruction to execute the
 71	 conditional block of instructions.
 72
 73	 This technique lowers overhead and stress on the branch prediction
 74	 of the processor and generally makes the kernel faster. The update
 75	 of the condition is slower, but those are always very rare.
 76
 77	 ( On 32-bit x86, the necessary options added to the compiler
 78	   flags may increase the size of the kernel slightly. )
 79
 80config STATIC_KEYS_SELFTEST
 81	bool "Static key selftest"
 82	depends on JUMP_LABEL
 83	help
 84	  Boot time self-test of the branch patching code.
 85
 86config OPTPROBES
 87	def_bool y
 88	depends on KPROBES && HAVE_OPTPROBES
 89	depends on !PREEMPT
 90
 91config KPROBES_ON_FTRACE
 92	def_bool y
 93	depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 94	depends on DYNAMIC_FTRACE_WITH_REGS
 95	help
 96	 If function tracer is enabled and the arch supports full
 97	 passing of pt_regs to function tracing, then kprobes can
 98	 optimize on top of function tracing.
 99
100config UPROBES
101	def_bool n
102	depends on ARCH_SUPPORTS_UPROBES
103	help
104	  Uprobes is the user-space counterpart to kprobes: they
105	  enable instrumentation applications (such as 'perf probe')
106	  to establish unintrusive probes in user-space binaries and
107	  libraries, by executing handler functions when the probes
108	  are hit by user-space applications.
109
110	  ( These probes come in the form of single-byte breakpoints,
111	    managed by the kernel and kept transparent to the probed
112	    application. )
113
114config HAVE_64BIT_ALIGNED_ACCESS
115	def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
116	help
117	  Some architectures require 64 bit accesses to be 64 bit
118	  aligned, which also requires structs containing 64 bit values
119	  to be 64 bit aligned too. This includes some 32 bit
120	  architectures which can do 64 bit accesses, as well as 64 bit
121	  architectures without unaligned access.
122
123	  This symbol should be selected by an architecture if 64 bit
124	  accesses are required to be 64 bit aligned in this way even
125	  though it is not a 64 bit architecture.
126
127	  See Documentation/unaligned-memory-access.txt for more
128	  information on the topic of unaligned memory accesses.
129
130config HAVE_EFFICIENT_UNALIGNED_ACCESS
131	bool
132	help
133	  Some architectures are unable to perform unaligned accesses
134	  without the use of get_unaligned/put_unaligned. Others are
135	  unable to perform such accesses efficiently (e.g. trap on
136	  unaligned access and require fixing it up in the exception
137	  handler.)
138
139	  This symbol should be selected by an architecture if it can
140	  perform unaligned accesses efficiently to allow different
141	  code paths to be selected for these cases. Some network
142	  drivers, for example, could opt to not fix up alignment
143	  problems with received packets if doing so would not help
144	  much.
145
146	  See Documentation/unaligned-memory-access.txt for more
147	  information on the topic of unaligned memory accesses.
148
149config ARCH_USE_BUILTIN_BSWAP
150       bool
151       help
152	 Modern versions of GCC (since 4.4) have builtin functions
153	 for handling byte-swapping. Using these, instead of the old
154	 inline assembler that the architecture code provides in the
155	 __arch_bswapXX() macros, allows the compiler to see what's
156	 happening and offers more opportunity for optimisation. In
157	 particular, the compiler will be able to combine the byteswap
158	 with a nearby load or store and use load-and-swap or
159	 store-and-swap instructions if the architecture has them. It
160	 should almost *never* result in code which is worse than the
161	 hand-coded assembler in <asm/swab.h>.  But just in case it
162	 does, the use of the builtins is optional.
163
164	 Any architecture with load-and-swap or store-and-swap
165	 instructions should set this. And it shouldn't hurt to set it
166	 on architectures that don't have such instructions.
167
168config KRETPROBES
169	def_bool y
170	depends on KPROBES && HAVE_KRETPROBES
171
172config USER_RETURN_NOTIFIER
173	bool
174	depends on HAVE_USER_RETURN_NOTIFIER
175	help
176	  Provide a kernel-internal notification when a cpu is about to
177	  switch to user mode.
178
179config HAVE_IOREMAP_PROT
180	bool
181
182config HAVE_KPROBES
183	bool
184
185config HAVE_KRETPROBES
186	bool
187
188config HAVE_OPTPROBES
189	bool
190
191config HAVE_KPROBES_ON_FTRACE
192	bool
193
 
 
 
194config HAVE_NMI
195	bool
196
197config HAVE_NMI_WATCHDOG
198	depends on HAVE_NMI
199	bool
200#
201# An arch should select this if it provides all these things:
202#
203#	task_pt_regs()		in asm/processor.h or asm/ptrace.h
204#	arch_has_single_step()	if there is hardware single-step support
205#	arch_has_block_step()	if there is hardware block-step support
206#	asm/syscall.h		supplying asm-generic/syscall.h interface
207#	linux/regset.h		user_regset interfaces
208#	CORE_DUMP_USE_REGSET	#define'd in linux/elf.h
209#	TIF_SYSCALL_TRACE	calls tracehook_report_syscall_{entry,exit}
210#	TIF_NOTIFY_RESUME	calls tracehook_notify_resume()
211#	signal delivery		calls tracehook_signal_handler()
212#
213config HAVE_ARCH_TRACEHOOK
214	bool
215
216config HAVE_DMA_CONTIGUOUS
217	bool
218
219config GENERIC_SMP_IDLE_THREAD
220       bool
221
222config GENERIC_IDLE_POLL_SETUP
223       bool
224
225# Select if arch init_task initializer is different to init/init_task.c
226config ARCH_INIT_TASK
 
 
 
 
 
 
 
 
 
 
227       bool
228
229# Select if arch has its private alloc_task_struct() function
230config ARCH_TASK_STRUCT_ALLOCATOR
231	bool
232
 
 
 
 
 
 
 
 
 
 
 
233# Select if arch has its private alloc_thread_stack() function
234config ARCH_THREAD_STACK_ALLOCATOR
235	bool
236
237# Select if arch wants to size task_struct dynamically via arch_task_struct_size:
238config ARCH_WANTS_DYNAMIC_TASK_STRUCT
239	bool
240
241config HAVE_REGS_AND_STACK_ACCESS_API
242	bool
243	help
244	  This symbol should be selected by an architecure if it supports
245	  the API needed to access registers and stack entries from pt_regs,
246	  declared in asm/ptrace.h
247	  For example the kprobes-based event tracer needs this API.
248
249config HAVE_CLK
250	bool
251	help
252	  The <linux/clk.h> calls support software clock gating and
253	  thus are a key power management tool on many systems.
254
255config HAVE_DMA_API_DEBUG
256	bool
257
258config HAVE_HW_BREAKPOINT
259	bool
260	depends on PERF_EVENTS
261
262config HAVE_MIXED_BREAKPOINTS_REGS
263	bool
264	depends on HAVE_HW_BREAKPOINT
265	help
266	  Depending on the arch implementation of hardware breakpoints,
267	  some of them have separate registers for data and instruction
268	  breakpoints addresses, others have mixed registers to store
269	  them but define the access type in a control register.
270	  Select this option if your arch implements breakpoints under the
271	  latter fashion.
272
273config HAVE_USER_RETURN_NOTIFIER
274	bool
275
276config HAVE_PERF_EVENTS_NMI
277	bool
278	help
279	  System hardware can generate an NMI using the perf event
280	  subsystem.  Also has support for calculating CPU cycle events
281	  to determine how many clock cycles in a given period.
282
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
283config HAVE_PERF_REGS
284	bool
285	help
286	  Support selective register dumps for perf events. This includes
287	  bit-mapping of each registers and a unique architecture id.
288
289config HAVE_PERF_USER_STACK_DUMP
290	bool
291	help
292	  Support user stack dumps for perf event samples. This needs
293	  access to the user stack pointer which is not unified across
294	  architectures.
295
296config HAVE_ARCH_JUMP_LABEL
297	bool
298
299config HAVE_RCU_TABLE_FREE
300	bool
301
302config ARCH_HAVE_NMI_SAFE_CMPXCHG
303	bool
304
305config HAVE_ALIGNED_STRUCT_PAGE
306	bool
307	help
308	  This makes sure that struct pages are double word aligned and that
309	  e.g. the SLUB allocator can perform double word atomic operations
310	  on a struct page for better performance. However selecting this
311	  might increase the size of a struct page by a word.
312
313config HAVE_CMPXCHG_LOCAL
314	bool
315
316config HAVE_CMPXCHG_DOUBLE
317	bool
318
 
 
 
319config ARCH_WANT_IPC_PARSE_VERSION
320	bool
321
322config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
323	bool
324
325config ARCH_WANT_OLD_COMPAT_IPC
326	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
327	bool
328
329config HAVE_ARCH_SECCOMP_FILTER
330	bool
331	help
332	  An arch should select this symbol if it provides all of these things:
333	  - syscall_get_arch()
334	  - syscall_get_arguments()
335	  - syscall_rollback()
336	  - syscall_set_return_value()
337	  - SIGSYS siginfo_t support
338	  - secure_computing is called from a ptrace_event()-safe context
339	  - secure_computing return value is checked and a return value of -1
340	    results in the system call being skipped immediately.
341	  - seccomp syscall wired up
342
343config SECCOMP_FILTER
344	def_bool y
345	depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
346	help
347	  Enable tasks to build secure computing environments defined
348	  in terms of Berkeley Packet Filter programs which implement
349	  task-defined system call filtering polices.
350
351	  See Documentation/prctl/seccomp_filter.txt for details.
352
353config HAVE_GCC_PLUGINS
354	bool
355	help
356	  An arch should select this symbol if it supports building with
357	  GCC plugins.
358
359menuconfig GCC_PLUGINS
360	bool "GCC plugins"
361	depends on HAVE_GCC_PLUGINS
362	depends on !COMPILE_TEST
363	help
364	  GCC plugins are loadable modules that provide extra features to the
365	  compiler. They are useful for runtime instrumentation and static analysis.
366
367	  See Documentation/gcc-plugins.txt for details.
368
369config GCC_PLUGIN_CYC_COMPLEXITY
370	bool "Compute the cyclomatic complexity of a function" if EXPERT
371	depends on GCC_PLUGINS
372	depends on !COMPILE_TEST
373	help
374	  The complexity M of a function's control flow graph is defined as:
375	   M = E - N + 2P
376	  where
377
378	  E = the number of edges
379	  N = the number of nodes
380	  P = the number of connected components (exit nodes).
381
382	  Enabling this plugin reports the complexity to stderr during the
383	  build. It mainly serves as a simple example of how to create a
384	  gcc plugin for the kernel.
385
386config GCC_PLUGIN_SANCOV
387	bool
388	depends on GCC_PLUGINS
389	help
390	  This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
391	  basic blocks. It supports all gcc versions with plugin support (from
392	  gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
393	  by Dmitry Vyukov <dvyukov@google.com>.
394
395config GCC_PLUGIN_LATENT_ENTROPY
396	bool "Generate some entropy during boot and runtime"
397	depends on GCC_PLUGINS
398	help
399	  By saying Y here the kernel will instrument some kernel code to
400	  extract some entropy from both original and artificially created
401	  program state.  This will help especially embedded systems where
402	  there is little 'natural' source of entropy normally.  The cost
403	  is some slowdown of the boot process (about 0.5%) and fork and
404	  irq processing.
405
406	  Note that entropy extracted this way is not cryptographically
407	  secure!
408
409	  This plugin was ported from grsecurity/PaX. More information at:
410	   * https://grsecurity.net/
411	   * https://pax.grsecurity.net/
412
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
413config HAVE_CC_STACKPROTECTOR
414	bool
415	help
416	  An arch should select this symbol if:
417	  - its compiler supports the -fstack-protector option
418	  - it has implemented a stack canary (e.g. __stack_chk_guard)
419
420config CC_STACKPROTECTOR
421	def_bool n
422	help
423	  Set when a stack-protector mode is enabled, so that the build
424	  can enable kernel-side support for the GCC feature.
425
426choice
427	prompt "Stack Protector buffer overflow detection"
428	depends on HAVE_CC_STACKPROTECTOR
429	default CC_STACKPROTECTOR_NONE
430	help
431	  This option turns on the "stack-protector" GCC feature. This
432	  feature puts, at the beginning of functions, a canary value on
433	  the stack just before the return address, and validates
434	  the value just before actually returning.  Stack based buffer
435	  overflows (that need to overwrite this return address) now also
436	  overwrite the canary, which gets detected and the attack is then
437	  neutralized via a kernel panic.
438
439config CC_STACKPROTECTOR_NONE
440	bool "None"
441	help
442	  Disable "stack-protector" GCC feature.
443
444config CC_STACKPROTECTOR_REGULAR
445	bool "Regular"
446	select CC_STACKPROTECTOR
447	help
448	  Functions will have the stack-protector canary logic added if they
449	  have an 8-byte or larger character array on the stack.
450
451	  This feature requires gcc version 4.2 or above, or a distribution
452	  gcc with the feature backported ("-fstack-protector").
453
454	  On an x86 "defconfig" build, this feature adds canary checks to
455	  about 3% of all kernel functions, which increases kernel code size
456	  by about 0.3%.
457
458config CC_STACKPROTECTOR_STRONG
459	bool "Strong"
460	select CC_STACKPROTECTOR
461	help
462	  Functions will have the stack-protector canary logic added in any
463	  of the following conditions:
464
465	  - local variable's address used as part of the right hand side of an
466	    assignment or function argument
467	  - local variable is an array (or union containing an array),
468	    regardless of array type or length
469	  - uses register local variables
470
471	  This feature requires gcc version 4.9 or above, or a distribution
472	  gcc with the feature backported ("-fstack-protector-strong").
473
474	  On an x86 "defconfig" build, this feature adds canary checks to
475	  about 20% of all kernel functions, which increases the kernel code
476	  size by about 2%.
477
 
 
 
 
 
 
478endchoice
479
480config THIN_ARCHIVES
481	bool
482	help
483	  Select this if the architecture wants to use thin archives
484	  instead of ld -r to create the built-in.o files.
485
486config LD_DEAD_CODE_DATA_ELIMINATION
487	bool
488	help
489	  Select this if the architecture wants to do dead code and
490	  data elimination with the linker by compiling with
491	  -ffunction-sections -fdata-sections and linking with
492	  --gc-sections.
493
494	  This requires that the arch annotates or otherwise protects
495	  its external entry points from being discarded. Linker scripts
496	  must also merge .text.*, .data.*, and .bss.* correctly into
497	  output sections. Care must be taken not to pull in unrelated
498	  sections (e.g., '.text.init'). Typically '.' in section names
499	  is used to distinguish them from label names / C identifiers.
500
501config HAVE_ARCH_WITHIN_STACK_FRAMES
502	bool
503	help
504	  An architecture should select this if it can walk the kernel stack
505	  frames to determine if an object is part of either the arguments
506	  or local variables (i.e. that it excludes saved return addresses,
507	  and similar) by implementing an inline arch_within_stack_frames(),
508	  which is used by CONFIG_HARDENED_USERCOPY.
509
510config HAVE_CONTEXT_TRACKING
511	bool
512	help
513	  Provide kernel/user boundaries probes necessary for subsystems
514	  that need it, such as userspace RCU extended quiescent state.
515	  Syscalls need to be wrapped inside user_exit()-user_enter() through
516	  the slow path using TIF_NOHZ flag. Exceptions handlers must be
517	  wrapped as well. Irqs are already protected inside
518	  rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
519	  irq exit still need to be protected.
520
521config HAVE_VIRT_CPU_ACCOUNTING
522	bool
523
524config ARCH_HAS_SCALED_CPUTIME
525	bool
526
527config HAVE_VIRT_CPU_ACCOUNTING_GEN
528	bool
529	default y if 64BIT
530	help
531	  With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
532	  Before enabling this option, arch code must be audited
533	  to ensure there are no races in concurrent read/write of
534	  cputime_t. For example, reading/writing 64-bit cputime_t on
535	  some 32-bit arches may require multiple accesses, so proper
536	  locking is needed to protect against concurrent accesses.
537
538
539config HAVE_IRQ_TIME_ACCOUNTING
540	bool
541	help
542	  Archs need to ensure they use a high enough resolution clock to
543	  support irq time accounting and then call enable_sched_clock_irqtime().
544
545config HAVE_ARCH_TRANSPARENT_HUGEPAGE
546	bool
547
 
 
 
548config HAVE_ARCH_HUGE_VMAP
549	bool
550
551config HAVE_ARCH_SOFT_DIRTY
552	bool
553
554config HAVE_MOD_ARCH_SPECIFIC
555	bool
556	help
557	  The arch uses struct mod_arch_specific to store data.  Many arches
558	  just need a simple module loader without arch specific data - those
559	  should not enable this.
560
561config MODULES_USE_ELF_RELA
562	bool
563	help
564	  Modules only use ELF RELA relocations.  Modules with ELF REL
565	  relocations will give an error.
566
567config MODULES_USE_ELF_REL
568	bool
569	help
570	  Modules only use ELF REL relocations.  Modules with ELF RELA
571	  relocations will give an error.
572
573config HAVE_UNDERSCORE_SYMBOL_PREFIX
574	bool
575	help
576	  Some architectures generate an _ in front of C symbols; things like
577	  module loading and assembly files need to know about this.
578
579config HAVE_IRQ_EXIT_ON_IRQ_STACK
580	bool
581	help
582	  Architecture doesn't only execute the irq handler on the irq stack
583	  but also irq_exit(). This way we can process softirqs on this irq
584	  stack instead of switching to a new one when we call __do_softirq()
585	  in the end of an hardirq.
586	  This spares a stack switch and improves cache usage on softirq
587	  processing.
588
589config PGTABLE_LEVELS
590	int
591	default 2
592
593config ARCH_HAS_ELF_RANDOMIZE
594	bool
595	help
596	  An architecture supports choosing randomized locations for
597	  stack, mmap, brk, and ET_DYN. Defined functions:
598	  - arch_mmap_rnd()
599	  - arch_randomize_brk()
600
601config HAVE_ARCH_MMAP_RND_BITS
602	bool
603	help
604	  An arch should select this symbol if it supports setting a variable
605	  number of bits for use in establishing the base address for mmap
606	  allocations, has MMU enabled and provides values for both:
607	  - ARCH_MMAP_RND_BITS_MIN
608	  - ARCH_MMAP_RND_BITS_MAX
609
610config HAVE_EXIT_THREAD
611	bool
612	help
613	  An architecture implements exit_thread.
614
615config ARCH_MMAP_RND_BITS_MIN
616	int
617
618config ARCH_MMAP_RND_BITS_MAX
619	int
620
621config ARCH_MMAP_RND_BITS_DEFAULT
622	int
623
624config ARCH_MMAP_RND_BITS
625	int "Number of bits to use for ASLR of mmap base address" if EXPERT
626	range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
627	default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
628	default ARCH_MMAP_RND_BITS_MIN
629	depends on HAVE_ARCH_MMAP_RND_BITS
630	help
631	  This value can be used to select the number of bits to use to
632	  determine the random offset to the base address of vma regions
633	  resulting from mmap allocations. This value will be bounded
634	  by the architecture's minimum and maximum supported values.
635
636	  This value can be changed after boot using the
637	  /proc/sys/vm/mmap_rnd_bits tunable
638
639config HAVE_ARCH_MMAP_RND_COMPAT_BITS
640	bool
641	help
642	  An arch should select this symbol if it supports running applications
643	  in compatibility mode, supports setting a variable number of bits for
644	  use in establishing the base address for mmap allocations, has MMU
645	  enabled and provides values for both:
646	  - ARCH_MMAP_RND_COMPAT_BITS_MIN
647	  - ARCH_MMAP_RND_COMPAT_BITS_MAX
648
649config ARCH_MMAP_RND_COMPAT_BITS_MIN
650	int
651
652config ARCH_MMAP_RND_COMPAT_BITS_MAX
653	int
654
655config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
656	int
657
658config ARCH_MMAP_RND_COMPAT_BITS
659	int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
660	range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
661	default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
662	default ARCH_MMAP_RND_COMPAT_BITS_MIN
663	depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
664	help
665	  This value can be used to select the number of bits to use to
666	  determine the random offset to the base address of vma regions
667	  resulting from mmap allocations for compatible applications This
668	  value will be bounded by the architecture's minimum and maximum
669	  supported values.
670
671	  This value can be changed after boot using the
672	  /proc/sys/vm/mmap_rnd_compat_bits tunable
673
 
 
 
 
 
 
 
674config HAVE_COPY_THREAD_TLS
675	bool
676	help
677	  Architecture provides copy_thread_tls to accept tls argument via
678	  normal C parameter passing, rather than extracting the syscall
679	  argument from pt_regs.
680
681config HAVE_STACK_VALIDATION
682	bool
683	help
684	  Architecture supports the 'objtool check' host tool command, which
685	  performs compile-time stack metadata validation.
686
 
 
 
 
 
 
687config HAVE_ARCH_HASH
688	bool
689	default n
690	help
691	  If this is set, the architecture provides an <asm/hash.h>
692	  file which provides platform-specific implementations of some
693	  functions in <linux/hash.h> or fs/namei.c.
694
695config ISA_BUS_API
696	def_bool ISA
697
698#
699# ABI hall of shame
700#
701config CLONE_BACKWARDS
702	bool
703	help
704	  Architecture has tls passed as the 4th argument of clone(2),
705	  not the 5th one.
706
707config CLONE_BACKWARDS2
708	bool
709	help
710	  Architecture has the first two arguments of clone(2) swapped.
711
712config CLONE_BACKWARDS3
713	bool
714	help
715	  Architecture has tls passed as the 3rd argument of clone(2),
716	  not the 5th one.
717
718config ODD_RT_SIGACTION
719	bool
720	help
721	  Architecture has unusual rt_sigaction(2) arguments
722
723config OLD_SIGSUSPEND
724	bool
725	help
726	  Architecture has old sigsuspend(2) syscall, of one-argument variety
727
728config OLD_SIGSUSPEND3
729	bool
730	help
731	  Even weirder antique ABI - three-argument sigsuspend(2)
732
733config OLD_SIGACTION
734	bool
735	help
736	  Architecture has old sigaction(2) syscall.  Nope, not the same
737	  as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
738	  but fairly different variant of sigaction(2), thanks to OSF/1
739	  compatibility...
740
741config COMPAT_OLD_SIGACTION
742	bool
743
744config ARCH_NO_COHERENT_DMA_MMAP
745	bool
746
747config CPU_NO_EFFICIENT_FFS
748	def_bool n
749
750config HAVE_ARCH_VMAP_STACK
751	def_bool n
752	help
753	  An arch should select this symbol if it can support kernel stacks
754	  in vmalloc space.  This means:
755
756	  - vmalloc space must be large enough to hold many kernel stacks.
757	    This may rule out many 32-bit architectures.
758
759	  - Stacks in vmalloc space need to work reliably.  For example, if
760	    vmap page tables are created on demand, either this mechanism
761	    needs to work while the stack points to a virtual address with
762	    unpopulated page tables or arch code (switch_to() and switch_mm(),
763	    most likely) needs to ensure that the stack's page table entries
764	    are populated before running on a possibly unpopulated stack.
765
766	  - If the stack overflows into a guard page, something reasonable
767	    should happen.  The definition of "reasonable" is flexible, but
768	    instantly rebooting without logging anything would be unfriendly.
769
770config VMAP_STACK
771	default y
772	bool "Use a virtually-mapped stack"
773	depends on HAVE_ARCH_VMAP_STACK && !KASAN
774	---help---
775	  Enable this if you want the use virtually-mapped kernel stacks
776	  with guard pages.  This causes kernel stack overflows to be
777	  caught immediately rather than causing difficult-to-diagnose
778	  corruption.
779
780	  This is presently incompatible with KASAN because KASAN expects
781	  the stack to map directly to the KASAN shadow map using a formula
782	  that is incorrect if the stack is in vmalloc space.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
783
784source "kernel/gcov/Kconfig"