1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6# 7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8# override the default values in this file. 9# 10source "arch/$(SRCARCH)/Kconfig" 11 12menu "General architecture-dependent options" 13 14config CRASH_CORE 15 bool 16 17config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21config HAVE_IMA_KEXEC 22 bool 23 24config HOTPLUG_SMT 25 bool 26 27config OPROFILE 28 tristate "OProfile system profiling" 29 depends on PROFILING 30 depends on HAVE_OPROFILE 31 select RING_BUFFER 32 select RING_BUFFER_ALLOW_SWAP 33 help 34 OProfile is a profiling system capable of profiling the 35 whole system, include the kernel, kernel modules, libraries, 36 and applications. 37 38 If unsure, say N. 39 40config OPROFILE_EVENT_MULTIPLEX 41 bool "OProfile multiplexing support (EXPERIMENTAL)" 42 default n 43 depends on OPROFILE && X86 44 help 45 The number of hardware counters is limited. The multiplexing 46 feature enables OProfile to gather more events than counters 47 are provided by the hardware. This is realized by switching 48 between events at a user specified time interval. 49 50 If unsure, say N. 51 52config HAVE_OPROFILE 53 bool 54 55config OPROFILE_NMI_TIMER 56 def_bool y 57 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 58 59config KPROBES 60 bool "Kprobes" 61 depends on MODULES 62 depends on HAVE_KPROBES 63 select KALLSYMS 64 help 65 Kprobes allows you to trap at almost any kernel address and 66 execute a callback function. register_kprobe() establishes 67 a probepoint and specifies the callback. Kprobes is useful 68 for kernel debugging, non-intrusive instrumentation and testing. 69 If in doubt, say "N". 70 71config JUMP_LABEL 72 bool "Optimize very unlikely/likely branches" 73 depends on HAVE_ARCH_JUMP_LABEL 74 depends on CC_HAS_ASM_GOTO 75 help 76 This option enables a transparent branch optimization that 77 makes certain almost-always-true or almost-always-false branch 78 conditions even cheaper to execute within the kernel. 79 80 Certain performance-sensitive kernel code, such as trace points, 81 scheduler functionality, networking code and KVM have such 82 branches and include support for this optimization technique. 83 84 If it is detected that the compiler has support for "asm goto", 85 the kernel will compile such branches with just a nop 86 instruction. When the condition flag is toggled to true, the 87 nop will be converted to a jump instruction to execute the 88 conditional block of instructions. 89 90 This technique lowers overhead and stress on the branch prediction 91 of the processor and generally makes the kernel faster. The update 92 of the condition is slower, but those are always very rare. 93 94 ( On 32-bit x86, the necessary options added to the compiler 95 flags may increase the size of the kernel slightly. ) 96 97config STATIC_KEYS_SELFTEST 98 bool "Static key selftest" 99 depends on JUMP_LABEL 100 help 101 Boot time self-test of the branch patching code. 102 103config OPTPROBES 104 def_bool y 105 depends on KPROBES && HAVE_OPTPROBES 106 select TASKS_RCU if PREEMPT 107 108config KPROBES_ON_FTRACE 109 def_bool y 110 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 111 depends on DYNAMIC_FTRACE_WITH_REGS 112 help 113 If function tracer is enabled and the arch supports full 114 passing of pt_regs to function tracing, then kprobes can 115 optimize on top of function tracing. 116 117config UPROBES 118 def_bool n 119 depends on ARCH_SUPPORTS_UPROBES 120 help 121 Uprobes is the user-space counterpart to kprobes: they 122 enable instrumentation applications (such as 'perf probe') 123 to establish unintrusive probes in user-space binaries and 124 libraries, by executing handler functions when the probes 125 are hit by user-space applications. 126 127 ( These probes come in the form of single-byte breakpoints, 128 managed by the kernel and kept transparent to the probed 129 application. ) 130 131config HAVE_64BIT_ALIGNED_ACCESS 132 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 133 help 134 Some architectures require 64 bit accesses to be 64 bit 135 aligned, which also requires structs containing 64 bit values 136 to be 64 bit aligned too. This includes some 32 bit 137 architectures which can do 64 bit accesses, as well as 64 bit 138 architectures without unaligned access. 139 140 This symbol should be selected by an architecture if 64 bit 141 accesses are required to be 64 bit aligned in this way even 142 though it is not a 64 bit architecture. 143 144 See Documentation/unaligned-memory-access.txt for more 145 information on the topic of unaligned memory accesses. 146 147config HAVE_EFFICIENT_UNALIGNED_ACCESS 148 bool 149 help 150 Some architectures are unable to perform unaligned accesses 151 without the use of get_unaligned/put_unaligned. Others are 152 unable to perform such accesses efficiently (e.g. trap on 153 unaligned access and require fixing it up in the exception 154 handler.) 155 156 This symbol should be selected by an architecture if it can 157 perform unaligned accesses efficiently to allow different 158 code paths to be selected for these cases. Some network 159 drivers, for example, could opt to not fix up alignment 160 problems with received packets if doing so would not help 161 much. 162 163 See Documentation/unaligned-memory-access.txt for more 164 information on the topic of unaligned memory accesses. 165 166config ARCH_USE_BUILTIN_BSWAP 167 bool 168 help 169 Modern versions of GCC (since 4.4) have builtin functions 170 for handling byte-swapping. Using these, instead of the old 171 inline assembler that the architecture code provides in the 172 __arch_bswapXX() macros, allows the compiler to see what's 173 happening and offers more opportunity for optimisation. In 174 particular, the compiler will be able to combine the byteswap 175 with a nearby load or store and use load-and-swap or 176 store-and-swap instructions if the architecture has them. It 177 should almost *never* result in code which is worse than the 178 hand-coded assembler in <asm/swab.h>. But just in case it 179 does, the use of the builtins is optional. 180 181 Any architecture with load-and-swap or store-and-swap 182 instructions should set this. And it shouldn't hurt to set it 183 on architectures that don't have such instructions. 184 185config KRETPROBES 186 def_bool y 187 depends on KPROBES && HAVE_KRETPROBES 188 189config USER_RETURN_NOTIFIER 190 bool 191 depends on HAVE_USER_RETURN_NOTIFIER 192 help 193 Provide a kernel-internal notification when a cpu is about to 194 switch to user mode. 195 196config HAVE_IOREMAP_PROT 197 bool 198 199config HAVE_KPROBES 200 bool 201 202config HAVE_KRETPROBES 203 bool 204 205config HAVE_OPTPROBES 206 bool 207 208config HAVE_KPROBES_ON_FTRACE 209 bool 210 211config HAVE_FUNCTION_ERROR_INJECTION 212 bool 213 214config HAVE_NMI 215 bool 216 217# 218# An arch should select this if it provides all these things: 219# 220# task_pt_regs() in asm/processor.h or asm/ptrace.h 221# arch_has_single_step() if there is hardware single-step support 222# arch_has_block_step() if there is hardware block-step support 223# asm/syscall.h supplying asm-generic/syscall.h interface 224# linux/regset.h user_regset interfaces 225# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 226# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 227# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 228# signal delivery calls tracehook_signal_handler() 229# 230config HAVE_ARCH_TRACEHOOK 231 bool 232 233config HAVE_DMA_CONTIGUOUS 234 bool 235 236config GENERIC_SMP_IDLE_THREAD 237 bool 238 239config GENERIC_IDLE_POLL_SETUP 240 bool 241 242config ARCH_HAS_FORTIFY_SOURCE 243 bool 244 help 245 An architecture should select this when it can successfully 246 build and run with CONFIG_FORTIFY_SOURCE. 247 248# 249# Select if the arch provides a historic keepinit alias for the retain_initrd 250# command line option 251# 252config ARCH_HAS_KEEPINITRD 253 bool 254 255# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 256config ARCH_HAS_SET_MEMORY 257 bool 258 259# Select if arch has all set_direct_map_invalid/default() functions 260config ARCH_HAS_SET_DIRECT_MAP 261 bool 262 263# 264# Select if arch has an uncached kernel segment and provides the 265# uncached_kernel_address / cached_kernel_address symbols to use it 266# 267config ARCH_HAS_UNCACHED_SEGMENT 268 select ARCH_HAS_DMA_PREP_COHERENT 269 bool 270 271# Select if arch init_task must go in the __init_task_data section 272config ARCH_TASK_STRUCT_ON_STACK 273 bool 274 275# Select if arch has its private alloc_task_struct() function 276config ARCH_TASK_STRUCT_ALLOCATOR 277 bool 278 279config HAVE_ARCH_THREAD_STRUCT_WHITELIST 280 bool 281 depends on !ARCH_TASK_STRUCT_ALLOCATOR 282 help 283 An architecture should select this to provide hardened usercopy 284 knowledge about what region of the thread_struct should be 285 whitelisted for copying to userspace. Normally this is only the 286 FPU registers. Specifically, arch_thread_struct_whitelist() 287 should be implemented. Without this, the entire thread_struct 288 field in task_struct will be left whitelisted. 289 290# Select if arch has its private alloc_thread_stack() function 291config ARCH_THREAD_STACK_ALLOCATOR 292 bool 293 294# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 295config ARCH_WANTS_DYNAMIC_TASK_STRUCT 296 bool 297 298config ARCH_32BIT_OFF_T 299 bool 300 depends on !64BIT 301 help 302 All new 32-bit architectures should have 64-bit off_t type on 303 userspace side which corresponds to the loff_t kernel type. This 304 is the requirement for modern ABIs. Some existing architectures 305 still support 32-bit off_t. This option is enabled for all such 306 architectures explicitly. 307 308config HAVE_REGS_AND_STACK_ACCESS_API 309 bool 310 help 311 This symbol should be selected by an architecure if it supports 312 the API needed to access registers and stack entries from pt_regs, 313 declared in asm/ptrace.h 314 For example the kprobes-based event tracer needs this API. 315 316config HAVE_RSEQ 317 bool 318 depends on HAVE_REGS_AND_STACK_ACCESS_API 319 help 320 This symbol should be selected by an architecture if it 321 supports an implementation of restartable sequences. 322 323config HAVE_FUNCTION_ARG_ACCESS_API 324 bool 325 help 326 This symbol should be selected by an architecure if it supports 327 the API needed to access function arguments from pt_regs, 328 declared in asm/ptrace.h 329 330config HAVE_CLK 331 bool 332 help 333 The <linux/clk.h> calls support software clock gating and 334 thus are a key power management tool on many systems. 335 336config HAVE_HW_BREAKPOINT 337 bool 338 depends on PERF_EVENTS 339 340config HAVE_MIXED_BREAKPOINTS_REGS 341 bool 342 depends on HAVE_HW_BREAKPOINT 343 help 344 Depending on the arch implementation of hardware breakpoints, 345 some of them have separate registers for data and instruction 346 breakpoints addresses, others have mixed registers to store 347 them but define the access type in a control register. 348 Select this option if your arch implements breakpoints under the 349 latter fashion. 350 351config HAVE_USER_RETURN_NOTIFIER 352 bool 353 354config HAVE_PERF_EVENTS_NMI 355 bool 356 help 357 System hardware can generate an NMI using the perf event 358 subsystem. Also has support for calculating CPU cycle events 359 to determine how many clock cycles in a given period. 360 361config HAVE_HARDLOCKUP_DETECTOR_PERF 362 bool 363 depends on HAVE_PERF_EVENTS_NMI 364 help 365 The arch chooses to use the generic perf-NMI-based hardlockup 366 detector. Must define HAVE_PERF_EVENTS_NMI. 367 368config HAVE_NMI_WATCHDOG 369 depends on HAVE_NMI 370 bool 371 help 372 The arch provides a low level NMI watchdog. It provides 373 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 374 375config HAVE_HARDLOCKUP_DETECTOR_ARCH 376 bool 377 select HAVE_NMI_WATCHDOG 378 help 379 The arch chooses to provide its own hardlockup detector, which is 380 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 381 interfaces and parameters provided by hardlockup detector subsystem. 382 383config HAVE_PERF_REGS 384 bool 385 help 386 Support selective register dumps for perf events. This includes 387 bit-mapping of each registers and a unique architecture id. 388 389config HAVE_PERF_USER_STACK_DUMP 390 bool 391 help 392 Support user stack dumps for perf event samples. This needs 393 access to the user stack pointer which is not unified across 394 architectures. 395 396config HAVE_ARCH_JUMP_LABEL 397 bool 398 399config HAVE_ARCH_JUMP_LABEL_RELATIVE 400 bool 401 402config HAVE_RCU_TABLE_FREE 403 bool 404 405config HAVE_RCU_TABLE_NO_INVALIDATE 406 bool 407 408config HAVE_MMU_GATHER_PAGE_SIZE 409 bool 410 411config HAVE_MMU_GATHER_NO_GATHER 412 bool 413 414config ARCH_HAVE_NMI_SAFE_CMPXCHG 415 bool 416 417config HAVE_ALIGNED_STRUCT_PAGE 418 bool 419 help 420 This makes sure that struct pages are double word aligned and that 421 e.g. the SLUB allocator can perform double word atomic operations 422 on a struct page for better performance. However selecting this 423 might increase the size of a struct page by a word. 424 425config HAVE_CMPXCHG_LOCAL 426 bool 427 428config HAVE_CMPXCHG_DOUBLE 429 bool 430 431config ARCH_WEAK_RELEASE_ACQUIRE 432 bool 433 434config ARCH_WANT_IPC_PARSE_VERSION 435 bool 436 437config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 438 bool 439 440config ARCH_WANT_OLD_COMPAT_IPC 441 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 442 bool 443 444config HAVE_ARCH_SECCOMP_FILTER 445 bool 446 help 447 An arch should select this symbol if it provides all of these things: 448 - syscall_get_arch() 449 - syscall_get_arguments() 450 - syscall_rollback() 451 - syscall_set_return_value() 452 - SIGSYS siginfo_t support 453 - secure_computing is called from a ptrace_event()-safe context 454 - secure_computing return value is checked and a return value of -1 455 results in the system call being skipped immediately. 456 - seccomp syscall wired up 457 458config SECCOMP_FILTER 459 def_bool y 460 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 461 help 462 Enable tasks to build secure computing environments defined 463 in terms of Berkeley Packet Filter programs which implement 464 task-defined system call filtering polices. 465 466 See Documentation/userspace-api/seccomp_filter.rst for details. 467 468config HAVE_ARCH_STACKLEAK 469 bool 470 help 471 An architecture should select this if it has the code which 472 fills the used part of the kernel stack with the STACKLEAK_POISON 473 value before returning from system calls. 474 475config HAVE_STACKPROTECTOR 476 bool 477 help 478 An arch should select this symbol if: 479 - it has implemented a stack canary (e.g. __stack_chk_guard) 480 481config CC_HAS_STACKPROTECTOR_NONE 482 def_bool $(cc-option,-fno-stack-protector) 483 484config STACKPROTECTOR 485 bool "Stack Protector buffer overflow detection" 486 depends on HAVE_STACKPROTECTOR 487 depends on $(cc-option,-fstack-protector) 488 default y 489 help 490 This option turns on the "stack-protector" GCC feature. This 491 feature puts, at the beginning of functions, a canary value on 492 the stack just before the return address, and validates 493 the value just before actually returning. Stack based buffer 494 overflows (that need to overwrite this return address) now also 495 overwrite the canary, which gets detected and the attack is then 496 neutralized via a kernel panic. 497 498 Functions will have the stack-protector canary logic added if they 499 have an 8-byte or larger character array on the stack. 500 501 This feature requires gcc version 4.2 or above, or a distribution 502 gcc with the feature backported ("-fstack-protector"). 503 504 On an x86 "defconfig" build, this feature adds canary checks to 505 about 3% of all kernel functions, which increases kernel code size 506 by about 0.3%. 507 508config STACKPROTECTOR_STRONG 509 bool "Strong Stack Protector" 510 depends on STACKPROTECTOR 511 depends on $(cc-option,-fstack-protector-strong) 512 default y 513 help 514 Functions will have the stack-protector canary logic added in any 515 of the following conditions: 516 517 - local variable's address used as part of the right hand side of an 518 assignment or function argument 519 - local variable is an array (or union containing an array), 520 regardless of array type or length 521 - uses register local variables 522 523 This feature requires gcc version 4.9 or above, or a distribution 524 gcc with the feature backported ("-fstack-protector-strong"). 525 526 On an x86 "defconfig" build, this feature adds canary checks to 527 about 20% of all kernel functions, which increases the kernel code 528 size by about 2%. 529 530config HAVE_ARCH_WITHIN_STACK_FRAMES 531 bool 532 help 533 An architecture should select this if it can walk the kernel stack 534 frames to determine if an object is part of either the arguments 535 or local variables (i.e. that it excludes saved return addresses, 536 and similar) by implementing an inline arch_within_stack_frames(), 537 which is used by CONFIG_HARDENED_USERCOPY. 538 539config HAVE_CONTEXT_TRACKING 540 bool 541 help 542 Provide kernel/user boundaries probes necessary for subsystems 543 that need it, such as userspace RCU extended quiescent state. 544 Syscalls need to be wrapped inside user_exit()-user_enter() through 545 the slow path using TIF_NOHZ flag. Exceptions handlers must be 546 wrapped as well. Irqs are already protected inside 547 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 548 irq exit still need to be protected. 549 550config HAVE_VIRT_CPU_ACCOUNTING 551 bool 552 553config ARCH_HAS_SCALED_CPUTIME 554 bool 555 556config HAVE_VIRT_CPU_ACCOUNTING_GEN 557 bool 558 default y if 64BIT 559 help 560 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 561 Before enabling this option, arch code must be audited 562 to ensure there are no races in concurrent read/write of 563 cputime_t. For example, reading/writing 64-bit cputime_t on 564 some 32-bit arches may require multiple accesses, so proper 565 locking is needed to protect against concurrent accesses. 566 567 568config HAVE_IRQ_TIME_ACCOUNTING 569 bool 570 help 571 Archs need to ensure they use a high enough resolution clock to 572 support irq time accounting and then call enable_sched_clock_irqtime(). 573 574config HAVE_MOVE_PMD 575 bool 576 help 577 Archs that select this are able to move page tables at the PMD level. 578 579config HAVE_ARCH_TRANSPARENT_HUGEPAGE 580 bool 581 582config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 583 bool 584 585config HAVE_ARCH_HUGE_VMAP 586 bool 587 588config HAVE_ARCH_SOFT_DIRTY 589 bool 590 591config HAVE_MOD_ARCH_SPECIFIC 592 bool 593 help 594 The arch uses struct mod_arch_specific to store data. Many arches 595 just need a simple module loader without arch specific data - those 596 should not enable this. 597 598config MODULES_USE_ELF_RELA 599 bool 600 help 601 Modules only use ELF RELA relocations. Modules with ELF REL 602 relocations will give an error. 603 604config MODULES_USE_ELF_REL 605 bool 606 help 607 Modules only use ELF REL relocations. Modules with ELF RELA 608 relocations will give an error. 609 610config HAVE_IRQ_EXIT_ON_IRQ_STACK 611 bool 612 help 613 Architecture doesn't only execute the irq handler on the irq stack 614 but also irq_exit(). This way we can process softirqs on this irq 615 stack instead of switching to a new one when we call __do_softirq() 616 in the end of an hardirq. 617 This spares a stack switch and improves cache usage on softirq 618 processing. 619 620config PGTABLE_LEVELS 621 int 622 default 2 623 624config ARCH_HAS_ELF_RANDOMIZE 625 bool 626 help 627 An architecture supports choosing randomized locations for 628 stack, mmap, brk, and ET_DYN. Defined functions: 629 - arch_mmap_rnd() 630 - arch_randomize_brk() 631 632config HAVE_ARCH_MMAP_RND_BITS 633 bool 634 help 635 An arch should select this symbol if it supports setting a variable 636 number of bits for use in establishing the base address for mmap 637 allocations, has MMU enabled and provides values for both: 638 - ARCH_MMAP_RND_BITS_MIN 639 - ARCH_MMAP_RND_BITS_MAX 640 641config HAVE_EXIT_THREAD 642 bool 643 help 644 An architecture implements exit_thread. 645 646config ARCH_MMAP_RND_BITS_MIN 647 int 648 649config ARCH_MMAP_RND_BITS_MAX 650 int 651 652config ARCH_MMAP_RND_BITS_DEFAULT 653 int 654 655config ARCH_MMAP_RND_BITS 656 int "Number of bits to use for ASLR of mmap base address" if EXPERT 657 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 658 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 659 default ARCH_MMAP_RND_BITS_MIN 660 depends on HAVE_ARCH_MMAP_RND_BITS 661 help 662 This value can be used to select the number of bits to use to 663 determine the random offset to the base address of vma regions 664 resulting from mmap allocations. This value will be bounded 665 by the architecture's minimum and maximum supported values. 666 667 This value can be changed after boot using the 668 /proc/sys/vm/mmap_rnd_bits tunable 669 670config HAVE_ARCH_MMAP_RND_COMPAT_BITS 671 bool 672 help 673 An arch should select this symbol if it supports running applications 674 in compatibility mode, supports setting a variable number of bits for 675 use in establishing the base address for mmap allocations, has MMU 676 enabled and provides values for both: 677 - ARCH_MMAP_RND_COMPAT_BITS_MIN 678 - ARCH_MMAP_RND_COMPAT_BITS_MAX 679 680config ARCH_MMAP_RND_COMPAT_BITS_MIN 681 int 682 683config ARCH_MMAP_RND_COMPAT_BITS_MAX 684 int 685 686config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 687 int 688 689config ARCH_MMAP_RND_COMPAT_BITS 690 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 691 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 692 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 693 default ARCH_MMAP_RND_COMPAT_BITS_MIN 694 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 695 help 696 This value can be used to select the number of bits to use to 697 determine the random offset to the base address of vma regions 698 resulting from mmap allocations for compatible applications This 699 value will be bounded by the architecture's minimum and maximum 700 supported values. 701 702 This value can be changed after boot using the 703 /proc/sys/vm/mmap_rnd_compat_bits tunable 704 705config HAVE_ARCH_COMPAT_MMAP_BASES 706 bool 707 help 708 This allows 64bit applications to invoke 32-bit mmap() syscall 709 and vice-versa 32-bit applications to call 64-bit mmap(). 710 Required for applications doing different bitness syscalls. 711 712config HAVE_COPY_THREAD_TLS 713 bool 714 help 715 Architecture provides copy_thread_tls to accept tls argument via 716 normal C parameter passing, rather than extracting the syscall 717 argument from pt_regs. 718 719config HAVE_STACK_VALIDATION 720 bool 721 help 722 Architecture supports the 'objtool check' host tool command, which 723 performs compile-time stack metadata validation. 724 725config HAVE_RELIABLE_STACKTRACE 726 bool 727 help 728 Architecture has a save_stack_trace_tsk_reliable() function which 729 only returns a stack trace if it can guarantee the trace is reliable. 730 731config HAVE_ARCH_HASH 732 bool 733 default n 734 help 735 If this is set, the architecture provides an <asm/hash.h> 736 file which provides platform-specific implementations of some 737 functions in <linux/hash.h> or fs/namei.c. 738 739config HAVE_ARCH_NVRAM_OPS 740 bool 741 742config ISA_BUS_API 743 def_bool ISA 744 745# 746# ABI hall of shame 747# 748config CLONE_BACKWARDS 749 bool 750 help 751 Architecture has tls passed as the 4th argument of clone(2), 752 not the 5th one. 753 754config CLONE_BACKWARDS2 755 bool 756 help 757 Architecture has the first two arguments of clone(2) swapped. 758 759config CLONE_BACKWARDS3 760 bool 761 help 762 Architecture has tls passed as the 3rd argument of clone(2), 763 not the 5th one. 764 765config ODD_RT_SIGACTION 766 bool 767 help 768 Architecture has unusual rt_sigaction(2) arguments 769 770config OLD_SIGSUSPEND 771 bool 772 help 773 Architecture has old sigsuspend(2) syscall, of one-argument variety 774 775config OLD_SIGSUSPEND3 776 bool 777 help 778 Even weirder antique ABI - three-argument sigsuspend(2) 779 780config OLD_SIGACTION 781 bool 782 help 783 Architecture has old sigaction(2) syscall. Nope, not the same 784 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 785 but fairly different variant of sigaction(2), thanks to OSF/1 786 compatibility... 787 788config COMPAT_OLD_SIGACTION 789 bool 790 791config 64BIT_TIME 792 def_bool y 793 help 794 This should be selected by all architectures that need to support 795 new system calls with a 64-bit time_t. This is relevant on all 32-bit 796 architectures, and 64-bit architectures as part of compat syscall 797 handling. 798 799config COMPAT_32BIT_TIME 800 def_bool !64BIT || COMPAT 801 help 802 This enables 32 bit time_t support in addition to 64 bit time_t support. 803 This is relevant on all 32-bit architectures, and 64-bit architectures 804 as part of compat syscall handling. 805 806config ARCH_NO_COHERENT_DMA_MMAP 807 bool 808 809config ARCH_NO_PREEMPT 810 bool 811 812config CPU_NO_EFFICIENT_FFS 813 def_bool n 814 815config HAVE_ARCH_VMAP_STACK 816 def_bool n 817 help 818 An arch should select this symbol if it can support kernel stacks 819 in vmalloc space. This means: 820 821 - vmalloc space must be large enough to hold many kernel stacks. 822 This may rule out many 32-bit architectures. 823 824 - Stacks in vmalloc space need to work reliably. For example, if 825 vmap page tables are created on demand, either this mechanism 826 needs to work while the stack points to a virtual address with 827 unpopulated page tables or arch code (switch_to() and switch_mm(), 828 most likely) needs to ensure that the stack's page table entries 829 are populated before running on a possibly unpopulated stack. 830 831 - If the stack overflows into a guard page, something reasonable 832 should happen. The definition of "reasonable" is flexible, but 833 instantly rebooting without logging anything would be unfriendly. 834 835config VMAP_STACK 836 default y 837 bool "Use a virtually-mapped stack" 838 depends on HAVE_ARCH_VMAP_STACK && !KASAN 839 ---help--- 840 Enable this if you want the use virtually-mapped kernel stacks 841 with guard pages. This causes kernel stack overflows to be 842 caught immediately rather than causing difficult-to-diagnose 843 corruption. 844 845 This is presently incompatible with KASAN because KASAN expects 846 the stack to map directly to the KASAN shadow map using a formula 847 that is incorrect if the stack is in vmalloc space. 848 849config ARCH_OPTIONAL_KERNEL_RWX 850 def_bool n 851 852config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 853 def_bool n 854 855config ARCH_HAS_STRICT_KERNEL_RWX 856 def_bool n 857 858config STRICT_KERNEL_RWX 859 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 860 depends on ARCH_HAS_STRICT_KERNEL_RWX 861 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 862 help 863 If this is set, kernel text and rodata memory will be made read-only, 864 and non-text memory will be made non-executable. This provides 865 protection against certain security exploits (e.g. executing the heap 866 or modifying text) 867 868 These features are considered standard security practice these days. 869 You should say Y here in almost all cases. 870 871config ARCH_HAS_STRICT_MODULE_RWX 872 def_bool n 873 874config STRICT_MODULE_RWX 875 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 876 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 877 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 878 help 879 If this is set, module text and rodata memory will be made read-only, 880 and non-text memory will be made non-executable. This provides 881 protection against certain security exploits (e.g. writing to text) 882 883# select if the architecture provides an asm/dma-direct.h header 884config ARCH_HAS_PHYS_TO_DMA 885 bool 886 887config ARCH_HAS_REFCOUNT 888 bool 889 help 890 An architecture selects this when it has implemented refcount_t 891 using open coded assembly primitives that provide an optimized 892 refcount_t implementation, possibly at the expense of some full 893 refcount state checks of CONFIG_REFCOUNT_FULL=y. 894 895 The refcount overflow check behavior, however, must be retained. 896 Catching overflows is the primary security concern for protecting 897 against bugs in reference counts. 898 899config REFCOUNT_FULL 900 bool "Perform full reference count validation at the expense of speed" 901 help 902 Enabling this switches the refcounting infrastructure from a fast 903 unchecked atomic_t implementation to a fully state checked 904 implementation, which can be (slightly) slower but provides protections 905 against various use-after-free conditions that can be used in 906 security flaw exploits. 907 908config HAVE_ARCH_COMPILER_H 909 bool 910 help 911 An architecture can select this if it provides an 912 asm/compiler.h header that should be included after 913 linux/compiler-*.h in order to override macro definitions that those 914 headers generally provide. 915 916config HAVE_ARCH_PREL32_RELOCATIONS 917 bool 918 help 919 May be selected by an architecture if it supports place-relative 920 32-bit relocations, both in the toolchain and in the module loader, 921 in which case relative references can be used in special sections 922 for PCI fixup, initcalls etc which are only half the size on 64 bit 923 architectures, and don't require runtime relocation on relocatable 924 kernels. 925 926config ARCH_USE_MEMREMAP_PROT 927 bool 928 929config LOCK_EVENT_COUNTS 930 bool "Locking event counts collection" 931 depends on DEBUG_FS 932 ---help--- 933 Enable light-weight counting of various locking related events 934 in the system with minimal performance impact. This reduces 935 the chance of application behavior change because of timing 936 differences. The counts are reported via debugfs. 937 938source "kernel/gcov/Kconfig" 939 940source "scripts/gcc-plugins/Kconfig" 941 942endmenu 943