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# Select if arch init_task must go in the __init_task_data section 264config ARCH_TASK_STRUCT_ON_STACK 265 bool 266 267# Select if arch has its private alloc_task_struct() function 268config ARCH_TASK_STRUCT_ALLOCATOR 269 bool 270 271config HAVE_ARCH_THREAD_STRUCT_WHITELIST 272 bool 273 depends on !ARCH_TASK_STRUCT_ALLOCATOR 274 help 275 An architecture should select this to provide hardened usercopy 276 knowledge about what region of the thread_struct should be 277 whitelisted for copying to userspace. Normally this is only the 278 FPU registers. Specifically, arch_thread_struct_whitelist() 279 should be implemented. Without this, the entire thread_struct 280 field in task_struct will be left whitelisted. 281 282# Select if arch has its private alloc_thread_stack() function 283config ARCH_THREAD_STACK_ALLOCATOR 284 bool 285 286# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 287config ARCH_WANTS_DYNAMIC_TASK_STRUCT 288 bool 289 290config ARCH_32BIT_OFF_T 291 bool 292 depends on !64BIT 293 help 294 All new 32-bit architectures should have 64-bit off_t type on 295 userspace side which corresponds to the loff_t kernel type. This 296 is the requirement for modern ABIs. Some existing architectures 297 still support 32-bit off_t. This option is enabled for all such 298 architectures explicitly. 299 300config HAVE_REGS_AND_STACK_ACCESS_API 301 bool 302 help 303 This symbol should be selected by an architecure if it supports 304 the API needed to access registers and stack entries from pt_regs, 305 declared in asm/ptrace.h 306 For example the kprobes-based event tracer needs this API. 307 308config HAVE_RSEQ 309 bool 310 depends on HAVE_REGS_AND_STACK_ACCESS_API 311 help 312 This symbol should be selected by an architecture if it 313 supports an implementation of restartable sequences. 314 315config HAVE_FUNCTION_ARG_ACCESS_API 316 bool 317 help 318 This symbol should be selected by an architecure if it supports 319 the API needed to access function arguments from pt_regs, 320 declared in asm/ptrace.h 321 322config HAVE_CLK 323 bool 324 help 325 The <linux/clk.h> calls support software clock gating and 326 thus are a key power management tool on many systems. 327 328config HAVE_HW_BREAKPOINT 329 bool 330 depends on PERF_EVENTS 331 332config HAVE_MIXED_BREAKPOINTS_REGS 333 bool 334 depends on HAVE_HW_BREAKPOINT 335 help 336 Depending on the arch implementation of hardware breakpoints, 337 some of them have separate registers for data and instruction 338 breakpoints addresses, others have mixed registers to store 339 them but define the access type in a control register. 340 Select this option if your arch implements breakpoints under the 341 latter fashion. 342 343config HAVE_USER_RETURN_NOTIFIER 344 bool 345 346config HAVE_PERF_EVENTS_NMI 347 bool 348 help 349 System hardware can generate an NMI using the perf event 350 subsystem. Also has support for calculating CPU cycle events 351 to determine how many clock cycles in a given period. 352 353config HAVE_HARDLOCKUP_DETECTOR_PERF 354 bool 355 depends on HAVE_PERF_EVENTS_NMI 356 help 357 The arch chooses to use the generic perf-NMI-based hardlockup 358 detector. Must define HAVE_PERF_EVENTS_NMI. 359 360config HAVE_NMI_WATCHDOG 361 depends on HAVE_NMI 362 bool 363 help 364 The arch provides a low level NMI watchdog. It provides 365 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 366 367config HAVE_HARDLOCKUP_DETECTOR_ARCH 368 bool 369 select HAVE_NMI_WATCHDOG 370 help 371 The arch chooses to provide its own hardlockup detector, which is 372 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 373 interfaces and parameters provided by hardlockup detector subsystem. 374 375config HAVE_PERF_REGS 376 bool 377 help 378 Support selective register dumps for perf events. This includes 379 bit-mapping of each registers and a unique architecture id. 380 381config HAVE_PERF_USER_STACK_DUMP 382 bool 383 help 384 Support user stack dumps for perf event samples. This needs 385 access to the user stack pointer which is not unified across 386 architectures. 387 388config HAVE_ARCH_JUMP_LABEL 389 bool 390 391config HAVE_ARCH_JUMP_LABEL_RELATIVE 392 bool 393 394config HAVE_RCU_TABLE_FREE 395 bool 396 397config HAVE_RCU_TABLE_NO_INVALIDATE 398 bool 399 400config HAVE_MMU_GATHER_PAGE_SIZE 401 bool 402 403config HAVE_MMU_GATHER_NO_GATHER 404 bool 405 406config ARCH_HAVE_NMI_SAFE_CMPXCHG 407 bool 408 409config HAVE_ALIGNED_STRUCT_PAGE 410 bool 411 help 412 This makes sure that struct pages are double word aligned and that 413 e.g. the SLUB allocator can perform double word atomic operations 414 on a struct page for better performance. However selecting this 415 might increase the size of a struct page by a word. 416 417config HAVE_CMPXCHG_LOCAL 418 bool 419 420config HAVE_CMPXCHG_DOUBLE 421 bool 422 423config ARCH_WEAK_RELEASE_ACQUIRE 424 bool 425 426config ARCH_WANT_IPC_PARSE_VERSION 427 bool 428 429config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 430 bool 431 432config ARCH_WANT_OLD_COMPAT_IPC 433 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 434 bool 435 436config HAVE_ARCH_SECCOMP_FILTER 437 bool 438 help 439 An arch should select this symbol if it provides all of these things: 440 - syscall_get_arch() 441 - syscall_get_arguments() 442 - syscall_rollback() 443 - syscall_set_return_value() 444 - SIGSYS siginfo_t support 445 - secure_computing is called from a ptrace_event()-safe context 446 - secure_computing return value is checked and a return value of -1 447 results in the system call being skipped immediately. 448 - seccomp syscall wired up 449 450config SECCOMP_FILTER 451 def_bool y 452 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 453 help 454 Enable tasks to build secure computing environments defined 455 in terms of Berkeley Packet Filter programs which implement 456 task-defined system call filtering polices. 457 458 See Documentation/userspace-api/seccomp_filter.rst for details. 459 460config HAVE_ARCH_STACKLEAK 461 bool 462 help 463 An architecture should select this if it has the code which 464 fills the used part of the kernel stack with the STACKLEAK_POISON 465 value before returning from system calls. 466 467config HAVE_STACKPROTECTOR 468 bool 469 help 470 An arch should select this symbol if: 471 - it has implemented a stack canary (e.g. __stack_chk_guard) 472 473config CC_HAS_STACKPROTECTOR_NONE 474 def_bool $(cc-option,-fno-stack-protector) 475 476config STACKPROTECTOR 477 bool "Stack Protector buffer overflow detection" 478 depends on HAVE_STACKPROTECTOR 479 depends on $(cc-option,-fstack-protector) 480 default y 481 help 482 This option turns on the "stack-protector" GCC feature. This 483 feature puts, at the beginning of functions, a canary value on 484 the stack just before the return address, and validates 485 the value just before actually returning. Stack based buffer 486 overflows (that need to overwrite this return address) now also 487 overwrite the canary, which gets detected and the attack is then 488 neutralized via a kernel panic. 489 490 Functions will have the stack-protector canary logic added if they 491 have an 8-byte or larger character array on the stack. 492 493 This feature requires gcc version 4.2 or above, or a distribution 494 gcc with the feature backported ("-fstack-protector"). 495 496 On an x86 "defconfig" build, this feature adds canary checks to 497 about 3% of all kernel functions, which increases kernel code size 498 by about 0.3%. 499 500config STACKPROTECTOR_STRONG 501 bool "Strong Stack Protector" 502 depends on STACKPROTECTOR 503 depends on $(cc-option,-fstack-protector-strong) 504 default y 505 help 506 Functions will have the stack-protector canary logic added in any 507 of the following conditions: 508 509 - local variable's address used as part of the right hand side of an 510 assignment or function argument 511 - local variable is an array (or union containing an array), 512 regardless of array type or length 513 - uses register local variables 514 515 This feature requires gcc version 4.9 or above, or a distribution 516 gcc with the feature backported ("-fstack-protector-strong"). 517 518 On an x86 "defconfig" build, this feature adds canary checks to 519 about 20% of all kernel functions, which increases the kernel code 520 size by about 2%. 521 522config HAVE_ARCH_WITHIN_STACK_FRAMES 523 bool 524 help 525 An architecture should select this if it can walk the kernel stack 526 frames to determine if an object is part of either the arguments 527 or local variables (i.e. that it excludes saved return addresses, 528 and similar) by implementing an inline arch_within_stack_frames(), 529 which is used by CONFIG_HARDENED_USERCOPY. 530 531config HAVE_CONTEXT_TRACKING 532 bool 533 help 534 Provide kernel/user boundaries probes necessary for subsystems 535 that need it, such as userspace RCU extended quiescent state. 536 Syscalls need to be wrapped inside user_exit()-user_enter() through 537 the slow path using TIF_NOHZ flag. Exceptions handlers must be 538 wrapped as well. Irqs are already protected inside 539 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 540 irq exit still need to be protected. 541 542config HAVE_VIRT_CPU_ACCOUNTING 543 bool 544 545config ARCH_HAS_SCALED_CPUTIME 546 bool 547 548config HAVE_VIRT_CPU_ACCOUNTING_GEN 549 bool 550 default y if 64BIT 551 help 552 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 553 Before enabling this option, arch code must be audited 554 to ensure there are no races in concurrent read/write of 555 cputime_t. For example, reading/writing 64-bit cputime_t on 556 some 32-bit arches may require multiple accesses, so proper 557 locking is needed to protect against concurrent accesses. 558 559 560config HAVE_IRQ_TIME_ACCOUNTING 561 bool 562 help 563 Archs need to ensure they use a high enough resolution clock to 564 support irq time accounting and then call enable_sched_clock_irqtime(). 565 566config HAVE_MOVE_PMD 567 bool 568 help 569 Archs that select this are able to move page tables at the PMD level. 570 571config HAVE_ARCH_TRANSPARENT_HUGEPAGE 572 bool 573 574config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 575 bool 576 577config HAVE_ARCH_HUGE_VMAP 578 bool 579 580config HAVE_ARCH_SOFT_DIRTY 581 bool 582 583config HAVE_MOD_ARCH_SPECIFIC 584 bool 585 help 586 The arch uses struct mod_arch_specific to store data. Many arches 587 just need a simple module loader without arch specific data - those 588 should not enable this. 589 590config MODULES_USE_ELF_RELA 591 bool 592 help 593 Modules only use ELF RELA relocations. Modules with ELF REL 594 relocations will give an error. 595 596config MODULES_USE_ELF_REL 597 bool 598 help 599 Modules only use ELF REL relocations. Modules with ELF RELA 600 relocations will give an error. 601 602config HAVE_IRQ_EXIT_ON_IRQ_STACK 603 bool 604 help 605 Architecture doesn't only execute the irq handler on the irq stack 606 but also irq_exit(). This way we can process softirqs on this irq 607 stack instead of switching to a new one when we call __do_softirq() 608 in the end of an hardirq. 609 This spares a stack switch and improves cache usage on softirq 610 processing. 611 612config PGTABLE_LEVELS 613 int 614 default 2 615 616config ARCH_HAS_ELF_RANDOMIZE 617 bool 618 help 619 An architecture supports choosing randomized locations for 620 stack, mmap, brk, and ET_DYN. Defined functions: 621 - arch_mmap_rnd() 622 - arch_randomize_brk() 623 624config HAVE_ARCH_MMAP_RND_BITS 625 bool 626 help 627 An arch should select this symbol if it supports setting a variable 628 number of bits for use in establishing the base address for mmap 629 allocations, has MMU enabled and provides values for both: 630 - ARCH_MMAP_RND_BITS_MIN 631 - ARCH_MMAP_RND_BITS_MAX 632 633config HAVE_EXIT_THREAD 634 bool 635 help 636 An architecture implements exit_thread. 637 638config ARCH_MMAP_RND_BITS_MIN 639 int 640 641config ARCH_MMAP_RND_BITS_MAX 642 int 643 644config ARCH_MMAP_RND_BITS_DEFAULT 645 int 646 647config ARCH_MMAP_RND_BITS 648 int "Number of bits to use for ASLR of mmap base address" if EXPERT 649 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 650 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 651 default ARCH_MMAP_RND_BITS_MIN 652 depends on HAVE_ARCH_MMAP_RND_BITS 653 help 654 This value can be used to select the number of bits to use to 655 determine the random offset to the base address of vma regions 656 resulting from mmap allocations. This value will be bounded 657 by the architecture's minimum and maximum supported values. 658 659 This value can be changed after boot using the 660 /proc/sys/vm/mmap_rnd_bits tunable 661 662config HAVE_ARCH_MMAP_RND_COMPAT_BITS 663 bool 664 help 665 An arch should select this symbol if it supports running applications 666 in compatibility mode, supports setting a variable number of bits for 667 use in establishing the base address for mmap allocations, has MMU 668 enabled and provides values for both: 669 - ARCH_MMAP_RND_COMPAT_BITS_MIN 670 - ARCH_MMAP_RND_COMPAT_BITS_MAX 671 672config ARCH_MMAP_RND_COMPAT_BITS_MIN 673 int 674 675config ARCH_MMAP_RND_COMPAT_BITS_MAX 676 int 677 678config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 679 int 680 681config ARCH_MMAP_RND_COMPAT_BITS 682 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 683 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 684 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 685 default ARCH_MMAP_RND_COMPAT_BITS_MIN 686 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 687 help 688 This value can be used to select the number of bits to use to 689 determine the random offset to the base address of vma regions 690 resulting from mmap allocations for compatible applications This 691 value will be bounded by the architecture's minimum and maximum 692 supported values. 693 694 This value can be changed after boot using the 695 /proc/sys/vm/mmap_rnd_compat_bits tunable 696 697config HAVE_ARCH_COMPAT_MMAP_BASES 698 bool 699 help 700 This allows 64bit applications to invoke 32-bit mmap() syscall 701 and vice-versa 32-bit applications to call 64-bit mmap(). 702 Required for applications doing different bitness syscalls. 703 704config HAVE_COPY_THREAD_TLS 705 bool 706 help 707 Architecture provides copy_thread_tls to accept tls argument via 708 normal C parameter passing, rather than extracting the syscall 709 argument from pt_regs. 710 711config HAVE_STACK_VALIDATION 712 bool 713 help 714 Architecture supports the 'objtool check' host tool command, which 715 performs compile-time stack metadata validation. 716 717config HAVE_RELIABLE_STACKTRACE 718 bool 719 help 720 Architecture has a save_stack_trace_tsk_reliable() function which 721 only returns a stack trace if it can guarantee the trace is reliable. 722 723config HAVE_ARCH_HASH 724 bool 725 default n 726 help 727 If this is set, the architecture provides an <asm/hash.h> 728 file which provides platform-specific implementations of some 729 functions in <linux/hash.h> or fs/namei.c. 730 731config HAVE_ARCH_NVRAM_OPS 732 bool 733 734config ISA_BUS_API 735 def_bool ISA 736 737# 738# ABI hall of shame 739# 740config CLONE_BACKWARDS 741 bool 742 help 743 Architecture has tls passed as the 4th argument of clone(2), 744 not the 5th one. 745 746config CLONE_BACKWARDS2 747 bool 748 help 749 Architecture has the first two arguments of clone(2) swapped. 750 751config CLONE_BACKWARDS3 752 bool 753 help 754 Architecture has tls passed as the 3rd argument of clone(2), 755 not the 5th one. 756 757config ODD_RT_SIGACTION 758 bool 759 help 760 Architecture has unusual rt_sigaction(2) arguments 761 762config OLD_SIGSUSPEND 763 bool 764 help 765 Architecture has old sigsuspend(2) syscall, of one-argument variety 766 767config OLD_SIGSUSPEND3 768 bool 769 help 770 Even weirder antique ABI - three-argument sigsuspend(2) 771 772config OLD_SIGACTION 773 bool 774 help 775 Architecture has old sigaction(2) syscall. Nope, not the same 776 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 777 but fairly different variant of sigaction(2), thanks to OSF/1 778 compatibility... 779 780config COMPAT_OLD_SIGACTION 781 bool 782 783config 64BIT_TIME 784 def_bool y 785 help 786 This should be selected by all architectures that need to support 787 new system calls with a 64-bit time_t. This is relevant on all 32-bit 788 architectures, and 64-bit architectures as part of compat syscall 789 handling. 790 791config COMPAT_32BIT_TIME 792 def_bool !64BIT || COMPAT 793 help 794 This enables 32 bit time_t support in addition to 64 bit time_t support. 795 This is relevant on all 32-bit architectures, and 64-bit architectures 796 as part of compat syscall handling. 797 798config ARCH_NO_COHERENT_DMA_MMAP 799 bool 800 801config ARCH_NO_PREEMPT 802 bool 803 804config CPU_NO_EFFICIENT_FFS 805 def_bool n 806 807config HAVE_ARCH_VMAP_STACK 808 def_bool n 809 help 810 An arch should select this symbol if it can support kernel stacks 811 in vmalloc space. This means: 812 813 - vmalloc space must be large enough to hold many kernel stacks. 814 This may rule out many 32-bit architectures. 815 816 - Stacks in vmalloc space need to work reliably. For example, if 817 vmap page tables are created on demand, either this mechanism 818 needs to work while the stack points to a virtual address with 819 unpopulated page tables or arch code (switch_to() and switch_mm(), 820 most likely) needs to ensure that the stack's page table entries 821 are populated before running on a possibly unpopulated stack. 822 823 - If the stack overflows into a guard page, something reasonable 824 should happen. The definition of "reasonable" is flexible, but 825 instantly rebooting without logging anything would be unfriendly. 826 827config VMAP_STACK 828 default y 829 bool "Use a virtually-mapped stack" 830 depends on HAVE_ARCH_VMAP_STACK && !KASAN 831 ---help--- 832 Enable this if you want the use virtually-mapped kernel stacks 833 with guard pages. This causes kernel stack overflows to be 834 caught immediately rather than causing difficult-to-diagnose 835 corruption. 836 837 This is presently incompatible with KASAN because KASAN expects 838 the stack to map directly to the KASAN shadow map using a formula 839 that is incorrect if the stack is in vmalloc space. 840 841config ARCH_OPTIONAL_KERNEL_RWX 842 def_bool n 843 844config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 845 def_bool n 846 847config ARCH_HAS_STRICT_KERNEL_RWX 848 def_bool n 849 850config STRICT_KERNEL_RWX 851 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 852 depends on ARCH_HAS_STRICT_KERNEL_RWX 853 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 854 help 855 If this is set, kernel text and rodata memory will be made read-only, 856 and non-text memory will be made non-executable. This provides 857 protection against certain security exploits (e.g. executing the heap 858 or modifying text) 859 860 These features are considered standard security practice these days. 861 You should say Y here in almost all cases. 862 863config ARCH_HAS_STRICT_MODULE_RWX 864 def_bool n 865 866config STRICT_MODULE_RWX 867 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 868 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 869 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 870 help 871 If this is set, module text and rodata memory will be made read-only, 872 and non-text memory will be made non-executable. This provides 873 protection against certain security exploits (e.g. writing to text) 874 875# select if the architecture provides an asm/dma-direct.h header 876config ARCH_HAS_PHYS_TO_DMA 877 bool 878 879config ARCH_HAS_REFCOUNT 880 bool 881 help 882 An architecture selects this when it has implemented refcount_t 883 using open coded assembly primitives that provide an optimized 884 refcount_t implementation, possibly at the expense of some full 885 refcount state checks of CONFIG_REFCOUNT_FULL=y. 886 887 The refcount overflow check behavior, however, must be retained. 888 Catching overflows is the primary security concern for protecting 889 against bugs in reference counts. 890 891config REFCOUNT_FULL 892 bool "Perform full reference count validation at the expense of speed" 893 help 894 Enabling this switches the refcounting infrastructure from a fast 895 unchecked atomic_t implementation to a fully state checked 896 implementation, which can be (slightly) slower but provides protections 897 against various use-after-free conditions that can be used in 898 security flaw exploits. 899 900config HAVE_ARCH_COMPILER_H 901 bool 902 help 903 An architecture can select this if it provides an 904 asm/compiler.h header that should be included after 905 linux/compiler-*.h in order to override macro definitions that those 906 headers generally provide. 907 908config HAVE_ARCH_PREL32_RELOCATIONS 909 bool 910 help 911 May be selected by an architecture if it supports place-relative 912 32-bit relocations, both in the toolchain and in the module loader, 913 in which case relative references can be used in special sections 914 for PCI fixup, initcalls etc which are only half the size on 64 bit 915 architectures, and don't require runtime relocation on relocatable 916 kernels. 917 918config ARCH_USE_MEMREMAP_PROT 919 bool 920 921config LOCK_EVENT_COUNTS 922 bool "Locking event counts collection" 923 depends on DEBUG_FS 924 ---help--- 925 Enable light-weight counting of various locking related events 926 in the system with minimal performance impact. This reduces 927 the chance of application behavior change because of timing 928 differences. The counts are reported via debugfs. 929 930source "kernel/gcov/Kconfig" 931 932source "scripts/gcc-plugins/Kconfig" 933 934endmenu 935