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 KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config HOTPLUG_SMT 28 bool 29 30config GENERIC_ENTRY 31 bool 32 33config OPROFILE 34 tristate "OProfile system profiling" 35 depends on PROFILING 36 depends on HAVE_OPROFILE 37 select RING_BUFFER 38 select RING_BUFFER_ALLOW_SWAP 39 help 40 OProfile is a profiling system capable of profiling the 41 whole system, include the kernel, kernel modules, libraries, 42 and applications. 43 44 If unsure, say N. 45 46config OPROFILE_EVENT_MULTIPLEX 47 bool "OProfile multiplexing support (EXPERIMENTAL)" 48 default n 49 depends on OPROFILE && X86 50 help 51 The number of hardware counters is limited. The multiplexing 52 feature enables OProfile to gather more events than counters 53 are provided by the hardware. This is realized by switching 54 between events at a user specified time interval. 55 56 If unsure, say N. 57 58config HAVE_OPROFILE 59 bool 60 61config OPROFILE_NMI_TIMER 62 def_bool y 63 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 64 65config KPROBES 66 bool "Kprobes" 67 depends on MODULES 68 depends on HAVE_KPROBES 69 select KALLSYMS 70 help 71 Kprobes allows you to trap at almost any kernel address and 72 execute a callback function. register_kprobe() establishes 73 a probepoint and specifies the callback. Kprobes is useful 74 for kernel debugging, non-intrusive instrumentation and testing. 75 If in doubt, say "N". 76 77config JUMP_LABEL 78 bool "Optimize very unlikely/likely branches" 79 depends on HAVE_ARCH_JUMP_LABEL 80 depends on CC_HAS_ASM_GOTO 81 help 82 This option enables a transparent branch optimization that 83 makes certain almost-always-true or almost-always-false branch 84 conditions even cheaper to execute within the kernel. 85 86 Certain performance-sensitive kernel code, such as trace points, 87 scheduler functionality, networking code and KVM have such 88 branches and include support for this optimization technique. 89 90 If it is detected that the compiler has support for "asm goto", 91 the kernel will compile such branches with just a nop 92 instruction. When the condition flag is toggled to true, the 93 nop will be converted to a jump instruction to execute the 94 conditional block of instructions. 95 96 This technique lowers overhead and stress on the branch prediction 97 of the processor and generally makes the kernel faster. The update 98 of the condition is slower, but those are always very rare. 99 100 ( On 32-bit x86, the necessary options added to the compiler 101 flags may increase the size of the kernel slightly. ) 102 103config STATIC_KEYS_SELFTEST 104 bool "Static key selftest" 105 depends on JUMP_LABEL 106 help 107 Boot time self-test of the branch patching code. 108 109config OPTPROBES 110 def_bool y 111 depends on KPROBES && HAVE_OPTPROBES 112 select TASKS_RCU if PREEMPTION 113 114config KPROBES_ON_FTRACE 115 def_bool y 116 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 117 depends on DYNAMIC_FTRACE_WITH_REGS 118 help 119 If function tracer is enabled and the arch supports full 120 passing of pt_regs to function tracing, then kprobes can 121 optimize on top of function tracing. 122 123config UPROBES 124 def_bool n 125 depends on ARCH_SUPPORTS_UPROBES 126 help 127 Uprobes is the user-space counterpart to kprobes: they 128 enable instrumentation applications (such as 'perf probe') 129 to establish unintrusive probes in user-space binaries and 130 libraries, by executing handler functions when the probes 131 are hit by user-space applications. 132 133 ( These probes come in the form of single-byte breakpoints, 134 managed by the kernel and kept transparent to the probed 135 application. ) 136 137config HAVE_EFFICIENT_UNALIGNED_ACCESS 138 bool 139 help 140 Some architectures are unable to perform unaligned accesses 141 without the use of get_unaligned/put_unaligned. Others are 142 unable to perform such accesses efficiently (e.g. trap on 143 unaligned access and require fixing it up in the exception 144 handler.) 145 146 This symbol should be selected by an architecture if it can 147 perform unaligned accesses efficiently to allow different 148 code paths to be selected for these cases. Some network 149 drivers, for example, could opt to not fix up alignment 150 problems with received packets if doing so would not help 151 much. 152 153 See Documentation/core-api/unaligned-memory-access.rst for more 154 information on the topic of unaligned memory accesses. 155 156config ARCH_USE_BUILTIN_BSWAP 157 bool 158 help 159 Modern versions of GCC (since 4.4) have builtin functions 160 for handling byte-swapping. Using these, instead of the old 161 inline assembler that the architecture code provides in the 162 __arch_bswapXX() macros, allows the compiler to see what's 163 happening and offers more opportunity for optimisation. In 164 particular, the compiler will be able to combine the byteswap 165 with a nearby load or store and use load-and-swap or 166 store-and-swap instructions if the architecture has them. It 167 should almost *never* result in code which is worse than the 168 hand-coded assembler in <asm/swab.h>. But just in case it 169 does, the use of the builtins is optional. 170 171 Any architecture with load-and-swap or store-and-swap 172 instructions should set this. And it shouldn't hurt to set it 173 on architectures that don't have such instructions. 174 175config KRETPROBES 176 def_bool y 177 depends on KPROBES && HAVE_KRETPROBES 178 179config USER_RETURN_NOTIFIER 180 bool 181 depends on HAVE_USER_RETURN_NOTIFIER 182 help 183 Provide a kernel-internal notification when a cpu is about to 184 switch to user mode. 185 186config HAVE_IOREMAP_PROT 187 bool 188 189config HAVE_KPROBES 190 bool 191 192config HAVE_KRETPROBES 193 bool 194 195config HAVE_OPTPROBES 196 bool 197 198config HAVE_KPROBES_ON_FTRACE 199 bool 200 201config HAVE_FUNCTION_ERROR_INJECTION 202 bool 203 204config HAVE_NMI 205 bool 206 207# 208# An arch should select this if it provides all these things: 209# 210# task_pt_regs() in asm/processor.h or asm/ptrace.h 211# arch_has_single_step() if there is hardware single-step support 212# arch_has_block_step() if there is hardware block-step support 213# asm/syscall.h supplying asm-generic/syscall.h interface 214# linux/regset.h user_regset interfaces 215# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 216# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 217# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 218# signal delivery calls tracehook_signal_handler() 219# 220config HAVE_ARCH_TRACEHOOK 221 bool 222 223config HAVE_DMA_CONTIGUOUS 224 bool 225 226config GENERIC_SMP_IDLE_THREAD 227 bool 228 229config GENERIC_IDLE_POLL_SETUP 230 bool 231 232config ARCH_HAS_FORTIFY_SOURCE 233 bool 234 help 235 An architecture should select this when it can successfully 236 build and run with CONFIG_FORTIFY_SOURCE. 237 238# 239# Select if the arch provides a historic keepinit alias for the retain_initrd 240# command line option 241# 242config ARCH_HAS_KEEPINITRD 243 bool 244 245# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 246config ARCH_HAS_SET_MEMORY 247 bool 248 249# Select if arch has all set_direct_map_invalid/default() functions 250config ARCH_HAS_SET_DIRECT_MAP 251 bool 252 253# 254# Select if the architecture provides the arch_dma_set_uncached symbol to 255# either provide an uncached segement alias for a DMA allocation, or 256# to remap the page tables in place. 257# 258config ARCH_HAS_DMA_SET_UNCACHED 259 bool 260 261# 262# Select if the architectures provides the arch_dma_clear_uncached symbol 263# to undo an in-place page table remap for uncached access. 264# 265config ARCH_HAS_DMA_CLEAR_UNCACHED 266 bool 267 268# Select if arch init_task must go in the __init_task_data section 269config ARCH_TASK_STRUCT_ON_STACK 270 bool 271 272# Select if arch has its private alloc_task_struct() function 273config ARCH_TASK_STRUCT_ALLOCATOR 274 bool 275 276config HAVE_ARCH_THREAD_STRUCT_WHITELIST 277 bool 278 depends on !ARCH_TASK_STRUCT_ALLOCATOR 279 help 280 An architecture should select this to provide hardened usercopy 281 knowledge about what region of the thread_struct should be 282 whitelisted for copying to userspace. Normally this is only the 283 FPU registers. Specifically, arch_thread_struct_whitelist() 284 should be implemented. Without this, the entire thread_struct 285 field in task_struct will be left whitelisted. 286 287# Select if arch has its private alloc_thread_stack() function 288config ARCH_THREAD_STACK_ALLOCATOR 289 bool 290 291# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 292config ARCH_WANTS_DYNAMIC_TASK_STRUCT 293 bool 294 295config ARCH_32BIT_OFF_T 296 bool 297 depends on !64BIT 298 help 299 All new 32-bit architectures should have 64-bit off_t type on 300 userspace side which corresponds to the loff_t kernel type. This 301 is the requirement for modern ABIs. Some existing architectures 302 still support 32-bit off_t. This option is enabled for all such 303 architectures explicitly. 304 305config HAVE_ASM_MODVERSIONS 306 bool 307 help 308 This symbol should be selected by an architecure if it provides 309 <asm/asm-prototypes.h> to support the module versioning for symbols 310 exported from assembly code. 311 312config HAVE_REGS_AND_STACK_ACCESS_API 313 bool 314 help 315 This symbol should be selected by an architecure if it supports 316 the API needed to access registers and stack entries from pt_regs, 317 declared in asm/ptrace.h 318 For example the kprobes-based event tracer needs this API. 319 320config HAVE_RSEQ 321 bool 322 depends on HAVE_REGS_AND_STACK_ACCESS_API 323 help 324 This symbol should be selected by an architecture if it 325 supports an implementation of restartable sequences. 326 327config HAVE_FUNCTION_ARG_ACCESS_API 328 bool 329 help 330 This symbol should be selected by an architecure if it supports 331 the API needed to access function arguments from pt_regs, 332 declared in asm/ptrace.h 333 334config HAVE_HW_BREAKPOINT 335 bool 336 depends on PERF_EVENTS 337 338config HAVE_MIXED_BREAKPOINTS_REGS 339 bool 340 depends on HAVE_HW_BREAKPOINT 341 help 342 Depending on the arch implementation of hardware breakpoints, 343 some of them have separate registers for data and instruction 344 breakpoints addresses, others have mixed registers to store 345 them but define the access type in a control register. 346 Select this option if your arch implements breakpoints under the 347 latter fashion. 348 349config HAVE_USER_RETURN_NOTIFIER 350 bool 351 352config HAVE_PERF_EVENTS_NMI 353 bool 354 help 355 System hardware can generate an NMI using the perf event 356 subsystem. Also has support for calculating CPU cycle events 357 to determine how many clock cycles in a given period. 358 359config HAVE_HARDLOCKUP_DETECTOR_PERF 360 bool 361 depends on HAVE_PERF_EVENTS_NMI 362 help 363 The arch chooses to use the generic perf-NMI-based hardlockup 364 detector. Must define HAVE_PERF_EVENTS_NMI. 365 366config HAVE_NMI_WATCHDOG 367 depends on HAVE_NMI 368 bool 369 help 370 The arch provides a low level NMI watchdog. It provides 371 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 372 373config HAVE_HARDLOCKUP_DETECTOR_ARCH 374 bool 375 select HAVE_NMI_WATCHDOG 376 help 377 The arch chooses to provide its own hardlockup detector, which is 378 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 379 interfaces and parameters provided by hardlockup detector subsystem. 380 381config HAVE_PERF_REGS 382 bool 383 help 384 Support selective register dumps for perf events. This includes 385 bit-mapping of each registers and a unique architecture id. 386 387config HAVE_PERF_USER_STACK_DUMP 388 bool 389 help 390 Support user stack dumps for perf event samples. This needs 391 access to the user stack pointer which is not unified across 392 architectures. 393 394config HAVE_ARCH_JUMP_LABEL 395 bool 396 397config HAVE_ARCH_JUMP_LABEL_RELATIVE 398 bool 399 400config MMU_GATHER_TABLE_FREE 401 bool 402 403config MMU_GATHER_RCU_TABLE_FREE 404 bool 405 select MMU_GATHER_TABLE_FREE 406 407config MMU_GATHER_PAGE_SIZE 408 bool 409 410config MMU_GATHER_NO_RANGE 411 bool 412 413config MMU_GATHER_NO_GATHER 414 bool 415 depends on MMU_GATHER_TABLE_FREE 416 417config ARCH_HAVE_NMI_SAFE_CMPXCHG 418 bool 419 420config HAVE_ALIGNED_STRUCT_PAGE 421 bool 422 help 423 This makes sure that struct pages are double word aligned and that 424 e.g. the SLUB allocator can perform double word atomic operations 425 on a struct page for better performance. However selecting this 426 might increase the size of a struct page by a word. 427 428config HAVE_CMPXCHG_LOCAL 429 bool 430 431config HAVE_CMPXCHG_DOUBLE 432 bool 433 434config ARCH_WEAK_RELEASE_ACQUIRE 435 bool 436 437config ARCH_WANT_IPC_PARSE_VERSION 438 bool 439 440config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 441 bool 442 443config ARCH_WANT_OLD_COMPAT_IPC 444 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 445 bool 446 447config HAVE_ARCH_SECCOMP_FILTER 448 bool 449 help 450 An arch should select this symbol if it provides all of these things: 451 - syscall_get_arch() 452 - syscall_get_arguments() 453 - syscall_rollback() 454 - syscall_set_return_value() 455 - SIGSYS siginfo_t support 456 - secure_computing is called from a ptrace_event()-safe context 457 - secure_computing return value is checked and a return value of -1 458 results in the system call being skipped immediately. 459 - seccomp syscall wired up 460 461config SECCOMP_FILTER 462 def_bool y 463 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 464 help 465 Enable tasks to build secure computing environments defined 466 in terms of Berkeley Packet Filter programs which implement 467 task-defined system call filtering polices. 468 469 See Documentation/userspace-api/seccomp_filter.rst for details. 470 471config HAVE_ARCH_STACKLEAK 472 bool 473 help 474 An architecture should select this if it has the code which 475 fills the used part of the kernel stack with the STACKLEAK_POISON 476 value before returning from system calls. 477 478config HAVE_STACKPROTECTOR 479 bool 480 help 481 An arch should select this symbol if: 482 - it has implemented a stack canary (e.g. __stack_chk_guard) 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 ARCH_SUPPORTS_SHADOW_CALL_STACK 531 bool 532 help 533 An architecture should select this if it supports Clang's Shadow 534 Call Stack and implements runtime support for shadow stack 535 switching. 536 537config SHADOW_CALL_STACK 538 bool "Clang Shadow Call Stack" 539 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 540 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 541 help 542 This option enables Clang's Shadow Call Stack, which uses a 543 shadow stack to protect function return addresses from being 544 overwritten by an attacker. More information can be found in 545 Clang's documentation: 546 547 https://clang.llvm.org/docs/ShadowCallStack.html 548 549 Note that security guarantees in the kernel differ from the 550 ones documented for user space. The kernel must store addresses 551 of shadow stacks in memory, which means an attacker capable of 552 reading and writing arbitrary memory may be able to locate them 553 and hijack control flow by modifying the stacks. 554 555config HAVE_ARCH_WITHIN_STACK_FRAMES 556 bool 557 help 558 An architecture should select this if it can walk the kernel stack 559 frames to determine if an object is part of either the arguments 560 or local variables (i.e. that it excludes saved return addresses, 561 and similar) by implementing an inline arch_within_stack_frames(), 562 which is used by CONFIG_HARDENED_USERCOPY. 563 564config HAVE_CONTEXT_TRACKING 565 bool 566 help 567 Provide kernel/user boundaries probes necessary for subsystems 568 that need it, such as userspace RCU extended quiescent state. 569 Syscalls need to be wrapped inside user_exit()-user_enter(), either 570 optimized behind static key or through the slow path using TIF_NOHZ 571 flag. Exceptions handlers must be wrapped as well. Irqs are already 572 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 573 handling on irq exit still need to be protected. 574 575config HAVE_TIF_NOHZ 576 bool 577 help 578 Arch relies on TIF_NOHZ and syscall slow path to implement context 579 tracking calls to user_enter()/user_exit(). 580 581config HAVE_VIRT_CPU_ACCOUNTING 582 bool 583 584config ARCH_HAS_SCALED_CPUTIME 585 bool 586 587config HAVE_VIRT_CPU_ACCOUNTING_GEN 588 bool 589 default y if 64BIT 590 help 591 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 592 Before enabling this option, arch code must be audited 593 to ensure there are no races in concurrent read/write of 594 cputime_t. For example, reading/writing 64-bit cputime_t on 595 some 32-bit arches may require multiple accesses, so proper 596 locking is needed to protect against concurrent accesses. 597 598 599config HAVE_IRQ_TIME_ACCOUNTING 600 bool 601 help 602 Archs need to ensure they use a high enough resolution clock to 603 support irq time accounting and then call enable_sched_clock_irqtime(). 604 605config HAVE_MOVE_PMD 606 bool 607 help 608 Archs that select this are able to move page tables at the PMD level. 609 610config HAVE_ARCH_TRANSPARENT_HUGEPAGE 611 bool 612 613config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 614 bool 615 616config HAVE_ARCH_HUGE_VMAP 617 bool 618 619config ARCH_WANT_HUGE_PMD_SHARE 620 bool 621 622config HAVE_ARCH_SOFT_DIRTY 623 bool 624 625config HAVE_MOD_ARCH_SPECIFIC 626 bool 627 help 628 The arch uses struct mod_arch_specific to store data. Many arches 629 just need a simple module loader without arch specific data - those 630 should not enable this. 631 632config MODULES_USE_ELF_RELA 633 bool 634 help 635 Modules only use ELF RELA relocations. Modules with ELF REL 636 relocations will give an error. 637 638config MODULES_USE_ELF_REL 639 bool 640 help 641 Modules only use ELF REL relocations. Modules with ELF RELA 642 relocations will give an error. 643 644config HAVE_IRQ_EXIT_ON_IRQ_STACK 645 bool 646 help 647 Architecture doesn't only execute the irq handler on the irq stack 648 but also irq_exit(). This way we can process softirqs on this irq 649 stack instead of switching to a new one when we call __do_softirq() 650 in the end of an hardirq. 651 This spares a stack switch and improves cache usage on softirq 652 processing. 653 654config PGTABLE_LEVELS 655 int 656 default 2 657 658config ARCH_HAS_ELF_RANDOMIZE 659 bool 660 help 661 An architecture supports choosing randomized locations for 662 stack, mmap, brk, and ET_DYN. Defined functions: 663 - arch_mmap_rnd() 664 - arch_randomize_brk() 665 666config HAVE_ARCH_MMAP_RND_BITS 667 bool 668 help 669 An arch should select this symbol if it supports setting a variable 670 number of bits for use in establishing the base address for mmap 671 allocations, has MMU enabled and provides values for both: 672 - ARCH_MMAP_RND_BITS_MIN 673 - ARCH_MMAP_RND_BITS_MAX 674 675config HAVE_EXIT_THREAD 676 bool 677 help 678 An architecture implements exit_thread. 679 680config ARCH_MMAP_RND_BITS_MIN 681 int 682 683config ARCH_MMAP_RND_BITS_MAX 684 int 685 686config ARCH_MMAP_RND_BITS_DEFAULT 687 int 688 689config ARCH_MMAP_RND_BITS 690 int "Number of bits to use for ASLR of mmap base address" if EXPERT 691 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 692 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 693 default ARCH_MMAP_RND_BITS_MIN 694 depends on HAVE_ARCH_MMAP_RND_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. This value will be bounded 699 by the architecture's minimum and maximum supported values. 700 701 This value can be changed after boot using the 702 /proc/sys/vm/mmap_rnd_bits tunable 703 704config HAVE_ARCH_MMAP_RND_COMPAT_BITS 705 bool 706 help 707 An arch should select this symbol if it supports running applications 708 in compatibility mode, supports setting a variable number of bits for 709 use in establishing the base address for mmap allocations, has MMU 710 enabled and provides values for both: 711 - ARCH_MMAP_RND_COMPAT_BITS_MIN 712 - ARCH_MMAP_RND_COMPAT_BITS_MAX 713 714config ARCH_MMAP_RND_COMPAT_BITS_MIN 715 int 716 717config ARCH_MMAP_RND_COMPAT_BITS_MAX 718 int 719 720config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 721 int 722 723config ARCH_MMAP_RND_COMPAT_BITS 724 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 725 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 726 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 727 default ARCH_MMAP_RND_COMPAT_BITS_MIN 728 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 729 help 730 This value can be used to select the number of bits to use to 731 determine the random offset to the base address of vma regions 732 resulting from mmap allocations for compatible applications This 733 value will be bounded by the architecture's minimum and maximum 734 supported values. 735 736 This value can be changed after boot using the 737 /proc/sys/vm/mmap_rnd_compat_bits tunable 738 739config HAVE_ARCH_COMPAT_MMAP_BASES 740 bool 741 help 742 This allows 64bit applications to invoke 32-bit mmap() syscall 743 and vice-versa 32-bit applications to call 64-bit mmap(). 744 Required for applications doing different bitness syscalls. 745 746# This allows to use a set of generic functions to determine mmap base 747# address by giving priority to top-down scheme only if the process 748# is not in legacy mode (compat task, unlimited stack size or 749# sysctl_legacy_va_layout). 750# Architecture that selects this option can provide its own version of: 751# - STACK_RND_MASK 752config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 753 bool 754 depends on MMU 755 select ARCH_HAS_ELF_RANDOMIZE 756 757config HAVE_STACK_VALIDATION 758 bool 759 help 760 Architecture supports the 'objtool check' host tool command, which 761 performs compile-time stack metadata validation. 762 763config HAVE_RELIABLE_STACKTRACE 764 bool 765 help 766 Architecture has either save_stack_trace_tsk_reliable() or 767 arch_stack_walk_reliable() function which only returns a stack trace 768 if it can guarantee the trace is reliable. 769 770config HAVE_ARCH_HASH 771 bool 772 default n 773 help 774 If this is set, the architecture provides an <asm/hash.h> 775 file which provides platform-specific implementations of some 776 functions in <linux/hash.h> or fs/namei.c. 777 778config HAVE_ARCH_NVRAM_OPS 779 bool 780 781config ISA_BUS_API 782 def_bool ISA 783 784# 785# ABI hall of shame 786# 787config CLONE_BACKWARDS 788 bool 789 help 790 Architecture has tls passed as the 4th argument of clone(2), 791 not the 5th one. 792 793config CLONE_BACKWARDS2 794 bool 795 help 796 Architecture has the first two arguments of clone(2) swapped. 797 798config CLONE_BACKWARDS3 799 bool 800 help 801 Architecture has tls passed as the 3rd argument of clone(2), 802 not the 5th one. 803 804config ODD_RT_SIGACTION 805 bool 806 help 807 Architecture has unusual rt_sigaction(2) arguments 808 809config OLD_SIGSUSPEND 810 bool 811 help 812 Architecture has old sigsuspend(2) syscall, of one-argument variety 813 814config OLD_SIGSUSPEND3 815 bool 816 help 817 Even weirder antique ABI - three-argument sigsuspend(2) 818 819config OLD_SIGACTION 820 bool 821 help 822 Architecture has old sigaction(2) syscall. Nope, not the same 823 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 824 but fairly different variant of sigaction(2), thanks to OSF/1 825 compatibility... 826 827config COMPAT_OLD_SIGACTION 828 bool 829 830config COMPAT_32BIT_TIME 831 bool "Provide system calls for 32-bit time_t" 832 default !64BIT || COMPAT 833 help 834 This enables 32 bit time_t support in addition to 64 bit time_t support. 835 This is relevant on all 32-bit architectures, and 64-bit architectures 836 as part of compat syscall handling. 837 838config ARCH_NO_PREEMPT 839 bool 840 841config ARCH_SUPPORTS_RT 842 bool 843 844config CPU_NO_EFFICIENT_FFS 845 def_bool n 846 847config HAVE_ARCH_VMAP_STACK 848 def_bool n 849 help 850 An arch should select this symbol if it can support kernel stacks 851 in vmalloc space. This means: 852 853 - vmalloc space must be large enough to hold many kernel stacks. 854 This may rule out many 32-bit architectures. 855 856 - Stacks in vmalloc space need to work reliably. For example, if 857 vmap page tables are created on demand, either this mechanism 858 needs to work while the stack points to a virtual address with 859 unpopulated page tables or arch code (switch_to() and switch_mm(), 860 most likely) needs to ensure that the stack's page table entries 861 are populated before running on a possibly unpopulated stack. 862 863 - If the stack overflows into a guard page, something reasonable 864 should happen. The definition of "reasonable" is flexible, but 865 instantly rebooting without logging anything would be unfriendly. 866 867config VMAP_STACK 868 default y 869 bool "Use a virtually-mapped stack" 870 depends on HAVE_ARCH_VMAP_STACK 871 depends on !KASAN || KASAN_VMALLOC 872 help 873 Enable this if you want the use virtually-mapped kernel stacks 874 with guard pages. This causes kernel stack overflows to be 875 caught immediately rather than causing difficult-to-diagnose 876 corruption. 877 878 To use this with KASAN, the architecture must support backing 879 virtual mappings with real shadow memory, and KASAN_VMALLOC must 880 be enabled. 881 882config ARCH_OPTIONAL_KERNEL_RWX 883 def_bool n 884 885config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 886 def_bool n 887 888config ARCH_HAS_STRICT_KERNEL_RWX 889 def_bool n 890 891config STRICT_KERNEL_RWX 892 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 893 depends on ARCH_HAS_STRICT_KERNEL_RWX 894 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 895 help 896 If this is set, kernel text and rodata memory will be made read-only, 897 and non-text memory will be made non-executable. This provides 898 protection against certain security exploits (e.g. executing the heap 899 or modifying text) 900 901 These features are considered standard security practice these days. 902 You should say Y here in almost all cases. 903 904config ARCH_HAS_STRICT_MODULE_RWX 905 def_bool n 906 907config STRICT_MODULE_RWX 908 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 909 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 910 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 911 help 912 If this is set, module text and rodata memory will be made read-only, 913 and non-text memory will be made non-executable. This provides 914 protection against certain security exploits (e.g. writing to text) 915 916# select if the architecture provides an asm/dma-direct.h header 917config ARCH_HAS_PHYS_TO_DMA 918 bool 919 920config HAVE_ARCH_COMPILER_H 921 bool 922 help 923 An architecture can select this if it provides an 924 asm/compiler.h header that should be included after 925 linux/compiler-*.h in order to override macro definitions that those 926 headers generally provide. 927 928config HAVE_ARCH_PREL32_RELOCATIONS 929 bool 930 help 931 May be selected by an architecture if it supports place-relative 932 32-bit relocations, both in the toolchain and in the module loader, 933 in which case relative references can be used in special sections 934 for PCI fixup, initcalls etc which are only half the size on 64 bit 935 architectures, and don't require runtime relocation on relocatable 936 kernels. 937 938config ARCH_USE_MEMREMAP_PROT 939 bool 940 941config LOCK_EVENT_COUNTS 942 bool "Locking event counts collection" 943 depends on DEBUG_FS 944 help 945 Enable light-weight counting of various locking related events 946 in the system with minimal performance impact. This reduces 947 the chance of application behavior change because of timing 948 differences. The counts are reported via debugfs. 949 950# Select if the architecture has support for applying RELR relocations. 951config ARCH_HAS_RELR 952 bool 953 954config RELR 955 bool "Use RELR relocation packing" 956 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 957 default y 958 help 959 Store the kernel's dynamic relocations in the RELR relocation packing 960 format. Requires a compatible linker (LLD supports this feature), as 961 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 962 are compatible). 963 964config ARCH_HAS_MEM_ENCRYPT 965 bool 966 967config HAVE_SPARSE_SYSCALL_NR 968 bool 969 help 970 An architecture should select this if its syscall numbering is sparse 971 to save space. For example, MIPS architecture has a syscall array with 972 entries at 4000, 5000 and 6000 locations. This option turns on syscall 973 related optimizations for a given architecture. 974 975config ARCH_HAS_VDSO_DATA 976 bool 977 978source "kernel/gcov/Kconfig" 979 980source "scripts/gcc-plugins/Kconfig" 981 982endmenu 983