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 CC_HAS_STACKPROTECTOR_NONE 485 def_bool $(cc-option,-fno-stack-protector) 486 487config STACKPROTECTOR 488 bool "Stack Protector buffer overflow detection" 489 depends on HAVE_STACKPROTECTOR 490 depends on $(cc-option,-fstack-protector) 491 default y 492 help 493 This option turns on the "stack-protector" GCC feature. This 494 feature puts, at the beginning of functions, a canary value on 495 the stack just before the return address, and validates 496 the value just before actually returning. Stack based buffer 497 overflows (that need to overwrite this return address) now also 498 overwrite the canary, which gets detected and the attack is then 499 neutralized via a kernel panic. 500 501 Functions will have the stack-protector canary logic added if they 502 have an 8-byte or larger character array on the stack. 503 504 This feature requires gcc version 4.2 or above, or a distribution 505 gcc with the feature backported ("-fstack-protector"). 506 507 On an x86 "defconfig" build, this feature adds canary checks to 508 about 3% of all kernel functions, which increases kernel code size 509 by about 0.3%. 510 511config STACKPROTECTOR_STRONG 512 bool "Strong Stack Protector" 513 depends on STACKPROTECTOR 514 depends on $(cc-option,-fstack-protector-strong) 515 default y 516 help 517 Functions will have the stack-protector canary logic added in any 518 of the following conditions: 519 520 - local variable's address used as part of the right hand side of an 521 assignment or function argument 522 - local variable is an array (or union containing an array), 523 regardless of array type or length 524 - uses register local variables 525 526 This feature requires gcc version 4.9 or above, or a distribution 527 gcc with the feature backported ("-fstack-protector-strong"). 528 529 On an x86 "defconfig" build, this feature adds canary checks to 530 about 20% of all kernel functions, which increases the kernel code 531 size by about 2%. 532 533config ARCH_SUPPORTS_SHADOW_CALL_STACK 534 bool 535 help 536 An architecture should select this if it supports Clang's Shadow 537 Call Stack and implements runtime support for shadow stack 538 switching. 539 540config SHADOW_CALL_STACK 541 bool "Clang Shadow Call Stack" 542 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 543 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 544 help 545 This option enables Clang's Shadow Call Stack, which uses a 546 shadow stack to protect function return addresses from being 547 overwritten by an attacker. More information can be found in 548 Clang's documentation: 549 550 https://clang.llvm.org/docs/ShadowCallStack.html 551 552 Note that security guarantees in the kernel differ from the 553 ones documented for user space. The kernel must store addresses 554 of shadow stacks in memory, which means an attacker capable of 555 reading and writing arbitrary memory may be able to locate them 556 and hijack control flow by modifying the stacks. 557 558config HAVE_ARCH_WITHIN_STACK_FRAMES 559 bool 560 help 561 An architecture should select this if it can walk the kernel stack 562 frames to determine if an object is part of either the arguments 563 or local variables (i.e. that it excludes saved return addresses, 564 and similar) by implementing an inline arch_within_stack_frames(), 565 which is used by CONFIG_HARDENED_USERCOPY. 566 567config HAVE_CONTEXT_TRACKING 568 bool 569 help 570 Provide kernel/user boundaries probes necessary for subsystems 571 that need it, such as userspace RCU extended quiescent state. 572 Syscalls need to be wrapped inside user_exit()-user_enter(), either 573 optimized behind static key or through the slow path using TIF_NOHZ 574 flag. Exceptions handlers must be wrapped as well. Irqs are already 575 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 576 handling on irq exit still need to be protected. 577 578config HAVE_TIF_NOHZ 579 bool 580 help 581 Arch relies on TIF_NOHZ and syscall slow path to implement context 582 tracking calls to user_enter()/user_exit(). 583 584config HAVE_VIRT_CPU_ACCOUNTING 585 bool 586 587config ARCH_HAS_SCALED_CPUTIME 588 bool 589 590config HAVE_VIRT_CPU_ACCOUNTING_GEN 591 bool 592 default y if 64BIT 593 help 594 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 595 Before enabling this option, arch code must be audited 596 to ensure there are no races in concurrent read/write of 597 cputime_t. For example, reading/writing 64-bit cputime_t on 598 some 32-bit arches may require multiple accesses, so proper 599 locking is needed to protect against concurrent accesses. 600 601 602config HAVE_IRQ_TIME_ACCOUNTING 603 bool 604 help 605 Archs need to ensure they use a high enough resolution clock to 606 support irq time accounting and then call enable_sched_clock_irqtime(). 607 608config HAVE_MOVE_PMD 609 bool 610 help 611 Archs that select this are able to move page tables at the PMD level. 612 613config HAVE_ARCH_TRANSPARENT_HUGEPAGE 614 bool 615 616config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 617 bool 618 619config HAVE_ARCH_HUGE_VMAP 620 bool 621 622config ARCH_WANT_HUGE_PMD_SHARE 623 bool 624 625config HAVE_ARCH_SOFT_DIRTY 626 bool 627 628config HAVE_MOD_ARCH_SPECIFIC 629 bool 630 help 631 The arch uses struct mod_arch_specific to store data. Many arches 632 just need a simple module loader without arch specific data - those 633 should not enable this. 634 635config MODULES_USE_ELF_RELA 636 bool 637 help 638 Modules only use ELF RELA relocations. Modules with ELF REL 639 relocations will give an error. 640 641config MODULES_USE_ELF_REL 642 bool 643 help 644 Modules only use ELF REL relocations. Modules with ELF RELA 645 relocations will give an error. 646 647config HAVE_IRQ_EXIT_ON_IRQ_STACK 648 bool 649 help 650 Architecture doesn't only execute the irq handler on the irq stack 651 but also irq_exit(). This way we can process softirqs on this irq 652 stack instead of switching to a new one when we call __do_softirq() 653 in the end of an hardirq. 654 This spares a stack switch and improves cache usage on softirq 655 processing. 656 657config PGTABLE_LEVELS 658 int 659 default 2 660 661config ARCH_HAS_ELF_RANDOMIZE 662 bool 663 help 664 An architecture supports choosing randomized locations for 665 stack, mmap, brk, and ET_DYN. Defined functions: 666 - arch_mmap_rnd() 667 - arch_randomize_brk() 668 669config HAVE_ARCH_MMAP_RND_BITS 670 bool 671 help 672 An arch should select this symbol if it supports setting a variable 673 number of bits for use in establishing the base address for mmap 674 allocations, has MMU enabled and provides values for both: 675 - ARCH_MMAP_RND_BITS_MIN 676 - ARCH_MMAP_RND_BITS_MAX 677 678config HAVE_EXIT_THREAD 679 bool 680 help 681 An architecture implements exit_thread. 682 683config ARCH_MMAP_RND_BITS_MIN 684 int 685 686config ARCH_MMAP_RND_BITS_MAX 687 int 688 689config ARCH_MMAP_RND_BITS_DEFAULT 690 int 691 692config ARCH_MMAP_RND_BITS 693 int "Number of bits to use for ASLR of mmap base address" if EXPERT 694 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 695 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 696 default ARCH_MMAP_RND_BITS_MIN 697 depends on HAVE_ARCH_MMAP_RND_BITS 698 help 699 This value can be used to select the number of bits to use to 700 determine the random offset to the base address of vma regions 701 resulting from mmap allocations. This value will be bounded 702 by the architecture's minimum and maximum supported values. 703 704 This value can be changed after boot using the 705 /proc/sys/vm/mmap_rnd_bits tunable 706 707config HAVE_ARCH_MMAP_RND_COMPAT_BITS 708 bool 709 help 710 An arch should select this symbol if it supports running applications 711 in compatibility mode, supports setting a variable number of bits for 712 use in establishing the base address for mmap allocations, has MMU 713 enabled and provides values for both: 714 - ARCH_MMAP_RND_COMPAT_BITS_MIN 715 - ARCH_MMAP_RND_COMPAT_BITS_MAX 716 717config ARCH_MMAP_RND_COMPAT_BITS_MIN 718 int 719 720config ARCH_MMAP_RND_COMPAT_BITS_MAX 721 int 722 723config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 724 int 725 726config ARCH_MMAP_RND_COMPAT_BITS 727 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 728 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 729 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 730 default ARCH_MMAP_RND_COMPAT_BITS_MIN 731 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 732 help 733 This value can be used to select the number of bits to use to 734 determine the random offset to the base address of vma regions 735 resulting from mmap allocations for compatible applications This 736 value will be bounded by the architecture's minimum and maximum 737 supported values. 738 739 This value can be changed after boot using the 740 /proc/sys/vm/mmap_rnd_compat_bits tunable 741 742config HAVE_ARCH_COMPAT_MMAP_BASES 743 bool 744 help 745 This allows 64bit applications to invoke 32-bit mmap() syscall 746 and vice-versa 32-bit applications to call 64-bit mmap(). 747 Required for applications doing different bitness syscalls. 748 749# This allows to use a set of generic functions to determine mmap base 750# address by giving priority to top-down scheme only if the process 751# is not in legacy mode (compat task, unlimited stack size or 752# sysctl_legacy_va_layout). 753# Architecture that selects this option can provide its own version of: 754# - STACK_RND_MASK 755config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 756 bool 757 depends on MMU 758 select ARCH_HAS_ELF_RANDOMIZE 759 760config HAVE_STACK_VALIDATION 761 bool 762 help 763 Architecture supports the 'objtool check' host tool command, which 764 performs compile-time stack metadata validation. 765 766config HAVE_RELIABLE_STACKTRACE 767 bool 768 help 769 Architecture has either save_stack_trace_tsk_reliable() or 770 arch_stack_walk_reliable() function which only returns a stack trace 771 if it can guarantee the trace is reliable. 772 773config HAVE_ARCH_HASH 774 bool 775 default n 776 help 777 If this is set, the architecture provides an <asm/hash.h> 778 file which provides platform-specific implementations of some 779 functions in <linux/hash.h> or fs/namei.c. 780 781config HAVE_ARCH_NVRAM_OPS 782 bool 783 784config ISA_BUS_API 785 def_bool ISA 786 787# 788# ABI hall of shame 789# 790config CLONE_BACKWARDS 791 bool 792 help 793 Architecture has tls passed as the 4th argument of clone(2), 794 not the 5th one. 795 796config CLONE_BACKWARDS2 797 bool 798 help 799 Architecture has the first two arguments of clone(2) swapped. 800 801config CLONE_BACKWARDS3 802 bool 803 help 804 Architecture has tls passed as the 3rd argument of clone(2), 805 not the 5th one. 806 807config ODD_RT_SIGACTION 808 bool 809 help 810 Architecture has unusual rt_sigaction(2) arguments 811 812config OLD_SIGSUSPEND 813 bool 814 help 815 Architecture has old sigsuspend(2) syscall, of one-argument variety 816 817config OLD_SIGSUSPEND3 818 bool 819 help 820 Even weirder antique ABI - three-argument sigsuspend(2) 821 822config OLD_SIGACTION 823 bool 824 help 825 Architecture has old sigaction(2) syscall. Nope, not the same 826 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 827 but fairly different variant of sigaction(2), thanks to OSF/1 828 compatibility... 829 830config COMPAT_OLD_SIGACTION 831 bool 832 833config COMPAT_32BIT_TIME 834 bool "Provide system calls for 32-bit time_t" 835 default !64BIT || COMPAT 836 help 837 This enables 32 bit time_t support in addition to 64 bit time_t support. 838 This is relevant on all 32-bit architectures, and 64-bit architectures 839 as part of compat syscall handling. 840 841config ARCH_NO_PREEMPT 842 bool 843 844config ARCH_SUPPORTS_RT 845 bool 846 847config CPU_NO_EFFICIENT_FFS 848 def_bool n 849 850config HAVE_ARCH_VMAP_STACK 851 def_bool n 852 help 853 An arch should select this symbol if it can support kernel stacks 854 in vmalloc space. This means: 855 856 - vmalloc space must be large enough to hold many kernel stacks. 857 This may rule out many 32-bit architectures. 858 859 - Stacks in vmalloc space need to work reliably. For example, if 860 vmap page tables are created on demand, either this mechanism 861 needs to work while the stack points to a virtual address with 862 unpopulated page tables or arch code (switch_to() and switch_mm(), 863 most likely) needs to ensure that the stack's page table entries 864 are populated before running on a possibly unpopulated stack. 865 866 - If the stack overflows into a guard page, something reasonable 867 should happen. The definition of "reasonable" is flexible, but 868 instantly rebooting without logging anything would be unfriendly. 869 870config VMAP_STACK 871 default y 872 bool "Use a virtually-mapped stack" 873 depends on HAVE_ARCH_VMAP_STACK 874 depends on !KASAN || KASAN_VMALLOC 875 help 876 Enable this if you want the use virtually-mapped kernel stacks 877 with guard pages. This causes kernel stack overflows to be 878 caught immediately rather than causing difficult-to-diagnose 879 corruption. 880 881 To use this with KASAN, the architecture must support backing 882 virtual mappings with real shadow memory, and KASAN_VMALLOC must 883 be enabled. 884 885config ARCH_OPTIONAL_KERNEL_RWX 886 def_bool n 887 888config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 889 def_bool n 890 891config ARCH_HAS_STRICT_KERNEL_RWX 892 def_bool n 893 894config STRICT_KERNEL_RWX 895 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 896 depends on ARCH_HAS_STRICT_KERNEL_RWX 897 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 898 help 899 If this is set, kernel text and rodata memory will be made read-only, 900 and non-text memory will be made non-executable. This provides 901 protection against certain security exploits (e.g. executing the heap 902 or modifying text) 903 904 These features are considered standard security practice these days. 905 You should say Y here in almost all cases. 906 907config ARCH_HAS_STRICT_MODULE_RWX 908 def_bool n 909 910config STRICT_MODULE_RWX 911 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 912 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 913 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 914 help 915 If this is set, module text and rodata memory will be made read-only, 916 and non-text memory will be made non-executable. This provides 917 protection against certain security exploits (e.g. writing to text) 918 919# select if the architecture provides an asm/dma-direct.h header 920config ARCH_HAS_PHYS_TO_DMA 921 bool 922 923config HAVE_ARCH_COMPILER_H 924 bool 925 help 926 An architecture can select this if it provides an 927 asm/compiler.h header that should be included after 928 linux/compiler-*.h in order to override macro definitions that those 929 headers generally provide. 930 931config HAVE_ARCH_PREL32_RELOCATIONS 932 bool 933 help 934 May be selected by an architecture if it supports place-relative 935 32-bit relocations, both in the toolchain and in the module loader, 936 in which case relative references can be used in special sections 937 for PCI fixup, initcalls etc which are only half the size on 64 bit 938 architectures, and don't require runtime relocation on relocatable 939 kernels. 940 941config ARCH_USE_MEMREMAP_PROT 942 bool 943 944config LOCK_EVENT_COUNTS 945 bool "Locking event counts collection" 946 depends on DEBUG_FS 947 help 948 Enable light-weight counting of various locking related events 949 in the system with minimal performance impact. This reduces 950 the chance of application behavior change because of timing 951 differences. The counts are reported via debugfs. 952 953# Select if the architecture has support for applying RELR relocations. 954config ARCH_HAS_RELR 955 bool 956 957config RELR 958 bool "Use RELR relocation packing" 959 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 960 default y 961 help 962 Store the kernel's dynamic relocations in the RELR relocation packing 963 format. Requires a compatible linker (LLD supports this feature), as 964 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 965 are compatible). 966 967config ARCH_HAS_MEM_ENCRYPT 968 bool 969 970config HAVE_SPARSE_SYSCALL_NR 971 bool 972 help 973 An architecture should select this if its syscall numbering is sparse 974 to save space. For example, MIPS architecture has a syscall array with 975 entries at 4000, 5000 and 6000 locations. This option turns on syscall 976 related optimizations for a given architecture. 977 978source "kernel/gcov/Kconfig" 979 980source "scripts/gcc-plugins/Kconfig" 981 982endmenu 983