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 OPROFILE 31 tristate "OProfile system profiling" 32 depends on PROFILING 33 depends on HAVE_OPROFILE 34 select RING_BUFFER 35 select RING_BUFFER_ALLOW_SWAP 36 help 37 OProfile is a profiling system capable of profiling the 38 whole system, include the kernel, kernel modules, libraries, 39 and applications. 40 41 If unsure, say N. 42 43config OPROFILE_EVENT_MULTIPLEX 44 bool "OProfile multiplexing support (EXPERIMENTAL)" 45 default n 46 depends on OPROFILE && X86 47 help 48 The number of hardware counters is limited. The multiplexing 49 feature enables OProfile to gather more events than counters 50 are provided by the hardware. This is realized by switching 51 between events at a user specified time interval. 52 53 If unsure, say N. 54 55config HAVE_OPROFILE 56 bool 57 58config OPROFILE_NMI_TIMER 59 def_bool y 60 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 61 62config KPROBES 63 bool "Kprobes" 64 depends on MODULES 65 depends on HAVE_KPROBES 66 select KALLSYMS 67 help 68 Kprobes allows you to trap at almost any kernel address and 69 execute a callback function. register_kprobe() establishes 70 a probepoint and specifies the callback. Kprobes is useful 71 for kernel debugging, non-intrusive instrumentation and testing. 72 If in doubt, say "N". 73 74config JUMP_LABEL 75 bool "Optimize very unlikely/likely branches" 76 depends on HAVE_ARCH_JUMP_LABEL 77 depends on CC_HAS_ASM_GOTO 78 help 79 This option enables a transparent branch optimization that 80 makes certain almost-always-true or almost-always-false branch 81 conditions even cheaper to execute within the kernel. 82 83 Certain performance-sensitive kernel code, such as trace points, 84 scheduler functionality, networking code and KVM have such 85 branches and include support for this optimization technique. 86 87 If it is detected that the compiler has support for "asm goto", 88 the kernel will compile such branches with just a nop 89 instruction. When the condition flag is toggled to true, the 90 nop will be converted to a jump instruction to execute the 91 conditional block of instructions. 92 93 This technique lowers overhead and stress on the branch prediction 94 of the processor and generally makes the kernel faster. The update 95 of the condition is slower, but those are always very rare. 96 97 ( On 32-bit x86, the necessary options added to the compiler 98 flags may increase the size of the kernel slightly. ) 99 100config STATIC_KEYS_SELFTEST 101 bool "Static key selftest" 102 depends on JUMP_LABEL 103 help 104 Boot time self-test of the branch patching code. 105 106config OPTPROBES 107 def_bool y 108 depends on KPROBES && HAVE_OPTPROBES 109 select TASKS_RCU if PREEMPTION 110 111config KPROBES_ON_FTRACE 112 def_bool y 113 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 114 depends on DYNAMIC_FTRACE_WITH_REGS 115 help 116 If function tracer is enabled and the arch supports full 117 passing of pt_regs to function tracing, then kprobes can 118 optimize on top of function tracing. 119 120config UPROBES 121 def_bool n 122 depends on ARCH_SUPPORTS_UPROBES 123 help 124 Uprobes is the user-space counterpart to kprobes: they 125 enable instrumentation applications (such as 'perf probe') 126 to establish unintrusive probes in user-space binaries and 127 libraries, by executing handler functions when the probes 128 are hit by user-space applications. 129 130 ( These probes come in the form of single-byte breakpoints, 131 managed by the kernel and kept transparent to the probed 132 application. ) 133 134config HAVE_EFFICIENT_UNALIGNED_ACCESS 135 bool 136 help 137 Some architectures are unable to perform unaligned accesses 138 without the use of get_unaligned/put_unaligned. Others are 139 unable to perform such accesses efficiently (e.g. trap on 140 unaligned access and require fixing it up in the exception 141 handler.) 142 143 This symbol should be selected by an architecture if it can 144 perform unaligned accesses efficiently to allow different 145 code paths to be selected for these cases. Some network 146 drivers, for example, could opt to not fix up alignment 147 problems with received packets if doing so would not help 148 much. 149 150 See Documentation/core-api/unaligned-memory-access.rst for more 151 information on the topic of unaligned memory accesses. 152 153config ARCH_USE_BUILTIN_BSWAP 154 bool 155 help 156 Modern versions of GCC (since 4.4) have builtin functions 157 for handling byte-swapping. Using these, instead of the old 158 inline assembler that the architecture code provides in the 159 __arch_bswapXX() macros, allows the compiler to see what's 160 happening and offers more opportunity for optimisation. In 161 particular, the compiler will be able to combine the byteswap 162 with a nearby load or store and use load-and-swap or 163 store-and-swap instructions if the architecture has them. It 164 should almost *never* result in code which is worse than the 165 hand-coded assembler in <asm/swab.h>. But just in case it 166 does, the use of the builtins is optional. 167 168 Any architecture with load-and-swap or store-and-swap 169 instructions should set this. And it shouldn't hurt to set it 170 on architectures that don't have such instructions. 171 172config KRETPROBES 173 def_bool y 174 depends on KPROBES && HAVE_KRETPROBES 175 176config USER_RETURN_NOTIFIER 177 bool 178 depends on HAVE_USER_RETURN_NOTIFIER 179 help 180 Provide a kernel-internal notification when a cpu is about to 181 switch to user mode. 182 183config HAVE_IOREMAP_PROT 184 bool 185 186config HAVE_KPROBES 187 bool 188 189config HAVE_KRETPROBES 190 bool 191 192config HAVE_OPTPROBES 193 bool 194 195config HAVE_KPROBES_ON_FTRACE 196 bool 197 198config HAVE_FUNCTION_ERROR_INJECTION 199 bool 200 201config HAVE_NMI 202 bool 203 204# 205# An arch should select this if it provides all these things: 206# 207# task_pt_regs() in asm/processor.h or asm/ptrace.h 208# arch_has_single_step() if there is hardware single-step support 209# arch_has_block_step() if there is hardware block-step support 210# asm/syscall.h supplying asm-generic/syscall.h interface 211# linux/regset.h user_regset interfaces 212# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 213# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 214# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 215# signal delivery calls tracehook_signal_handler() 216# 217config HAVE_ARCH_TRACEHOOK 218 bool 219 220config HAVE_DMA_CONTIGUOUS 221 bool 222 223config GENERIC_SMP_IDLE_THREAD 224 bool 225 226config GENERIC_IDLE_POLL_SETUP 227 bool 228 229config ARCH_HAS_FORTIFY_SOURCE 230 bool 231 help 232 An architecture should select this when it can successfully 233 build and run with CONFIG_FORTIFY_SOURCE. 234 235# 236# Select if the arch provides a historic keepinit alias for the retain_initrd 237# command line option 238# 239config ARCH_HAS_KEEPINITRD 240 bool 241 242# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 243config ARCH_HAS_SET_MEMORY 244 bool 245 246# Select if arch has all set_direct_map_invalid/default() functions 247config ARCH_HAS_SET_DIRECT_MAP 248 bool 249 250# 251# Select if the architecture provides the arch_dma_set_uncached symbol to 252# either provide an uncached segement alias for a DMA allocation, or 253# to remap the page tables in place. 254# 255config ARCH_HAS_DMA_SET_UNCACHED 256 bool 257 258# 259# Select if the architectures provides the arch_dma_clear_uncached symbol 260# to undo an in-place page table remap for uncached access. 261# 262config ARCH_HAS_DMA_CLEAR_UNCACHED 263 bool 264 265# Select if arch init_task must go in the __init_task_data section 266config ARCH_TASK_STRUCT_ON_STACK 267 bool 268 269# Select if arch has its private alloc_task_struct() function 270config ARCH_TASK_STRUCT_ALLOCATOR 271 bool 272 273config HAVE_ARCH_THREAD_STRUCT_WHITELIST 274 bool 275 depends on !ARCH_TASK_STRUCT_ALLOCATOR 276 help 277 An architecture should select this to provide hardened usercopy 278 knowledge about what region of the thread_struct should be 279 whitelisted for copying to userspace. Normally this is only the 280 FPU registers. Specifically, arch_thread_struct_whitelist() 281 should be implemented. Without this, the entire thread_struct 282 field in task_struct will be left whitelisted. 283 284# Select if arch has its private alloc_thread_stack() function 285config ARCH_THREAD_STACK_ALLOCATOR 286 bool 287 288# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 289config ARCH_WANTS_DYNAMIC_TASK_STRUCT 290 bool 291 292config ARCH_32BIT_OFF_T 293 bool 294 depends on !64BIT 295 help 296 All new 32-bit architectures should have 64-bit off_t type on 297 userspace side which corresponds to the loff_t kernel type. This 298 is the requirement for modern ABIs. Some existing architectures 299 still support 32-bit off_t. This option is enabled for all such 300 architectures explicitly. 301 302config HAVE_ASM_MODVERSIONS 303 bool 304 help 305 This symbol should be selected by an architecure if it provides 306 <asm/asm-prototypes.h> to support the module versioning for symbols 307 exported from assembly code. 308 309config HAVE_REGS_AND_STACK_ACCESS_API 310 bool 311 help 312 This symbol should be selected by an architecure if it supports 313 the API needed to access registers and stack entries from pt_regs, 314 declared in asm/ptrace.h 315 For example the kprobes-based event tracer needs this API. 316 317config HAVE_RSEQ 318 bool 319 depends on HAVE_REGS_AND_STACK_ACCESS_API 320 help 321 This symbol should be selected by an architecture if it 322 supports an implementation of restartable sequences. 323 324config HAVE_FUNCTION_ARG_ACCESS_API 325 bool 326 help 327 This symbol should be selected by an architecure if it supports 328 the API needed to access function arguments from pt_regs, 329 declared in asm/ptrace.h 330 331config HAVE_HW_BREAKPOINT 332 bool 333 depends on PERF_EVENTS 334 335config HAVE_MIXED_BREAKPOINTS_REGS 336 bool 337 depends on HAVE_HW_BREAKPOINT 338 help 339 Depending on the arch implementation of hardware breakpoints, 340 some of them have separate registers for data and instruction 341 breakpoints addresses, others have mixed registers to store 342 them but define the access type in a control register. 343 Select this option if your arch implements breakpoints under the 344 latter fashion. 345 346config HAVE_USER_RETURN_NOTIFIER 347 bool 348 349config HAVE_PERF_EVENTS_NMI 350 bool 351 help 352 System hardware can generate an NMI using the perf event 353 subsystem. Also has support for calculating CPU cycle events 354 to determine how many clock cycles in a given period. 355 356config HAVE_HARDLOCKUP_DETECTOR_PERF 357 bool 358 depends on HAVE_PERF_EVENTS_NMI 359 help 360 The arch chooses to use the generic perf-NMI-based hardlockup 361 detector. Must define HAVE_PERF_EVENTS_NMI. 362 363config HAVE_NMI_WATCHDOG 364 depends on HAVE_NMI 365 bool 366 help 367 The arch provides a low level NMI watchdog. It provides 368 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 369 370config HAVE_HARDLOCKUP_DETECTOR_ARCH 371 bool 372 select HAVE_NMI_WATCHDOG 373 help 374 The arch chooses to provide its own hardlockup detector, which is 375 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 376 interfaces and parameters provided by hardlockup detector subsystem. 377 378config HAVE_PERF_REGS 379 bool 380 help 381 Support selective register dumps for perf events. This includes 382 bit-mapping of each registers and a unique architecture id. 383 384config HAVE_PERF_USER_STACK_DUMP 385 bool 386 help 387 Support user stack dumps for perf event samples. This needs 388 access to the user stack pointer which is not unified across 389 architectures. 390 391config HAVE_ARCH_JUMP_LABEL 392 bool 393 394config HAVE_ARCH_JUMP_LABEL_RELATIVE 395 bool 396 397config MMU_GATHER_TABLE_FREE 398 bool 399 400config MMU_GATHER_RCU_TABLE_FREE 401 bool 402 select MMU_GATHER_TABLE_FREE 403 404config MMU_GATHER_PAGE_SIZE 405 bool 406 407config MMU_GATHER_NO_RANGE 408 bool 409 410config MMU_GATHER_NO_GATHER 411 bool 412 depends on MMU_GATHER_TABLE_FREE 413 414config ARCH_HAVE_NMI_SAFE_CMPXCHG 415 bool 416 417config HAVE_ALIGNED_STRUCT_PAGE 418 bool 419 help 420 This makes sure that struct pages are double word aligned and that 421 e.g. the SLUB allocator can perform double word atomic operations 422 on a struct page for better performance. However selecting this 423 might increase the size of a struct page by a word. 424 425config HAVE_CMPXCHG_LOCAL 426 bool 427 428config HAVE_CMPXCHG_DOUBLE 429 bool 430 431config ARCH_WEAK_RELEASE_ACQUIRE 432 bool 433 434config ARCH_WANT_IPC_PARSE_VERSION 435 bool 436 437config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 438 bool 439 440config ARCH_WANT_OLD_COMPAT_IPC 441 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 442 bool 443 444config HAVE_ARCH_SECCOMP_FILTER 445 bool 446 help 447 An arch should select this symbol if it provides all of these things: 448 - syscall_get_arch() 449 - syscall_get_arguments() 450 - syscall_rollback() 451 - syscall_set_return_value() 452 - SIGSYS siginfo_t support 453 - secure_computing is called from a ptrace_event()-safe context 454 - secure_computing return value is checked and a return value of -1 455 results in the system call being skipped immediately. 456 - seccomp syscall wired up 457 458config SECCOMP_FILTER 459 def_bool y 460 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 461 help 462 Enable tasks to build secure computing environments defined 463 in terms of Berkeley Packet Filter programs which implement 464 task-defined system call filtering polices. 465 466 See Documentation/userspace-api/seccomp_filter.rst for details. 467 468config HAVE_ARCH_STACKLEAK 469 bool 470 help 471 An architecture should select this if it has the code which 472 fills the used part of the kernel stack with the STACKLEAK_POISON 473 value before returning from system calls. 474 475config HAVE_STACKPROTECTOR 476 bool 477 help 478 An arch should select this symbol if: 479 - it has implemented a stack canary (e.g. __stack_chk_guard) 480 481config CC_HAS_STACKPROTECTOR_NONE 482 def_bool $(cc-option,-fno-stack-protector) 483 484config STACKPROTECTOR 485 bool "Stack Protector buffer overflow detection" 486 depends on HAVE_STACKPROTECTOR 487 depends on $(cc-option,-fstack-protector) 488 default y 489 help 490 This option turns on the "stack-protector" GCC feature. This 491 feature puts, at the beginning of functions, a canary value on 492 the stack just before the return address, and validates 493 the value just before actually returning. Stack based buffer 494 overflows (that need to overwrite this return address) now also 495 overwrite the canary, which gets detected and the attack is then 496 neutralized via a kernel panic. 497 498 Functions will have the stack-protector canary logic added if they 499 have an 8-byte or larger character array on the stack. 500 501 This feature requires gcc version 4.2 or above, or a distribution 502 gcc with the feature backported ("-fstack-protector"). 503 504 On an x86 "defconfig" build, this feature adds canary checks to 505 about 3% of all kernel functions, which increases kernel code size 506 by about 0.3%. 507 508config STACKPROTECTOR_STRONG 509 bool "Strong Stack Protector" 510 depends on STACKPROTECTOR 511 depends on $(cc-option,-fstack-protector-strong) 512 default y 513 help 514 Functions will have the stack-protector canary logic added in any 515 of the following conditions: 516 517 - local variable's address used as part of the right hand side of an 518 assignment or function argument 519 - local variable is an array (or union containing an array), 520 regardless of array type or length 521 - uses register local variables 522 523 This feature requires gcc version 4.9 or above, or a distribution 524 gcc with the feature backported ("-fstack-protector-strong"). 525 526 On an x86 "defconfig" build, this feature adds canary checks to 527 about 20% of all kernel functions, which increases the kernel code 528 size by about 2%. 529 530config 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_COPY_THREAD_TLS 758 bool 759 help 760 Architecture provides copy_thread_tls to accept tls argument via 761 normal C parameter passing, rather than extracting the syscall 762 argument from pt_regs. 763 764config HAVE_STACK_VALIDATION 765 bool 766 help 767 Architecture supports the 'objtool check' host tool command, which 768 performs compile-time stack metadata validation. 769 770config HAVE_RELIABLE_STACKTRACE 771 bool 772 help 773 Architecture has either save_stack_trace_tsk_reliable() or 774 arch_stack_walk_reliable() function which only returns a stack trace 775 if it can guarantee the trace is reliable. 776 777config HAVE_ARCH_HASH 778 bool 779 default n 780 help 781 If this is set, the architecture provides an <asm/hash.h> 782 file which provides platform-specific implementations of some 783 functions in <linux/hash.h> or fs/namei.c. 784 785config HAVE_ARCH_NVRAM_OPS 786 bool 787 788config ISA_BUS_API 789 def_bool ISA 790 791# 792# ABI hall of shame 793# 794config CLONE_BACKWARDS 795 bool 796 help 797 Architecture has tls passed as the 4th argument of clone(2), 798 not the 5th one. 799 800config CLONE_BACKWARDS2 801 bool 802 help 803 Architecture has the first two arguments of clone(2) swapped. 804 805config CLONE_BACKWARDS3 806 bool 807 help 808 Architecture has tls passed as the 3rd argument of clone(2), 809 not the 5th one. 810 811config ODD_RT_SIGACTION 812 bool 813 help 814 Architecture has unusual rt_sigaction(2) arguments 815 816config OLD_SIGSUSPEND 817 bool 818 help 819 Architecture has old sigsuspend(2) syscall, of one-argument variety 820 821config OLD_SIGSUSPEND3 822 bool 823 help 824 Even weirder antique ABI - three-argument sigsuspend(2) 825 826config OLD_SIGACTION 827 bool 828 help 829 Architecture has old sigaction(2) syscall. Nope, not the same 830 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 831 but fairly different variant of sigaction(2), thanks to OSF/1 832 compatibility... 833 834config COMPAT_OLD_SIGACTION 835 bool 836 837config COMPAT_32BIT_TIME 838 bool "Provide system calls for 32-bit time_t" 839 default !64BIT || COMPAT 840 help 841 This enables 32 bit time_t support in addition to 64 bit time_t support. 842 This is relevant on all 32-bit architectures, and 64-bit architectures 843 as part of compat syscall handling. 844 845config ARCH_NO_PREEMPT 846 bool 847 848config ARCH_SUPPORTS_RT 849 bool 850 851config CPU_NO_EFFICIENT_FFS 852 def_bool n 853 854config HAVE_ARCH_VMAP_STACK 855 def_bool n 856 help 857 An arch should select this symbol if it can support kernel stacks 858 in vmalloc space. This means: 859 860 - vmalloc space must be large enough to hold many kernel stacks. 861 This may rule out many 32-bit architectures. 862 863 - Stacks in vmalloc space need to work reliably. For example, if 864 vmap page tables are created on demand, either this mechanism 865 needs to work while the stack points to a virtual address with 866 unpopulated page tables or arch code (switch_to() and switch_mm(), 867 most likely) needs to ensure that the stack's page table entries 868 are populated before running on a possibly unpopulated stack. 869 870 - If the stack overflows into a guard page, something reasonable 871 should happen. The definition of "reasonable" is flexible, but 872 instantly rebooting without logging anything would be unfriendly. 873 874config VMAP_STACK 875 default y 876 bool "Use a virtually-mapped stack" 877 depends on HAVE_ARCH_VMAP_STACK 878 depends on !KASAN || KASAN_VMALLOC 879 help 880 Enable this if you want the use virtually-mapped kernel stacks 881 with guard pages. This causes kernel stack overflows to be 882 caught immediately rather than causing difficult-to-diagnose 883 corruption. 884 885 To use this with KASAN, the architecture must support backing 886 virtual mappings with real shadow memory, and KASAN_VMALLOC must 887 be enabled. 888 889config ARCH_OPTIONAL_KERNEL_RWX 890 def_bool n 891 892config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 893 def_bool n 894 895config ARCH_HAS_STRICT_KERNEL_RWX 896 def_bool n 897 898config STRICT_KERNEL_RWX 899 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 900 depends on ARCH_HAS_STRICT_KERNEL_RWX 901 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 902 help 903 If this is set, kernel text and rodata memory will be made read-only, 904 and non-text memory will be made non-executable. This provides 905 protection against certain security exploits (e.g. executing the heap 906 or modifying text) 907 908 These features are considered standard security practice these days. 909 You should say Y here in almost all cases. 910 911config ARCH_HAS_STRICT_MODULE_RWX 912 def_bool n 913 914config STRICT_MODULE_RWX 915 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 916 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 917 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 918 help 919 If this is set, module text and rodata memory will be made read-only, 920 and non-text memory will be made non-executable. This provides 921 protection against certain security exploits (e.g. writing to text) 922 923# select if the architecture provides an asm/dma-direct.h header 924config ARCH_HAS_PHYS_TO_DMA 925 bool 926 927config HAVE_ARCH_COMPILER_H 928 bool 929 help 930 An architecture can select this if it provides an 931 asm/compiler.h header that should be included after 932 linux/compiler-*.h in order to override macro definitions that those 933 headers generally provide. 934 935config HAVE_ARCH_PREL32_RELOCATIONS 936 bool 937 help 938 May be selected by an architecture if it supports place-relative 939 32-bit relocations, both in the toolchain and in the module loader, 940 in which case relative references can be used in special sections 941 for PCI fixup, initcalls etc which are only half the size on 64 bit 942 architectures, and don't require runtime relocation on relocatable 943 kernels. 944 945config ARCH_USE_MEMREMAP_PROT 946 bool 947 948config LOCK_EVENT_COUNTS 949 bool "Locking event counts collection" 950 depends on DEBUG_FS 951 help 952 Enable light-weight counting of various locking related events 953 in the system with minimal performance impact. This reduces 954 the chance of application behavior change because of timing 955 differences. The counts are reported via debugfs. 956 957# Select if the architecture has support for applying RELR relocations. 958config ARCH_HAS_RELR 959 bool 960 961config RELR 962 bool "Use RELR relocation packing" 963 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 964 default y 965 help 966 Store the kernel's dynamic relocations in the RELR relocation packing 967 format. Requires a compatible linker (LLD supports this feature), as 968 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 969 are compatible). 970 971config ARCH_HAS_MEM_ENCRYPT 972 bool 973 974config HAVE_SPARSE_SYSCALL_NR 975 bool 976 help 977 An architecture should select this if its syscall numbering is sparse 978 to save space. For example, MIPS architecture has a syscall array with 979 entries at 4000, 5000 and 6000 locations. This option turns on syscall 980 related optimizations for a given architecture. 981 982source "kernel/gcov/Kconfig" 983 984source "scripts/gcc-plugins/Kconfig" 985 986endmenu 987