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 SET_FS 28 bool 29 30config HOTPLUG_SMT 31 bool 32 33config GENERIC_ENTRY 34 bool 35 36config OPROFILE 37 tristate "OProfile system profiling" 38 depends on PROFILING 39 depends on HAVE_OPROFILE 40 select RING_BUFFER 41 select RING_BUFFER_ALLOW_SWAP 42 help 43 OProfile is a profiling system capable of profiling the 44 whole system, include the kernel, kernel modules, libraries, 45 and applications. 46 47 If unsure, say N. 48 49config OPROFILE_EVENT_MULTIPLEX 50 bool "OProfile multiplexing support (EXPERIMENTAL)" 51 default n 52 depends on OPROFILE && X86 53 help 54 The number of hardware counters is limited. The multiplexing 55 feature enables OProfile to gather more events than counters 56 are provided by the hardware. This is realized by switching 57 between events at a user specified time interval. 58 59 If unsure, say N. 60 61config HAVE_OPROFILE 62 bool 63 64config OPROFILE_NMI_TIMER 65 def_bool y 66 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 67 68config KPROBES 69 bool "Kprobes" 70 depends on MODULES 71 depends on HAVE_KPROBES 72 select KALLSYMS 73 help 74 Kprobes allows you to trap at almost any kernel address and 75 execute a callback function. register_kprobe() establishes 76 a probepoint and specifies the callback. Kprobes is useful 77 for kernel debugging, non-intrusive instrumentation and testing. 78 If in doubt, say "N". 79 80config JUMP_LABEL 81 bool "Optimize very unlikely/likely branches" 82 depends on HAVE_ARCH_JUMP_LABEL 83 depends on CC_HAS_ASM_GOTO 84 help 85 This option enables a transparent branch optimization that 86 makes certain almost-always-true or almost-always-false branch 87 conditions even cheaper to execute within the kernel. 88 89 Certain performance-sensitive kernel code, such as trace points, 90 scheduler functionality, networking code and KVM have such 91 branches and include support for this optimization technique. 92 93 If it is detected that the compiler has support for "asm goto", 94 the kernel will compile such branches with just a nop 95 instruction. When the condition flag is toggled to true, the 96 nop will be converted to a jump instruction to execute the 97 conditional block of instructions. 98 99 This technique lowers overhead and stress on the branch prediction 100 of the processor and generally makes the kernel faster. The update 101 of the condition is slower, but those are always very rare. 102 103 ( On 32-bit x86, the necessary options added to the compiler 104 flags may increase the size of the kernel slightly. ) 105 106config STATIC_KEYS_SELFTEST 107 bool "Static key selftest" 108 depends on JUMP_LABEL 109 help 110 Boot time self-test of the branch patching code. 111 112config STATIC_CALL_SELFTEST 113 bool "Static call selftest" 114 depends on HAVE_STATIC_CALL 115 help 116 Boot time self-test of the call patching code. 117 118config OPTPROBES 119 def_bool y 120 depends on KPROBES && HAVE_OPTPROBES 121 select TASKS_RCU if PREEMPTION 122 123config KPROBES_ON_FTRACE 124 def_bool y 125 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 126 depends on DYNAMIC_FTRACE_WITH_REGS 127 help 128 If function tracer is enabled and the arch supports full 129 passing of pt_regs to function tracing, then kprobes can 130 optimize on top of function tracing. 131 132config UPROBES 133 def_bool n 134 depends on ARCH_SUPPORTS_UPROBES 135 help 136 Uprobes is the user-space counterpart to kprobes: they 137 enable instrumentation applications (such as 'perf probe') 138 to establish unintrusive probes in user-space binaries and 139 libraries, by executing handler functions when the probes 140 are hit by user-space applications. 141 142 ( These probes come in the form of single-byte breakpoints, 143 managed by the kernel and kept transparent to the probed 144 application. ) 145 146config HAVE_EFFICIENT_UNALIGNED_ACCESS 147 bool 148 help 149 Some architectures are unable to perform unaligned accesses 150 without the use of get_unaligned/put_unaligned. Others are 151 unable to perform such accesses efficiently (e.g. trap on 152 unaligned access and require fixing it up in the exception 153 handler.) 154 155 This symbol should be selected by an architecture if it can 156 perform unaligned accesses efficiently to allow different 157 code paths to be selected for these cases. Some network 158 drivers, for example, could opt to not fix up alignment 159 problems with received packets if doing so would not help 160 much. 161 162 See Documentation/core-api/unaligned-memory-access.rst for more 163 information on the topic of unaligned memory accesses. 164 165config ARCH_USE_BUILTIN_BSWAP 166 bool 167 help 168 Modern versions of GCC (since 4.4) have builtin functions 169 for handling byte-swapping. Using these, instead of the old 170 inline assembler that the architecture code provides in the 171 __arch_bswapXX() macros, allows the compiler to see what's 172 happening and offers more opportunity for optimisation. In 173 particular, the compiler will be able to combine the byteswap 174 with a nearby load or store and use load-and-swap or 175 store-and-swap instructions if the architecture has them. It 176 should almost *never* result in code which is worse than the 177 hand-coded assembler in <asm/swab.h>. But just in case it 178 does, the use of the builtins is optional. 179 180 Any architecture with load-and-swap or store-and-swap 181 instructions should set this. And it shouldn't hurt to set it 182 on architectures that don't have such instructions. 183 184config KRETPROBES 185 def_bool y 186 depends on KPROBES && HAVE_KRETPROBES 187 188config USER_RETURN_NOTIFIER 189 bool 190 depends on HAVE_USER_RETURN_NOTIFIER 191 help 192 Provide a kernel-internal notification when a cpu is about to 193 switch to user mode. 194 195config HAVE_IOREMAP_PROT 196 bool 197 198config HAVE_KPROBES 199 bool 200 201config HAVE_KRETPROBES 202 bool 203 204config HAVE_OPTPROBES 205 bool 206 207config HAVE_KPROBES_ON_FTRACE 208 bool 209 210config HAVE_FUNCTION_ERROR_INJECTION 211 bool 212 213config HAVE_NMI 214 bool 215 216# 217# An arch should select this if it provides all these things: 218# 219# task_pt_regs() in asm/processor.h or asm/ptrace.h 220# arch_has_single_step() if there is hardware single-step support 221# arch_has_block_step() if there is hardware block-step support 222# asm/syscall.h supplying asm-generic/syscall.h interface 223# linux/regset.h user_regset interfaces 224# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 225# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 226# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 227# signal delivery calls tracehook_signal_handler() 228# 229config HAVE_ARCH_TRACEHOOK 230 bool 231 232config HAVE_DMA_CONTIGUOUS 233 bool 234 235config GENERIC_SMP_IDLE_THREAD 236 bool 237 238config GENERIC_IDLE_POLL_SETUP 239 bool 240 241config ARCH_HAS_FORTIFY_SOURCE 242 bool 243 help 244 An architecture should select this when it can successfully 245 build and run with CONFIG_FORTIFY_SOURCE. 246 247# 248# Select if the arch provides a historic keepinit alias for the retain_initrd 249# command line option 250# 251config ARCH_HAS_KEEPINITRD 252 bool 253 254# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 255config ARCH_HAS_SET_MEMORY 256 bool 257 258# Select if arch has all set_direct_map_invalid/default() functions 259config ARCH_HAS_SET_DIRECT_MAP 260 bool 261 262# 263# Select if the architecture provides the arch_dma_set_uncached symbol to 264# either provide an uncached segment alias for a DMA allocation, or 265# to remap the page tables in place. 266# 267config ARCH_HAS_DMA_SET_UNCACHED 268 bool 269 270# 271# Select if the architectures provides the arch_dma_clear_uncached symbol 272# to undo an in-place page table remap for uncached access. 273# 274config ARCH_HAS_DMA_CLEAR_UNCACHED 275 bool 276 277# Select if arch init_task must go in the __init_task_data section 278config ARCH_TASK_STRUCT_ON_STACK 279 bool 280 281# Select if arch has its private alloc_task_struct() function 282config ARCH_TASK_STRUCT_ALLOCATOR 283 bool 284 285config HAVE_ARCH_THREAD_STRUCT_WHITELIST 286 bool 287 depends on !ARCH_TASK_STRUCT_ALLOCATOR 288 help 289 An architecture should select this to provide hardened usercopy 290 knowledge about what region of the thread_struct should be 291 whitelisted for copying to userspace. Normally this is only the 292 FPU registers. Specifically, arch_thread_struct_whitelist() 293 should be implemented. Without this, the entire thread_struct 294 field in task_struct will be left whitelisted. 295 296# Select if arch has its private alloc_thread_stack() function 297config ARCH_THREAD_STACK_ALLOCATOR 298 bool 299 300# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 301config ARCH_WANTS_DYNAMIC_TASK_STRUCT 302 bool 303 304config ARCH_32BIT_OFF_T 305 bool 306 depends on !64BIT 307 help 308 All new 32-bit architectures should have 64-bit off_t type on 309 userspace side which corresponds to the loff_t kernel type. This 310 is the requirement for modern ABIs. Some existing architectures 311 still support 32-bit off_t. This option is enabled for all such 312 architectures explicitly. 313 314config HAVE_ASM_MODVERSIONS 315 bool 316 help 317 This symbol should be selected by an architecture if it provides 318 <asm/asm-prototypes.h> to support the module versioning for symbols 319 exported from assembly code. 320 321config HAVE_REGS_AND_STACK_ACCESS_API 322 bool 323 help 324 This symbol should be selected by an architecture if it supports 325 the API needed to access registers and stack entries from pt_regs, 326 declared in asm/ptrace.h 327 For example the kprobes-based event tracer needs this API. 328 329config HAVE_RSEQ 330 bool 331 depends on HAVE_REGS_AND_STACK_ACCESS_API 332 help 333 This symbol should be selected by an architecture if it 334 supports an implementation of restartable sequences. 335 336config HAVE_FUNCTION_ARG_ACCESS_API 337 bool 338 help 339 This symbol should be selected by an architecture if it supports 340 the API needed to access function arguments from pt_regs, 341 declared in asm/ptrace.h 342 343config HAVE_HW_BREAKPOINT 344 bool 345 depends on PERF_EVENTS 346 347config HAVE_MIXED_BREAKPOINTS_REGS 348 bool 349 depends on HAVE_HW_BREAKPOINT 350 help 351 Depending on the arch implementation of hardware breakpoints, 352 some of them have separate registers for data and instruction 353 breakpoints addresses, others have mixed registers to store 354 them but define the access type in a control register. 355 Select this option if your arch implements breakpoints under the 356 latter fashion. 357 358config HAVE_USER_RETURN_NOTIFIER 359 bool 360 361config HAVE_PERF_EVENTS_NMI 362 bool 363 help 364 System hardware can generate an NMI using the perf event 365 subsystem. Also has support for calculating CPU cycle events 366 to determine how many clock cycles in a given period. 367 368config HAVE_HARDLOCKUP_DETECTOR_PERF 369 bool 370 depends on HAVE_PERF_EVENTS_NMI 371 help 372 The arch chooses to use the generic perf-NMI-based hardlockup 373 detector. Must define HAVE_PERF_EVENTS_NMI. 374 375config HAVE_NMI_WATCHDOG 376 depends on HAVE_NMI 377 bool 378 help 379 The arch provides a low level NMI watchdog. It provides 380 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 381 382config HAVE_HARDLOCKUP_DETECTOR_ARCH 383 bool 384 select HAVE_NMI_WATCHDOG 385 help 386 The arch chooses to provide its own hardlockup detector, which is 387 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 388 interfaces and parameters provided by hardlockup detector subsystem. 389 390config HAVE_PERF_REGS 391 bool 392 help 393 Support selective register dumps for perf events. This includes 394 bit-mapping of each registers and a unique architecture id. 395 396config HAVE_PERF_USER_STACK_DUMP 397 bool 398 help 399 Support user stack dumps for perf event samples. This needs 400 access to the user stack pointer which is not unified across 401 architectures. 402 403config HAVE_ARCH_JUMP_LABEL 404 bool 405 406config HAVE_ARCH_JUMP_LABEL_RELATIVE 407 bool 408 409config MMU_GATHER_TABLE_FREE 410 bool 411 412config MMU_GATHER_RCU_TABLE_FREE 413 bool 414 select MMU_GATHER_TABLE_FREE 415 416config MMU_GATHER_PAGE_SIZE 417 bool 418 419config MMU_GATHER_NO_RANGE 420 bool 421 422config MMU_GATHER_NO_GATHER 423 bool 424 depends on MMU_GATHER_TABLE_FREE 425 426config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 427 bool 428 help 429 Temporary select until all architectures can be converted to have 430 irqs disabled over activate_mm. Architectures that do IPI based TLB 431 shootdowns should enable this. 432 433config ARCH_HAVE_NMI_SAFE_CMPXCHG 434 bool 435 436config HAVE_ALIGNED_STRUCT_PAGE 437 bool 438 help 439 This makes sure that struct pages are double word aligned and that 440 e.g. the SLUB allocator can perform double word atomic operations 441 on a struct page for better performance. However selecting this 442 might increase the size of a struct page by a word. 443 444config HAVE_CMPXCHG_LOCAL 445 bool 446 447config HAVE_CMPXCHG_DOUBLE 448 bool 449 450config ARCH_WEAK_RELEASE_ACQUIRE 451 bool 452 453config ARCH_WANT_IPC_PARSE_VERSION 454 bool 455 456config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 457 bool 458 459config ARCH_WANT_OLD_COMPAT_IPC 460 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 461 bool 462 463config HAVE_ARCH_SECCOMP 464 bool 465 help 466 An arch should select this symbol to support seccomp mode 1 (the fixed 467 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 468 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 469 - __NR_seccomp_read_32 470 - __NR_seccomp_write_32 471 - __NR_seccomp_exit_32 472 - __NR_seccomp_sigreturn_32 473 474config HAVE_ARCH_SECCOMP_FILTER 475 bool 476 select HAVE_ARCH_SECCOMP 477 help 478 An arch should select this symbol if it provides all of these things: 479 - all the requirements for HAVE_ARCH_SECCOMP 480 - syscall_get_arch() 481 - syscall_get_arguments() 482 - syscall_rollback() 483 - syscall_set_return_value() 484 - SIGSYS siginfo_t support 485 - secure_computing is called from a ptrace_event()-safe context 486 - secure_computing return value is checked and a return value of -1 487 results in the system call being skipped immediately. 488 - seccomp syscall wired up 489 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 490 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 491 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 492 493config SECCOMP 494 prompt "Enable seccomp to safely execute untrusted bytecode" 495 def_bool y 496 depends on HAVE_ARCH_SECCOMP 497 help 498 This kernel feature is useful for number crunching applications 499 that may need to handle untrusted bytecode during their 500 execution. By using pipes or other transports made available 501 to the process as file descriptors supporting the read/write 502 syscalls, it's possible to isolate those applications in their 503 own address space using seccomp. Once seccomp is enabled via 504 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 505 disabled and the task is only allowed to execute a few safe 506 syscalls defined by each seccomp mode. 507 508 If unsure, say Y. 509 510config SECCOMP_FILTER 511 def_bool y 512 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 513 help 514 Enable tasks to build secure computing environments defined 515 in terms of Berkeley Packet Filter programs which implement 516 task-defined system call filtering polices. 517 518 See Documentation/userspace-api/seccomp_filter.rst for details. 519 520config SECCOMP_CACHE_DEBUG 521 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 522 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 523 depends on PROC_FS 524 help 525 This enables the /proc/pid/seccomp_cache interface to monitor 526 seccomp cache data. The file format is subject to change. Reading 527 the file requires CAP_SYS_ADMIN. 528 529 This option is for debugging only. Enabling presents the risk that 530 an adversary may be able to infer the seccomp filter logic. 531 532 If unsure, say N. 533 534config HAVE_ARCH_STACKLEAK 535 bool 536 help 537 An architecture should select this if it has the code which 538 fills the used part of the kernel stack with the STACKLEAK_POISON 539 value before returning from system calls. 540 541config HAVE_STACKPROTECTOR 542 bool 543 help 544 An arch should select this symbol if: 545 - it has implemented a stack canary (e.g. __stack_chk_guard) 546 547config STACKPROTECTOR 548 bool "Stack Protector buffer overflow detection" 549 depends on HAVE_STACKPROTECTOR 550 depends on $(cc-option,-fstack-protector) 551 default y 552 help 553 This option turns on the "stack-protector" GCC feature. This 554 feature puts, at the beginning of functions, a canary value on 555 the stack just before the return address, and validates 556 the value just before actually returning. Stack based buffer 557 overflows (that need to overwrite this return address) now also 558 overwrite the canary, which gets detected and the attack is then 559 neutralized via a kernel panic. 560 561 Functions will have the stack-protector canary logic added if they 562 have an 8-byte or larger character array on the stack. 563 564 This feature requires gcc version 4.2 or above, or a distribution 565 gcc with the feature backported ("-fstack-protector"). 566 567 On an x86 "defconfig" build, this feature adds canary checks to 568 about 3% of all kernel functions, which increases kernel code size 569 by about 0.3%. 570 571config STACKPROTECTOR_STRONG 572 bool "Strong Stack Protector" 573 depends on STACKPROTECTOR 574 depends on $(cc-option,-fstack-protector-strong) 575 default y 576 help 577 Functions will have the stack-protector canary logic added in any 578 of the following conditions: 579 580 - local variable's address used as part of the right hand side of an 581 assignment or function argument 582 - local variable is an array (or union containing an array), 583 regardless of array type or length 584 - uses register local variables 585 586 This feature requires gcc version 4.9 or above, or a distribution 587 gcc with the feature backported ("-fstack-protector-strong"). 588 589 On an x86 "defconfig" build, this feature adds canary checks to 590 about 20% of all kernel functions, which increases the kernel code 591 size by about 2%. 592 593config ARCH_SUPPORTS_SHADOW_CALL_STACK 594 bool 595 help 596 An architecture should select this if it supports Clang's Shadow 597 Call Stack and implements runtime support for shadow stack 598 switching. 599 600config SHADOW_CALL_STACK 601 bool "Clang Shadow Call Stack" 602 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 603 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 604 help 605 This option enables Clang's Shadow Call Stack, which uses a 606 shadow stack to protect function return addresses from being 607 overwritten by an attacker. More information can be found in 608 Clang's documentation: 609 610 https://clang.llvm.org/docs/ShadowCallStack.html 611 612 Note that security guarantees in the kernel differ from the 613 ones documented for user space. The kernel must store addresses 614 of shadow stacks in memory, which means an attacker capable of 615 reading and writing arbitrary memory may be able to locate them 616 and hijack control flow by modifying the stacks. 617 618config HAVE_ARCH_WITHIN_STACK_FRAMES 619 bool 620 help 621 An architecture should select this if it can walk the kernel stack 622 frames to determine if an object is part of either the arguments 623 or local variables (i.e. that it excludes saved return addresses, 624 and similar) by implementing an inline arch_within_stack_frames(), 625 which is used by CONFIG_HARDENED_USERCOPY. 626 627config HAVE_CONTEXT_TRACKING 628 bool 629 help 630 Provide kernel/user boundaries probes necessary for subsystems 631 that need it, such as userspace RCU extended quiescent state. 632 Syscalls need to be wrapped inside user_exit()-user_enter(), either 633 optimized behind static key or through the slow path using TIF_NOHZ 634 flag. Exceptions handlers must be wrapped as well. Irqs are already 635 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 636 handling on irq exit still need to be protected. 637 638config HAVE_CONTEXT_TRACKING_OFFSTACK 639 bool 640 help 641 Architecture neither relies on exception_enter()/exception_exit() 642 nor on schedule_user(). Also preempt_schedule_notrace() and 643 preempt_schedule_irq() can't be called in a preemptible section 644 while context tracking is CONTEXT_USER. This feature reflects a sane 645 entry implementation where the following requirements are met on 646 critical entry code, ie: before user_exit() or after user_enter(): 647 648 - Critical entry code isn't preemptible (or better yet: 649 not interruptible). 650 - No use of RCU read side critical sections, unless rcu_nmi_enter() 651 got called. 652 - No use of instrumentation, unless instrumentation_begin() got 653 called. 654 655config HAVE_TIF_NOHZ 656 bool 657 help 658 Arch relies on TIF_NOHZ and syscall slow path to implement context 659 tracking calls to user_enter()/user_exit(). 660 661config HAVE_VIRT_CPU_ACCOUNTING 662 bool 663 664config HAVE_VIRT_CPU_ACCOUNTING_IDLE 665 bool 666 help 667 Architecture has its own way to account idle CPU time and therefore 668 doesn't implement vtime_account_idle(). 669 670config ARCH_HAS_SCALED_CPUTIME 671 bool 672 673config HAVE_VIRT_CPU_ACCOUNTING_GEN 674 bool 675 default y if 64BIT 676 help 677 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 678 Before enabling this option, arch code must be audited 679 to ensure there are no races in concurrent read/write of 680 cputime_t. For example, reading/writing 64-bit cputime_t on 681 some 32-bit arches may require multiple accesses, so proper 682 locking is needed to protect against concurrent accesses. 683 684config HAVE_IRQ_TIME_ACCOUNTING 685 bool 686 help 687 Archs need to ensure they use a high enough resolution clock to 688 support irq time accounting and then call enable_sched_clock_irqtime(). 689 690config HAVE_MOVE_PUD 691 bool 692 help 693 Architectures that select this are able to move page tables at the 694 PUD level. If there are only 3 page table levels, the move effectively 695 happens at the PGD level. 696 697config HAVE_MOVE_PMD 698 bool 699 help 700 Archs that select this are able to move page tables at the PMD level. 701 702config HAVE_ARCH_TRANSPARENT_HUGEPAGE 703 bool 704 705config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 706 bool 707 708config HAVE_ARCH_HUGE_VMAP 709 bool 710 711config ARCH_WANT_HUGE_PMD_SHARE 712 bool 713 714config HAVE_ARCH_SOFT_DIRTY 715 bool 716 717config HAVE_MOD_ARCH_SPECIFIC 718 bool 719 help 720 The arch uses struct mod_arch_specific to store data. Many arches 721 just need a simple module loader without arch specific data - those 722 should not enable this. 723 724config MODULES_USE_ELF_RELA 725 bool 726 help 727 Modules only use ELF RELA relocations. Modules with ELF REL 728 relocations will give an error. 729 730config MODULES_USE_ELF_REL 731 bool 732 help 733 Modules only use ELF REL relocations. Modules with ELF RELA 734 relocations will give an error. 735 736config HAVE_IRQ_EXIT_ON_IRQ_STACK 737 bool 738 help 739 Architecture doesn't only execute the irq handler on the irq stack 740 but also irq_exit(). This way we can process softirqs on this irq 741 stack instead of switching to a new one when we call __do_softirq() 742 in the end of an hardirq. 743 This spares a stack switch and improves cache usage on softirq 744 processing. 745 746config PGTABLE_LEVELS 747 int 748 default 2 749 750config ARCH_HAS_ELF_RANDOMIZE 751 bool 752 help 753 An architecture supports choosing randomized locations for 754 stack, mmap, brk, and ET_DYN. Defined functions: 755 - arch_mmap_rnd() 756 - arch_randomize_brk() 757 758config HAVE_ARCH_MMAP_RND_BITS 759 bool 760 help 761 An arch should select this symbol if it supports setting a variable 762 number of bits for use in establishing the base address for mmap 763 allocations, has MMU enabled and provides values for both: 764 - ARCH_MMAP_RND_BITS_MIN 765 - ARCH_MMAP_RND_BITS_MAX 766 767config HAVE_EXIT_THREAD 768 bool 769 help 770 An architecture implements exit_thread. 771 772config ARCH_MMAP_RND_BITS_MIN 773 int 774 775config ARCH_MMAP_RND_BITS_MAX 776 int 777 778config ARCH_MMAP_RND_BITS_DEFAULT 779 int 780 781config ARCH_MMAP_RND_BITS 782 int "Number of bits to use for ASLR of mmap base address" if EXPERT 783 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 784 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 785 default ARCH_MMAP_RND_BITS_MIN 786 depends on HAVE_ARCH_MMAP_RND_BITS 787 help 788 This value can be used to select the number of bits to use to 789 determine the random offset to the base address of vma regions 790 resulting from mmap allocations. This value will be bounded 791 by the architecture's minimum and maximum supported values. 792 793 This value can be changed after boot using the 794 /proc/sys/vm/mmap_rnd_bits tunable 795 796config HAVE_ARCH_MMAP_RND_COMPAT_BITS 797 bool 798 help 799 An arch should select this symbol if it supports running applications 800 in compatibility mode, supports setting a variable number of bits for 801 use in establishing the base address for mmap allocations, has MMU 802 enabled and provides values for both: 803 - ARCH_MMAP_RND_COMPAT_BITS_MIN 804 - ARCH_MMAP_RND_COMPAT_BITS_MAX 805 806config ARCH_MMAP_RND_COMPAT_BITS_MIN 807 int 808 809config ARCH_MMAP_RND_COMPAT_BITS_MAX 810 int 811 812config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 813 int 814 815config ARCH_MMAP_RND_COMPAT_BITS 816 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 817 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 818 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 819 default ARCH_MMAP_RND_COMPAT_BITS_MIN 820 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 821 help 822 This value can be used to select the number of bits to use to 823 determine the random offset to the base address of vma regions 824 resulting from mmap allocations for compatible applications This 825 value will be bounded by the architecture's minimum and maximum 826 supported values. 827 828 This value can be changed after boot using the 829 /proc/sys/vm/mmap_rnd_compat_bits tunable 830 831config HAVE_ARCH_COMPAT_MMAP_BASES 832 bool 833 help 834 This allows 64bit applications to invoke 32-bit mmap() syscall 835 and vice-versa 32-bit applications to call 64-bit mmap(). 836 Required for applications doing different bitness syscalls. 837 838# This allows to use a set of generic functions to determine mmap base 839# address by giving priority to top-down scheme only if the process 840# is not in legacy mode (compat task, unlimited stack size or 841# sysctl_legacy_va_layout). 842# Architecture that selects this option can provide its own version of: 843# - STACK_RND_MASK 844config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 845 bool 846 depends on MMU 847 select ARCH_HAS_ELF_RANDOMIZE 848 849config HAVE_STACK_VALIDATION 850 bool 851 help 852 Architecture supports the 'objtool check' host tool command, which 853 performs compile-time stack metadata validation. 854 855config HAVE_RELIABLE_STACKTRACE 856 bool 857 help 858 Architecture has either save_stack_trace_tsk_reliable() or 859 arch_stack_walk_reliable() function which only returns a stack trace 860 if it can guarantee the trace is reliable. 861 862config HAVE_ARCH_HASH 863 bool 864 default n 865 help 866 If this is set, the architecture provides an <asm/hash.h> 867 file which provides platform-specific implementations of some 868 functions in <linux/hash.h> or fs/namei.c. 869 870config HAVE_ARCH_NVRAM_OPS 871 bool 872 873config ISA_BUS_API 874 def_bool ISA 875 876# 877# ABI hall of shame 878# 879config CLONE_BACKWARDS 880 bool 881 help 882 Architecture has tls passed as the 4th argument of clone(2), 883 not the 5th one. 884 885config CLONE_BACKWARDS2 886 bool 887 help 888 Architecture has the first two arguments of clone(2) swapped. 889 890config CLONE_BACKWARDS3 891 bool 892 help 893 Architecture has tls passed as the 3rd argument of clone(2), 894 not the 5th one. 895 896config ODD_RT_SIGACTION 897 bool 898 help 899 Architecture has unusual rt_sigaction(2) arguments 900 901config OLD_SIGSUSPEND 902 bool 903 help 904 Architecture has old sigsuspend(2) syscall, of one-argument variety 905 906config OLD_SIGSUSPEND3 907 bool 908 help 909 Even weirder antique ABI - three-argument sigsuspend(2) 910 911config OLD_SIGACTION 912 bool 913 help 914 Architecture has old sigaction(2) syscall. Nope, not the same 915 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 916 but fairly different variant of sigaction(2), thanks to OSF/1 917 compatibility... 918 919config COMPAT_OLD_SIGACTION 920 bool 921 922config COMPAT_32BIT_TIME 923 bool "Provide system calls for 32-bit time_t" 924 default !64BIT || COMPAT 925 help 926 This enables 32 bit time_t support in addition to 64 bit time_t support. 927 This is relevant on all 32-bit architectures, and 64-bit architectures 928 as part of compat syscall handling. 929 930config ARCH_NO_PREEMPT 931 bool 932 933config ARCH_SUPPORTS_RT 934 bool 935 936config CPU_NO_EFFICIENT_FFS 937 def_bool n 938 939config HAVE_ARCH_VMAP_STACK 940 def_bool n 941 help 942 An arch should select this symbol if it can support kernel stacks 943 in vmalloc space. This means: 944 945 - vmalloc space must be large enough to hold many kernel stacks. 946 This may rule out many 32-bit architectures. 947 948 - Stacks in vmalloc space need to work reliably. For example, if 949 vmap page tables are created on demand, either this mechanism 950 needs to work while the stack points to a virtual address with 951 unpopulated page tables or arch code (switch_to() and switch_mm(), 952 most likely) needs to ensure that the stack's page table entries 953 are populated before running on a possibly unpopulated stack. 954 955 - If the stack overflows into a guard page, something reasonable 956 should happen. The definition of "reasonable" is flexible, but 957 instantly rebooting without logging anything would be unfriendly. 958 959config VMAP_STACK 960 default y 961 bool "Use a virtually-mapped stack" 962 depends on HAVE_ARCH_VMAP_STACK 963 depends on !KASAN || KASAN_VMALLOC 964 help 965 Enable this if you want the use virtually-mapped kernel stacks 966 with guard pages. This causes kernel stack overflows to be 967 caught immediately rather than causing difficult-to-diagnose 968 corruption. 969 970 To use this with KASAN, the architecture must support backing 971 virtual mappings with real shadow memory, and KASAN_VMALLOC must 972 be enabled. 973 974config ARCH_OPTIONAL_KERNEL_RWX 975 def_bool n 976 977config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 978 def_bool n 979 980config ARCH_HAS_STRICT_KERNEL_RWX 981 def_bool n 982 983config STRICT_KERNEL_RWX 984 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 985 depends on ARCH_HAS_STRICT_KERNEL_RWX 986 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 987 help 988 If this is set, kernel text and rodata memory will be made read-only, 989 and non-text memory will be made non-executable. This provides 990 protection against certain security exploits (e.g. executing the heap 991 or modifying text) 992 993 These features are considered standard security practice these days. 994 You should say Y here in almost all cases. 995 996config ARCH_HAS_STRICT_MODULE_RWX 997 def_bool n 998 999config STRICT_MODULE_RWX 1000 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1001 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1002 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1003 help 1004 If this is set, module text and rodata memory will be made read-only, 1005 and non-text memory will be made non-executable. This provides 1006 protection against certain security exploits (e.g. writing to text) 1007 1008# select if the architecture provides an asm/dma-direct.h header 1009config ARCH_HAS_PHYS_TO_DMA 1010 bool 1011 1012config HAVE_ARCH_COMPILER_H 1013 bool 1014 help 1015 An architecture can select this if it provides an 1016 asm/compiler.h header that should be included after 1017 linux/compiler-*.h in order to override macro definitions that those 1018 headers generally provide. 1019 1020config HAVE_ARCH_PREL32_RELOCATIONS 1021 bool 1022 help 1023 May be selected by an architecture if it supports place-relative 1024 32-bit relocations, both in the toolchain and in the module loader, 1025 in which case relative references can be used in special sections 1026 for PCI fixup, initcalls etc which are only half the size on 64 bit 1027 architectures, and don't require runtime relocation on relocatable 1028 kernels. 1029 1030config ARCH_USE_MEMREMAP_PROT 1031 bool 1032 1033config LOCK_EVENT_COUNTS 1034 bool "Locking event counts collection" 1035 depends on DEBUG_FS 1036 help 1037 Enable light-weight counting of various locking related events 1038 in the system with minimal performance impact. This reduces 1039 the chance of application behavior change because of timing 1040 differences. The counts are reported via debugfs. 1041 1042# Select if the architecture has support for applying RELR relocations. 1043config ARCH_HAS_RELR 1044 bool 1045 1046config RELR 1047 bool "Use RELR relocation packing" 1048 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1049 default y 1050 help 1051 Store the kernel's dynamic relocations in the RELR relocation packing 1052 format. Requires a compatible linker (LLD supports this feature), as 1053 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1054 are compatible). 1055 1056config ARCH_HAS_MEM_ENCRYPT 1057 bool 1058 1059config HAVE_SPARSE_SYSCALL_NR 1060 bool 1061 help 1062 An architecture should select this if its syscall numbering is sparse 1063 to save space. For example, MIPS architecture has a syscall array with 1064 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1065 related optimizations for a given architecture. 1066 1067config ARCH_HAS_VDSO_DATA 1068 bool 1069 1070config HAVE_STATIC_CALL 1071 bool 1072 1073config HAVE_STATIC_CALL_INLINE 1074 bool 1075 depends on HAVE_STATIC_CALL 1076 1077config ARCH_WANT_LD_ORPHAN_WARN 1078 bool 1079 help 1080 An arch should select this symbol once all linker sections are explicitly 1081 included, size-asserted, or discarded in the linker scripts. This is 1082 important because we never want expected sections to be placed heuristically 1083 by the linker, since the locations of such sections can change between linker 1084 versions. 1085 1086config HAVE_ARCH_PFN_VALID 1087 bool 1088 1089config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1090 bool 1091 1092source "kernel/gcov/Kconfig" 1093 1094source "scripts/gcc-plugins/Kconfig" 1095 1096endmenu 1097