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 490config SECCOMP 491 prompt "Enable seccomp to safely execute untrusted bytecode" 492 def_bool y 493 depends on HAVE_ARCH_SECCOMP 494 help 495 This kernel feature is useful for number crunching applications 496 that may need to handle untrusted bytecode during their 497 execution. By using pipes or other transports made available 498 to the process as file descriptors supporting the read/write 499 syscalls, it's possible to isolate those applications in their 500 own address space using seccomp. Once seccomp is enabled via 501 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 502 disabled and the task is only allowed to execute a few safe 503 syscalls defined by each seccomp mode. 504 505 If unsure, say Y. 506 507config SECCOMP_FILTER 508 def_bool y 509 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 510 help 511 Enable tasks to build secure computing environments defined 512 in terms of Berkeley Packet Filter programs which implement 513 task-defined system call filtering polices. 514 515 See Documentation/userspace-api/seccomp_filter.rst for details. 516 517config HAVE_ARCH_STACKLEAK 518 bool 519 help 520 An architecture should select this if it has the code which 521 fills the used part of the kernel stack with the STACKLEAK_POISON 522 value before returning from system calls. 523 524config HAVE_STACKPROTECTOR 525 bool 526 help 527 An arch should select this symbol if: 528 - it has implemented a stack canary (e.g. __stack_chk_guard) 529 530config STACKPROTECTOR 531 bool "Stack Protector buffer overflow detection" 532 depends on HAVE_STACKPROTECTOR 533 depends on $(cc-option,-fstack-protector) 534 default y 535 help 536 This option turns on the "stack-protector" GCC feature. This 537 feature puts, at the beginning of functions, a canary value on 538 the stack just before the return address, and validates 539 the value just before actually returning. Stack based buffer 540 overflows (that need to overwrite this return address) now also 541 overwrite the canary, which gets detected and the attack is then 542 neutralized via a kernel panic. 543 544 Functions will have the stack-protector canary logic added if they 545 have an 8-byte or larger character array on the stack. 546 547 This feature requires gcc version 4.2 or above, or a distribution 548 gcc with the feature backported ("-fstack-protector"). 549 550 On an x86 "defconfig" build, this feature adds canary checks to 551 about 3% of all kernel functions, which increases kernel code size 552 by about 0.3%. 553 554config STACKPROTECTOR_STRONG 555 bool "Strong Stack Protector" 556 depends on STACKPROTECTOR 557 depends on $(cc-option,-fstack-protector-strong) 558 default y 559 help 560 Functions will have the stack-protector canary logic added in any 561 of the following conditions: 562 563 - local variable's address used as part of the right hand side of an 564 assignment or function argument 565 - local variable is an array (or union containing an array), 566 regardless of array type or length 567 - uses register local variables 568 569 This feature requires gcc version 4.9 or above, or a distribution 570 gcc with the feature backported ("-fstack-protector-strong"). 571 572 On an x86 "defconfig" build, this feature adds canary checks to 573 about 20% of all kernel functions, which increases the kernel code 574 size by about 2%. 575 576config ARCH_SUPPORTS_SHADOW_CALL_STACK 577 bool 578 help 579 An architecture should select this if it supports Clang's Shadow 580 Call Stack and implements runtime support for shadow stack 581 switching. 582 583config SHADOW_CALL_STACK 584 bool "Clang Shadow Call Stack" 585 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 586 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 587 help 588 This option enables Clang's Shadow Call Stack, which uses a 589 shadow stack to protect function return addresses from being 590 overwritten by an attacker. More information can be found in 591 Clang's documentation: 592 593 https://clang.llvm.org/docs/ShadowCallStack.html 594 595 Note that security guarantees in the kernel differ from the 596 ones documented for user space. The kernel must store addresses 597 of shadow stacks in memory, which means an attacker capable of 598 reading and writing arbitrary memory may be able to locate them 599 and hijack control flow by modifying the stacks. 600 601config HAVE_ARCH_WITHIN_STACK_FRAMES 602 bool 603 help 604 An architecture should select this if it can walk the kernel stack 605 frames to determine if an object is part of either the arguments 606 or local variables (i.e. that it excludes saved return addresses, 607 and similar) by implementing an inline arch_within_stack_frames(), 608 which is used by CONFIG_HARDENED_USERCOPY. 609 610config HAVE_CONTEXT_TRACKING 611 bool 612 help 613 Provide kernel/user boundaries probes necessary for subsystems 614 that need it, such as userspace RCU extended quiescent state. 615 Syscalls need to be wrapped inside user_exit()-user_enter(), either 616 optimized behind static key or through the slow path using TIF_NOHZ 617 flag. Exceptions handlers must be wrapped as well. Irqs are already 618 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 619 handling on irq exit still need to be protected. 620 621config HAVE_TIF_NOHZ 622 bool 623 help 624 Arch relies on TIF_NOHZ and syscall slow path to implement context 625 tracking calls to user_enter()/user_exit(). 626 627config HAVE_VIRT_CPU_ACCOUNTING 628 bool 629 630config ARCH_HAS_SCALED_CPUTIME 631 bool 632 633config HAVE_VIRT_CPU_ACCOUNTING_GEN 634 bool 635 default y if 64BIT 636 help 637 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 638 Before enabling this option, arch code must be audited 639 to ensure there are no races in concurrent read/write of 640 cputime_t. For example, reading/writing 64-bit cputime_t on 641 some 32-bit arches may require multiple accesses, so proper 642 locking is needed to protect against concurrent accesses. 643 644 645config HAVE_IRQ_TIME_ACCOUNTING 646 bool 647 help 648 Archs need to ensure they use a high enough resolution clock to 649 support irq time accounting and then call enable_sched_clock_irqtime(). 650 651config HAVE_MOVE_PUD 652 bool 653 help 654 Architectures that select this are able to move page tables at the 655 PUD level. If there are only 3 page table levels, the move effectively 656 happens at the PGD level. 657 658config HAVE_MOVE_PMD 659 bool 660 help 661 Archs that select this are able to move page tables at the PMD level. 662 663config HAVE_ARCH_TRANSPARENT_HUGEPAGE 664 bool 665 666config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 667 bool 668 669config HAVE_ARCH_HUGE_VMAP 670 bool 671 672config ARCH_WANT_HUGE_PMD_SHARE 673 bool 674 675config HAVE_ARCH_SOFT_DIRTY 676 bool 677 678config HAVE_MOD_ARCH_SPECIFIC 679 bool 680 help 681 The arch uses struct mod_arch_specific to store data. Many arches 682 just need a simple module loader without arch specific data - those 683 should not enable this. 684 685config MODULES_USE_ELF_RELA 686 bool 687 help 688 Modules only use ELF RELA relocations. Modules with ELF REL 689 relocations will give an error. 690 691config MODULES_USE_ELF_REL 692 bool 693 help 694 Modules only use ELF REL relocations. Modules with ELF RELA 695 relocations will give an error. 696 697config HAVE_IRQ_EXIT_ON_IRQ_STACK 698 bool 699 help 700 Architecture doesn't only execute the irq handler on the irq stack 701 but also irq_exit(). This way we can process softirqs on this irq 702 stack instead of switching to a new one when we call __do_softirq() 703 in the end of an hardirq. 704 This spares a stack switch and improves cache usage on softirq 705 processing. 706 707config PGTABLE_LEVELS 708 int 709 default 2 710 711config ARCH_HAS_ELF_RANDOMIZE 712 bool 713 help 714 An architecture supports choosing randomized locations for 715 stack, mmap, brk, and ET_DYN. Defined functions: 716 - arch_mmap_rnd() 717 - arch_randomize_brk() 718 719config HAVE_ARCH_MMAP_RND_BITS 720 bool 721 help 722 An arch should select this symbol if it supports setting a variable 723 number of bits for use in establishing the base address for mmap 724 allocations, has MMU enabled and provides values for both: 725 - ARCH_MMAP_RND_BITS_MIN 726 - ARCH_MMAP_RND_BITS_MAX 727 728config HAVE_EXIT_THREAD 729 bool 730 help 731 An architecture implements exit_thread. 732 733config ARCH_MMAP_RND_BITS_MIN 734 int 735 736config ARCH_MMAP_RND_BITS_MAX 737 int 738 739config ARCH_MMAP_RND_BITS_DEFAULT 740 int 741 742config ARCH_MMAP_RND_BITS 743 int "Number of bits to use for ASLR of mmap base address" if EXPERT 744 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 745 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 746 default ARCH_MMAP_RND_BITS_MIN 747 depends on HAVE_ARCH_MMAP_RND_BITS 748 help 749 This value can be used to select the number of bits to use to 750 determine the random offset to the base address of vma regions 751 resulting from mmap allocations. This value will be bounded 752 by the architecture's minimum and maximum supported values. 753 754 This value can be changed after boot using the 755 /proc/sys/vm/mmap_rnd_bits tunable 756 757config HAVE_ARCH_MMAP_RND_COMPAT_BITS 758 bool 759 help 760 An arch should select this symbol if it supports running applications 761 in compatibility mode, supports setting a variable number of bits for 762 use in establishing the base address for mmap allocations, has MMU 763 enabled and provides values for both: 764 - ARCH_MMAP_RND_COMPAT_BITS_MIN 765 - ARCH_MMAP_RND_COMPAT_BITS_MAX 766 767config ARCH_MMAP_RND_COMPAT_BITS_MIN 768 int 769 770config ARCH_MMAP_RND_COMPAT_BITS_MAX 771 int 772 773config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 774 int 775 776config ARCH_MMAP_RND_COMPAT_BITS 777 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 778 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 779 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 780 default ARCH_MMAP_RND_COMPAT_BITS_MIN 781 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 782 help 783 This value can be used to select the number of bits to use to 784 determine the random offset to the base address of vma regions 785 resulting from mmap allocations for compatible applications This 786 value will be bounded by the architecture's minimum and maximum 787 supported values. 788 789 This value can be changed after boot using the 790 /proc/sys/vm/mmap_rnd_compat_bits tunable 791 792config HAVE_ARCH_COMPAT_MMAP_BASES 793 bool 794 help 795 This allows 64bit applications to invoke 32-bit mmap() syscall 796 and vice-versa 32-bit applications to call 64-bit mmap(). 797 Required for applications doing different bitness syscalls. 798 799# This allows to use a set of generic functions to determine mmap base 800# address by giving priority to top-down scheme only if the process 801# is not in legacy mode (compat task, unlimited stack size or 802# sysctl_legacy_va_layout). 803# Architecture that selects this option can provide its own version of: 804# - STACK_RND_MASK 805config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 806 bool 807 depends on MMU 808 select ARCH_HAS_ELF_RANDOMIZE 809 810config HAVE_STACK_VALIDATION 811 bool 812 help 813 Architecture supports the 'objtool check' host tool command, which 814 performs compile-time stack metadata validation. 815 816config HAVE_RELIABLE_STACKTRACE 817 bool 818 help 819 Architecture has either save_stack_trace_tsk_reliable() or 820 arch_stack_walk_reliable() function which only returns a stack trace 821 if it can guarantee the trace is reliable. 822 823config HAVE_ARCH_HASH 824 bool 825 default n 826 help 827 If this is set, the architecture provides an <asm/hash.h> 828 file which provides platform-specific implementations of some 829 functions in <linux/hash.h> or fs/namei.c. 830 831config HAVE_ARCH_NVRAM_OPS 832 bool 833 834config ISA_BUS_API 835 def_bool ISA 836 837# 838# ABI hall of shame 839# 840config CLONE_BACKWARDS 841 bool 842 help 843 Architecture has tls passed as the 4th argument of clone(2), 844 not the 5th one. 845 846config CLONE_BACKWARDS2 847 bool 848 help 849 Architecture has the first two arguments of clone(2) swapped. 850 851config CLONE_BACKWARDS3 852 bool 853 help 854 Architecture has tls passed as the 3rd argument of clone(2), 855 not the 5th one. 856 857config ODD_RT_SIGACTION 858 bool 859 help 860 Architecture has unusual rt_sigaction(2) arguments 861 862config OLD_SIGSUSPEND 863 bool 864 help 865 Architecture has old sigsuspend(2) syscall, of one-argument variety 866 867config OLD_SIGSUSPEND3 868 bool 869 help 870 Even weirder antique ABI - three-argument sigsuspend(2) 871 872config OLD_SIGACTION 873 bool 874 help 875 Architecture has old sigaction(2) syscall. Nope, not the same 876 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 877 but fairly different variant of sigaction(2), thanks to OSF/1 878 compatibility... 879 880config COMPAT_OLD_SIGACTION 881 bool 882 883config COMPAT_32BIT_TIME 884 bool "Provide system calls for 32-bit time_t" 885 default !64BIT || COMPAT 886 help 887 This enables 32 bit time_t support in addition to 64 bit time_t support. 888 This is relevant on all 32-bit architectures, and 64-bit architectures 889 as part of compat syscall handling. 890 891config ARCH_NO_PREEMPT 892 bool 893 894config ARCH_SUPPORTS_RT 895 bool 896 897config CPU_NO_EFFICIENT_FFS 898 def_bool n 899 900config HAVE_ARCH_VMAP_STACK 901 def_bool n 902 help 903 An arch should select this symbol if it can support kernel stacks 904 in vmalloc space. This means: 905 906 - vmalloc space must be large enough to hold many kernel stacks. 907 This may rule out many 32-bit architectures. 908 909 - Stacks in vmalloc space need to work reliably. For example, if 910 vmap page tables are created on demand, either this mechanism 911 needs to work while the stack points to a virtual address with 912 unpopulated page tables or arch code (switch_to() and switch_mm(), 913 most likely) needs to ensure that the stack's page table entries 914 are populated before running on a possibly unpopulated stack. 915 916 - If the stack overflows into a guard page, something reasonable 917 should happen. The definition of "reasonable" is flexible, but 918 instantly rebooting without logging anything would be unfriendly. 919 920config VMAP_STACK 921 default y 922 bool "Use a virtually-mapped stack" 923 depends on HAVE_ARCH_VMAP_STACK 924 depends on !KASAN || KASAN_VMALLOC 925 help 926 Enable this if you want the use virtually-mapped kernel stacks 927 with guard pages. This causes kernel stack overflows to be 928 caught immediately rather than causing difficult-to-diagnose 929 corruption. 930 931 To use this with KASAN, the architecture must support backing 932 virtual mappings with real shadow memory, and KASAN_VMALLOC must 933 be enabled. 934 935config ARCH_OPTIONAL_KERNEL_RWX 936 def_bool n 937 938config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 939 def_bool n 940 941config ARCH_HAS_STRICT_KERNEL_RWX 942 def_bool n 943 944config STRICT_KERNEL_RWX 945 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 946 depends on ARCH_HAS_STRICT_KERNEL_RWX 947 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 948 help 949 If this is set, kernel text and rodata memory will be made read-only, 950 and non-text memory will be made non-executable. This provides 951 protection against certain security exploits (e.g. executing the heap 952 or modifying text) 953 954 These features are considered standard security practice these days. 955 You should say Y here in almost all cases. 956 957config ARCH_HAS_STRICT_MODULE_RWX 958 def_bool n 959 960config STRICT_MODULE_RWX 961 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 962 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 963 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 964 help 965 If this is set, module text and rodata memory will be made read-only, 966 and non-text memory will be made non-executable. This provides 967 protection against certain security exploits (e.g. writing to text) 968 969# select if the architecture provides an asm/dma-direct.h header 970config ARCH_HAS_PHYS_TO_DMA 971 bool 972 973config HAVE_ARCH_COMPILER_H 974 bool 975 help 976 An architecture can select this if it provides an 977 asm/compiler.h header that should be included after 978 linux/compiler-*.h in order to override macro definitions that those 979 headers generally provide. 980 981config HAVE_ARCH_PREL32_RELOCATIONS 982 bool 983 help 984 May be selected by an architecture if it supports place-relative 985 32-bit relocations, both in the toolchain and in the module loader, 986 in which case relative references can be used in special sections 987 for PCI fixup, initcalls etc which are only half the size on 64 bit 988 architectures, and don't require runtime relocation on relocatable 989 kernels. 990 991config ARCH_USE_MEMREMAP_PROT 992 bool 993 994config LOCK_EVENT_COUNTS 995 bool "Locking event counts collection" 996 depends on DEBUG_FS 997 help 998 Enable light-weight counting of various locking related events 999 in the system with minimal performance impact. This reduces 1000 the chance of application behavior change because of timing 1001 differences. The counts are reported via debugfs. 1002 1003# Select if the architecture has support for applying RELR relocations. 1004config ARCH_HAS_RELR 1005 bool 1006 1007config RELR 1008 bool "Use RELR relocation packing" 1009 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1010 default y 1011 help 1012 Store the kernel's dynamic relocations in the RELR relocation packing 1013 format. Requires a compatible linker (LLD supports this feature), as 1014 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1015 are compatible). 1016 1017config ARCH_HAS_MEM_ENCRYPT 1018 bool 1019 1020config HAVE_SPARSE_SYSCALL_NR 1021 bool 1022 help 1023 An architecture should select this if its syscall numbering is sparse 1024 to save space. For example, MIPS architecture has a syscall array with 1025 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1026 related optimizations for a given architecture. 1027 1028config ARCH_HAS_VDSO_DATA 1029 bool 1030 1031config HAVE_STATIC_CALL 1032 bool 1033 1034config HAVE_STATIC_CALL_INLINE 1035 bool 1036 depends on HAVE_STATIC_CALL 1037 1038config ARCH_WANT_LD_ORPHAN_WARN 1039 bool 1040 help 1041 An arch should select this symbol once all linker sections are explicitly 1042 included, size-asserted, or discarded in the linker scripts. This is 1043 important because we never want expected sections to be placed heuristically 1044 by the linker, since the locations of such sections can change between linker 1045 versions. 1046 1047config HAVE_ARCH_PFN_VALID 1048 bool 1049 1050source "kernel/gcov/Kconfig" 1051 1052source "scripts/gcc-plugins/Kconfig" 1053 1054endmenu 1055