1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6# 7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8# override the default values in this file. 9# 10source "arch/$(SRCARCH)/Kconfig" 11 12menu "General architecture-dependent options" 13 14config CRASH_CORE 15 bool 16 17config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21config KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config HOTPLUG_SMT 28 bool 29 30config GENERIC_ENTRY 31 bool 32 33config OPROFILE 34 tristate "OProfile system profiling" 35 depends on PROFILING 36 depends on HAVE_OPROFILE 37 select RING_BUFFER 38 select RING_BUFFER_ALLOW_SWAP 39 help 40 OProfile is a profiling system capable of profiling the 41 whole system, include the kernel, kernel modules, libraries, 42 and applications. 43 44 If unsure, say N. 45 46config OPROFILE_EVENT_MULTIPLEX 47 bool "OProfile multiplexing support (EXPERIMENTAL)" 48 default n 49 depends on OPROFILE && X86 50 help 51 The number of hardware counters is limited. The multiplexing 52 feature enables OProfile to gather more events than counters 53 are provided by the hardware. This is realized by switching 54 between events at a user specified time interval. 55 56 If unsure, say N. 57 58config HAVE_OPROFILE 59 bool 60 61config OPROFILE_NMI_TIMER 62 def_bool y 63 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 64 65config KPROBES 66 bool "Kprobes" 67 depends on MODULES 68 depends on HAVE_KPROBES 69 select KALLSYMS 70 help 71 Kprobes allows you to trap at almost any kernel address and 72 execute a callback function. register_kprobe() establishes 73 a probepoint and specifies the callback. Kprobes is useful 74 for kernel debugging, non-intrusive instrumentation and testing. 75 If in doubt, say "N". 76 77config JUMP_LABEL 78 bool "Optimize very unlikely/likely branches" 79 depends on HAVE_ARCH_JUMP_LABEL 80 depends on CC_HAS_ASM_GOTO 81 help 82 This option enables a transparent branch optimization that 83 makes certain almost-always-true or almost-always-false branch 84 conditions even cheaper to execute within the kernel. 85 86 Certain performance-sensitive kernel code, such as trace points, 87 scheduler functionality, networking code and KVM have such 88 branches and include support for this optimization technique. 89 90 If it is detected that the compiler has support for "asm goto", 91 the kernel will compile such branches with just a nop 92 instruction. When the condition flag is toggled to true, the 93 nop will be converted to a jump instruction to execute the 94 conditional block of instructions. 95 96 This technique lowers overhead and stress on the branch prediction 97 of the processor and generally makes the kernel faster. The update 98 of the condition is slower, but those are always very rare. 99 100 ( On 32-bit x86, the necessary options added to the compiler 101 flags may increase the size of the kernel slightly. ) 102 103config STATIC_KEYS_SELFTEST 104 bool "Static key selftest" 105 depends on JUMP_LABEL 106 help 107 Boot time self-test of the branch patching code. 108 109config STATIC_CALL_SELFTEST 110 bool "Static call selftest" 111 depends on HAVE_STATIC_CALL 112 help 113 Boot time self-test of the call patching code. 114 115config OPTPROBES 116 def_bool y 117 depends on KPROBES && HAVE_OPTPROBES 118 select TASKS_RCU if PREEMPTION 119 120config KPROBES_ON_FTRACE 121 def_bool y 122 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 123 depends on DYNAMIC_FTRACE_WITH_REGS 124 help 125 If function tracer is enabled and the arch supports full 126 passing of pt_regs to function tracing, then kprobes can 127 optimize on top of function tracing. 128 129config UPROBES 130 def_bool n 131 depends on ARCH_SUPPORTS_UPROBES 132 help 133 Uprobes is the user-space counterpart to kprobes: they 134 enable instrumentation applications (such as 'perf probe') 135 to establish unintrusive probes in user-space binaries and 136 libraries, by executing handler functions when the probes 137 are hit by user-space applications. 138 139 ( These probes come in the form of single-byte breakpoints, 140 managed by the kernel and kept transparent to the probed 141 application. ) 142 143config HAVE_EFFICIENT_UNALIGNED_ACCESS 144 bool 145 help 146 Some architectures are unable to perform unaligned accesses 147 without the use of get_unaligned/put_unaligned. Others are 148 unable to perform such accesses efficiently (e.g. trap on 149 unaligned access and require fixing it up in the exception 150 handler.) 151 152 This symbol should be selected by an architecture if it can 153 perform unaligned accesses efficiently to allow different 154 code paths to be selected for these cases. Some network 155 drivers, for example, could opt to not fix up alignment 156 problems with received packets if doing so would not help 157 much. 158 159 See Documentation/core-api/unaligned-memory-access.rst for more 160 information on the topic of unaligned memory accesses. 161 162config ARCH_USE_BUILTIN_BSWAP 163 bool 164 help 165 Modern versions of GCC (since 4.4) have builtin functions 166 for handling byte-swapping. Using these, instead of the old 167 inline assembler that the architecture code provides in the 168 __arch_bswapXX() macros, allows the compiler to see what's 169 happening and offers more opportunity for optimisation. In 170 particular, the compiler will be able to combine the byteswap 171 with a nearby load or store and use load-and-swap or 172 store-and-swap instructions if the architecture has them. It 173 should almost *never* result in code which is worse than the 174 hand-coded assembler in <asm/swab.h>. But just in case it 175 does, the use of the builtins is optional. 176 177 Any architecture with load-and-swap or store-and-swap 178 instructions should set this. And it shouldn't hurt to set it 179 on architectures that don't have such instructions. 180 181config KRETPROBES 182 def_bool y 183 depends on KPROBES && HAVE_KRETPROBES 184 185config USER_RETURN_NOTIFIER 186 bool 187 depends on HAVE_USER_RETURN_NOTIFIER 188 help 189 Provide a kernel-internal notification when a cpu is about to 190 switch to user mode. 191 192config HAVE_IOREMAP_PROT 193 bool 194 195config HAVE_KPROBES 196 bool 197 198config HAVE_KRETPROBES 199 bool 200 201config HAVE_OPTPROBES 202 bool 203 204config HAVE_KPROBES_ON_FTRACE 205 bool 206 207config HAVE_FUNCTION_ERROR_INJECTION 208 bool 209 210config HAVE_NMI 211 bool 212 213# 214# An arch should select this if it provides all these things: 215# 216# task_pt_regs() in asm/processor.h or asm/ptrace.h 217# arch_has_single_step() if there is hardware single-step support 218# arch_has_block_step() if there is hardware block-step support 219# asm/syscall.h supplying asm-generic/syscall.h interface 220# linux/regset.h user_regset interfaces 221# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 222# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 223# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 224# signal delivery calls tracehook_signal_handler() 225# 226config HAVE_ARCH_TRACEHOOK 227 bool 228 229config HAVE_DMA_CONTIGUOUS 230 bool 231 232config GENERIC_SMP_IDLE_THREAD 233 bool 234 235config GENERIC_IDLE_POLL_SETUP 236 bool 237 238config ARCH_HAS_FORTIFY_SOURCE 239 bool 240 help 241 An architecture should select this when it can successfully 242 build and run with CONFIG_FORTIFY_SOURCE. 243 244# 245# Select if the arch provides a historic keepinit alias for the retain_initrd 246# command line option 247# 248config ARCH_HAS_KEEPINITRD 249 bool 250 251# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 252config ARCH_HAS_SET_MEMORY 253 bool 254 255# Select if arch has all set_direct_map_invalid/default() functions 256config ARCH_HAS_SET_DIRECT_MAP 257 bool 258 259# 260# Select if the architecture provides the arch_dma_set_uncached symbol to 261# either provide an uncached segement alias for a DMA allocation, or 262# to remap the page tables in place. 263# 264config ARCH_HAS_DMA_SET_UNCACHED 265 bool 266 267# 268# Select if the architectures provides the arch_dma_clear_uncached symbol 269# to undo an in-place page table remap for uncached access. 270# 271config ARCH_HAS_DMA_CLEAR_UNCACHED 272 bool 273 274# Select if arch init_task must go in the __init_task_data section 275config ARCH_TASK_STRUCT_ON_STACK 276 bool 277 278# Select if arch has its private alloc_task_struct() function 279config ARCH_TASK_STRUCT_ALLOCATOR 280 bool 281 282config HAVE_ARCH_THREAD_STRUCT_WHITELIST 283 bool 284 depends on !ARCH_TASK_STRUCT_ALLOCATOR 285 help 286 An architecture should select this to provide hardened usercopy 287 knowledge about what region of the thread_struct should be 288 whitelisted for copying to userspace. Normally this is only the 289 FPU registers. Specifically, arch_thread_struct_whitelist() 290 should be implemented. Without this, the entire thread_struct 291 field in task_struct will be left whitelisted. 292 293# Select if arch has its private alloc_thread_stack() function 294config ARCH_THREAD_STACK_ALLOCATOR 295 bool 296 297# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 298config ARCH_WANTS_DYNAMIC_TASK_STRUCT 299 bool 300 301config ARCH_32BIT_OFF_T 302 bool 303 depends on !64BIT 304 help 305 All new 32-bit architectures should have 64-bit off_t type on 306 userspace side which corresponds to the loff_t kernel type. This 307 is the requirement for modern ABIs. Some existing architectures 308 still support 32-bit off_t. This option is enabled for all such 309 architectures explicitly. 310 311config HAVE_ASM_MODVERSIONS 312 bool 313 help 314 This symbol should be selected by an architecure if it provides 315 <asm/asm-prototypes.h> to support the module versioning for symbols 316 exported from assembly code. 317 318config HAVE_REGS_AND_STACK_ACCESS_API 319 bool 320 help 321 This symbol should be selected by an architecure if it supports 322 the API needed to access registers and stack entries from pt_regs, 323 declared in asm/ptrace.h 324 For example the kprobes-based event tracer needs this API. 325 326config HAVE_RSEQ 327 bool 328 depends on HAVE_REGS_AND_STACK_ACCESS_API 329 help 330 This symbol should be selected by an architecture if it 331 supports an implementation of restartable sequences. 332 333config HAVE_FUNCTION_ARG_ACCESS_API 334 bool 335 help 336 This symbol should be selected by an architecure if it supports 337 the API needed to access function arguments from pt_regs, 338 declared in asm/ptrace.h 339 340config HAVE_HW_BREAKPOINT 341 bool 342 depends on PERF_EVENTS 343 344config HAVE_MIXED_BREAKPOINTS_REGS 345 bool 346 depends on HAVE_HW_BREAKPOINT 347 help 348 Depending on the arch implementation of hardware breakpoints, 349 some of them have separate registers for data and instruction 350 breakpoints addresses, others have mixed registers to store 351 them but define the access type in a control register. 352 Select this option if your arch implements breakpoints under the 353 latter fashion. 354 355config HAVE_USER_RETURN_NOTIFIER 356 bool 357 358config HAVE_PERF_EVENTS_NMI 359 bool 360 help 361 System hardware can generate an NMI using the perf event 362 subsystem. Also has support for calculating CPU cycle events 363 to determine how many clock cycles in a given period. 364 365config HAVE_HARDLOCKUP_DETECTOR_PERF 366 bool 367 depends on HAVE_PERF_EVENTS_NMI 368 help 369 The arch chooses to use the generic perf-NMI-based hardlockup 370 detector. Must define HAVE_PERF_EVENTS_NMI. 371 372config HAVE_NMI_WATCHDOG 373 depends on HAVE_NMI 374 bool 375 help 376 The arch provides a low level NMI watchdog. It provides 377 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 378 379config HAVE_HARDLOCKUP_DETECTOR_ARCH 380 bool 381 select HAVE_NMI_WATCHDOG 382 help 383 The arch chooses to provide its own hardlockup detector, which is 384 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 385 interfaces and parameters provided by hardlockup detector subsystem. 386 387config HAVE_PERF_REGS 388 bool 389 help 390 Support selective register dumps for perf events. This includes 391 bit-mapping of each registers and a unique architecture id. 392 393config HAVE_PERF_USER_STACK_DUMP 394 bool 395 help 396 Support user stack dumps for perf event samples. This needs 397 access to the user stack pointer which is not unified across 398 architectures. 399 400config HAVE_ARCH_JUMP_LABEL 401 bool 402 403config HAVE_ARCH_JUMP_LABEL_RELATIVE 404 bool 405 406config MMU_GATHER_TABLE_FREE 407 bool 408 409config MMU_GATHER_RCU_TABLE_FREE 410 bool 411 select MMU_GATHER_TABLE_FREE 412 413config MMU_GATHER_PAGE_SIZE 414 bool 415 416config MMU_GATHER_NO_RANGE 417 bool 418 419config MMU_GATHER_NO_GATHER 420 bool 421 depends on MMU_GATHER_TABLE_FREE 422 423config ARCH_HAVE_NMI_SAFE_CMPXCHG 424 bool 425 426config HAVE_ALIGNED_STRUCT_PAGE 427 bool 428 help 429 This makes sure that struct pages are double word aligned and that 430 e.g. the SLUB allocator can perform double word atomic operations 431 on a struct page for better performance. However selecting this 432 might increase the size of a struct page by a word. 433 434config HAVE_CMPXCHG_LOCAL 435 bool 436 437config HAVE_CMPXCHG_DOUBLE 438 bool 439 440config ARCH_WEAK_RELEASE_ACQUIRE 441 bool 442 443config ARCH_WANT_IPC_PARSE_VERSION 444 bool 445 446config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 447 bool 448 449config ARCH_WANT_OLD_COMPAT_IPC 450 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 451 bool 452 453config HAVE_ARCH_SECCOMP_FILTER 454 bool 455 help 456 An arch should select this symbol if it provides all of these things: 457 - syscall_get_arch() 458 - syscall_get_arguments() 459 - syscall_rollback() 460 - syscall_set_return_value() 461 - SIGSYS siginfo_t support 462 - secure_computing is called from a ptrace_event()-safe context 463 - secure_computing return value is checked and a return value of -1 464 results in the system call being skipped immediately. 465 - seccomp syscall wired up 466 467config SECCOMP_FILTER 468 def_bool y 469 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 470 help 471 Enable tasks to build secure computing environments defined 472 in terms of Berkeley Packet Filter programs which implement 473 task-defined system call filtering polices. 474 475 See Documentation/userspace-api/seccomp_filter.rst for details. 476 477config HAVE_ARCH_STACKLEAK 478 bool 479 help 480 An architecture should select this if it has the code which 481 fills the used part of the kernel stack with the STACKLEAK_POISON 482 value before returning from system calls. 483 484config HAVE_STACKPROTECTOR 485 bool 486 help 487 An arch should select this symbol if: 488 - it has implemented a stack canary (e.g. __stack_chk_guard) 489 490config STACKPROTECTOR 491 bool "Stack Protector buffer overflow detection" 492 depends on HAVE_STACKPROTECTOR 493 depends on $(cc-option,-fstack-protector) 494 default y 495 help 496 This option turns on the "stack-protector" GCC feature. This 497 feature puts, at the beginning of functions, a canary value on 498 the stack just before the return address, and validates 499 the value just before actually returning. Stack based buffer 500 overflows (that need to overwrite this return address) now also 501 overwrite the canary, which gets detected and the attack is then 502 neutralized via a kernel panic. 503 504 Functions will have the stack-protector canary logic added if they 505 have an 8-byte or larger character array on the stack. 506 507 This feature requires gcc version 4.2 or above, or a distribution 508 gcc with the feature backported ("-fstack-protector"). 509 510 On an x86 "defconfig" build, this feature adds canary checks to 511 about 3% of all kernel functions, which increases kernel code size 512 by about 0.3%. 513 514config STACKPROTECTOR_STRONG 515 bool "Strong Stack Protector" 516 depends on STACKPROTECTOR 517 depends on $(cc-option,-fstack-protector-strong) 518 default y 519 help 520 Functions will have the stack-protector canary logic added in any 521 of the following conditions: 522 523 - local variable's address used as part of the right hand side of an 524 assignment or function argument 525 - local variable is an array (or union containing an array), 526 regardless of array type or length 527 - uses register local variables 528 529 This feature requires gcc version 4.9 or above, or a distribution 530 gcc with the feature backported ("-fstack-protector-strong"). 531 532 On an x86 "defconfig" build, this feature adds canary checks to 533 about 20% of all kernel functions, which increases the kernel code 534 size by about 2%. 535 536config ARCH_SUPPORTS_SHADOW_CALL_STACK 537 bool 538 help 539 An architecture should select this if it supports Clang's Shadow 540 Call Stack and implements runtime support for shadow stack 541 switching. 542 543config SHADOW_CALL_STACK 544 bool "Clang Shadow Call Stack" 545 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 546 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 547 help 548 This option enables Clang's Shadow Call Stack, which uses a 549 shadow stack to protect function return addresses from being 550 overwritten by an attacker. More information can be found in 551 Clang's documentation: 552 553 https://clang.llvm.org/docs/ShadowCallStack.html 554 555 Note that security guarantees in the kernel differ from the 556 ones documented for user space. The kernel must store addresses 557 of shadow stacks in memory, which means an attacker capable of 558 reading and writing arbitrary memory may be able to locate them 559 and hijack control flow by modifying the stacks. 560 561config HAVE_ARCH_WITHIN_STACK_FRAMES 562 bool 563 help 564 An architecture should select this if it can walk the kernel stack 565 frames to determine if an object is part of either the arguments 566 or local variables (i.e. that it excludes saved return addresses, 567 and similar) by implementing an inline arch_within_stack_frames(), 568 which is used by CONFIG_HARDENED_USERCOPY. 569 570config HAVE_CONTEXT_TRACKING 571 bool 572 help 573 Provide kernel/user boundaries probes necessary for subsystems 574 that need it, such as userspace RCU extended quiescent state. 575 Syscalls need to be wrapped inside user_exit()-user_enter(), either 576 optimized behind static key or through the slow path using TIF_NOHZ 577 flag. Exceptions handlers must be wrapped as well. Irqs are already 578 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 579 handling on irq exit still need to be protected. 580 581config HAVE_TIF_NOHZ 582 bool 583 help 584 Arch relies on TIF_NOHZ and syscall slow path to implement context 585 tracking calls to user_enter()/user_exit(). 586 587config HAVE_VIRT_CPU_ACCOUNTING 588 bool 589 590config ARCH_HAS_SCALED_CPUTIME 591 bool 592 593config HAVE_VIRT_CPU_ACCOUNTING_GEN 594 bool 595 default y if 64BIT 596 help 597 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 598 Before enabling this option, arch code must be audited 599 to ensure there are no races in concurrent read/write of 600 cputime_t. For example, reading/writing 64-bit cputime_t on 601 some 32-bit arches may require multiple accesses, so proper 602 locking is needed to protect against concurrent accesses. 603 604 605config HAVE_IRQ_TIME_ACCOUNTING 606 bool 607 help 608 Archs need to ensure they use a high enough resolution clock to 609 support irq time accounting and then call enable_sched_clock_irqtime(). 610 611config HAVE_MOVE_PMD 612 bool 613 help 614 Archs that select this are able to move page tables at the PMD level. 615 616config HAVE_ARCH_TRANSPARENT_HUGEPAGE 617 bool 618 619config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 620 bool 621 622config HAVE_ARCH_HUGE_VMAP 623 bool 624 625config ARCH_WANT_HUGE_PMD_SHARE 626 bool 627 628config HAVE_ARCH_SOFT_DIRTY 629 bool 630 631config HAVE_MOD_ARCH_SPECIFIC 632 bool 633 help 634 The arch uses struct mod_arch_specific to store data. Many arches 635 just need a simple module loader without arch specific data - those 636 should not enable this. 637 638config MODULES_USE_ELF_RELA 639 bool 640 help 641 Modules only use ELF RELA relocations. Modules with ELF REL 642 relocations will give an error. 643 644config MODULES_USE_ELF_REL 645 bool 646 help 647 Modules only use ELF REL relocations. Modules with ELF RELA 648 relocations will give an error. 649 650config HAVE_IRQ_EXIT_ON_IRQ_STACK 651 bool 652 help 653 Architecture doesn't only execute the irq handler on the irq stack 654 but also irq_exit(). This way we can process softirqs on this irq 655 stack instead of switching to a new one when we call __do_softirq() 656 in the end of an hardirq. 657 This spares a stack switch and improves cache usage on softirq 658 processing. 659 660config PGTABLE_LEVELS 661 int 662 default 2 663 664config ARCH_HAS_ELF_RANDOMIZE 665 bool 666 help 667 An architecture supports choosing randomized locations for 668 stack, mmap, brk, and ET_DYN. Defined functions: 669 - arch_mmap_rnd() 670 - arch_randomize_brk() 671 672config HAVE_ARCH_MMAP_RND_BITS 673 bool 674 help 675 An arch should select this symbol if it supports setting a variable 676 number of bits for use in establishing the base address for mmap 677 allocations, has MMU enabled and provides values for both: 678 - ARCH_MMAP_RND_BITS_MIN 679 - ARCH_MMAP_RND_BITS_MAX 680 681config HAVE_EXIT_THREAD 682 bool 683 help 684 An architecture implements exit_thread. 685 686config ARCH_MMAP_RND_BITS_MIN 687 int 688 689config ARCH_MMAP_RND_BITS_MAX 690 int 691 692config ARCH_MMAP_RND_BITS_DEFAULT 693 int 694 695config ARCH_MMAP_RND_BITS 696 int "Number of bits to use for ASLR of mmap base address" if EXPERT 697 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 698 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 699 default ARCH_MMAP_RND_BITS_MIN 700 depends on HAVE_ARCH_MMAP_RND_BITS 701 help 702 This value can be used to select the number of bits to use to 703 determine the random offset to the base address of vma regions 704 resulting from mmap allocations. This value will be bounded 705 by the architecture's minimum and maximum supported values. 706 707 This value can be changed after boot using the 708 /proc/sys/vm/mmap_rnd_bits tunable 709 710config HAVE_ARCH_MMAP_RND_COMPAT_BITS 711 bool 712 help 713 An arch should select this symbol if it supports running applications 714 in compatibility mode, supports setting a variable number of bits for 715 use in establishing the base address for mmap allocations, has MMU 716 enabled and provides values for both: 717 - ARCH_MMAP_RND_COMPAT_BITS_MIN 718 - ARCH_MMAP_RND_COMPAT_BITS_MAX 719 720config ARCH_MMAP_RND_COMPAT_BITS_MIN 721 int 722 723config ARCH_MMAP_RND_COMPAT_BITS_MAX 724 int 725 726config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 727 int 728 729config ARCH_MMAP_RND_COMPAT_BITS 730 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 731 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 732 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 733 default ARCH_MMAP_RND_COMPAT_BITS_MIN 734 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 735 help 736 This value can be used to select the number of bits to use to 737 determine the random offset to the base address of vma regions 738 resulting from mmap allocations for compatible applications This 739 value will be bounded by the architecture's minimum and maximum 740 supported values. 741 742 This value can be changed after boot using the 743 /proc/sys/vm/mmap_rnd_compat_bits tunable 744 745config HAVE_ARCH_COMPAT_MMAP_BASES 746 bool 747 help 748 This allows 64bit applications to invoke 32-bit mmap() syscall 749 and vice-versa 32-bit applications to call 64-bit mmap(). 750 Required for applications doing different bitness syscalls. 751 752# This allows to use a set of generic functions to determine mmap base 753# address by giving priority to top-down scheme only if the process 754# is not in legacy mode (compat task, unlimited stack size or 755# sysctl_legacy_va_layout). 756# Architecture that selects this option can provide its own version of: 757# - STACK_RND_MASK 758config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 759 bool 760 depends on MMU 761 select ARCH_HAS_ELF_RANDOMIZE 762 763config HAVE_STACK_VALIDATION 764 bool 765 help 766 Architecture supports the 'objtool check' host tool command, which 767 performs compile-time stack metadata validation. 768 769config HAVE_RELIABLE_STACKTRACE 770 bool 771 help 772 Architecture has either save_stack_trace_tsk_reliable() or 773 arch_stack_walk_reliable() function which only returns a stack trace 774 if it can guarantee the trace is reliable. 775 776config HAVE_ARCH_HASH 777 bool 778 default n 779 help 780 If this is set, the architecture provides an <asm/hash.h> 781 file which provides platform-specific implementations of some 782 functions in <linux/hash.h> or fs/namei.c. 783 784config HAVE_ARCH_NVRAM_OPS 785 bool 786 787config ISA_BUS_API 788 def_bool ISA 789 790# 791# ABI hall of shame 792# 793config CLONE_BACKWARDS 794 bool 795 help 796 Architecture has tls passed as the 4th argument of clone(2), 797 not the 5th one. 798 799config CLONE_BACKWARDS2 800 bool 801 help 802 Architecture has the first two arguments of clone(2) swapped. 803 804config CLONE_BACKWARDS3 805 bool 806 help 807 Architecture has tls passed as the 3rd argument of clone(2), 808 not the 5th one. 809 810config ODD_RT_SIGACTION 811 bool 812 help 813 Architecture has unusual rt_sigaction(2) arguments 814 815config OLD_SIGSUSPEND 816 bool 817 help 818 Architecture has old sigsuspend(2) syscall, of one-argument variety 819 820config OLD_SIGSUSPEND3 821 bool 822 help 823 Even weirder antique ABI - three-argument sigsuspend(2) 824 825config OLD_SIGACTION 826 bool 827 help 828 Architecture has old sigaction(2) syscall. Nope, not the same 829 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 830 but fairly different variant of sigaction(2), thanks to OSF/1 831 compatibility... 832 833config COMPAT_OLD_SIGACTION 834 bool 835 836config COMPAT_32BIT_TIME 837 bool "Provide system calls for 32-bit time_t" 838 default !64BIT || COMPAT 839 help 840 This enables 32 bit time_t support in addition to 64 bit time_t support. 841 This is relevant on all 32-bit architectures, and 64-bit architectures 842 as part of compat syscall handling. 843 844config ARCH_NO_PREEMPT 845 bool 846 847config ARCH_SUPPORTS_RT 848 bool 849 850config CPU_NO_EFFICIENT_FFS 851 def_bool n 852 853config HAVE_ARCH_VMAP_STACK 854 def_bool n 855 help 856 An arch should select this symbol if it can support kernel stacks 857 in vmalloc space. This means: 858 859 - vmalloc space must be large enough to hold many kernel stacks. 860 This may rule out many 32-bit architectures. 861 862 - Stacks in vmalloc space need to work reliably. For example, if 863 vmap page tables are created on demand, either this mechanism 864 needs to work while the stack points to a virtual address with 865 unpopulated page tables or arch code (switch_to() and switch_mm(), 866 most likely) needs to ensure that the stack's page table entries 867 are populated before running on a possibly unpopulated stack. 868 869 - If the stack overflows into a guard page, something reasonable 870 should happen. The definition of "reasonable" is flexible, but 871 instantly rebooting without logging anything would be unfriendly. 872 873config VMAP_STACK 874 default y 875 bool "Use a virtually-mapped stack" 876 depends on HAVE_ARCH_VMAP_STACK 877 depends on !KASAN || KASAN_VMALLOC 878 help 879 Enable this if you want the use virtually-mapped kernel stacks 880 with guard pages. This causes kernel stack overflows to be 881 caught immediately rather than causing difficult-to-diagnose 882 corruption. 883 884 To use this with KASAN, the architecture must support backing 885 virtual mappings with real shadow memory, and KASAN_VMALLOC must 886 be enabled. 887 888config ARCH_OPTIONAL_KERNEL_RWX 889 def_bool n 890 891config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 892 def_bool n 893 894config ARCH_HAS_STRICT_KERNEL_RWX 895 def_bool n 896 897config STRICT_KERNEL_RWX 898 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 899 depends on ARCH_HAS_STRICT_KERNEL_RWX 900 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 901 help 902 If this is set, kernel text and rodata memory will be made read-only, 903 and non-text memory will be made non-executable. This provides 904 protection against certain security exploits (e.g. executing the heap 905 or modifying text) 906 907 These features are considered standard security practice these days. 908 You should say Y here in almost all cases. 909 910config ARCH_HAS_STRICT_MODULE_RWX 911 def_bool n 912 913config STRICT_MODULE_RWX 914 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 915 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 916 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 917 help 918 If this is set, module text and rodata memory will be made read-only, 919 and non-text memory will be made non-executable. This provides 920 protection against certain security exploits (e.g. writing to text) 921 922# select if the architecture provides an asm/dma-direct.h header 923config ARCH_HAS_PHYS_TO_DMA 924 bool 925 926config HAVE_ARCH_COMPILER_H 927 bool 928 help 929 An architecture can select this if it provides an 930 asm/compiler.h header that should be included after 931 linux/compiler-*.h in order to override macro definitions that those 932 headers generally provide. 933 934config HAVE_ARCH_PREL32_RELOCATIONS 935 bool 936 help 937 May be selected by an architecture if it supports place-relative 938 32-bit relocations, both in the toolchain and in the module loader, 939 in which case relative references can be used in special sections 940 for PCI fixup, initcalls etc which are only half the size on 64 bit 941 architectures, and don't require runtime relocation on relocatable 942 kernels. 943 944config ARCH_USE_MEMREMAP_PROT 945 bool 946 947config LOCK_EVENT_COUNTS 948 bool "Locking event counts collection" 949 depends on DEBUG_FS 950 help 951 Enable light-weight counting of various locking related events 952 in the system with minimal performance impact. This reduces 953 the chance of application behavior change because of timing 954 differences. The counts are reported via debugfs. 955 956# Select if the architecture has support for applying RELR relocations. 957config ARCH_HAS_RELR 958 bool 959 960config RELR 961 bool "Use RELR relocation packing" 962 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 963 default y 964 help 965 Store the kernel's dynamic relocations in the RELR relocation packing 966 format. Requires a compatible linker (LLD supports this feature), as 967 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 968 are compatible). 969 970config ARCH_HAS_MEM_ENCRYPT 971 bool 972 973config HAVE_SPARSE_SYSCALL_NR 974 bool 975 help 976 An architecture should select this if its syscall numbering is sparse 977 to save space. For example, MIPS architecture has a syscall array with 978 entries at 4000, 5000 and 6000 locations. This option turns on syscall 979 related optimizations for a given architecture. 980 981config ARCH_HAS_VDSO_DATA 982 bool 983 984config HAVE_STATIC_CALL 985 bool 986 987config HAVE_STATIC_CALL_INLINE 988 bool 989 depends on HAVE_STATIC_CALL 990 991source "kernel/gcov/Kconfig" 992 993source "scripts/gcc-plugins/Kconfig" 994 995endmenu 996