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_WANT_IRQS_OFF_ACTIVATE_MM 424 bool 425 help 426 Temporary select until all architectures can be converted to have 427 irqs disabled over activate_mm. Architectures that do IPI based TLB 428 shootdowns should enable this. 429 430config ARCH_HAVE_NMI_SAFE_CMPXCHG 431 bool 432 433config HAVE_ALIGNED_STRUCT_PAGE 434 bool 435 help 436 This makes sure that struct pages are double word aligned and that 437 e.g. the SLUB allocator can perform double word atomic operations 438 on a struct page for better performance. However selecting this 439 might increase the size of a struct page by a word. 440 441config HAVE_CMPXCHG_LOCAL 442 bool 443 444config HAVE_CMPXCHG_DOUBLE 445 bool 446 447config ARCH_WEAK_RELEASE_ACQUIRE 448 bool 449 450config ARCH_WANT_IPC_PARSE_VERSION 451 bool 452 453config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 454 bool 455 456config ARCH_WANT_OLD_COMPAT_IPC 457 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 458 bool 459 460config HAVE_ARCH_SECCOMP 461 bool 462 help 463 An arch should select this symbol to support seccomp mode 1 (the fixed 464 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 465 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 466 - __NR_seccomp_read_32 467 - __NR_seccomp_write_32 468 - __NR_seccomp_exit_32 469 - __NR_seccomp_sigreturn_32 470 471config HAVE_ARCH_SECCOMP_FILTER 472 bool 473 select HAVE_ARCH_SECCOMP 474 help 475 An arch should select this symbol if it provides all of these things: 476 - all the requirements for HAVE_ARCH_SECCOMP 477 - syscall_get_arch() 478 - syscall_get_arguments() 479 - syscall_rollback() 480 - syscall_set_return_value() 481 - SIGSYS siginfo_t support 482 - secure_computing is called from a ptrace_event()-safe context 483 - secure_computing return value is checked and a return value of -1 484 results in the system call being skipped immediately. 485 - seccomp syscall wired up 486 487config SECCOMP 488 prompt "Enable seccomp to safely execute untrusted bytecode" 489 def_bool y 490 depends on HAVE_ARCH_SECCOMP 491 help 492 This kernel feature is useful for number crunching applications 493 that may need to handle untrusted bytecode during their 494 execution. By using pipes or other transports made available 495 to the process as file descriptors supporting the read/write 496 syscalls, it's possible to isolate those applications in their 497 own address space using seccomp. Once seccomp is enabled via 498 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 499 disabled and the task is only allowed to execute a few safe 500 syscalls defined by each seccomp mode. 501 502 If unsure, say Y. 503 504config SECCOMP_FILTER 505 def_bool y 506 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 507 help 508 Enable tasks to build secure computing environments defined 509 in terms of Berkeley Packet Filter programs which implement 510 task-defined system call filtering polices. 511 512 See Documentation/userspace-api/seccomp_filter.rst for details. 513 514config HAVE_ARCH_STACKLEAK 515 bool 516 help 517 An architecture should select this if it has the code which 518 fills the used part of the kernel stack with the STACKLEAK_POISON 519 value before returning from system calls. 520 521config HAVE_STACKPROTECTOR 522 bool 523 help 524 An arch should select this symbol if: 525 - it has implemented a stack canary (e.g. __stack_chk_guard) 526 527config STACKPROTECTOR 528 bool "Stack Protector buffer overflow detection" 529 depends on HAVE_STACKPROTECTOR 530 depends on $(cc-option,-fstack-protector) 531 default y 532 help 533 This option turns on the "stack-protector" GCC feature. This 534 feature puts, at the beginning of functions, a canary value on 535 the stack just before the return address, and validates 536 the value just before actually returning. Stack based buffer 537 overflows (that need to overwrite this return address) now also 538 overwrite the canary, which gets detected and the attack is then 539 neutralized via a kernel panic. 540 541 Functions will have the stack-protector canary logic added if they 542 have an 8-byte or larger character array on the stack. 543 544 This feature requires gcc version 4.2 or above, or a distribution 545 gcc with the feature backported ("-fstack-protector"). 546 547 On an x86 "defconfig" build, this feature adds canary checks to 548 about 3% of all kernel functions, which increases kernel code size 549 by about 0.3%. 550 551config STACKPROTECTOR_STRONG 552 bool "Strong Stack Protector" 553 depends on STACKPROTECTOR 554 depends on $(cc-option,-fstack-protector-strong) 555 default y 556 help 557 Functions will have the stack-protector canary logic added in any 558 of the following conditions: 559 560 - local variable's address used as part of the right hand side of an 561 assignment or function argument 562 - local variable is an array (or union containing an array), 563 regardless of array type or length 564 - uses register local variables 565 566 This feature requires gcc version 4.9 or above, or a distribution 567 gcc with the feature backported ("-fstack-protector-strong"). 568 569 On an x86 "defconfig" build, this feature adds canary checks to 570 about 20% of all kernel functions, which increases the kernel code 571 size by about 2%. 572 573config ARCH_SUPPORTS_SHADOW_CALL_STACK 574 bool 575 help 576 An architecture should select this if it supports Clang's Shadow 577 Call Stack and implements runtime support for shadow stack 578 switching. 579 580config SHADOW_CALL_STACK 581 bool "Clang Shadow Call Stack" 582 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 583 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 584 help 585 This option enables Clang's Shadow Call Stack, which uses a 586 shadow stack to protect function return addresses from being 587 overwritten by an attacker. More information can be found in 588 Clang's documentation: 589 590 https://clang.llvm.org/docs/ShadowCallStack.html 591 592 Note that security guarantees in the kernel differ from the 593 ones documented for user space. The kernel must store addresses 594 of shadow stacks in memory, which means an attacker capable of 595 reading and writing arbitrary memory may be able to locate them 596 and hijack control flow by modifying the stacks. 597 598config HAVE_ARCH_WITHIN_STACK_FRAMES 599 bool 600 help 601 An architecture should select this if it can walk the kernel stack 602 frames to determine if an object is part of either the arguments 603 or local variables (i.e. that it excludes saved return addresses, 604 and similar) by implementing an inline arch_within_stack_frames(), 605 which is used by CONFIG_HARDENED_USERCOPY. 606 607config HAVE_CONTEXT_TRACKING 608 bool 609 help 610 Provide kernel/user boundaries probes necessary for subsystems 611 that need it, such as userspace RCU extended quiescent state. 612 Syscalls need to be wrapped inside user_exit()-user_enter(), either 613 optimized behind static key or through the slow path using TIF_NOHZ 614 flag. Exceptions handlers must be wrapped as well. Irqs are already 615 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 616 handling on irq exit still need to be protected. 617 618config HAVE_TIF_NOHZ 619 bool 620 help 621 Arch relies on TIF_NOHZ and syscall slow path to implement context 622 tracking calls to user_enter()/user_exit(). 623 624config HAVE_VIRT_CPU_ACCOUNTING 625 bool 626 627config ARCH_HAS_SCALED_CPUTIME 628 bool 629 630config HAVE_VIRT_CPU_ACCOUNTING_GEN 631 bool 632 default y if 64BIT 633 help 634 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 635 Before enabling this option, arch code must be audited 636 to ensure there are no races in concurrent read/write of 637 cputime_t. For example, reading/writing 64-bit cputime_t on 638 some 32-bit arches may require multiple accesses, so proper 639 locking is needed to protect against concurrent accesses. 640 641 642config HAVE_IRQ_TIME_ACCOUNTING 643 bool 644 help 645 Archs need to ensure they use a high enough resolution clock to 646 support irq time accounting and then call enable_sched_clock_irqtime(). 647 648config HAVE_MOVE_PMD 649 bool 650 help 651 Archs that select this are able to move page tables at the PMD level. 652 653config HAVE_ARCH_TRANSPARENT_HUGEPAGE 654 bool 655 656config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 657 bool 658 659config HAVE_ARCH_HUGE_VMAP 660 bool 661 662config ARCH_WANT_HUGE_PMD_SHARE 663 bool 664 665config HAVE_ARCH_SOFT_DIRTY 666 bool 667 668config HAVE_MOD_ARCH_SPECIFIC 669 bool 670 help 671 The arch uses struct mod_arch_specific to store data. Many arches 672 just need a simple module loader without arch specific data - those 673 should not enable this. 674 675config MODULES_USE_ELF_RELA 676 bool 677 help 678 Modules only use ELF RELA relocations. Modules with ELF REL 679 relocations will give an error. 680 681config MODULES_USE_ELF_REL 682 bool 683 help 684 Modules only use ELF REL relocations. Modules with ELF RELA 685 relocations will give an error. 686 687config HAVE_IRQ_EXIT_ON_IRQ_STACK 688 bool 689 help 690 Architecture doesn't only execute the irq handler on the irq stack 691 but also irq_exit(). This way we can process softirqs on this irq 692 stack instead of switching to a new one when we call __do_softirq() 693 in the end of an hardirq. 694 This spares a stack switch and improves cache usage on softirq 695 processing. 696 697config PGTABLE_LEVELS 698 int 699 default 2 700 701config ARCH_HAS_ELF_RANDOMIZE 702 bool 703 help 704 An architecture supports choosing randomized locations for 705 stack, mmap, brk, and ET_DYN. Defined functions: 706 - arch_mmap_rnd() 707 - arch_randomize_brk() 708 709config HAVE_ARCH_MMAP_RND_BITS 710 bool 711 help 712 An arch should select this symbol if it supports setting a variable 713 number of bits for use in establishing the base address for mmap 714 allocations, has MMU enabled and provides values for both: 715 - ARCH_MMAP_RND_BITS_MIN 716 - ARCH_MMAP_RND_BITS_MAX 717 718config HAVE_EXIT_THREAD 719 bool 720 help 721 An architecture implements exit_thread. 722 723config ARCH_MMAP_RND_BITS_MIN 724 int 725 726config ARCH_MMAP_RND_BITS_MAX 727 int 728 729config ARCH_MMAP_RND_BITS_DEFAULT 730 int 731 732config ARCH_MMAP_RND_BITS 733 int "Number of bits to use for ASLR of mmap base address" if EXPERT 734 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 735 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 736 default ARCH_MMAP_RND_BITS_MIN 737 depends on HAVE_ARCH_MMAP_RND_BITS 738 help 739 This value can be used to select the number of bits to use to 740 determine the random offset to the base address of vma regions 741 resulting from mmap allocations. This value will be bounded 742 by the architecture's minimum and maximum supported values. 743 744 This value can be changed after boot using the 745 /proc/sys/vm/mmap_rnd_bits tunable 746 747config HAVE_ARCH_MMAP_RND_COMPAT_BITS 748 bool 749 help 750 An arch should select this symbol if it supports running applications 751 in compatibility mode, supports setting a variable number of bits for 752 use in establishing the base address for mmap allocations, has MMU 753 enabled and provides values for both: 754 - ARCH_MMAP_RND_COMPAT_BITS_MIN 755 - ARCH_MMAP_RND_COMPAT_BITS_MAX 756 757config ARCH_MMAP_RND_COMPAT_BITS_MIN 758 int 759 760config ARCH_MMAP_RND_COMPAT_BITS_MAX 761 int 762 763config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 764 int 765 766config ARCH_MMAP_RND_COMPAT_BITS 767 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 768 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 769 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 770 default ARCH_MMAP_RND_COMPAT_BITS_MIN 771 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 772 help 773 This value can be used to select the number of bits to use to 774 determine the random offset to the base address of vma regions 775 resulting from mmap allocations for compatible applications This 776 value will be bounded by the architecture's minimum and maximum 777 supported values. 778 779 This value can be changed after boot using the 780 /proc/sys/vm/mmap_rnd_compat_bits tunable 781 782config HAVE_ARCH_COMPAT_MMAP_BASES 783 bool 784 help 785 This allows 64bit applications to invoke 32-bit mmap() syscall 786 and vice-versa 32-bit applications to call 64-bit mmap(). 787 Required for applications doing different bitness syscalls. 788 789# This allows to use a set of generic functions to determine mmap base 790# address by giving priority to top-down scheme only if the process 791# is not in legacy mode (compat task, unlimited stack size or 792# sysctl_legacy_va_layout). 793# Architecture that selects this option can provide its own version of: 794# - STACK_RND_MASK 795config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 796 bool 797 depends on MMU 798 select ARCH_HAS_ELF_RANDOMIZE 799 800config HAVE_STACK_VALIDATION 801 bool 802 help 803 Architecture supports the 'objtool check' host tool command, which 804 performs compile-time stack metadata validation. 805 806config HAVE_RELIABLE_STACKTRACE 807 bool 808 help 809 Architecture has either save_stack_trace_tsk_reliable() or 810 arch_stack_walk_reliable() function which only returns a stack trace 811 if it can guarantee the trace is reliable. 812 813config HAVE_ARCH_HASH 814 bool 815 default n 816 help 817 If this is set, the architecture provides an <asm/hash.h> 818 file which provides platform-specific implementations of some 819 functions in <linux/hash.h> or fs/namei.c. 820 821config HAVE_ARCH_NVRAM_OPS 822 bool 823 824config ISA_BUS_API 825 def_bool ISA 826 827# 828# ABI hall of shame 829# 830config CLONE_BACKWARDS 831 bool 832 help 833 Architecture has tls passed as the 4th argument of clone(2), 834 not the 5th one. 835 836config CLONE_BACKWARDS2 837 bool 838 help 839 Architecture has the first two arguments of clone(2) swapped. 840 841config CLONE_BACKWARDS3 842 bool 843 help 844 Architecture has tls passed as the 3rd argument of clone(2), 845 not the 5th one. 846 847config ODD_RT_SIGACTION 848 bool 849 help 850 Architecture has unusual rt_sigaction(2) arguments 851 852config OLD_SIGSUSPEND 853 bool 854 help 855 Architecture has old sigsuspend(2) syscall, of one-argument variety 856 857config OLD_SIGSUSPEND3 858 bool 859 help 860 Even weirder antique ABI - three-argument sigsuspend(2) 861 862config OLD_SIGACTION 863 bool 864 help 865 Architecture has old sigaction(2) syscall. Nope, not the same 866 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 867 but fairly different variant of sigaction(2), thanks to OSF/1 868 compatibility... 869 870config COMPAT_OLD_SIGACTION 871 bool 872 873config COMPAT_32BIT_TIME 874 bool "Provide system calls for 32-bit time_t" 875 default !64BIT || COMPAT 876 help 877 This enables 32 bit time_t support in addition to 64 bit time_t support. 878 This is relevant on all 32-bit architectures, and 64-bit architectures 879 as part of compat syscall handling. 880 881config ARCH_NO_PREEMPT 882 bool 883 884config ARCH_SUPPORTS_RT 885 bool 886 887config CPU_NO_EFFICIENT_FFS 888 def_bool n 889 890config HAVE_ARCH_VMAP_STACK 891 def_bool n 892 help 893 An arch should select this symbol if it can support kernel stacks 894 in vmalloc space. This means: 895 896 - vmalloc space must be large enough to hold many kernel stacks. 897 This may rule out many 32-bit architectures. 898 899 - Stacks in vmalloc space need to work reliably. For example, if 900 vmap page tables are created on demand, either this mechanism 901 needs to work while the stack points to a virtual address with 902 unpopulated page tables or arch code (switch_to() and switch_mm(), 903 most likely) needs to ensure that the stack's page table entries 904 are populated before running on a possibly unpopulated stack. 905 906 - If the stack overflows into a guard page, something reasonable 907 should happen. The definition of "reasonable" is flexible, but 908 instantly rebooting without logging anything would be unfriendly. 909 910config VMAP_STACK 911 default y 912 bool "Use a virtually-mapped stack" 913 depends on HAVE_ARCH_VMAP_STACK 914 depends on !KASAN || KASAN_VMALLOC 915 help 916 Enable this if you want the use virtually-mapped kernel stacks 917 with guard pages. This causes kernel stack overflows to be 918 caught immediately rather than causing difficult-to-diagnose 919 corruption. 920 921 To use this with KASAN, the architecture must support backing 922 virtual mappings with real shadow memory, and KASAN_VMALLOC must 923 be enabled. 924 925config ARCH_OPTIONAL_KERNEL_RWX 926 def_bool n 927 928config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 929 def_bool n 930 931config ARCH_HAS_STRICT_KERNEL_RWX 932 def_bool n 933 934config STRICT_KERNEL_RWX 935 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 936 depends on ARCH_HAS_STRICT_KERNEL_RWX 937 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 938 help 939 If this is set, kernel text and rodata memory will be made read-only, 940 and non-text memory will be made non-executable. This provides 941 protection against certain security exploits (e.g. executing the heap 942 or modifying text) 943 944 These features are considered standard security practice these days. 945 You should say Y here in almost all cases. 946 947config ARCH_HAS_STRICT_MODULE_RWX 948 def_bool n 949 950config STRICT_MODULE_RWX 951 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 952 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 953 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 954 help 955 If this is set, module text and rodata memory will be made read-only, 956 and non-text memory will be made non-executable. This provides 957 protection against certain security exploits (e.g. writing to text) 958 959# select if the architecture provides an asm/dma-direct.h header 960config ARCH_HAS_PHYS_TO_DMA 961 bool 962 963config HAVE_ARCH_COMPILER_H 964 bool 965 help 966 An architecture can select this if it provides an 967 asm/compiler.h header that should be included after 968 linux/compiler-*.h in order to override macro definitions that those 969 headers generally provide. 970 971config HAVE_ARCH_PREL32_RELOCATIONS 972 bool 973 help 974 May be selected by an architecture if it supports place-relative 975 32-bit relocations, both in the toolchain and in the module loader, 976 in which case relative references can be used in special sections 977 for PCI fixup, initcalls etc which are only half the size on 64 bit 978 architectures, and don't require runtime relocation on relocatable 979 kernels. 980 981config ARCH_USE_MEMREMAP_PROT 982 bool 983 984config LOCK_EVENT_COUNTS 985 bool "Locking event counts collection" 986 depends on DEBUG_FS 987 help 988 Enable light-weight counting of various locking related events 989 in the system with minimal performance impact. This reduces 990 the chance of application behavior change because of timing 991 differences. The counts are reported via debugfs. 992 993# Select if the architecture has support for applying RELR relocations. 994config ARCH_HAS_RELR 995 bool 996 997config RELR 998 bool "Use RELR relocation packing" 999 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1000 default y 1001 help 1002 Store the kernel's dynamic relocations in the RELR relocation packing 1003 format. Requires a compatible linker (LLD supports this feature), as 1004 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1005 are compatible). 1006 1007config ARCH_HAS_MEM_ENCRYPT 1008 bool 1009 1010config HAVE_SPARSE_SYSCALL_NR 1011 bool 1012 help 1013 An architecture should select this if its syscall numbering is sparse 1014 to save space. For example, MIPS architecture has a syscall array with 1015 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1016 related optimizations for a given architecture. 1017 1018config ARCH_HAS_VDSO_DATA 1019 bool 1020 1021config HAVE_STATIC_CALL 1022 bool 1023 1024config HAVE_STATIC_CALL_INLINE 1025 bool 1026 depends on HAVE_STATIC_CALL 1027 1028source "kernel/gcov/Kconfig" 1029 1030source "scripts/gcc-plugins/Kconfig" 1031 1032endmenu 1033