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