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 HAVE_IMA_KEXEC 22 bool 23 24config HOTPLUG_SMT 25 bool 26 27config OPROFILE 28 tristate "OProfile system profiling" 29 depends on PROFILING 30 depends on HAVE_OPROFILE 31 select RING_BUFFER 32 select RING_BUFFER_ALLOW_SWAP 33 help 34 OProfile is a profiling system capable of profiling the 35 whole system, include the kernel, kernel modules, libraries, 36 and applications. 37 38 If unsure, say N. 39 40config OPROFILE_EVENT_MULTIPLEX 41 bool "OProfile multiplexing support (EXPERIMENTAL)" 42 default n 43 depends on OPROFILE && X86 44 help 45 The number of hardware counters is limited. The multiplexing 46 feature enables OProfile to gather more events than counters 47 are provided by the hardware. This is realized by switching 48 between events at a user specified time interval. 49 50 If unsure, say N. 51 52config HAVE_OPROFILE 53 bool 54 55config OPROFILE_NMI_TIMER 56 def_bool y 57 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 58 59config KPROBES 60 bool "Kprobes" 61 depends on MODULES 62 depends on HAVE_KPROBES 63 select KALLSYMS 64 help 65 Kprobes allows you to trap at almost any kernel address and 66 execute a callback function. register_kprobe() establishes 67 a probepoint and specifies the callback. Kprobes is useful 68 for kernel debugging, non-intrusive instrumentation and testing. 69 If in doubt, say "N". 70 71config JUMP_LABEL 72 bool "Optimize very unlikely/likely branches" 73 depends on HAVE_ARCH_JUMP_LABEL 74 depends on CC_HAS_ASM_GOTO 75 help 76 This option enables a transparent branch optimization that 77 makes certain almost-always-true or almost-always-false branch 78 conditions even cheaper to execute within the kernel. 79 80 Certain performance-sensitive kernel code, such as trace points, 81 scheduler functionality, networking code and KVM have such 82 branches and include support for this optimization technique. 83 84 If it is detected that the compiler has support for "asm goto", 85 the kernel will compile such branches with just a nop 86 instruction. When the condition flag is toggled to true, the 87 nop will be converted to a jump instruction to execute the 88 conditional block of instructions. 89 90 This technique lowers overhead and stress on the branch prediction 91 of the processor and generally makes the kernel faster. The update 92 of the condition is slower, but those are always very rare. 93 94 ( On 32-bit x86, the necessary options added to the compiler 95 flags may increase the size of the kernel slightly. ) 96 97config STATIC_KEYS_SELFTEST 98 bool "Static key selftest" 99 depends on JUMP_LABEL 100 help 101 Boot time self-test of the branch patching code. 102 103config OPTPROBES 104 def_bool y 105 depends on KPROBES && HAVE_OPTPROBES 106 select TASKS_RCU if PREEMPT 107 108config KPROBES_ON_FTRACE 109 def_bool y 110 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 111 depends on DYNAMIC_FTRACE_WITH_REGS 112 help 113 If function tracer is enabled and the arch supports full 114 passing of pt_regs to function tracing, then kprobes can 115 optimize on top of function tracing. 116 117config UPROBES 118 def_bool n 119 depends on ARCH_SUPPORTS_UPROBES 120 help 121 Uprobes is the user-space counterpart to kprobes: they 122 enable instrumentation applications (such as 'perf probe') 123 to establish unintrusive probes in user-space binaries and 124 libraries, by executing handler functions when the probes 125 are hit by user-space applications. 126 127 ( These probes come in the form of single-byte breakpoints, 128 managed by the kernel and kept transparent to the probed 129 application. ) 130 131config HAVE_64BIT_ALIGNED_ACCESS 132 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 133 help 134 Some architectures require 64 bit accesses to be 64 bit 135 aligned, which also requires structs containing 64 bit values 136 to be 64 bit aligned too. This includes some 32 bit 137 architectures which can do 64 bit accesses, as well as 64 bit 138 architectures without unaligned access. 139 140 This symbol should be selected by an architecture if 64 bit 141 accesses are required to be 64 bit aligned in this way even 142 though it is not a 64 bit architecture. 143 144 See Documentation/unaligned-memory-access.txt for more 145 information on the topic of unaligned memory accesses. 146 147config HAVE_EFFICIENT_UNALIGNED_ACCESS 148 bool 149 help 150 Some architectures are unable to perform unaligned accesses 151 without the use of get_unaligned/put_unaligned. Others are 152 unable to perform such accesses efficiently (e.g. trap on 153 unaligned access and require fixing it up in the exception 154 handler.) 155 156 This symbol should be selected by an architecture if it can 157 perform unaligned accesses efficiently to allow different 158 code paths to be selected for these cases. Some network 159 drivers, for example, could opt to not fix up alignment 160 problems with received packets if doing so would not help 161 much. 162 163 See Documentation/unaligned-memory-access.txt for more 164 information on the topic of unaligned memory accesses. 165 166config ARCH_USE_BUILTIN_BSWAP 167 bool 168 help 169 Modern versions of GCC (since 4.4) have builtin functions 170 for handling byte-swapping. Using these, instead of the old 171 inline assembler that the architecture code provides in the 172 __arch_bswapXX() macros, allows the compiler to see what's 173 happening and offers more opportunity for optimisation. In 174 particular, the compiler will be able to combine the byteswap 175 with a nearby load or store and use load-and-swap or 176 store-and-swap instructions if the architecture has them. It 177 should almost *never* result in code which is worse than the 178 hand-coded assembler in <asm/swab.h>. But just in case it 179 does, the use of the builtins is optional. 180 181 Any architecture with load-and-swap or store-and-swap 182 instructions should set this. And it shouldn't hurt to set it 183 on architectures that don't have such instructions. 184 185config KRETPROBES 186 def_bool y 187 depends on KPROBES && HAVE_KRETPROBES 188 189config USER_RETURN_NOTIFIER 190 bool 191 depends on HAVE_USER_RETURN_NOTIFIER 192 help 193 Provide a kernel-internal notification when a cpu is about to 194 switch to user mode. 195 196config HAVE_IOREMAP_PROT 197 bool 198 199config HAVE_KPROBES 200 bool 201 202config HAVE_KRETPROBES 203 bool 204 205config HAVE_OPTPROBES 206 bool 207 208config HAVE_KPROBES_ON_FTRACE 209 bool 210 211config HAVE_FUNCTION_ERROR_INJECTION 212 bool 213 214config HAVE_NMI 215 bool 216 217# 218# An arch should select this if it provides all these things: 219# 220# task_pt_regs() in asm/processor.h or asm/ptrace.h 221# arch_has_single_step() if there is hardware single-step support 222# arch_has_block_step() if there is hardware block-step support 223# asm/syscall.h supplying asm-generic/syscall.h interface 224# linux/regset.h user_regset interfaces 225# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 226# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 227# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 228# signal delivery calls tracehook_signal_handler() 229# 230config HAVE_ARCH_TRACEHOOK 231 bool 232 233config HAVE_DMA_CONTIGUOUS 234 bool 235 236config GENERIC_SMP_IDLE_THREAD 237 bool 238 239config GENERIC_IDLE_POLL_SETUP 240 bool 241 242config ARCH_HAS_FORTIFY_SOURCE 243 bool 244 help 245 An architecture should select this when it can successfully 246 build and run with CONFIG_FORTIFY_SOURCE. 247 248# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 249config ARCH_HAS_SET_MEMORY 250 bool 251 252# Select if arch init_task must go in the __init_task_data section 253config ARCH_TASK_STRUCT_ON_STACK 254 bool 255 256# Select if arch has its private alloc_task_struct() function 257config ARCH_TASK_STRUCT_ALLOCATOR 258 bool 259 260config HAVE_ARCH_THREAD_STRUCT_WHITELIST 261 bool 262 depends on !ARCH_TASK_STRUCT_ALLOCATOR 263 help 264 An architecture should select this to provide hardened usercopy 265 knowledge about what region of the thread_struct should be 266 whitelisted for copying to userspace. Normally this is only the 267 FPU registers. Specifically, arch_thread_struct_whitelist() 268 should be implemented. Without this, the entire thread_struct 269 field in task_struct will be left whitelisted. 270 271# Select if arch has its private alloc_thread_stack() function 272config ARCH_THREAD_STACK_ALLOCATOR 273 bool 274 275# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 276config ARCH_WANTS_DYNAMIC_TASK_STRUCT 277 bool 278 279config HAVE_REGS_AND_STACK_ACCESS_API 280 bool 281 help 282 This symbol should be selected by an architecure if it supports 283 the API needed to access registers and stack entries from pt_regs, 284 declared in asm/ptrace.h 285 For example the kprobes-based event tracer needs this API. 286 287config HAVE_RSEQ 288 bool 289 depends on HAVE_REGS_AND_STACK_ACCESS_API 290 help 291 This symbol should be selected by an architecture if it 292 supports an implementation of restartable sequences. 293 294config HAVE_FUNCTION_ARG_ACCESS_API 295 bool 296 help 297 This symbol should be selected by an architecure if it supports 298 the API needed to access function arguments from pt_regs, 299 declared in asm/ptrace.h 300 301config HAVE_CLK 302 bool 303 help 304 The <linux/clk.h> calls support software clock gating and 305 thus are a key power management tool on many systems. 306 307config HAVE_HW_BREAKPOINT 308 bool 309 depends on PERF_EVENTS 310 311config HAVE_MIXED_BREAKPOINTS_REGS 312 bool 313 depends on HAVE_HW_BREAKPOINT 314 help 315 Depending on the arch implementation of hardware breakpoints, 316 some of them have separate registers for data and instruction 317 breakpoints addresses, others have mixed registers to store 318 them but define the access type in a control register. 319 Select this option if your arch implements breakpoints under the 320 latter fashion. 321 322config HAVE_USER_RETURN_NOTIFIER 323 bool 324 325config HAVE_PERF_EVENTS_NMI 326 bool 327 help 328 System hardware can generate an NMI using the perf event 329 subsystem. Also has support for calculating CPU cycle events 330 to determine how many clock cycles in a given period. 331 332config HAVE_HARDLOCKUP_DETECTOR_PERF 333 bool 334 depends on HAVE_PERF_EVENTS_NMI 335 help 336 The arch chooses to use the generic perf-NMI-based hardlockup 337 detector. Must define HAVE_PERF_EVENTS_NMI. 338 339config HAVE_NMI_WATCHDOG 340 depends on HAVE_NMI 341 bool 342 help 343 The arch provides a low level NMI watchdog. It provides 344 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 345 346config HAVE_HARDLOCKUP_DETECTOR_ARCH 347 bool 348 select HAVE_NMI_WATCHDOG 349 help 350 The arch chooses to provide its own hardlockup detector, which is 351 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 352 interfaces and parameters provided by hardlockup detector subsystem. 353 354config HAVE_PERF_REGS 355 bool 356 help 357 Support selective register dumps for perf events. This includes 358 bit-mapping of each registers and a unique architecture id. 359 360config HAVE_PERF_USER_STACK_DUMP 361 bool 362 help 363 Support user stack dumps for perf event samples. This needs 364 access to the user stack pointer which is not unified across 365 architectures. 366 367config HAVE_ARCH_JUMP_LABEL 368 bool 369 370config HAVE_ARCH_JUMP_LABEL_RELATIVE 371 bool 372 373config HAVE_RCU_TABLE_FREE 374 bool 375 376config HAVE_RCU_TABLE_INVALIDATE 377 bool 378 379config ARCH_HAVE_NMI_SAFE_CMPXCHG 380 bool 381 382config HAVE_ALIGNED_STRUCT_PAGE 383 bool 384 help 385 This makes sure that struct pages are double word aligned and that 386 e.g. the SLUB allocator can perform double word atomic operations 387 on a struct page for better performance. However selecting this 388 might increase the size of a struct page by a word. 389 390config HAVE_CMPXCHG_LOCAL 391 bool 392 393config HAVE_CMPXCHG_DOUBLE 394 bool 395 396config ARCH_WEAK_RELEASE_ACQUIRE 397 bool 398 399config ARCH_WANT_IPC_PARSE_VERSION 400 bool 401 402config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 403 bool 404 405config ARCH_WANT_OLD_COMPAT_IPC 406 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 407 bool 408 409config HAVE_ARCH_SECCOMP_FILTER 410 bool 411 help 412 An arch should select this symbol if it provides all of these things: 413 - syscall_get_arch() 414 - syscall_get_arguments() 415 - syscall_rollback() 416 - syscall_set_return_value() 417 - SIGSYS siginfo_t support 418 - secure_computing is called from a ptrace_event()-safe context 419 - secure_computing return value is checked and a return value of -1 420 results in the system call being skipped immediately. 421 - seccomp syscall wired up 422 423config SECCOMP_FILTER 424 def_bool y 425 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 426 help 427 Enable tasks to build secure computing environments defined 428 in terms of Berkeley Packet Filter programs which implement 429 task-defined system call filtering polices. 430 431 See Documentation/userspace-api/seccomp_filter.rst for details. 432 433config HAVE_ARCH_STACKLEAK 434 bool 435 help 436 An architecture should select this if it has the code which 437 fills the used part of the kernel stack with the STACKLEAK_POISON 438 value before returning from system calls. 439 440config HAVE_STACKPROTECTOR 441 bool 442 help 443 An arch should select this symbol if: 444 - it has implemented a stack canary (e.g. __stack_chk_guard) 445 446config CC_HAS_STACKPROTECTOR_NONE 447 def_bool $(cc-option,-fno-stack-protector) 448 449config STACKPROTECTOR 450 bool "Stack Protector buffer overflow detection" 451 depends on HAVE_STACKPROTECTOR 452 depends on $(cc-option,-fstack-protector) 453 default y 454 help 455 This option turns on the "stack-protector" GCC feature. This 456 feature puts, at the beginning of functions, a canary value on 457 the stack just before the return address, and validates 458 the value just before actually returning. Stack based buffer 459 overflows (that need to overwrite this return address) now also 460 overwrite the canary, which gets detected and the attack is then 461 neutralized via a kernel panic. 462 463 Functions will have the stack-protector canary logic added if they 464 have an 8-byte or larger character array on the stack. 465 466 This feature requires gcc version 4.2 or above, or a distribution 467 gcc with the feature backported ("-fstack-protector"). 468 469 On an x86 "defconfig" build, this feature adds canary checks to 470 about 3% of all kernel functions, which increases kernel code size 471 by about 0.3%. 472 473config STACKPROTECTOR_STRONG 474 bool "Strong Stack Protector" 475 depends on STACKPROTECTOR 476 depends on $(cc-option,-fstack-protector-strong) 477 default y 478 help 479 Functions will have the stack-protector canary logic added in any 480 of the following conditions: 481 482 - local variable's address used as part of the right hand side of an 483 assignment or function argument 484 - local variable is an array (or union containing an array), 485 regardless of array type or length 486 - uses register local variables 487 488 This feature requires gcc version 4.9 or above, or a distribution 489 gcc with the feature backported ("-fstack-protector-strong"). 490 491 On an x86 "defconfig" build, this feature adds canary checks to 492 about 20% of all kernel functions, which increases the kernel code 493 size by about 2%. 494 495config HAVE_ARCH_WITHIN_STACK_FRAMES 496 bool 497 help 498 An architecture should select this if it can walk the kernel stack 499 frames to determine if an object is part of either the arguments 500 or local variables (i.e. that it excludes saved return addresses, 501 and similar) by implementing an inline arch_within_stack_frames(), 502 which is used by CONFIG_HARDENED_USERCOPY. 503 504config HAVE_CONTEXT_TRACKING 505 bool 506 help 507 Provide kernel/user boundaries probes necessary for subsystems 508 that need it, such as userspace RCU extended quiescent state. 509 Syscalls need to be wrapped inside user_exit()-user_enter() through 510 the slow path using TIF_NOHZ flag. Exceptions handlers must be 511 wrapped as well. Irqs are already protected inside 512 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 513 irq exit still need to be protected. 514 515config HAVE_VIRT_CPU_ACCOUNTING 516 bool 517 518config ARCH_HAS_SCALED_CPUTIME 519 bool 520 521config HAVE_VIRT_CPU_ACCOUNTING_GEN 522 bool 523 default y if 64BIT 524 help 525 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 526 Before enabling this option, arch code must be audited 527 to ensure there are no races in concurrent read/write of 528 cputime_t. For example, reading/writing 64-bit cputime_t on 529 some 32-bit arches may require multiple accesses, so proper 530 locking is needed to protect against concurrent accesses. 531 532 533config HAVE_IRQ_TIME_ACCOUNTING 534 bool 535 help 536 Archs need to ensure they use a high enough resolution clock to 537 support irq time accounting and then call enable_sched_clock_irqtime(). 538 539config HAVE_MOVE_PMD 540 bool 541 help 542 Archs that select this are able to move page tables at the PMD level. 543 544config HAVE_ARCH_TRANSPARENT_HUGEPAGE 545 bool 546 547config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 548 bool 549 550config HAVE_ARCH_HUGE_VMAP 551 bool 552 553config HAVE_ARCH_SOFT_DIRTY 554 bool 555 556config HAVE_MOD_ARCH_SPECIFIC 557 bool 558 help 559 The arch uses struct mod_arch_specific to store data. Many arches 560 just need a simple module loader without arch specific data - those 561 should not enable this. 562 563config MODULES_USE_ELF_RELA 564 bool 565 help 566 Modules only use ELF RELA relocations. Modules with ELF REL 567 relocations will give an error. 568 569config MODULES_USE_ELF_REL 570 bool 571 help 572 Modules only use ELF REL relocations. Modules with ELF RELA 573 relocations will give an error. 574 575config HAVE_IRQ_EXIT_ON_IRQ_STACK 576 bool 577 help 578 Architecture doesn't only execute the irq handler on the irq stack 579 but also irq_exit(). This way we can process softirqs on this irq 580 stack instead of switching to a new one when we call __do_softirq() 581 in the end of an hardirq. 582 This spares a stack switch and improves cache usage on softirq 583 processing. 584 585config PGTABLE_LEVELS 586 int 587 default 2 588 589config ARCH_HAS_ELF_RANDOMIZE 590 bool 591 help 592 An architecture supports choosing randomized locations for 593 stack, mmap, brk, and ET_DYN. Defined functions: 594 - arch_mmap_rnd() 595 - arch_randomize_brk() 596 597config HAVE_ARCH_MMAP_RND_BITS 598 bool 599 help 600 An arch should select this symbol if it supports setting a variable 601 number of bits for use in establishing the base address for mmap 602 allocations, has MMU enabled and provides values for both: 603 - ARCH_MMAP_RND_BITS_MIN 604 - ARCH_MMAP_RND_BITS_MAX 605 606config HAVE_EXIT_THREAD 607 bool 608 help 609 An architecture implements exit_thread. 610 611config ARCH_MMAP_RND_BITS_MIN 612 int 613 614config ARCH_MMAP_RND_BITS_MAX 615 int 616 617config ARCH_MMAP_RND_BITS_DEFAULT 618 int 619 620config ARCH_MMAP_RND_BITS 621 int "Number of bits to use for ASLR of mmap base address" if EXPERT 622 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 623 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 624 default ARCH_MMAP_RND_BITS_MIN 625 depends on HAVE_ARCH_MMAP_RND_BITS 626 help 627 This value can be used to select the number of bits to use to 628 determine the random offset to the base address of vma regions 629 resulting from mmap allocations. This value will be bounded 630 by the architecture's minimum and maximum supported values. 631 632 This value can be changed after boot using the 633 /proc/sys/vm/mmap_rnd_bits tunable 634 635config HAVE_ARCH_MMAP_RND_COMPAT_BITS 636 bool 637 help 638 An arch should select this symbol if it supports running applications 639 in compatibility mode, supports setting a variable number of bits for 640 use in establishing the base address for mmap allocations, has MMU 641 enabled and provides values for both: 642 - ARCH_MMAP_RND_COMPAT_BITS_MIN 643 - ARCH_MMAP_RND_COMPAT_BITS_MAX 644 645config ARCH_MMAP_RND_COMPAT_BITS_MIN 646 int 647 648config ARCH_MMAP_RND_COMPAT_BITS_MAX 649 int 650 651config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 652 int 653 654config ARCH_MMAP_RND_COMPAT_BITS 655 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 656 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 657 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 658 default ARCH_MMAP_RND_COMPAT_BITS_MIN 659 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 660 help 661 This value can be used to select the number of bits to use to 662 determine the random offset to the base address of vma regions 663 resulting from mmap allocations for compatible applications This 664 value will be bounded by the architecture's minimum and maximum 665 supported values. 666 667 This value can be changed after boot using the 668 /proc/sys/vm/mmap_rnd_compat_bits tunable 669 670config HAVE_ARCH_COMPAT_MMAP_BASES 671 bool 672 help 673 This allows 64bit applications to invoke 32-bit mmap() syscall 674 and vice-versa 32-bit applications to call 64-bit mmap(). 675 Required for applications doing different bitness syscalls. 676 677config HAVE_COPY_THREAD_TLS 678 bool 679 help 680 Architecture provides copy_thread_tls to accept tls argument via 681 normal C parameter passing, rather than extracting the syscall 682 argument from pt_regs. 683 684config HAVE_STACK_VALIDATION 685 bool 686 help 687 Architecture supports the 'objtool check' host tool command, which 688 performs compile-time stack metadata validation. 689 690config HAVE_RELIABLE_STACKTRACE 691 bool 692 help 693 Architecture has a save_stack_trace_tsk_reliable() function which 694 only returns a stack trace if it can guarantee the trace is reliable. 695 696config HAVE_ARCH_HASH 697 bool 698 default n 699 help 700 If this is set, the architecture provides an <asm/hash.h> 701 file which provides platform-specific implementations of some 702 functions in <linux/hash.h> or fs/namei.c. 703 704config ISA_BUS_API 705 def_bool ISA 706 707# 708# ABI hall of shame 709# 710config CLONE_BACKWARDS 711 bool 712 help 713 Architecture has tls passed as the 4th argument of clone(2), 714 not the 5th one. 715 716config CLONE_BACKWARDS2 717 bool 718 help 719 Architecture has the first two arguments of clone(2) swapped. 720 721config CLONE_BACKWARDS3 722 bool 723 help 724 Architecture has tls passed as the 3rd argument of clone(2), 725 not the 5th one. 726 727config ODD_RT_SIGACTION 728 bool 729 help 730 Architecture has unusual rt_sigaction(2) arguments 731 732config OLD_SIGSUSPEND 733 bool 734 help 735 Architecture has old sigsuspend(2) syscall, of one-argument variety 736 737config OLD_SIGSUSPEND3 738 bool 739 help 740 Even weirder antique ABI - three-argument sigsuspend(2) 741 742config OLD_SIGACTION 743 bool 744 help 745 Architecture has old sigaction(2) syscall. Nope, not the same 746 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 747 but fairly different variant of sigaction(2), thanks to OSF/1 748 compatibility... 749 750config COMPAT_OLD_SIGACTION 751 bool 752 753config 64BIT_TIME 754 def_bool ARCH_HAS_64BIT_TIME 755 help 756 This should be selected by all architectures that need to support 757 new system calls with a 64-bit time_t. This is relevant on all 32-bit 758 architectures, and 64-bit architectures as part of compat syscall 759 handling. 760 761config COMPAT_32BIT_TIME 762 def_bool (!64BIT && 64BIT_TIME) || COMPAT 763 help 764 This enables 32 bit time_t support in addition to 64 bit time_t support. 765 This is relevant on all 32-bit architectures, and 64-bit architectures 766 as part of compat syscall handling. 767 768config ARCH_NO_COHERENT_DMA_MMAP 769 bool 770 771config ARCH_NO_PREEMPT 772 bool 773 774config CPU_NO_EFFICIENT_FFS 775 def_bool n 776 777config HAVE_ARCH_VMAP_STACK 778 def_bool n 779 help 780 An arch should select this symbol if it can support kernel stacks 781 in vmalloc space. This means: 782 783 - vmalloc space must be large enough to hold many kernel stacks. 784 This may rule out many 32-bit architectures. 785 786 - Stacks in vmalloc space need to work reliably. For example, if 787 vmap page tables are created on demand, either this mechanism 788 needs to work while the stack points to a virtual address with 789 unpopulated page tables or arch code (switch_to() and switch_mm(), 790 most likely) needs to ensure that the stack's page table entries 791 are populated before running on a possibly unpopulated stack. 792 793 - If the stack overflows into a guard page, something reasonable 794 should happen. The definition of "reasonable" is flexible, but 795 instantly rebooting without logging anything would be unfriendly. 796 797config VMAP_STACK 798 default y 799 bool "Use a virtually-mapped stack" 800 depends on HAVE_ARCH_VMAP_STACK && !KASAN 801 ---help--- 802 Enable this if you want the use virtually-mapped kernel stacks 803 with guard pages. This causes kernel stack overflows to be 804 caught immediately rather than causing difficult-to-diagnose 805 corruption. 806 807 This is presently incompatible with KASAN because KASAN expects 808 the stack to map directly to the KASAN shadow map using a formula 809 that is incorrect if the stack is in vmalloc space. 810 811config ARCH_OPTIONAL_KERNEL_RWX 812 def_bool n 813 814config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 815 def_bool n 816 817config ARCH_HAS_STRICT_KERNEL_RWX 818 def_bool n 819 820config STRICT_KERNEL_RWX 821 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 822 depends on ARCH_HAS_STRICT_KERNEL_RWX 823 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 824 help 825 If this is set, kernel text and rodata memory will be made read-only, 826 and non-text memory will be made non-executable. This provides 827 protection against certain security exploits (e.g. executing the heap 828 or modifying text) 829 830 These features are considered standard security practice these days. 831 You should say Y here in almost all cases. 832 833config ARCH_HAS_STRICT_MODULE_RWX 834 def_bool n 835 836config STRICT_MODULE_RWX 837 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 838 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 839 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 840 help 841 If this is set, module text and rodata memory will be made read-only, 842 and non-text memory will be made non-executable. This provides 843 protection against certain security exploits (e.g. writing to text) 844 845# select if the architecture provides an asm/dma-direct.h header 846config ARCH_HAS_PHYS_TO_DMA 847 bool 848 849config ARCH_HAS_REFCOUNT 850 bool 851 help 852 An architecture selects this when it has implemented refcount_t 853 using open coded assembly primitives that provide an optimized 854 refcount_t implementation, possibly at the expense of some full 855 refcount state checks of CONFIG_REFCOUNT_FULL=y. 856 857 The refcount overflow check behavior, however, must be retained. 858 Catching overflows is the primary security concern for protecting 859 against bugs in reference counts. 860 861config REFCOUNT_FULL 862 bool "Perform full reference count validation at the expense of speed" 863 help 864 Enabling this switches the refcounting infrastructure from a fast 865 unchecked atomic_t implementation to a fully state checked 866 implementation, which can be (slightly) slower but provides protections 867 against various use-after-free conditions that can be used in 868 security flaw exploits. 869 870config HAVE_ARCH_COMPILER_H 871 bool 872 help 873 An architecture can select this if it provides an 874 asm/compiler.h header that should be included after 875 linux/compiler-*.h in order to override macro definitions that those 876 headers generally provide. 877 878config HAVE_ARCH_PREL32_RELOCATIONS 879 bool 880 help 881 May be selected by an architecture if it supports place-relative 882 32-bit relocations, both in the toolchain and in the module loader, 883 in which case relative references can be used in special sections 884 for PCI fixup, initcalls etc which are only half the size on 64 bit 885 architectures, and don't require runtime relocation on relocatable 886 kernels. 887 888source "kernel/gcov/Kconfig" 889 890source "scripts/gcc-plugins/Kconfig" 891 892endmenu 893