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