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_STACKPROTECTOR 433 bool 434 help 435 An arch should select this symbol if: 436 - it has implemented a stack canary (e.g. __stack_chk_guard) 437 438config CC_HAS_STACKPROTECTOR_NONE 439 def_bool $(cc-option,-fno-stack-protector) 440 441config STACKPROTECTOR 442 bool "Stack Protector buffer overflow detection" 443 depends on HAVE_STACKPROTECTOR 444 depends on $(cc-option,-fstack-protector) 445 default y 446 help 447 This option turns on the "stack-protector" GCC feature. This 448 feature puts, at the beginning of functions, a canary value on 449 the stack just before the return address, and validates 450 the value just before actually returning. Stack based buffer 451 overflows (that need to overwrite this return address) now also 452 overwrite the canary, which gets detected and the attack is then 453 neutralized via a kernel panic. 454 455 Functions will have the stack-protector canary logic added if they 456 have an 8-byte or larger character array on the stack. 457 458 This feature requires gcc version 4.2 or above, or a distribution 459 gcc with the feature backported ("-fstack-protector"). 460 461 On an x86 "defconfig" build, this feature adds canary checks to 462 about 3% of all kernel functions, which increases kernel code size 463 by about 0.3%. 464 465config STACKPROTECTOR_STRONG 466 bool "Strong Stack Protector" 467 depends on STACKPROTECTOR 468 depends on $(cc-option,-fstack-protector-strong) 469 default y 470 help 471 Functions will have the stack-protector canary logic added in any 472 of the following conditions: 473 474 - local variable's address used as part of the right hand side of an 475 assignment or function argument 476 - local variable is an array (or union containing an array), 477 regardless of array type or length 478 - uses register local variables 479 480 This feature requires gcc version 4.9 or above, or a distribution 481 gcc with the feature backported ("-fstack-protector-strong"). 482 483 On an x86 "defconfig" build, this feature adds canary checks to 484 about 20% of all kernel functions, which increases the kernel code 485 size by about 2%. 486 487config HAVE_ARCH_WITHIN_STACK_FRAMES 488 bool 489 help 490 An architecture should select this if it can walk the kernel stack 491 frames to determine if an object is part of either the arguments 492 or local variables (i.e. that it excludes saved return addresses, 493 and similar) by implementing an inline arch_within_stack_frames(), 494 which is used by CONFIG_HARDENED_USERCOPY. 495 496config HAVE_CONTEXT_TRACKING 497 bool 498 help 499 Provide kernel/user boundaries probes necessary for subsystems 500 that need it, such as userspace RCU extended quiescent state. 501 Syscalls need to be wrapped inside user_exit()-user_enter() through 502 the slow path using TIF_NOHZ flag. Exceptions handlers must be 503 wrapped as well. Irqs are already protected inside 504 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 505 irq exit still need to be protected. 506 507config HAVE_VIRT_CPU_ACCOUNTING 508 bool 509 510config ARCH_HAS_SCALED_CPUTIME 511 bool 512 513config HAVE_VIRT_CPU_ACCOUNTING_GEN 514 bool 515 default y if 64BIT 516 help 517 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 518 Before enabling this option, arch code must be audited 519 to ensure there are no races in concurrent read/write of 520 cputime_t. For example, reading/writing 64-bit cputime_t on 521 some 32-bit arches may require multiple accesses, so proper 522 locking is needed to protect against concurrent accesses. 523 524 525config HAVE_IRQ_TIME_ACCOUNTING 526 bool 527 help 528 Archs need to ensure they use a high enough resolution clock to 529 support irq time accounting and then call enable_sched_clock_irqtime(). 530 531config HAVE_ARCH_TRANSPARENT_HUGEPAGE 532 bool 533 534config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 535 bool 536 537config HAVE_ARCH_HUGE_VMAP 538 bool 539 540config HAVE_ARCH_SOFT_DIRTY 541 bool 542 543config HAVE_MOD_ARCH_SPECIFIC 544 bool 545 help 546 The arch uses struct mod_arch_specific to store data. Many arches 547 just need a simple module loader without arch specific data - those 548 should not enable this. 549 550config MODULES_USE_ELF_RELA 551 bool 552 help 553 Modules only use ELF RELA relocations. Modules with ELF REL 554 relocations will give an error. 555 556config MODULES_USE_ELF_REL 557 bool 558 help 559 Modules only use ELF REL relocations. Modules with ELF RELA 560 relocations will give an error. 561 562config HAVE_IRQ_EXIT_ON_IRQ_STACK 563 bool 564 help 565 Architecture doesn't only execute the irq handler on the irq stack 566 but also irq_exit(). This way we can process softirqs on this irq 567 stack instead of switching to a new one when we call __do_softirq() 568 in the end of an hardirq. 569 This spares a stack switch and improves cache usage on softirq 570 processing. 571 572config PGTABLE_LEVELS 573 int 574 default 2 575 576config ARCH_HAS_ELF_RANDOMIZE 577 bool 578 help 579 An architecture supports choosing randomized locations for 580 stack, mmap, brk, and ET_DYN. Defined functions: 581 - arch_mmap_rnd() 582 - arch_randomize_brk() 583 584config HAVE_ARCH_MMAP_RND_BITS 585 bool 586 help 587 An arch should select this symbol if it supports setting a variable 588 number of bits for use in establishing the base address for mmap 589 allocations, has MMU enabled and provides values for both: 590 - ARCH_MMAP_RND_BITS_MIN 591 - ARCH_MMAP_RND_BITS_MAX 592 593config HAVE_EXIT_THREAD 594 bool 595 help 596 An architecture implements exit_thread. 597 598config ARCH_MMAP_RND_BITS_MIN 599 int 600 601config ARCH_MMAP_RND_BITS_MAX 602 int 603 604config ARCH_MMAP_RND_BITS_DEFAULT 605 int 606 607config ARCH_MMAP_RND_BITS 608 int "Number of bits to use for ASLR of mmap base address" if EXPERT 609 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 610 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 611 default ARCH_MMAP_RND_BITS_MIN 612 depends on HAVE_ARCH_MMAP_RND_BITS 613 help 614 This value can be used to select the number of bits to use to 615 determine the random offset to the base address of vma regions 616 resulting from mmap allocations. This value will be bounded 617 by the architecture's minimum and maximum supported values. 618 619 This value can be changed after boot using the 620 /proc/sys/vm/mmap_rnd_bits tunable 621 622config HAVE_ARCH_MMAP_RND_COMPAT_BITS 623 bool 624 help 625 An arch should select this symbol if it supports running applications 626 in compatibility mode, supports setting a variable number of bits for 627 use in establishing the base address for mmap allocations, has MMU 628 enabled and provides values for both: 629 - ARCH_MMAP_RND_COMPAT_BITS_MIN 630 - ARCH_MMAP_RND_COMPAT_BITS_MAX 631 632config ARCH_MMAP_RND_COMPAT_BITS_MIN 633 int 634 635config ARCH_MMAP_RND_COMPAT_BITS_MAX 636 int 637 638config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 639 int 640 641config ARCH_MMAP_RND_COMPAT_BITS 642 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 643 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 644 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 645 default ARCH_MMAP_RND_COMPAT_BITS_MIN 646 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 647 help 648 This value can be used to select the number of bits to use to 649 determine the random offset to the base address of vma regions 650 resulting from mmap allocations for compatible applications This 651 value will be bounded by the architecture's minimum and maximum 652 supported values. 653 654 This value can be changed after boot using the 655 /proc/sys/vm/mmap_rnd_compat_bits tunable 656 657config HAVE_ARCH_COMPAT_MMAP_BASES 658 bool 659 help 660 This allows 64bit applications to invoke 32-bit mmap() syscall 661 and vice-versa 32-bit applications to call 64-bit mmap(). 662 Required for applications doing different bitness syscalls. 663 664config HAVE_COPY_THREAD_TLS 665 bool 666 help 667 Architecture provides copy_thread_tls to accept tls argument via 668 normal C parameter passing, rather than extracting the syscall 669 argument from pt_regs. 670 671config HAVE_STACK_VALIDATION 672 bool 673 help 674 Architecture supports the 'objtool check' host tool command, which 675 performs compile-time stack metadata validation. 676 677config HAVE_RELIABLE_STACKTRACE 678 bool 679 help 680 Architecture has a save_stack_trace_tsk_reliable() function which 681 only returns a stack trace if it can guarantee the trace is reliable. 682 683config HAVE_ARCH_HASH 684 bool 685 default n 686 help 687 If this is set, the architecture provides an <asm/hash.h> 688 file which provides platform-specific implementations of some 689 functions in <linux/hash.h> or fs/namei.c. 690 691config ISA_BUS_API 692 def_bool ISA 693 694# 695# ABI hall of shame 696# 697config CLONE_BACKWARDS 698 bool 699 help 700 Architecture has tls passed as the 4th argument of clone(2), 701 not the 5th one. 702 703config CLONE_BACKWARDS2 704 bool 705 help 706 Architecture has the first two arguments of clone(2) swapped. 707 708config CLONE_BACKWARDS3 709 bool 710 help 711 Architecture has tls passed as the 3rd argument of clone(2), 712 not the 5th one. 713 714config ODD_RT_SIGACTION 715 bool 716 help 717 Architecture has unusual rt_sigaction(2) arguments 718 719config OLD_SIGSUSPEND 720 bool 721 help 722 Architecture has old sigsuspend(2) syscall, of one-argument variety 723 724config OLD_SIGSUSPEND3 725 bool 726 help 727 Even weirder antique ABI - three-argument sigsuspend(2) 728 729config OLD_SIGACTION 730 bool 731 help 732 Architecture has old sigaction(2) syscall. Nope, not the same 733 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 734 but fairly different variant of sigaction(2), thanks to OSF/1 735 compatibility... 736 737config COMPAT_OLD_SIGACTION 738 bool 739 740config 64BIT_TIME 741 def_bool ARCH_HAS_64BIT_TIME 742 help 743 This should be selected by all architectures that need to support 744 new system calls with a 64-bit time_t. This is relevant on all 32-bit 745 architectures, and 64-bit architectures as part of compat syscall 746 handling. 747 748config COMPAT_32BIT_TIME 749 def_bool (!64BIT && 64BIT_TIME) || COMPAT 750 help 751 This enables 32 bit time_t support in addition to 64 bit time_t support. 752 This is relevant on all 32-bit architectures, and 64-bit architectures 753 as part of compat syscall handling. 754 755config ARCH_NO_COHERENT_DMA_MMAP 756 bool 757 758config ARCH_NO_PREEMPT 759 bool 760 761config CPU_NO_EFFICIENT_FFS 762 def_bool n 763 764config HAVE_ARCH_VMAP_STACK 765 def_bool n 766 help 767 An arch should select this symbol if it can support kernel stacks 768 in vmalloc space. This means: 769 770 - vmalloc space must be large enough to hold many kernel stacks. 771 This may rule out many 32-bit architectures. 772 773 - Stacks in vmalloc space need to work reliably. For example, if 774 vmap page tables are created on demand, either this mechanism 775 needs to work while the stack points to a virtual address with 776 unpopulated page tables or arch code (switch_to() and switch_mm(), 777 most likely) needs to ensure that the stack's page table entries 778 are populated before running on a possibly unpopulated stack. 779 780 - If the stack overflows into a guard page, something reasonable 781 should happen. The definition of "reasonable" is flexible, but 782 instantly rebooting without logging anything would be unfriendly. 783 784config VMAP_STACK 785 default y 786 bool "Use a virtually-mapped stack" 787 depends on HAVE_ARCH_VMAP_STACK && !KASAN 788 ---help--- 789 Enable this if you want the use virtually-mapped kernel stacks 790 with guard pages. This causes kernel stack overflows to be 791 caught immediately rather than causing difficult-to-diagnose 792 corruption. 793 794 This is presently incompatible with KASAN because KASAN expects 795 the stack to map directly to the KASAN shadow map using a formula 796 that is incorrect if the stack is in vmalloc space. 797 798config ARCH_OPTIONAL_KERNEL_RWX 799 def_bool n 800 801config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 802 def_bool n 803 804config ARCH_HAS_STRICT_KERNEL_RWX 805 def_bool n 806 807config STRICT_KERNEL_RWX 808 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 809 depends on ARCH_HAS_STRICT_KERNEL_RWX 810 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 811 help 812 If this is set, kernel text and rodata memory will be made read-only, 813 and non-text memory will be made non-executable. This provides 814 protection against certain security exploits (e.g. executing the heap 815 or modifying text) 816 817 These features are considered standard security practice these days. 818 You should say Y here in almost all cases. 819 820config ARCH_HAS_STRICT_MODULE_RWX 821 def_bool n 822 823config STRICT_MODULE_RWX 824 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 825 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 826 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 827 help 828 If this is set, module text and rodata memory will be made read-only, 829 and non-text memory will be made non-executable. This provides 830 protection against certain security exploits (e.g. writing to text) 831 832# select if the architecture provides an asm/dma-direct.h header 833config ARCH_HAS_PHYS_TO_DMA 834 bool 835 836config ARCH_HAS_REFCOUNT 837 bool 838 help 839 An architecture selects this when it has implemented refcount_t 840 using open coded assembly primitives that provide an optimized 841 refcount_t implementation, possibly at the expense of some full 842 refcount state checks of CONFIG_REFCOUNT_FULL=y. 843 844 The refcount overflow check behavior, however, must be retained. 845 Catching overflows is the primary security concern for protecting 846 against bugs in reference counts. 847 848config REFCOUNT_FULL 849 bool "Perform full reference count validation at the expense of speed" 850 help 851 Enabling this switches the refcounting infrastructure from a fast 852 unchecked atomic_t implementation to a fully state checked 853 implementation, which can be (slightly) slower but provides protections 854 against various use-after-free conditions that can be used in 855 security flaw exploits. 856 857config HAVE_ARCH_COMPILER_H 858 bool 859 help 860 An architecture can select this if it provides an 861 asm/compiler.h header that should be included after 862 linux/compiler-*.h in order to override macro definitions that those 863 headers generally provide. 864 865config HAVE_ARCH_PREL32_RELOCATIONS 866 bool 867 help 868 May be selected by an architecture if it supports place-relative 869 32-bit relocations, both in the toolchain and in the module loader, 870 in which case relative references can be used in special sections 871 for PCI fixup, initcalls etc which are only half the size on 64 bit 872 architectures, and don't require runtime relocation on relocatable 873 kernels. 874 875source "kernel/gcov/Kconfig" 876 877source "scripts/gcc-plugins/Kconfig" 878 879endmenu 880