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_CLK 295 bool 296 help 297 The <linux/clk.h> calls support software clock gating and 298 thus are a key power management tool on many systems. 299 300config HAVE_HW_BREAKPOINT 301 bool 302 depends on PERF_EVENTS 303 304config HAVE_MIXED_BREAKPOINTS_REGS 305 bool 306 depends on HAVE_HW_BREAKPOINT 307 help 308 Depending on the arch implementation of hardware breakpoints, 309 some of them have separate registers for data and instruction 310 breakpoints addresses, others have mixed registers to store 311 them but define the access type in a control register. 312 Select this option if your arch implements breakpoints under the 313 latter fashion. 314 315config HAVE_USER_RETURN_NOTIFIER 316 bool 317 318config HAVE_PERF_EVENTS_NMI 319 bool 320 help 321 System hardware can generate an NMI using the perf event 322 subsystem. Also has support for calculating CPU cycle events 323 to determine how many clock cycles in a given period. 324 325config HAVE_HARDLOCKUP_DETECTOR_PERF 326 bool 327 depends on HAVE_PERF_EVENTS_NMI 328 help 329 The arch chooses to use the generic perf-NMI-based hardlockup 330 detector. Must define HAVE_PERF_EVENTS_NMI. 331 332config HAVE_NMI_WATCHDOG 333 depends on HAVE_NMI 334 bool 335 help 336 The arch provides a low level NMI watchdog. It provides 337 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 338 339config HAVE_HARDLOCKUP_DETECTOR_ARCH 340 bool 341 select HAVE_NMI_WATCHDOG 342 help 343 The arch chooses to provide its own hardlockup detector, which is 344 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 345 interfaces and parameters provided by hardlockup detector subsystem. 346 347config HAVE_PERF_REGS 348 bool 349 help 350 Support selective register dumps for perf events. This includes 351 bit-mapping of each registers and a unique architecture id. 352 353config HAVE_PERF_USER_STACK_DUMP 354 bool 355 help 356 Support user stack dumps for perf event samples. This needs 357 access to the user stack pointer which is not unified across 358 architectures. 359 360config HAVE_ARCH_JUMP_LABEL 361 bool 362 363config HAVE_RCU_TABLE_FREE 364 bool 365 366config HAVE_RCU_TABLE_INVALIDATE 367 bool 368 369config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 370 bool 371 help 372 Temporary select until all architectures can be converted to have 373 irqs disabled over activate_mm. Architectures that do IPI based TLB 374 shootdowns should enable this. 375 376config ARCH_HAVE_NMI_SAFE_CMPXCHG 377 bool 378 379config HAVE_ALIGNED_STRUCT_PAGE 380 bool 381 help 382 This makes sure that struct pages are double word aligned and that 383 e.g. the SLUB allocator can perform double word atomic operations 384 on a struct page for better performance. However selecting this 385 might increase the size of a struct page by a word. 386 387config HAVE_CMPXCHG_LOCAL 388 bool 389 390config HAVE_CMPXCHG_DOUBLE 391 bool 392 393config ARCH_WEAK_RELEASE_ACQUIRE 394 bool 395 396config ARCH_WANT_IPC_PARSE_VERSION 397 bool 398 399config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 400 bool 401 402config ARCH_WANT_OLD_COMPAT_IPC 403 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 404 bool 405 406config HAVE_ARCH_SECCOMP_FILTER 407 bool 408 help 409 An arch should select this symbol if it provides all of these things: 410 - syscall_get_arch() 411 - syscall_get_arguments() 412 - syscall_rollback() 413 - syscall_set_return_value() 414 - SIGSYS siginfo_t support 415 - secure_computing is called from a ptrace_event()-safe context 416 - secure_computing return value is checked and a return value of -1 417 results in the system call being skipped immediately. 418 - seccomp syscall wired up 419 420config SECCOMP_FILTER 421 def_bool y 422 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 423 help 424 Enable tasks to build secure computing environments defined 425 in terms of Berkeley Packet Filter programs which implement 426 task-defined system call filtering polices. 427 428 See Documentation/userspace-api/seccomp_filter.rst for details. 429 430config HAVE_STACKPROTECTOR 431 bool 432 help 433 An arch should select this symbol if: 434 - it has implemented a stack canary (e.g. __stack_chk_guard) 435 436config CC_HAS_STACKPROTECTOR_NONE 437 def_bool $(cc-option,-fno-stack-protector) 438 439config STACKPROTECTOR 440 bool "Stack Protector buffer overflow detection" 441 depends on HAVE_STACKPROTECTOR 442 depends on $(cc-option,-fstack-protector) 443 default y 444 help 445 This option turns on the "stack-protector" GCC feature. This 446 feature puts, at the beginning of functions, a canary value on 447 the stack just before the return address, and validates 448 the value just before actually returning. Stack based buffer 449 overflows (that need to overwrite this return address) now also 450 overwrite the canary, which gets detected and the attack is then 451 neutralized via a kernel panic. 452 453 Functions will have the stack-protector canary logic added if they 454 have an 8-byte or larger character array on the stack. 455 456 This feature requires gcc version 4.2 or above, or a distribution 457 gcc with the feature backported ("-fstack-protector"). 458 459 On an x86 "defconfig" build, this feature adds canary checks to 460 about 3% of all kernel functions, which increases kernel code size 461 by about 0.3%. 462 463config STACKPROTECTOR_STRONG 464 bool "Strong Stack Protector" 465 depends on STACKPROTECTOR 466 depends on $(cc-option,-fstack-protector-strong) 467 default y 468 help 469 Functions will have the stack-protector canary logic added in any 470 of the following conditions: 471 472 - local variable's address used as part of the right hand side of an 473 assignment or function argument 474 - local variable is an array (or union containing an array), 475 regardless of array type or length 476 - uses register local variables 477 478 This feature requires gcc version 4.9 or above, or a distribution 479 gcc with the feature backported ("-fstack-protector-strong"). 480 481 On an x86 "defconfig" build, this feature adds canary checks to 482 about 20% of all kernel functions, which increases the kernel code 483 size by about 2%. 484 485config HAVE_ARCH_WITHIN_STACK_FRAMES 486 bool 487 help 488 An architecture should select this if it can walk the kernel stack 489 frames to determine if an object is part of either the arguments 490 or local variables (i.e. that it excludes saved return addresses, 491 and similar) by implementing an inline arch_within_stack_frames(), 492 which is used by CONFIG_HARDENED_USERCOPY. 493 494config HAVE_CONTEXT_TRACKING 495 bool 496 help 497 Provide kernel/user boundaries probes necessary for subsystems 498 that need it, such as userspace RCU extended quiescent state. 499 Syscalls need to be wrapped inside user_exit()-user_enter() through 500 the slow path using TIF_NOHZ flag. Exceptions handlers must be 501 wrapped as well. Irqs are already protected inside 502 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 503 irq exit still need to be protected. 504 505config HAVE_VIRT_CPU_ACCOUNTING 506 bool 507 508config ARCH_HAS_SCALED_CPUTIME 509 bool 510 511config HAVE_VIRT_CPU_ACCOUNTING_GEN 512 bool 513 default y if 64BIT 514 help 515 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 516 Before enabling this option, arch code must be audited 517 to ensure there are no races in concurrent read/write of 518 cputime_t. For example, reading/writing 64-bit cputime_t on 519 some 32-bit arches may require multiple accesses, so proper 520 locking is needed to protect against concurrent accesses. 521 522 523config HAVE_IRQ_TIME_ACCOUNTING 524 bool 525 help 526 Archs need to ensure they use a high enough resolution clock to 527 support irq time accounting and then call enable_sched_clock_irqtime(). 528 529config HAVE_ARCH_TRANSPARENT_HUGEPAGE 530 bool 531 532config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 533 bool 534 535config HAVE_ARCH_HUGE_VMAP 536 bool 537 538config HAVE_ARCH_SOFT_DIRTY 539 bool 540 541config HAVE_MOD_ARCH_SPECIFIC 542 bool 543 help 544 The arch uses struct mod_arch_specific to store data. Many arches 545 just need a simple module loader without arch specific data - those 546 should not enable this. 547 548config MODULES_USE_ELF_RELA 549 bool 550 help 551 Modules only use ELF RELA relocations. Modules with ELF REL 552 relocations will give an error. 553 554config MODULES_USE_ELF_REL 555 bool 556 help 557 Modules only use ELF REL relocations. Modules with ELF RELA 558 relocations will give an error. 559 560config HAVE_IRQ_EXIT_ON_IRQ_STACK 561 bool 562 help 563 Architecture doesn't only execute the irq handler on the irq stack 564 but also irq_exit(). This way we can process softirqs on this irq 565 stack instead of switching to a new one when we call __do_softirq() 566 in the end of an hardirq. 567 This spares a stack switch and improves cache usage on softirq 568 processing. 569 570config PGTABLE_LEVELS 571 int 572 default 2 573 574config ARCH_HAS_ELF_RANDOMIZE 575 bool 576 help 577 An architecture supports choosing randomized locations for 578 stack, mmap, brk, and ET_DYN. Defined functions: 579 - arch_mmap_rnd() 580 - arch_randomize_brk() 581 582config HAVE_ARCH_MMAP_RND_BITS 583 bool 584 help 585 An arch should select this symbol if it supports setting a variable 586 number of bits for use in establishing the base address for mmap 587 allocations, has MMU enabled and provides values for both: 588 - ARCH_MMAP_RND_BITS_MIN 589 - ARCH_MMAP_RND_BITS_MAX 590 591config HAVE_EXIT_THREAD 592 bool 593 help 594 An architecture implements exit_thread. 595 596config ARCH_MMAP_RND_BITS_MIN 597 int 598 599config ARCH_MMAP_RND_BITS_MAX 600 int 601 602config ARCH_MMAP_RND_BITS_DEFAULT 603 int 604 605config ARCH_MMAP_RND_BITS 606 int "Number of bits to use for ASLR of mmap base address" if EXPERT 607 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 608 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 609 default ARCH_MMAP_RND_BITS_MIN 610 depends on HAVE_ARCH_MMAP_RND_BITS 611 help 612 This value can be used to select the number of bits to use to 613 determine the random offset to the base address of vma regions 614 resulting from mmap allocations. This value will be bounded 615 by the architecture's minimum and maximum supported values. 616 617 This value can be changed after boot using the 618 /proc/sys/vm/mmap_rnd_bits tunable 619 620config HAVE_ARCH_MMAP_RND_COMPAT_BITS 621 bool 622 help 623 An arch should select this symbol if it supports running applications 624 in compatibility mode, supports setting a variable number of bits for 625 use in establishing the base address for mmap allocations, has MMU 626 enabled and provides values for both: 627 - ARCH_MMAP_RND_COMPAT_BITS_MIN 628 - ARCH_MMAP_RND_COMPAT_BITS_MAX 629 630config ARCH_MMAP_RND_COMPAT_BITS_MIN 631 int 632 633config ARCH_MMAP_RND_COMPAT_BITS_MAX 634 int 635 636config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 637 int 638 639config ARCH_MMAP_RND_COMPAT_BITS 640 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 641 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 642 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 643 default ARCH_MMAP_RND_COMPAT_BITS_MIN 644 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 645 help 646 This value can be used to select the number of bits to use to 647 determine the random offset to the base address of vma regions 648 resulting from mmap allocations for compatible applications This 649 value will be bounded by the architecture's minimum and maximum 650 supported values. 651 652 This value can be changed after boot using the 653 /proc/sys/vm/mmap_rnd_compat_bits tunable 654 655config HAVE_ARCH_COMPAT_MMAP_BASES 656 bool 657 help 658 This allows 64bit applications to invoke 32-bit mmap() syscall 659 and vice-versa 32-bit applications to call 64-bit mmap(). 660 Required for applications doing different bitness syscalls. 661 662config HAVE_COPY_THREAD_TLS 663 bool 664 help 665 Architecture provides copy_thread_tls to accept tls argument via 666 normal C parameter passing, rather than extracting the syscall 667 argument from pt_regs. 668 669config HAVE_STACK_VALIDATION 670 bool 671 help 672 Architecture supports the 'objtool check' host tool command, which 673 performs compile-time stack metadata validation. 674 675config HAVE_RELIABLE_STACKTRACE 676 bool 677 help 678 Architecture has a save_stack_trace_tsk_reliable() function which 679 only returns a stack trace if it can guarantee the trace is reliable. 680 681config HAVE_ARCH_HASH 682 bool 683 default n 684 help 685 If this is set, the architecture provides an <asm/hash.h> 686 file which provides platform-specific implementations of some 687 functions in <linux/hash.h> or fs/namei.c. 688 689config ISA_BUS_API 690 def_bool ISA 691 692# 693# ABI hall of shame 694# 695config CLONE_BACKWARDS 696 bool 697 help 698 Architecture has tls passed as the 4th argument of clone(2), 699 not the 5th one. 700 701config CLONE_BACKWARDS2 702 bool 703 help 704 Architecture has the first two arguments of clone(2) swapped. 705 706config CLONE_BACKWARDS3 707 bool 708 help 709 Architecture has tls passed as the 3rd argument of clone(2), 710 not the 5th one. 711 712config ODD_RT_SIGACTION 713 bool 714 help 715 Architecture has unusual rt_sigaction(2) arguments 716 717config OLD_SIGSUSPEND 718 bool 719 help 720 Architecture has old sigsuspend(2) syscall, of one-argument variety 721 722config OLD_SIGSUSPEND3 723 bool 724 help 725 Even weirder antique ABI - three-argument sigsuspend(2) 726 727config OLD_SIGACTION 728 bool 729 help 730 Architecture has old sigaction(2) syscall. Nope, not the same 731 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 732 but fairly different variant of sigaction(2), thanks to OSF/1 733 compatibility... 734 735config COMPAT_OLD_SIGACTION 736 bool 737 738config 64BIT_TIME 739 def_bool ARCH_HAS_64BIT_TIME 740 help 741 This should be selected by all architectures that need to support 742 new system calls with a 64-bit time_t. This is relevant on all 32-bit 743 architectures, and 64-bit architectures as part of compat syscall 744 handling. 745 746config COMPAT_32BIT_TIME 747 def_bool (!64BIT && 64BIT_TIME) || COMPAT 748 help 749 This enables 32 bit time_t support in addition to 64 bit time_t support. 750 This is relevant on all 32-bit architectures, and 64-bit architectures 751 as part of compat syscall handling. 752 753config ARCH_NO_COHERENT_DMA_MMAP 754 bool 755 756config ARCH_NO_PREEMPT 757 bool 758 759config CPU_NO_EFFICIENT_FFS 760 def_bool n 761 762config HAVE_ARCH_VMAP_STACK 763 def_bool n 764 help 765 An arch should select this symbol if it can support kernel stacks 766 in vmalloc space. This means: 767 768 - vmalloc space must be large enough to hold many kernel stacks. 769 This may rule out many 32-bit architectures. 770 771 - Stacks in vmalloc space need to work reliably. For example, if 772 vmap page tables are created on demand, either this mechanism 773 needs to work while the stack points to a virtual address with 774 unpopulated page tables or arch code (switch_to() and switch_mm(), 775 most likely) needs to ensure that the stack's page table entries 776 are populated before running on a possibly unpopulated stack. 777 778 - If the stack overflows into a guard page, something reasonable 779 should happen. The definition of "reasonable" is flexible, but 780 instantly rebooting without logging anything would be unfriendly. 781 782config VMAP_STACK 783 default y 784 bool "Use a virtually-mapped stack" 785 depends on HAVE_ARCH_VMAP_STACK && !KASAN 786 ---help--- 787 Enable this if you want the use virtually-mapped kernel stacks 788 with guard pages. This causes kernel stack overflows to be 789 caught immediately rather than causing difficult-to-diagnose 790 corruption. 791 792 This is presently incompatible with KASAN because KASAN expects 793 the stack to map directly to the KASAN shadow map using a formula 794 that is incorrect if the stack is in vmalloc space. 795 796config ARCH_OPTIONAL_KERNEL_RWX 797 def_bool n 798 799config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 800 def_bool n 801 802config ARCH_HAS_STRICT_KERNEL_RWX 803 def_bool n 804 805config STRICT_KERNEL_RWX 806 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 807 depends on ARCH_HAS_STRICT_KERNEL_RWX 808 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 809 help 810 If this is set, kernel text and rodata memory will be made read-only, 811 and non-text memory will be made non-executable. This provides 812 protection against certain security exploits (e.g. executing the heap 813 or modifying text) 814 815 These features are considered standard security practice these days. 816 You should say Y here in almost all cases. 817 818config ARCH_HAS_STRICT_MODULE_RWX 819 def_bool n 820 821config STRICT_MODULE_RWX 822 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 823 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 824 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 825 help 826 If this is set, module text and rodata memory will be made read-only, 827 and non-text memory will be made non-executable. This provides 828 protection against certain security exploits (e.g. writing to text) 829 830# select if the architecture provides an asm/dma-direct.h header 831config ARCH_HAS_PHYS_TO_DMA 832 bool 833 834config ARCH_HAS_REFCOUNT 835 bool 836 help 837 An architecture selects this when it has implemented refcount_t 838 using open coded assembly primitives that provide an optimized 839 refcount_t implementation, possibly at the expense of some full 840 refcount state checks of CONFIG_REFCOUNT_FULL=y. 841 842 The refcount overflow check behavior, however, must be retained. 843 Catching overflows is the primary security concern for protecting 844 against bugs in reference counts. 845 846config REFCOUNT_FULL 847 bool "Perform full reference count validation at the expense of speed" 848 help 849 Enabling this switches the refcounting infrastructure from a fast 850 unchecked atomic_t implementation to a fully state checked 851 implementation, which can be (slightly) slower but provides protections 852 against various use-after-free conditions that can be used in 853 security flaw exploits. 854 855config HAVE_ARCH_COMPILER_H 856 bool 857 help 858 An architecture can select this if it provides an 859 asm/compiler.h header that should be included after 860 linux/compiler-*.h in order to override macro definitions that those 861 headers generally provide. 862 863config HAVE_ARCH_PREL32_RELOCATIONS 864 bool 865 help 866 May be selected by an architecture if it supports place-relative 867 32-bit relocations, both in the toolchain and in the module loader, 868 in which case relative references can be used in special sections 869 for PCI fixup, initcalls etc which are only half the size on 64 bit 870 architectures, and don't require runtime relocation on relocatable 871 kernels. 872 873source "kernel/gcov/Kconfig" 874 875source "scripts/gcc-plugins/Kconfig" 876 877endmenu 878