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 ARCH_32BIT_OFF_T 280 bool 281 depends on !64BIT 282 help 283 All new 32-bit architectures should have 64-bit off_t type on 284 userspace side which corresponds to the loff_t kernel type. This 285 is the requirement for modern ABIs. Some existing architectures 286 still support 32-bit off_t. This option is enabled for all such 287 architectures explicitly. 288 289config HAVE_REGS_AND_STACK_ACCESS_API 290 bool 291 help 292 This symbol should be selected by an architecure if it supports 293 the API needed to access registers and stack entries from pt_regs, 294 declared in asm/ptrace.h 295 For example the kprobes-based event tracer needs this API. 296 297config HAVE_RSEQ 298 bool 299 depends on HAVE_REGS_AND_STACK_ACCESS_API 300 help 301 This symbol should be selected by an architecture if it 302 supports an implementation of restartable sequences. 303 304config HAVE_FUNCTION_ARG_ACCESS_API 305 bool 306 help 307 This symbol should be selected by an architecure if it supports 308 the API needed to access function arguments from pt_regs, 309 declared in asm/ptrace.h 310 311config HAVE_CLK 312 bool 313 help 314 The <linux/clk.h> calls support software clock gating and 315 thus are a key power management tool on many systems. 316 317config HAVE_HW_BREAKPOINT 318 bool 319 depends on PERF_EVENTS 320 321config HAVE_MIXED_BREAKPOINTS_REGS 322 bool 323 depends on HAVE_HW_BREAKPOINT 324 help 325 Depending on the arch implementation of hardware breakpoints, 326 some of them have separate registers for data and instruction 327 breakpoints addresses, others have mixed registers to store 328 them but define the access type in a control register. 329 Select this option if your arch implements breakpoints under the 330 latter fashion. 331 332config HAVE_USER_RETURN_NOTIFIER 333 bool 334 335config HAVE_PERF_EVENTS_NMI 336 bool 337 help 338 System hardware can generate an NMI using the perf event 339 subsystem. Also has support for calculating CPU cycle events 340 to determine how many clock cycles in a given period. 341 342config HAVE_HARDLOCKUP_DETECTOR_PERF 343 bool 344 depends on HAVE_PERF_EVENTS_NMI 345 help 346 The arch chooses to use the generic perf-NMI-based hardlockup 347 detector. Must define HAVE_PERF_EVENTS_NMI. 348 349config HAVE_NMI_WATCHDOG 350 depends on HAVE_NMI 351 bool 352 help 353 The arch provides a low level NMI watchdog. It provides 354 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 355 356config HAVE_HARDLOCKUP_DETECTOR_ARCH 357 bool 358 select HAVE_NMI_WATCHDOG 359 help 360 The arch chooses to provide its own hardlockup detector, which is 361 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 362 interfaces and parameters provided by hardlockup detector subsystem. 363 364config HAVE_PERF_REGS 365 bool 366 help 367 Support selective register dumps for perf events. This includes 368 bit-mapping of each registers and a unique architecture id. 369 370config HAVE_PERF_USER_STACK_DUMP 371 bool 372 help 373 Support user stack dumps for perf event samples. This needs 374 access to the user stack pointer which is not unified across 375 architectures. 376 377config HAVE_ARCH_JUMP_LABEL 378 bool 379 380config HAVE_ARCH_JUMP_LABEL_RELATIVE 381 bool 382 383config HAVE_RCU_TABLE_FREE 384 bool 385 386config HAVE_RCU_TABLE_INVALIDATE 387 bool 388 389config ARCH_HAVE_NMI_SAFE_CMPXCHG 390 bool 391 392config HAVE_ALIGNED_STRUCT_PAGE 393 bool 394 help 395 This makes sure that struct pages are double word aligned and that 396 e.g. the SLUB allocator can perform double word atomic operations 397 on a struct page for better performance. However selecting this 398 might increase the size of a struct page by a word. 399 400config HAVE_CMPXCHG_LOCAL 401 bool 402 403config HAVE_CMPXCHG_DOUBLE 404 bool 405 406config ARCH_WEAK_RELEASE_ACQUIRE 407 bool 408 409config ARCH_WANT_IPC_PARSE_VERSION 410 bool 411 412config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 413 bool 414 415config ARCH_WANT_OLD_COMPAT_IPC 416 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 417 bool 418 419config HAVE_ARCH_SECCOMP_FILTER 420 bool 421 help 422 An arch should select this symbol if it provides all of these things: 423 - syscall_get_arch() 424 - syscall_get_arguments() 425 - syscall_rollback() 426 - syscall_set_return_value() 427 - SIGSYS siginfo_t support 428 - secure_computing is called from a ptrace_event()-safe context 429 - secure_computing return value is checked and a return value of -1 430 results in the system call being skipped immediately. 431 - seccomp syscall wired up 432 433config SECCOMP_FILTER 434 def_bool y 435 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 436 help 437 Enable tasks to build secure computing environments defined 438 in terms of Berkeley Packet Filter programs which implement 439 task-defined system call filtering polices. 440 441 See Documentation/userspace-api/seccomp_filter.rst for details. 442 443config HAVE_ARCH_STACKLEAK 444 bool 445 help 446 An architecture should select this if it has the code which 447 fills the used part of the kernel stack with the STACKLEAK_POISON 448 value before returning from system calls. 449 450config HAVE_STACKPROTECTOR 451 bool 452 help 453 An arch should select this symbol if: 454 - it has implemented a stack canary (e.g. __stack_chk_guard) 455 456config CC_HAS_STACKPROTECTOR_NONE 457 def_bool $(cc-option,-fno-stack-protector) 458 459config STACKPROTECTOR 460 bool "Stack Protector buffer overflow detection" 461 depends on HAVE_STACKPROTECTOR 462 depends on $(cc-option,-fstack-protector) 463 default y 464 help 465 This option turns on the "stack-protector" GCC feature. This 466 feature puts, at the beginning of functions, a canary value on 467 the stack just before the return address, and validates 468 the value just before actually returning. Stack based buffer 469 overflows (that need to overwrite this return address) now also 470 overwrite the canary, which gets detected and the attack is then 471 neutralized via a kernel panic. 472 473 Functions will have the stack-protector canary logic added if they 474 have an 8-byte or larger character array on the stack. 475 476 This feature requires gcc version 4.2 or above, or a distribution 477 gcc with the feature backported ("-fstack-protector"). 478 479 On an x86 "defconfig" build, this feature adds canary checks to 480 about 3% of all kernel functions, which increases kernel code size 481 by about 0.3%. 482 483config STACKPROTECTOR_STRONG 484 bool "Strong Stack Protector" 485 depends on STACKPROTECTOR 486 depends on $(cc-option,-fstack-protector-strong) 487 default y 488 help 489 Functions will have the stack-protector canary logic added in any 490 of the following conditions: 491 492 - local variable's address used as part of the right hand side of an 493 assignment or function argument 494 - local variable is an array (or union containing an array), 495 regardless of array type or length 496 - uses register local variables 497 498 This feature requires gcc version 4.9 or above, or a distribution 499 gcc with the feature backported ("-fstack-protector-strong"). 500 501 On an x86 "defconfig" build, this feature adds canary checks to 502 about 20% of all kernel functions, which increases the kernel code 503 size by about 2%. 504 505config HAVE_ARCH_WITHIN_STACK_FRAMES 506 bool 507 help 508 An architecture should select this if it can walk the kernel stack 509 frames to determine if an object is part of either the arguments 510 or local variables (i.e. that it excludes saved return addresses, 511 and similar) by implementing an inline arch_within_stack_frames(), 512 which is used by CONFIG_HARDENED_USERCOPY. 513 514config HAVE_CONTEXT_TRACKING 515 bool 516 help 517 Provide kernel/user boundaries probes necessary for subsystems 518 that need it, such as userspace RCU extended quiescent state. 519 Syscalls need to be wrapped inside user_exit()-user_enter() through 520 the slow path using TIF_NOHZ flag. Exceptions handlers must be 521 wrapped as well. Irqs are already protected inside 522 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 523 irq exit still need to be protected. 524 525config HAVE_VIRT_CPU_ACCOUNTING 526 bool 527 528config ARCH_HAS_SCALED_CPUTIME 529 bool 530 531config HAVE_VIRT_CPU_ACCOUNTING_GEN 532 bool 533 default y if 64BIT 534 help 535 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 536 Before enabling this option, arch code must be audited 537 to ensure there are no races in concurrent read/write of 538 cputime_t. For example, reading/writing 64-bit cputime_t on 539 some 32-bit arches may require multiple accesses, so proper 540 locking is needed to protect against concurrent accesses. 541 542 543config HAVE_IRQ_TIME_ACCOUNTING 544 bool 545 help 546 Archs need to ensure they use a high enough resolution clock to 547 support irq time accounting and then call enable_sched_clock_irqtime(). 548 549config HAVE_MOVE_PMD 550 bool 551 help 552 Archs that select this are able to move page tables at the PMD level. 553 554config HAVE_ARCH_TRANSPARENT_HUGEPAGE 555 bool 556 557config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 558 bool 559 560config HAVE_ARCH_HUGE_VMAP 561 bool 562 563config HAVE_ARCH_SOFT_DIRTY 564 bool 565 566config HAVE_MOD_ARCH_SPECIFIC 567 bool 568 help 569 The arch uses struct mod_arch_specific to store data. Many arches 570 just need a simple module loader without arch specific data - those 571 should not enable this. 572 573config MODULES_USE_ELF_RELA 574 bool 575 help 576 Modules only use ELF RELA relocations. Modules with ELF REL 577 relocations will give an error. 578 579config MODULES_USE_ELF_REL 580 bool 581 help 582 Modules only use ELF REL relocations. Modules with ELF RELA 583 relocations will give an error. 584 585config HAVE_IRQ_EXIT_ON_IRQ_STACK 586 bool 587 help 588 Architecture doesn't only execute the irq handler on the irq stack 589 but also irq_exit(). This way we can process softirqs on this irq 590 stack instead of switching to a new one when we call __do_softirq() 591 in the end of an hardirq. 592 This spares a stack switch and improves cache usage on softirq 593 processing. 594 595config PGTABLE_LEVELS 596 int 597 default 2 598 599config ARCH_HAS_ELF_RANDOMIZE 600 bool 601 help 602 An architecture supports choosing randomized locations for 603 stack, mmap, brk, and ET_DYN. Defined functions: 604 - arch_mmap_rnd() 605 - arch_randomize_brk() 606 607config HAVE_ARCH_MMAP_RND_BITS 608 bool 609 help 610 An arch should select this symbol if it supports setting a variable 611 number of bits for use in establishing the base address for mmap 612 allocations, has MMU enabled and provides values for both: 613 - ARCH_MMAP_RND_BITS_MIN 614 - ARCH_MMAP_RND_BITS_MAX 615 616config HAVE_EXIT_THREAD 617 bool 618 help 619 An architecture implements exit_thread. 620 621config ARCH_MMAP_RND_BITS_MIN 622 int 623 624config ARCH_MMAP_RND_BITS_MAX 625 int 626 627config ARCH_MMAP_RND_BITS_DEFAULT 628 int 629 630config ARCH_MMAP_RND_BITS 631 int "Number of bits to use for ASLR of mmap base address" if EXPERT 632 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 633 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 634 default ARCH_MMAP_RND_BITS_MIN 635 depends on HAVE_ARCH_MMAP_RND_BITS 636 help 637 This value can be used to select the number of bits to use to 638 determine the random offset to the base address of vma regions 639 resulting from mmap allocations. This value will be bounded 640 by the architecture's minimum and maximum supported values. 641 642 This value can be changed after boot using the 643 /proc/sys/vm/mmap_rnd_bits tunable 644 645config HAVE_ARCH_MMAP_RND_COMPAT_BITS 646 bool 647 help 648 An arch should select this symbol if it supports running applications 649 in compatibility mode, supports setting a variable number of bits for 650 use in establishing the base address for mmap allocations, has MMU 651 enabled and provides values for both: 652 - ARCH_MMAP_RND_COMPAT_BITS_MIN 653 - ARCH_MMAP_RND_COMPAT_BITS_MAX 654 655config ARCH_MMAP_RND_COMPAT_BITS_MIN 656 int 657 658config ARCH_MMAP_RND_COMPAT_BITS_MAX 659 int 660 661config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 662 int 663 664config ARCH_MMAP_RND_COMPAT_BITS 665 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 666 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 667 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 668 default ARCH_MMAP_RND_COMPAT_BITS_MIN 669 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 670 help 671 This value can be used to select the number of bits to use to 672 determine the random offset to the base address of vma regions 673 resulting from mmap allocations for compatible applications This 674 value will be bounded by the architecture's minimum and maximum 675 supported values. 676 677 This value can be changed after boot using the 678 /proc/sys/vm/mmap_rnd_compat_bits tunable 679 680config HAVE_ARCH_COMPAT_MMAP_BASES 681 bool 682 help 683 This allows 64bit applications to invoke 32-bit mmap() syscall 684 and vice-versa 32-bit applications to call 64-bit mmap(). 685 Required for applications doing different bitness syscalls. 686 687config HAVE_COPY_THREAD_TLS 688 bool 689 help 690 Architecture provides copy_thread_tls to accept tls argument via 691 normal C parameter passing, rather than extracting the syscall 692 argument from pt_regs. 693 694config HAVE_STACK_VALIDATION 695 bool 696 help 697 Architecture supports the 'objtool check' host tool command, which 698 performs compile-time stack metadata validation. 699 700config HAVE_RELIABLE_STACKTRACE 701 bool 702 help 703 Architecture has a save_stack_trace_tsk_reliable() function which 704 only returns a stack trace if it can guarantee the trace is reliable. 705 706config HAVE_ARCH_HASH 707 bool 708 default n 709 help 710 If this is set, the architecture provides an <asm/hash.h> 711 file which provides platform-specific implementations of some 712 functions in <linux/hash.h> or fs/namei.c. 713 714config HAVE_ARCH_NVRAM_OPS 715 bool 716 717config ISA_BUS_API 718 def_bool ISA 719 720# 721# ABI hall of shame 722# 723config CLONE_BACKWARDS 724 bool 725 help 726 Architecture has tls passed as the 4th argument of clone(2), 727 not the 5th one. 728 729config CLONE_BACKWARDS2 730 bool 731 help 732 Architecture has the first two arguments of clone(2) swapped. 733 734config CLONE_BACKWARDS3 735 bool 736 help 737 Architecture has tls passed as the 3rd argument of clone(2), 738 not the 5th one. 739 740config ODD_RT_SIGACTION 741 bool 742 help 743 Architecture has unusual rt_sigaction(2) arguments 744 745config OLD_SIGSUSPEND 746 bool 747 help 748 Architecture has old sigsuspend(2) syscall, of one-argument variety 749 750config OLD_SIGSUSPEND3 751 bool 752 help 753 Even weirder antique ABI - three-argument sigsuspend(2) 754 755config OLD_SIGACTION 756 bool 757 help 758 Architecture has old sigaction(2) syscall. Nope, not the same 759 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 760 but fairly different variant of sigaction(2), thanks to OSF/1 761 compatibility... 762 763config COMPAT_OLD_SIGACTION 764 bool 765 766config 64BIT_TIME 767 def_bool ARCH_HAS_64BIT_TIME 768 help 769 This should be selected by all architectures that need to support 770 new system calls with a 64-bit time_t. This is relevant on all 32-bit 771 architectures, and 64-bit architectures as part of compat syscall 772 handling. 773 774config COMPAT_32BIT_TIME 775 def_bool !64BIT || COMPAT 776 help 777 This enables 32 bit time_t support in addition to 64 bit time_t support. 778 This is relevant on all 32-bit architectures, and 64-bit architectures 779 as part of compat syscall handling. 780 781config ARCH_NO_COHERENT_DMA_MMAP 782 bool 783 784config ARCH_NO_PREEMPT 785 bool 786 787config CPU_NO_EFFICIENT_FFS 788 def_bool n 789 790config HAVE_ARCH_VMAP_STACK 791 def_bool n 792 help 793 An arch should select this symbol if it can support kernel stacks 794 in vmalloc space. This means: 795 796 - vmalloc space must be large enough to hold many kernel stacks. 797 This may rule out many 32-bit architectures. 798 799 - Stacks in vmalloc space need to work reliably. For example, if 800 vmap page tables are created on demand, either this mechanism 801 needs to work while the stack points to a virtual address with 802 unpopulated page tables or arch code (switch_to() and switch_mm(), 803 most likely) needs to ensure that the stack's page table entries 804 are populated before running on a possibly unpopulated stack. 805 806 - If the stack overflows into a guard page, something reasonable 807 should happen. The definition of "reasonable" is flexible, but 808 instantly rebooting without logging anything would be unfriendly. 809 810config VMAP_STACK 811 default y 812 bool "Use a virtually-mapped stack" 813 depends on HAVE_ARCH_VMAP_STACK && !KASAN 814 ---help--- 815 Enable this if you want the use virtually-mapped kernel stacks 816 with guard pages. This causes kernel stack overflows to be 817 caught immediately rather than causing difficult-to-diagnose 818 corruption. 819 820 This is presently incompatible with KASAN because KASAN expects 821 the stack to map directly to the KASAN shadow map using a formula 822 that is incorrect if the stack is in vmalloc space. 823 824config ARCH_OPTIONAL_KERNEL_RWX 825 def_bool n 826 827config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 828 def_bool n 829 830config ARCH_HAS_STRICT_KERNEL_RWX 831 def_bool n 832 833config STRICT_KERNEL_RWX 834 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 835 depends on ARCH_HAS_STRICT_KERNEL_RWX 836 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 837 help 838 If this is set, kernel text and rodata memory will be made read-only, 839 and non-text memory will be made non-executable. This provides 840 protection against certain security exploits (e.g. executing the heap 841 or modifying text) 842 843 These features are considered standard security practice these days. 844 You should say Y here in almost all cases. 845 846config ARCH_HAS_STRICT_MODULE_RWX 847 def_bool n 848 849config STRICT_MODULE_RWX 850 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 851 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 852 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 853 help 854 If this is set, module text and rodata memory will be made read-only, 855 and non-text memory will be made non-executable. This provides 856 protection against certain security exploits (e.g. writing to text) 857 858# select if the architecture provides an asm/dma-direct.h header 859config ARCH_HAS_PHYS_TO_DMA 860 bool 861 862config ARCH_HAS_REFCOUNT 863 bool 864 help 865 An architecture selects this when it has implemented refcount_t 866 using open coded assembly primitives that provide an optimized 867 refcount_t implementation, possibly at the expense of some full 868 refcount state checks of CONFIG_REFCOUNT_FULL=y. 869 870 The refcount overflow check behavior, however, must be retained. 871 Catching overflows is the primary security concern for protecting 872 against bugs in reference counts. 873 874config REFCOUNT_FULL 875 bool "Perform full reference count validation at the expense of speed" 876 help 877 Enabling this switches the refcounting infrastructure from a fast 878 unchecked atomic_t implementation to a fully state checked 879 implementation, which can be (slightly) slower but provides protections 880 against various use-after-free conditions that can be used in 881 security flaw exploits. 882 883config HAVE_ARCH_COMPILER_H 884 bool 885 help 886 An architecture can select this if it provides an 887 asm/compiler.h header that should be included after 888 linux/compiler-*.h in order to override macro definitions that those 889 headers generally provide. 890 891config HAVE_ARCH_PREL32_RELOCATIONS 892 bool 893 help 894 May be selected by an architecture if it supports place-relative 895 32-bit relocations, both in the toolchain and in the module loader, 896 in which case relative references can be used in special sections 897 for PCI fixup, initcalls etc which are only half the size on 64 bit 898 architectures, and don't require runtime relocation on relocatable 899 kernels. 900 901config ARCH_USE_MEMREMAP_PROT 902 bool 903 904source "kernel/gcov/Kconfig" 905 906source "scripts/gcc-plugins/Kconfig" 907 908endmenu 909