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 has all set_direct_map_invalid/default() functions 253config ARCH_HAS_SET_DIRECT_MAP 254 bool 255 256# Select if arch init_task must go in the __init_task_data section 257config ARCH_TASK_STRUCT_ON_STACK 258 bool 259 260# Select if arch has its private alloc_task_struct() function 261config ARCH_TASK_STRUCT_ALLOCATOR 262 bool 263 264config HAVE_ARCH_THREAD_STRUCT_WHITELIST 265 bool 266 depends on !ARCH_TASK_STRUCT_ALLOCATOR 267 help 268 An architecture should select this to provide hardened usercopy 269 knowledge about what region of the thread_struct should be 270 whitelisted for copying to userspace. Normally this is only the 271 FPU registers. Specifically, arch_thread_struct_whitelist() 272 should be implemented. Without this, the entire thread_struct 273 field in task_struct will be left whitelisted. 274 275# Select if arch has its private alloc_thread_stack() function 276config ARCH_THREAD_STACK_ALLOCATOR 277 bool 278 279# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 280config ARCH_WANTS_DYNAMIC_TASK_STRUCT 281 bool 282 283config ARCH_32BIT_OFF_T 284 bool 285 depends on !64BIT 286 help 287 All new 32-bit architectures should have 64-bit off_t type on 288 userspace side which corresponds to the loff_t kernel type. This 289 is the requirement for modern ABIs. Some existing architectures 290 still support 32-bit off_t. This option is enabled for all such 291 architectures explicitly. 292 293config HAVE_REGS_AND_STACK_ACCESS_API 294 bool 295 help 296 This symbol should be selected by an architecure if it supports 297 the API needed to access registers and stack entries from pt_regs, 298 declared in asm/ptrace.h 299 For example the kprobes-based event tracer needs this API. 300 301config HAVE_RSEQ 302 bool 303 depends on HAVE_REGS_AND_STACK_ACCESS_API 304 help 305 This symbol should be selected by an architecture if it 306 supports an implementation of restartable sequences. 307 308config HAVE_FUNCTION_ARG_ACCESS_API 309 bool 310 help 311 This symbol should be selected by an architecure if it supports 312 the API needed to access function arguments from pt_regs, 313 declared in asm/ptrace.h 314 315config HAVE_CLK 316 bool 317 help 318 The <linux/clk.h> calls support software clock gating and 319 thus are a key power management tool on many systems. 320 321config HAVE_HW_BREAKPOINT 322 bool 323 depends on PERF_EVENTS 324 325config HAVE_MIXED_BREAKPOINTS_REGS 326 bool 327 depends on HAVE_HW_BREAKPOINT 328 help 329 Depending on the arch implementation of hardware breakpoints, 330 some of them have separate registers for data and instruction 331 breakpoints addresses, others have mixed registers to store 332 them but define the access type in a control register. 333 Select this option if your arch implements breakpoints under the 334 latter fashion. 335 336config HAVE_USER_RETURN_NOTIFIER 337 bool 338 339config HAVE_PERF_EVENTS_NMI 340 bool 341 help 342 System hardware can generate an NMI using the perf event 343 subsystem. Also has support for calculating CPU cycle events 344 to determine how many clock cycles in a given period. 345 346config HAVE_HARDLOCKUP_DETECTOR_PERF 347 bool 348 depends on HAVE_PERF_EVENTS_NMI 349 help 350 The arch chooses to use the generic perf-NMI-based hardlockup 351 detector. Must define HAVE_PERF_EVENTS_NMI. 352 353config HAVE_NMI_WATCHDOG 354 depends on HAVE_NMI 355 bool 356 help 357 The arch provides a low level NMI watchdog. It provides 358 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 359 360config HAVE_HARDLOCKUP_DETECTOR_ARCH 361 bool 362 select HAVE_NMI_WATCHDOG 363 help 364 The arch chooses to provide its own hardlockup detector, which is 365 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 366 interfaces and parameters provided by hardlockup detector subsystem. 367 368config HAVE_PERF_REGS 369 bool 370 help 371 Support selective register dumps for perf events. This includes 372 bit-mapping of each registers and a unique architecture id. 373 374config HAVE_PERF_USER_STACK_DUMP 375 bool 376 help 377 Support user stack dumps for perf event samples. This needs 378 access to the user stack pointer which is not unified across 379 architectures. 380 381config HAVE_ARCH_JUMP_LABEL 382 bool 383 384config HAVE_ARCH_JUMP_LABEL_RELATIVE 385 bool 386 387config HAVE_RCU_TABLE_FREE 388 bool 389 390config HAVE_RCU_TABLE_INVALIDATE 391 bool 392 393config ARCH_HAVE_NMI_SAFE_CMPXCHG 394 bool 395 396config HAVE_ALIGNED_STRUCT_PAGE 397 bool 398 help 399 This makes sure that struct pages are double word aligned and that 400 e.g. the SLUB allocator can perform double word atomic operations 401 on a struct page for better performance. However selecting this 402 might increase the size of a struct page by a word. 403 404config HAVE_CMPXCHG_LOCAL 405 bool 406 407config HAVE_CMPXCHG_DOUBLE 408 bool 409 410config ARCH_WEAK_RELEASE_ACQUIRE 411 bool 412 413config ARCH_WANT_IPC_PARSE_VERSION 414 bool 415 416config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 417 bool 418 419config ARCH_WANT_OLD_COMPAT_IPC 420 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 421 bool 422 423config HAVE_ARCH_SECCOMP_FILTER 424 bool 425 help 426 An arch should select this symbol if it provides all of these things: 427 - syscall_get_arch() 428 - syscall_get_arguments() 429 - syscall_rollback() 430 - syscall_set_return_value() 431 - SIGSYS siginfo_t support 432 - secure_computing is called from a ptrace_event()-safe context 433 - secure_computing return value is checked and a return value of -1 434 results in the system call being skipped immediately. 435 - seccomp syscall wired up 436 437config SECCOMP_FILTER 438 def_bool y 439 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 440 help 441 Enable tasks to build secure computing environments defined 442 in terms of Berkeley Packet Filter programs which implement 443 task-defined system call filtering polices. 444 445 See Documentation/userspace-api/seccomp_filter.rst for details. 446 447config HAVE_ARCH_STACKLEAK 448 bool 449 help 450 An architecture should select this if it has the code which 451 fills the used part of the kernel stack with the STACKLEAK_POISON 452 value before returning from system calls. 453 454config HAVE_STACKPROTECTOR 455 bool 456 help 457 An arch should select this symbol if: 458 - it has implemented a stack canary (e.g. __stack_chk_guard) 459 460config CC_HAS_STACKPROTECTOR_NONE 461 def_bool $(cc-option,-fno-stack-protector) 462 463config STACKPROTECTOR 464 bool "Stack Protector buffer overflow detection" 465 depends on HAVE_STACKPROTECTOR 466 depends on $(cc-option,-fstack-protector) 467 default y 468 help 469 This option turns on the "stack-protector" GCC feature. This 470 feature puts, at the beginning of functions, a canary value on 471 the stack just before the return address, and validates 472 the value just before actually returning. Stack based buffer 473 overflows (that need to overwrite this return address) now also 474 overwrite the canary, which gets detected and the attack is then 475 neutralized via a kernel panic. 476 477 Functions will have the stack-protector canary logic added if they 478 have an 8-byte or larger character array on the stack. 479 480 This feature requires gcc version 4.2 or above, or a distribution 481 gcc with the feature backported ("-fstack-protector"). 482 483 On an x86 "defconfig" build, this feature adds canary checks to 484 about 3% of all kernel functions, which increases kernel code size 485 by about 0.3%. 486 487config STACKPROTECTOR_STRONG 488 bool "Strong Stack Protector" 489 depends on STACKPROTECTOR 490 depends on $(cc-option,-fstack-protector-strong) 491 default y 492 help 493 Functions will have the stack-protector canary logic added in any 494 of the following conditions: 495 496 - local variable's address used as part of the right hand side of an 497 assignment or function argument 498 - local variable is an array (or union containing an array), 499 regardless of array type or length 500 - uses register local variables 501 502 This feature requires gcc version 4.9 or above, or a distribution 503 gcc with the feature backported ("-fstack-protector-strong"). 504 505 On an x86 "defconfig" build, this feature adds canary checks to 506 about 20% of all kernel functions, which increases the kernel code 507 size by about 2%. 508 509config HAVE_ARCH_WITHIN_STACK_FRAMES 510 bool 511 help 512 An architecture should select this if it can walk the kernel stack 513 frames to determine if an object is part of either the arguments 514 or local variables (i.e. that it excludes saved return addresses, 515 and similar) by implementing an inline arch_within_stack_frames(), 516 which is used by CONFIG_HARDENED_USERCOPY. 517 518config HAVE_CONTEXT_TRACKING 519 bool 520 help 521 Provide kernel/user boundaries probes necessary for subsystems 522 that need it, such as userspace RCU extended quiescent state. 523 Syscalls need to be wrapped inside user_exit()-user_enter() through 524 the slow path using TIF_NOHZ flag. Exceptions handlers must be 525 wrapped as well. Irqs are already protected inside 526 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 527 irq exit still need to be protected. 528 529config HAVE_VIRT_CPU_ACCOUNTING 530 bool 531 532config ARCH_HAS_SCALED_CPUTIME 533 bool 534 535config HAVE_VIRT_CPU_ACCOUNTING_GEN 536 bool 537 default y if 64BIT 538 help 539 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 540 Before enabling this option, arch code must be audited 541 to ensure there are no races in concurrent read/write of 542 cputime_t. For example, reading/writing 64-bit cputime_t on 543 some 32-bit arches may require multiple accesses, so proper 544 locking is needed to protect against concurrent accesses. 545 546 547config HAVE_IRQ_TIME_ACCOUNTING 548 bool 549 help 550 Archs need to ensure they use a high enough resolution clock to 551 support irq time accounting and then call enable_sched_clock_irqtime(). 552 553config HAVE_MOVE_PMD 554 bool 555 help 556 Archs that select this are able to move page tables at the PMD level. 557 558config HAVE_ARCH_TRANSPARENT_HUGEPAGE 559 bool 560 561config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 562 bool 563 564config HAVE_ARCH_HUGE_VMAP 565 bool 566 567config HAVE_ARCH_SOFT_DIRTY 568 bool 569 570config HAVE_MOD_ARCH_SPECIFIC 571 bool 572 help 573 The arch uses struct mod_arch_specific to store data. Many arches 574 just need a simple module loader without arch specific data - those 575 should not enable this. 576 577config MODULES_USE_ELF_RELA 578 bool 579 help 580 Modules only use ELF RELA relocations. Modules with ELF REL 581 relocations will give an error. 582 583config MODULES_USE_ELF_REL 584 bool 585 help 586 Modules only use ELF REL relocations. Modules with ELF RELA 587 relocations will give an error. 588 589config HAVE_IRQ_EXIT_ON_IRQ_STACK 590 bool 591 help 592 Architecture doesn't only execute the irq handler on the irq stack 593 but also irq_exit(). This way we can process softirqs on this irq 594 stack instead of switching to a new one when we call __do_softirq() 595 in the end of an hardirq. 596 This spares a stack switch and improves cache usage on softirq 597 processing. 598 599config PGTABLE_LEVELS 600 int 601 default 2 602 603config ARCH_HAS_ELF_RANDOMIZE 604 bool 605 help 606 An architecture supports choosing randomized locations for 607 stack, mmap, brk, and ET_DYN. Defined functions: 608 - arch_mmap_rnd() 609 - arch_randomize_brk() 610 611config HAVE_ARCH_MMAP_RND_BITS 612 bool 613 help 614 An arch should select this symbol if it supports setting a variable 615 number of bits for use in establishing the base address for mmap 616 allocations, has MMU enabled and provides values for both: 617 - ARCH_MMAP_RND_BITS_MIN 618 - ARCH_MMAP_RND_BITS_MAX 619 620config HAVE_EXIT_THREAD 621 bool 622 help 623 An architecture implements exit_thread. 624 625config ARCH_MMAP_RND_BITS_MIN 626 int 627 628config ARCH_MMAP_RND_BITS_MAX 629 int 630 631config ARCH_MMAP_RND_BITS_DEFAULT 632 int 633 634config ARCH_MMAP_RND_BITS 635 int "Number of bits to use for ASLR of mmap base address" if EXPERT 636 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 637 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 638 default ARCH_MMAP_RND_BITS_MIN 639 depends on HAVE_ARCH_MMAP_RND_BITS 640 help 641 This value can be used to select the number of bits to use to 642 determine the random offset to the base address of vma regions 643 resulting from mmap allocations. This value will be bounded 644 by the architecture's minimum and maximum supported values. 645 646 This value can be changed after boot using the 647 /proc/sys/vm/mmap_rnd_bits tunable 648 649config HAVE_ARCH_MMAP_RND_COMPAT_BITS 650 bool 651 help 652 An arch should select this symbol if it supports running applications 653 in compatibility mode, supports setting a variable number of bits for 654 use in establishing the base address for mmap allocations, has MMU 655 enabled and provides values for both: 656 - ARCH_MMAP_RND_COMPAT_BITS_MIN 657 - ARCH_MMAP_RND_COMPAT_BITS_MAX 658 659config ARCH_MMAP_RND_COMPAT_BITS_MIN 660 int 661 662config ARCH_MMAP_RND_COMPAT_BITS_MAX 663 int 664 665config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 666 int 667 668config ARCH_MMAP_RND_COMPAT_BITS 669 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 670 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 671 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 672 default ARCH_MMAP_RND_COMPAT_BITS_MIN 673 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 674 help 675 This value can be used to select the number of bits to use to 676 determine the random offset to the base address of vma regions 677 resulting from mmap allocations for compatible applications This 678 value will be bounded by the architecture's minimum and maximum 679 supported values. 680 681 This value can be changed after boot using the 682 /proc/sys/vm/mmap_rnd_compat_bits tunable 683 684config HAVE_ARCH_COMPAT_MMAP_BASES 685 bool 686 help 687 This allows 64bit applications to invoke 32-bit mmap() syscall 688 and vice-versa 32-bit applications to call 64-bit mmap(). 689 Required for applications doing different bitness syscalls. 690 691config HAVE_COPY_THREAD_TLS 692 bool 693 help 694 Architecture provides copy_thread_tls to accept tls argument via 695 normal C parameter passing, rather than extracting the syscall 696 argument from pt_regs. 697 698config HAVE_STACK_VALIDATION 699 bool 700 help 701 Architecture supports the 'objtool check' host tool command, which 702 performs compile-time stack metadata validation. 703 704config HAVE_RELIABLE_STACKTRACE 705 bool 706 help 707 Architecture has a save_stack_trace_tsk_reliable() function which 708 only returns a stack trace if it can guarantee the trace is reliable. 709 710config HAVE_ARCH_HASH 711 bool 712 default n 713 help 714 If this is set, the architecture provides an <asm/hash.h> 715 file which provides platform-specific implementations of some 716 functions in <linux/hash.h> or fs/namei.c. 717 718config HAVE_ARCH_NVRAM_OPS 719 bool 720 721config ISA_BUS_API 722 def_bool ISA 723 724# 725# ABI hall of shame 726# 727config CLONE_BACKWARDS 728 bool 729 help 730 Architecture has tls passed as the 4th argument of clone(2), 731 not the 5th one. 732 733config CLONE_BACKWARDS2 734 bool 735 help 736 Architecture has the first two arguments of clone(2) swapped. 737 738config CLONE_BACKWARDS3 739 bool 740 help 741 Architecture has tls passed as the 3rd argument of clone(2), 742 not the 5th one. 743 744config ODD_RT_SIGACTION 745 bool 746 help 747 Architecture has unusual rt_sigaction(2) arguments 748 749config OLD_SIGSUSPEND 750 bool 751 help 752 Architecture has old sigsuspend(2) syscall, of one-argument variety 753 754config OLD_SIGSUSPEND3 755 bool 756 help 757 Even weirder antique ABI - three-argument sigsuspend(2) 758 759config OLD_SIGACTION 760 bool 761 help 762 Architecture has old sigaction(2) syscall. Nope, not the same 763 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 764 but fairly different variant of sigaction(2), thanks to OSF/1 765 compatibility... 766 767config COMPAT_OLD_SIGACTION 768 bool 769 770config 64BIT_TIME 771 def_bool ARCH_HAS_64BIT_TIME 772 help 773 This should be selected by all architectures that need to support 774 new system calls with a 64-bit time_t. This is relevant on all 32-bit 775 architectures, and 64-bit architectures as part of compat syscall 776 handling. 777 778config COMPAT_32BIT_TIME 779 def_bool !64BIT || COMPAT 780 help 781 This enables 32 bit time_t support in addition to 64 bit time_t support. 782 This is relevant on all 32-bit architectures, and 64-bit architectures 783 as part of compat syscall handling. 784 785config ARCH_NO_COHERENT_DMA_MMAP 786 bool 787 788config ARCH_NO_PREEMPT 789 bool 790 791config CPU_NO_EFFICIENT_FFS 792 def_bool n 793 794config HAVE_ARCH_VMAP_STACK 795 def_bool n 796 help 797 An arch should select this symbol if it can support kernel stacks 798 in vmalloc space. This means: 799 800 - vmalloc space must be large enough to hold many kernel stacks. 801 This may rule out many 32-bit architectures. 802 803 - Stacks in vmalloc space need to work reliably. For example, if 804 vmap page tables are created on demand, either this mechanism 805 needs to work while the stack points to a virtual address with 806 unpopulated page tables or arch code (switch_to() and switch_mm(), 807 most likely) needs to ensure that the stack's page table entries 808 are populated before running on a possibly unpopulated stack. 809 810 - If the stack overflows into a guard page, something reasonable 811 should happen. The definition of "reasonable" is flexible, but 812 instantly rebooting without logging anything would be unfriendly. 813 814config VMAP_STACK 815 default y 816 bool "Use a virtually-mapped stack" 817 depends on HAVE_ARCH_VMAP_STACK && !KASAN 818 ---help--- 819 Enable this if you want the use virtually-mapped kernel stacks 820 with guard pages. This causes kernel stack overflows to be 821 caught immediately rather than causing difficult-to-diagnose 822 corruption. 823 824 This is presently incompatible with KASAN because KASAN expects 825 the stack to map directly to the KASAN shadow map using a formula 826 that is incorrect if the stack is in vmalloc space. 827 828config ARCH_OPTIONAL_KERNEL_RWX 829 def_bool n 830 831config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 832 def_bool n 833 834config ARCH_HAS_STRICT_KERNEL_RWX 835 def_bool n 836 837config STRICT_KERNEL_RWX 838 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 839 depends on ARCH_HAS_STRICT_KERNEL_RWX 840 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 841 help 842 If this is set, kernel text and rodata memory will be made read-only, 843 and non-text memory will be made non-executable. This provides 844 protection against certain security exploits (e.g. executing the heap 845 or modifying text) 846 847 These features are considered standard security practice these days. 848 You should say Y here in almost all cases. 849 850config ARCH_HAS_STRICT_MODULE_RWX 851 def_bool n 852 853config STRICT_MODULE_RWX 854 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 855 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 856 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 857 help 858 If this is set, module text and rodata memory will be made read-only, 859 and non-text memory will be made non-executable. This provides 860 protection against certain security exploits (e.g. writing to text) 861 862# select if the architecture provides an asm/dma-direct.h header 863config ARCH_HAS_PHYS_TO_DMA 864 bool 865 866config ARCH_HAS_REFCOUNT 867 bool 868 help 869 An architecture selects this when it has implemented refcount_t 870 using open coded assembly primitives that provide an optimized 871 refcount_t implementation, possibly at the expense of some full 872 refcount state checks of CONFIG_REFCOUNT_FULL=y. 873 874 The refcount overflow check behavior, however, must be retained. 875 Catching overflows is the primary security concern for protecting 876 against bugs in reference counts. 877 878config REFCOUNT_FULL 879 bool "Perform full reference count validation at the expense of speed" 880 help 881 Enabling this switches the refcounting infrastructure from a fast 882 unchecked atomic_t implementation to a fully state checked 883 implementation, which can be (slightly) slower but provides protections 884 against various use-after-free conditions that can be used in 885 security flaw exploits. 886 887config HAVE_ARCH_COMPILER_H 888 bool 889 help 890 An architecture can select this if it provides an 891 asm/compiler.h header that should be included after 892 linux/compiler-*.h in order to override macro definitions that those 893 headers generally provide. 894 895config HAVE_ARCH_PREL32_RELOCATIONS 896 bool 897 help 898 May be selected by an architecture if it supports place-relative 899 32-bit relocations, both in the toolchain and in the module loader, 900 in which case relative references can be used in special sections 901 for PCI fixup, initcalls etc which are only half the size on 64 bit 902 architectures, and don't require runtime relocation on relocatable 903 kernels. 904 905config ARCH_USE_MEMREMAP_PROT 906 bool 907 908source "kernel/gcov/Kconfig" 909 910source "scripts/gcc-plugins/Kconfig" 911 912endmenu 913