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_EFFICIENT_UNALIGNED_ACCESS 132 bool 133 help 134 Some architectures are unable to perform unaligned accesses 135 without the use of get_unaligned/put_unaligned. Others are 136 unable to perform such accesses efficiently (e.g. trap on 137 unaligned access and require fixing it up in the exception 138 handler.) 139 140 This symbol should be selected by an architecture if it can 141 perform unaligned accesses efficiently to allow different 142 code paths to be selected for these cases. Some network 143 drivers, for example, could opt to not fix up alignment 144 problems with received packets if doing so would not help 145 much. 146 147 See Documentation/unaligned-memory-access.txt for more 148 information on the topic of unaligned memory accesses. 149 150config ARCH_USE_BUILTIN_BSWAP 151 bool 152 help 153 Modern versions of GCC (since 4.4) have builtin functions 154 for handling byte-swapping. Using these, instead of the old 155 inline assembler that the architecture code provides in the 156 __arch_bswapXX() macros, allows the compiler to see what's 157 happening and offers more opportunity for optimisation. In 158 particular, the compiler will be able to combine the byteswap 159 with a nearby load or store and use load-and-swap or 160 store-and-swap instructions if the architecture has them. It 161 should almost *never* result in code which is worse than the 162 hand-coded assembler in <asm/swab.h>. But just in case it 163 does, the use of the builtins is optional. 164 165 Any architecture with load-and-swap or store-and-swap 166 instructions should set this. And it shouldn't hurt to set it 167 on architectures that don't have such instructions. 168 169config KRETPROBES 170 def_bool y 171 depends on KPROBES && HAVE_KRETPROBES 172 173config USER_RETURN_NOTIFIER 174 bool 175 depends on HAVE_USER_RETURN_NOTIFIER 176 help 177 Provide a kernel-internal notification when a cpu is about to 178 switch to user mode. 179 180config HAVE_IOREMAP_PROT 181 bool 182 183config HAVE_KPROBES 184 bool 185 186config HAVE_KRETPROBES 187 bool 188 189config HAVE_OPTPROBES 190 bool 191 192config HAVE_KPROBES_ON_FTRACE 193 bool 194 195config HAVE_FUNCTION_ERROR_INJECTION 196 bool 197 198config HAVE_NMI 199 bool 200 201# 202# An arch should select this if it provides all these things: 203# 204# task_pt_regs() in asm/processor.h or asm/ptrace.h 205# arch_has_single_step() if there is hardware single-step support 206# arch_has_block_step() if there is hardware block-step support 207# asm/syscall.h supplying asm-generic/syscall.h interface 208# linux/regset.h user_regset interfaces 209# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 210# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 211# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 212# signal delivery calls tracehook_signal_handler() 213# 214config HAVE_ARCH_TRACEHOOK 215 bool 216 217config HAVE_DMA_CONTIGUOUS 218 bool 219 220config GENERIC_SMP_IDLE_THREAD 221 bool 222 223config GENERIC_IDLE_POLL_SETUP 224 bool 225 226config ARCH_HAS_FORTIFY_SOURCE 227 bool 228 help 229 An architecture should select this when it can successfully 230 build and run with CONFIG_FORTIFY_SOURCE. 231 232# 233# Select if the arch provides a historic keepinit alias for the retain_initrd 234# command line option 235# 236config ARCH_HAS_KEEPINITRD 237 bool 238 239# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 240config ARCH_HAS_SET_MEMORY 241 bool 242 243# Select if arch has all set_direct_map_invalid/default() functions 244config ARCH_HAS_SET_DIRECT_MAP 245 bool 246 247# 248# Select if arch has an uncached kernel segment and provides the 249# uncached_kernel_address / cached_kernel_address symbols to use it 250# 251config ARCH_HAS_UNCACHED_SEGMENT 252 select ARCH_HAS_DMA_PREP_COHERENT 253 bool 254 255# Select if arch init_task must go in the __init_task_data section 256config ARCH_TASK_STRUCT_ON_STACK 257 bool 258 259# Select if arch has its private alloc_task_struct() function 260config ARCH_TASK_STRUCT_ALLOCATOR 261 bool 262 263config HAVE_ARCH_THREAD_STRUCT_WHITELIST 264 bool 265 depends on !ARCH_TASK_STRUCT_ALLOCATOR 266 help 267 An architecture should select this to provide hardened usercopy 268 knowledge about what region of the thread_struct should be 269 whitelisted for copying to userspace. Normally this is only the 270 FPU registers. Specifically, arch_thread_struct_whitelist() 271 should be implemented. Without this, the entire thread_struct 272 field in task_struct will be left whitelisted. 273 274# Select if arch has its private alloc_thread_stack() function 275config ARCH_THREAD_STACK_ALLOCATOR 276 bool 277 278# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 279config ARCH_WANTS_DYNAMIC_TASK_STRUCT 280 bool 281 282config ARCH_32BIT_OFF_T 283 bool 284 depends on !64BIT 285 help 286 All new 32-bit architectures should have 64-bit off_t type on 287 userspace side which corresponds to the loff_t kernel type. This 288 is the requirement for modern ABIs. Some existing architectures 289 still support 32-bit off_t. This option is enabled for all such 290 architectures explicitly. 291 292config HAVE_ASM_MODVERSIONS 293 bool 294 help 295 This symbol should be selected by an architecure if it provides 296 <asm/asm-prototypes.h> to support the module versioning for symbols 297 exported from assembly code. 298 299config HAVE_REGS_AND_STACK_ACCESS_API 300 bool 301 help 302 This symbol should be selected by an architecure if it supports 303 the API needed to access registers and stack entries from pt_regs, 304 declared in asm/ptrace.h 305 For example the kprobes-based event tracer needs this API. 306 307config HAVE_RSEQ 308 bool 309 depends on HAVE_REGS_AND_STACK_ACCESS_API 310 help 311 This symbol should be selected by an architecture if it 312 supports an implementation of restartable sequences. 313 314config HAVE_FUNCTION_ARG_ACCESS_API 315 bool 316 help 317 This symbol should be selected by an architecure if it supports 318 the API needed to access function arguments from pt_regs, 319 declared in asm/ptrace.h 320 321config HAVE_CLK 322 bool 323 help 324 The <linux/clk.h> calls support software clock gating and 325 thus are a key power management tool on many systems. 326 327config HAVE_HW_BREAKPOINT 328 bool 329 depends on PERF_EVENTS 330 331config HAVE_MIXED_BREAKPOINTS_REGS 332 bool 333 depends on HAVE_HW_BREAKPOINT 334 help 335 Depending on the arch implementation of hardware breakpoints, 336 some of them have separate registers for data and instruction 337 breakpoints addresses, others have mixed registers to store 338 them but define the access type in a control register. 339 Select this option if your arch implements breakpoints under the 340 latter fashion. 341 342config HAVE_USER_RETURN_NOTIFIER 343 bool 344 345config HAVE_PERF_EVENTS_NMI 346 bool 347 help 348 System hardware can generate an NMI using the perf event 349 subsystem. Also has support for calculating CPU cycle events 350 to determine how many clock cycles in a given period. 351 352config HAVE_HARDLOCKUP_DETECTOR_PERF 353 bool 354 depends on HAVE_PERF_EVENTS_NMI 355 help 356 The arch chooses to use the generic perf-NMI-based hardlockup 357 detector. Must define HAVE_PERF_EVENTS_NMI. 358 359config HAVE_NMI_WATCHDOG 360 depends on HAVE_NMI 361 bool 362 help 363 The arch provides a low level NMI watchdog. It provides 364 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 365 366config HAVE_HARDLOCKUP_DETECTOR_ARCH 367 bool 368 select HAVE_NMI_WATCHDOG 369 help 370 The arch chooses to provide its own hardlockup detector, which is 371 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 372 interfaces and parameters provided by hardlockup detector subsystem. 373 374config HAVE_PERF_REGS 375 bool 376 help 377 Support selective register dumps for perf events. This includes 378 bit-mapping of each registers and a unique architecture id. 379 380config HAVE_PERF_USER_STACK_DUMP 381 bool 382 help 383 Support user stack dumps for perf event samples. This needs 384 access to the user stack pointer which is not unified across 385 architectures. 386 387config HAVE_ARCH_JUMP_LABEL 388 bool 389 390config HAVE_ARCH_JUMP_LABEL_RELATIVE 391 bool 392 393config HAVE_RCU_TABLE_FREE 394 bool 395 396config HAVE_RCU_TABLE_NO_INVALIDATE 397 bool 398 399config HAVE_MMU_GATHER_PAGE_SIZE 400 bool 401 402config HAVE_MMU_GATHER_NO_GATHER 403 bool 404 405config ARCH_HAVE_NMI_SAFE_CMPXCHG 406 bool 407 408config HAVE_ALIGNED_STRUCT_PAGE 409 bool 410 help 411 This makes sure that struct pages are double word aligned and that 412 e.g. the SLUB allocator can perform double word atomic operations 413 on a struct page for better performance. However selecting this 414 might increase the size of a struct page by a word. 415 416config HAVE_CMPXCHG_LOCAL 417 bool 418 419config HAVE_CMPXCHG_DOUBLE 420 bool 421 422config ARCH_WEAK_RELEASE_ACQUIRE 423 bool 424 425config ARCH_WANT_IPC_PARSE_VERSION 426 bool 427 428config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 429 bool 430 431config ARCH_WANT_OLD_COMPAT_IPC 432 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 433 bool 434 435config HAVE_ARCH_SECCOMP_FILTER 436 bool 437 help 438 An arch should select this symbol if it provides all of these things: 439 - syscall_get_arch() 440 - syscall_get_arguments() 441 - syscall_rollback() 442 - syscall_set_return_value() 443 - SIGSYS siginfo_t support 444 - secure_computing is called from a ptrace_event()-safe context 445 - secure_computing return value is checked and a return value of -1 446 results in the system call being skipped immediately. 447 - seccomp syscall wired up 448 449config SECCOMP_FILTER 450 def_bool y 451 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 452 help 453 Enable tasks to build secure computing environments defined 454 in terms of Berkeley Packet Filter programs which implement 455 task-defined system call filtering polices. 456 457 See Documentation/userspace-api/seccomp_filter.rst for details. 458 459config HAVE_ARCH_STACKLEAK 460 bool 461 help 462 An architecture should select this if it has the code which 463 fills the used part of the kernel stack with the STACKLEAK_POISON 464 value before returning from system calls. 465 466config HAVE_STACKPROTECTOR 467 bool 468 help 469 An arch should select this symbol if: 470 - it has implemented a stack canary (e.g. __stack_chk_guard) 471 472config CC_HAS_STACKPROTECTOR_NONE 473 def_bool $(cc-option,-fno-stack-protector) 474 475config STACKPROTECTOR 476 bool "Stack Protector buffer overflow detection" 477 depends on HAVE_STACKPROTECTOR 478 depends on $(cc-option,-fstack-protector) 479 default y 480 help 481 This option turns on the "stack-protector" GCC feature. This 482 feature puts, at the beginning of functions, a canary value on 483 the stack just before the return address, and validates 484 the value just before actually returning. Stack based buffer 485 overflows (that need to overwrite this return address) now also 486 overwrite the canary, which gets detected and the attack is then 487 neutralized via a kernel panic. 488 489 Functions will have the stack-protector canary logic added if they 490 have an 8-byte or larger character array on the stack. 491 492 This feature requires gcc version 4.2 or above, or a distribution 493 gcc with the feature backported ("-fstack-protector"). 494 495 On an x86 "defconfig" build, this feature adds canary checks to 496 about 3% of all kernel functions, which increases kernel code size 497 by about 0.3%. 498 499config STACKPROTECTOR_STRONG 500 bool "Strong Stack Protector" 501 depends on STACKPROTECTOR 502 depends on $(cc-option,-fstack-protector-strong) 503 default y 504 help 505 Functions will have the stack-protector canary logic added in any 506 of the following conditions: 507 508 - local variable's address used as part of the right hand side of an 509 assignment or function argument 510 - local variable is an array (or union containing an array), 511 regardless of array type or length 512 - uses register local variables 513 514 This feature requires gcc version 4.9 or above, or a distribution 515 gcc with the feature backported ("-fstack-protector-strong"). 516 517 On an x86 "defconfig" build, this feature adds canary checks to 518 about 20% of all kernel functions, which increases the kernel code 519 size by about 2%. 520 521config HAVE_ARCH_WITHIN_STACK_FRAMES 522 bool 523 help 524 An architecture should select this if it can walk the kernel stack 525 frames to determine if an object is part of either the arguments 526 or local variables (i.e. that it excludes saved return addresses, 527 and similar) by implementing an inline arch_within_stack_frames(), 528 which is used by CONFIG_HARDENED_USERCOPY. 529 530config HAVE_CONTEXT_TRACKING 531 bool 532 help 533 Provide kernel/user boundaries probes necessary for subsystems 534 that need it, such as userspace RCU extended quiescent state. 535 Syscalls need to be wrapped inside user_exit()-user_enter() through 536 the slow path using TIF_NOHZ flag. Exceptions handlers must be 537 wrapped as well. Irqs are already protected inside 538 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 539 irq exit still need to be protected. 540 541config HAVE_VIRT_CPU_ACCOUNTING 542 bool 543 544config ARCH_HAS_SCALED_CPUTIME 545 bool 546 547config HAVE_VIRT_CPU_ACCOUNTING_GEN 548 bool 549 default y if 64BIT 550 help 551 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 552 Before enabling this option, arch code must be audited 553 to ensure there are no races in concurrent read/write of 554 cputime_t. For example, reading/writing 64-bit cputime_t on 555 some 32-bit arches may require multiple accesses, so proper 556 locking is needed to protect against concurrent accesses. 557 558 559config HAVE_IRQ_TIME_ACCOUNTING 560 bool 561 help 562 Archs need to ensure they use a high enough resolution clock to 563 support irq time accounting and then call enable_sched_clock_irqtime(). 564 565config HAVE_MOVE_PMD 566 bool 567 help 568 Archs that select this are able to move page tables at the PMD level. 569 570config HAVE_ARCH_TRANSPARENT_HUGEPAGE 571 bool 572 573config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 574 bool 575 576config HAVE_ARCH_HUGE_VMAP 577 bool 578 579config ARCH_WANT_HUGE_PMD_SHARE 580 bool 581 582config HAVE_ARCH_SOFT_DIRTY 583 bool 584 585config HAVE_MOD_ARCH_SPECIFIC 586 bool 587 help 588 The arch uses struct mod_arch_specific to store data. Many arches 589 just need a simple module loader without arch specific data - those 590 should not enable this. 591 592config MODULES_USE_ELF_RELA 593 bool 594 help 595 Modules only use ELF RELA relocations. Modules with ELF REL 596 relocations will give an error. 597 598config MODULES_USE_ELF_REL 599 bool 600 help 601 Modules only use ELF REL relocations. Modules with ELF RELA 602 relocations will give an error. 603 604config HAVE_IRQ_EXIT_ON_IRQ_STACK 605 bool 606 help 607 Architecture doesn't only execute the irq handler on the irq stack 608 but also irq_exit(). This way we can process softirqs on this irq 609 stack instead of switching to a new one when we call __do_softirq() 610 in the end of an hardirq. 611 This spares a stack switch and improves cache usage on softirq 612 processing. 613 614config PGTABLE_LEVELS 615 int 616 default 2 617 618config ARCH_HAS_ELF_RANDOMIZE 619 bool 620 help 621 An architecture supports choosing randomized locations for 622 stack, mmap, brk, and ET_DYN. Defined functions: 623 - arch_mmap_rnd() 624 - arch_randomize_brk() 625 626config HAVE_ARCH_MMAP_RND_BITS 627 bool 628 help 629 An arch should select this symbol if it supports setting a variable 630 number of bits for use in establishing the base address for mmap 631 allocations, has MMU enabled and provides values for both: 632 - ARCH_MMAP_RND_BITS_MIN 633 - ARCH_MMAP_RND_BITS_MAX 634 635config HAVE_EXIT_THREAD 636 bool 637 help 638 An architecture implements exit_thread. 639 640config ARCH_MMAP_RND_BITS_MIN 641 int 642 643config ARCH_MMAP_RND_BITS_MAX 644 int 645 646config ARCH_MMAP_RND_BITS_DEFAULT 647 int 648 649config ARCH_MMAP_RND_BITS 650 int "Number of bits to use for ASLR of mmap base address" if EXPERT 651 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 652 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 653 default ARCH_MMAP_RND_BITS_MIN 654 depends on HAVE_ARCH_MMAP_RND_BITS 655 help 656 This value can be used to select the number of bits to use to 657 determine the random offset to the base address of vma regions 658 resulting from mmap allocations. This value will be bounded 659 by the architecture's minimum and maximum supported values. 660 661 This value can be changed after boot using the 662 /proc/sys/vm/mmap_rnd_bits tunable 663 664config HAVE_ARCH_MMAP_RND_COMPAT_BITS 665 bool 666 help 667 An arch should select this symbol if it supports running applications 668 in compatibility mode, supports setting a variable number of bits for 669 use in establishing the base address for mmap allocations, has MMU 670 enabled and provides values for both: 671 - ARCH_MMAP_RND_COMPAT_BITS_MIN 672 - ARCH_MMAP_RND_COMPAT_BITS_MAX 673 674config ARCH_MMAP_RND_COMPAT_BITS_MIN 675 int 676 677config ARCH_MMAP_RND_COMPAT_BITS_MAX 678 int 679 680config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 681 int 682 683config ARCH_MMAP_RND_COMPAT_BITS 684 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 685 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 686 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 687 default ARCH_MMAP_RND_COMPAT_BITS_MIN 688 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 689 help 690 This value can be used to select the number of bits to use to 691 determine the random offset to the base address of vma regions 692 resulting from mmap allocations for compatible applications This 693 value will be bounded by the architecture's minimum and maximum 694 supported values. 695 696 This value can be changed after boot using the 697 /proc/sys/vm/mmap_rnd_compat_bits tunable 698 699config HAVE_ARCH_COMPAT_MMAP_BASES 700 bool 701 help 702 This allows 64bit applications to invoke 32-bit mmap() syscall 703 and vice-versa 32-bit applications to call 64-bit mmap(). 704 Required for applications doing different bitness syscalls. 705 706config HAVE_COPY_THREAD_TLS 707 bool 708 help 709 Architecture provides copy_thread_tls to accept tls argument via 710 normal C parameter passing, rather than extracting the syscall 711 argument from pt_regs. 712 713config HAVE_STACK_VALIDATION 714 bool 715 help 716 Architecture supports the 'objtool check' host tool command, which 717 performs compile-time stack metadata validation. 718 719config HAVE_RELIABLE_STACKTRACE 720 bool 721 help 722 Architecture has a save_stack_trace_tsk_reliable() function which 723 only returns a stack trace if it can guarantee the trace is reliable. 724 725config HAVE_ARCH_HASH 726 bool 727 default n 728 help 729 If this is set, the architecture provides an <asm/hash.h> 730 file which provides platform-specific implementations of some 731 functions in <linux/hash.h> or fs/namei.c. 732 733config HAVE_ARCH_NVRAM_OPS 734 bool 735 736config ISA_BUS_API 737 def_bool ISA 738 739# 740# ABI hall of shame 741# 742config CLONE_BACKWARDS 743 bool 744 help 745 Architecture has tls passed as the 4th argument of clone(2), 746 not the 5th one. 747 748config CLONE_BACKWARDS2 749 bool 750 help 751 Architecture has the first two arguments of clone(2) swapped. 752 753config CLONE_BACKWARDS3 754 bool 755 help 756 Architecture has tls passed as the 3rd argument of clone(2), 757 not the 5th one. 758 759config ODD_RT_SIGACTION 760 bool 761 help 762 Architecture has unusual rt_sigaction(2) arguments 763 764config OLD_SIGSUSPEND 765 bool 766 help 767 Architecture has old sigsuspend(2) syscall, of one-argument variety 768 769config OLD_SIGSUSPEND3 770 bool 771 help 772 Even weirder antique ABI - three-argument sigsuspend(2) 773 774config OLD_SIGACTION 775 bool 776 help 777 Architecture has old sigaction(2) syscall. Nope, not the same 778 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 779 but fairly different variant of sigaction(2), thanks to OSF/1 780 compatibility... 781 782config COMPAT_OLD_SIGACTION 783 bool 784 785config 64BIT_TIME 786 def_bool y 787 help 788 This should be selected by all architectures that need to support 789 new system calls with a 64-bit time_t. This is relevant on all 32-bit 790 architectures, and 64-bit architectures as part of compat syscall 791 handling. 792 793config COMPAT_32BIT_TIME 794 def_bool !64BIT || COMPAT 795 help 796 This enables 32 bit time_t support in addition to 64 bit time_t support. 797 This is relevant on all 32-bit architectures, and 64-bit architectures 798 as part of compat syscall handling. 799 800config ARCH_NO_COHERENT_DMA_MMAP 801 bool 802 803config ARCH_NO_PREEMPT 804 bool 805 806config ARCH_SUPPORTS_RT 807 bool 808 809config CPU_NO_EFFICIENT_FFS 810 def_bool n 811 812config HAVE_ARCH_VMAP_STACK 813 def_bool n 814 help 815 An arch should select this symbol if it can support kernel stacks 816 in vmalloc space. This means: 817 818 - vmalloc space must be large enough to hold many kernel stacks. 819 This may rule out many 32-bit architectures. 820 821 - Stacks in vmalloc space need to work reliably. For example, if 822 vmap page tables are created on demand, either this mechanism 823 needs to work while the stack points to a virtual address with 824 unpopulated page tables or arch code (switch_to() and switch_mm(), 825 most likely) needs to ensure that the stack's page table entries 826 are populated before running on a possibly unpopulated stack. 827 828 - If the stack overflows into a guard page, something reasonable 829 should happen. The definition of "reasonable" is flexible, but 830 instantly rebooting without logging anything would be unfriendly. 831 832config VMAP_STACK 833 default y 834 bool "Use a virtually-mapped stack" 835 depends on HAVE_ARCH_VMAP_STACK && !KASAN 836 ---help--- 837 Enable this if you want the use virtually-mapped kernel stacks 838 with guard pages. This causes kernel stack overflows to be 839 caught immediately rather than causing difficult-to-diagnose 840 corruption. 841 842 This is presently incompatible with KASAN because KASAN expects 843 the stack to map directly to the KASAN shadow map using a formula 844 that is incorrect if the stack is in vmalloc space. 845 846config ARCH_OPTIONAL_KERNEL_RWX 847 def_bool n 848 849config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 850 def_bool n 851 852config ARCH_HAS_STRICT_KERNEL_RWX 853 def_bool n 854 855config STRICT_KERNEL_RWX 856 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 857 depends on ARCH_HAS_STRICT_KERNEL_RWX 858 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 859 help 860 If this is set, kernel text and rodata memory will be made read-only, 861 and non-text memory will be made non-executable. This provides 862 protection against certain security exploits (e.g. executing the heap 863 or modifying text) 864 865 These features are considered standard security practice these days. 866 You should say Y here in almost all cases. 867 868config ARCH_HAS_STRICT_MODULE_RWX 869 def_bool n 870 871config STRICT_MODULE_RWX 872 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 873 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 874 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 875 help 876 If this is set, module text and rodata memory will be made read-only, 877 and non-text memory will be made non-executable. This provides 878 protection against certain security exploits (e.g. writing to text) 879 880# select if the architecture provides an asm/dma-direct.h header 881config ARCH_HAS_PHYS_TO_DMA 882 bool 883 884config ARCH_HAS_REFCOUNT 885 bool 886 help 887 An architecture selects this when it has implemented refcount_t 888 using open coded assembly primitives that provide an optimized 889 refcount_t implementation, possibly at the expense of some full 890 refcount state checks of CONFIG_REFCOUNT_FULL=y. 891 892 The refcount overflow check behavior, however, must be retained. 893 Catching overflows is the primary security concern for protecting 894 against bugs in reference counts. 895 896config REFCOUNT_FULL 897 bool "Perform full reference count validation at the expense of speed" 898 help 899 Enabling this switches the refcounting infrastructure from a fast 900 unchecked atomic_t implementation to a fully state checked 901 implementation, which can be (slightly) slower but provides protections 902 against various use-after-free conditions that can be used in 903 security flaw exploits. 904 905config HAVE_ARCH_COMPILER_H 906 bool 907 help 908 An architecture can select this if it provides an 909 asm/compiler.h header that should be included after 910 linux/compiler-*.h in order to override macro definitions that those 911 headers generally provide. 912 913config HAVE_ARCH_PREL32_RELOCATIONS 914 bool 915 help 916 May be selected by an architecture if it supports place-relative 917 32-bit relocations, both in the toolchain and in the module loader, 918 in which case relative references can be used in special sections 919 for PCI fixup, initcalls etc which are only half the size on 64 bit 920 architectures, and don't require runtime relocation on relocatable 921 kernels. 922 923config ARCH_USE_MEMREMAP_PROT 924 bool 925 926config LOCK_EVENT_COUNTS 927 bool "Locking event counts collection" 928 depends on DEBUG_FS 929 ---help--- 930 Enable light-weight counting of various locking related events 931 in the system with minimal performance impact. This reduces 932 the chance of application behavior change because of timing 933 differences. The counts are reported via debugfs. 934 935source "kernel/gcov/Kconfig" 936 937source "scripts/gcc-plugins/Kconfig" 938 939endmenu 940