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 KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config SET_FS 28 bool 29 30config HOTPLUG_SMT 31 bool 32 33config GENERIC_ENTRY 34 bool 35 36config KPROBES 37 bool "Kprobes" 38 depends on MODULES 39 depends on HAVE_KPROBES 40 select KALLSYMS 41 help 42 Kprobes allows you to trap at almost any kernel address and 43 execute a callback function. register_kprobe() establishes 44 a probepoint and specifies the callback. Kprobes is useful 45 for kernel debugging, non-intrusive instrumentation and testing. 46 If in doubt, say "N". 47 48config JUMP_LABEL 49 bool "Optimize very unlikely/likely branches" 50 depends on HAVE_ARCH_JUMP_LABEL 51 depends on CC_HAS_ASM_GOTO 52 help 53 This option enables a transparent branch optimization that 54 makes certain almost-always-true or almost-always-false branch 55 conditions even cheaper to execute within the kernel. 56 57 Certain performance-sensitive kernel code, such as trace points, 58 scheduler functionality, networking code and KVM have such 59 branches and include support for this optimization technique. 60 61 If it is detected that the compiler has support for "asm goto", 62 the kernel will compile such branches with just a nop 63 instruction. When the condition flag is toggled to true, the 64 nop will be converted to a jump instruction to execute the 65 conditional block of instructions. 66 67 This technique lowers overhead and stress on the branch prediction 68 of the processor and generally makes the kernel faster. The update 69 of the condition is slower, but those are always very rare. 70 71 ( On 32-bit x86, the necessary options added to the compiler 72 flags may increase the size of the kernel slightly. ) 73 74config STATIC_KEYS_SELFTEST 75 bool "Static key selftest" 76 depends on JUMP_LABEL 77 help 78 Boot time self-test of the branch patching code. 79 80config STATIC_CALL_SELFTEST 81 bool "Static call selftest" 82 depends on HAVE_STATIC_CALL 83 help 84 Boot time self-test of the call patching code. 85 86config OPTPROBES 87 def_bool y 88 depends on KPROBES && HAVE_OPTPROBES 89 select TASKS_RCU if PREEMPTION 90 91config KPROBES_ON_FTRACE 92 def_bool y 93 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 94 depends on DYNAMIC_FTRACE_WITH_REGS 95 help 96 If function tracer is enabled and the arch supports full 97 passing of pt_regs to function tracing, then kprobes can 98 optimize on top of function tracing. 99 100config UPROBES 101 def_bool n 102 depends on ARCH_SUPPORTS_UPROBES 103 help 104 Uprobes is the user-space counterpart to kprobes: they 105 enable instrumentation applications (such as 'perf probe') 106 to establish unintrusive probes in user-space binaries and 107 libraries, by executing handler functions when the probes 108 are hit by user-space applications. 109 110 ( These probes come in the form of single-byte breakpoints, 111 managed by the kernel and kept transparent to the probed 112 application. ) 113 114config HAVE_64BIT_ALIGNED_ACCESS 115 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 116 help 117 Some architectures require 64 bit accesses to be 64 bit 118 aligned, which also requires structs containing 64 bit values 119 to be 64 bit aligned too. This includes some 32 bit 120 architectures which can do 64 bit accesses, as well as 64 bit 121 architectures without unaligned access. 122 123 This symbol should be selected by an architecture if 64 bit 124 accesses are required to be 64 bit aligned in this way even 125 though it is not a 64 bit architecture. 126 127 See Documentation/unaligned-memory-access.txt for more 128 information on the topic of unaligned memory accesses. 129 130config HAVE_EFFICIENT_UNALIGNED_ACCESS 131 bool 132 help 133 Some architectures are unable to perform unaligned accesses 134 without the use of get_unaligned/put_unaligned. Others are 135 unable to perform such accesses efficiently (e.g. trap on 136 unaligned access and require fixing it up in the exception 137 handler.) 138 139 This symbol should be selected by an architecture if it can 140 perform unaligned accesses efficiently to allow different 141 code paths to be selected for these cases. Some network 142 drivers, for example, could opt to not fix up alignment 143 problems with received packets if doing so would not help 144 much. 145 146 See Documentation/core-api/unaligned-memory-access.rst for more 147 information on the topic of unaligned memory accesses. 148 149config ARCH_USE_BUILTIN_BSWAP 150 bool 151 help 152 Modern versions of GCC (since 4.4) have builtin functions 153 for handling byte-swapping. Using these, instead of the old 154 inline assembler that the architecture code provides in the 155 __arch_bswapXX() macros, allows the compiler to see what's 156 happening and offers more opportunity for optimisation. In 157 particular, the compiler will be able to combine the byteswap 158 with a nearby load or store and use load-and-swap or 159 store-and-swap instructions if the architecture has them. It 160 should almost *never* result in code which is worse than the 161 hand-coded assembler in <asm/swab.h>. But just in case it 162 does, the use of the builtins is optional. 163 164 Any architecture with load-and-swap or store-and-swap 165 instructions should set this. And it shouldn't hurt to set it 166 on architectures that don't have such instructions. 167 168config KRETPROBES 169 def_bool y 170 depends on KPROBES && HAVE_KRETPROBES 171 172config USER_RETURN_NOTIFIER 173 bool 174 depends on HAVE_USER_RETURN_NOTIFIER 175 help 176 Provide a kernel-internal notification when a cpu is about to 177 switch to user mode. 178 179config HAVE_IOREMAP_PROT 180 bool 181 182config HAVE_KPROBES 183 bool 184 185config HAVE_KRETPROBES 186 bool 187 188config HAVE_OPTPROBES 189 bool 190 191config HAVE_KPROBES_ON_FTRACE 192 bool 193 194config HAVE_FUNCTION_ERROR_INJECTION 195 bool 196 197config HAVE_NMI 198 bool 199 200# 201# An arch should select this if it provides all these things: 202# 203# task_pt_regs() in asm/processor.h or asm/ptrace.h 204# arch_has_single_step() if there is hardware single-step support 205# arch_has_block_step() if there is hardware block-step support 206# asm/syscall.h supplying asm-generic/syscall.h interface 207# linux/regset.h user_regset interfaces 208# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 209# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 210# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 211# signal delivery calls tracehook_signal_handler() 212# 213config HAVE_ARCH_TRACEHOOK 214 bool 215 216config HAVE_DMA_CONTIGUOUS 217 bool 218 219config GENERIC_SMP_IDLE_THREAD 220 bool 221 222config GENERIC_IDLE_POLL_SETUP 223 bool 224 225config ARCH_HAS_FORTIFY_SOURCE 226 bool 227 help 228 An architecture should select this when it can successfully 229 build and run with CONFIG_FORTIFY_SOURCE. 230 231# 232# Select if the arch provides a historic keepinit alias for the retain_initrd 233# command line option 234# 235config ARCH_HAS_KEEPINITRD 236 bool 237 238# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 239config ARCH_HAS_SET_MEMORY 240 bool 241 242# Select if arch has all set_direct_map_invalid/default() functions 243config ARCH_HAS_SET_DIRECT_MAP 244 bool 245 246# 247# Select if the architecture provides the arch_dma_set_uncached symbol to 248# either provide an uncached segment alias for a DMA allocation, or 249# to remap the page tables in place. 250# 251config ARCH_HAS_DMA_SET_UNCACHED 252 bool 253 254# 255# Select if the architectures provides the arch_dma_clear_uncached symbol 256# to undo an in-place page table remap for uncached access. 257# 258config ARCH_HAS_DMA_CLEAR_UNCACHED 259 bool 260 261# Select if arch init_task must go in the __init_task_data section 262config ARCH_TASK_STRUCT_ON_STACK 263 bool 264 265# Select if arch has its private alloc_task_struct() function 266config ARCH_TASK_STRUCT_ALLOCATOR 267 bool 268 269config HAVE_ARCH_THREAD_STRUCT_WHITELIST 270 bool 271 depends on !ARCH_TASK_STRUCT_ALLOCATOR 272 help 273 An architecture should select this to provide hardened usercopy 274 knowledge about what region of the thread_struct should be 275 whitelisted for copying to userspace. Normally this is only the 276 FPU registers. Specifically, arch_thread_struct_whitelist() 277 should be implemented. Without this, the entire thread_struct 278 field in task_struct will be left whitelisted. 279 280# Select if arch has its private alloc_thread_stack() function 281config ARCH_THREAD_STACK_ALLOCATOR 282 bool 283 284# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 285config ARCH_WANTS_DYNAMIC_TASK_STRUCT 286 bool 287 288config ARCH_32BIT_OFF_T 289 bool 290 depends on !64BIT 291 help 292 All new 32-bit architectures should have 64-bit off_t type on 293 userspace side which corresponds to the loff_t kernel type. This 294 is the requirement for modern ABIs. Some existing architectures 295 still support 32-bit off_t. This option is enabled for all such 296 architectures explicitly. 297 298config HAVE_ASM_MODVERSIONS 299 bool 300 help 301 This symbol should be selected by an architecture if it provides 302 <asm/asm-prototypes.h> to support the module versioning for symbols 303 exported from assembly code. 304 305config HAVE_REGS_AND_STACK_ACCESS_API 306 bool 307 help 308 This symbol should be selected by an architecture if it supports 309 the API needed to access registers and stack entries from pt_regs, 310 declared in asm/ptrace.h 311 For example the kprobes-based event tracer needs this API. 312 313config HAVE_RSEQ 314 bool 315 depends on HAVE_REGS_AND_STACK_ACCESS_API 316 help 317 This symbol should be selected by an architecture if it 318 supports an implementation of restartable sequences. 319 320config HAVE_FUNCTION_ARG_ACCESS_API 321 bool 322 help 323 This symbol should be selected by an architecture if it supports 324 the API needed to access function arguments from pt_regs, 325 declared in asm/ptrace.h 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 MMU_GATHER_TABLE_FREE 394 bool 395 396config MMU_GATHER_RCU_TABLE_FREE 397 bool 398 select MMU_GATHER_TABLE_FREE 399 400config MMU_GATHER_PAGE_SIZE 401 bool 402 403config MMU_GATHER_NO_RANGE 404 bool 405 406config MMU_GATHER_NO_GATHER 407 bool 408 depends on MMU_GATHER_TABLE_FREE 409 410config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 411 bool 412 help 413 Temporary select until all architectures can be converted to have 414 irqs disabled over activate_mm. Architectures that do IPI based TLB 415 shootdowns should enable this. 416 417config ARCH_HAVE_NMI_SAFE_CMPXCHG 418 bool 419 420config HAVE_ALIGNED_STRUCT_PAGE 421 bool 422 help 423 This makes sure that struct pages are double word aligned and that 424 e.g. the SLUB allocator can perform double word atomic operations 425 on a struct page for better performance. However selecting this 426 might increase the size of a struct page by a word. 427 428config HAVE_CMPXCHG_LOCAL 429 bool 430 431config HAVE_CMPXCHG_DOUBLE 432 bool 433 434config ARCH_WEAK_RELEASE_ACQUIRE 435 bool 436 437config ARCH_WANT_IPC_PARSE_VERSION 438 bool 439 440config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 441 bool 442 443config ARCH_WANT_OLD_COMPAT_IPC 444 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 445 bool 446 447config HAVE_ARCH_SECCOMP 448 bool 449 help 450 An arch should select this symbol to support seccomp mode 1 (the fixed 451 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 452 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 453 - __NR_seccomp_read_32 454 - __NR_seccomp_write_32 455 - __NR_seccomp_exit_32 456 - __NR_seccomp_sigreturn_32 457 458config HAVE_ARCH_SECCOMP_FILTER 459 bool 460 select HAVE_ARCH_SECCOMP 461 help 462 An arch should select this symbol if it provides all of these things: 463 - all the requirements for HAVE_ARCH_SECCOMP 464 - syscall_get_arch() 465 - syscall_get_arguments() 466 - syscall_rollback() 467 - syscall_set_return_value() 468 - SIGSYS siginfo_t support 469 - secure_computing is called from a ptrace_event()-safe context 470 - secure_computing return value is checked and a return value of -1 471 results in the system call being skipped immediately. 472 - seccomp syscall wired up 473 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 474 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 475 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 476 477config SECCOMP 478 prompt "Enable seccomp to safely execute untrusted bytecode" 479 def_bool y 480 depends on HAVE_ARCH_SECCOMP 481 help 482 This kernel feature is useful for number crunching applications 483 that may need to handle untrusted bytecode during their 484 execution. By using pipes or other transports made available 485 to the process as file descriptors supporting the read/write 486 syscalls, it's possible to isolate those applications in their 487 own address space using seccomp. Once seccomp is enabled via 488 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 489 disabled and the task is only allowed to execute a few safe 490 syscalls defined by each seccomp mode. 491 492 If unsure, say Y. 493 494config SECCOMP_FILTER 495 def_bool y 496 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 497 help 498 Enable tasks to build secure computing environments defined 499 in terms of Berkeley Packet Filter programs which implement 500 task-defined system call filtering polices. 501 502 See Documentation/userspace-api/seccomp_filter.rst for details. 503 504config SECCOMP_CACHE_DEBUG 505 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 506 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 507 depends on PROC_FS 508 help 509 This enables the /proc/pid/seccomp_cache interface to monitor 510 seccomp cache data. The file format is subject to change. Reading 511 the file requires CAP_SYS_ADMIN. 512 513 This option is for debugging only. Enabling presents the risk that 514 an adversary may be able to infer the seccomp filter logic. 515 516 If unsure, say N. 517 518config HAVE_ARCH_STACKLEAK 519 bool 520 help 521 An architecture should select this if it has the code which 522 fills the used part of the kernel stack with the STACKLEAK_POISON 523 value before returning from system calls. 524 525config HAVE_STACKPROTECTOR 526 bool 527 help 528 An arch should select this symbol if: 529 - it has implemented a stack canary (e.g. __stack_chk_guard) 530 531config STACKPROTECTOR 532 bool "Stack Protector buffer overflow detection" 533 depends on HAVE_STACKPROTECTOR 534 depends on $(cc-option,-fstack-protector) 535 default y 536 help 537 This option turns on the "stack-protector" GCC feature. This 538 feature puts, at the beginning of functions, a canary value on 539 the stack just before the return address, and validates 540 the value just before actually returning. Stack based buffer 541 overflows (that need to overwrite this return address) now also 542 overwrite the canary, which gets detected and the attack is then 543 neutralized via a kernel panic. 544 545 Functions will have the stack-protector canary logic added if they 546 have an 8-byte or larger character array on the stack. 547 548 This feature requires gcc version 4.2 or above, or a distribution 549 gcc with the feature backported ("-fstack-protector"). 550 551 On an x86 "defconfig" build, this feature adds canary checks to 552 about 3% of all kernel functions, which increases kernel code size 553 by about 0.3%. 554 555config STACKPROTECTOR_STRONG 556 bool "Strong Stack Protector" 557 depends on STACKPROTECTOR 558 depends on $(cc-option,-fstack-protector-strong) 559 default y 560 help 561 Functions will have the stack-protector canary logic added in any 562 of the following conditions: 563 564 - local variable's address used as part of the right hand side of an 565 assignment or function argument 566 - local variable is an array (or union containing an array), 567 regardless of array type or length 568 - uses register local variables 569 570 This feature requires gcc version 4.9 or above, or a distribution 571 gcc with the feature backported ("-fstack-protector-strong"). 572 573 On an x86 "defconfig" build, this feature adds canary checks to 574 about 20% of all kernel functions, which increases the kernel code 575 size by about 2%. 576 577config ARCH_SUPPORTS_SHADOW_CALL_STACK 578 bool 579 help 580 An architecture should select this if it supports Clang's Shadow 581 Call Stack and implements runtime support for shadow stack 582 switching. 583 584config SHADOW_CALL_STACK 585 bool "Clang Shadow Call Stack" 586 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 587 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 588 help 589 This option enables Clang's Shadow Call Stack, which uses a 590 shadow stack to protect function return addresses from being 591 overwritten by an attacker. More information can be found in 592 Clang's documentation: 593 594 https://clang.llvm.org/docs/ShadowCallStack.html 595 596 Note that security guarantees in the kernel differ from the 597 ones documented for user space. The kernel must store addresses 598 of shadow stacks in memory, which means an attacker capable of 599 reading and writing arbitrary memory may be able to locate them 600 and hijack control flow by modifying the stacks. 601 602config HAVE_ARCH_WITHIN_STACK_FRAMES 603 bool 604 help 605 An architecture should select this if it can walk the kernel stack 606 frames to determine if an object is part of either the arguments 607 or local variables (i.e. that it excludes saved return addresses, 608 and similar) by implementing an inline arch_within_stack_frames(), 609 which is used by CONFIG_HARDENED_USERCOPY. 610 611config HAVE_CONTEXT_TRACKING 612 bool 613 help 614 Provide kernel/user boundaries probes necessary for subsystems 615 that need it, such as userspace RCU extended quiescent state. 616 Syscalls need to be wrapped inside user_exit()-user_enter(), either 617 optimized behind static key or through the slow path using TIF_NOHZ 618 flag. Exceptions handlers must be wrapped as well. Irqs are already 619 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 620 handling on irq exit still need to be protected. 621 622config HAVE_CONTEXT_TRACKING_OFFSTACK 623 bool 624 help 625 Architecture neither relies on exception_enter()/exception_exit() 626 nor on schedule_user(). Also preempt_schedule_notrace() and 627 preempt_schedule_irq() can't be called in a preemptible section 628 while context tracking is CONTEXT_USER. This feature reflects a sane 629 entry implementation where the following requirements are met on 630 critical entry code, ie: before user_exit() or after user_enter(): 631 632 - Critical entry code isn't preemptible (or better yet: 633 not interruptible). 634 - No use of RCU read side critical sections, unless rcu_nmi_enter() 635 got called. 636 - No use of instrumentation, unless instrumentation_begin() got 637 called. 638 639config HAVE_TIF_NOHZ 640 bool 641 help 642 Arch relies on TIF_NOHZ and syscall slow path to implement context 643 tracking calls to user_enter()/user_exit(). 644 645config HAVE_VIRT_CPU_ACCOUNTING 646 bool 647 648config HAVE_VIRT_CPU_ACCOUNTING_IDLE 649 bool 650 help 651 Architecture has its own way to account idle CPU time and therefore 652 doesn't implement vtime_account_idle(). 653 654config ARCH_HAS_SCALED_CPUTIME 655 bool 656 657config HAVE_VIRT_CPU_ACCOUNTING_GEN 658 bool 659 default y if 64BIT 660 help 661 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 662 Before enabling this option, arch code must be audited 663 to ensure there are no races in concurrent read/write of 664 cputime_t. For example, reading/writing 64-bit cputime_t on 665 some 32-bit arches may require multiple accesses, so proper 666 locking is needed to protect against concurrent accesses. 667 668config HAVE_IRQ_TIME_ACCOUNTING 669 bool 670 help 671 Archs need to ensure they use a high enough resolution clock to 672 support irq time accounting and then call enable_sched_clock_irqtime(). 673 674config HAVE_MOVE_PUD 675 bool 676 help 677 Architectures that select this are able to move page tables at the 678 PUD level. If there are only 3 page table levels, the move effectively 679 happens at the PGD level. 680 681config HAVE_MOVE_PMD 682 bool 683 help 684 Archs that select this are able to move page tables at the PMD level. 685 686config HAVE_ARCH_TRANSPARENT_HUGEPAGE 687 bool 688 689config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 690 bool 691 692config HAVE_ARCH_HUGE_VMAP 693 bool 694 695config ARCH_WANT_HUGE_PMD_SHARE 696 bool 697 698config HAVE_ARCH_SOFT_DIRTY 699 bool 700 701config HAVE_MOD_ARCH_SPECIFIC 702 bool 703 help 704 The arch uses struct mod_arch_specific to store data. Many arches 705 just need a simple module loader without arch specific data - those 706 should not enable this. 707 708config MODULES_USE_ELF_RELA 709 bool 710 help 711 Modules only use ELF RELA relocations. Modules with ELF REL 712 relocations will give an error. 713 714config MODULES_USE_ELF_REL 715 bool 716 help 717 Modules only use ELF REL relocations. Modules with ELF RELA 718 relocations will give an error. 719 720config HAVE_IRQ_EXIT_ON_IRQ_STACK 721 bool 722 help 723 Architecture doesn't only execute the irq handler on the irq stack 724 but also irq_exit(). This way we can process softirqs on this irq 725 stack instead of switching to a new one when we call __do_softirq() 726 in the end of an hardirq. 727 This spares a stack switch and improves cache usage on softirq 728 processing. 729 730config PGTABLE_LEVELS 731 int 732 default 2 733 734config ARCH_HAS_ELF_RANDOMIZE 735 bool 736 help 737 An architecture supports choosing randomized locations for 738 stack, mmap, brk, and ET_DYN. Defined functions: 739 - arch_mmap_rnd() 740 - arch_randomize_brk() 741 742config HAVE_ARCH_MMAP_RND_BITS 743 bool 744 help 745 An arch should select this symbol if it supports setting a variable 746 number of bits for use in establishing the base address for mmap 747 allocations, has MMU enabled and provides values for both: 748 - ARCH_MMAP_RND_BITS_MIN 749 - ARCH_MMAP_RND_BITS_MAX 750 751config HAVE_EXIT_THREAD 752 bool 753 help 754 An architecture implements exit_thread. 755 756config ARCH_MMAP_RND_BITS_MIN 757 int 758 759config ARCH_MMAP_RND_BITS_MAX 760 int 761 762config ARCH_MMAP_RND_BITS_DEFAULT 763 int 764 765config ARCH_MMAP_RND_BITS 766 int "Number of bits to use for ASLR of mmap base address" if EXPERT 767 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 768 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 769 default ARCH_MMAP_RND_BITS_MIN 770 depends on HAVE_ARCH_MMAP_RND_BITS 771 help 772 This value can be used to select the number of bits to use to 773 determine the random offset to the base address of vma regions 774 resulting from mmap allocations. This value will be bounded 775 by the architecture's minimum and maximum supported values. 776 777 This value can be changed after boot using the 778 /proc/sys/vm/mmap_rnd_bits tunable 779 780config HAVE_ARCH_MMAP_RND_COMPAT_BITS 781 bool 782 help 783 An arch should select this symbol if it supports running applications 784 in compatibility mode, supports setting a variable number of bits for 785 use in establishing the base address for mmap allocations, has MMU 786 enabled and provides values for both: 787 - ARCH_MMAP_RND_COMPAT_BITS_MIN 788 - ARCH_MMAP_RND_COMPAT_BITS_MAX 789 790config ARCH_MMAP_RND_COMPAT_BITS_MIN 791 int 792 793config ARCH_MMAP_RND_COMPAT_BITS_MAX 794 int 795 796config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 797 int 798 799config ARCH_MMAP_RND_COMPAT_BITS 800 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 801 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 802 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 803 default ARCH_MMAP_RND_COMPAT_BITS_MIN 804 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 805 help 806 This value can be used to select the number of bits to use to 807 determine the random offset to the base address of vma regions 808 resulting from mmap allocations for compatible applications This 809 value will be bounded by the architecture's minimum and maximum 810 supported values. 811 812 This value can be changed after boot using the 813 /proc/sys/vm/mmap_rnd_compat_bits tunable 814 815config HAVE_ARCH_COMPAT_MMAP_BASES 816 bool 817 help 818 This allows 64bit applications to invoke 32-bit mmap() syscall 819 and vice-versa 32-bit applications to call 64-bit mmap(). 820 Required for applications doing different bitness syscalls. 821 822# This allows to use a set of generic functions to determine mmap base 823# address by giving priority to top-down scheme only if the process 824# is not in legacy mode (compat task, unlimited stack size or 825# sysctl_legacy_va_layout). 826# Architecture that selects this option can provide its own version of: 827# - STACK_RND_MASK 828config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 829 bool 830 depends on MMU 831 select ARCH_HAS_ELF_RANDOMIZE 832 833config HAVE_STACK_VALIDATION 834 bool 835 help 836 Architecture supports the 'objtool check' host tool command, which 837 performs compile-time stack metadata validation. 838 839config HAVE_RELIABLE_STACKTRACE 840 bool 841 help 842 Architecture has either save_stack_trace_tsk_reliable() or 843 arch_stack_walk_reliable() function which only returns a stack trace 844 if it can guarantee the trace is reliable. 845 846config HAVE_ARCH_HASH 847 bool 848 default n 849 help 850 If this is set, the architecture provides an <asm/hash.h> 851 file which provides platform-specific implementations of some 852 functions in <linux/hash.h> or fs/namei.c. 853 854config HAVE_ARCH_NVRAM_OPS 855 bool 856 857config ISA_BUS_API 858 def_bool ISA 859 860# 861# ABI hall of shame 862# 863config CLONE_BACKWARDS 864 bool 865 help 866 Architecture has tls passed as the 4th argument of clone(2), 867 not the 5th one. 868 869config CLONE_BACKWARDS2 870 bool 871 help 872 Architecture has the first two arguments of clone(2) swapped. 873 874config CLONE_BACKWARDS3 875 bool 876 help 877 Architecture has tls passed as the 3rd argument of clone(2), 878 not the 5th one. 879 880config ODD_RT_SIGACTION 881 bool 882 help 883 Architecture has unusual rt_sigaction(2) arguments 884 885config OLD_SIGSUSPEND 886 bool 887 help 888 Architecture has old sigsuspend(2) syscall, of one-argument variety 889 890config OLD_SIGSUSPEND3 891 bool 892 help 893 Even weirder antique ABI - three-argument sigsuspend(2) 894 895config OLD_SIGACTION 896 bool 897 help 898 Architecture has old sigaction(2) syscall. Nope, not the same 899 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 900 but fairly different variant of sigaction(2), thanks to OSF/1 901 compatibility... 902 903config COMPAT_OLD_SIGACTION 904 bool 905 906config COMPAT_32BIT_TIME 907 bool "Provide system calls for 32-bit time_t" 908 default !64BIT || COMPAT 909 help 910 This enables 32 bit time_t support in addition to 64 bit time_t support. 911 This is relevant on all 32-bit architectures, and 64-bit architectures 912 as part of compat syscall handling. 913 914config ARCH_NO_PREEMPT 915 bool 916 917config ARCH_SUPPORTS_RT 918 bool 919 920config CPU_NO_EFFICIENT_FFS 921 def_bool n 922 923config HAVE_ARCH_VMAP_STACK 924 def_bool n 925 help 926 An arch should select this symbol if it can support kernel stacks 927 in vmalloc space. This means: 928 929 - vmalloc space must be large enough to hold many kernel stacks. 930 This may rule out many 32-bit architectures. 931 932 - Stacks in vmalloc space need to work reliably. For example, if 933 vmap page tables are created on demand, either this mechanism 934 needs to work while the stack points to a virtual address with 935 unpopulated page tables or arch code (switch_to() and switch_mm(), 936 most likely) needs to ensure that the stack's page table entries 937 are populated before running on a possibly unpopulated stack. 938 939 - If the stack overflows into a guard page, something reasonable 940 should happen. The definition of "reasonable" is flexible, but 941 instantly rebooting without logging anything would be unfriendly. 942 943config VMAP_STACK 944 default y 945 bool "Use a virtually-mapped stack" 946 depends on HAVE_ARCH_VMAP_STACK 947 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 948 help 949 Enable this if you want the use virtually-mapped kernel stacks 950 with guard pages. This causes kernel stack overflows to be 951 caught immediately rather than causing difficult-to-diagnose 952 corruption. 953 954 To use this with software KASAN modes, the architecture must support 955 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 956 must be enabled. 957 958config ARCH_OPTIONAL_KERNEL_RWX 959 def_bool n 960 961config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 962 def_bool n 963 964config ARCH_HAS_STRICT_KERNEL_RWX 965 def_bool n 966 967config STRICT_KERNEL_RWX 968 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 969 depends on ARCH_HAS_STRICT_KERNEL_RWX 970 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 971 help 972 If this is set, kernel text and rodata memory will be made read-only, 973 and non-text memory will be made non-executable. This provides 974 protection against certain security exploits (e.g. executing the heap 975 or modifying text) 976 977 These features are considered standard security practice these days. 978 You should say Y here in almost all cases. 979 980config ARCH_HAS_STRICT_MODULE_RWX 981 def_bool n 982 983config STRICT_MODULE_RWX 984 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 985 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 986 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 987 help 988 If this is set, module text and rodata memory will be made read-only, 989 and non-text memory will be made non-executable. This provides 990 protection against certain security exploits (e.g. writing to text) 991 992# select if the architecture provides an asm/dma-direct.h header 993config ARCH_HAS_PHYS_TO_DMA 994 bool 995 996config HAVE_ARCH_COMPILER_H 997 bool 998 help 999 An architecture can select this if it provides an 1000 asm/compiler.h header that should be included after 1001 linux/compiler-*.h in order to override macro definitions that those 1002 headers generally provide. 1003 1004config HAVE_ARCH_PREL32_RELOCATIONS 1005 bool 1006 help 1007 May be selected by an architecture if it supports place-relative 1008 32-bit relocations, both in the toolchain and in the module loader, 1009 in which case relative references can be used in special sections 1010 for PCI fixup, initcalls etc which are only half the size on 64 bit 1011 architectures, and don't require runtime relocation on relocatable 1012 kernels. 1013 1014config ARCH_USE_MEMREMAP_PROT 1015 bool 1016 1017config LOCK_EVENT_COUNTS 1018 bool "Locking event counts collection" 1019 depends on DEBUG_FS 1020 help 1021 Enable light-weight counting of various locking related events 1022 in the system with minimal performance impact. This reduces 1023 the chance of application behavior change because of timing 1024 differences. The counts are reported via debugfs. 1025 1026# Select if the architecture has support for applying RELR relocations. 1027config ARCH_HAS_RELR 1028 bool 1029 1030config RELR 1031 bool "Use RELR relocation packing" 1032 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1033 default y 1034 help 1035 Store the kernel's dynamic relocations in the RELR relocation packing 1036 format. Requires a compatible linker (LLD supports this feature), as 1037 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1038 are compatible). 1039 1040config ARCH_HAS_MEM_ENCRYPT 1041 bool 1042 1043config HAVE_SPARSE_SYSCALL_NR 1044 bool 1045 help 1046 An architecture should select this if its syscall numbering is sparse 1047 to save space. For example, MIPS architecture has a syscall array with 1048 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1049 related optimizations for a given architecture. 1050 1051config ARCH_HAS_VDSO_DATA 1052 bool 1053 1054config HAVE_STATIC_CALL 1055 bool 1056 1057config HAVE_STATIC_CALL_INLINE 1058 bool 1059 depends on HAVE_STATIC_CALL 1060 1061config HAVE_PREEMPT_DYNAMIC 1062 bool 1063 depends on HAVE_STATIC_CALL 1064 depends on GENERIC_ENTRY 1065 help 1066 Select this if the architecture support boot time preempt setting 1067 on top of static calls. It is strongly advised to support inline 1068 static call to avoid any overhead. 1069 1070config ARCH_WANT_LD_ORPHAN_WARN 1071 bool 1072 help 1073 An arch should select this symbol once all linker sections are explicitly 1074 included, size-asserted, or discarded in the linker scripts. This is 1075 important because we never want expected sections to be placed heuristically 1076 by the linker, since the locations of such sections can change between linker 1077 versions. 1078 1079config HAVE_ARCH_PFN_VALID 1080 bool 1081 1082config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1083 bool 1084 1085config ARCH_SPLIT_ARG64 1086 bool 1087 help 1088 If a 32-bit architecture requires 64-bit arguments to be split into 1089 pairs of 32-bit arguments, select this option. 1090 1091config ARCH_HAS_ELFCORE_COMPAT 1092 bool 1093 1094source "kernel/gcov/Kconfig" 1095 1096source "scripts/gcc-plugins/Kconfig" 1097 1098endmenu 1099