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 12config ARCH_CONFIGURES_CPU_MITIGATIONS 13 bool 14 15if !ARCH_CONFIGURES_CPU_MITIGATIONS 16config CPU_MITIGATIONS 17 def_bool y 18endif 19 20# 21# Selected by architectures that need custom DMA operations for e.g. legacy 22# IOMMUs not handled by dma-iommu. Drivers must never select this symbol. 23# 24config ARCH_HAS_DMA_OPS 25 depends on HAS_DMA 26 select DMA_OPS_HELPERS 27 bool 28 29menu "General architecture-dependent options" 30 31config ARCH_HAS_SUBPAGE_FAULTS 32 bool 33 help 34 Select if the architecture can check permissions at sub-page 35 granularity (e.g. arm64 MTE). The probe_user_*() functions 36 must be implemented. 37 38config HOTPLUG_SMT 39 bool 40 41config SMT_NUM_THREADS_DYNAMIC 42 bool 43 44config ARCH_SUPPORTS_SCHED_SMT 45 bool 46 47config ARCH_SUPPORTS_SCHED_CLUSTER 48 bool 49 50config ARCH_SUPPORTS_SCHED_MC 51 bool 52 53config SCHED_SMT 54 bool "SMT (Hyperthreading) scheduler support" 55 depends on ARCH_SUPPORTS_SCHED_SMT 56 default y 57 help 58 Improves the CPU scheduler's decision making when dealing with 59 MultiThreading at a cost of slightly increased overhead in some 60 places. If unsure say N here. 61 62config SCHED_CLUSTER 63 bool "Cluster scheduler support" 64 depends on ARCH_SUPPORTS_SCHED_CLUSTER 65 default y 66 help 67 Cluster scheduler support improves the CPU scheduler's decision 68 making when dealing with machines that have clusters of CPUs. 69 Cluster usually means a couple of CPUs which are placed closely 70 by sharing mid-level caches, last-level cache tags or internal 71 busses. 72 73config SCHED_MC 74 bool "Multi-Core Cache (MC) scheduler support" 75 depends on ARCH_SUPPORTS_SCHED_MC 76 default y 77 help 78 Multi-core scheduler support improves the CPU scheduler's decision 79 making when dealing with multi-core CPU chips at a cost of slightly 80 increased overhead in some places. If unsure say N here. 81 82# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 83config HOTPLUG_CORE_SYNC 84 bool 85 86# Basic CPU dead synchronization selected by architecture 87config HOTPLUG_CORE_SYNC_DEAD 88 bool 89 select HOTPLUG_CORE_SYNC 90 91# Full CPU synchronization with alive state selected by architecture 92config HOTPLUG_CORE_SYNC_FULL 93 bool 94 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 95 select HOTPLUG_CORE_SYNC 96 97config HOTPLUG_SPLIT_STARTUP 98 bool 99 select HOTPLUG_CORE_SYNC_FULL 100 101config HOTPLUG_PARALLEL 102 bool 103 select HOTPLUG_SPLIT_STARTUP 104 105config GENERIC_IRQ_ENTRY 106 bool 107 108config GENERIC_SYSCALL 109 bool 110 depends on GENERIC_IRQ_ENTRY 111 112config GENERIC_ENTRY 113 bool 114 select GENERIC_IRQ_ENTRY 115 select GENERIC_SYSCALL 116 117config KPROBES 118 bool "Kprobes" 119 depends on HAVE_KPROBES 120 select KALLSYMS 121 select EXECMEM 122 select NEED_TASKS_RCU 123 help 124 Kprobes allows you to trap at almost any kernel address and 125 execute a callback function. register_kprobe() establishes 126 a probepoint and specifies the callback. Kprobes is useful 127 for kernel debugging, non-intrusive instrumentation and testing. 128 If in doubt, say "N". 129 130config JUMP_LABEL 131 bool "Optimize very unlikely/likely branches" 132 depends on HAVE_ARCH_JUMP_LABEL 133 select OBJTOOL if HAVE_JUMP_LABEL_HACK 134 help 135 This option enables a transparent branch optimization that 136 makes certain almost-always-true or almost-always-false branch 137 conditions even cheaper to execute within the kernel. 138 139 Certain performance-sensitive kernel code, such as trace points, 140 scheduler functionality, networking code and KVM have such 141 branches and include support for this optimization technique. 142 143 If it is detected that the compiler has support for "asm goto", 144 the kernel will compile such branches with just a nop 145 instruction. When the condition flag is toggled to true, the 146 nop will be converted to a jump instruction to execute the 147 conditional block of instructions. 148 149 This technique lowers overhead and stress on the branch prediction 150 of the processor and generally makes the kernel faster. The update 151 of the condition is slower, but those are always very rare. 152 153 ( On 32-bit x86, the necessary options added to the compiler 154 flags may increase the size of the kernel slightly. ) 155 156config STATIC_KEYS_SELFTEST 157 bool "Static key selftest" 158 depends on JUMP_LABEL 159 help 160 Boot time self-test of the branch patching code. 161 162config STATIC_CALL_SELFTEST 163 bool "Static call selftest" 164 depends on HAVE_STATIC_CALL 165 help 166 Boot time self-test of the call patching code. 167 168config OPTPROBES 169 def_bool y 170 depends on KPROBES && HAVE_OPTPROBES 171 select NEED_TASKS_RCU 172 173config KPROBES_ON_FTRACE 174 def_bool y 175 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 176 depends on DYNAMIC_FTRACE_WITH_REGS 177 help 178 If function tracer is enabled and the arch supports full 179 passing of pt_regs to function tracing, then kprobes can 180 optimize on top of function tracing. 181 182config UPROBES 183 def_bool n 184 depends on ARCH_SUPPORTS_UPROBES 185 select TASKS_TRACE_RCU 186 help 187 Uprobes is the user-space counterpart to kprobes: they 188 enable instrumentation applications (such as 'perf probe') 189 to establish unintrusive probes in user-space binaries and 190 libraries, by executing handler functions when the probes 191 are hit by user-space applications. 192 193 ( These probes come in the form of single-byte breakpoints, 194 managed by the kernel and kept transparent to the probed 195 application. ) 196 197config HAVE_64BIT_ALIGNED_ACCESS 198 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 199 help 200 Some architectures require 64 bit accesses to be 64 bit 201 aligned, which also requires structs containing 64 bit values 202 to be 64 bit aligned too. This includes some 32 bit 203 architectures which can do 64 bit accesses, as well as 64 bit 204 architectures without unaligned access. 205 206 This symbol should be selected by an architecture if 64 bit 207 accesses are required to be 64 bit aligned in this way even 208 though it is not a 64 bit architecture. 209 210 See Documentation/core-api/unaligned-memory-access.rst for 211 more information on the topic of unaligned memory accesses. 212 213config HAVE_EFFICIENT_UNALIGNED_ACCESS 214 bool 215 help 216 Some architectures are unable to perform unaligned accesses 217 without the use of get_unaligned/put_unaligned. Others are 218 unable to perform such accesses efficiently (e.g. trap on 219 unaligned access and require fixing it up in the exception 220 handler.) 221 222 This symbol should be selected by an architecture if it can 223 perform unaligned accesses efficiently to allow different 224 code paths to be selected for these cases. Some network 225 drivers, for example, could opt to not fix up alignment 226 problems with received packets if doing so would not help 227 much. 228 229 See Documentation/core-api/unaligned-memory-access.rst for more 230 information on the topic of unaligned memory accesses. 231 232config ARCH_USE_BUILTIN_BSWAP 233 bool 234 help 235 Modern versions of GCC (since 4.4) have builtin functions 236 for handling byte-swapping. Using these, instead of the old 237 inline assembler that the architecture code provides in the 238 __arch_bswapXX() macros, allows the compiler to see what's 239 happening and offers more opportunity for optimisation. In 240 particular, the compiler will be able to combine the byteswap 241 with a nearby load or store and use load-and-swap or 242 store-and-swap instructions if the architecture has them. It 243 should almost *never* result in code which is worse than the 244 hand-coded assembler in <asm/swab.h>. But just in case it 245 does, the use of the builtins is optional. 246 247 Any architecture with load-and-swap or store-and-swap 248 instructions should set this. And it shouldn't hurt to set it 249 on architectures that don't have such instructions. 250 251config KRETPROBES 252 def_bool y 253 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 254 255config KRETPROBE_ON_RETHOOK 256 def_bool y 257 depends on HAVE_RETHOOK 258 depends on KRETPROBES 259 select RETHOOK 260 261config USER_RETURN_NOTIFIER 262 bool 263 depends on HAVE_USER_RETURN_NOTIFIER 264 help 265 Provide a kernel-internal notification when a cpu is about to 266 switch to user mode. 267 268config HAVE_IOREMAP_PROT 269 bool 270 271config HAVE_KPROBES 272 bool 273 274config HAVE_KRETPROBES 275 bool 276 277config HAVE_OPTPROBES 278 bool 279 280config HAVE_KPROBES_ON_FTRACE 281 bool 282 283config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 284 bool 285 help 286 Since kretprobes modifies return address on the stack, the 287 stacktrace may see the kretprobe trampoline address instead 288 of correct one. If the architecture stacktrace code and 289 unwinder can adjust such entries, select this configuration. 290 291config HAVE_FUNCTION_ERROR_INJECTION 292 bool 293 294config HAVE_NMI 295 bool 296 297config HAVE_FUNCTION_DESCRIPTORS 298 bool 299 300config TRACE_IRQFLAGS_SUPPORT 301 bool 302 303config TRACE_IRQFLAGS_NMI_SUPPORT 304 bool 305 306# 307# An arch should select this if it provides all these things: 308# 309# task_pt_regs() in asm/processor.h or asm/ptrace.h 310# arch_has_single_step() if there is hardware single-step support 311# arch_has_block_step() if there is hardware block-step support 312# asm/syscall.h supplying asm-generic/syscall.h interface 313# linux/regset.h user_regset interfaces 314# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 315# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 316# TIF_NOTIFY_RESUME calls resume_user_mode_work() 317# 318config HAVE_ARCH_TRACEHOOK 319 bool 320 321config HAVE_DMA_CONTIGUOUS 322 bool 323 324config GENERIC_SMP_IDLE_THREAD 325 bool 326 327config GENERIC_IDLE_POLL_SETUP 328 bool 329 330config ARCH_HAS_FORTIFY_SOURCE 331 bool 332 help 333 An architecture should select this when it can successfully 334 build and run with CONFIG_FORTIFY_SOURCE. 335 336# 337# Select if the arch provides a historic keepinit alias for the retain_initrd 338# command line option 339# 340config ARCH_HAS_KEEPINITRD 341 bool 342 343# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 344config ARCH_HAS_SET_MEMORY 345 bool 346 347# Select if arch has all set_direct_map_invalid/default() functions 348config ARCH_HAS_SET_DIRECT_MAP 349 bool 350 351# 352# Select if the architecture provides the arch_dma_set_uncached symbol to 353# either provide an uncached segment alias for a DMA allocation, or 354# to remap the page tables in place. 355# 356config ARCH_HAS_DMA_SET_UNCACHED 357 bool 358 359# 360# Select if the architectures provides the arch_dma_clear_uncached symbol 361# to undo an in-place page table remap for uncached access. 362# 363config ARCH_HAS_DMA_CLEAR_UNCACHED 364 bool 365 366config ARCH_HAS_CPU_FINALIZE_INIT 367 bool 368 369# The architecture has a per-task state that includes the mm's PASID 370config ARCH_HAS_CPU_PASID 371 bool 372 select IOMMU_MM_DATA 373 374config HAVE_ARCH_THREAD_STRUCT_WHITELIST 375 bool 376 help 377 An architecture should select this to provide hardened usercopy 378 knowledge about what region of the thread_struct should be 379 whitelisted for copying to userspace. Normally this is only the 380 FPU registers. Specifically, arch_thread_struct_whitelist() 381 should be implemented. Without this, the entire thread_struct 382 field in task_struct will be left whitelisted. 383 384# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 385config ARCH_WANTS_DYNAMIC_TASK_STRUCT 386 bool 387 388config ARCH_WANTS_NO_INSTR 389 bool 390 help 391 An architecture should select this if the noinstr macro is being used on 392 functions to denote that the toolchain should avoid instrumenting such 393 functions and is required for correctness. 394 395config ARCH_32BIT_OFF_T 396 bool 397 depends on !64BIT 398 help 399 All new 32-bit architectures should have 64-bit off_t type on 400 userspace side which corresponds to the loff_t kernel type. This 401 is the requirement for modern ABIs. Some existing architectures 402 still support 32-bit off_t. This option is enabled for all such 403 architectures explicitly. 404 405# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 406config ARCH_32BIT_USTAT_F_TINODE 407 bool 408 409config HAVE_ASM_MODVERSIONS 410 bool 411 help 412 This symbol should be selected by an architecture if it provides 413 <asm/asm-prototypes.h> to support the module versioning for symbols 414 exported from assembly code. 415 416config HAVE_REGS_AND_STACK_ACCESS_API 417 bool 418 help 419 This symbol should be selected by an architecture if it supports 420 the API needed to access registers and stack entries from pt_regs, 421 declared in asm/ptrace.h 422 For example the kprobes-based event tracer needs this API. 423 424config HAVE_RSEQ 425 bool 426 depends on HAVE_REGS_AND_STACK_ACCESS_API 427 help 428 This symbol should be selected by an architecture if it 429 supports an implementation of restartable sequences. 430 431config HAVE_RUST 432 bool 433 help 434 This symbol should be selected by an architecture if it 435 supports Rust. 436 437config HAVE_FUNCTION_ARG_ACCESS_API 438 bool 439 help 440 This symbol should be selected by an architecture if it supports 441 the API needed to access function arguments from pt_regs, 442 declared in asm/ptrace.h 443 444config HAVE_HW_BREAKPOINT 445 bool 446 depends on PERF_EVENTS 447 448config HAVE_MIXED_BREAKPOINTS_REGS 449 bool 450 depends on HAVE_HW_BREAKPOINT 451 help 452 Depending on the arch implementation of hardware breakpoints, 453 some of them have separate registers for data and instruction 454 breakpoints addresses, others have mixed registers to store 455 them but define the access type in a control register. 456 Select this option if your arch implements breakpoints under the 457 latter fashion. 458 459config HAVE_USER_RETURN_NOTIFIER 460 bool 461 462config HAVE_PERF_EVENTS_NMI 463 bool 464 help 465 System hardware can generate an NMI using the perf event 466 subsystem. Also has support for calculating CPU cycle events 467 to determine how many clock cycles in a given period. 468 469config HAVE_HARDLOCKUP_DETECTOR_PERF 470 bool 471 depends on HAVE_PERF_EVENTS_NMI 472 help 473 The arch chooses to use the generic perf-NMI-based hardlockup 474 detector. Must define HAVE_PERF_EVENTS_NMI. 475 476config HAVE_HARDLOCKUP_DETECTOR_ARCH 477 bool 478 help 479 The arch provides its own hardlockup detector implementation instead 480 of the generic ones. 481 482 It uses the same command line parameters, and sysctl interface, 483 as the generic hardlockup detectors. 484 485config UNWIND_USER 486 bool 487 488config HAVE_UNWIND_USER_FP 489 bool 490 select UNWIND_USER 491 492config HAVE_PERF_REGS 493 bool 494 help 495 Support selective register dumps for perf events. This includes 496 bit-mapping of each registers and a unique architecture id. 497 498config HAVE_PERF_USER_STACK_DUMP 499 bool 500 help 501 Support user stack dumps for perf event samples. This needs 502 access to the user stack pointer which is not unified across 503 architectures. 504 505config HAVE_ARCH_JUMP_LABEL 506 bool 507 508config HAVE_ARCH_JUMP_LABEL_RELATIVE 509 bool 510 511config MMU_GATHER_TABLE_FREE 512 bool 513 514config MMU_GATHER_RCU_TABLE_FREE 515 bool 516 select MMU_GATHER_TABLE_FREE 517 518config MMU_GATHER_PAGE_SIZE 519 bool 520 521config MMU_GATHER_NO_RANGE 522 bool 523 select MMU_GATHER_MERGE_VMAS 524 525config MMU_GATHER_NO_FLUSH_CACHE 526 bool 527 528config MMU_GATHER_MERGE_VMAS 529 bool 530 531config MMU_GATHER_NO_GATHER 532 bool 533 depends on MMU_GATHER_TABLE_FREE 534 535config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 536 bool 537 help 538 Temporary select until all architectures can be converted to have 539 irqs disabled over activate_mm. Architectures that do IPI based TLB 540 shootdowns should enable this. 541 542# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 543# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 544# to/from kernel threads when the same mm is running on a lot of CPUs (a large 545# multi-threaded application), by reducing contention on the mm refcount. 546# 547# This can be disabled if the architecture ensures no CPUs are using an mm as a 548# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 549# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 550# final exit(2) TLB flush, for example. 551# 552# To implement this, an arch *must*: 553# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 554# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 555# converted already). 556config MMU_LAZY_TLB_REFCOUNT 557 def_bool y 558 depends on !MMU_LAZY_TLB_SHOOTDOWN 559 560# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 561# mm as a lazy tlb beyond its last reference count, by shooting down these 562# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 563# be using the mm as a lazy tlb, so that they may switch themselves to using 564# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 565# may be using mm as a lazy tlb mm. 566# 567# To implement this, an arch *must*: 568# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 569# at least all possible CPUs in which the mm is lazy. 570# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 571config MMU_LAZY_TLB_SHOOTDOWN 572 bool 573 574config ARCH_HAVE_NMI_SAFE_CMPXCHG 575 bool 576 577config ARCH_HAVE_EXTRA_ELF_NOTES 578 bool 579 help 580 An architecture should select this in order to enable adding an 581 arch-specific ELF note section to core files. It must provide two 582 functions: elf_coredump_extra_notes_size() and 583 elf_coredump_extra_notes_write() which are invoked by the ELF core 584 dumper. 585 586config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 587 bool 588 589config HAVE_ALIGNED_STRUCT_PAGE 590 bool 591 help 592 This makes sure that struct pages are double word aligned and that 593 e.g. the SLUB allocator can perform double word atomic operations 594 on a struct page for better performance. However selecting this 595 might increase the size of a struct page by a word. 596 597config HAVE_CMPXCHG_LOCAL 598 bool 599 600config HAVE_CMPXCHG_DOUBLE 601 bool 602 603config ARCH_WEAK_RELEASE_ACQUIRE 604 bool 605 606config ARCH_WANT_IPC_PARSE_VERSION 607 bool 608 609config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 610 bool 611 612config ARCH_WANT_OLD_COMPAT_IPC 613 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 614 bool 615 616config HAVE_ARCH_SECCOMP 617 bool 618 help 619 An arch should select this symbol to support seccomp mode 1 (the fixed 620 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 621 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 622 - __NR_seccomp_read_32 623 - __NR_seccomp_write_32 624 - __NR_seccomp_exit_32 625 - __NR_seccomp_sigreturn_32 626 627config HAVE_ARCH_SECCOMP_FILTER 628 bool 629 select HAVE_ARCH_SECCOMP 630 help 631 An arch should select this symbol if it provides all of these things: 632 - all the requirements for HAVE_ARCH_SECCOMP 633 - syscall_get_arch() 634 - syscall_get_arguments() 635 - syscall_rollback() 636 - syscall_set_return_value() 637 - SIGSYS siginfo_t support 638 - secure_computing is called from a ptrace_event()-safe context 639 - secure_computing return value is checked and a return value of -1 640 results in the system call being skipped immediately. 641 - seccomp syscall wired up 642 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 643 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 644 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 645 646config SECCOMP 647 prompt "Enable seccomp to safely execute untrusted bytecode" 648 def_bool y 649 depends on HAVE_ARCH_SECCOMP 650 help 651 This kernel feature is useful for number crunching applications 652 that may need to handle untrusted bytecode during their 653 execution. By using pipes or other transports made available 654 to the process as file descriptors supporting the read/write 655 syscalls, it's possible to isolate those applications in their 656 own address space using seccomp. Once seccomp is enabled via 657 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 658 disabled and the task is only allowed to execute a few safe 659 syscalls defined by each seccomp mode. 660 661 If unsure, say Y. 662 663config SECCOMP_FILTER 664 def_bool y 665 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 666 help 667 Enable tasks to build secure computing environments defined 668 in terms of Berkeley Packet Filter programs which implement 669 task-defined system call filtering polices. 670 671 See Documentation/userspace-api/seccomp_filter.rst for details. 672 673config SECCOMP_CACHE_DEBUG 674 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 675 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 676 depends on PROC_FS 677 help 678 This enables the /proc/pid/seccomp_cache interface to monitor 679 seccomp cache data. The file format is subject to change. Reading 680 the file requires CAP_SYS_ADMIN. 681 682 This option is for debugging only. Enabling presents the risk that 683 an adversary may be able to infer the seccomp filter logic. 684 685 If unsure, say N. 686 687config HAVE_ARCH_KSTACK_ERASE 688 bool 689 help 690 An architecture should select this if it has the code which 691 fills the used part of the kernel stack with the KSTACK_ERASE_POISON 692 value before returning from system calls. 693 694config HAVE_STACKPROTECTOR 695 bool 696 help 697 An arch should select this symbol if: 698 - it has implemented a stack canary (e.g. __stack_chk_guard) 699 700config STACKPROTECTOR 701 bool "Stack Protector buffer overflow detection" 702 depends on HAVE_STACKPROTECTOR 703 depends on $(cc-option,-fstack-protector) 704 default y 705 help 706 This option turns on the "stack-protector" GCC feature. This 707 feature puts, at the beginning of functions, a canary value on 708 the stack just before the return address, and validates 709 the value just before actually returning. Stack based buffer 710 overflows (that need to overwrite this return address) now also 711 overwrite the canary, which gets detected and the attack is then 712 neutralized via a kernel panic. 713 714 Functions will have the stack-protector canary logic added if they 715 have an 8-byte or larger character array on the stack. 716 717 This feature requires gcc version 4.2 or above, or a distribution 718 gcc with the feature backported ("-fstack-protector"). 719 720 On an x86 "defconfig" build, this feature adds canary checks to 721 about 3% of all kernel functions, which increases kernel code size 722 by about 0.3%. 723 724config STACKPROTECTOR_STRONG 725 bool "Strong Stack Protector" 726 depends on STACKPROTECTOR 727 depends on $(cc-option,-fstack-protector-strong) 728 default y 729 help 730 Functions will have the stack-protector canary logic added in any 731 of the following conditions: 732 733 - local variable's address used as part of the right hand side of an 734 assignment or function argument 735 - local variable is an array (or union containing an array), 736 regardless of array type or length 737 - uses register local variables 738 739 This feature requires gcc version 4.9 or above, or a distribution 740 gcc with the feature backported ("-fstack-protector-strong"). 741 742 On an x86 "defconfig" build, this feature adds canary checks to 743 about 20% of all kernel functions, which increases the kernel code 744 size by about 2%. 745 746config ARCH_SUPPORTS_SHADOW_CALL_STACK 747 bool 748 help 749 An architecture should select this if it supports the compiler's 750 Shadow Call Stack and implements runtime support for shadow stack 751 switching. 752 753config SHADOW_CALL_STACK 754 bool "Shadow Call Stack" 755 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 756 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 757 depends on MMU 758 help 759 This option enables the compiler's Shadow Call Stack, which 760 uses a shadow stack to protect function return addresses from 761 being overwritten by an attacker. More information can be found 762 in the compiler's documentation: 763 764 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 765 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 766 767 Note that security guarantees in the kernel differ from the 768 ones documented for user space. The kernel must store addresses 769 of shadow stacks in memory, which means an attacker capable of 770 reading and writing arbitrary memory may be able to locate them 771 and hijack control flow by modifying the stacks. 772 773config DYNAMIC_SCS 774 bool 775 help 776 Set by the arch code if it relies on code patching to insert the 777 shadow call stack push and pop instructions rather than on the 778 compiler. 779 780config LTO 781 bool 782 help 783 Selected if the kernel will be built using the compiler's LTO feature. 784 785config LTO_CLANG 786 bool 787 select LTO 788 help 789 Selected if the kernel will be built using Clang's LTO feature. 790 791config ARCH_SUPPORTS_LTO_CLANG 792 bool 793 help 794 An architecture should select this option if it supports: 795 - compiling with Clang, 796 - compiling inline assembly with Clang's integrated assembler, 797 - and linking with LLD. 798 799config ARCH_SUPPORTS_LTO_CLANG_THIN 800 bool 801 help 802 An architecture should select this option if it can support Clang's 803 ThinLTO mode. 804 805config HAS_LTO_CLANG 806 def_bool y 807 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 808 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 809 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 810 depends on ARCH_SUPPORTS_LTO_CLANG 811 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 812 # https://github.com/ClangBuiltLinux/linux/issues/1721 813 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 814 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 815 depends on !GCOV_KERNEL 816 help 817 The compiler and Kconfig options support building with Clang's 818 LTO. 819 820choice 821 prompt "Link Time Optimization (LTO)" 822 default LTO_NONE 823 help 824 This option enables Link Time Optimization (LTO), which allows the 825 compiler to optimize binaries globally. 826 827 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 828 so it's disabled by default. 829 830config LTO_NONE 831 bool "None" 832 help 833 Build the kernel normally, without Link Time Optimization (LTO). 834 835config LTO_CLANG_FULL 836 bool "Clang Full LTO (EXPERIMENTAL)" 837 depends on HAS_LTO_CLANG 838 depends on !COMPILE_TEST 839 select LTO_CLANG 840 help 841 This option enables Clang's full Link Time Optimization (LTO), which 842 allows the compiler to optimize the kernel globally. If you enable 843 this option, the compiler generates LLVM bitcode instead of ELF 844 object files, and the actual compilation from bitcode happens at 845 the LTO link step, which may take several minutes depending on the 846 kernel configuration. More information can be found from LLVM's 847 documentation: 848 849 https://llvm.org/docs/LinkTimeOptimization.html 850 851 During link time, this option can use a large amount of RAM, and 852 may take much longer than the ThinLTO option. 853 854config LTO_CLANG_THIN 855 bool "Clang ThinLTO (EXPERIMENTAL)" 856 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 857 select LTO_CLANG 858 help 859 This option enables Clang's ThinLTO, which allows for parallel 860 optimization and faster incremental compiles compared to the 861 CONFIG_LTO_CLANG_FULL option. More information can be found 862 from Clang's documentation: 863 864 https://clang.llvm.org/docs/ThinLTO.html 865 866 If unsure, say Y. 867endchoice 868 869config ARCH_SUPPORTS_AUTOFDO_CLANG 870 bool 871 872config AUTOFDO_CLANG 873 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 874 depends on ARCH_SUPPORTS_AUTOFDO_CLANG 875 depends on CC_IS_CLANG && CLANG_VERSION >= 170000 876 help 877 This option enables Clang’s AutoFDO build. When 878 an AutoFDO profile is specified in variable 879 CLANG_AUTOFDO_PROFILE during the build process, 880 Clang uses the profile to optimize the kernel. 881 882 If no profile is specified, AutoFDO options are 883 still passed to Clang to facilitate the collection 884 of perf data for creating an AutoFDO profile in 885 subsequent builds. 886 887 If unsure, say N. 888 889config ARCH_SUPPORTS_PROPELLER_CLANG 890 bool 891 892config PROPELLER_CLANG 893 bool "Enable Clang's Propeller build" 894 depends on ARCH_SUPPORTS_PROPELLER_CLANG 895 depends on CC_IS_CLANG && CLANG_VERSION >= 190000 896 help 897 This option enables Clang’s Propeller build. When the Propeller 898 profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX 899 during the build process, Clang uses the profiles to optimize 900 the kernel. 901 902 If no profile is specified, Propeller options are still passed 903 to Clang to facilitate the collection of perf data for creating 904 the Propeller profiles in subsequent builds. 905 906 If unsure, say N. 907 908config ARCH_SUPPORTS_CFI_CLANG 909 bool 910 help 911 An architecture should select this option if it can support Clang's 912 Control-Flow Integrity (CFI) checking. 913 914config ARCH_USES_CFI_TRAPS 915 bool 916 917config CFI_CLANG 918 bool "Use Clang's Control Flow Integrity (CFI)" 919 depends on ARCH_SUPPORTS_CFI_CLANG 920 depends on $(cc-option,-fsanitize=kcfi) 921 help 922 This option enables Clang's forward-edge Control Flow Integrity 923 (CFI) checking, where the compiler injects a runtime check to each 924 indirect function call to ensure the target is a valid function with 925 the correct static type. This restricts possible call targets and 926 makes it more difficult for an attacker to exploit bugs that allow 927 the modification of stored function pointers. More information can be 928 found from Clang's documentation: 929 930 https://clang.llvm.org/docs/ControlFlowIntegrity.html 931 932config CFI_ICALL_NORMALIZE_INTEGERS 933 bool "Normalize CFI tags for integers" 934 depends on CFI_CLANG 935 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 936 help 937 This option normalizes the CFI tags for integer types so that all 938 integer types of the same size and signedness receive the same CFI 939 tag. 940 941 The option is separate from CONFIG_RUST because it affects the ABI. 942 When working with build systems that care about the ABI, it is 943 convenient to be able to turn on this flag first, before Rust is 944 turned on. 945 946 This option is necessary for using CFI with Rust. If unsure, say N. 947 948config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 949 def_bool y 950 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 951 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 952 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 953 954config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 955 def_bool y 956 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 957 depends on RUSTC_VERSION >= 107900 958 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 959 depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \ 960 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 961 962config CFI_PERMISSIVE 963 bool "Use CFI in permissive mode" 964 depends on CFI_CLANG 965 help 966 When selected, Control Flow Integrity (CFI) violations result in a 967 warning instead of a kernel panic. This option should only be used 968 for finding indirect call type mismatches during development. 969 970 If unsure, say N. 971 972config HAVE_ARCH_WITHIN_STACK_FRAMES 973 bool 974 help 975 An architecture should select this if it can walk the kernel stack 976 frames to determine if an object is part of either the arguments 977 or local variables (i.e. that it excludes saved return addresses, 978 and similar) by implementing an inline arch_within_stack_frames(), 979 which is used by CONFIG_HARDENED_USERCOPY. 980 981config HAVE_CONTEXT_TRACKING_USER 982 bool 983 help 984 Provide kernel/user boundaries probes necessary for subsystems 985 that need it, such as userspace RCU extended quiescent state. 986 Syscalls need to be wrapped inside user_exit()-user_enter(), either 987 optimized behind static key or through the slow path using TIF_NOHZ 988 flag. Exceptions handlers must be wrapped as well. Irqs are already 989 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 990 handling on irq exit still need to be protected. 991 992config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 993 bool 994 help 995 Architecture neither relies on exception_enter()/exception_exit() 996 nor on schedule_user(). Also preempt_schedule_notrace() and 997 preempt_schedule_irq() can't be called in a preemptible section 998 while context tracking is CT_STATE_USER. This feature reflects a sane 999 entry implementation where the following requirements are met on 1000 critical entry code, ie: before user_exit() or after user_enter(): 1001 1002 - Critical entry code isn't preemptible (or better yet: 1003 not interruptible). 1004 - No use of RCU read side critical sections, unless ct_nmi_enter() 1005 got called. 1006 - No use of instrumentation, unless instrumentation_begin() got 1007 called. 1008 1009config HAVE_TIF_NOHZ 1010 bool 1011 help 1012 Arch relies on TIF_NOHZ and syscall slow path to implement context 1013 tracking calls to user_enter()/user_exit(). 1014 1015config HAVE_VIRT_CPU_ACCOUNTING 1016 bool 1017 1018config HAVE_VIRT_CPU_ACCOUNTING_IDLE 1019 bool 1020 help 1021 Architecture has its own way to account idle CPU time and therefore 1022 doesn't implement vtime_account_idle(). 1023 1024config ARCH_HAS_SCALED_CPUTIME 1025 bool 1026 1027config HAVE_VIRT_CPU_ACCOUNTING_GEN 1028 bool 1029 default y if 64BIT 1030 help 1031 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 1032 Before enabling this option, arch code must be audited 1033 to ensure there are no races in concurrent read/write of 1034 cputime_t. For example, reading/writing 64-bit cputime_t on 1035 some 32-bit arches may require multiple accesses, so proper 1036 locking is needed to protect against concurrent accesses. 1037 1038config HAVE_IRQ_TIME_ACCOUNTING 1039 bool 1040 help 1041 Archs need to ensure they use a high enough resolution clock to 1042 support irq time accounting and then call enable_sched_clock_irqtime(). 1043 1044config HAVE_MOVE_PUD 1045 bool 1046 help 1047 Architectures that select this are able to move page tables at the 1048 PUD level. If there are only 3 page table levels, the move effectively 1049 happens at the PGD level. 1050 1051config HAVE_MOVE_PMD 1052 bool 1053 help 1054 Archs that select this are able to move page tables at the PMD level. 1055 1056config HAVE_ARCH_TRANSPARENT_HUGEPAGE 1057 bool 1058 1059config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1060 bool 1061 1062config HAVE_ARCH_HUGE_VMAP 1063 bool 1064 1065# 1066# Archs that select this would be capable of PMD-sized vmaps (i.e., 1067# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 1068# must be used to enable allocations to use hugepages. 1069# 1070config HAVE_ARCH_HUGE_VMALLOC 1071 depends on HAVE_ARCH_HUGE_VMAP 1072 bool 1073 1074config ARCH_WANT_HUGE_PMD_SHARE 1075 bool 1076 1077# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1078# if there are no userspace memory management features that use it 1079config ARCH_WANT_KERNEL_PMD_MKWRITE 1080 bool 1081 1082config ARCH_WANT_PMD_MKWRITE 1083 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1084 1085config HAVE_ARCH_SOFT_DIRTY 1086 bool 1087 1088config HAVE_MOD_ARCH_SPECIFIC 1089 bool 1090 help 1091 The arch uses struct mod_arch_specific to store data. Many arches 1092 just need a simple module loader without arch specific data - those 1093 should not enable this. 1094 1095config MODULES_USE_ELF_RELA 1096 bool 1097 help 1098 Modules only use ELF RELA relocations. Modules with ELF REL 1099 relocations will give an error. 1100 1101config MODULES_USE_ELF_REL 1102 bool 1103 help 1104 Modules only use ELF REL relocations. Modules with ELF RELA 1105 relocations will give an error. 1106 1107config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1108 bool 1109 help 1110 For architectures like powerpc/32 which have constraints on module 1111 allocation and need to allocate module data outside of module area. 1112 1113config ARCH_WANTS_EXECMEM_LATE 1114 bool 1115 help 1116 For architectures that do not allocate executable memory early on 1117 boot, but rather require its initialization late when there is 1118 enough entropy for module space randomization, for instance 1119 arm64. 1120 1121config ARCH_HAS_EXECMEM_ROX 1122 bool 1123 depends on MMU && !HIGHMEM 1124 help 1125 For architectures that support allocations of executable memory 1126 with read-only execute permissions. Architecture must implement 1127 execmem_fill_trapping_insns() callback to enable this. 1128 1129config HAVE_IRQ_EXIT_ON_IRQ_STACK 1130 bool 1131 help 1132 Architecture doesn't only execute the irq handler on the irq stack 1133 but also irq_exit(). This way we can process softirqs on this irq 1134 stack instead of switching to a new one when we call __do_softirq() 1135 in the end of an hardirq. 1136 This spares a stack switch and improves cache usage on softirq 1137 processing. 1138 1139config HAVE_SOFTIRQ_ON_OWN_STACK 1140 bool 1141 help 1142 Architecture provides a function to run __do_softirq() on a 1143 separate stack. 1144 1145config SOFTIRQ_ON_OWN_STACK 1146 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1147 1148config ALTERNATE_USER_ADDRESS_SPACE 1149 bool 1150 help 1151 Architectures set this when the CPU uses separate address 1152 spaces for kernel and user space pointers. In this case, the 1153 access_ok() check on a __user pointer is skipped. 1154 1155config PGTABLE_LEVELS 1156 int 1157 default 2 1158 1159config ARCH_HAS_ELF_RANDOMIZE 1160 bool 1161 help 1162 An architecture supports choosing randomized locations for 1163 stack, mmap, brk, and ET_DYN. Defined functions: 1164 - arch_mmap_rnd() 1165 - arch_randomize_brk() 1166 1167config HAVE_ARCH_MMAP_RND_BITS 1168 bool 1169 help 1170 An arch should select this symbol if it supports setting a variable 1171 number of bits for use in establishing the base address for mmap 1172 allocations, has MMU enabled and provides values for both: 1173 - ARCH_MMAP_RND_BITS_MIN 1174 - ARCH_MMAP_RND_BITS_MAX 1175 1176config HAVE_EXIT_THREAD 1177 bool 1178 help 1179 An architecture implements exit_thread. 1180 1181config ARCH_MMAP_RND_BITS_MIN 1182 int 1183 1184config ARCH_MMAP_RND_BITS_MAX 1185 int 1186 1187config ARCH_MMAP_RND_BITS_DEFAULT 1188 int 1189 1190config ARCH_MMAP_RND_BITS 1191 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1192 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1193 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1194 default ARCH_MMAP_RND_BITS_MIN 1195 depends on HAVE_ARCH_MMAP_RND_BITS 1196 help 1197 This value can be used to select the number of bits to use to 1198 determine the random offset to the base address of vma regions 1199 resulting from mmap allocations. This value will be bounded 1200 by the architecture's minimum and maximum supported values. 1201 1202 This value can be changed after boot using the 1203 /proc/sys/vm/mmap_rnd_bits tunable 1204 1205config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1206 bool 1207 help 1208 An arch should select this symbol if it supports running applications 1209 in compatibility mode, supports setting a variable number of bits for 1210 use in establishing the base address for mmap allocations, has MMU 1211 enabled and provides values for both: 1212 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1213 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1214 1215config ARCH_MMAP_RND_COMPAT_BITS_MIN 1216 int 1217 1218config ARCH_MMAP_RND_COMPAT_BITS_MAX 1219 int 1220 1221config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1222 int 1223 1224config ARCH_MMAP_RND_COMPAT_BITS 1225 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1226 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1227 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1228 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1229 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1230 help 1231 This value can be used to select the number of bits to use to 1232 determine the random offset to the base address of vma regions 1233 resulting from mmap allocations for compatible applications This 1234 value will be bounded by the architecture's minimum and maximum 1235 supported values. 1236 1237 This value can be changed after boot using the 1238 /proc/sys/vm/mmap_rnd_compat_bits tunable 1239 1240config HAVE_ARCH_COMPAT_MMAP_BASES 1241 bool 1242 help 1243 This allows 64bit applications to invoke 32-bit mmap() syscall 1244 and vice-versa 32-bit applications to call 64-bit mmap(). 1245 Required for applications doing different bitness syscalls. 1246 1247config HAVE_PAGE_SIZE_4KB 1248 bool 1249 1250config HAVE_PAGE_SIZE_8KB 1251 bool 1252 1253config HAVE_PAGE_SIZE_16KB 1254 bool 1255 1256config HAVE_PAGE_SIZE_32KB 1257 bool 1258 1259config HAVE_PAGE_SIZE_64KB 1260 bool 1261 1262config HAVE_PAGE_SIZE_256KB 1263 bool 1264 1265choice 1266 prompt "MMU page size" 1267 1268config PAGE_SIZE_4KB 1269 bool "4KiB pages" 1270 depends on HAVE_PAGE_SIZE_4KB 1271 help 1272 This option select the standard 4KiB Linux page size and the only 1273 available option on many architectures. Using 4KiB page size will 1274 minimize memory consumption and is therefore recommended for low 1275 memory systems. 1276 Some software that is written for x86 systems makes incorrect 1277 assumptions about the page size and only runs on 4KiB pages. 1278 1279config PAGE_SIZE_8KB 1280 bool "8KiB pages" 1281 depends on HAVE_PAGE_SIZE_8KB 1282 help 1283 This option is the only supported page size on a few older 1284 processors, and can be slightly faster than 4KiB pages. 1285 1286config PAGE_SIZE_16KB 1287 bool "16KiB pages" 1288 depends on HAVE_PAGE_SIZE_16KB 1289 help 1290 This option is usually a good compromise between memory 1291 consumption and performance for typical desktop and server 1292 workloads, often saving a level of page table lookups compared 1293 to 4KB pages as well as reducing TLB pressure and overhead of 1294 per-page operations in the kernel at the expense of a larger 1295 page cache. 1296 1297config PAGE_SIZE_32KB 1298 bool "32KiB pages" 1299 depends on HAVE_PAGE_SIZE_32KB 1300 help 1301 Using 32KiB page size will result in slightly higher performance 1302 kernel at the price of higher memory consumption compared to 1303 16KiB pages. This option is available only on cnMIPS cores. 1304 Note that you will need a suitable Linux distribution to 1305 support this. 1306 1307config PAGE_SIZE_64KB 1308 bool "64KiB pages" 1309 depends on HAVE_PAGE_SIZE_64KB 1310 help 1311 Using 64KiB page size will result in slightly higher performance 1312 kernel at the price of much higher memory consumption compared to 1313 4KiB or 16KiB pages. 1314 This is not suitable for general-purpose workloads but the 1315 better performance may be worth the cost for certain types of 1316 supercomputing or database applications that work mostly with 1317 large in-memory data rather than small files. 1318 1319config PAGE_SIZE_256KB 1320 bool "256KiB pages" 1321 depends on HAVE_PAGE_SIZE_256KB 1322 help 1323 256KiB pages have little practical value due to their extreme 1324 memory usage. The kernel will only be able to run applications 1325 that have been compiled with '-zmax-page-size' set to 256KiB 1326 (the default is 64KiB or 4KiB on most architectures). 1327 1328endchoice 1329 1330config PAGE_SIZE_LESS_THAN_64KB 1331 def_bool y 1332 depends on !PAGE_SIZE_64KB 1333 depends on PAGE_SIZE_LESS_THAN_256KB 1334 1335config PAGE_SIZE_LESS_THAN_256KB 1336 def_bool y 1337 depends on !PAGE_SIZE_256KB 1338 1339config PAGE_SHIFT 1340 int 1341 default 12 if PAGE_SIZE_4KB 1342 default 13 if PAGE_SIZE_8KB 1343 default 14 if PAGE_SIZE_16KB 1344 default 15 if PAGE_SIZE_32KB 1345 default 16 if PAGE_SIZE_64KB 1346 default 18 if PAGE_SIZE_256KB 1347 1348# This allows to use a set of generic functions to determine mmap base 1349# address by giving priority to top-down scheme only if the process 1350# is not in legacy mode (compat task, unlimited stack size or 1351# sysctl_legacy_va_layout). 1352# Architecture that selects this option can provide its own version of: 1353# - STACK_RND_MASK 1354config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1355 bool 1356 depends on MMU 1357 select ARCH_HAS_ELF_RANDOMIZE 1358 1359config HAVE_OBJTOOL 1360 bool 1361 1362config HAVE_JUMP_LABEL_HACK 1363 bool 1364 1365config HAVE_NOINSTR_HACK 1366 bool 1367 1368config HAVE_NOINSTR_VALIDATION 1369 bool 1370 1371config HAVE_UACCESS_VALIDATION 1372 bool 1373 select OBJTOOL 1374 1375config HAVE_STACK_VALIDATION 1376 bool 1377 help 1378 Architecture supports objtool compile-time frame pointer rule 1379 validation. 1380 1381config HAVE_RELIABLE_STACKTRACE 1382 bool 1383 help 1384 Architecture has either save_stack_trace_tsk_reliable() or 1385 arch_stack_walk_reliable() function which only returns a stack trace 1386 if it can guarantee the trace is reliable. 1387 1388config HAVE_ARCH_HASH 1389 bool 1390 default n 1391 help 1392 If this is set, the architecture provides an <asm/hash.h> 1393 file which provides platform-specific implementations of some 1394 functions in <linux/hash.h> or fs/namei.c. 1395 1396config HAVE_ARCH_NVRAM_OPS 1397 bool 1398 1399config ISA_BUS_API 1400 def_bool ISA 1401 1402# 1403# ABI hall of shame 1404# 1405config CLONE_BACKWARDS 1406 bool 1407 help 1408 Architecture has tls passed as the 4th argument of clone(2), 1409 not the 5th one. 1410 1411config CLONE_BACKWARDS2 1412 bool 1413 help 1414 Architecture has the first two arguments of clone(2) swapped. 1415 1416config CLONE_BACKWARDS3 1417 bool 1418 help 1419 Architecture has tls passed as the 3rd argument of clone(2), 1420 not the 5th one. 1421 1422config ODD_RT_SIGACTION 1423 bool 1424 help 1425 Architecture has unusual rt_sigaction(2) arguments 1426 1427config OLD_SIGSUSPEND 1428 bool 1429 help 1430 Architecture has old sigsuspend(2) syscall, of one-argument variety 1431 1432config OLD_SIGSUSPEND3 1433 bool 1434 help 1435 Even weirder antique ABI - three-argument sigsuspend(2) 1436 1437config OLD_SIGACTION 1438 bool 1439 help 1440 Architecture has old sigaction(2) syscall. Nope, not the same 1441 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1442 but fairly different variant of sigaction(2), thanks to OSF/1 1443 compatibility... 1444 1445config COMPAT_OLD_SIGACTION 1446 bool 1447 1448config COMPAT_32BIT_TIME 1449 bool "Provide system calls for 32-bit time_t" 1450 default !64BIT || COMPAT 1451 help 1452 This enables 32 bit time_t support in addition to 64 bit time_t support. 1453 This is relevant on all 32-bit architectures, and 64-bit architectures 1454 as part of compat syscall handling. 1455 1456config ARCH_NO_PREEMPT 1457 bool 1458 1459config ARCH_SUPPORTS_RT 1460 bool 1461 1462config CPU_NO_EFFICIENT_FFS 1463 def_bool n 1464 1465config HAVE_ARCH_VMAP_STACK 1466 def_bool n 1467 help 1468 An arch should select this symbol if it can support kernel stacks 1469 in vmalloc space. This means: 1470 1471 - vmalloc space must be large enough to hold many kernel stacks. 1472 This may rule out many 32-bit architectures. 1473 1474 - Stacks in vmalloc space need to work reliably. For example, if 1475 vmap page tables are created on demand, either this mechanism 1476 needs to work while the stack points to a virtual address with 1477 unpopulated page tables or arch code (switch_to() and switch_mm(), 1478 most likely) needs to ensure that the stack's page table entries 1479 are populated before running on a possibly unpopulated stack. 1480 1481 - If the stack overflows into a guard page, something reasonable 1482 should happen. The definition of "reasonable" is flexible, but 1483 instantly rebooting without logging anything would be unfriendly. 1484 1485config VMAP_STACK 1486 default y 1487 bool "Use a virtually-mapped stack" 1488 depends on HAVE_ARCH_VMAP_STACK 1489 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1490 help 1491 Enable this if you want the use virtually-mapped kernel stacks 1492 with guard pages. This causes kernel stack overflows to be 1493 caught immediately rather than causing difficult-to-diagnose 1494 corruption. 1495 1496 To use this with software KASAN modes, the architecture must support 1497 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1498 must be enabled. 1499 1500config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1501 def_bool n 1502 help 1503 An arch should select this symbol if it can support kernel stack 1504 offset randomization with calls to add_random_kstack_offset() 1505 during syscall entry and choose_random_kstack_offset() during 1506 syscall exit. Careful removal of -fstack-protector-strong and 1507 -fstack-protector should also be applied to the entry code and 1508 closely examined, as the artificial stack bump looks like an array 1509 to the compiler, so it will attempt to add canary checks regardless 1510 of the static branch state. 1511 1512config RANDOMIZE_KSTACK_OFFSET 1513 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1514 default y 1515 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1516 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1517 help 1518 The kernel stack offset can be randomized (after pt_regs) by 1519 roughly 5 bits of entropy, frustrating memory corruption 1520 attacks that depend on stack address determinism or 1521 cross-syscall address exposures. 1522 1523 The feature is controlled via the "randomize_kstack_offset=on/off" 1524 kernel boot param, and if turned off has zero overhead due to its use 1525 of static branches (see JUMP_LABEL). 1526 1527 If unsure, say Y. 1528 1529config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1530 bool "Default state of kernel stack offset randomization" 1531 depends on RANDOMIZE_KSTACK_OFFSET 1532 help 1533 Kernel stack offset randomization is controlled by kernel boot param 1534 "randomize_kstack_offset=on/off", and this config chooses the default 1535 boot state. 1536 1537config ARCH_OPTIONAL_KERNEL_RWX 1538 def_bool n 1539 1540config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1541 def_bool n 1542 1543config ARCH_HAS_STRICT_KERNEL_RWX 1544 def_bool n 1545 1546config STRICT_KERNEL_RWX 1547 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1548 depends on ARCH_HAS_STRICT_KERNEL_RWX 1549 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1550 help 1551 If this is set, kernel text and rodata memory will be made read-only, 1552 and non-text memory will be made non-executable. This provides 1553 protection against certain security exploits (e.g. executing the heap 1554 or modifying text) 1555 1556 These features are considered standard security practice these days. 1557 You should say Y here in almost all cases. 1558 1559config ARCH_HAS_STRICT_MODULE_RWX 1560 def_bool n 1561 1562config STRICT_MODULE_RWX 1563 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1564 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1565 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1566 help 1567 If this is set, module text and rodata memory will be made read-only, 1568 and non-text memory will be made non-executable. This provides 1569 protection against certain security exploits (e.g. writing to text) 1570 1571# select if the architecture provides an asm/dma-direct.h header 1572config ARCH_HAS_PHYS_TO_DMA 1573 bool 1574 1575config ARCH_HAS_CPU_RESCTRL 1576 bool 1577 help 1578 An architecture selects this option to indicate that the necessary 1579 hooks are provided to support the common memory system usage 1580 monitoring and control interfaces provided by the 'resctrl' 1581 filesystem (see RESCTRL_FS). 1582 1583config HAVE_ARCH_COMPILER_H 1584 bool 1585 help 1586 An architecture can select this if it provides an 1587 asm/compiler.h header that should be included after 1588 linux/compiler-*.h in order to override macro definitions that those 1589 headers generally provide. 1590 1591config HAVE_ARCH_LIBGCC_H 1592 bool 1593 help 1594 An architecture can select this if it provides an 1595 asm/libgcc.h header that should be included after 1596 linux/libgcc.h in order to override macro definitions that 1597 header generally provides. 1598 1599config HAVE_ARCH_PREL32_RELOCATIONS 1600 bool 1601 help 1602 May be selected by an architecture if it supports place-relative 1603 32-bit relocations, both in the toolchain and in the module loader, 1604 in which case relative references can be used in special sections 1605 for PCI fixup, initcalls etc which are only half the size on 64 bit 1606 architectures, and don't require runtime relocation on relocatable 1607 kernels. 1608 1609config ARCH_USE_MEMREMAP_PROT 1610 bool 1611 1612config LOCK_EVENT_COUNTS 1613 bool "Locking event counts collection" 1614 depends on DEBUG_FS 1615 help 1616 Enable light-weight counting of various locking related events 1617 in the system with minimal performance impact. This reduces 1618 the chance of application behavior change because of timing 1619 differences. The counts are reported via debugfs. 1620 1621# Select if the architecture has support for applying RELR relocations. 1622config ARCH_HAS_RELR 1623 bool 1624 1625config RELR 1626 bool "Use RELR relocation packing" 1627 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1628 default y 1629 help 1630 Store the kernel's dynamic relocations in the RELR relocation packing 1631 format. Requires a compatible linker (LLD supports this feature), as 1632 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1633 are compatible). 1634 1635config ARCH_HAS_MEM_ENCRYPT 1636 bool 1637 1638config ARCH_HAS_CC_PLATFORM 1639 bool 1640 1641config HAVE_SPARSE_SYSCALL_NR 1642 bool 1643 help 1644 An architecture should select this if its syscall numbering is sparse 1645 to save space. For example, MIPS architecture has a syscall array with 1646 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1647 related optimizations for a given architecture. 1648 1649config ARCH_HAS_VDSO_ARCH_DATA 1650 depends on GENERIC_VDSO_DATA_STORE 1651 bool 1652 1653config ARCH_HAS_VDSO_TIME_DATA 1654 bool 1655 1656config HAVE_STATIC_CALL 1657 bool 1658 1659config HAVE_STATIC_CALL_INLINE 1660 bool 1661 depends on HAVE_STATIC_CALL 1662 select OBJTOOL 1663 1664config HAVE_PREEMPT_DYNAMIC 1665 bool 1666 1667config HAVE_PREEMPT_DYNAMIC_CALL 1668 bool 1669 depends on HAVE_STATIC_CALL 1670 select HAVE_PREEMPT_DYNAMIC 1671 help 1672 An architecture should select this if it can handle the preemption 1673 model being selected at boot time using static calls. 1674 1675 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1676 preemption function will be patched directly. 1677 1678 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1679 call to a preemption function will go through a trampoline, and the 1680 trampoline will be patched. 1681 1682 It is strongly advised to support inline static call to avoid any 1683 overhead. 1684 1685config HAVE_PREEMPT_DYNAMIC_KEY 1686 bool 1687 depends on HAVE_ARCH_JUMP_LABEL 1688 select HAVE_PREEMPT_DYNAMIC 1689 help 1690 An architecture should select this if it can handle the preemption 1691 model being selected at boot time using static keys. 1692 1693 Each preemption function will be given an early return based on a 1694 static key. This should have slightly lower overhead than non-inline 1695 static calls, as this effectively inlines each trampoline into the 1696 start of its callee. This may avoid redundant work, and may 1697 integrate better with CFI schemes. 1698 1699 This will have greater overhead than using inline static calls as 1700 the call to the preemption function cannot be entirely elided. 1701 1702config ARCH_WANT_LD_ORPHAN_WARN 1703 bool 1704 help 1705 An arch should select this symbol once all linker sections are explicitly 1706 included, size-asserted, or discarded in the linker scripts. This is 1707 important because we never want expected sections to be placed heuristically 1708 by the linker, since the locations of such sections can change between linker 1709 versions. 1710 1711config HAVE_ARCH_PFN_VALID 1712 bool 1713 1714config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1715 bool 1716 1717config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1718 bool 1719 1720config ARCH_SPLIT_ARG64 1721 bool 1722 help 1723 If a 32-bit architecture requires 64-bit arguments to be split into 1724 pairs of 32-bit arguments, select this option. 1725 1726config ARCH_HAS_ELFCORE_COMPAT 1727 bool 1728 1729config ARCH_HAS_PARANOID_L1D_FLUSH 1730 bool 1731 1732config ARCH_HAVE_TRACE_MMIO_ACCESS 1733 bool 1734 1735config DYNAMIC_SIGFRAME 1736 bool 1737 1738# Select, if arch has a named attribute group bound to NUMA device nodes. 1739config HAVE_ARCH_NODE_DEV_GROUP 1740 bool 1741 1742config ARCH_HAS_HW_PTE_YOUNG 1743 bool 1744 help 1745 Architectures that select this option are capable of setting the 1746 accessed bit in PTE entries when using them as part of linear address 1747 translations. Architectures that require runtime check should select 1748 this option and override arch_has_hw_pte_young(). 1749 1750config ARCH_HAS_NONLEAF_PMD_YOUNG 1751 bool 1752 help 1753 Architectures that select this option are capable of setting the 1754 accessed bit in non-leaf PMD entries when using them as part of linear 1755 address translations. Page table walkers that clear the accessed bit 1756 may use this capability to reduce their search space. 1757 1758config ARCH_HAS_KERNEL_FPU_SUPPORT 1759 bool 1760 help 1761 Architectures that select this option can run floating-point code in 1762 the kernel, as described in Documentation/core-api/floating-point.rst. 1763 1764config ARCH_VMLINUX_NEEDS_RELOCS 1765 bool 1766 help 1767 Whether the architecture needs vmlinux to be built with static 1768 relocations preserved. This is used by some architectures to 1769 construct bespoke relocation tables for KASLR. 1770 1771source "kernel/gcov/Kconfig" 1772 1773source "scripts/gcc-plugins/Kconfig" 1774 1775config FUNCTION_ALIGNMENT_4B 1776 bool 1777 1778config FUNCTION_ALIGNMENT_8B 1779 bool 1780 1781config FUNCTION_ALIGNMENT_16B 1782 bool 1783 1784config FUNCTION_ALIGNMENT_32B 1785 bool 1786 1787config FUNCTION_ALIGNMENT_64B 1788 bool 1789 1790config FUNCTION_ALIGNMENT 1791 int 1792 default 64 if FUNCTION_ALIGNMENT_64B 1793 default 32 if FUNCTION_ALIGNMENT_32B 1794 default 16 if FUNCTION_ALIGNMENT_16B 1795 default 8 if FUNCTION_ALIGNMENT_8B 1796 default 4 if FUNCTION_ALIGNMENT_4B 1797 default 0 1798 1799config CC_HAS_MIN_FUNCTION_ALIGNMENT 1800 # Detect availability of the GCC option -fmin-function-alignment which 1801 # guarantees minimal alignment for all functions, unlike 1802 # -falign-functions which the compiler ignores for cold functions. 1803 def_bool $(cc-option, -fmin-function-alignment=8) 1804 1805config CC_HAS_SANE_FUNCTION_ALIGNMENT 1806 # Set if the guaranteed alignment with -fmin-function-alignment is 1807 # available or extra care is required in the kernel. Clang provides 1808 # strict alignment always, even with -falign-functions. 1809 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1810 1811config ARCH_NEED_CMPXCHG_1_EMU 1812 bool 1813 1814config ARCH_WANTS_PRE_LINK_VMLINUX 1815 bool 1816 help 1817 An architecture can select this if it provides arch/<arch>/tools/Makefile 1818 with .arch.vmlinux.o target to be linked into vmlinux. 1819 1820config ARCH_HAS_CPU_ATTACK_VECTORS 1821 bool 1822 1823endmenu 1824