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 ARCH_SUPPORTS_SYSCALL_USER_DISPATCH 118 bool 119 120config SYSCALL_USER_DISPATCH 121 bool "Syscall User Dispatch" 122 depends on ARCH_SUPPORTS_SYSCALL_USER_DISPATCH 123 depends on GENERIC_ENTRY 124 default y 125 help 126 Syscall User Dispatch lets a thread have its own system calls 127 intercepted and redirected to a userspace signal handler based 128 on a prctl() configured instruction pointer range. 129 If unsure, say Y. 130 131config KPROBES 132 bool "Kprobes" 133 depends on HAVE_KPROBES 134 select KALLSYMS 135 select EXECMEM 136 select NEED_TASKS_RCU 137 help 138 Kprobes allows you to trap at almost any kernel address and 139 execute a callback function. register_kprobe() establishes 140 a probepoint and specifies the callback. Kprobes is useful 141 for kernel debugging, non-intrusive instrumentation and testing. 142 If in doubt, say "N". 143 144config JUMP_LABEL 145 bool "Optimize very unlikely/likely branches" 146 depends on HAVE_ARCH_JUMP_LABEL 147 select OBJTOOL if HAVE_JUMP_LABEL_HACK 148 help 149 This option enables a transparent branch optimization that 150 makes certain almost-always-true or almost-always-false branch 151 conditions even cheaper to execute within the kernel. 152 153 Certain performance-sensitive kernel code, such as trace points, 154 scheduler functionality, networking code and KVM have such 155 branches and include support for this optimization technique. 156 157 If it is detected that the compiler has support for "asm goto", 158 the kernel will compile such branches with just a nop 159 instruction. When the condition flag is toggled to true, the 160 nop will be converted to a jump instruction to execute the 161 conditional block of instructions. 162 163 This technique lowers overhead and stress on the branch prediction 164 of the processor and generally makes the kernel faster. The update 165 of the condition is slower, but those are always very rare. 166 167 ( On 32-bit x86, the necessary options added to the compiler 168 flags may increase the size of the kernel slightly. ) 169 170config STATIC_KEYS_SELFTEST 171 bool "Static key selftest" 172 depends on JUMP_LABEL 173 help 174 Boot time self-test of the branch patching code. 175 176config STATIC_CALL_SELFTEST 177 bool "Static call selftest" 178 depends on HAVE_STATIC_CALL 179 help 180 Boot time self-test of the call patching code. 181 182config OPTPROBES 183 def_bool y 184 depends on KPROBES && HAVE_OPTPROBES 185 select NEED_TASKS_RCU 186 187config KPROBES_ON_FTRACE 188 def_bool y 189 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 190 depends on DYNAMIC_FTRACE_WITH_REGS 191 help 192 If function tracer is enabled and the arch supports full 193 passing of pt_regs to function tracing, then kprobes can 194 optimize on top of function tracing. 195 196config UPROBES 197 def_bool n 198 depends on ARCH_SUPPORTS_UPROBES 199 select TASKS_TRACE_RCU 200 help 201 Uprobes is the user-space counterpart to kprobes: they 202 enable instrumentation applications (such as 'perf probe') 203 to establish unintrusive probes in user-space binaries and 204 libraries, by executing handler functions when the probes 205 are hit by user-space applications. 206 207 ( These probes come in the form of single-byte breakpoints, 208 managed by the kernel and kept transparent to the probed 209 application. ) 210 211config HAVE_64BIT_ALIGNED_ACCESS 212 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 213 help 214 Some architectures require 64 bit accesses to be 64 bit 215 aligned, which also requires structs containing 64 bit values 216 to be 64 bit aligned too. This includes some 32 bit 217 architectures which can do 64 bit accesses, as well as 64 bit 218 architectures without unaligned access. 219 220 This symbol should be selected by an architecture if 64 bit 221 accesses are required to be 64 bit aligned in this way even 222 though it is not a 64 bit architecture. 223 224 See Documentation/core-api/unaligned-memory-access.rst for 225 more information on the topic of unaligned memory accesses. 226 227config HAVE_EFFICIENT_UNALIGNED_ACCESS 228 bool 229 help 230 Some architectures are unable to perform unaligned accesses 231 without the use of get_unaligned/put_unaligned. Others are 232 unable to perform such accesses efficiently (e.g. trap on 233 unaligned access and require fixing it up in the exception 234 handler.) 235 236 This symbol should be selected by an architecture if it can 237 perform unaligned accesses efficiently to allow different 238 code paths to be selected for these cases. Some network 239 drivers, for example, could opt to not fix up alignment 240 problems with received packets if doing so would not help 241 much. 242 243 See Documentation/core-api/unaligned-memory-access.rst for more 244 information on the topic of unaligned memory accesses. 245 246config ARCH_USE_BUILTIN_BSWAP 247 bool 248 help 249 GCC and Clang have builtin functions for handling byte-swapping. 250 Using these allows the compiler to see what's happening and 251 offers more opportunity for optimisation. In particular, the 252 compiler will be able to combine the byteswap with a nearby load 253 or store and use load-and-swap or store-and-swap instructions if 254 the architecture has them. It should almost *never* result in code 255 which is worse than the hand-coded assembler in <asm/swab.h>. 256 But just in case it does, the use of the builtins is optional. 257 258 Any architecture with load-and-swap or store-and-swap 259 instructions should set this. And it shouldn't hurt to set it 260 on architectures that don't have such instructions. 261 262config KRETPROBES 263 def_bool y 264 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 265 266config KRETPROBE_ON_RETHOOK 267 def_bool y 268 depends on HAVE_RETHOOK 269 depends on KRETPROBES 270 select RETHOOK 271 272config USER_RETURN_NOTIFIER 273 bool 274 depends on HAVE_USER_RETURN_NOTIFIER 275 help 276 Provide a kernel-internal notification when a cpu is about to 277 switch to user mode. 278 279config HAVE_IOREMAP_PROT 280 bool 281 282config HAVE_KPROBES 283 bool 284 285config HAVE_KRETPROBES 286 bool 287 288config HAVE_OPTPROBES 289 bool 290 291config HAVE_KPROBES_ON_FTRACE 292 bool 293 294config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 295 bool 296 help 297 Since kretprobes modifies return address on the stack, the 298 stacktrace may see the kretprobe trampoline address instead 299 of correct one. If the architecture stacktrace code and 300 unwinder can adjust such entries, select this configuration. 301 302config HAVE_FUNCTION_ERROR_INJECTION 303 bool 304 305config HAVE_NMI 306 bool 307 308config HAVE_FUNCTION_DESCRIPTORS 309 bool 310 311config TRACE_IRQFLAGS_SUPPORT 312 bool 313 314config TRACE_IRQFLAGS_NMI_SUPPORT 315 bool 316 317# 318# An arch should select this if it provides all these things: 319# 320# task_pt_regs() in asm/processor.h or asm/ptrace.h 321# arch_has_single_step() if there is hardware single-step support 322# arch_has_block_step() if there is hardware block-step support 323# asm/syscall.h supplying asm-generic/syscall.h interface 324# linux/regset.h user_regset interfaces 325# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 326# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 327# TIF_NOTIFY_RESUME calls resume_user_mode_work() 328# 329config HAVE_ARCH_TRACEHOOK 330 bool 331 332config HAVE_DMA_CONTIGUOUS 333 bool 334 335config GENERIC_SMP_IDLE_THREAD 336 bool 337 338config GENERIC_IDLE_POLL_SETUP 339 bool 340 341config ARCH_HAS_FORTIFY_SOURCE 342 bool 343 help 344 An architecture should select this when it can successfully 345 build and run with CONFIG_FORTIFY_SOURCE. 346 347# 348# Select if the arch provides a historic keepinit alias for the retain_initrd 349# command line option 350# 351config ARCH_HAS_KEEPINITRD 352 bool 353 354# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 355config ARCH_HAS_SET_MEMORY 356 bool 357 358# Select if arch has all set_direct_map_invalid/default() functions 359config ARCH_HAS_SET_DIRECT_MAP 360 bool 361 362# 363# Select if the architecture provides the arch_dma_set_uncached symbol to 364# either provide an uncached segment alias for a DMA allocation, or 365# to remap the page tables in place. 366# 367config ARCH_HAS_DMA_SET_UNCACHED 368 bool 369 370# 371# Select if the architectures provides the arch_dma_clear_uncached symbol 372# to undo an in-place page table remap for uncached access. 373# 374config ARCH_HAS_DMA_CLEAR_UNCACHED 375 bool 376 377config ARCH_HAS_CPU_FINALIZE_INIT 378 bool 379 380config ARCH_HAS_DELAY_TIMER 381 bool 382 383# The architecture has a per-task state that includes the mm's PASID 384config ARCH_HAS_CPU_PASID 385 bool 386 select IOMMU_MM_DATA 387 388config HAVE_ARCH_THREAD_STRUCT_WHITELIST 389 bool 390 help 391 An architecture should select this to provide hardened usercopy 392 knowledge about what region of the thread_struct should be 393 whitelisted for copying to userspace. Normally this is only the 394 FPU registers. Specifically, arch_thread_struct_whitelist() 395 should be implemented. Without this, the entire thread_struct 396 field in task_struct will be left whitelisted. 397 398# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 399config ARCH_WANTS_DYNAMIC_TASK_STRUCT 400 bool 401 402config ARCH_WANTS_NO_INSTR 403 bool 404 help 405 An architecture should select this if the noinstr macro is being used on 406 functions to denote that the toolchain should avoid instrumenting such 407 functions and is required for correctness. 408 409config ARCH_32BIT_OFF_T 410 bool 411 depends on !64BIT 412 help 413 All new 32-bit architectures should have 64-bit off_t type on 414 userspace side which corresponds to the loff_t kernel type. This 415 is the requirement for modern ABIs. Some existing architectures 416 still support 32-bit off_t. This option is enabled for all such 417 architectures explicitly. 418 419# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 420config ARCH_32BIT_USTAT_F_TINODE 421 bool 422 423# Selected by architectures with Total Store Order (TSO) 424config ARCH_MEMORY_ORDER_TSO 425 bool 426 427config HAVE_ASM_MODVERSIONS 428 bool 429 help 430 This symbol should be selected by an architecture if it provides 431 <asm/asm-prototypes.h> to support the module versioning for symbols 432 exported from assembly code. 433 434config HAVE_REGS_AND_STACK_ACCESS_API 435 bool 436 help 437 This symbol should be selected by an architecture if it supports 438 the API needed to access registers and stack entries from pt_regs, 439 declared in asm/ptrace.h 440 For example the kprobes-based event tracer needs this API. 441 442config HAVE_RSEQ 443 bool 444 depends on HAVE_REGS_AND_STACK_ACCESS_API 445 help 446 This symbol should be selected by an architecture if it 447 supports an implementation of restartable sequences. 448 449config HAVE_RUST 450 bool 451 help 452 This symbol should be selected by an architecture if it 453 supports Rust. 454 455config HAVE_FUNCTION_ARG_ACCESS_API 456 bool 457 help 458 This symbol should be selected by an architecture if it supports 459 the API needed to access function arguments from pt_regs, 460 declared in asm/ptrace.h 461 462config HAVE_HW_BREAKPOINT 463 bool 464 depends on PERF_EVENTS 465 466config HAVE_MIXED_BREAKPOINTS_REGS 467 bool 468 depends on HAVE_HW_BREAKPOINT 469 help 470 Depending on the arch implementation of hardware breakpoints, 471 some of them have separate registers for data and instruction 472 breakpoints addresses, others have mixed registers to store 473 them but define the access type in a control register. 474 Select this option if your arch implements breakpoints under the 475 latter fashion. 476 477config HAVE_USER_RETURN_NOTIFIER 478 bool 479 480config HAVE_PERF_EVENTS_NMI 481 bool 482 help 483 System hardware can generate an NMI using the perf event 484 subsystem. Also has support for calculating CPU cycle events 485 to determine how many clock cycles in a given period. 486 487config HAVE_HARDLOCKUP_DETECTOR_PERF 488 bool 489 depends on HAVE_PERF_EVENTS_NMI 490 help 491 The arch chooses to use the generic perf-NMI-based hardlockup 492 detector. Must define HAVE_PERF_EVENTS_NMI. 493 494config HAVE_HARDLOCKUP_DETECTOR_ARCH 495 bool 496 help 497 The arch provides its own hardlockup detector implementation instead 498 of the generic ones. 499 500 It uses the same command line parameters, and sysctl interface, 501 as the generic hardlockup detectors. 502 503config UNWIND_USER 504 bool 505 506config HAVE_UNWIND_USER_FP 507 bool 508 select UNWIND_USER 509 510config HAVE_PERF_REGS 511 bool 512 help 513 Support selective register dumps for perf events. This includes 514 bit-mapping of each registers and a unique architecture id. 515 516config HAVE_PERF_USER_STACK_DUMP 517 bool 518 help 519 Support user stack dumps for perf event samples. This needs 520 access to the user stack pointer which is not unified across 521 architectures. 522 523config HAVE_ARCH_JUMP_LABEL 524 bool 525 526config HAVE_ARCH_JUMP_LABEL_RELATIVE 527 bool 528 529config MMU_GATHER_TABLE_FREE 530 bool 531 532config MMU_GATHER_RCU_TABLE_FREE 533 bool 534 select MMU_GATHER_TABLE_FREE 535 536config MMU_GATHER_PAGE_SIZE 537 bool 538 539config MMU_GATHER_NO_RANGE 540 bool 541 select MMU_GATHER_MERGE_VMAS 542 543config MMU_GATHER_NO_FLUSH_CACHE 544 bool 545 546config MMU_GATHER_MERGE_VMAS 547 bool 548 549config MMU_GATHER_NO_GATHER 550 bool 551 depends on MMU_GATHER_TABLE_FREE 552 553config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 554 bool 555 help 556 Temporary select until all architectures can be converted to have 557 irqs disabled over activate_mm. Architectures that do IPI based TLB 558 shootdowns should enable this. 559 560# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 561# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 562# to/from kernel threads when the same mm is running on a lot of CPUs (a large 563# multi-threaded application), by reducing contention on the mm refcount. 564# 565# This can be disabled if the architecture ensures no CPUs are using an mm as a 566# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 567# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 568# final exit(2) TLB flush, for example. 569# 570# To implement this, an arch *must*: 571# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 572# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 573# converted already). 574config MMU_LAZY_TLB_REFCOUNT 575 def_bool y 576 depends on !MMU_LAZY_TLB_SHOOTDOWN 577 578# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 579# mm as a lazy tlb beyond its last reference count, by shooting down these 580# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 581# be using the mm as a lazy tlb, so that they may switch themselves to using 582# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 583# may be using mm as a lazy tlb mm. 584# 585# To implement this, an arch *must*: 586# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 587# at least all possible CPUs in which the mm is lazy. 588# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 589config MMU_LAZY_TLB_SHOOTDOWN 590 bool 591 592config ARCH_HAVE_NMI_SAFE_CMPXCHG 593 bool 594 595config ARCH_HAVE_EXTRA_ELF_NOTES 596 bool 597 help 598 An architecture should select this in order to enable adding an 599 arch-specific ELF note section to core files. It must provide two 600 functions: elf_coredump_extra_notes_size() and 601 elf_coredump_extra_notes_write() which are invoked by the ELF core 602 dumper. 603 604config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 605 bool 606 607config HAVE_ALIGNED_STRUCT_PAGE 608 bool 609 help 610 This makes sure that struct pages are double word aligned and that 611 e.g. the SLUB allocator can perform double word atomic operations 612 on a struct page for better performance. However selecting this 613 might increase the size of a struct page by a word. 614 615config HAVE_CMPXCHG_LOCAL 616 bool 617 618config HAVE_CMPXCHG_DOUBLE 619 bool 620 621config ARCH_WEAK_RELEASE_ACQUIRE 622 bool 623 624config ARCH_WANT_IPC_PARSE_VERSION 625 bool 626 627config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 628 bool 629 630config ARCH_WANT_OLD_COMPAT_IPC 631 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 632 bool 633 634config HAVE_ARCH_SECCOMP 635 bool 636 help 637 An arch should select this symbol to support seccomp mode 1 (the fixed 638 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 639 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 640 - __NR_seccomp_read_32 641 - __NR_seccomp_write_32 642 - __NR_seccomp_exit_32 643 - __NR_seccomp_sigreturn_32 644 645config HAVE_ARCH_SECCOMP_FILTER 646 bool 647 select HAVE_ARCH_SECCOMP 648 help 649 An arch should select this symbol if it provides all of these things: 650 - all the requirements for HAVE_ARCH_SECCOMP 651 - syscall_get_arch() 652 - syscall_get_arguments() 653 - syscall_rollback() 654 - syscall_set_return_value() 655 - SIGSYS siginfo_t support 656 - secure_computing is called from a ptrace_event()-safe context 657 - secure_computing return value is checked and if false it 658 results in the system call being skipped immediately. 659 - seccomp syscall wired up 660 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 661 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 662 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 663 664config SECCOMP 665 prompt "Enable seccomp to safely execute untrusted bytecode" 666 def_bool y 667 depends on HAVE_ARCH_SECCOMP 668 help 669 This kernel feature is useful for number crunching applications 670 that may need to handle untrusted bytecode during their 671 execution. By using pipes or other transports made available 672 to the process as file descriptors supporting the read/write 673 syscalls, it's possible to isolate those applications in their 674 own address space using seccomp. Once seccomp is enabled via 675 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 676 disabled and the task is only allowed to execute a few safe 677 syscalls defined by each seccomp mode. 678 679 If unsure, say Y. 680 681config SECCOMP_FILTER 682 def_bool y 683 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 684 help 685 Enable tasks to build secure computing environments defined 686 in terms of Berkeley Packet Filter programs which implement 687 task-defined system call filtering polices. 688 689 See Documentation/userspace-api/seccomp_filter.rst for details. 690 691config SECCOMP_CACHE_DEBUG 692 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 693 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 694 depends on PROC_FS 695 help 696 This enables the /proc/pid/seccomp_cache interface to monitor 697 seccomp cache data. The file format is subject to change. Reading 698 the file requires CAP_SYS_ADMIN. 699 700 This option is for debugging only. Enabling presents the risk that 701 an adversary may be able to infer the seccomp filter logic. 702 703 If unsure, say N. 704 705config HAVE_ARCH_KSTACK_ERASE 706 bool 707 help 708 An architecture should select this if it has the code which 709 fills the used part of the kernel stack with the KSTACK_ERASE_POISON 710 value before returning from system calls. 711 712config HAVE_STACKPROTECTOR 713 bool 714 help 715 An arch should select this symbol if: 716 - it has implemented a stack canary (e.g. __stack_chk_guard) 717 718config STACKPROTECTOR 719 bool "Stack Protector buffer overflow detection" 720 depends on HAVE_STACKPROTECTOR 721 depends on $(cc-option,-fstack-protector) 722 default y 723 help 724 This option turns on the "stack-protector" GCC feature. This 725 feature puts, at the beginning of functions, a canary value on 726 the stack just before the return address, and validates 727 the value just before actually returning. Stack based buffer 728 overflows (that need to overwrite this return address) now also 729 overwrite the canary, which gets detected and the attack is then 730 neutralized via a kernel panic. 731 732 Functions will have the stack-protector canary logic added if they 733 have an 8-byte or larger character array on the stack. 734 735 This feature requires gcc version 4.2 or above, or a distribution 736 gcc with the feature backported ("-fstack-protector"). 737 738 On an x86 "defconfig" build, this feature adds canary checks to 739 about 3% of all kernel functions, which increases kernel code size 740 by about 0.3%. 741 742config STACKPROTECTOR_STRONG 743 bool "Strong Stack Protector" 744 depends on STACKPROTECTOR 745 depends on $(cc-option,-fstack-protector-strong) 746 default y 747 help 748 Functions will have the stack-protector canary logic added in any 749 of the following conditions: 750 751 - local variable's address used as part of the right hand side of an 752 assignment or function argument 753 - local variable is an array (or union containing an array), 754 regardless of array type or length 755 - uses register local variables 756 757 This feature requires gcc version 4.9 or above, or a distribution 758 gcc with the feature backported ("-fstack-protector-strong"). 759 760 On an x86 "defconfig" build, this feature adds canary checks to 761 about 20% of all kernel functions, which increases the kernel code 762 size by about 2%. 763 764config ARCH_SUPPORTS_SHADOW_CALL_STACK 765 bool 766 help 767 An architecture should select this if it supports the compiler's 768 Shadow Call Stack and implements runtime support for shadow stack 769 switching. 770 771config SHADOW_CALL_STACK 772 bool "Shadow Call Stack" 773 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 774 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 775 depends on MMU 776 help 777 This option enables the compiler's Shadow Call Stack, which 778 uses a shadow stack to protect function return addresses from 779 being overwritten by an attacker. More information can be found 780 in the compiler's documentation: 781 782 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 783 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 784 785 Note that security guarantees in the kernel differ from the 786 ones documented for user space. The kernel must store addresses 787 of shadow stacks in memory, which means an attacker capable of 788 reading and writing arbitrary memory may be able to locate them 789 and hijack control flow by modifying the stacks. 790 791config DYNAMIC_SCS 792 bool 793 help 794 Set by the arch code if it relies on code patching to insert the 795 shadow call stack push and pop instructions rather than on the 796 compiler. 797 798config LTO 799 bool 800 help 801 Selected if the kernel will be built using the compiler's LTO feature. 802 803config LTO_CLANG 804 bool 805 select LTO 806 help 807 Selected if the kernel will be built using Clang's LTO feature. 808 809config ARCH_SUPPORTS_LTO_CLANG 810 bool 811 help 812 An architecture should select this option if it supports: 813 - compiling with Clang, 814 - compiling inline assembly with Clang's integrated assembler, 815 - and linking with LLD. 816 817config ARCH_SUPPORTS_LTO_CLANG_THIN 818 bool 819 help 820 An architecture should select this option if it can support Clang's 821 ThinLTO mode. 822 823config HAS_LTO_CLANG 824 def_bool y 825 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 826 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 827 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 828 depends on ARCH_SUPPORTS_LTO_CLANG 829 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 830 depends on !GCOV_KERNEL 831 help 832 The compiler and Kconfig options support building with Clang's 833 LTO. 834 835choice 836 prompt "Link Time Optimization (LTO)" 837 default LTO_NONE 838 help 839 This option enables Link Time Optimization (LTO), which allows the 840 compiler to optimize binaries globally. 841 842 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 843 so it's disabled by default. 844 845config LTO_NONE 846 bool "None" 847 help 848 Build the kernel normally, without Link Time Optimization (LTO). 849 850config LTO_CLANG_FULL 851 bool "Clang Full LTO (EXPERIMENTAL)" 852 depends on HAS_LTO_CLANG 853 depends on !COMPILE_TEST 854 select LTO_CLANG 855 help 856 This option enables Clang's full Link Time Optimization (LTO), which 857 allows the compiler to optimize the kernel globally. If you enable 858 this option, the compiler generates LLVM bitcode instead of ELF 859 object files, and the actual compilation from bitcode happens at 860 the LTO link step, which may take several minutes depending on the 861 kernel configuration. More information can be found from LLVM's 862 documentation: 863 864 https://llvm.org/docs/LinkTimeOptimization.html 865 866 During link time, this option can use a large amount of RAM, and 867 may take much longer than the ThinLTO option. 868 869config LTO_CLANG_THIN 870 bool "Clang ThinLTO (EXPERIMENTAL)" 871 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 872 select LTO_CLANG 873 help 874 This option enables Clang's ThinLTO, which allows for parallel 875 optimization and faster incremental compiles compared to the 876 CONFIG_LTO_CLANG_FULL option. More information can be found 877 from Clang's documentation: 878 879 https://clang.llvm.org/docs/ThinLTO.html 880 881 If unsure, say Y. 882 883config LTO_CLANG_THIN_DIST 884 bool "Clang ThinLTO in distributed mode (EXPERIMENTAL)" 885 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 886 select LTO_CLANG 887 help 888 This option enables Clang's ThinLTO in distributed build mode. 889 In this mode, the linker performs the thin-link, generating 890 ThinLTO index files. Subsequently, the build system explicitly 891 invokes ThinLTO backend compilation using these index files 892 and pre-linked IR objects. The resulting native object files 893 are with the .thinlto-native.o suffix. 894 895 This build mode offers improved visibility into the ThinLTO 896 process through explicit subcommand exposure. It also makes 897 final native object files directly available, benefiting 898 tools like objtool and kpatch. Additionally, it provides 899 crucial granular control over back-end options, enabling 900 module-specific compiler options, and simplifies debugging. 901endchoice 902 903config AUTOFDO_CLANG 904 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 905 depends on CC_IS_CLANG 906 help 907 This option enables Clang’s AutoFDO build. When 908 an AutoFDO profile is specified in variable 909 CLANG_AUTOFDO_PROFILE during the build process, 910 Clang uses the profile to optimize the kernel. 911 912 If no profile is specified, AutoFDO options are 913 still passed to Clang to facilitate the collection 914 of perf data for creating an AutoFDO profile in 915 subsequent builds. 916 917 If unsure, say N. 918 919config PROPELLER_CLANG 920 bool "Enable Clang's Propeller build" 921 depends on CC_IS_CLANG && CLANG_VERSION >= 190000 922 depends on $(cc-option,-fbasic-block-sections=list=/dev/null) 923 help 924 This option enables Clang’s Propeller build. When the Propeller 925 profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX 926 during the build process, Clang uses the profiles to optimize 927 the kernel. 928 929 If no profile is specified, Propeller options are still passed 930 to Clang to facilitate the collection of perf data for creating 931 the Propeller profiles in subsequent builds. 932 933 If unsure, say N. 934 935config ARCH_SUPPORTS_CFI 936 bool 937 help 938 An architecture should select this option if it can support Kernel 939 Control-Flow Integrity (CFI) checking (-fsanitize=kcfi). 940 941config ARCH_USES_CFI_TRAPS 942 bool 943 help 944 An architecture should select this option if it requires the 945 .kcfi_traps section for KCFI trap handling. 946 947config ARCH_USES_CFI_GENERIC_LLVM_PASS 948 bool 949 help 950 An architecture should select this option if it uses the generic 951 KCFIPass in LLVM to expand kCFI bundles instead of architecture-specific 952 lowering. 953 954config CFI 955 bool "Use Kernel Control Flow Integrity (kCFI)" 956 default CFI_CLANG 957 depends on ARCH_SUPPORTS_CFI 958 depends on $(cc-option,-fsanitize=kcfi) 959 help 960 This option enables forward-edge Control Flow Integrity (CFI) 961 checking, where the compiler injects a runtime check to each 962 indirect function call to ensure the target is a valid function with 963 the correct static type. This restricts possible call targets and 964 makes it more difficult for an attacker to exploit bugs that allow 965 the modification of stored function pointers. More information can be 966 found from Clang's documentation: 967 968 https://clang.llvm.org/docs/ControlFlowIntegrity.html 969 970config CFI_CLANG 971 bool 972 transitional 973 help 974 Transitional config for CFI_CLANG to CFI migration. 975 976config CFI_ICALL_NORMALIZE_INTEGERS 977 bool "Normalize CFI tags for integers" 978 depends on CFI 979 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS 980 help 981 This option normalizes the CFI tags for integer types so that all 982 integer types of the same size and signedness receive the same CFI 983 tag. 984 985 The option is separate from CONFIG_RUST because it affects the ABI. 986 When working with build systems that care about the ABI, it is 987 convenient to be able to turn on this flag first, before Rust is 988 turned on. 989 990 This option is necessary for using CFI with Rust. If unsure, say N. 991 992config HAVE_CFI_ICALL_NORMALIZE_INTEGERS 993 def_bool y 994 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 995 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 996 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 997 998config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 999 def_bool y 1000 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS 1001 depends on ARM64 || X86_64 1002 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 1003 depends on RUSTC_LLVM_VERSION >= 190103 || \ 1004 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 1005 1006config CFI_PERMISSIVE 1007 bool "Use CFI in permissive mode" 1008 depends on CFI 1009 help 1010 When selected, Control Flow Integrity (CFI) violations result in a 1011 warning instead of a kernel panic. This option should only be used 1012 for finding indirect call type mismatches during development. 1013 1014 If unsure, say N. 1015 1016config HAVE_ARCH_WITHIN_STACK_FRAMES 1017 bool 1018 help 1019 An architecture should select this if it can walk the kernel stack 1020 frames to determine if an object is part of either the arguments 1021 or local variables (i.e. that it excludes saved return addresses, 1022 and similar) by implementing an inline arch_within_stack_frames(), 1023 which is used by CONFIG_HARDENED_USERCOPY. 1024 1025config HAVE_CONTEXT_TRACKING_USER 1026 bool 1027 help 1028 Provide kernel/user boundaries probes necessary for subsystems 1029 that need it, such as userspace RCU extended quiescent state. 1030 Syscalls need to be wrapped inside user_exit()-user_enter(), either 1031 optimized behind static key or through the slow path using TIF_NOHZ 1032 flag. Exceptions handlers must be wrapped as well. Irqs are already 1033 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 1034 handling on irq exit still need to be protected. 1035 1036config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 1037 bool 1038 help 1039 Architecture neither relies on exception_enter()/exception_exit() 1040 nor on schedule_user(). Also preempt_schedule_notrace() and 1041 preempt_schedule_irq() can't be called in a preemptible section 1042 while context tracking is CT_STATE_USER. This feature reflects a sane 1043 entry implementation where the following requirements are met on 1044 critical entry code, ie: before user_exit() or after user_enter(): 1045 1046 - Critical entry code isn't preemptible (or better yet: 1047 not interruptible). 1048 - No use of RCU read side critical sections, unless ct_nmi_enter() 1049 got called. 1050 - No use of instrumentation, unless instrumentation_begin() got 1051 called. 1052 1053config HAVE_TIF_NOHZ 1054 bool 1055 help 1056 Arch relies on TIF_NOHZ and syscall slow path to implement context 1057 tracking calls to user_enter()/user_exit(). 1058 1059config HAVE_VIRT_CPU_ACCOUNTING 1060 bool 1061 1062config HAVE_VIRT_CPU_ACCOUNTING_IDLE 1063 bool 1064 help 1065 Architecture has its own way to account idle CPU time and therefore 1066 doesn't implement vtime_account_idle(). 1067 1068config ARCH_HAS_SCALED_CPUTIME 1069 bool 1070 1071config HAVE_VIRT_CPU_ACCOUNTING_GEN 1072 bool 1073 default y if 64BIT 1074 help 1075 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 1076 Before enabling this option, arch code must be audited 1077 to ensure there are no races in concurrent read/write of 1078 cputime_t. For example, reading/writing 64-bit cputime_t on 1079 some 32-bit arches may require multiple accesses, so proper 1080 locking is needed to protect against concurrent accesses. 1081 1082config HAVE_IRQ_TIME_ACCOUNTING 1083 bool 1084 help 1085 Archs need to ensure they use a high enough resolution clock to 1086 support irq time accounting and then call enable_sched_clock_irqtime(). 1087 1088config HAVE_PV_STEAL_CLOCK_GEN 1089 bool 1090 1091config HAVE_MOVE_PUD 1092 bool 1093 help 1094 Architectures that select this are able to move page tables at the 1095 PUD level. If there are only 3 page table levels, the move effectively 1096 happens at the PGD level. 1097 1098config HAVE_MOVE_PMD 1099 bool 1100 help 1101 Archs that select this are able to move page tables at the PMD level. 1102 1103config HAVE_ARCH_TRANSPARENT_HUGEPAGE 1104 bool 1105 1106config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1107 bool 1108 1109config HAVE_ARCH_HUGE_VMAP 1110 bool 1111 1112# 1113# Archs that select this would be capable of PMD-sized vmaps (i.e., 1114# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 1115# must be used to enable allocations to use hugepages. 1116# 1117config HAVE_ARCH_HUGE_VMALLOC 1118 depends on HAVE_ARCH_HUGE_VMAP 1119 bool 1120 1121config ARCH_WANT_HUGE_PMD_SHARE 1122 bool 1123 1124# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1125# if there are no userspace memory management features that use it 1126config ARCH_WANT_KERNEL_PMD_MKWRITE 1127 bool 1128 1129config ARCH_WANT_PMD_MKWRITE 1130 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1131 1132config HAVE_ARCH_SOFT_DIRTY 1133 bool 1134 1135config HAVE_MOD_ARCH_SPECIFIC 1136 bool 1137 help 1138 The arch uses struct mod_arch_specific to store data. Many arches 1139 just need a simple module loader without arch specific data - those 1140 should not enable this. 1141 1142config MODULES_USE_ELF_RELA 1143 bool 1144 help 1145 Modules only use ELF RELA relocations. Modules with ELF REL 1146 relocations will give an error. 1147 1148config MODULES_USE_ELF_REL 1149 bool 1150 help 1151 Modules only use ELF REL relocations. Modules with ELF RELA 1152 relocations will give an error. 1153 1154config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1155 bool 1156 help 1157 For architectures like powerpc/32 which have constraints on module 1158 allocation and need to allocate module data outside of module area. 1159 1160config ARCH_WANTS_MODULES_TEXT_SECTIONS 1161 bool 1162 help 1163 For architectures like 32-bit parisc which require that functions in 1164 modules have to keep code in own text sections (-ffunction-sections) 1165 and to avoid merging all text into one big text section, 1166 1167config ARCH_WANTS_EXECMEM_LATE 1168 bool 1169 help 1170 For architectures that do not allocate executable memory early on 1171 boot, but rather require its initialization late when there is 1172 enough entropy for module space randomization, for instance 1173 arm64. 1174 1175config ARCH_HAS_EXECMEM_ROX 1176 bool 1177 depends on MMU && !HIGHMEM 1178 help 1179 For architectures that support allocations of executable memory 1180 with read-only execute permissions. Architecture must implement 1181 execmem_fill_trapping_insns() callback to enable this. 1182 1183config HAVE_IRQ_EXIT_ON_IRQ_STACK 1184 bool 1185 help 1186 Architecture doesn't only execute the irq handler on the irq stack 1187 but also irq_exit(). This way we can process softirqs on this irq 1188 stack instead of switching to a new one when we call __do_softirq() 1189 in the end of an hardirq. 1190 This spares a stack switch and improves cache usage on softirq 1191 processing. 1192 1193config HAVE_SOFTIRQ_ON_OWN_STACK 1194 bool 1195 help 1196 Architecture provides a function to run __do_softirq() on a 1197 separate stack. 1198 1199config SOFTIRQ_ON_OWN_STACK 1200 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1201 1202config ALTERNATE_USER_ADDRESS_SPACE 1203 bool 1204 help 1205 Architectures set this when the CPU uses separate address 1206 spaces for kernel and user space pointers. In this case, the 1207 access_ok() check on a __user pointer is skipped. 1208 1209config PGTABLE_LEVELS 1210 int 1211 default 2 1212 1213config ARCH_HAS_ELF_RANDOMIZE 1214 bool 1215 help 1216 An architecture supports choosing randomized locations for 1217 stack, mmap, brk, and ET_DYN. Defined functions: 1218 - arch_mmap_rnd() 1219 - arch_randomize_brk() 1220 1221config HAVE_ARCH_MMAP_RND_BITS 1222 bool 1223 help 1224 An arch should select this symbol if it supports setting a variable 1225 number of bits for use in establishing the base address for mmap 1226 allocations, has MMU enabled and provides values for both: 1227 - ARCH_MMAP_RND_BITS_MIN 1228 - ARCH_MMAP_RND_BITS_MAX 1229 1230config HAVE_EXIT_THREAD 1231 bool 1232 help 1233 An architecture implements exit_thread. 1234 1235config ARCH_MMAP_RND_BITS_MIN 1236 int 1237 1238config ARCH_MMAP_RND_BITS_MAX 1239 int 1240 1241config ARCH_MMAP_RND_BITS_DEFAULT 1242 int 1243 1244config ARCH_MMAP_RND_BITS 1245 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1246 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1247 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1248 default ARCH_MMAP_RND_BITS_MIN 1249 depends on HAVE_ARCH_MMAP_RND_BITS 1250 help 1251 This value can be used to select the number of bits to use to 1252 determine the random offset to the base address of vma regions 1253 resulting from mmap allocations. This value will be bounded 1254 by the architecture's minimum and maximum supported values. 1255 1256 This value can be changed after boot using the 1257 /proc/sys/vm/mmap_rnd_bits tunable 1258 1259config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1260 bool 1261 help 1262 An arch should select this symbol if it supports running applications 1263 in compatibility mode, supports setting a variable number of bits for 1264 use in establishing the base address for mmap allocations, has MMU 1265 enabled and provides values for both: 1266 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1267 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1268 1269config ARCH_MMAP_RND_COMPAT_BITS_MIN 1270 int 1271 1272config ARCH_MMAP_RND_COMPAT_BITS_MAX 1273 int 1274 1275config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1276 int 1277 1278config ARCH_MMAP_RND_COMPAT_BITS 1279 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1280 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1281 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1282 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1283 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1284 help 1285 This value can be used to select the number of bits to use to 1286 determine the random offset to the base address of vma regions 1287 resulting from mmap allocations for compatible applications This 1288 value will be bounded by the architecture's minimum and maximum 1289 supported values. 1290 1291 This value can be changed after boot using the 1292 /proc/sys/vm/mmap_rnd_compat_bits tunable 1293 1294config HAVE_ARCH_COMPAT_MMAP_BASES 1295 bool 1296 help 1297 This allows 64bit applications to invoke 32-bit mmap() syscall 1298 and vice-versa 32-bit applications to call 64-bit mmap(). 1299 Required for applications doing different bitness syscalls. 1300 1301config HAVE_PAGE_SIZE_4KB 1302 bool 1303 1304config HAVE_PAGE_SIZE_8KB 1305 bool 1306 1307config HAVE_PAGE_SIZE_16KB 1308 bool 1309 1310config HAVE_PAGE_SIZE_32KB 1311 bool 1312 1313config HAVE_PAGE_SIZE_64KB 1314 bool 1315 1316config HAVE_PAGE_SIZE_256KB 1317 bool 1318 1319choice 1320 prompt "MMU page size" 1321 1322config PAGE_SIZE_4KB 1323 bool "4KiB pages" 1324 depends on HAVE_PAGE_SIZE_4KB 1325 help 1326 This option select the standard 4KiB Linux page size and the only 1327 available option on many architectures. Using 4KiB page size will 1328 minimize memory consumption and is therefore recommended for low 1329 memory systems. 1330 Some software that is written for x86 systems makes incorrect 1331 assumptions about the page size and only runs on 4KiB pages. 1332 1333config PAGE_SIZE_8KB 1334 bool "8KiB pages" 1335 depends on HAVE_PAGE_SIZE_8KB 1336 help 1337 This option is the only supported page size on a few older 1338 processors, and can be slightly faster than 4KiB pages. 1339 1340config PAGE_SIZE_16KB 1341 bool "16KiB pages" 1342 depends on HAVE_PAGE_SIZE_16KB 1343 help 1344 This option is usually a good compromise between memory 1345 consumption and performance for typical desktop and server 1346 workloads, often saving a level of page table lookups compared 1347 to 4KB pages as well as reducing TLB pressure and overhead of 1348 per-page operations in the kernel at the expense of a larger 1349 page cache. 1350 1351config PAGE_SIZE_32KB 1352 bool "32KiB pages" 1353 depends on HAVE_PAGE_SIZE_32KB 1354 help 1355 Using 32KiB page size will result in slightly higher performance 1356 kernel at the price of higher memory consumption compared to 1357 16KiB pages. This option is available only on cnMIPS cores. 1358 Note that you will need a suitable Linux distribution to 1359 support this. 1360 1361config PAGE_SIZE_64KB 1362 bool "64KiB pages" 1363 depends on HAVE_PAGE_SIZE_64KB 1364 help 1365 Using 64KiB page size will result in slightly higher performance 1366 kernel at the price of much higher memory consumption compared to 1367 4KiB or 16KiB pages. 1368 This is not suitable for general-purpose workloads but the 1369 better performance may be worth the cost for certain types of 1370 supercomputing or database applications that work mostly with 1371 large in-memory data rather than small files. 1372 1373config PAGE_SIZE_256KB 1374 bool "256KiB pages" 1375 depends on HAVE_PAGE_SIZE_256KB 1376 help 1377 256KiB pages have little practical value due to their extreme 1378 memory usage. The kernel will only be able to run applications 1379 that have been compiled with '-zmax-page-size' set to 256KiB 1380 (the default is 64KiB or 4KiB on most architectures). 1381 1382endchoice 1383 1384config PAGE_SIZE_LESS_THAN_64KB 1385 def_bool y 1386 depends on !PAGE_SIZE_64KB 1387 depends on PAGE_SIZE_LESS_THAN_256KB 1388 1389config PAGE_SIZE_LESS_THAN_256KB 1390 def_bool y 1391 depends on !PAGE_SIZE_256KB 1392 1393config PAGE_SHIFT 1394 int 1395 default 12 if PAGE_SIZE_4KB 1396 default 13 if PAGE_SIZE_8KB 1397 default 14 if PAGE_SIZE_16KB 1398 default 15 if PAGE_SIZE_32KB 1399 default 16 if PAGE_SIZE_64KB 1400 default 18 if PAGE_SIZE_256KB 1401 1402# This allows to use a set of generic functions to determine mmap base 1403# address by giving priority to top-down scheme only if the process 1404# is not in legacy mode (compat task, unlimited stack size or 1405# sysctl_legacy_va_layout). 1406# Architecture that selects this option can provide its own version of: 1407# - STACK_RND_MASK 1408config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1409 bool 1410 depends on MMU 1411 select ARCH_HAS_ELF_RANDOMIZE 1412 1413config HAVE_OBJTOOL 1414 bool 1415 1416config HAVE_JUMP_LABEL_HACK 1417 bool 1418 1419config HAVE_NOINSTR_HACK 1420 bool 1421 1422config HAVE_NOINSTR_VALIDATION 1423 bool 1424 1425config HAVE_UACCESS_VALIDATION 1426 bool 1427 select OBJTOOL 1428 1429config HAVE_STACK_VALIDATION 1430 bool 1431 help 1432 Architecture supports objtool compile-time frame pointer rule 1433 validation. 1434 1435config HAVE_RELIABLE_STACKTRACE 1436 bool 1437 help 1438 Architecture has either save_stack_trace_tsk_reliable() or 1439 arch_stack_walk_reliable() function which only returns a stack trace 1440 if it can guarantee the trace is reliable. 1441 1442config HAVE_ARCH_HASH 1443 bool 1444 default n 1445 help 1446 If this is set, the architecture provides an <asm/hash.h> 1447 file which provides platform-specific implementations of some 1448 functions in <linux/hash.h> or fs/namei.c. 1449 1450config HAVE_ARCH_NVRAM_OPS 1451 bool 1452 1453config ISA_BUS_API 1454 def_bool ISA 1455 1456# 1457# ABI hall of shame 1458# 1459config CLONE_BACKWARDS 1460 bool 1461 help 1462 Architecture has tls passed as the 4th argument of clone(2), 1463 not the 5th one. 1464 1465config CLONE_BACKWARDS2 1466 bool 1467 help 1468 Architecture has the first two arguments of clone(2) swapped. 1469 1470config CLONE_BACKWARDS3 1471 bool 1472 help 1473 Architecture has tls passed as the 3rd argument of clone(2), 1474 not the 5th one. 1475 1476config ODD_RT_SIGACTION 1477 bool 1478 help 1479 Architecture has unusual rt_sigaction(2) arguments 1480 1481config OLD_SIGSUSPEND 1482 bool 1483 help 1484 Architecture has old sigsuspend(2) syscall, of one-argument variety 1485 1486config OLD_SIGSUSPEND3 1487 bool 1488 help 1489 Even weirder antique ABI - three-argument sigsuspend(2) 1490 1491config OLD_SIGACTION 1492 bool 1493 help 1494 Architecture has old sigaction(2) syscall. Nope, not the same 1495 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1496 but fairly different variant of sigaction(2), thanks to OSF/1 1497 compatibility... 1498 1499config COMPAT_OLD_SIGACTION 1500 bool 1501 1502config COMPAT_32BIT_TIME 1503 bool "Provide system calls for 32-bit time_t" 1504 default !64BIT || COMPAT 1505 help 1506 This enables 32 bit time_t support in addition to 64 bit time_t support. 1507 This is relevant on all 32-bit architectures, and 64-bit architectures 1508 as part of compat syscall handling. 1509 1510config ARCH_NO_PREEMPT 1511 bool 1512 1513config ARCH_SUPPORTS_RT 1514 bool 1515 1516config CPU_NO_EFFICIENT_FFS 1517 def_bool n 1518 1519config HAVE_ARCH_VMAP_STACK 1520 def_bool n 1521 help 1522 An arch should select this symbol if it can support kernel stacks 1523 in vmalloc space. This means: 1524 1525 - vmalloc space must be large enough to hold many kernel stacks. 1526 This may rule out many 32-bit architectures. 1527 1528 - Stacks in vmalloc space need to work reliably. For example, if 1529 vmap page tables are created on demand, either this mechanism 1530 needs to work while the stack points to a virtual address with 1531 unpopulated page tables or arch code (switch_to() and switch_mm(), 1532 most likely) needs to ensure that the stack's page table entries 1533 are populated before running on a possibly unpopulated stack. 1534 1535 - If the stack overflows into a guard page, something reasonable 1536 should happen. The definition of "reasonable" is flexible, but 1537 instantly rebooting without logging anything would be unfriendly. 1538 1539config VMAP_STACK 1540 default y 1541 bool "Use a virtually-mapped stack" 1542 depends on HAVE_ARCH_VMAP_STACK 1543 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1544 help 1545 Enable this if you want the use virtually-mapped kernel stacks 1546 with guard pages. This causes kernel stack overflows to be 1547 caught immediately rather than causing difficult-to-diagnose 1548 corruption. 1549 1550 To use this with software KASAN modes, the architecture must support 1551 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1552 must be enabled. 1553 1554config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1555 def_bool n 1556 help 1557 An arch should select this symbol if it can support kernel stack 1558 offset randomization with a call to add_random_kstack_offset() 1559 during syscall entry. Careful removal of -fstack-protector-strong and 1560 -fstack-protector should also be applied to the entry code and 1561 closely examined, as the artificial stack bump looks like an array 1562 to the compiler, so it will attempt to add canary checks regardless 1563 of the static branch state. 1564 1565config RANDOMIZE_KSTACK_OFFSET 1566 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1567 default y 1568 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1569 help 1570 The kernel stack offset can be randomized (after pt_regs) by 1571 roughly 5 bits of entropy, frustrating memory corruption 1572 attacks that depend on stack address determinism or 1573 cross-syscall address exposures. 1574 1575 The feature is controlled via the "randomize_kstack_offset=on/off" 1576 kernel boot param, and if turned off has zero overhead due to its use 1577 of static branches (see JUMP_LABEL). 1578 1579 If unsure, say Y. 1580 1581config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1582 bool "Default state of kernel stack offset randomization" 1583 depends on RANDOMIZE_KSTACK_OFFSET 1584 help 1585 Kernel stack offset randomization is controlled by kernel boot param 1586 "randomize_kstack_offset=on/off", and this config chooses the default 1587 boot state. 1588 1589config ARCH_OPTIONAL_KERNEL_RWX 1590 def_bool n 1591 1592config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1593 def_bool n 1594 1595config ARCH_HAS_STRICT_KERNEL_RWX 1596 def_bool n 1597 1598config STRICT_KERNEL_RWX 1599 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1600 depends on ARCH_HAS_STRICT_KERNEL_RWX 1601 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1602 help 1603 If this is set, kernel text and rodata memory will be made read-only, 1604 and non-text memory will be made non-executable. This provides 1605 protection against certain security exploits (e.g. executing the heap 1606 or modifying text) 1607 1608 These features are considered standard security practice these days. 1609 You should say Y here in almost all cases. 1610 1611config ARCH_HAS_STRICT_MODULE_RWX 1612 def_bool n 1613 1614config STRICT_MODULE_RWX 1615 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1616 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1617 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1618 help 1619 If this is set, module text and rodata memory will be made read-only, 1620 and non-text memory will be made non-executable. This provides 1621 protection against certain security exploits (e.g. writing to text) 1622 1623# select if the architecture provides an asm/dma-direct.h header 1624config ARCH_HAS_PHYS_TO_DMA 1625 bool 1626 1627config ARCH_HAS_CPU_RESCTRL 1628 bool 1629 help 1630 An architecture selects this option to indicate that the necessary 1631 hooks are provided to support the common memory system usage 1632 monitoring and control interfaces provided by the 'resctrl' 1633 filesystem (see RESCTRL_FS). 1634 1635config HAVE_ARCH_COMPILER_H 1636 bool 1637 help 1638 An architecture can select this if it provides an 1639 asm/compiler.h header that should be included after 1640 linux/compiler-*.h in order to override macro definitions that those 1641 headers generally provide. 1642 1643config HAVE_ARCH_LIBGCC_H 1644 bool 1645 help 1646 An architecture can select this if it provides an 1647 asm/libgcc.h header that should be included after 1648 linux/libgcc.h in order to override macro definitions that 1649 header generally provides. 1650 1651config HAVE_ARCH_PREL32_RELOCATIONS 1652 bool 1653 help 1654 May be selected by an architecture if it supports place-relative 1655 32-bit relocations, both in the toolchain and in the module loader, 1656 in which case relative references can be used in special sections 1657 for PCI fixup, initcalls etc which are only half the size on 64 bit 1658 architectures, and don't require runtime relocation on relocatable 1659 kernels. 1660 1661config ARCH_USE_MEMREMAP_PROT 1662 bool 1663 1664config LOCK_EVENT_COUNTS 1665 bool "Locking event counts collection" 1666 depends on DEBUG_FS 1667 help 1668 Enable light-weight counting of various locking related events 1669 in the system with minimal performance impact. This reduces 1670 the chance of application behavior change because of timing 1671 differences. The counts are reported via debugfs. 1672 1673# Select if the architecture has support for applying RELR relocations. 1674config ARCH_HAS_RELR 1675 bool 1676 1677config RELR 1678 bool "Use RELR relocation packing" 1679 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1680 default y 1681 help 1682 Store the kernel's dynamic relocations in the RELR relocation packing 1683 format. Requires a compatible linker (LLD supports this feature), as 1684 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1685 are compatible). 1686 1687config ARCH_HAS_MEM_ENCRYPT 1688 bool 1689 1690config ARCH_HAS_CC_PLATFORM 1691 bool 1692 1693config HAVE_SPARSE_SYSCALL_NR 1694 bool 1695 help 1696 An architecture should select this if its syscall numbering is sparse 1697 to save space. For example, MIPS architecture has a syscall array with 1698 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1699 related optimizations for a given architecture. 1700 1701config ARCH_HAS_VDSO_ARCH_DATA 1702 bool 1703 1704config ARCH_HAS_VDSO_TIME_DATA 1705 bool 1706 1707config HAVE_STATIC_CALL 1708 bool 1709 1710config HAVE_STATIC_CALL_INLINE 1711 bool 1712 depends on HAVE_STATIC_CALL 1713 select OBJTOOL 1714 1715config HAVE_PREEMPT_DYNAMIC 1716 bool 1717 1718config HAVE_PREEMPT_DYNAMIC_CALL 1719 bool 1720 depends on HAVE_STATIC_CALL 1721 select HAVE_PREEMPT_DYNAMIC 1722 help 1723 An architecture should select this if it can handle the preemption 1724 model being selected at boot time using static calls. 1725 1726 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1727 preemption function will be patched directly. 1728 1729 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1730 call to a preemption function will go through a trampoline, and the 1731 trampoline will be patched. 1732 1733 It is strongly advised to support inline static call to avoid any 1734 overhead. 1735 1736config HAVE_PREEMPT_DYNAMIC_KEY 1737 bool 1738 depends on HAVE_ARCH_JUMP_LABEL 1739 select HAVE_PREEMPT_DYNAMIC 1740 help 1741 An architecture should select this if it can handle the preemption 1742 model being selected at boot time using static keys. 1743 1744 Each preemption function will be given an early return based on a 1745 static key. This should have slightly lower overhead than non-inline 1746 static calls, as this effectively inlines each trampoline into the 1747 start of its callee. This may avoid redundant work, and may 1748 integrate better with CFI schemes. 1749 1750 This will have greater overhead than using inline static calls as 1751 the call to the preemption function cannot be entirely elided. 1752 1753config ARCH_WANT_LD_ORPHAN_WARN 1754 bool 1755 help 1756 An arch should select this symbol once all linker sections are explicitly 1757 included, size-asserted, or discarded in the linker scripts. This is 1758 important because we never want expected sections to be placed heuristically 1759 by the linker, since the locations of such sections can change between linker 1760 versions. 1761 1762config HAVE_ARCH_PFN_VALID 1763 bool 1764 1765config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1766 bool 1767 1768config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1769 bool 1770 1771config ARCH_SPLIT_ARG64 1772 bool 1773 help 1774 If a 32-bit architecture requires 64-bit arguments to be split into 1775 pairs of 32-bit arguments, select this option. 1776 1777config ARCH_HAS_ELFCORE_COMPAT 1778 bool 1779 1780config ARCH_HAS_PARANOID_L1D_FLUSH 1781 bool 1782 1783config ARCH_HAVE_TRACE_MMIO_ACCESS 1784 bool 1785 1786config DYNAMIC_SIGFRAME 1787 bool 1788 1789# Select, if arch has a named attribute group bound to NUMA device nodes. 1790config HAVE_ARCH_NODE_DEV_GROUP 1791 bool 1792 1793config ARCH_HAS_HW_PTE_YOUNG 1794 bool 1795 help 1796 Architectures that select this option are capable of setting the 1797 accessed bit in PTE entries when using them as part of linear address 1798 translations. Architectures that require runtime check should select 1799 this option and override arch_has_hw_pte_young(). 1800 1801config ARCH_HAS_NONLEAF_PMD_YOUNG 1802 bool 1803 help 1804 Architectures that select this option are capable of setting the 1805 accessed bit in non-leaf PMD entries when using them as part of linear 1806 address translations. Page table walkers that clear the accessed bit 1807 may use this capability to reduce their search space. 1808 1809config ARCH_HAS_KERNEL_FPU_SUPPORT 1810 bool 1811 help 1812 Architectures that select this option can run floating-point code in 1813 the kernel, as described in Documentation/core-api/floating-point.rst. 1814 1815config ARCH_VMLINUX_NEEDS_RELOCS 1816 bool 1817 help 1818 Whether the architecture needs vmlinux to be built with static 1819 relocations preserved. This is used by some architectures to 1820 construct bespoke relocation tables for KASLR. 1821 1822# Select if architecture uses the common generic TIF bits 1823config HAVE_GENERIC_TIF_BITS 1824 bool 1825 1826source "kernel/gcov/Kconfig" 1827 1828source "scripts/gcc-plugins/Kconfig" 1829 1830config FUNCTION_ALIGNMENT_4B 1831 bool 1832 1833config FUNCTION_ALIGNMENT_8B 1834 bool 1835 1836config FUNCTION_ALIGNMENT_16B 1837 bool 1838 1839config FUNCTION_ALIGNMENT_32B 1840 bool 1841 1842config FUNCTION_ALIGNMENT_64B 1843 bool 1844 1845config FUNCTION_ALIGNMENT 1846 int 1847 default 64 if FUNCTION_ALIGNMENT_64B 1848 default 32 if FUNCTION_ALIGNMENT_32B 1849 default 16 if FUNCTION_ALIGNMENT_16B 1850 default 8 if FUNCTION_ALIGNMENT_8B 1851 default 4 if FUNCTION_ALIGNMENT_4B 1852 default 0 1853 1854config CC_HAS_MIN_FUNCTION_ALIGNMENT 1855 # Detect availability of the GCC option -fmin-function-alignment which 1856 # guarantees minimal alignment for all functions, unlike 1857 # -falign-functions which the compiler ignores for cold functions. 1858 def_bool $(cc-option, -fmin-function-alignment=8) 1859 1860config CC_HAS_SANE_FUNCTION_ALIGNMENT 1861 # Set if the guaranteed alignment with -fmin-function-alignment is 1862 # available or extra care is required in the kernel. Clang provides 1863 # strict alignment always, even with -falign-functions. 1864 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1865 1866config ARCH_NEED_CMPXCHG_1_EMU 1867 bool 1868 1869config ARCH_WANTS_PRE_LINK_VMLINUX 1870 bool 1871 help 1872 An architecture can select this if it provides arch/<arch>/tools/Makefile 1873 with .arch.vmlinux.o target to be linked into vmlinux. 1874 1875config ARCH_HAS_CPU_ATTACK_VECTORS 1876 bool 1877 1878config HAVE_ARCH_GET_SECUREBOOT 1879 def_bool EFI 1880 1881endmenu 1882