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