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