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 # https://github.com/ClangBuiltLinux/linux/issues/1721 810 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 811 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 812 depends on !GCOV_KERNEL 813 help 814 The compiler and Kconfig options support building with Clang's 815 LTO. 816 817choice 818 prompt "Link Time Optimization (LTO)" 819 default LTO_NONE 820 help 821 This option enables Link Time Optimization (LTO), which allows the 822 compiler to optimize binaries globally. 823 824 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 825 so it's disabled by default. 826 827config LTO_NONE 828 bool "None" 829 help 830 Build the kernel normally, without Link Time Optimization (LTO). 831 832config LTO_CLANG_FULL 833 bool "Clang Full LTO (EXPERIMENTAL)" 834 depends on HAS_LTO_CLANG 835 depends on !COMPILE_TEST 836 select LTO_CLANG 837 help 838 This option enables Clang's full Link Time Optimization (LTO), which 839 allows the compiler to optimize the kernel globally. If you enable 840 this option, the compiler generates LLVM bitcode instead of ELF 841 object files, and the actual compilation from bitcode happens at 842 the LTO link step, which may take several minutes depending on the 843 kernel configuration. More information can be found from LLVM's 844 documentation: 845 846 https://llvm.org/docs/LinkTimeOptimization.html 847 848 During link time, this option can use a large amount of RAM, and 849 may take much longer than the ThinLTO option. 850 851config LTO_CLANG_THIN 852 bool "Clang ThinLTO (EXPERIMENTAL)" 853 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 854 select LTO_CLANG 855 help 856 This option enables Clang's ThinLTO, which allows for parallel 857 optimization and faster incremental compiles compared to the 858 CONFIG_LTO_CLANG_FULL option. More information can be found 859 from Clang's documentation: 860 861 https://clang.llvm.org/docs/ThinLTO.html 862 863 If unsure, say Y. 864endchoice 865 866config ARCH_SUPPORTS_AUTOFDO_CLANG 867 bool 868 869config AUTOFDO_CLANG 870 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 871 depends on ARCH_SUPPORTS_AUTOFDO_CLANG 872 depends on CC_IS_CLANG && CLANG_VERSION >= 170000 873 help 874 This option enables Clang’s AutoFDO build. When 875 an AutoFDO profile is specified in variable 876 CLANG_AUTOFDO_PROFILE during the build process, 877 Clang uses the profile to optimize the kernel. 878 879 If no profile is specified, AutoFDO options are 880 still passed to Clang to facilitate the collection 881 of perf data for creating an AutoFDO profile in 882 subsequent builds. 883 884 If unsure, say N. 885 886config ARCH_SUPPORTS_PROPELLER_CLANG 887 bool 888 889config PROPELLER_CLANG 890 bool "Enable Clang's Propeller build" 891 depends on ARCH_SUPPORTS_PROPELLER_CLANG 892 depends on CC_IS_CLANG && CLANG_VERSION >= 190000 893 help 894 This option enables Clang’s Propeller build. When the Propeller 895 profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX 896 during the build process, Clang uses the profiles to optimize 897 the kernel. 898 899 If no profile is specified, Propeller options are still passed 900 to Clang to facilitate the collection of perf data for creating 901 the Propeller profiles in subsequent builds. 902 903 If unsure, say N. 904 905config ARCH_SUPPORTS_CFI 906 bool 907 help 908 An architecture should select this option if it can support Kernel 909 Control-Flow Integrity (CFI) checking (-fsanitize=kcfi). 910 911config ARCH_USES_CFI_TRAPS 912 bool 913 help 914 An architecture should select this option if it requires the 915 .kcfi_traps section for KCFI trap handling. 916 917config ARCH_USES_CFI_GENERIC_LLVM_PASS 918 bool 919 help 920 An architecture should select this option if it uses the generic 921 KCFIPass in LLVM to expand kCFI bundles instead of architecture-specific 922 lowering. 923 924config CFI 925 bool "Use Kernel Control Flow Integrity (kCFI)" 926 default CFI_CLANG 927 depends on ARCH_SUPPORTS_CFI 928 depends on $(cc-option,-fsanitize=kcfi) 929 help 930 This option enables forward-edge Control Flow Integrity (CFI) 931 checking, where the compiler injects a runtime check to each 932 indirect function call to ensure the target is a valid function with 933 the correct static type. This restricts possible call targets and 934 makes it more difficult for an attacker to exploit bugs that allow 935 the modification of stored function pointers. More information can be 936 found from Clang's documentation: 937 938 https://clang.llvm.org/docs/ControlFlowIntegrity.html 939 940config CFI_CLANG 941 bool 942 transitional 943 help 944 Transitional config for CFI_CLANG to CFI migration. 945 946config CFI_ICALL_NORMALIZE_INTEGERS 947 bool "Normalize CFI tags for integers" 948 depends on CFI 949 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS 950 help 951 This option normalizes the CFI tags for integer types so that all 952 integer types of the same size and signedness receive the same CFI 953 tag. 954 955 The option is separate from CONFIG_RUST because it affects the ABI. 956 When working with build systems that care about the ABI, it is 957 convenient to be able to turn on this flag first, before Rust is 958 turned on. 959 960 This option is necessary for using CFI with Rust. If unsure, say N. 961 962config HAVE_CFI_ICALL_NORMALIZE_INTEGERS 963 def_bool y 964 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 965 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 966 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 967 968config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 969 def_bool y 970 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS 971 depends on ARM64 || X86_64 972 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 973 depends on RUSTC_LLVM_VERSION >= 190103 || \ 974 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 975 976config CFI_PERMISSIVE 977 bool "Use CFI in permissive mode" 978 depends on CFI 979 help 980 When selected, Control Flow Integrity (CFI) violations result in a 981 warning instead of a kernel panic. This option should only be used 982 for finding indirect call type mismatches during development. 983 984 If unsure, say N. 985 986config HAVE_ARCH_WITHIN_STACK_FRAMES 987 bool 988 help 989 An architecture should select this if it can walk the kernel stack 990 frames to determine if an object is part of either the arguments 991 or local variables (i.e. that it excludes saved return addresses, 992 and similar) by implementing an inline arch_within_stack_frames(), 993 which is used by CONFIG_HARDENED_USERCOPY. 994 995config HAVE_CONTEXT_TRACKING_USER 996 bool 997 help 998 Provide kernel/user boundaries probes necessary for subsystems 999 that need it, such as userspace RCU extended quiescent state. 1000 Syscalls need to be wrapped inside user_exit()-user_enter(), either 1001 optimized behind static key or through the slow path using TIF_NOHZ 1002 flag. Exceptions handlers must be wrapped as well. Irqs are already 1003 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 1004 handling on irq exit still need to be protected. 1005 1006config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 1007 bool 1008 help 1009 Architecture neither relies on exception_enter()/exception_exit() 1010 nor on schedule_user(). Also preempt_schedule_notrace() and 1011 preempt_schedule_irq() can't be called in a preemptible section 1012 while context tracking is CT_STATE_USER. This feature reflects a sane 1013 entry implementation where the following requirements are met on 1014 critical entry code, ie: before user_exit() or after user_enter(): 1015 1016 - Critical entry code isn't preemptible (or better yet: 1017 not interruptible). 1018 - No use of RCU read side critical sections, unless ct_nmi_enter() 1019 got called. 1020 - No use of instrumentation, unless instrumentation_begin() got 1021 called. 1022 1023config HAVE_TIF_NOHZ 1024 bool 1025 help 1026 Arch relies on TIF_NOHZ and syscall slow path to implement context 1027 tracking calls to user_enter()/user_exit(). 1028 1029config HAVE_VIRT_CPU_ACCOUNTING 1030 bool 1031 1032config HAVE_VIRT_CPU_ACCOUNTING_IDLE 1033 bool 1034 help 1035 Architecture has its own way to account idle CPU time and therefore 1036 doesn't implement vtime_account_idle(). 1037 1038config ARCH_HAS_SCALED_CPUTIME 1039 bool 1040 1041config HAVE_VIRT_CPU_ACCOUNTING_GEN 1042 bool 1043 default y if 64BIT 1044 help 1045 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 1046 Before enabling this option, arch code must be audited 1047 to ensure there are no races in concurrent read/write of 1048 cputime_t. For example, reading/writing 64-bit cputime_t on 1049 some 32-bit arches may require multiple accesses, so proper 1050 locking is needed to protect against concurrent accesses. 1051 1052config HAVE_IRQ_TIME_ACCOUNTING 1053 bool 1054 help 1055 Archs need to ensure they use a high enough resolution clock to 1056 support irq time accounting and then call enable_sched_clock_irqtime(). 1057 1058config HAVE_PV_STEAL_CLOCK_GEN 1059 bool 1060 1061config HAVE_MOVE_PUD 1062 bool 1063 help 1064 Architectures that select this are able to move page tables at the 1065 PUD level. If there are only 3 page table levels, the move effectively 1066 happens at the PGD level. 1067 1068config HAVE_MOVE_PMD 1069 bool 1070 help 1071 Archs that select this are able to move page tables at the PMD level. 1072 1073config HAVE_ARCH_TRANSPARENT_HUGEPAGE 1074 bool 1075 1076config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1077 bool 1078 1079config HAVE_ARCH_HUGE_VMAP 1080 bool 1081 1082# 1083# Archs that select this would be capable of PMD-sized vmaps (i.e., 1084# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 1085# must be used to enable allocations to use hugepages. 1086# 1087config HAVE_ARCH_HUGE_VMALLOC 1088 depends on HAVE_ARCH_HUGE_VMAP 1089 bool 1090 1091config ARCH_WANT_HUGE_PMD_SHARE 1092 bool 1093 1094# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1095# if there are no userspace memory management features that use it 1096config ARCH_WANT_KERNEL_PMD_MKWRITE 1097 bool 1098 1099config ARCH_WANT_PMD_MKWRITE 1100 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1101 1102config HAVE_ARCH_SOFT_DIRTY 1103 bool 1104 1105config HAVE_MOD_ARCH_SPECIFIC 1106 bool 1107 help 1108 The arch uses struct mod_arch_specific to store data. Many arches 1109 just need a simple module loader without arch specific data - those 1110 should not enable this. 1111 1112config MODULES_USE_ELF_RELA 1113 bool 1114 help 1115 Modules only use ELF RELA relocations. Modules with ELF REL 1116 relocations will give an error. 1117 1118config MODULES_USE_ELF_REL 1119 bool 1120 help 1121 Modules only use ELF REL relocations. Modules with ELF RELA 1122 relocations will give an error. 1123 1124config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1125 bool 1126 help 1127 For architectures like powerpc/32 which have constraints on module 1128 allocation and need to allocate module data outside of module area. 1129 1130config ARCH_WANTS_MODULES_TEXT_SECTIONS 1131 bool 1132 help 1133 For architectures like 32-bit parisc which require that functions in 1134 modules have to keep code in own text sections (-ffunction-sections) 1135 and to avoid merging all text into one big text section, 1136 1137config ARCH_WANTS_EXECMEM_LATE 1138 bool 1139 help 1140 For architectures that do not allocate executable memory early on 1141 boot, but rather require its initialization late when there is 1142 enough entropy for module space randomization, for instance 1143 arm64. 1144 1145config ARCH_HAS_EXECMEM_ROX 1146 bool 1147 depends on MMU && !HIGHMEM 1148 help 1149 For architectures that support allocations of executable memory 1150 with read-only execute permissions. Architecture must implement 1151 execmem_fill_trapping_insns() callback to enable this. 1152 1153config HAVE_IRQ_EXIT_ON_IRQ_STACK 1154 bool 1155 help 1156 Architecture doesn't only execute the irq handler on the irq stack 1157 but also irq_exit(). This way we can process softirqs on this irq 1158 stack instead of switching to a new one when we call __do_softirq() 1159 in the end of an hardirq. 1160 This spares a stack switch and improves cache usage on softirq 1161 processing. 1162 1163config HAVE_SOFTIRQ_ON_OWN_STACK 1164 bool 1165 help 1166 Architecture provides a function to run __do_softirq() on a 1167 separate stack. 1168 1169config SOFTIRQ_ON_OWN_STACK 1170 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1171 1172config ALTERNATE_USER_ADDRESS_SPACE 1173 bool 1174 help 1175 Architectures set this when the CPU uses separate address 1176 spaces for kernel and user space pointers. In this case, the 1177 access_ok() check on a __user pointer is skipped. 1178 1179config PGTABLE_LEVELS 1180 int 1181 default 2 1182 1183config ARCH_HAS_ELF_RANDOMIZE 1184 bool 1185 help 1186 An architecture supports choosing randomized locations for 1187 stack, mmap, brk, and ET_DYN. Defined functions: 1188 - arch_mmap_rnd() 1189 - arch_randomize_brk() 1190 1191config HAVE_ARCH_MMAP_RND_BITS 1192 bool 1193 help 1194 An arch should select this symbol if it supports setting a variable 1195 number of bits for use in establishing the base address for mmap 1196 allocations, has MMU enabled and provides values for both: 1197 - ARCH_MMAP_RND_BITS_MIN 1198 - ARCH_MMAP_RND_BITS_MAX 1199 1200config HAVE_EXIT_THREAD 1201 bool 1202 help 1203 An architecture implements exit_thread. 1204 1205config ARCH_MMAP_RND_BITS_MIN 1206 int 1207 1208config ARCH_MMAP_RND_BITS_MAX 1209 int 1210 1211config ARCH_MMAP_RND_BITS_DEFAULT 1212 int 1213 1214config ARCH_MMAP_RND_BITS 1215 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1216 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1217 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1218 default ARCH_MMAP_RND_BITS_MIN 1219 depends on HAVE_ARCH_MMAP_RND_BITS 1220 help 1221 This value can be used to select the number of bits to use to 1222 determine the random offset to the base address of vma regions 1223 resulting from mmap allocations. This value will be bounded 1224 by the architecture's minimum and maximum supported values. 1225 1226 This value can be changed after boot using the 1227 /proc/sys/vm/mmap_rnd_bits tunable 1228 1229config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1230 bool 1231 help 1232 An arch should select this symbol if it supports running applications 1233 in compatibility mode, supports setting a variable number of bits for 1234 use in establishing the base address for mmap allocations, has MMU 1235 enabled and provides values for both: 1236 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1237 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1238 1239config ARCH_MMAP_RND_COMPAT_BITS_MIN 1240 int 1241 1242config ARCH_MMAP_RND_COMPAT_BITS_MAX 1243 int 1244 1245config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1246 int 1247 1248config ARCH_MMAP_RND_COMPAT_BITS 1249 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1250 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1251 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1252 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1253 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1254 help 1255 This value can be used to select the number of bits to use to 1256 determine the random offset to the base address of vma regions 1257 resulting from mmap allocations for compatible applications This 1258 value will be bounded by the architecture's minimum and maximum 1259 supported values. 1260 1261 This value can be changed after boot using the 1262 /proc/sys/vm/mmap_rnd_compat_bits tunable 1263 1264config HAVE_ARCH_COMPAT_MMAP_BASES 1265 bool 1266 help 1267 This allows 64bit applications to invoke 32-bit mmap() syscall 1268 and vice-versa 32-bit applications to call 64-bit mmap(). 1269 Required for applications doing different bitness syscalls. 1270 1271config HAVE_PAGE_SIZE_4KB 1272 bool 1273 1274config HAVE_PAGE_SIZE_8KB 1275 bool 1276 1277config HAVE_PAGE_SIZE_16KB 1278 bool 1279 1280config HAVE_PAGE_SIZE_32KB 1281 bool 1282 1283config HAVE_PAGE_SIZE_64KB 1284 bool 1285 1286config HAVE_PAGE_SIZE_256KB 1287 bool 1288 1289choice 1290 prompt "MMU page size" 1291 1292config PAGE_SIZE_4KB 1293 bool "4KiB pages" 1294 depends on HAVE_PAGE_SIZE_4KB 1295 help 1296 This option select the standard 4KiB Linux page size and the only 1297 available option on many architectures. Using 4KiB page size will 1298 minimize memory consumption and is therefore recommended for low 1299 memory systems. 1300 Some software that is written for x86 systems makes incorrect 1301 assumptions about the page size and only runs on 4KiB pages. 1302 1303config PAGE_SIZE_8KB 1304 bool "8KiB pages" 1305 depends on HAVE_PAGE_SIZE_8KB 1306 help 1307 This option is the only supported page size on a few older 1308 processors, and can be slightly faster than 4KiB pages. 1309 1310config PAGE_SIZE_16KB 1311 bool "16KiB pages" 1312 depends on HAVE_PAGE_SIZE_16KB 1313 help 1314 This option is usually a good compromise between memory 1315 consumption and performance for typical desktop and server 1316 workloads, often saving a level of page table lookups compared 1317 to 4KB pages as well as reducing TLB pressure and overhead of 1318 per-page operations in the kernel at the expense of a larger 1319 page cache. 1320 1321config PAGE_SIZE_32KB 1322 bool "32KiB pages" 1323 depends on HAVE_PAGE_SIZE_32KB 1324 help 1325 Using 32KiB page size will result in slightly higher performance 1326 kernel at the price of higher memory consumption compared to 1327 16KiB pages. This option is available only on cnMIPS cores. 1328 Note that you will need a suitable Linux distribution to 1329 support this. 1330 1331config PAGE_SIZE_64KB 1332 bool "64KiB pages" 1333 depends on HAVE_PAGE_SIZE_64KB 1334 help 1335 Using 64KiB page size will result in slightly higher performance 1336 kernel at the price of much higher memory consumption compared to 1337 4KiB or 16KiB pages. 1338 This is not suitable for general-purpose workloads but the 1339 better performance may be worth the cost for certain types of 1340 supercomputing or database applications that work mostly with 1341 large in-memory data rather than small files. 1342 1343config PAGE_SIZE_256KB 1344 bool "256KiB pages" 1345 depends on HAVE_PAGE_SIZE_256KB 1346 help 1347 256KiB pages have little practical value due to their extreme 1348 memory usage. The kernel will only be able to run applications 1349 that have been compiled with '-zmax-page-size' set to 256KiB 1350 (the default is 64KiB or 4KiB on most architectures). 1351 1352endchoice 1353 1354config PAGE_SIZE_LESS_THAN_64KB 1355 def_bool y 1356 depends on !PAGE_SIZE_64KB 1357 depends on PAGE_SIZE_LESS_THAN_256KB 1358 1359config PAGE_SIZE_LESS_THAN_256KB 1360 def_bool y 1361 depends on !PAGE_SIZE_256KB 1362 1363config PAGE_SHIFT 1364 int 1365 default 12 if PAGE_SIZE_4KB 1366 default 13 if PAGE_SIZE_8KB 1367 default 14 if PAGE_SIZE_16KB 1368 default 15 if PAGE_SIZE_32KB 1369 default 16 if PAGE_SIZE_64KB 1370 default 18 if PAGE_SIZE_256KB 1371 1372# This allows to use a set of generic functions to determine mmap base 1373# address by giving priority to top-down scheme only if the process 1374# is not in legacy mode (compat task, unlimited stack size or 1375# sysctl_legacy_va_layout). 1376# Architecture that selects this option can provide its own version of: 1377# - STACK_RND_MASK 1378config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1379 bool 1380 depends on MMU 1381 select ARCH_HAS_ELF_RANDOMIZE 1382 1383config HAVE_OBJTOOL 1384 bool 1385 1386config HAVE_JUMP_LABEL_HACK 1387 bool 1388 1389config HAVE_NOINSTR_HACK 1390 bool 1391 1392config HAVE_NOINSTR_VALIDATION 1393 bool 1394 1395config HAVE_UACCESS_VALIDATION 1396 bool 1397 select OBJTOOL 1398 1399config HAVE_STACK_VALIDATION 1400 bool 1401 help 1402 Architecture supports objtool compile-time frame pointer rule 1403 validation. 1404 1405config HAVE_RELIABLE_STACKTRACE 1406 bool 1407 help 1408 Architecture has either save_stack_trace_tsk_reliable() or 1409 arch_stack_walk_reliable() function which only returns a stack trace 1410 if it can guarantee the trace is reliable. 1411 1412config HAVE_ARCH_HASH 1413 bool 1414 default n 1415 help 1416 If this is set, the architecture provides an <asm/hash.h> 1417 file which provides platform-specific implementations of some 1418 functions in <linux/hash.h> or fs/namei.c. 1419 1420config HAVE_ARCH_NVRAM_OPS 1421 bool 1422 1423config ISA_BUS_API 1424 def_bool ISA 1425 1426# 1427# ABI hall of shame 1428# 1429config CLONE_BACKWARDS 1430 bool 1431 help 1432 Architecture has tls passed as the 4th argument of clone(2), 1433 not the 5th one. 1434 1435config CLONE_BACKWARDS2 1436 bool 1437 help 1438 Architecture has the first two arguments of clone(2) swapped. 1439 1440config CLONE_BACKWARDS3 1441 bool 1442 help 1443 Architecture has tls passed as the 3rd argument of clone(2), 1444 not the 5th one. 1445 1446config ODD_RT_SIGACTION 1447 bool 1448 help 1449 Architecture has unusual rt_sigaction(2) arguments 1450 1451config OLD_SIGSUSPEND 1452 bool 1453 help 1454 Architecture has old sigsuspend(2) syscall, of one-argument variety 1455 1456config OLD_SIGSUSPEND3 1457 bool 1458 help 1459 Even weirder antique ABI - three-argument sigsuspend(2) 1460 1461config OLD_SIGACTION 1462 bool 1463 help 1464 Architecture has old sigaction(2) syscall. Nope, not the same 1465 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1466 but fairly different variant of sigaction(2), thanks to OSF/1 1467 compatibility... 1468 1469config COMPAT_OLD_SIGACTION 1470 bool 1471 1472config COMPAT_32BIT_TIME 1473 bool "Provide system calls for 32-bit time_t" 1474 default !64BIT || COMPAT 1475 help 1476 This enables 32 bit time_t support in addition to 64 bit time_t support. 1477 This is relevant on all 32-bit architectures, and 64-bit architectures 1478 as part of compat syscall handling. 1479 1480config ARCH_NO_PREEMPT 1481 bool 1482 1483config ARCH_SUPPORTS_RT 1484 bool 1485 1486config CPU_NO_EFFICIENT_FFS 1487 def_bool n 1488 1489config HAVE_ARCH_VMAP_STACK 1490 def_bool n 1491 help 1492 An arch should select this symbol if it can support kernel stacks 1493 in vmalloc space. This means: 1494 1495 - vmalloc space must be large enough to hold many kernel stacks. 1496 This may rule out many 32-bit architectures. 1497 1498 - Stacks in vmalloc space need to work reliably. For example, if 1499 vmap page tables are created on demand, either this mechanism 1500 needs to work while the stack points to a virtual address with 1501 unpopulated page tables or arch code (switch_to() and switch_mm(), 1502 most likely) needs to ensure that the stack's page table entries 1503 are populated before running on a possibly unpopulated stack. 1504 1505 - If the stack overflows into a guard page, something reasonable 1506 should happen. The definition of "reasonable" is flexible, but 1507 instantly rebooting without logging anything would be unfriendly. 1508 1509config VMAP_STACK 1510 default y 1511 bool "Use a virtually-mapped stack" 1512 depends on HAVE_ARCH_VMAP_STACK 1513 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1514 help 1515 Enable this if you want the use virtually-mapped kernel stacks 1516 with guard pages. This causes kernel stack overflows to be 1517 caught immediately rather than causing difficult-to-diagnose 1518 corruption. 1519 1520 To use this with software KASAN modes, the architecture must support 1521 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1522 must be enabled. 1523 1524config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1525 def_bool n 1526 help 1527 An arch should select this symbol if it can support kernel stack 1528 offset randomization with a call to add_random_kstack_offset() 1529 during syscall entry. Careful removal of -fstack-protector-strong and 1530 -fstack-protector should also be applied to the entry code and 1531 closely examined, as the artificial stack bump looks like an array 1532 to the compiler, so it will attempt to add canary checks regardless 1533 of the static branch state. 1534 1535config RANDOMIZE_KSTACK_OFFSET 1536 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1537 default y 1538 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1539 help 1540 The kernel stack offset can be randomized (after pt_regs) by 1541 roughly 5 bits of entropy, frustrating memory corruption 1542 attacks that depend on stack address determinism or 1543 cross-syscall address exposures. 1544 1545 The feature is controlled via the "randomize_kstack_offset=on/off" 1546 kernel boot param, and if turned off has zero overhead due to its use 1547 of static branches (see JUMP_LABEL). 1548 1549 If unsure, say Y. 1550 1551config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1552 bool "Default state of kernel stack offset randomization" 1553 depends on RANDOMIZE_KSTACK_OFFSET 1554 help 1555 Kernel stack offset randomization is controlled by kernel boot param 1556 "randomize_kstack_offset=on/off", and this config chooses the default 1557 boot state. 1558 1559config ARCH_OPTIONAL_KERNEL_RWX 1560 def_bool n 1561 1562config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1563 def_bool n 1564 1565config ARCH_HAS_STRICT_KERNEL_RWX 1566 def_bool n 1567 1568config STRICT_KERNEL_RWX 1569 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1570 depends on ARCH_HAS_STRICT_KERNEL_RWX 1571 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1572 help 1573 If this is set, kernel text and rodata memory will be made read-only, 1574 and non-text memory will be made non-executable. This provides 1575 protection against certain security exploits (e.g. executing the heap 1576 or modifying text) 1577 1578 These features are considered standard security practice these days. 1579 You should say Y here in almost all cases. 1580 1581config ARCH_HAS_STRICT_MODULE_RWX 1582 def_bool n 1583 1584config STRICT_MODULE_RWX 1585 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1586 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1587 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1588 help 1589 If this is set, module 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. writing to text) 1592 1593# select if the architecture provides an asm/dma-direct.h header 1594config ARCH_HAS_PHYS_TO_DMA 1595 bool 1596 1597config ARCH_HAS_CPU_RESCTRL 1598 bool 1599 help 1600 An architecture selects this option to indicate that the necessary 1601 hooks are provided to support the common memory system usage 1602 monitoring and control interfaces provided by the 'resctrl' 1603 filesystem (see RESCTRL_FS). 1604 1605config HAVE_ARCH_COMPILER_H 1606 bool 1607 help 1608 An architecture can select this if it provides an 1609 asm/compiler.h header that should be included after 1610 linux/compiler-*.h in order to override macro definitions that those 1611 headers generally provide. 1612 1613config HAVE_ARCH_LIBGCC_H 1614 bool 1615 help 1616 An architecture can select this if it provides an 1617 asm/libgcc.h header that should be included after 1618 linux/libgcc.h in order to override macro definitions that 1619 header generally provides. 1620 1621config HAVE_ARCH_PREL32_RELOCATIONS 1622 bool 1623 help 1624 May be selected by an architecture if it supports place-relative 1625 32-bit relocations, both in the toolchain and in the module loader, 1626 in which case relative references can be used in special sections 1627 for PCI fixup, initcalls etc which are only half the size on 64 bit 1628 architectures, and don't require runtime relocation on relocatable 1629 kernels. 1630 1631config ARCH_USE_MEMREMAP_PROT 1632 bool 1633 1634config LOCK_EVENT_COUNTS 1635 bool "Locking event counts collection" 1636 depends on DEBUG_FS 1637 help 1638 Enable light-weight counting of various locking related events 1639 in the system with minimal performance impact. This reduces 1640 the chance of application behavior change because of timing 1641 differences. The counts are reported via debugfs. 1642 1643# Select if the architecture has support for applying RELR relocations. 1644config ARCH_HAS_RELR 1645 bool 1646 1647config RELR 1648 bool "Use RELR relocation packing" 1649 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1650 default y 1651 help 1652 Store the kernel's dynamic relocations in the RELR relocation packing 1653 format. Requires a compatible linker (LLD supports this feature), as 1654 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1655 are compatible). 1656 1657config ARCH_HAS_MEM_ENCRYPT 1658 bool 1659 1660config ARCH_HAS_CC_PLATFORM 1661 bool 1662 1663config HAVE_SPARSE_SYSCALL_NR 1664 bool 1665 help 1666 An architecture should select this if its syscall numbering is sparse 1667 to save space. For example, MIPS architecture has a syscall array with 1668 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1669 related optimizations for a given architecture. 1670 1671config ARCH_HAS_VDSO_ARCH_DATA 1672 depends on HAVE_GENERIC_VDSO 1673 bool 1674 1675config ARCH_HAS_VDSO_TIME_DATA 1676 bool 1677 1678config HAVE_STATIC_CALL 1679 bool 1680 1681config HAVE_STATIC_CALL_INLINE 1682 bool 1683 depends on HAVE_STATIC_CALL 1684 select OBJTOOL 1685 1686config HAVE_PREEMPT_DYNAMIC 1687 bool 1688 1689config HAVE_PREEMPT_DYNAMIC_CALL 1690 bool 1691 depends on HAVE_STATIC_CALL 1692 select HAVE_PREEMPT_DYNAMIC 1693 help 1694 An architecture should select this if it can handle the preemption 1695 model being selected at boot time using static calls. 1696 1697 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1698 preemption function will be patched directly. 1699 1700 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1701 call to a preemption function will go through a trampoline, and the 1702 trampoline will be patched. 1703 1704 It is strongly advised to support inline static call to avoid any 1705 overhead. 1706 1707config HAVE_PREEMPT_DYNAMIC_KEY 1708 bool 1709 depends on HAVE_ARCH_JUMP_LABEL 1710 select HAVE_PREEMPT_DYNAMIC 1711 help 1712 An architecture should select this if it can handle the preemption 1713 model being selected at boot time using static keys. 1714 1715 Each preemption function will be given an early return based on a 1716 static key. This should have slightly lower overhead than non-inline 1717 static calls, as this effectively inlines each trampoline into the 1718 start of its callee. This may avoid redundant work, and may 1719 integrate better with CFI schemes. 1720 1721 This will have greater overhead than using inline static calls as 1722 the call to the preemption function cannot be entirely elided. 1723 1724config ARCH_WANT_LD_ORPHAN_WARN 1725 bool 1726 help 1727 An arch should select this symbol once all linker sections are explicitly 1728 included, size-asserted, or discarded in the linker scripts. This is 1729 important because we never want expected sections to be placed heuristically 1730 by the linker, since the locations of such sections can change between linker 1731 versions. 1732 1733config HAVE_ARCH_PFN_VALID 1734 bool 1735 1736config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1737 bool 1738 1739config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1740 bool 1741 1742config ARCH_SPLIT_ARG64 1743 bool 1744 help 1745 If a 32-bit architecture requires 64-bit arguments to be split into 1746 pairs of 32-bit arguments, select this option. 1747 1748config ARCH_HAS_ELFCORE_COMPAT 1749 bool 1750 1751config ARCH_HAS_PARANOID_L1D_FLUSH 1752 bool 1753 1754config ARCH_HAVE_TRACE_MMIO_ACCESS 1755 bool 1756 1757config DYNAMIC_SIGFRAME 1758 bool 1759 1760# Select, if arch has a named attribute group bound to NUMA device nodes. 1761config HAVE_ARCH_NODE_DEV_GROUP 1762 bool 1763 1764config ARCH_HAS_HW_PTE_YOUNG 1765 bool 1766 help 1767 Architectures that select this option are capable of setting the 1768 accessed bit in PTE entries when using them as part of linear address 1769 translations. Architectures that require runtime check should select 1770 this option and override arch_has_hw_pte_young(). 1771 1772config ARCH_HAS_NONLEAF_PMD_YOUNG 1773 bool 1774 help 1775 Architectures that select this option are capable of setting the 1776 accessed bit in non-leaf PMD entries when using them as part of linear 1777 address translations. Page table walkers that clear the accessed bit 1778 may use this capability to reduce their search space. 1779 1780config ARCH_HAS_KERNEL_FPU_SUPPORT 1781 bool 1782 help 1783 Architectures that select this option can run floating-point code in 1784 the kernel, as described in Documentation/core-api/floating-point.rst. 1785 1786config ARCH_VMLINUX_NEEDS_RELOCS 1787 bool 1788 help 1789 Whether the architecture needs vmlinux to be built with static 1790 relocations preserved. This is used by some architectures to 1791 construct bespoke relocation tables for KASLR. 1792 1793# Select if architecture uses the common generic TIF bits 1794config HAVE_GENERIC_TIF_BITS 1795 bool 1796 1797source "kernel/gcov/Kconfig" 1798 1799source "scripts/gcc-plugins/Kconfig" 1800 1801config FUNCTION_ALIGNMENT_4B 1802 bool 1803 1804config FUNCTION_ALIGNMENT_8B 1805 bool 1806 1807config FUNCTION_ALIGNMENT_16B 1808 bool 1809 1810config FUNCTION_ALIGNMENT_32B 1811 bool 1812 1813config FUNCTION_ALIGNMENT_64B 1814 bool 1815 1816config FUNCTION_ALIGNMENT 1817 int 1818 default 64 if FUNCTION_ALIGNMENT_64B 1819 default 32 if FUNCTION_ALIGNMENT_32B 1820 default 16 if FUNCTION_ALIGNMENT_16B 1821 default 8 if FUNCTION_ALIGNMENT_8B 1822 default 4 if FUNCTION_ALIGNMENT_4B 1823 default 0 1824 1825config CC_HAS_MIN_FUNCTION_ALIGNMENT 1826 # Detect availability of the GCC option -fmin-function-alignment which 1827 # guarantees minimal alignment for all functions, unlike 1828 # -falign-functions which the compiler ignores for cold functions. 1829 def_bool $(cc-option, -fmin-function-alignment=8) 1830 1831config CC_HAS_SANE_FUNCTION_ALIGNMENT 1832 # Set if the guaranteed alignment with -fmin-function-alignment is 1833 # available or extra care is required in the kernel. Clang provides 1834 # strict alignment always, even with -falign-functions. 1835 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1836 1837config ARCH_NEED_CMPXCHG_1_EMU 1838 bool 1839 1840config ARCH_WANTS_PRE_LINK_VMLINUX 1841 bool 1842 help 1843 An architecture can select this if it provides arch/<arch>/tools/Makefile 1844 with .arch.vmlinux.o target to be linked into vmlinux. 1845 1846config ARCH_HAS_CPU_ATTACK_VECTORS 1847 bool 1848 1849config HAVE_ARCH_GET_SECUREBOOT 1850 def_bool EFI 1851 1852endmenu 1853