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