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 44# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 45config HOTPLUG_CORE_SYNC 46 bool 47 48# Basic CPU dead synchronization selected by architecture 49config HOTPLUG_CORE_SYNC_DEAD 50 bool 51 select HOTPLUG_CORE_SYNC 52 53# Full CPU synchronization with alive state selected by architecture 54config HOTPLUG_CORE_SYNC_FULL 55 bool 56 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 57 select HOTPLUG_CORE_SYNC 58 59config HOTPLUG_SPLIT_STARTUP 60 bool 61 select HOTPLUG_CORE_SYNC_FULL 62 63config HOTPLUG_PARALLEL 64 bool 65 select HOTPLUG_SPLIT_STARTUP 66 67config GENERIC_IRQ_ENTRY 68 bool 69 70config GENERIC_SYSCALL 71 bool 72 depends on GENERIC_IRQ_ENTRY 73 74config GENERIC_ENTRY 75 bool 76 select GENERIC_IRQ_ENTRY 77 select GENERIC_SYSCALL 78 79config KPROBES 80 bool "Kprobes" 81 depends on HAVE_KPROBES 82 select KALLSYMS 83 select EXECMEM 84 select NEED_TASKS_RCU 85 help 86 Kprobes allows you to trap at almost any kernel address and 87 execute a callback function. register_kprobe() establishes 88 a probepoint and specifies the callback. Kprobes is useful 89 for kernel debugging, non-intrusive instrumentation and testing. 90 If in doubt, say "N". 91 92config JUMP_LABEL 93 bool "Optimize very unlikely/likely branches" 94 depends on HAVE_ARCH_JUMP_LABEL 95 select OBJTOOL if HAVE_JUMP_LABEL_HACK 96 help 97 This option enables a transparent branch optimization that 98 makes certain almost-always-true or almost-always-false branch 99 conditions even cheaper to execute within the kernel. 100 101 Certain performance-sensitive kernel code, such as trace points, 102 scheduler functionality, networking code and KVM have such 103 branches and include support for this optimization technique. 104 105 If it is detected that the compiler has support for "asm goto", 106 the kernel will compile such branches with just a nop 107 instruction. When the condition flag is toggled to true, the 108 nop will be converted to a jump instruction to execute the 109 conditional block of instructions. 110 111 This technique lowers overhead and stress on the branch prediction 112 of the processor and generally makes the kernel faster. The update 113 of the condition is slower, but those are always very rare. 114 115 ( On 32-bit x86, the necessary options added to the compiler 116 flags may increase the size of the kernel slightly. ) 117 118config STATIC_KEYS_SELFTEST 119 bool "Static key selftest" 120 depends on JUMP_LABEL 121 help 122 Boot time self-test of the branch patching code. 123 124config STATIC_CALL_SELFTEST 125 bool "Static call selftest" 126 depends on HAVE_STATIC_CALL 127 help 128 Boot time self-test of the call patching code. 129 130config OPTPROBES 131 def_bool y 132 depends on KPROBES && HAVE_OPTPROBES 133 select NEED_TASKS_RCU 134 135config KPROBES_ON_FTRACE 136 def_bool y 137 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 138 depends on DYNAMIC_FTRACE_WITH_REGS 139 help 140 If function tracer is enabled and the arch supports full 141 passing of pt_regs to function tracing, then kprobes can 142 optimize on top of function tracing. 143 144config UPROBES 145 def_bool n 146 depends on ARCH_SUPPORTS_UPROBES 147 select TASKS_TRACE_RCU 148 help 149 Uprobes is the user-space counterpart to kprobes: they 150 enable instrumentation applications (such as 'perf probe') 151 to establish unintrusive probes in user-space binaries and 152 libraries, by executing handler functions when the probes 153 are hit by user-space applications. 154 155 ( These probes come in the form of single-byte breakpoints, 156 managed by the kernel and kept transparent to the probed 157 application. ) 158 159config HAVE_64BIT_ALIGNED_ACCESS 160 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 161 help 162 Some architectures require 64 bit accesses to be 64 bit 163 aligned, which also requires structs containing 64 bit values 164 to be 64 bit aligned too. This includes some 32 bit 165 architectures which can do 64 bit accesses, as well as 64 bit 166 architectures without unaligned access. 167 168 This symbol should be selected by an architecture if 64 bit 169 accesses are required to be 64 bit aligned in this way even 170 though it is not a 64 bit architecture. 171 172 See Documentation/core-api/unaligned-memory-access.rst for 173 more information on the topic of unaligned memory accesses. 174 175config HAVE_EFFICIENT_UNALIGNED_ACCESS 176 bool 177 help 178 Some architectures are unable to perform unaligned accesses 179 without the use of get_unaligned/put_unaligned. Others are 180 unable to perform such accesses efficiently (e.g. trap on 181 unaligned access and require fixing it up in the exception 182 handler.) 183 184 This symbol should be selected by an architecture if it can 185 perform unaligned accesses efficiently to allow different 186 code paths to be selected for these cases. Some network 187 drivers, for example, could opt to not fix up alignment 188 problems with received packets if doing so would not help 189 much. 190 191 See Documentation/core-api/unaligned-memory-access.rst for more 192 information on the topic of unaligned memory accesses. 193 194config ARCH_USE_BUILTIN_BSWAP 195 bool 196 help 197 Modern versions of GCC (since 4.4) have builtin functions 198 for handling byte-swapping. Using these, instead of the old 199 inline assembler that the architecture code provides in the 200 __arch_bswapXX() macros, allows the compiler to see what's 201 happening and offers more opportunity for optimisation. In 202 particular, the compiler will be able to combine the byteswap 203 with a nearby load or store and use load-and-swap or 204 store-and-swap instructions if the architecture has them. It 205 should almost *never* result in code which is worse than the 206 hand-coded assembler in <asm/swab.h>. But just in case it 207 does, the use of the builtins is optional. 208 209 Any architecture with load-and-swap or store-and-swap 210 instructions should set this. And it shouldn't hurt to set it 211 on architectures that don't have such instructions. 212 213config KRETPROBES 214 def_bool y 215 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 216 217config KRETPROBE_ON_RETHOOK 218 def_bool y 219 depends on HAVE_RETHOOK 220 depends on KRETPROBES 221 select RETHOOK 222 223config USER_RETURN_NOTIFIER 224 bool 225 depends on HAVE_USER_RETURN_NOTIFIER 226 help 227 Provide a kernel-internal notification when a cpu is about to 228 switch to user mode. 229 230config HAVE_IOREMAP_PROT 231 bool 232 233config HAVE_KPROBES 234 bool 235 236config HAVE_KRETPROBES 237 bool 238 239config HAVE_OPTPROBES 240 bool 241 242config HAVE_KPROBES_ON_FTRACE 243 bool 244 245config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 246 bool 247 help 248 Since kretprobes modifies return address on the stack, the 249 stacktrace may see the kretprobe trampoline address instead 250 of correct one. If the architecture stacktrace code and 251 unwinder can adjust such entries, select this configuration. 252 253config HAVE_FUNCTION_ERROR_INJECTION 254 bool 255 256config HAVE_NMI 257 bool 258 259config HAVE_FUNCTION_DESCRIPTORS 260 bool 261 262config TRACE_IRQFLAGS_SUPPORT 263 bool 264 265config TRACE_IRQFLAGS_NMI_SUPPORT 266 bool 267 268# 269# An arch should select this if it provides all these things: 270# 271# task_pt_regs() in asm/processor.h or asm/ptrace.h 272# arch_has_single_step() if there is hardware single-step support 273# arch_has_block_step() if there is hardware block-step support 274# asm/syscall.h supplying asm-generic/syscall.h interface 275# linux/regset.h user_regset interfaces 276# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 277# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 278# TIF_NOTIFY_RESUME calls resume_user_mode_work() 279# 280config HAVE_ARCH_TRACEHOOK 281 bool 282 283config HAVE_DMA_CONTIGUOUS 284 bool 285 286config GENERIC_SMP_IDLE_THREAD 287 bool 288 289config GENERIC_IDLE_POLL_SETUP 290 bool 291 292config ARCH_HAS_FORTIFY_SOURCE 293 bool 294 help 295 An architecture should select this when it can successfully 296 build and run with CONFIG_FORTIFY_SOURCE. 297 298# 299# Select if the arch provides a historic keepinit alias for the retain_initrd 300# command line option 301# 302config ARCH_HAS_KEEPINITRD 303 bool 304 305# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 306config ARCH_HAS_SET_MEMORY 307 bool 308 309# Select if arch has all set_direct_map_invalid/default() functions 310config ARCH_HAS_SET_DIRECT_MAP 311 bool 312 313# 314# Select if the architecture provides the arch_dma_set_uncached symbol to 315# either provide an uncached segment alias for a DMA allocation, or 316# to remap the page tables in place. 317# 318config ARCH_HAS_DMA_SET_UNCACHED 319 bool 320 321# 322# Select if the architectures provides the arch_dma_clear_uncached symbol 323# to undo an in-place page table remap for uncached access. 324# 325config ARCH_HAS_DMA_CLEAR_UNCACHED 326 bool 327 328config ARCH_HAS_CPU_FINALIZE_INIT 329 bool 330 331# The architecture has a per-task state that includes the mm's PASID 332config ARCH_HAS_CPU_PASID 333 bool 334 select IOMMU_MM_DATA 335 336config HAVE_ARCH_THREAD_STRUCT_WHITELIST 337 bool 338 help 339 An architecture should select this to provide hardened usercopy 340 knowledge about what region of the thread_struct should be 341 whitelisted for copying to userspace. Normally this is only the 342 FPU registers. Specifically, arch_thread_struct_whitelist() 343 should be implemented. Without this, the entire thread_struct 344 field in task_struct will be left whitelisted. 345 346# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 347config ARCH_WANTS_DYNAMIC_TASK_STRUCT 348 bool 349 350config ARCH_WANTS_NO_INSTR 351 bool 352 help 353 An architecture should select this if the noinstr macro is being used on 354 functions to denote that the toolchain should avoid instrumenting such 355 functions and is required for correctness. 356 357config ARCH_32BIT_OFF_T 358 bool 359 depends on !64BIT 360 help 361 All new 32-bit architectures should have 64-bit off_t type on 362 userspace side which corresponds to the loff_t kernel type. This 363 is the requirement for modern ABIs. Some existing architectures 364 still support 32-bit off_t. This option is enabled for all such 365 architectures explicitly. 366 367# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 368config ARCH_32BIT_USTAT_F_TINODE 369 bool 370 371config HAVE_ASM_MODVERSIONS 372 bool 373 help 374 This symbol should be selected by an architecture if it provides 375 <asm/asm-prototypes.h> to support the module versioning for symbols 376 exported from assembly code. 377 378config HAVE_REGS_AND_STACK_ACCESS_API 379 bool 380 help 381 This symbol should be selected by an architecture if it supports 382 the API needed to access registers and stack entries from pt_regs, 383 declared in asm/ptrace.h 384 For example the kprobes-based event tracer needs this API. 385 386config HAVE_RSEQ 387 bool 388 depends on HAVE_REGS_AND_STACK_ACCESS_API 389 help 390 This symbol should be selected by an architecture if it 391 supports an implementation of restartable sequences. 392 393config HAVE_RUST 394 bool 395 help 396 This symbol should be selected by an architecture if it 397 supports Rust. 398 399config HAVE_FUNCTION_ARG_ACCESS_API 400 bool 401 help 402 This symbol should be selected by an architecture if it supports 403 the API needed to access function arguments from pt_regs, 404 declared in asm/ptrace.h 405 406config HAVE_HW_BREAKPOINT 407 bool 408 depends on PERF_EVENTS 409 410config HAVE_MIXED_BREAKPOINTS_REGS 411 bool 412 depends on HAVE_HW_BREAKPOINT 413 help 414 Depending on the arch implementation of hardware breakpoints, 415 some of them have separate registers for data and instruction 416 breakpoints addresses, others have mixed registers to store 417 them but define the access type in a control register. 418 Select this option if your arch implements breakpoints under the 419 latter fashion. 420 421config HAVE_USER_RETURN_NOTIFIER 422 bool 423 424config HAVE_PERF_EVENTS_NMI 425 bool 426 help 427 System hardware can generate an NMI using the perf event 428 subsystem. Also has support for calculating CPU cycle events 429 to determine how many clock cycles in a given period. 430 431config HAVE_HARDLOCKUP_DETECTOR_PERF 432 bool 433 depends on HAVE_PERF_EVENTS_NMI 434 help 435 The arch chooses to use the generic perf-NMI-based hardlockup 436 detector. Must define HAVE_PERF_EVENTS_NMI. 437 438config HAVE_HARDLOCKUP_DETECTOR_ARCH 439 bool 440 help 441 The arch provides its own hardlockup detector implementation instead 442 of the generic ones. 443 444 It uses the same command line parameters, and sysctl interface, 445 as the generic hardlockup detectors. 446 447config UNWIND_USER 448 bool 449 450config HAVE_UNWIND_USER_FP 451 bool 452 select UNWIND_USER 453 454config HAVE_PERF_REGS 455 bool 456 help 457 Support selective register dumps for perf events. This includes 458 bit-mapping of each registers and a unique architecture id. 459 460config HAVE_PERF_USER_STACK_DUMP 461 bool 462 help 463 Support user stack dumps for perf event samples. This needs 464 access to the user stack pointer which is not unified across 465 architectures. 466 467config HAVE_ARCH_JUMP_LABEL 468 bool 469 470config HAVE_ARCH_JUMP_LABEL_RELATIVE 471 bool 472 473config MMU_GATHER_TABLE_FREE 474 bool 475 476config MMU_GATHER_RCU_TABLE_FREE 477 bool 478 select MMU_GATHER_TABLE_FREE 479 480config MMU_GATHER_PAGE_SIZE 481 bool 482 483config MMU_GATHER_NO_RANGE 484 bool 485 select MMU_GATHER_MERGE_VMAS 486 487config MMU_GATHER_NO_FLUSH_CACHE 488 bool 489 490config MMU_GATHER_MERGE_VMAS 491 bool 492 493config MMU_GATHER_NO_GATHER 494 bool 495 depends on MMU_GATHER_TABLE_FREE 496 497config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 498 bool 499 help 500 Temporary select until all architectures can be converted to have 501 irqs disabled over activate_mm. Architectures that do IPI based TLB 502 shootdowns should enable this. 503 504# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 505# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 506# to/from kernel threads when the same mm is running on a lot of CPUs (a large 507# multi-threaded application), by reducing contention on the mm refcount. 508# 509# This can be disabled if the architecture ensures no CPUs are using an mm as a 510# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 511# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 512# final exit(2) TLB flush, for example. 513# 514# To implement this, an arch *must*: 515# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 516# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 517# converted already). 518config MMU_LAZY_TLB_REFCOUNT 519 def_bool y 520 depends on !MMU_LAZY_TLB_SHOOTDOWN 521 522# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 523# mm as a lazy tlb beyond its last reference count, by shooting down these 524# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 525# be using the mm as a lazy tlb, so that they may switch themselves to using 526# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 527# may be using mm as a lazy tlb mm. 528# 529# To implement this, an arch *must*: 530# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 531# at least all possible CPUs in which the mm is lazy. 532# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 533config MMU_LAZY_TLB_SHOOTDOWN 534 bool 535 536config ARCH_HAVE_NMI_SAFE_CMPXCHG 537 bool 538 539config ARCH_HAVE_EXTRA_ELF_NOTES 540 bool 541 help 542 An architecture should select this in order to enable adding an 543 arch-specific ELF note section to core files. It must provide two 544 functions: elf_coredump_extra_notes_size() and 545 elf_coredump_extra_notes_write() which are invoked by the ELF core 546 dumper. 547 548config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 549 bool 550 551config HAVE_ALIGNED_STRUCT_PAGE 552 bool 553 help 554 This makes sure that struct pages are double word aligned and that 555 e.g. the SLUB allocator can perform double word atomic operations 556 on a struct page for better performance. However selecting this 557 might increase the size of a struct page by a word. 558 559config HAVE_CMPXCHG_LOCAL 560 bool 561 562config HAVE_CMPXCHG_DOUBLE 563 bool 564 565config ARCH_WEAK_RELEASE_ACQUIRE 566 bool 567 568config ARCH_WANT_IPC_PARSE_VERSION 569 bool 570 571config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 572 bool 573 574config ARCH_WANT_OLD_COMPAT_IPC 575 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 576 bool 577 578config HAVE_ARCH_SECCOMP 579 bool 580 help 581 An arch should select this symbol to support seccomp mode 1 (the fixed 582 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 583 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 584 - __NR_seccomp_read_32 585 - __NR_seccomp_write_32 586 - __NR_seccomp_exit_32 587 - __NR_seccomp_sigreturn_32 588 589config HAVE_ARCH_SECCOMP_FILTER 590 bool 591 select HAVE_ARCH_SECCOMP 592 help 593 An arch should select this symbol if it provides all of these things: 594 - all the requirements for HAVE_ARCH_SECCOMP 595 - syscall_get_arch() 596 - syscall_get_arguments() 597 - syscall_rollback() 598 - syscall_set_return_value() 599 - SIGSYS siginfo_t support 600 - secure_computing is called from a ptrace_event()-safe context 601 - secure_computing return value is checked and a return value of -1 602 results in the system call being skipped immediately. 603 - seccomp syscall wired up 604 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 605 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 606 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 607 608config SECCOMP 609 prompt "Enable seccomp to safely execute untrusted bytecode" 610 def_bool y 611 depends on HAVE_ARCH_SECCOMP 612 help 613 This kernel feature is useful for number crunching applications 614 that may need to handle untrusted bytecode during their 615 execution. By using pipes or other transports made available 616 to the process as file descriptors supporting the read/write 617 syscalls, it's possible to isolate those applications in their 618 own address space using seccomp. Once seccomp is enabled via 619 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 620 disabled and the task is only allowed to execute a few safe 621 syscalls defined by each seccomp mode. 622 623 If unsure, say Y. 624 625config SECCOMP_FILTER 626 def_bool y 627 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 628 help 629 Enable tasks to build secure computing environments defined 630 in terms of Berkeley Packet Filter programs which implement 631 task-defined system call filtering polices. 632 633 See Documentation/userspace-api/seccomp_filter.rst for details. 634 635config SECCOMP_CACHE_DEBUG 636 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 637 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 638 depends on PROC_FS 639 help 640 This enables the /proc/pid/seccomp_cache interface to monitor 641 seccomp cache data. The file format is subject to change. Reading 642 the file requires CAP_SYS_ADMIN. 643 644 This option is for debugging only. Enabling presents the risk that 645 an adversary may be able to infer the seccomp filter logic. 646 647 If unsure, say N. 648 649config HAVE_ARCH_KSTACK_ERASE 650 bool 651 help 652 An architecture should select this if it has the code which 653 fills the used part of the kernel stack with the KSTACK_ERASE_POISON 654 value before returning from system calls. 655 656config HAVE_STACKPROTECTOR 657 bool 658 help 659 An arch should select this symbol if: 660 - it has implemented a stack canary (e.g. __stack_chk_guard) 661 662config STACKPROTECTOR 663 bool "Stack Protector buffer overflow detection" 664 depends on HAVE_STACKPROTECTOR 665 depends on $(cc-option,-fstack-protector) 666 default y 667 help 668 This option turns on the "stack-protector" GCC feature. This 669 feature puts, at the beginning of functions, a canary value on 670 the stack just before the return address, and validates 671 the value just before actually returning. Stack based buffer 672 overflows (that need to overwrite this return address) now also 673 overwrite the canary, which gets detected and the attack is then 674 neutralized via a kernel panic. 675 676 Functions will have the stack-protector canary logic added if they 677 have an 8-byte or larger character array on the stack. 678 679 This feature requires gcc version 4.2 or above, or a distribution 680 gcc with the feature backported ("-fstack-protector"). 681 682 On an x86 "defconfig" build, this feature adds canary checks to 683 about 3% of all kernel functions, which increases kernel code size 684 by about 0.3%. 685 686config STACKPROTECTOR_STRONG 687 bool "Strong Stack Protector" 688 depends on STACKPROTECTOR 689 depends on $(cc-option,-fstack-protector-strong) 690 default y 691 help 692 Functions will have the stack-protector canary logic added in any 693 of the following conditions: 694 695 - local variable's address used as part of the right hand side of an 696 assignment or function argument 697 - local variable is an array (or union containing an array), 698 regardless of array type or length 699 - uses register local variables 700 701 This feature requires gcc version 4.9 or above, or a distribution 702 gcc with the feature backported ("-fstack-protector-strong"). 703 704 On an x86 "defconfig" build, this feature adds canary checks to 705 about 20% of all kernel functions, which increases the kernel code 706 size by about 2%. 707 708config ARCH_SUPPORTS_SHADOW_CALL_STACK 709 bool 710 help 711 An architecture should select this if it supports the compiler's 712 Shadow Call Stack and implements runtime support for shadow stack 713 switching. 714 715config SHADOW_CALL_STACK 716 bool "Shadow Call Stack" 717 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 718 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 719 depends on MMU 720 help 721 This option enables the compiler's Shadow Call Stack, which 722 uses a shadow stack to protect function return addresses from 723 being overwritten by an attacker. More information can be found 724 in the compiler's documentation: 725 726 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 727 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 728 729 Note that security guarantees in the kernel differ from the 730 ones documented for user space. The kernel must store addresses 731 of shadow stacks in memory, which means an attacker capable of 732 reading and writing arbitrary memory may be able to locate them 733 and hijack control flow by modifying the stacks. 734 735config DYNAMIC_SCS 736 bool 737 help 738 Set by the arch code if it relies on code patching to insert the 739 shadow call stack push and pop instructions rather than on the 740 compiler. 741 742config LTO 743 bool 744 help 745 Selected if the kernel will be built using the compiler's LTO feature. 746 747config LTO_CLANG 748 bool 749 select LTO 750 help 751 Selected if the kernel will be built using Clang's LTO feature. 752 753config ARCH_SUPPORTS_LTO_CLANG 754 bool 755 help 756 An architecture should select this option if it supports: 757 - compiling with Clang, 758 - compiling inline assembly with Clang's integrated assembler, 759 - and linking with LLD. 760 761config ARCH_SUPPORTS_LTO_CLANG_THIN 762 bool 763 help 764 An architecture should select this option if it can support Clang's 765 ThinLTO mode. 766 767config HAS_LTO_CLANG 768 def_bool y 769 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 770 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 771 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 772 depends on ARCH_SUPPORTS_LTO_CLANG 773 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 774 # https://github.com/ClangBuiltLinux/linux/issues/1721 775 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 776 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 777 depends on !GCOV_KERNEL 778 help 779 The compiler and Kconfig options support building with Clang's 780 LTO. 781 782choice 783 prompt "Link Time Optimization (LTO)" 784 default LTO_NONE 785 help 786 This option enables Link Time Optimization (LTO), which allows the 787 compiler to optimize binaries globally. 788 789 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 790 so it's disabled by default. 791 792config LTO_NONE 793 bool "None" 794 help 795 Build the kernel normally, without Link Time Optimization (LTO). 796 797config LTO_CLANG_FULL 798 bool "Clang Full LTO (EXPERIMENTAL)" 799 depends on HAS_LTO_CLANG 800 depends on !COMPILE_TEST 801 select LTO_CLANG 802 help 803 This option enables Clang's full Link Time Optimization (LTO), which 804 allows the compiler to optimize the kernel globally. If you enable 805 this option, the compiler generates LLVM bitcode instead of ELF 806 object files, and the actual compilation from bitcode happens at 807 the LTO link step, which may take several minutes depending on the 808 kernel configuration. More information can be found from LLVM's 809 documentation: 810 811 https://llvm.org/docs/LinkTimeOptimization.html 812 813 During link time, this option can use a large amount of RAM, and 814 may take much longer than the ThinLTO option. 815 816config LTO_CLANG_THIN 817 bool "Clang ThinLTO (EXPERIMENTAL)" 818 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 819 select LTO_CLANG 820 help 821 This option enables Clang's ThinLTO, which allows for parallel 822 optimization and faster incremental compiles compared to the 823 CONFIG_LTO_CLANG_FULL option. More information can be found 824 from Clang's documentation: 825 826 https://clang.llvm.org/docs/ThinLTO.html 827 828 If unsure, say Y. 829endchoice 830 831config ARCH_SUPPORTS_AUTOFDO_CLANG 832 bool 833 834config AUTOFDO_CLANG 835 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 836 depends on ARCH_SUPPORTS_AUTOFDO_CLANG 837 depends on CC_IS_CLANG && CLANG_VERSION >= 170000 838 help 839 This option enables Clang’s AutoFDO build. When 840 an AutoFDO profile is specified in variable 841 CLANG_AUTOFDO_PROFILE during the build process, 842 Clang uses the profile to optimize the kernel. 843 844 If no profile is specified, AutoFDO options are 845 still passed to Clang to facilitate the collection 846 of perf data for creating an AutoFDO profile in 847 subsequent builds. 848 849 If unsure, say N. 850 851config ARCH_SUPPORTS_PROPELLER_CLANG 852 bool 853 854config PROPELLER_CLANG 855 bool "Enable Clang's Propeller build" 856 depends on ARCH_SUPPORTS_PROPELLER_CLANG 857 depends on CC_IS_CLANG && CLANG_VERSION >= 190000 858 help 859 This option enables Clang’s Propeller build. When the Propeller 860 profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX 861 during the build process, Clang uses the profiles to optimize 862 the kernel. 863 864 If no profile is specified, Propeller options are still passed 865 to Clang to facilitate the collection of perf data for creating 866 the Propeller profiles in subsequent builds. 867 868 If unsure, say N. 869 870config ARCH_SUPPORTS_CFI_CLANG 871 bool 872 help 873 An architecture should select this option if it can support Clang's 874 Control-Flow Integrity (CFI) checking. 875 876config ARCH_USES_CFI_TRAPS 877 bool 878 879config CFI_CLANG 880 bool "Use Clang's Control Flow Integrity (CFI)" 881 depends on ARCH_SUPPORTS_CFI_CLANG 882 depends on $(cc-option,-fsanitize=kcfi) 883 help 884 This option enables Clang's forward-edge Control Flow Integrity 885 (CFI) checking, where the compiler injects a runtime check to each 886 indirect function call to ensure the target is a valid function with 887 the correct static type. This restricts possible call targets and 888 makes it more difficult for an attacker to exploit bugs that allow 889 the modification of stored function pointers. More information can be 890 found from Clang's documentation: 891 892 https://clang.llvm.org/docs/ControlFlowIntegrity.html 893 894config CFI_ICALL_NORMALIZE_INTEGERS 895 bool "Normalize CFI tags for integers" 896 depends on CFI_CLANG 897 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 898 help 899 This option normalizes the CFI tags for integer types so that all 900 integer types of the same size and signedness receive the same CFI 901 tag. 902 903 The option is separate from CONFIG_RUST because it affects the ABI. 904 When working with build systems that care about the ABI, it is 905 convenient to be able to turn on this flag first, before Rust is 906 turned on. 907 908 This option is necessary for using CFI with Rust. If unsure, say N. 909 910config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 911 def_bool y 912 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 913 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 914 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 915 916config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 917 def_bool y 918 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 919 depends on RUSTC_VERSION >= 107900 920 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 921 depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \ 922 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 923 924config CFI_PERMISSIVE 925 bool "Use CFI in permissive mode" 926 depends on CFI_CLANG 927 help 928 When selected, Control Flow Integrity (CFI) violations result in a 929 warning instead of a kernel panic. This option should only be used 930 for finding indirect call type mismatches during development. 931 932 If unsure, say N. 933 934config HAVE_ARCH_WITHIN_STACK_FRAMES 935 bool 936 help 937 An architecture should select this if it can walk the kernel stack 938 frames to determine if an object is part of either the arguments 939 or local variables (i.e. that it excludes saved return addresses, 940 and similar) by implementing an inline arch_within_stack_frames(), 941 which is used by CONFIG_HARDENED_USERCOPY. 942 943config HAVE_CONTEXT_TRACKING_USER 944 bool 945 help 946 Provide kernel/user boundaries probes necessary for subsystems 947 that need it, such as userspace RCU extended quiescent state. 948 Syscalls need to be wrapped inside user_exit()-user_enter(), either 949 optimized behind static key or through the slow path using TIF_NOHZ 950 flag. Exceptions handlers must be wrapped as well. Irqs are already 951 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 952 handling on irq exit still need to be protected. 953 954config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 955 bool 956 help 957 Architecture neither relies on exception_enter()/exception_exit() 958 nor on schedule_user(). Also preempt_schedule_notrace() and 959 preempt_schedule_irq() can't be called in a preemptible section 960 while context tracking is CT_STATE_USER. This feature reflects a sane 961 entry implementation where the following requirements are met on 962 critical entry code, ie: before user_exit() or after user_enter(): 963 964 - Critical entry code isn't preemptible (or better yet: 965 not interruptible). 966 - No use of RCU read side critical sections, unless ct_nmi_enter() 967 got called. 968 - No use of instrumentation, unless instrumentation_begin() got 969 called. 970 971config HAVE_TIF_NOHZ 972 bool 973 help 974 Arch relies on TIF_NOHZ and syscall slow path to implement context 975 tracking calls to user_enter()/user_exit(). 976 977config HAVE_VIRT_CPU_ACCOUNTING 978 bool 979 980config HAVE_VIRT_CPU_ACCOUNTING_IDLE 981 bool 982 help 983 Architecture has its own way to account idle CPU time and therefore 984 doesn't implement vtime_account_idle(). 985 986config ARCH_HAS_SCALED_CPUTIME 987 bool 988 989config HAVE_VIRT_CPU_ACCOUNTING_GEN 990 bool 991 default y if 64BIT 992 help 993 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 994 Before enabling this option, arch code must be audited 995 to ensure there are no races in concurrent read/write of 996 cputime_t. For example, reading/writing 64-bit cputime_t on 997 some 32-bit arches may require multiple accesses, so proper 998 locking is needed to protect against concurrent accesses. 999 1000config HAVE_IRQ_TIME_ACCOUNTING 1001 bool 1002 help 1003 Archs need to ensure they use a high enough resolution clock to 1004 support irq time accounting and then call enable_sched_clock_irqtime(). 1005 1006config HAVE_MOVE_PUD 1007 bool 1008 help 1009 Architectures that select this are able to move page tables at the 1010 PUD level. If there are only 3 page table levels, the move effectively 1011 happens at the PGD level. 1012 1013config HAVE_MOVE_PMD 1014 bool 1015 help 1016 Archs that select this are able to move page tables at the PMD level. 1017 1018config HAVE_ARCH_TRANSPARENT_HUGEPAGE 1019 bool 1020 1021config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1022 bool 1023 1024config HAVE_ARCH_HUGE_VMAP 1025 bool 1026 1027# 1028# Archs that select this would be capable of PMD-sized vmaps (i.e., 1029# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 1030# must be used to enable allocations to use hugepages. 1031# 1032config HAVE_ARCH_HUGE_VMALLOC 1033 depends on HAVE_ARCH_HUGE_VMAP 1034 bool 1035 1036config ARCH_WANT_HUGE_PMD_SHARE 1037 bool 1038 1039# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1040# if there are no userspace memory management features that use it 1041config ARCH_WANT_KERNEL_PMD_MKWRITE 1042 bool 1043 1044config ARCH_WANT_PMD_MKWRITE 1045 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1046 1047config HAVE_ARCH_SOFT_DIRTY 1048 bool 1049 1050config HAVE_MOD_ARCH_SPECIFIC 1051 bool 1052 help 1053 The arch uses struct mod_arch_specific to store data. Many arches 1054 just need a simple module loader without arch specific data - those 1055 should not enable this. 1056 1057config MODULES_USE_ELF_RELA 1058 bool 1059 help 1060 Modules only use ELF RELA relocations. Modules with ELF REL 1061 relocations will give an error. 1062 1063config MODULES_USE_ELF_REL 1064 bool 1065 help 1066 Modules only use ELF REL relocations. Modules with ELF RELA 1067 relocations will give an error. 1068 1069config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1070 bool 1071 help 1072 For architectures like powerpc/32 which have constraints on module 1073 allocation and need to allocate module data outside of module area. 1074 1075config ARCH_WANTS_EXECMEM_LATE 1076 bool 1077 help 1078 For architectures that do not allocate executable memory early on 1079 boot, but rather require its initialization late when there is 1080 enough entropy for module space randomization, for instance 1081 arm64. 1082 1083config ARCH_HAS_EXECMEM_ROX 1084 bool 1085 depends on MMU && !HIGHMEM 1086 help 1087 For architectures that support allocations of executable memory 1088 with read-only execute permissions. Architecture must implement 1089 execmem_fill_trapping_insns() callback to enable this. 1090 1091config HAVE_IRQ_EXIT_ON_IRQ_STACK 1092 bool 1093 help 1094 Architecture doesn't only execute the irq handler on the irq stack 1095 but also irq_exit(). This way we can process softirqs on this irq 1096 stack instead of switching to a new one when we call __do_softirq() 1097 in the end of an hardirq. 1098 This spares a stack switch and improves cache usage on softirq 1099 processing. 1100 1101config HAVE_SOFTIRQ_ON_OWN_STACK 1102 bool 1103 help 1104 Architecture provides a function to run __do_softirq() on a 1105 separate stack. 1106 1107config SOFTIRQ_ON_OWN_STACK 1108 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1109 1110config ALTERNATE_USER_ADDRESS_SPACE 1111 bool 1112 help 1113 Architectures set this when the CPU uses separate address 1114 spaces for kernel and user space pointers. In this case, the 1115 access_ok() check on a __user pointer is skipped. 1116 1117config PGTABLE_LEVELS 1118 int 1119 default 2 1120 1121config ARCH_HAS_ELF_RANDOMIZE 1122 bool 1123 help 1124 An architecture supports choosing randomized locations for 1125 stack, mmap, brk, and ET_DYN. Defined functions: 1126 - arch_mmap_rnd() 1127 - arch_randomize_brk() 1128 1129config HAVE_ARCH_MMAP_RND_BITS 1130 bool 1131 help 1132 An arch should select this symbol if it supports setting a variable 1133 number of bits for use in establishing the base address for mmap 1134 allocations, has MMU enabled and provides values for both: 1135 - ARCH_MMAP_RND_BITS_MIN 1136 - ARCH_MMAP_RND_BITS_MAX 1137 1138config HAVE_EXIT_THREAD 1139 bool 1140 help 1141 An architecture implements exit_thread. 1142 1143config ARCH_MMAP_RND_BITS_MIN 1144 int 1145 1146config ARCH_MMAP_RND_BITS_MAX 1147 int 1148 1149config ARCH_MMAP_RND_BITS_DEFAULT 1150 int 1151 1152config ARCH_MMAP_RND_BITS 1153 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1154 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1155 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1156 default ARCH_MMAP_RND_BITS_MIN 1157 depends on HAVE_ARCH_MMAP_RND_BITS 1158 help 1159 This value can be used to select the number of bits to use to 1160 determine the random offset to the base address of vma regions 1161 resulting from mmap allocations. This value will be bounded 1162 by the architecture's minimum and maximum supported values. 1163 1164 This value can be changed after boot using the 1165 /proc/sys/vm/mmap_rnd_bits tunable 1166 1167config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1168 bool 1169 help 1170 An arch should select this symbol if it supports running applications 1171 in compatibility mode, supports setting a variable number of bits for 1172 use in establishing the base address for mmap allocations, has MMU 1173 enabled and provides values for both: 1174 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1175 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1176 1177config ARCH_MMAP_RND_COMPAT_BITS_MIN 1178 int 1179 1180config ARCH_MMAP_RND_COMPAT_BITS_MAX 1181 int 1182 1183config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1184 int 1185 1186config ARCH_MMAP_RND_COMPAT_BITS 1187 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1188 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1189 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1190 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1191 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1192 help 1193 This value can be used to select the number of bits to use to 1194 determine the random offset to the base address of vma regions 1195 resulting from mmap allocations for compatible applications This 1196 value will be bounded by the architecture's minimum and maximum 1197 supported values. 1198 1199 This value can be changed after boot using the 1200 /proc/sys/vm/mmap_rnd_compat_bits tunable 1201 1202config HAVE_ARCH_COMPAT_MMAP_BASES 1203 bool 1204 help 1205 This allows 64bit applications to invoke 32-bit mmap() syscall 1206 and vice-versa 32-bit applications to call 64-bit mmap(). 1207 Required for applications doing different bitness syscalls. 1208 1209config HAVE_PAGE_SIZE_4KB 1210 bool 1211 1212config HAVE_PAGE_SIZE_8KB 1213 bool 1214 1215config HAVE_PAGE_SIZE_16KB 1216 bool 1217 1218config HAVE_PAGE_SIZE_32KB 1219 bool 1220 1221config HAVE_PAGE_SIZE_64KB 1222 bool 1223 1224config HAVE_PAGE_SIZE_256KB 1225 bool 1226 1227choice 1228 prompt "MMU page size" 1229 1230config PAGE_SIZE_4KB 1231 bool "4KiB pages" 1232 depends on HAVE_PAGE_SIZE_4KB 1233 help 1234 This option select the standard 4KiB Linux page size and the only 1235 available option on many architectures. Using 4KiB page size will 1236 minimize memory consumption and is therefore recommended for low 1237 memory systems. 1238 Some software that is written for x86 systems makes incorrect 1239 assumptions about the page size and only runs on 4KiB pages. 1240 1241config PAGE_SIZE_8KB 1242 bool "8KiB pages" 1243 depends on HAVE_PAGE_SIZE_8KB 1244 help 1245 This option is the only supported page size on a few older 1246 processors, and can be slightly faster than 4KiB pages. 1247 1248config PAGE_SIZE_16KB 1249 bool "16KiB pages" 1250 depends on HAVE_PAGE_SIZE_16KB 1251 help 1252 This option is usually a good compromise between memory 1253 consumption and performance for typical desktop and server 1254 workloads, often saving a level of page table lookups compared 1255 to 4KB pages as well as reducing TLB pressure and overhead of 1256 per-page operations in the kernel at the expense of a larger 1257 page cache. 1258 1259config PAGE_SIZE_32KB 1260 bool "32KiB pages" 1261 depends on HAVE_PAGE_SIZE_32KB 1262 help 1263 Using 32KiB page size will result in slightly higher performance 1264 kernel at the price of higher memory consumption compared to 1265 16KiB pages. This option is available only on cnMIPS cores. 1266 Note that you will need a suitable Linux distribution to 1267 support this. 1268 1269config PAGE_SIZE_64KB 1270 bool "64KiB pages" 1271 depends on HAVE_PAGE_SIZE_64KB 1272 help 1273 Using 64KiB page size will result in slightly higher performance 1274 kernel at the price of much higher memory consumption compared to 1275 4KiB or 16KiB pages. 1276 This is not suitable for general-purpose workloads but the 1277 better performance may be worth the cost for certain types of 1278 supercomputing or database applications that work mostly with 1279 large in-memory data rather than small files. 1280 1281config PAGE_SIZE_256KB 1282 bool "256KiB pages" 1283 depends on HAVE_PAGE_SIZE_256KB 1284 help 1285 256KiB pages have little practical value due to their extreme 1286 memory usage. The kernel will only be able to run applications 1287 that have been compiled with '-zmax-page-size' set to 256KiB 1288 (the default is 64KiB or 4KiB on most architectures). 1289 1290endchoice 1291 1292config PAGE_SIZE_LESS_THAN_64KB 1293 def_bool y 1294 depends on !PAGE_SIZE_64KB 1295 depends on PAGE_SIZE_LESS_THAN_256KB 1296 1297config PAGE_SIZE_LESS_THAN_256KB 1298 def_bool y 1299 depends on !PAGE_SIZE_256KB 1300 1301config PAGE_SHIFT 1302 int 1303 default 12 if PAGE_SIZE_4KB 1304 default 13 if PAGE_SIZE_8KB 1305 default 14 if PAGE_SIZE_16KB 1306 default 15 if PAGE_SIZE_32KB 1307 default 16 if PAGE_SIZE_64KB 1308 default 18 if PAGE_SIZE_256KB 1309 1310# This allows to use a set of generic functions to determine mmap base 1311# address by giving priority to top-down scheme only if the process 1312# is not in legacy mode (compat task, unlimited stack size or 1313# sysctl_legacy_va_layout). 1314# Architecture that selects this option can provide its own version of: 1315# - STACK_RND_MASK 1316config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1317 bool 1318 depends on MMU 1319 select ARCH_HAS_ELF_RANDOMIZE 1320 1321config HAVE_OBJTOOL 1322 bool 1323 1324config HAVE_JUMP_LABEL_HACK 1325 bool 1326 1327config HAVE_NOINSTR_HACK 1328 bool 1329 1330config HAVE_NOINSTR_VALIDATION 1331 bool 1332 1333config HAVE_UACCESS_VALIDATION 1334 bool 1335 select OBJTOOL 1336 1337config HAVE_STACK_VALIDATION 1338 bool 1339 help 1340 Architecture supports objtool compile-time frame pointer rule 1341 validation. 1342 1343config HAVE_RELIABLE_STACKTRACE 1344 bool 1345 help 1346 Architecture has either save_stack_trace_tsk_reliable() or 1347 arch_stack_walk_reliable() function which only returns a stack trace 1348 if it can guarantee the trace is reliable. 1349 1350config HAVE_ARCH_HASH 1351 bool 1352 default n 1353 help 1354 If this is set, the architecture provides an <asm/hash.h> 1355 file which provides platform-specific implementations of some 1356 functions in <linux/hash.h> or fs/namei.c. 1357 1358config HAVE_ARCH_NVRAM_OPS 1359 bool 1360 1361config ISA_BUS_API 1362 def_bool ISA 1363 1364# 1365# ABI hall of shame 1366# 1367config CLONE_BACKWARDS 1368 bool 1369 help 1370 Architecture has tls passed as the 4th argument of clone(2), 1371 not the 5th one. 1372 1373config CLONE_BACKWARDS2 1374 bool 1375 help 1376 Architecture has the first two arguments of clone(2) swapped. 1377 1378config CLONE_BACKWARDS3 1379 bool 1380 help 1381 Architecture has tls passed as the 3rd argument of clone(2), 1382 not the 5th one. 1383 1384config ODD_RT_SIGACTION 1385 bool 1386 help 1387 Architecture has unusual rt_sigaction(2) arguments 1388 1389config OLD_SIGSUSPEND 1390 bool 1391 help 1392 Architecture has old sigsuspend(2) syscall, of one-argument variety 1393 1394config OLD_SIGSUSPEND3 1395 bool 1396 help 1397 Even weirder antique ABI - three-argument sigsuspend(2) 1398 1399config OLD_SIGACTION 1400 bool 1401 help 1402 Architecture has old sigaction(2) syscall. Nope, not the same 1403 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1404 but fairly different variant of sigaction(2), thanks to OSF/1 1405 compatibility... 1406 1407config COMPAT_OLD_SIGACTION 1408 bool 1409 1410config COMPAT_32BIT_TIME 1411 bool "Provide system calls for 32-bit time_t" 1412 default !64BIT || COMPAT 1413 help 1414 This enables 32 bit time_t support in addition to 64 bit time_t support. 1415 This is relevant on all 32-bit architectures, and 64-bit architectures 1416 as part of compat syscall handling. 1417 1418config ARCH_NO_PREEMPT 1419 bool 1420 1421config ARCH_SUPPORTS_RT 1422 bool 1423 1424config CPU_NO_EFFICIENT_FFS 1425 def_bool n 1426 1427config HAVE_ARCH_VMAP_STACK 1428 def_bool n 1429 help 1430 An arch should select this symbol if it can support kernel stacks 1431 in vmalloc space. This means: 1432 1433 - vmalloc space must be large enough to hold many kernel stacks. 1434 This may rule out many 32-bit architectures. 1435 1436 - Stacks in vmalloc space need to work reliably. For example, if 1437 vmap page tables are created on demand, either this mechanism 1438 needs to work while the stack points to a virtual address with 1439 unpopulated page tables or arch code (switch_to() and switch_mm(), 1440 most likely) needs to ensure that the stack's page table entries 1441 are populated before running on a possibly unpopulated stack. 1442 1443 - If the stack overflows into a guard page, something reasonable 1444 should happen. The definition of "reasonable" is flexible, but 1445 instantly rebooting without logging anything would be unfriendly. 1446 1447config VMAP_STACK 1448 default y 1449 bool "Use a virtually-mapped stack" 1450 depends on HAVE_ARCH_VMAP_STACK 1451 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1452 help 1453 Enable this if you want the use virtually-mapped kernel stacks 1454 with guard pages. This causes kernel stack overflows to be 1455 caught immediately rather than causing difficult-to-diagnose 1456 corruption. 1457 1458 To use this with software KASAN modes, the architecture must support 1459 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1460 must be enabled. 1461 1462config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1463 def_bool n 1464 help 1465 An arch should select this symbol if it can support kernel stack 1466 offset randomization with calls to add_random_kstack_offset() 1467 during syscall entry and choose_random_kstack_offset() during 1468 syscall exit. Careful removal of -fstack-protector-strong and 1469 -fstack-protector should also be applied to the entry code and 1470 closely examined, as the artificial stack bump looks like an array 1471 to the compiler, so it will attempt to add canary checks regardless 1472 of the static branch state. 1473 1474config RANDOMIZE_KSTACK_OFFSET 1475 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1476 default y 1477 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1478 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1479 help 1480 The kernel stack offset can be randomized (after pt_regs) by 1481 roughly 5 bits of entropy, frustrating memory corruption 1482 attacks that depend on stack address determinism or 1483 cross-syscall address exposures. 1484 1485 The feature is controlled via the "randomize_kstack_offset=on/off" 1486 kernel boot param, and if turned off has zero overhead due to its use 1487 of static branches (see JUMP_LABEL). 1488 1489 If unsure, say Y. 1490 1491config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1492 bool "Default state of kernel stack offset randomization" 1493 depends on RANDOMIZE_KSTACK_OFFSET 1494 help 1495 Kernel stack offset randomization is controlled by kernel boot param 1496 "randomize_kstack_offset=on/off", and this config chooses the default 1497 boot state. 1498 1499config ARCH_OPTIONAL_KERNEL_RWX 1500 def_bool n 1501 1502config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1503 def_bool n 1504 1505config ARCH_HAS_STRICT_KERNEL_RWX 1506 def_bool n 1507 1508config STRICT_KERNEL_RWX 1509 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1510 depends on ARCH_HAS_STRICT_KERNEL_RWX 1511 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1512 help 1513 If this is set, kernel text and rodata memory will be made read-only, 1514 and non-text memory will be made non-executable. This provides 1515 protection against certain security exploits (e.g. executing the heap 1516 or modifying text) 1517 1518 These features are considered standard security practice these days. 1519 You should say Y here in almost all cases. 1520 1521config ARCH_HAS_STRICT_MODULE_RWX 1522 def_bool n 1523 1524config STRICT_MODULE_RWX 1525 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1526 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1527 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1528 help 1529 If this is set, module text and rodata memory will be made read-only, 1530 and non-text memory will be made non-executable. This provides 1531 protection against certain security exploits (e.g. writing to text) 1532 1533# select if the architecture provides an asm/dma-direct.h header 1534config ARCH_HAS_PHYS_TO_DMA 1535 bool 1536 1537config ARCH_HAS_CPU_RESCTRL 1538 bool 1539 help 1540 An architecture selects this option to indicate that the necessary 1541 hooks are provided to support the common memory system usage 1542 monitoring and control interfaces provided by the 'resctrl' 1543 filesystem (see RESCTRL_FS). 1544 1545config HAVE_ARCH_COMPILER_H 1546 bool 1547 help 1548 An architecture can select this if it provides an 1549 asm/compiler.h header that should be included after 1550 linux/compiler-*.h in order to override macro definitions that those 1551 headers generally provide. 1552 1553config HAVE_ARCH_LIBGCC_H 1554 bool 1555 help 1556 An architecture can select this if it provides an 1557 asm/libgcc.h header that should be included after 1558 linux/libgcc.h in order to override macro definitions that 1559 header generally provides. 1560 1561config HAVE_ARCH_PREL32_RELOCATIONS 1562 bool 1563 help 1564 May be selected by an architecture if it supports place-relative 1565 32-bit relocations, both in the toolchain and in the module loader, 1566 in which case relative references can be used in special sections 1567 for PCI fixup, initcalls etc which are only half the size on 64 bit 1568 architectures, and don't require runtime relocation on relocatable 1569 kernels. 1570 1571config ARCH_USE_MEMREMAP_PROT 1572 bool 1573 1574config LOCK_EVENT_COUNTS 1575 bool "Locking event counts collection" 1576 depends on DEBUG_FS 1577 help 1578 Enable light-weight counting of various locking related events 1579 in the system with minimal performance impact. This reduces 1580 the chance of application behavior change because of timing 1581 differences. The counts are reported via debugfs. 1582 1583# Select if the architecture has support for applying RELR relocations. 1584config ARCH_HAS_RELR 1585 bool 1586 1587config RELR 1588 bool "Use RELR relocation packing" 1589 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1590 default y 1591 help 1592 Store the kernel's dynamic relocations in the RELR relocation packing 1593 format. Requires a compatible linker (LLD supports this feature), as 1594 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1595 are compatible). 1596 1597config ARCH_HAS_MEM_ENCRYPT 1598 bool 1599 1600config ARCH_HAS_CC_PLATFORM 1601 bool 1602 1603config HAVE_SPARSE_SYSCALL_NR 1604 bool 1605 help 1606 An architecture should select this if its syscall numbering is sparse 1607 to save space. For example, MIPS architecture has a syscall array with 1608 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1609 related optimizations for a given architecture. 1610 1611config ARCH_HAS_VDSO_ARCH_DATA 1612 depends on GENERIC_VDSO_DATA_STORE 1613 bool 1614 1615config ARCH_HAS_VDSO_TIME_DATA 1616 bool 1617 1618config HAVE_STATIC_CALL 1619 bool 1620 1621config HAVE_STATIC_CALL_INLINE 1622 bool 1623 depends on HAVE_STATIC_CALL 1624 select OBJTOOL 1625 1626config HAVE_PREEMPT_DYNAMIC 1627 bool 1628 1629config HAVE_PREEMPT_DYNAMIC_CALL 1630 bool 1631 depends on HAVE_STATIC_CALL 1632 select HAVE_PREEMPT_DYNAMIC 1633 help 1634 An architecture should select this if it can handle the preemption 1635 model being selected at boot time using static calls. 1636 1637 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1638 preemption function will be patched directly. 1639 1640 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1641 call to a preemption function will go through a trampoline, and the 1642 trampoline will be patched. 1643 1644 It is strongly advised to support inline static call to avoid any 1645 overhead. 1646 1647config HAVE_PREEMPT_DYNAMIC_KEY 1648 bool 1649 depends on HAVE_ARCH_JUMP_LABEL 1650 select HAVE_PREEMPT_DYNAMIC 1651 help 1652 An architecture should select this if it can handle the preemption 1653 model being selected at boot time using static keys. 1654 1655 Each preemption function will be given an early return based on a 1656 static key. This should have slightly lower overhead than non-inline 1657 static calls, as this effectively inlines each trampoline into the 1658 start of its callee. This may avoid redundant work, and may 1659 integrate better with CFI schemes. 1660 1661 This will have greater overhead than using inline static calls as 1662 the call to the preemption function cannot be entirely elided. 1663 1664config ARCH_WANT_LD_ORPHAN_WARN 1665 bool 1666 help 1667 An arch should select this symbol once all linker sections are explicitly 1668 included, size-asserted, or discarded in the linker scripts. This is 1669 important because we never want expected sections to be placed heuristically 1670 by the linker, since the locations of such sections can change between linker 1671 versions. 1672 1673config HAVE_ARCH_PFN_VALID 1674 bool 1675 1676config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1677 bool 1678 1679config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1680 bool 1681 1682config ARCH_SPLIT_ARG64 1683 bool 1684 help 1685 If a 32-bit architecture requires 64-bit arguments to be split into 1686 pairs of 32-bit arguments, select this option. 1687 1688config ARCH_HAS_ELFCORE_COMPAT 1689 bool 1690 1691config ARCH_HAS_PARANOID_L1D_FLUSH 1692 bool 1693 1694config ARCH_HAVE_TRACE_MMIO_ACCESS 1695 bool 1696 1697config DYNAMIC_SIGFRAME 1698 bool 1699 1700# Select, if arch has a named attribute group bound to NUMA device nodes. 1701config HAVE_ARCH_NODE_DEV_GROUP 1702 bool 1703 1704config ARCH_HAS_HW_PTE_YOUNG 1705 bool 1706 help 1707 Architectures that select this option are capable of setting the 1708 accessed bit in PTE entries when using them as part of linear address 1709 translations. Architectures that require runtime check should select 1710 this option and override arch_has_hw_pte_young(). 1711 1712config ARCH_HAS_NONLEAF_PMD_YOUNG 1713 bool 1714 help 1715 Architectures that select this option are capable of setting the 1716 accessed bit in non-leaf PMD entries when using them as part of linear 1717 address translations. Page table walkers that clear the accessed bit 1718 may use this capability to reduce their search space. 1719 1720config ARCH_HAS_KERNEL_FPU_SUPPORT 1721 bool 1722 help 1723 Architectures that select this option can run floating-point code in 1724 the kernel, as described in Documentation/core-api/floating-point.rst. 1725 1726config ARCH_VMLINUX_NEEDS_RELOCS 1727 bool 1728 help 1729 Whether the architecture needs vmlinux to be built with static 1730 relocations preserved. This is used by some architectures to 1731 construct bespoke relocation tables for KASLR. 1732 1733source "kernel/gcov/Kconfig" 1734 1735source "scripts/gcc-plugins/Kconfig" 1736 1737config FUNCTION_ALIGNMENT_4B 1738 bool 1739 1740config FUNCTION_ALIGNMENT_8B 1741 bool 1742 1743config FUNCTION_ALIGNMENT_16B 1744 bool 1745 1746config FUNCTION_ALIGNMENT_32B 1747 bool 1748 1749config FUNCTION_ALIGNMENT_64B 1750 bool 1751 1752config FUNCTION_ALIGNMENT 1753 int 1754 default 64 if FUNCTION_ALIGNMENT_64B 1755 default 32 if FUNCTION_ALIGNMENT_32B 1756 default 16 if FUNCTION_ALIGNMENT_16B 1757 default 8 if FUNCTION_ALIGNMENT_8B 1758 default 4 if FUNCTION_ALIGNMENT_4B 1759 default 0 1760 1761config CC_HAS_MIN_FUNCTION_ALIGNMENT 1762 # Detect availability of the GCC option -fmin-function-alignment which 1763 # guarantees minimal alignment for all functions, unlike 1764 # -falign-functions which the compiler ignores for cold functions. 1765 def_bool $(cc-option, -fmin-function-alignment=8) 1766 1767config CC_HAS_SANE_FUNCTION_ALIGNMENT 1768 # Set if the guaranteed alignment with -fmin-function-alignment is 1769 # available or extra care is required in the kernel. Clang provides 1770 # strict alignment always, even with -falign-functions. 1771 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1772 1773config ARCH_NEED_CMPXCHG_1_EMU 1774 bool 1775 1776config ARCH_WANTS_PRE_LINK_VMLINUX 1777 bool 1778 help 1779 An architecture can select this if it provides arch/<arch>/tools/Makefile 1780 with .arch.vmlinux.o target to be linked into vmlinux. 1781 1782config ARCH_HAS_CPU_ATTACK_VECTORS 1783 bool 1784 1785endmenu 1786