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