1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6# 7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8# override the default values in this file. 9# 10source "arch/$(SRCARCH)/Kconfig" 11 12config ARCH_CONFIGURES_CPU_MITIGATIONS 13 bool 14 15if !ARCH_CONFIGURES_CPU_MITIGATIONS 16config CPU_MITIGATIONS 17 def_bool y 18endif 19 20# 21# Selected by architectures that need custom DMA operations for e.g. legacy 22# IOMMUs not handled by dma-iommu. Drivers must never select this symbol. 23# 24config ARCH_HAS_DMA_OPS 25 depends on HAS_DMA 26 select DMA_OPS_HELPERS 27 bool 28 29menu "General architecture-dependent options" 30 31config ARCH_HAS_SUBPAGE_FAULTS 32 bool 33 help 34 Select if the architecture can check permissions at sub-page 35 granularity (e.g. arm64 MTE). The probe_user_*() functions 36 must be implemented. 37 38config HOTPLUG_SMT 39 bool 40 41config SMT_NUM_THREADS_DYNAMIC 42 bool 43 44config ARCH_SUPPORTS_SCHED_SMT 45 bool 46 47config ARCH_SUPPORTS_SCHED_CLUSTER 48 bool 49 50config ARCH_SUPPORTS_SCHED_MC 51 bool 52 53config SCHED_SMT 54 bool "SMT (Hyperthreading) scheduler support" 55 depends on ARCH_SUPPORTS_SCHED_SMT 56 default y 57 help 58 Improves the CPU scheduler's decision making when dealing with 59 MultiThreading at a cost of slightly increased overhead in some 60 places. If unsure say N here. 61 62config SCHED_CLUSTER 63 bool "Cluster scheduler support" 64 depends on ARCH_SUPPORTS_SCHED_CLUSTER 65 default y 66 help 67 Cluster scheduler support improves the CPU scheduler's decision 68 making when dealing with machines that have clusters of CPUs. 69 Cluster usually means a couple of CPUs which are placed closely 70 by sharing mid-level caches, last-level cache tags or internal 71 busses. 72 73config SCHED_MC 74 bool "Multi-Core Cache (MC) scheduler support" 75 depends on ARCH_SUPPORTS_SCHED_MC 76 default y 77 help 78 Multi-core scheduler support improves the CPU scheduler's decision 79 making when dealing with multi-core CPU chips at a cost of slightly 80 increased overhead in some places. If unsure say N here. 81 82# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 83config HOTPLUG_CORE_SYNC 84 bool 85 86# Basic CPU dead synchronization selected by architecture 87config HOTPLUG_CORE_SYNC_DEAD 88 bool 89 select HOTPLUG_CORE_SYNC 90 91# Full CPU synchronization with alive state selected by architecture 92config HOTPLUG_CORE_SYNC_FULL 93 bool 94 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 95 select HOTPLUG_CORE_SYNC 96 97config HOTPLUG_SPLIT_STARTUP 98 bool 99 select HOTPLUG_CORE_SYNC_FULL 100 101config HOTPLUG_PARALLEL 102 bool 103 select HOTPLUG_SPLIT_STARTUP 104 105config GENERIC_IRQ_ENTRY 106 bool 107 108config GENERIC_SYSCALL 109 bool 110 depends on GENERIC_IRQ_ENTRY 111 112config GENERIC_ENTRY 113 bool 114 select GENERIC_IRQ_ENTRY 115 select GENERIC_SYSCALL 116 117config KPROBES 118 bool "Kprobes" 119 depends on HAVE_KPROBES 120 select KALLSYMS 121 select EXECMEM 122 select NEED_TASKS_RCU 123 help 124 Kprobes allows you to trap at almost any kernel address and 125 execute a callback function. register_kprobe() establishes 126 a probepoint and specifies the callback. Kprobes is useful 127 for kernel debugging, non-intrusive instrumentation and testing. 128 If in doubt, say "N". 129 130config JUMP_LABEL 131 bool "Optimize very unlikely/likely branches" 132 depends on HAVE_ARCH_JUMP_LABEL 133 select OBJTOOL if HAVE_JUMP_LABEL_HACK 134 help 135 This option enables a transparent branch optimization that 136 makes certain almost-always-true or almost-always-false branch 137 conditions even cheaper to execute within the kernel. 138 139 Certain performance-sensitive kernel code, such as trace points, 140 scheduler functionality, networking code and KVM have such 141 branches and include support for this optimization technique. 142 143 If it is detected that the compiler has support for "asm goto", 144 the kernel will compile such branches with just a nop 145 instruction. When the condition flag is toggled to true, the 146 nop will be converted to a jump instruction to execute the 147 conditional block of instructions. 148 149 This technique lowers overhead and stress on the branch prediction 150 of the processor and generally makes the kernel faster. The update 151 of the condition is slower, but those are always very rare. 152 153 ( On 32-bit x86, the necessary options added to the compiler 154 flags may increase the size of the kernel slightly. ) 155 156config STATIC_KEYS_SELFTEST 157 bool "Static key selftest" 158 depends on JUMP_LABEL 159 help 160 Boot time self-test of the branch patching code. 161 162config STATIC_CALL_SELFTEST 163 bool "Static call selftest" 164 depends on HAVE_STATIC_CALL 165 help 166 Boot time self-test of the call patching code. 167 168config OPTPROBES 169 def_bool y 170 depends on KPROBES && HAVE_OPTPROBES 171 select NEED_TASKS_RCU 172 173config KPROBES_ON_FTRACE 174 def_bool y 175 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 176 depends on DYNAMIC_FTRACE_WITH_REGS 177 help 178 If function tracer is enabled and the arch supports full 179 passing of pt_regs to function tracing, then kprobes can 180 optimize on top of function tracing. 181 182config UPROBES 183 def_bool n 184 depends on ARCH_SUPPORTS_UPROBES 185 select TASKS_TRACE_RCU 186 help 187 Uprobes is the user-space counterpart to kprobes: they 188 enable instrumentation applications (such as 'perf probe') 189 to establish unintrusive probes in user-space binaries and 190 libraries, by executing handler functions when the probes 191 are hit by user-space applications. 192 193 ( These probes come in the form of single-byte breakpoints, 194 managed by the kernel and kept transparent to the probed 195 application. ) 196 197config HAVE_64BIT_ALIGNED_ACCESS 198 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 199 help 200 Some architectures require 64 bit accesses to be 64 bit 201 aligned, which also requires structs containing 64 bit values 202 to be 64 bit aligned too. This includes some 32 bit 203 architectures which can do 64 bit accesses, as well as 64 bit 204 architectures without unaligned access. 205 206 This symbol should be selected by an architecture if 64 bit 207 accesses are required to be 64 bit aligned in this way even 208 though it is not a 64 bit architecture. 209 210 See Documentation/core-api/unaligned-memory-access.rst for 211 more information on the topic of unaligned memory accesses. 212 213config HAVE_EFFICIENT_UNALIGNED_ACCESS 214 bool 215 help 216 Some architectures are unable to perform unaligned accesses 217 without the use of get_unaligned/put_unaligned. Others are 218 unable to perform such accesses efficiently (e.g. trap on 219 unaligned access and require fixing it up in the exception 220 handler.) 221 222 This symbol should be selected by an architecture if it can 223 perform unaligned accesses efficiently to allow different 224 code paths to be selected for these cases. Some network 225 drivers, for example, could opt to not fix up alignment 226 problems with received packets if doing so would not help 227 much. 228 229 See Documentation/core-api/unaligned-memory-access.rst for more 230 information on the topic of unaligned memory accesses. 231 232config ARCH_USE_BUILTIN_BSWAP 233 bool 234 help 235 GCC and Clang have builtin functions for handling byte-swapping. 236 Using these allows the compiler to see what's happening and 237 offers more opportunity for optimisation. In particular, the 238 compiler will be able to combine the byteswap with a nearby load 239 or store and use load-and-swap or store-and-swap instructions if 240 the architecture has them. It should almost *never* result in code 241 which is worse than the hand-coded assembler in <asm/swab.h>. 242 But just in case it does, the use of the builtins is optional. 243 244 Any architecture with load-and-swap or store-and-swap 245 instructions should set this. And it shouldn't hurt to set it 246 on architectures that don't have such instructions. 247 248config KRETPROBES 249 def_bool y 250 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 251 252config KRETPROBE_ON_RETHOOK 253 def_bool y 254 depends on HAVE_RETHOOK 255 depends on KRETPROBES 256 select RETHOOK 257 258config USER_RETURN_NOTIFIER 259 bool 260 depends on HAVE_USER_RETURN_NOTIFIER 261 help 262 Provide a kernel-internal notification when a cpu is about to 263 switch to user mode. 264 265config HAVE_IOREMAP_PROT 266 bool 267 268config HAVE_KPROBES 269 bool 270 271config HAVE_KRETPROBES 272 bool 273 274config HAVE_OPTPROBES 275 bool 276 277config HAVE_KPROBES_ON_FTRACE 278 bool 279 280config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 281 bool 282 help 283 Since kretprobes modifies return address on the stack, the 284 stacktrace may see the kretprobe trampoline address instead 285 of correct one. If the architecture stacktrace code and 286 unwinder can adjust such entries, select this configuration. 287 288config HAVE_FUNCTION_ERROR_INJECTION 289 bool 290 291config HAVE_NMI 292 bool 293 294config HAVE_FUNCTION_DESCRIPTORS 295 bool 296 297config TRACE_IRQFLAGS_SUPPORT 298 bool 299 300config TRACE_IRQFLAGS_NMI_SUPPORT 301 bool 302 303# 304# An arch should select this if it provides all these things: 305# 306# task_pt_regs() in asm/processor.h or asm/ptrace.h 307# arch_has_single_step() if there is hardware single-step support 308# arch_has_block_step() if there is hardware block-step support 309# asm/syscall.h supplying asm-generic/syscall.h interface 310# linux/regset.h user_regset interfaces 311# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 312# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 313# TIF_NOTIFY_RESUME calls resume_user_mode_work() 314# 315config HAVE_ARCH_TRACEHOOK 316 bool 317 318config HAVE_DMA_CONTIGUOUS 319 bool 320 321config GENERIC_SMP_IDLE_THREAD 322 bool 323 324config GENERIC_IDLE_POLL_SETUP 325 bool 326 327config ARCH_HAS_FORTIFY_SOURCE 328 bool 329 help 330 An architecture should select this when it can successfully 331 build and run with CONFIG_FORTIFY_SOURCE. 332 333# 334# Select if the arch provides a historic keepinit alias for the retain_initrd 335# command line option 336# 337config ARCH_HAS_KEEPINITRD 338 bool 339 340# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 341config ARCH_HAS_SET_MEMORY 342 bool 343 344# Select if arch has all set_direct_map_invalid/default() functions 345config ARCH_HAS_SET_DIRECT_MAP 346 bool 347 348# 349# Select if the architecture provides the arch_dma_set_uncached symbol to 350# either provide an uncached segment alias for a DMA allocation, or 351# to remap the page tables in place. 352# 353config ARCH_HAS_DMA_SET_UNCACHED 354 bool 355 356# 357# Select if the architectures provides the arch_dma_clear_uncached symbol 358# to undo an in-place page table remap for uncached access. 359# 360config ARCH_HAS_DMA_CLEAR_UNCACHED 361 bool 362 363config ARCH_HAS_CPU_FINALIZE_INIT 364 bool 365 366# The architecture has a per-task state that includes the mm's PASID 367config ARCH_HAS_CPU_PASID 368 bool 369 select IOMMU_MM_DATA 370 371config HAVE_ARCH_THREAD_STRUCT_WHITELIST 372 bool 373 help 374 An architecture should select this to provide hardened usercopy 375 knowledge about what region of the thread_struct should be 376 whitelisted for copying to userspace. Normally this is only the 377 FPU registers. Specifically, arch_thread_struct_whitelist() 378 should be implemented. Without this, the entire thread_struct 379 field in task_struct will be left whitelisted. 380 381# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 382config ARCH_WANTS_DYNAMIC_TASK_STRUCT 383 bool 384 385config ARCH_WANTS_NO_INSTR 386 bool 387 help 388 An architecture should select this if the noinstr macro is being used on 389 functions to denote that the toolchain should avoid instrumenting such 390 functions and is required for correctness. 391 392config ARCH_32BIT_OFF_T 393 bool 394 depends on !64BIT 395 help 396 All new 32-bit architectures should have 64-bit off_t type on 397 userspace side which corresponds to the loff_t kernel type. This 398 is the requirement for modern ABIs. Some existing architectures 399 still support 32-bit off_t. This option is enabled for all such 400 architectures explicitly. 401 402# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 403config ARCH_32BIT_USTAT_F_TINODE 404 bool 405 406# Selected by architectures with Total Store Order (TSO) 407config ARCH_MEMORY_ORDER_TSO 408 bool 409 410config HAVE_ASM_MODVERSIONS 411 bool 412 help 413 This symbol should be selected by an architecture if it provides 414 <asm/asm-prototypes.h> to support the module versioning for symbols 415 exported from assembly code. 416 417config HAVE_REGS_AND_STACK_ACCESS_API 418 bool 419 help 420 This symbol should be selected by an architecture if it supports 421 the API needed to access registers and stack entries from pt_regs, 422 declared in asm/ptrace.h 423 For example the kprobes-based event tracer needs this API. 424 425config HAVE_RSEQ 426 bool 427 depends on HAVE_REGS_AND_STACK_ACCESS_API 428 help 429 This symbol should be selected by an architecture if it 430 supports an implementation of restartable sequences. 431 432config HAVE_RUST 433 bool 434 help 435 This symbol should be selected by an architecture if it 436 supports Rust. 437 438config HAVE_FUNCTION_ARG_ACCESS_API 439 bool 440 help 441 This symbol should be selected by an architecture if it supports 442 the API needed to access function arguments from pt_regs, 443 declared in asm/ptrace.h 444 445config HAVE_HW_BREAKPOINT 446 bool 447 depends on PERF_EVENTS 448 449config HAVE_MIXED_BREAKPOINTS_REGS 450 bool 451 depends on HAVE_HW_BREAKPOINT 452 help 453 Depending on the arch implementation of hardware breakpoints, 454 some of them have separate registers for data and instruction 455 breakpoints addresses, others have mixed registers to store 456 them but define the access type in a control register. 457 Select this option if your arch implements breakpoints under the 458 latter fashion. 459 460config HAVE_USER_RETURN_NOTIFIER 461 bool 462 463config HAVE_PERF_EVENTS_NMI 464 bool 465 help 466 System hardware can generate an NMI using the perf event 467 subsystem. Also has support for calculating CPU cycle events 468 to determine how many clock cycles in a given period. 469 470config HAVE_HARDLOCKUP_DETECTOR_PERF 471 bool 472 depends on HAVE_PERF_EVENTS_NMI 473 help 474 The arch chooses to use the generic perf-NMI-based hardlockup 475 detector. Must define HAVE_PERF_EVENTS_NMI. 476 477config HAVE_HARDLOCKUP_DETECTOR_ARCH 478 bool 479 help 480 The arch provides its own hardlockup detector implementation instead 481 of the generic ones. 482 483 It uses the same command line parameters, and sysctl interface, 484 as the generic hardlockup detectors. 485 486config UNWIND_USER 487 bool 488 489config HAVE_UNWIND_USER_FP 490 bool 491 select UNWIND_USER 492 493config HAVE_PERF_REGS 494 bool 495 help 496 Support selective register dumps for perf events. This includes 497 bit-mapping of each registers and a unique architecture id. 498 499config HAVE_PERF_USER_STACK_DUMP 500 bool 501 help 502 Support user stack dumps for perf event samples. This needs 503 access to the user stack pointer which is not unified across 504 architectures. 505 506config HAVE_ARCH_JUMP_LABEL 507 bool 508 509config HAVE_ARCH_JUMP_LABEL_RELATIVE 510 bool 511 512config MMU_GATHER_TABLE_FREE 513 bool 514 515config MMU_GATHER_RCU_TABLE_FREE 516 bool 517 select MMU_GATHER_TABLE_FREE 518 519config MMU_GATHER_PAGE_SIZE 520 bool 521 522config MMU_GATHER_NO_RANGE 523 bool 524 select MMU_GATHER_MERGE_VMAS 525 526config MMU_GATHER_NO_FLUSH_CACHE 527 bool 528 529config MMU_GATHER_MERGE_VMAS 530 bool 531 532config MMU_GATHER_NO_GATHER 533 bool 534 depends on MMU_GATHER_TABLE_FREE 535 536config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 537 bool 538 help 539 Temporary select until all architectures can be converted to have 540 irqs disabled over activate_mm. Architectures that do IPI based TLB 541 shootdowns should enable this. 542 543# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 544# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 545# to/from kernel threads when the same mm is running on a lot of CPUs (a large 546# multi-threaded application), by reducing contention on the mm refcount. 547# 548# This can be disabled if the architecture ensures no CPUs are using an mm as a 549# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 550# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 551# final exit(2) TLB flush, for example. 552# 553# To implement this, an arch *must*: 554# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 555# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 556# converted already). 557config MMU_LAZY_TLB_REFCOUNT 558 def_bool y 559 depends on !MMU_LAZY_TLB_SHOOTDOWN 560 561# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 562# mm as a lazy tlb beyond its last reference count, by shooting down these 563# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 564# be using the mm as a lazy tlb, so that they may switch themselves to using 565# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 566# may be using mm as a lazy tlb mm. 567# 568# To implement this, an arch *must*: 569# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 570# at least all possible CPUs in which the mm is lazy. 571# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 572config MMU_LAZY_TLB_SHOOTDOWN 573 bool 574 575config ARCH_HAVE_NMI_SAFE_CMPXCHG 576 bool 577 578config ARCH_HAVE_EXTRA_ELF_NOTES 579 bool 580 help 581 An architecture should select this in order to enable adding an 582 arch-specific ELF note section to core files. It must provide two 583 functions: elf_coredump_extra_notes_size() and 584 elf_coredump_extra_notes_write() which are invoked by the ELF core 585 dumper. 586 587config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 588 bool 589 590config HAVE_ALIGNED_STRUCT_PAGE 591 bool 592 help 593 This makes sure that struct pages are double word aligned and that 594 e.g. the SLUB allocator can perform double word atomic operations 595 on a struct page for better performance. However selecting this 596 might increase the size of a struct page by a word. 597 598config HAVE_CMPXCHG_LOCAL 599 bool 600 601config HAVE_CMPXCHG_DOUBLE 602 bool 603 604config ARCH_WEAK_RELEASE_ACQUIRE 605 bool 606 607config ARCH_WANT_IPC_PARSE_VERSION 608 bool 609 610config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 611 bool 612 613config ARCH_WANT_OLD_COMPAT_IPC 614 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 615 bool 616 617config HAVE_ARCH_SECCOMP 618 bool 619 help 620 An arch should select this symbol to support seccomp mode 1 (the fixed 621 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 622 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 623 - __NR_seccomp_read_32 624 - __NR_seccomp_write_32 625 - __NR_seccomp_exit_32 626 - __NR_seccomp_sigreturn_32 627 628config HAVE_ARCH_SECCOMP_FILTER 629 bool 630 select HAVE_ARCH_SECCOMP 631 help 632 An arch should select this symbol if it provides all of these things: 633 - all the requirements for HAVE_ARCH_SECCOMP 634 - syscall_get_arch() 635 - syscall_get_arguments() 636 - syscall_rollback() 637 - syscall_set_return_value() 638 - SIGSYS siginfo_t support 639 - secure_computing is called from a ptrace_event()-safe context 640 - secure_computing return value is checked and a return value of -1 641 results in the system call being skipped immediately. 642 - seccomp syscall wired up 643 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 644 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 645 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 646 647config SECCOMP 648 prompt "Enable seccomp to safely execute untrusted bytecode" 649 def_bool y 650 depends on HAVE_ARCH_SECCOMP 651 help 652 This kernel feature is useful for number crunching applications 653 that may need to handle untrusted bytecode during their 654 execution. By using pipes or other transports made available 655 to the process as file descriptors supporting the read/write 656 syscalls, it's possible to isolate those applications in their 657 own address space using seccomp. Once seccomp is enabled via 658 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 659 disabled and the task is only allowed to execute a few safe 660 syscalls defined by each seccomp mode. 661 662 If unsure, say Y. 663 664config SECCOMP_FILTER 665 def_bool y 666 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 667 help 668 Enable tasks to build secure computing environments defined 669 in terms of Berkeley Packet Filter programs which implement 670 task-defined system call filtering polices. 671 672 See Documentation/userspace-api/seccomp_filter.rst for details. 673 674config SECCOMP_CACHE_DEBUG 675 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 676 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 677 depends on PROC_FS 678 help 679 This enables the /proc/pid/seccomp_cache interface to monitor 680 seccomp cache data. The file format is subject to change. Reading 681 the file requires CAP_SYS_ADMIN. 682 683 This option is for debugging only. Enabling presents the risk that 684 an adversary may be able to infer the seccomp filter logic. 685 686 If unsure, say N. 687 688config HAVE_ARCH_KSTACK_ERASE 689 bool 690 help 691 An architecture should select this if it has the code which 692 fills the used part of the kernel stack with the KSTACK_ERASE_POISON 693 value before returning from system calls. 694 695config HAVE_STACKPROTECTOR 696 bool 697 help 698 An arch should select this symbol if: 699 - it has implemented a stack canary (e.g. __stack_chk_guard) 700 701config STACKPROTECTOR 702 bool "Stack Protector buffer overflow detection" 703 depends on HAVE_STACKPROTECTOR 704 depends on $(cc-option,-fstack-protector) 705 default y 706 help 707 This option turns on the "stack-protector" GCC feature. This 708 feature puts, at the beginning of functions, a canary value on 709 the stack just before the return address, and validates 710 the value just before actually returning. Stack based buffer 711 overflows (that need to overwrite this return address) now also 712 overwrite the canary, which gets detected and the attack is then 713 neutralized via a kernel panic. 714 715 Functions will have the stack-protector canary logic added if they 716 have an 8-byte or larger character array on the stack. 717 718 This feature requires gcc version 4.2 or above, or a distribution 719 gcc with the feature backported ("-fstack-protector"). 720 721 On an x86 "defconfig" build, this feature adds canary checks to 722 about 3% of all kernel functions, which increases kernel code size 723 by about 0.3%. 724 725config STACKPROTECTOR_STRONG 726 bool "Strong Stack Protector" 727 depends on STACKPROTECTOR 728 depends on $(cc-option,-fstack-protector-strong) 729 default y 730 help 731 Functions will have the stack-protector canary logic added in any 732 of the following conditions: 733 734 - local variable's address used as part of the right hand side of an 735 assignment or function argument 736 - local variable is an array (or union containing an array), 737 regardless of array type or length 738 - uses register local variables 739 740 This feature requires gcc version 4.9 or above, or a distribution 741 gcc with the feature backported ("-fstack-protector-strong"). 742 743 On an x86 "defconfig" build, this feature adds canary checks to 744 about 20% of all kernel functions, which increases the kernel code 745 size by about 2%. 746 747config ARCH_SUPPORTS_SHADOW_CALL_STACK 748 bool 749 help 750 An architecture should select this if it supports the compiler's 751 Shadow Call Stack and implements runtime support for shadow stack 752 switching. 753 754config SHADOW_CALL_STACK 755 bool "Shadow Call Stack" 756 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 757 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 758 depends on MMU 759 help 760 This option enables the compiler's Shadow Call Stack, which 761 uses a shadow stack to protect function return addresses from 762 being overwritten by an attacker. More information can be found 763 in the compiler's documentation: 764 765 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 766 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 767 768 Note that security guarantees in the kernel differ from the 769 ones documented for user space. The kernel must store addresses 770 of shadow stacks in memory, which means an attacker capable of 771 reading and writing arbitrary memory may be able to locate them 772 and hijack control flow by modifying the stacks. 773 774config DYNAMIC_SCS 775 bool 776 help 777 Set by the arch code if it relies on code patching to insert the 778 shadow call stack push and pop instructions rather than on the 779 compiler. 780 781config LTO 782 bool 783 help 784 Selected if the kernel will be built using the compiler's LTO feature. 785 786config LTO_CLANG 787 bool 788 select LTO 789 help 790 Selected if the kernel will be built using Clang's LTO feature. 791 792config ARCH_SUPPORTS_LTO_CLANG 793 bool 794 help 795 An architecture should select this option if it supports: 796 - compiling with Clang, 797 - compiling inline assembly with Clang's integrated assembler, 798 - and linking with LLD. 799 800config ARCH_SUPPORTS_LTO_CLANG_THIN 801 bool 802 help 803 An architecture should select this option if it can support Clang's 804 ThinLTO mode. 805 806config HAS_LTO_CLANG 807 def_bool y 808 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 809 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 810 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 811 depends on ARCH_SUPPORTS_LTO_CLANG 812 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 813 # https://github.com/ClangBuiltLinux/linux/issues/1721 814 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 815 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 816 depends on !GCOV_KERNEL 817 help 818 The compiler and Kconfig options support building with Clang's 819 LTO. 820 821choice 822 prompt "Link Time Optimization (LTO)" 823 default LTO_NONE 824 help 825 This option enables Link Time Optimization (LTO), which allows the 826 compiler to optimize binaries globally. 827 828 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 829 so it's disabled by default. 830 831config LTO_NONE 832 bool "None" 833 help 834 Build the kernel normally, without Link Time Optimization (LTO). 835 836config LTO_CLANG_FULL 837 bool "Clang Full LTO (EXPERIMENTAL)" 838 depends on HAS_LTO_CLANG 839 depends on !COMPILE_TEST 840 select LTO_CLANG 841 help 842 This option enables Clang's full Link Time Optimization (LTO), which 843 allows the compiler to optimize the kernel globally. If you enable 844 this option, the compiler generates LLVM bitcode instead of ELF 845 object files, and the actual compilation from bitcode happens at 846 the LTO link step, which may take several minutes depending on the 847 kernel configuration. More information can be found from LLVM's 848 documentation: 849 850 https://llvm.org/docs/LinkTimeOptimization.html 851 852 During link time, this option can use a large amount of RAM, and 853 may take much longer than the ThinLTO option. 854 855config LTO_CLANG_THIN 856 bool "Clang ThinLTO (EXPERIMENTAL)" 857 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 858 select LTO_CLANG 859 help 860 This option enables Clang's ThinLTO, which allows for parallel 861 optimization and faster incremental compiles compared to the 862 CONFIG_LTO_CLANG_FULL option. More information can be found 863 from Clang's documentation: 864 865 https://clang.llvm.org/docs/ThinLTO.html 866 867 If unsure, say Y. 868endchoice 869 870config ARCH_SUPPORTS_AUTOFDO_CLANG 871 bool 872 873config AUTOFDO_CLANG 874 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 875 depends on ARCH_SUPPORTS_AUTOFDO_CLANG 876 depends on CC_IS_CLANG && CLANG_VERSION >= 170000 877 help 878 This option enables Clang’s AutoFDO build. When 879 an AutoFDO profile is specified in variable 880 CLANG_AUTOFDO_PROFILE during the build process, 881 Clang uses the profile to optimize the kernel. 882 883 If no profile is specified, AutoFDO options are 884 still passed to Clang to facilitate the collection 885 of perf data for creating an AutoFDO profile in 886 subsequent builds. 887 888 If unsure, say N. 889 890config ARCH_SUPPORTS_PROPELLER_CLANG 891 bool 892 893config PROPELLER_CLANG 894 bool "Enable Clang's Propeller build" 895 depends on ARCH_SUPPORTS_PROPELLER_CLANG 896 depends on CC_IS_CLANG && CLANG_VERSION >= 190000 897 help 898 This option enables Clang’s Propeller build. When the Propeller 899 profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX 900 during the build process, Clang uses the profiles to optimize 901 the kernel. 902 903 If no profile is specified, Propeller options are still passed 904 to Clang to facilitate the collection of perf data for creating 905 the Propeller profiles in subsequent builds. 906 907 If unsure, say N. 908 909config ARCH_SUPPORTS_CFI 910 bool 911 help 912 An architecture should select this option if it can support Kernel 913 Control-Flow Integrity (CFI) checking (-fsanitize=kcfi). 914 915config ARCH_USES_CFI_TRAPS 916 bool 917 help 918 An architecture should select this option if it requires the 919 .kcfi_traps section for KCFI trap handling. 920 921config ARCH_USES_CFI_GENERIC_LLVM_PASS 922 bool 923 help 924 An architecture should select this option if it uses the generic 925 KCFIPass in LLVM to expand kCFI bundles instead of architecture-specific 926 lowering. 927 928config CFI 929 bool "Use Kernel Control Flow Integrity (kCFI)" 930 default CFI_CLANG 931 depends on ARCH_SUPPORTS_CFI 932 depends on $(cc-option,-fsanitize=kcfi) 933 help 934 This option enables forward-edge Control Flow Integrity (CFI) 935 checking, where the compiler injects a runtime check to each 936 indirect function call to ensure the target is a valid function with 937 the correct static type. This restricts possible call targets and 938 makes it more difficult for an attacker to exploit bugs that allow 939 the modification of stored function pointers. More information can be 940 found from Clang's documentation: 941 942 https://clang.llvm.org/docs/ControlFlowIntegrity.html 943 944config CFI_CLANG 945 bool 946 transitional 947 help 948 Transitional config for CFI_CLANG to CFI migration. 949 950config CFI_ICALL_NORMALIZE_INTEGERS 951 bool "Normalize CFI tags for integers" 952 depends on CFI 953 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS 954 help 955 This option normalizes the CFI tags for integer types so that all 956 integer types of the same size and signedness receive the same CFI 957 tag. 958 959 The option is separate from CONFIG_RUST because it affects the ABI. 960 When working with build systems that care about the ABI, it is 961 convenient to be able to turn on this flag first, before Rust is 962 turned on. 963 964 This option is necessary for using CFI with Rust. If unsure, say N. 965 966config HAVE_CFI_ICALL_NORMALIZE_INTEGERS 967 def_bool y 968 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 969 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 970 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 971 972config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 973 def_bool y 974 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS 975 depends on ARM64 || X86_64 976 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 977 depends on RUSTC_LLVM_VERSION >= 190103 || \ 978 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 979 980config CFI_PERMISSIVE 981 bool "Use CFI in permissive mode" 982 depends on CFI 983 help 984 When selected, Control Flow Integrity (CFI) violations result in a 985 warning instead of a kernel panic. This option should only be used 986 for finding indirect call type mismatches during development. 987 988 If unsure, say N. 989 990config HAVE_ARCH_WITHIN_STACK_FRAMES 991 bool 992 help 993 An architecture should select this if it can walk the kernel stack 994 frames to determine if an object is part of either the arguments 995 or local variables (i.e. that it excludes saved return addresses, 996 and similar) by implementing an inline arch_within_stack_frames(), 997 which is used by CONFIG_HARDENED_USERCOPY. 998 999config HAVE_CONTEXT_TRACKING_USER 1000 bool 1001 help 1002 Provide kernel/user boundaries probes necessary for subsystems 1003 that need it, such as userspace RCU extended quiescent state. 1004 Syscalls need to be wrapped inside user_exit()-user_enter(), either 1005 optimized behind static key or through the slow path using TIF_NOHZ 1006 flag. Exceptions handlers must be wrapped as well. Irqs are already 1007 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 1008 handling on irq exit still need to be protected. 1009 1010config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 1011 bool 1012 help 1013 Architecture neither relies on exception_enter()/exception_exit() 1014 nor on schedule_user(). Also preempt_schedule_notrace() and 1015 preempt_schedule_irq() can't be called in a preemptible section 1016 while context tracking is CT_STATE_USER. This feature reflects a sane 1017 entry implementation where the following requirements are met on 1018 critical entry code, ie: before user_exit() or after user_enter(): 1019 1020 - Critical entry code isn't preemptible (or better yet: 1021 not interruptible). 1022 - No use of RCU read side critical sections, unless ct_nmi_enter() 1023 got called. 1024 - No use of instrumentation, unless instrumentation_begin() got 1025 called. 1026 1027config HAVE_TIF_NOHZ 1028 bool 1029 help 1030 Arch relies on TIF_NOHZ and syscall slow path to implement context 1031 tracking calls to user_enter()/user_exit(). 1032 1033config HAVE_VIRT_CPU_ACCOUNTING 1034 bool 1035 1036config HAVE_VIRT_CPU_ACCOUNTING_IDLE 1037 bool 1038 help 1039 Architecture has its own way to account idle CPU time and therefore 1040 doesn't implement vtime_account_idle(). 1041 1042config ARCH_HAS_SCALED_CPUTIME 1043 bool 1044 1045config HAVE_VIRT_CPU_ACCOUNTING_GEN 1046 bool 1047 default y if 64BIT 1048 help 1049 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 1050 Before enabling this option, arch code must be audited 1051 to ensure there are no races in concurrent read/write of 1052 cputime_t. For example, reading/writing 64-bit cputime_t on 1053 some 32-bit arches may require multiple accesses, so proper 1054 locking is needed to protect against concurrent accesses. 1055 1056config HAVE_IRQ_TIME_ACCOUNTING 1057 bool 1058 help 1059 Archs need to ensure they use a high enough resolution clock to 1060 support irq time accounting and then call enable_sched_clock_irqtime(). 1061 1062config HAVE_PV_STEAL_CLOCK_GEN 1063 bool 1064 1065config HAVE_MOVE_PUD 1066 bool 1067 help 1068 Architectures that select this are able to move page tables at the 1069 PUD level. If there are only 3 page table levels, the move effectively 1070 happens at the PGD level. 1071 1072config HAVE_MOVE_PMD 1073 bool 1074 help 1075 Archs that select this are able to move page tables at the PMD level. 1076 1077config HAVE_ARCH_TRANSPARENT_HUGEPAGE 1078 bool 1079 1080config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1081 bool 1082 1083config HAVE_ARCH_HUGE_VMAP 1084 bool 1085 1086# 1087# Archs that select this would be capable of PMD-sized vmaps (i.e., 1088# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 1089# must be used to enable allocations to use hugepages. 1090# 1091config HAVE_ARCH_HUGE_VMALLOC 1092 depends on HAVE_ARCH_HUGE_VMAP 1093 bool 1094 1095config ARCH_WANT_HUGE_PMD_SHARE 1096 bool 1097 1098# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1099# if there are no userspace memory management features that use it 1100config ARCH_WANT_KERNEL_PMD_MKWRITE 1101 bool 1102 1103config ARCH_WANT_PMD_MKWRITE 1104 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1105 1106config HAVE_ARCH_SOFT_DIRTY 1107 bool 1108 1109config HAVE_MOD_ARCH_SPECIFIC 1110 bool 1111 help 1112 The arch uses struct mod_arch_specific to store data. Many arches 1113 just need a simple module loader without arch specific data - those 1114 should not enable this. 1115 1116config MODULES_USE_ELF_RELA 1117 bool 1118 help 1119 Modules only use ELF RELA relocations. Modules with ELF REL 1120 relocations will give an error. 1121 1122config MODULES_USE_ELF_REL 1123 bool 1124 help 1125 Modules only use ELF REL relocations. Modules with ELF RELA 1126 relocations will give an error. 1127 1128config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1129 bool 1130 help 1131 For architectures like powerpc/32 which have constraints on module 1132 allocation and need to allocate module data outside of module area. 1133 1134config ARCH_WANTS_MODULES_TEXT_SECTIONS 1135 bool 1136 help 1137 For architectures like 32-bit parisc which require that functions in 1138 modules have to keep code in own text sections (-ffunction-sections) 1139 and to avoid merging all text into one big text section, 1140 1141config ARCH_WANTS_EXECMEM_LATE 1142 bool 1143 help 1144 For architectures that do not allocate executable memory early on 1145 boot, but rather require its initialization late when there is 1146 enough entropy for module space randomization, for instance 1147 arm64. 1148 1149config ARCH_HAS_EXECMEM_ROX 1150 bool 1151 depends on MMU && !HIGHMEM 1152 help 1153 For architectures that support allocations of executable memory 1154 with read-only execute permissions. Architecture must implement 1155 execmem_fill_trapping_insns() callback to enable this. 1156 1157config HAVE_IRQ_EXIT_ON_IRQ_STACK 1158 bool 1159 help 1160 Architecture doesn't only execute the irq handler on the irq stack 1161 but also irq_exit(). This way we can process softirqs on this irq 1162 stack instead of switching to a new one when we call __do_softirq() 1163 in the end of an hardirq. 1164 This spares a stack switch and improves cache usage on softirq 1165 processing. 1166 1167config HAVE_SOFTIRQ_ON_OWN_STACK 1168 bool 1169 help 1170 Architecture provides a function to run __do_softirq() on a 1171 separate stack. 1172 1173config SOFTIRQ_ON_OWN_STACK 1174 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1175 1176config ALTERNATE_USER_ADDRESS_SPACE 1177 bool 1178 help 1179 Architectures set this when the CPU uses separate address 1180 spaces for kernel and user space pointers. In this case, the 1181 access_ok() check on a __user pointer is skipped. 1182 1183config PGTABLE_LEVELS 1184 int 1185 default 2 1186 1187config ARCH_HAS_ELF_RANDOMIZE 1188 bool 1189 help 1190 An architecture supports choosing randomized locations for 1191 stack, mmap, brk, and ET_DYN. Defined functions: 1192 - arch_mmap_rnd() 1193 - arch_randomize_brk() 1194 1195config HAVE_ARCH_MMAP_RND_BITS 1196 bool 1197 help 1198 An arch should select this symbol if it supports setting a variable 1199 number of bits for use in establishing the base address for mmap 1200 allocations, has MMU enabled and provides values for both: 1201 - ARCH_MMAP_RND_BITS_MIN 1202 - ARCH_MMAP_RND_BITS_MAX 1203 1204config HAVE_EXIT_THREAD 1205 bool 1206 help 1207 An architecture implements exit_thread. 1208 1209config ARCH_MMAP_RND_BITS_MIN 1210 int 1211 1212config ARCH_MMAP_RND_BITS_MAX 1213 int 1214 1215config ARCH_MMAP_RND_BITS_DEFAULT 1216 int 1217 1218config ARCH_MMAP_RND_BITS 1219 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1220 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1221 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1222 default ARCH_MMAP_RND_BITS_MIN 1223 depends on HAVE_ARCH_MMAP_RND_BITS 1224 help 1225 This value can be used to select the number of bits to use to 1226 determine the random offset to the base address of vma regions 1227 resulting from mmap allocations. This value will be bounded 1228 by the architecture's minimum and maximum supported values. 1229 1230 This value can be changed after boot using the 1231 /proc/sys/vm/mmap_rnd_bits tunable 1232 1233config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1234 bool 1235 help 1236 An arch should select this symbol if it supports running applications 1237 in compatibility mode, supports setting a variable number of bits for 1238 use in establishing the base address for mmap allocations, has MMU 1239 enabled and provides values for both: 1240 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1241 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1242 1243config ARCH_MMAP_RND_COMPAT_BITS_MIN 1244 int 1245 1246config ARCH_MMAP_RND_COMPAT_BITS_MAX 1247 int 1248 1249config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1250 int 1251 1252config ARCH_MMAP_RND_COMPAT_BITS 1253 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1254 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1255 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1256 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1257 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1258 help 1259 This value can be used to select the number of bits to use to 1260 determine the random offset to the base address of vma regions 1261 resulting from mmap allocations for compatible applications This 1262 value will be bounded by the architecture's minimum and maximum 1263 supported values. 1264 1265 This value can be changed after boot using the 1266 /proc/sys/vm/mmap_rnd_compat_bits tunable 1267 1268config HAVE_ARCH_COMPAT_MMAP_BASES 1269 bool 1270 help 1271 This allows 64bit applications to invoke 32-bit mmap() syscall 1272 and vice-versa 32-bit applications to call 64-bit mmap(). 1273 Required for applications doing different bitness syscalls. 1274 1275config HAVE_PAGE_SIZE_4KB 1276 bool 1277 1278config HAVE_PAGE_SIZE_8KB 1279 bool 1280 1281config HAVE_PAGE_SIZE_16KB 1282 bool 1283 1284config HAVE_PAGE_SIZE_32KB 1285 bool 1286 1287config HAVE_PAGE_SIZE_64KB 1288 bool 1289 1290config HAVE_PAGE_SIZE_256KB 1291 bool 1292 1293choice 1294 prompt "MMU page size" 1295 1296config PAGE_SIZE_4KB 1297 bool "4KiB pages" 1298 depends on HAVE_PAGE_SIZE_4KB 1299 help 1300 This option select the standard 4KiB Linux page size and the only 1301 available option on many architectures. Using 4KiB page size will 1302 minimize memory consumption and is therefore recommended for low 1303 memory systems. 1304 Some software that is written for x86 systems makes incorrect 1305 assumptions about the page size and only runs on 4KiB pages. 1306 1307config PAGE_SIZE_8KB 1308 bool "8KiB pages" 1309 depends on HAVE_PAGE_SIZE_8KB 1310 help 1311 This option is the only supported page size on a few older 1312 processors, and can be slightly faster than 4KiB pages. 1313 1314config PAGE_SIZE_16KB 1315 bool "16KiB pages" 1316 depends on HAVE_PAGE_SIZE_16KB 1317 help 1318 This option is usually a good compromise between memory 1319 consumption and performance for typical desktop and server 1320 workloads, often saving a level of page table lookups compared 1321 to 4KB pages as well as reducing TLB pressure and overhead of 1322 per-page operations in the kernel at the expense of a larger 1323 page cache. 1324 1325config PAGE_SIZE_32KB 1326 bool "32KiB pages" 1327 depends on HAVE_PAGE_SIZE_32KB 1328 help 1329 Using 32KiB page size will result in slightly higher performance 1330 kernel at the price of higher memory consumption compared to 1331 16KiB pages. This option is available only on cnMIPS cores. 1332 Note that you will need a suitable Linux distribution to 1333 support this. 1334 1335config PAGE_SIZE_64KB 1336 bool "64KiB pages" 1337 depends on HAVE_PAGE_SIZE_64KB 1338 help 1339 Using 64KiB page size will result in slightly higher performance 1340 kernel at the price of much higher memory consumption compared to 1341 4KiB or 16KiB pages. 1342 This is not suitable for general-purpose workloads but the 1343 better performance may be worth the cost for certain types of 1344 supercomputing or database applications that work mostly with 1345 large in-memory data rather than small files. 1346 1347config PAGE_SIZE_256KB 1348 bool "256KiB pages" 1349 depends on HAVE_PAGE_SIZE_256KB 1350 help 1351 256KiB pages have little practical value due to their extreme 1352 memory usage. The kernel will only be able to run applications 1353 that have been compiled with '-zmax-page-size' set to 256KiB 1354 (the default is 64KiB or 4KiB on most architectures). 1355 1356endchoice 1357 1358config PAGE_SIZE_LESS_THAN_64KB 1359 def_bool y 1360 depends on !PAGE_SIZE_64KB 1361 depends on PAGE_SIZE_LESS_THAN_256KB 1362 1363config PAGE_SIZE_LESS_THAN_256KB 1364 def_bool y 1365 depends on !PAGE_SIZE_256KB 1366 1367config PAGE_SHIFT 1368 int 1369 default 12 if PAGE_SIZE_4KB 1370 default 13 if PAGE_SIZE_8KB 1371 default 14 if PAGE_SIZE_16KB 1372 default 15 if PAGE_SIZE_32KB 1373 default 16 if PAGE_SIZE_64KB 1374 default 18 if PAGE_SIZE_256KB 1375 1376# This allows to use a set of generic functions to determine mmap base 1377# address by giving priority to top-down scheme only if the process 1378# is not in legacy mode (compat task, unlimited stack size or 1379# sysctl_legacy_va_layout). 1380# Architecture that selects this option can provide its own version of: 1381# - STACK_RND_MASK 1382config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1383 bool 1384 depends on MMU 1385 select ARCH_HAS_ELF_RANDOMIZE 1386 1387config HAVE_OBJTOOL 1388 bool 1389 1390config HAVE_JUMP_LABEL_HACK 1391 bool 1392 1393config HAVE_NOINSTR_HACK 1394 bool 1395 1396config HAVE_NOINSTR_VALIDATION 1397 bool 1398 1399config HAVE_UACCESS_VALIDATION 1400 bool 1401 select OBJTOOL 1402 1403config HAVE_STACK_VALIDATION 1404 bool 1405 help 1406 Architecture supports objtool compile-time frame pointer rule 1407 validation. 1408 1409config HAVE_RELIABLE_STACKTRACE 1410 bool 1411 help 1412 Architecture has either save_stack_trace_tsk_reliable() or 1413 arch_stack_walk_reliable() function which only returns a stack trace 1414 if it can guarantee the trace is reliable. 1415 1416config HAVE_ARCH_HASH 1417 bool 1418 default n 1419 help 1420 If this is set, the architecture provides an <asm/hash.h> 1421 file which provides platform-specific implementations of some 1422 functions in <linux/hash.h> or fs/namei.c. 1423 1424config HAVE_ARCH_NVRAM_OPS 1425 bool 1426 1427config ISA_BUS_API 1428 def_bool ISA 1429 1430# 1431# ABI hall of shame 1432# 1433config CLONE_BACKWARDS 1434 bool 1435 help 1436 Architecture has tls passed as the 4th argument of clone(2), 1437 not the 5th one. 1438 1439config CLONE_BACKWARDS2 1440 bool 1441 help 1442 Architecture has the first two arguments of clone(2) swapped. 1443 1444config CLONE_BACKWARDS3 1445 bool 1446 help 1447 Architecture has tls passed as the 3rd argument of clone(2), 1448 not the 5th one. 1449 1450config ODD_RT_SIGACTION 1451 bool 1452 help 1453 Architecture has unusual rt_sigaction(2) arguments 1454 1455config OLD_SIGSUSPEND 1456 bool 1457 help 1458 Architecture has old sigsuspend(2) syscall, of one-argument variety 1459 1460config OLD_SIGSUSPEND3 1461 bool 1462 help 1463 Even weirder antique ABI - three-argument sigsuspend(2) 1464 1465config OLD_SIGACTION 1466 bool 1467 help 1468 Architecture has old sigaction(2) syscall. Nope, not the same 1469 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1470 but fairly different variant of sigaction(2), thanks to OSF/1 1471 compatibility... 1472 1473config COMPAT_OLD_SIGACTION 1474 bool 1475 1476config COMPAT_32BIT_TIME 1477 bool "Provide system calls for 32-bit time_t" 1478 default !64BIT || COMPAT 1479 help 1480 This enables 32 bit time_t support in addition to 64 bit time_t support. 1481 This is relevant on all 32-bit architectures, and 64-bit architectures 1482 as part of compat syscall handling. 1483 1484config ARCH_NO_PREEMPT 1485 bool 1486 1487config ARCH_SUPPORTS_RT 1488 bool 1489 1490config CPU_NO_EFFICIENT_FFS 1491 def_bool n 1492 1493config HAVE_ARCH_VMAP_STACK 1494 def_bool n 1495 help 1496 An arch should select this symbol if it can support kernel stacks 1497 in vmalloc space. This means: 1498 1499 - vmalloc space must be large enough to hold many kernel stacks. 1500 This may rule out many 32-bit architectures. 1501 1502 - Stacks in vmalloc space need to work reliably. For example, if 1503 vmap page tables are created on demand, either this mechanism 1504 needs to work while the stack points to a virtual address with 1505 unpopulated page tables or arch code (switch_to() and switch_mm(), 1506 most likely) needs to ensure that the stack's page table entries 1507 are populated before running on a possibly unpopulated stack. 1508 1509 - If the stack overflows into a guard page, something reasonable 1510 should happen. The definition of "reasonable" is flexible, but 1511 instantly rebooting without logging anything would be unfriendly. 1512 1513config VMAP_STACK 1514 default y 1515 bool "Use a virtually-mapped stack" 1516 depends on HAVE_ARCH_VMAP_STACK 1517 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1518 help 1519 Enable this if you want the use virtually-mapped kernel stacks 1520 with guard pages. This causes kernel stack overflows to be 1521 caught immediately rather than causing difficult-to-diagnose 1522 corruption. 1523 1524 To use this with software KASAN modes, the architecture must support 1525 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1526 must be enabled. 1527 1528config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1529 def_bool n 1530 help 1531 An arch should select this symbol if it can support kernel stack 1532 offset randomization with a call to add_random_kstack_offset() 1533 during syscall entry. Careful removal of -fstack-protector-strong and 1534 -fstack-protector should also be applied to the entry code and 1535 closely examined, as the artificial stack bump looks like an array 1536 to the compiler, so it will attempt to add canary checks regardless 1537 of the static branch state. 1538 1539config RANDOMIZE_KSTACK_OFFSET 1540 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1541 default y 1542 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1543 help 1544 The kernel stack offset can be randomized (after pt_regs) by 1545 roughly 5 bits of entropy, frustrating memory corruption 1546 attacks that depend on stack address determinism or 1547 cross-syscall address exposures. 1548 1549 The feature is controlled via the "randomize_kstack_offset=on/off" 1550 kernel boot param, and if turned off has zero overhead due to its use 1551 of static branches (see JUMP_LABEL). 1552 1553 If unsure, say Y. 1554 1555config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1556 bool "Default state of kernel stack offset randomization" 1557 depends on RANDOMIZE_KSTACK_OFFSET 1558 help 1559 Kernel stack offset randomization is controlled by kernel boot param 1560 "randomize_kstack_offset=on/off", and this config chooses the default 1561 boot state. 1562 1563config ARCH_OPTIONAL_KERNEL_RWX 1564 def_bool n 1565 1566config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1567 def_bool n 1568 1569config ARCH_HAS_STRICT_KERNEL_RWX 1570 def_bool n 1571 1572config STRICT_KERNEL_RWX 1573 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1574 depends on ARCH_HAS_STRICT_KERNEL_RWX 1575 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1576 help 1577 If this is set, kernel text and rodata memory will be made read-only, 1578 and non-text memory will be made non-executable. This provides 1579 protection against certain security exploits (e.g. executing the heap 1580 or modifying text) 1581 1582 These features are considered standard security practice these days. 1583 You should say Y here in almost all cases. 1584 1585config ARCH_HAS_STRICT_MODULE_RWX 1586 def_bool n 1587 1588config STRICT_MODULE_RWX 1589 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1590 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1591 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1592 help 1593 If this is set, module text and rodata memory will be made read-only, 1594 and non-text memory will be made non-executable. This provides 1595 protection against certain security exploits (e.g. writing to text) 1596 1597# select if the architecture provides an asm/dma-direct.h header 1598config ARCH_HAS_PHYS_TO_DMA 1599 bool 1600 1601config ARCH_HAS_CPU_RESCTRL 1602 bool 1603 help 1604 An architecture selects this option to indicate that the necessary 1605 hooks are provided to support the common memory system usage 1606 monitoring and control interfaces provided by the 'resctrl' 1607 filesystem (see RESCTRL_FS). 1608 1609config HAVE_ARCH_COMPILER_H 1610 bool 1611 help 1612 An architecture can select this if it provides an 1613 asm/compiler.h header that should be included after 1614 linux/compiler-*.h in order to override macro definitions that those 1615 headers generally provide. 1616 1617config HAVE_ARCH_LIBGCC_H 1618 bool 1619 help 1620 An architecture can select this if it provides an 1621 asm/libgcc.h header that should be included after 1622 linux/libgcc.h in order to override macro definitions that 1623 header generally provides. 1624 1625config HAVE_ARCH_PREL32_RELOCATIONS 1626 bool 1627 help 1628 May be selected by an architecture if it supports place-relative 1629 32-bit relocations, both in the toolchain and in the module loader, 1630 in which case relative references can be used in special sections 1631 for PCI fixup, initcalls etc which are only half the size on 64 bit 1632 architectures, and don't require runtime relocation on relocatable 1633 kernels. 1634 1635config ARCH_USE_MEMREMAP_PROT 1636 bool 1637 1638config LOCK_EVENT_COUNTS 1639 bool "Locking event counts collection" 1640 depends on DEBUG_FS 1641 help 1642 Enable light-weight counting of various locking related events 1643 in the system with minimal performance impact. This reduces 1644 the chance of application behavior change because of timing 1645 differences. The counts are reported via debugfs. 1646 1647# Select if the architecture has support for applying RELR relocations. 1648config ARCH_HAS_RELR 1649 bool 1650 1651config RELR 1652 bool "Use RELR relocation packing" 1653 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1654 default y 1655 help 1656 Store the kernel's dynamic relocations in the RELR relocation packing 1657 format. Requires a compatible linker (LLD supports this feature), as 1658 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1659 are compatible). 1660 1661config ARCH_HAS_MEM_ENCRYPT 1662 bool 1663 1664config ARCH_HAS_CC_PLATFORM 1665 bool 1666 1667config HAVE_SPARSE_SYSCALL_NR 1668 bool 1669 help 1670 An architecture should select this if its syscall numbering is sparse 1671 to save space. For example, MIPS architecture has a syscall array with 1672 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1673 related optimizations for a given architecture. 1674 1675config ARCH_HAS_VDSO_ARCH_DATA 1676 depends on HAVE_GENERIC_VDSO 1677 bool 1678 1679config ARCH_HAS_VDSO_TIME_DATA 1680 bool 1681 1682config HAVE_STATIC_CALL 1683 bool 1684 1685config HAVE_STATIC_CALL_INLINE 1686 bool 1687 depends on HAVE_STATIC_CALL 1688 select OBJTOOL 1689 1690config HAVE_PREEMPT_DYNAMIC 1691 bool 1692 1693config HAVE_PREEMPT_DYNAMIC_CALL 1694 bool 1695 depends on HAVE_STATIC_CALL 1696 select HAVE_PREEMPT_DYNAMIC 1697 help 1698 An architecture should select this if it can handle the preemption 1699 model being selected at boot time using static calls. 1700 1701 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1702 preemption function will be patched directly. 1703 1704 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1705 call to a preemption function will go through a trampoline, and the 1706 trampoline will be patched. 1707 1708 It is strongly advised to support inline static call to avoid any 1709 overhead. 1710 1711config HAVE_PREEMPT_DYNAMIC_KEY 1712 bool 1713 depends on HAVE_ARCH_JUMP_LABEL 1714 select HAVE_PREEMPT_DYNAMIC 1715 help 1716 An architecture should select this if it can handle the preemption 1717 model being selected at boot time using static keys. 1718 1719 Each preemption function will be given an early return based on a 1720 static key. This should have slightly lower overhead than non-inline 1721 static calls, as this effectively inlines each trampoline into the 1722 start of its callee. This may avoid redundant work, and may 1723 integrate better with CFI schemes. 1724 1725 This will have greater overhead than using inline static calls as 1726 the call to the preemption function cannot be entirely elided. 1727 1728config ARCH_WANT_LD_ORPHAN_WARN 1729 bool 1730 help 1731 An arch should select this symbol once all linker sections are explicitly 1732 included, size-asserted, or discarded in the linker scripts. This is 1733 important because we never want expected sections to be placed heuristically 1734 by the linker, since the locations of such sections can change between linker 1735 versions. 1736 1737config HAVE_ARCH_PFN_VALID 1738 bool 1739 1740config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1741 bool 1742 1743config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1744 bool 1745 1746config ARCH_SPLIT_ARG64 1747 bool 1748 help 1749 If a 32-bit architecture requires 64-bit arguments to be split into 1750 pairs of 32-bit arguments, select this option. 1751 1752config ARCH_HAS_ELFCORE_COMPAT 1753 bool 1754 1755config ARCH_HAS_PARANOID_L1D_FLUSH 1756 bool 1757 1758config ARCH_HAVE_TRACE_MMIO_ACCESS 1759 bool 1760 1761config DYNAMIC_SIGFRAME 1762 bool 1763 1764# Select, if arch has a named attribute group bound to NUMA device nodes. 1765config HAVE_ARCH_NODE_DEV_GROUP 1766 bool 1767 1768config ARCH_HAS_HW_PTE_YOUNG 1769 bool 1770 help 1771 Architectures that select this option are capable of setting the 1772 accessed bit in PTE entries when using them as part of linear address 1773 translations. Architectures that require runtime check should select 1774 this option and override arch_has_hw_pte_young(). 1775 1776config ARCH_HAS_NONLEAF_PMD_YOUNG 1777 bool 1778 help 1779 Architectures that select this option are capable of setting the 1780 accessed bit in non-leaf PMD entries when using them as part of linear 1781 address translations. Page table walkers that clear the accessed bit 1782 may use this capability to reduce their search space. 1783 1784config ARCH_HAS_KERNEL_FPU_SUPPORT 1785 bool 1786 help 1787 Architectures that select this option can run floating-point code in 1788 the kernel, as described in Documentation/core-api/floating-point.rst. 1789 1790config ARCH_VMLINUX_NEEDS_RELOCS 1791 bool 1792 help 1793 Whether the architecture needs vmlinux to be built with static 1794 relocations preserved. This is used by some architectures to 1795 construct bespoke relocation tables for KASLR. 1796 1797# Select if architecture uses the common generic TIF bits 1798config HAVE_GENERIC_TIF_BITS 1799 bool 1800 1801source "kernel/gcov/Kconfig" 1802 1803source "scripts/gcc-plugins/Kconfig" 1804 1805config FUNCTION_ALIGNMENT_4B 1806 bool 1807 1808config FUNCTION_ALIGNMENT_8B 1809 bool 1810 1811config FUNCTION_ALIGNMENT_16B 1812 bool 1813 1814config FUNCTION_ALIGNMENT_32B 1815 bool 1816 1817config FUNCTION_ALIGNMENT_64B 1818 bool 1819 1820config FUNCTION_ALIGNMENT 1821 int 1822 default 64 if FUNCTION_ALIGNMENT_64B 1823 default 32 if FUNCTION_ALIGNMENT_32B 1824 default 16 if FUNCTION_ALIGNMENT_16B 1825 default 8 if FUNCTION_ALIGNMENT_8B 1826 default 4 if FUNCTION_ALIGNMENT_4B 1827 default 0 1828 1829config CC_HAS_MIN_FUNCTION_ALIGNMENT 1830 # Detect availability of the GCC option -fmin-function-alignment which 1831 # guarantees minimal alignment for all functions, unlike 1832 # -falign-functions which the compiler ignores for cold functions. 1833 def_bool $(cc-option, -fmin-function-alignment=8) 1834 1835config CC_HAS_SANE_FUNCTION_ALIGNMENT 1836 # Set if the guaranteed alignment with -fmin-function-alignment is 1837 # available or extra care is required in the kernel. Clang provides 1838 # strict alignment always, even with -falign-functions. 1839 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1840 1841config ARCH_NEED_CMPXCHG_1_EMU 1842 bool 1843 1844config ARCH_WANTS_PRE_LINK_VMLINUX 1845 bool 1846 help 1847 An architecture can select this if it provides arch/<arch>/tools/Makefile 1848 with .arch.vmlinux.o target to be linked into vmlinux. 1849 1850config ARCH_HAS_CPU_ATTACK_VECTORS 1851 bool 1852 1853config HAVE_ARCH_GET_SECUREBOOT 1854 def_bool EFI 1855 1856endmenu 1857