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 20menu "General architecture-dependent options" 21 22config ARCH_HAS_SUBPAGE_FAULTS 23 bool 24 help 25 Select if the architecture can check permissions at sub-page 26 granularity (e.g. arm64 MTE). The probe_user_*() functions 27 must be implemented. 28 29config HOTPLUG_SMT 30 bool 31 32config SMT_NUM_THREADS_DYNAMIC 33 bool 34 35# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 36config HOTPLUG_CORE_SYNC 37 bool 38 39# Basic CPU dead synchronization selected by architecture 40config HOTPLUG_CORE_SYNC_DEAD 41 bool 42 select HOTPLUG_CORE_SYNC 43 44# Full CPU synchronization with alive state selected by architecture 45config HOTPLUG_CORE_SYNC_FULL 46 bool 47 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 48 select HOTPLUG_CORE_SYNC 49 50config HOTPLUG_SPLIT_STARTUP 51 bool 52 select HOTPLUG_CORE_SYNC_FULL 53 54config HOTPLUG_PARALLEL 55 bool 56 select HOTPLUG_SPLIT_STARTUP 57 58config GENERIC_ENTRY 59 bool 60 61config KPROBES 62 bool "Kprobes" 63 depends on MODULES 64 depends on HAVE_KPROBES 65 select KALLSYMS 66 select TASKS_RCU if PREEMPTION 67 help 68 Kprobes allows you to trap at almost any kernel address and 69 execute a callback function. register_kprobe() establishes 70 a probepoint and specifies the callback. Kprobes is useful 71 for kernel debugging, non-intrusive instrumentation and testing. 72 If in doubt, say "N". 73 74config JUMP_LABEL 75 bool "Optimize very unlikely/likely branches" 76 depends on HAVE_ARCH_JUMP_LABEL 77 select OBJTOOL if HAVE_JUMP_LABEL_HACK 78 help 79 This option enables a transparent branch optimization that 80 makes certain almost-always-true or almost-always-false branch 81 conditions even cheaper to execute within the kernel. 82 83 Certain performance-sensitive kernel code, such as trace points, 84 scheduler functionality, networking code and KVM have such 85 branches and include support for this optimization technique. 86 87 If it is detected that the compiler has support for "asm goto", 88 the kernel will compile such branches with just a nop 89 instruction. When the condition flag is toggled to true, the 90 nop will be converted to a jump instruction to execute the 91 conditional block of instructions. 92 93 This technique lowers overhead and stress on the branch prediction 94 of the processor and generally makes the kernel faster. The update 95 of the condition is slower, but those are always very rare. 96 97 ( On 32-bit x86, the necessary options added to the compiler 98 flags may increase the size of the kernel slightly. ) 99 100config STATIC_KEYS_SELFTEST 101 bool "Static key selftest" 102 depends on JUMP_LABEL 103 help 104 Boot time self-test of the branch patching code. 105 106config STATIC_CALL_SELFTEST 107 bool "Static call selftest" 108 depends on HAVE_STATIC_CALL 109 help 110 Boot time self-test of the call patching code. 111 112config OPTPROBES 113 def_bool y 114 depends on KPROBES && HAVE_OPTPROBES 115 select TASKS_RCU if PREEMPTION 116 117config KPROBES_ON_FTRACE 118 def_bool y 119 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 120 depends on DYNAMIC_FTRACE_WITH_REGS 121 help 122 If function tracer is enabled and the arch supports full 123 passing of pt_regs to function tracing, then kprobes can 124 optimize on top of function tracing. 125 126config UPROBES 127 def_bool n 128 depends on ARCH_SUPPORTS_UPROBES 129 help 130 Uprobes is the user-space counterpart to kprobes: they 131 enable instrumentation applications (such as 'perf probe') 132 to establish unintrusive probes in user-space binaries and 133 libraries, by executing handler functions when the probes 134 are hit by user-space applications. 135 136 ( These probes come in the form of single-byte breakpoints, 137 managed by the kernel and kept transparent to the probed 138 application. ) 139 140config HAVE_64BIT_ALIGNED_ACCESS 141 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 142 help 143 Some architectures require 64 bit accesses to be 64 bit 144 aligned, which also requires structs containing 64 bit values 145 to be 64 bit aligned too. This includes some 32 bit 146 architectures which can do 64 bit accesses, as well as 64 bit 147 architectures without unaligned access. 148 149 This symbol should be selected by an architecture if 64 bit 150 accesses are required to be 64 bit aligned in this way even 151 though it is not a 64 bit architecture. 152 153 See Documentation/core-api/unaligned-memory-access.rst for 154 more information on the topic of unaligned memory accesses. 155 156config HAVE_EFFICIENT_UNALIGNED_ACCESS 157 bool 158 help 159 Some architectures are unable to perform unaligned accesses 160 without the use of get_unaligned/put_unaligned. Others are 161 unable to perform such accesses efficiently (e.g. trap on 162 unaligned access and require fixing it up in the exception 163 handler.) 164 165 This symbol should be selected by an architecture if it can 166 perform unaligned accesses efficiently to allow different 167 code paths to be selected for these cases. Some network 168 drivers, for example, could opt to not fix up alignment 169 problems with received packets if doing so would not help 170 much. 171 172 See Documentation/core-api/unaligned-memory-access.rst for more 173 information on the topic of unaligned memory accesses. 174 175config ARCH_USE_BUILTIN_BSWAP 176 bool 177 help 178 Modern versions of GCC (since 4.4) have builtin functions 179 for handling byte-swapping. Using these, instead of the old 180 inline assembler that the architecture code provides in the 181 __arch_bswapXX() macros, allows the compiler to see what's 182 happening and offers more opportunity for optimisation. In 183 particular, the compiler will be able to combine the byteswap 184 with a nearby load or store and use load-and-swap or 185 store-and-swap instructions if the architecture has them. It 186 should almost *never* result in code which is worse than the 187 hand-coded assembler in <asm/swab.h>. But just in case it 188 does, the use of the builtins is optional. 189 190 Any architecture with load-and-swap or store-and-swap 191 instructions should set this. And it shouldn't hurt to set it 192 on architectures that don't have such instructions. 193 194config KRETPROBES 195 def_bool y 196 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 197 198config KRETPROBE_ON_RETHOOK 199 def_bool y 200 depends on HAVE_RETHOOK 201 depends on KRETPROBES 202 select RETHOOK 203 204config USER_RETURN_NOTIFIER 205 bool 206 depends on HAVE_USER_RETURN_NOTIFIER 207 help 208 Provide a kernel-internal notification when a cpu is about to 209 switch to user mode. 210 211config HAVE_IOREMAP_PROT 212 bool 213 214config HAVE_KPROBES 215 bool 216 217config HAVE_KRETPROBES 218 bool 219 220config HAVE_OPTPROBES 221 bool 222 223config HAVE_KPROBES_ON_FTRACE 224 bool 225 226config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 227 bool 228 help 229 Since kretprobes modifies return address on the stack, the 230 stacktrace may see the kretprobe trampoline address instead 231 of correct one. If the architecture stacktrace code and 232 unwinder can adjust such entries, select this configuration. 233 234config HAVE_FUNCTION_ERROR_INJECTION 235 bool 236 237config HAVE_NMI 238 bool 239 240config HAVE_FUNCTION_DESCRIPTORS 241 bool 242 243config TRACE_IRQFLAGS_SUPPORT 244 bool 245 246config TRACE_IRQFLAGS_NMI_SUPPORT 247 bool 248 249# 250# An arch should select this if it provides all these things: 251# 252# task_pt_regs() in asm/processor.h or asm/ptrace.h 253# arch_has_single_step() if there is hardware single-step support 254# arch_has_block_step() if there is hardware block-step support 255# asm/syscall.h supplying asm-generic/syscall.h interface 256# linux/regset.h user_regset interfaces 257# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 258# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 259# TIF_NOTIFY_RESUME calls resume_user_mode_work() 260# 261config HAVE_ARCH_TRACEHOOK 262 bool 263 264config HAVE_DMA_CONTIGUOUS 265 bool 266 267config GENERIC_SMP_IDLE_THREAD 268 bool 269 270config GENERIC_IDLE_POLL_SETUP 271 bool 272 273config ARCH_HAS_FORTIFY_SOURCE 274 bool 275 help 276 An architecture should select this when it can successfully 277 build and run with CONFIG_FORTIFY_SOURCE. 278 279# 280# Select if the arch provides a historic keepinit alias for the retain_initrd 281# command line option 282# 283config ARCH_HAS_KEEPINITRD 284 bool 285 286# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 287config ARCH_HAS_SET_MEMORY 288 bool 289 290# Select if arch has all set_direct_map_invalid/default() functions 291config ARCH_HAS_SET_DIRECT_MAP 292 bool 293 294# 295# Select if the architecture provides the arch_dma_set_uncached symbol to 296# either provide an uncached segment alias for a DMA allocation, or 297# to remap the page tables in place. 298# 299config ARCH_HAS_DMA_SET_UNCACHED 300 bool 301 302# 303# Select if the architectures provides the arch_dma_clear_uncached symbol 304# to undo an in-place page table remap for uncached access. 305# 306config ARCH_HAS_DMA_CLEAR_UNCACHED 307 bool 308 309config ARCH_HAS_CPU_FINALIZE_INIT 310 bool 311 312# The architecture has a per-task state that includes the mm's PASID 313config ARCH_HAS_CPU_PASID 314 bool 315 select IOMMU_MM_DATA 316 317config HAVE_ARCH_THREAD_STRUCT_WHITELIST 318 bool 319 help 320 An architecture should select this to provide hardened usercopy 321 knowledge about what region of the thread_struct should be 322 whitelisted for copying to userspace. Normally this is only the 323 FPU registers. Specifically, arch_thread_struct_whitelist() 324 should be implemented. Without this, the entire thread_struct 325 field in task_struct will be left whitelisted. 326 327# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 328config ARCH_WANTS_DYNAMIC_TASK_STRUCT 329 bool 330 331config ARCH_WANTS_NO_INSTR 332 bool 333 help 334 An architecture should select this if the noinstr macro is being used on 335 functions to denote that the toolchain should avoid instrumenting such 336 functions and is required for correctness. 337 338config ARCH_32BIT_OFF_T 339 bool 340 depends on !64BIT 341 help 342 All new 32-bit architectures should have 64-bit off_t type on 343 userspace side which corresponds to the loff_t kernel type. This 344 is the requirement for modern ABIs. Some existing architectures 345 still support 32-bit off_t. This option is enabled for all such 346 architectures explicitly. 347 348# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 349config ARCH_32BIT_USTAT_F_TINODE 350 bool 351 352config HAVE_ASM_MODVERSIONS 353 bool 354 help 355 This symbol should be selected by an architecture if it provides 356 <asm/asm-prototypes.h> to support the module versioning for symbols 357 exported from assembly code. 358 359config HAVE_REGS_AND_STACK_ACCESS_API 360 bool 361 help 362 This symbol should be selected by an architecture if it supports 363 the API needed to access registers and stack entries from pt_regs, 364 declared in asm/ptrace.h 365 For example the kprobes-based event tracer needs this API. 366 367config HAVE_RSEQ 368 bool 369 depends on HAVE_REGS_AND_STACK_ACCESS_API 370 help 371 This symbol should be selected by an architecture if it 372 supports an implementation of restartable sequences. 373 374config HAVE_RUST 375 bool 376 help 377 This symbol should be selected by an architecture if it 378 supports Rust. 379 380config HAVE_FUNCTION_ARG_ACCESS_API 381 bool 382 help 383 This symbol should be selected by an architecture if it supports 384 the API needed to access function arguments from pt_regs, 385 declared in asm/ptrace.h 386 387config HAVE_HW_BREAKPOINT 388 bool 389 depends on PERF_EVENTS 390 391config HAVE_MIXED_BREAKPOINTS_REGS 392 bool 393 depends on HAVE_HW_BREAKPOINT 394 help 395 Depending on the arch implementation of hardware breakpoints, 396 some of them have separate registers for data and instruction 397 breakpoints addresses, others have mixed registers to store 398 them but define the access type in a control register. 399 Select this option if your arch implements breakpoints under the 400 latter fashion. 401 402config HAVE_USER_RETURN_NOTIFIER 403 bool 404 405config HAVE_PERF_EVENTS_NMI 406 bool 407 help 408 System hardware can generate an NMI using the perf event 409 subsystem. Also has support for calculating CPU cycle events 410 to determine how many clock cycles in a given period. 411 412config HAVE_HARDLOCKUP_DETECTOR_PERF 413 bool 414 depends on HAVE_PERF_EVENTS_NMI 415 help 416 The arch chooses to use the generic perf-NMI-based hardlockup 417 detector. Must define HAVE_PERF_EVENTS_NMI. 418 419config HAVE_HARDLOCKUP_DETECTOR_ARCH 420 bool 421 help 422 The arch provides its own hardlockup detector implementation instead 423 of the generic ones. 424 425 It uses the same command line parameters, and sysctl interface, 426 as the generic hardlockup detectors. 427 428config HAVE_PERF_REGS 429 bool 430 help 431 Support selective register dumps for perf events. This includes 432 bit-mapping of each registers and a unique architecture id. 433 434config HAVE_PERF_USER_STACK_DUMP 435 bool 436 help 437 Support user stack dumps for perf event samples. This needs 438 access to the user stack pointer which is not unified across 439 architectures. 440 441config HAVE_ARCH_JUMP_LABEL 442 bool 443 444config HAVE_ARCH_JUMP_LABEL_RELATIVE 445 bool 446 447config MMU_GATHER_TABLE_FREE 448 bool 449 450config MMU_GATHER_RCU_TABLE_FREE 451 bool 452 select MMU_GATHER_TABLE_FREE 453 454config MMU_GATHER_PAGE_SIZE 455 bool 456 457config MMU_GATHER_NO_RANGE 458 bool 459 select MMU_GATHER_MERGE_VMAS 460 461config MMU_GATHER_NO_FLUSH_CACHE 462 bool 463 464config MMU_GATHER_MERGE_VMAS 465 bool 466 467config MMU_GATHER_NO_GATHER 468 bool 469 depends on MMU_GATHER_TABLE_FREE 470 471config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 472 bool 473 help 474 Temporary select until all architectures can be converted to have 475 irqs disabled over activate_mm. Architectures that do IPI based TLB 476 shootdowns should enable this. 477 478# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 479# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 480# to/from kernel threads when the same mm is running on a lot of CPUs (a large 481# multi-threaded application), by reducing contention on the mm refcount. 482# 483# This can be disabled if the architecture ensures no CPUs are using an mm as a 484# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 485# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 486# final exit(2) TLB flush, for example. 487# 488# To implement this, an arch *must*: 489# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 490# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 491# converted already). 492config MMU_LAZY_TLB_REFCOUNT 493 def_bool y 494 depends on !MMU_LAZY_TLB_SHOOTDOWN 495 496# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 497# mm as a lazy tlb beyond its last reference count, by shooting down these 498# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 499# be using the mm as a lazy tlb, so that they may switch themselves to using 500# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 501# may be using mm as a lazy tlb mm. 502# 503# To implement this, an arch *must*: 504# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 505# at least all possible CPUs in which the mm is lazy. 506# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 507config MMU_LAZY_TLB_SHOOTDOWN 508 bool 509 510config ARCH_HAVE_NMI_SAFE_CMPXCHG 511 bool 512 513config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 514 bool 515 516config HAVE_ALIGNED_STRUCT_PAGE 517 bool 518 help 519 This makes sure that struct pages are double word aligned and that 520 e.g. the SLUB allocator can perform double word atomic operations 521 on a struct page for better performance. However selecting this 522 might increase the size of a struct page by a word. 523 524config HAVE_CMPXCHG_LOCAL 525 bool 526 527config HAVE_CMPXCHG_DOUBLE 528 bool 529 530config ARCH_WEAK_RELEASE_ACQUIRE 531 bool 532 533config ARCH_WANT_IPC_PARSE_VERSION 534 bool 535 536config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 537 bool 538 539config ARCH_WANT_OLD_COMPAT_IPC 540 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 541 bool 542 543config HAVE_ARCH_SECCOMP 544 bool 545 help 546 An arch should select this symbol to support seccomp mode 1 (the fixed 547 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 548 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 549 - __NR_seccomp_read_32 550 - __NR_seccomp_write_32 551 - __NR_seccomp_exit_32 552 - __NR_seccomp_sigreturn_32 553 554config HAVE_ARCH_SECCOMP_FILTER 555 bool 556 select HAVE_ARCH_SECCOMP 557 help 558 An arch should select this symbol if it provides all of these things: 559 - all the requirements for HAVE_ARCH_SECCOMP 560 - syscall_get_arch() 561 - syscall_get_arguments() 562 - syscall_rollback() 563 - syscall_set_return_value() 564 - SIGSYS siginfo_t support 565 - secure_computing is called from a ptrace_event()-safe context 566 - secure_computing return value is checked and a return value of -1 567 results in the system call being skipped immediately. 568 - seccomp syscall wired up 569 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 570 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 571 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 572 573config SECCOMP 574 prompt "Enable seccomp to safely execute untrusted bytecode" 575 def_bool y 576 depends on HAVE_ARCH_SECCOMP 577 help 578 This kernel feature is useful for number crunching applications 579 that may need to handle untrusted bytecode during their 580 execution. By using pipes or other transports made available 581 to the process as file descriptors supporting the read/write 582 syscalls, it's possible to isolate those applications in their 583 own address space using seccomp. Once seccomp is enabled via 584 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 585 disabled and the task is only allowed to execute a few safe 586 syscalls defined by each seccomp mode. 587 588 If unsure, say Y. 589 590config SECCOMP_FILTER 591 def_bool y 592 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 593 help 594 Enable tasks to build secure computing environments defined 595 in terms of Berkeley Packet Filter programs which implement 596 task-defined system call filtering polices. 597 598 See Documentation/userspace-api/seccomp_filter.rst for details. 599 600config SECCOMP_CACHE_DEBUG 601 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 602 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 603 depends on PROC_FS 604 help 605 This enables the /proc/pid/seccomp_cache interface to monitor 606 seccomp cache data. The file format is subject to change. Reading 607 the file requires CAP_SYS_ADMIN. 608 609 This option is for debugging only. Enabling presents the risk that 610 an adversary may be able to infer the seccomp filter logic. 611 612 If unsure, say N. 613 614config HAVE_ARCH_STACKLEAK 615 bool 616 help 617 An architecture should select this if it has the code which 618 fills the used part of the kernel stack with the STACKLEAK_POISON 619 value before returning from system calls. 620 621config HAVE_STACKPROTECTOR 622 bool 623 help 624 An arch should select this symbol if: 625 - it has implemented a stack canary (e.g. __stack_chk_guard) 626 627config STACKPROTECTOR 628 bool "Stack Protector buffer overflow detection" 629 depends on HAVE_STACKPROTECTOR 630 depends on $(cc-option,-fstack-protector) 631 default y 632 help 633 This option turns on the "stack-protector" GCC feature. This 634 feature puts, at the beginning of functions, a canary value on 635 the stack just before the return address, and validates 636 the value just before actually returning. Stack based buffer 637 overflows (that need to overwrite this return address) now also 638 overwrite the canary, which gets detected and the attack is then 639 neutralized via a kernel panic. 640 641 Functions will have the stack-protector canary logic added if they 642 have an 8-byte or larger character array on the stack. 643 644 This feature requires gcc version 4.2 or above, or a distribution 645 gcc with the feature backported ("-fstack-protector"). 646 647 On an x86 "defconfig" build, this feature adds canary checks to 648 about 3% of all kernel functions, which increases kernel code size 649 by about 0.3%. 650 651config STACKPROTECTOR_STRONG 652 bool "Strong Stack Protector" 653 depends on STACKPROTECTOR 654 depends on $(cc-option,-fstack-protector-strong) 655 default y 656 help 657 Functions will have the stack-protector canary logic added in any 658 of the following conditions: 659 660 - local variable's address used as part of the right hand side of an 661 assignment or function argument 662 - local variable is an array (or union containing an array), 663 regardless of array type or length 664 - uses register local variables 665 666 This feature requires gcc version 4.9 or above, or a distribution 667 gcc with the feature backported ("-fstack-protector-strong"). 668 669 On an x86 "defconfig" build, this feature adds canary checks to 670 about 20% of all kernel functions, which increases the kernel code 671 size by about 2%. 672 673config ARCH_SUPPORTS_SHADOW_CALL_STACK 674 bool 675 help 676 An architecture should select this if it supports the compiler's 677 Shadow Call Stack and implements runtime support for shadow stack 678 switching. 679 680config SHADOW_CALL_STACK 681 bool "Shadow Call Stack" 682 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 683 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 684 depends on MMU 685 help 686 This option enables the compiler's Shadow Call Stack, which 687 uses a shadow stack to protect function return addresses from 688 being overwritten by an attacker. More information can be found 689 in the compiler's documentation: 690 691 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 692 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 693 694 Note that security guarantees in the kernel differ from the 695 ones documented for user space. The kernel must store addresses 696 of shadow stacks in memory, which means an attacker capable of 697 reading and writing arbitrary memory may be able to locate them 698 and hijack control flow by modifying the stacks. 699 700config DYNAMIC_SCS 701 bool 702 help 703 Set by the arch code if it relies on code patching to insert the 704 shadow call stack push and pop instructions rather than on the 705 compiler. 706 707config LTO 708 bool 709 help 710 Selected if the kernel will be built using the compiler's LTO feature. 711 712config LTO_CLANG 713 bool 714 select LTO 715 help 716 Selected if the kernel will be built using Clang's LTO feature. 717 718config ARCH_SUPPORTS_LTO_CLANG 719 bool 720 help 721 An architecture should select this option if it supports: 722 - compiling with Clang, 723 - compiling inline assembly with Clang's integrated assembler, 724 - and linking with LLD. 725 726config ARCH_SUPPORTS_LTO_CLANG_THIN 727 bool 728 help 729 An architecture should select this option if it can support Clang's 730 ThinLTO mode. 731 732config HAS_LTO_CLANG 733 def_bool y 734 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 735 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 736 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 737 depends on ARCH_SUPPORTS_LTO_CLANG 738 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 739 # https://github.com/ClangBuiltLinux/linux/issues/1721 740 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 741 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 742 depends on !GCOV_KERNEL 743 help 744 The compiler and Kconfig options support building with Clang's 745 LTO. 746 747choice 748 prompt "Link Time Optimization (LTO)" 749 default LTO_NONE 750 help 751 This option enables Link Time Optimization (LTO), which allows the 752 compiler to optimize binaries globally. 753 754 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 755 so it's disabled by default. 756 757config LTO_NONE 758 bool "None" 759 help 760 Build the kernel normally, without Link Time Optimization (LTO). 761 762config LTO_CLANG_FULL 763 bool "Clang Full LTO (EXPERIMENTAL)" 764 depends on HAS_LTO_CLANG 765 depends on !COMPILE_TEST 766 select LTO_CLANG 767 help 768 This option enables Clang's full Link Time Optimization (LTO), which 769 allows the compiler to optimize the kernel globally. If you enable 770 this option, the compiler generates LLVM bitcode instead of ELF 771 object files, and the actual compilation from bitcode happens at 772 the LTO link step, which may take several minutes depending on the 773 kernel configuration. More information can be found from LLVM's 774 documentation: 775 776 https://llvm.org/docs/LinkTimeOptimization.html 777 778 During link time, this option can use a large amount of RAM, and 779 may take much longer than the ThinLTO option. 780 781config LTO_CLANG_THIN 782 bool "Clang ThinLTO (EXPERIMENTAL)" 783 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 784 select LTO_CLANG 785 help 786 This option enables Clang's ThinLTO, which allows for parallel 787 optimization and faster incremental compiles compared to the 788 CONFIG_LTO_CLANG_FULL option. More information can be found 789 from Clang's documentation: 790 791 https://clang.llvm.org/docs/ThinLTO.html 792 793 If unsure, say Y. 794endchoice 795 796config ARCH_SUPPORTS_CFI_CLANG 797 bool 798 help 799 An architecture should select this option if it can support Clang's 800 Control-Flow Integrity (CFI) checking. 801 802config ARCH_USES_CFI_TRAPS 803 bool 804 805config CFI_CLANG 806 bool "Use Clang's Control Flow Integrity (CFI)" 807 depends on ARCH_SUPPORTS_CFI_CLANG 808 depends on $(cc-option,-fsanitize=kcfi) 809 help 810 This option enables Clang's forward-edge Control Flow Integrity 811 (CFI) checking, where the compiler injects a runtime check to each 812 indirect function call to ensure the target is a valid function with 813 the correct static type. This restricts possible call targets and 814 makes it more difficult for an attacker to exploit bugs that allow 815 the modification of stored function pointers. More information can be 816 found from Clang's documentation: 817 818 https://clang.llvm.org/docs/ControlFlowIntegrity.html 819 820config CFI_PERMISSIVE 821 bool "Use CFI in permissive mode" 822 depends on CFI_CLANG 823 help 824 When selected, Control Flow Integrity (CFI) violations result in a 825 warning instead of a kernel panic. This option should only be used 826 for finding indirect call type mismatches during development. 827 828 If unsure, say N. 829 830config HAVE_ARCH_WITHIN_STACK_FRAMES 831 bool 832 help 833 An architecture should select this if it can walk the kernel stack 834 frames to determine if an object is part of either the arguments 835 or local variables (i.e. that it excludes saved return addresses, 836 and similar) by implementing an inline arch_within_stack_frames(), 837 which is used by CONFIG_HARDENED_USERCOPY. 838 839config HAVE_CONTEXT_TRACKING_USER 840 bool 841 help 842 Provide kernel/user boundaries probes necessary for subsystems 843 that need it, such as userspace RCU extended quiescent state. 844 Syscalls need to be wrapped inside user_exit()-user_enter(), either 845 optimized behind static key or through the slow path using TIF_NOHZ 846 flag. Exceptions handlers must be wrapped as well. Irqs are already 847 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 848 handling on irq exit still need to be protected. 849 850config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 851 bool 852 help 853 Architecture neither relies on exception_enter()/exception_exit() 854 nor on schedule_user(). Also preempt_schedule_notrace() and 855 preempt_schedule_irq() can't be called in a preemptible section 856 while context tracking is CONTEXT_USER. This feature reflects a sane 857 entry implementation where the following requirements are met on 858 critical entry code, ie: before user_exit() or after user_enter(): 859 860 - Critical entry code isn't preemptible (or better yet: 861 not interruptible). 862 - No use of RCU read side critical sections, unless ct_nmi_enter() 863 got called. 864 - No use of instrumentation, unless instrumentation_begin() got 865 called. 866 867config HAVE_TIF_NOHZ 868 bool 869 help 870 Arch relies on TIF_NOHZ and syscall slow path to implement context 871 tracking calls to user_enter()/user_exit(). 872 873config HAVE_VIRT_CPU_ACCOUNTING 874 bool 875 876config HAVE_VIRT_CPU_ACCOUNTING_IDLE 877 bool 878 help 879 Architecture has its own way to account idle CPU time and therefore 880 doesn't implement vtime_account_idle(). 881 882config ARCH_HAS_SCALED_CPUTIME 883 bool 884 885config HAVE_VIRT_CPU_ACCOUNTING_GEN 886 bool 887 default y if 64BIT 888 help 889 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 890 Before enabling this option, arch code must be audited 891 to ensure there are no races in concurrent read/write of 892 cputime_t. For example, reading/writing 64-bit cputime_t on 893 some 32-bit arches may require multiple accesses, so proper 894 locking is needed to protect against concurrent accesses. 895 896config HAVE_IRQ_TIME_ACCOUNTING 897 bool 898 help 899 Archs need to ensure they use a high enough resolution clock to 900 support irq time accounting and then call enable_sched_clock_irqtime(). 901 902config HAVE_MOVE_PUD 903 bool 904 help 905 Architectures that select this are able to move page tables at the 906 PUD level. If there are only 3 page table levels, the move effectively 907 happens at the PGD level. 908 909config HAVE_MOVE_PMD 910 bool 911 help 912 Archs that select this are able to move page tables at the PMD level. 913 914config HAVE_ARCH_TRANSPARENT_HUGEPAGE 915 bool 916 917config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 918 bool 919 920config HAVE_ARCH_HUGE_VMAP 921 bool 922 923# 924# Archs that select this would be capable of PMD-sized vmaps (i.e., 925# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 926# must be used to enable allocations to use hugepages. 927# 928config HAVE_ARCH_HUGE_VMALLOC 929 depends on HAVE_ARCH_HUGE_VMAP 930 bool 931 932config ARCH_WANT_HUGE_PMD_SHARE 933 bool 934 935# Archs that want to use pmd_mkwrite on kernel memory need it defined even 936# if there are no userspace memory management features that use it 937config ARCH_WANT_KERNEL_PMD_MKWRITE 938 bool 939 940config ARCH_WANT_PMD_MKWRITE 941 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 942 943config HAVE_ARCH_SOFT_DIRTY 944 bool 945 946config HAVE_MOD_ARCH_SPECIFIC 947 bool 948 help 949 The arch uses struct mod_arch_specific to store data. Many arches 950 just need a simple module loader without arch specific data - those 951 should not enable this. 952 953config MODULES_USE_ELF_RELA 954 bool 955 help 956 Modules only use ELF RELA relocations. Modules with ELF REL 957 relocations will give an error. 958 959config MODULES_USE_ELF_REL 960 bool 961 help 962 Modules only use ELF REL relocations. Modules with ELF RELA 963 relocations will give an error. 964 965config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 966 bool 967 help 968 For architectures like powerpc/32 which have constraints on module 969 allocation and need to allocate module data outside of module area. 970 971config HAVE_IRQ_EXIT_ON_IRQ_STACK 972 bool 973 help 974 Architecture doesn't only execute the irq handler on the irq stack 975 but also irq_exit(). This way we can process softirqs on this irq 976 stack instead of switching to a new one when we call __do_softirq() 977 in the end of an hardirq. 978 This spares a stack switch and improves cache usage on softirq 979 processing. 980 981config HAVE_SOFTIRQ_ON_OWN_STACK 982 bool 983 help 984 Architecture provides a function to run __do_softirq() on a 985 separate stack. 986 987config SOFTIRQ_ON_OWN_STACK 988 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 989 990config ALTERNATE_USER_ADDRESS_SPACE 991 bool 992 help 993 Architectures set this when the CPU uses separate address 994 spaces for kernel and user space pointers. In this case, the 995 access_ok() check on a __user pointer is skipped. 996 997config PGTABLE_LEVELS 998 int 999 default 2 1000 1001config ARCH_HAS_ELF_RANDOMIZE 1002 bool 1003 help 1004 An architecture supports choosing randomized locations for 1005 stack, mmap, brk, and ET_DYN. Defined functions: 1006 - arch_mmap_rnd() 1007 - arch_randomize_brk() 1008 1009config HAVE_ARCH_MMAP_RND_BITS 1010 bool 1011 help 1012 An arch should select this symbol if it supports setting a variable 1013 number of bits for use in establishing the base address for mmap 1014 allocations, has MMU enabled and provides values for both: 1015 - ARCH_MMAP_RND_BITS_MIN 1016 - ARCH_MMAP_RND_BITS_MAX 1017 1018config HAVE_EXIT_THREAD 1019 bool 1020 help 1021 An architecture implements exit_thread. 1022 1023config ARCH_MMAP_RND_BITS_MIN 1024 int 1025 1026config ARCH_MMAP_RND_BITS_MAX 1027 int 1028 1029config ARCH_MMAP_RND_BITS_DEFAULT 1030 int 1031 1032config ARCH_MMAP_RND_BITS 1033 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1034 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1035 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1036 default ARCH_MMAP_RND_BITS_MIN 1037 depends on HAVE_ARCH_MMAP_RND_BITS 1038 help 1039 This value can be used to select the number of bits to use to 1040 determine the random offset to the base address of vma regions 1041 resulting from mmap allocations. This value will be bounded 1042 by the architecture's minimum and maximum supported values. 1043 1044 This value can be changed after boot using the 1045 /proc/sys/vm/mmap_rnd_bits tunable 1046 1047config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1048 bool 1049 help 1050 An arch should select this symbol if it supports running applications 1051 in compatibility mode, supports setting a variable number of bits for 1052 use in establishing the base address for mmap allocations, has MMU 1053 enabled and provides values for both: 1054 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1055 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1056 1057config ARCH_MMAP_RND_COMPAT_BITS_MIN 1058 int 1059 1060config ARCH_MMAP_RND_COMPAT_BITS_MAX 1061 int 1062 1063config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1064 int 1065 1066config ARCH_MMAP_RND_COMPAT_BITS 1067 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1068 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1069 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1070 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1071 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1072 help 1073 This value can be used to select the number of bits to use to 1074 determine the random offset to the base address of vma regions 1075 resulting from mmap allocations for compatible applications This 1076 value will be bounded by the architecture's minimum and maximum 1077 supported values. 1078 1079 This value can be changed after boot using the 1080 /proc/sys/vm/mmap_rnd_compat_bits tunable 1081 1082config HAVE_ARCH_COMPAT_MMAP_BASES 1083 bool 1084 help 1085 This allows 64bit applications to invoke 32-bit mmap() syscall 1086 and vice-versa 32-bit applications to call 64-bit mmap(). 1087 Required for applications doing different bitness syscalls. 1088 1089config HAVE_PAGE_SIZE_4KB 1090 bool 1091 1092config HAVE_PAGE_SIZE_8KB 1093 bool 1094 1095config HAVE_PAGE_SIZE_16KB 1096 bool 1097 1098config HAVE_PAGE_SIZE_32KB 1099 bool 1100 1101config HAVE_PAGE_SIZE_64KB 1102 bool 1103 1104config HAVE_PAGE_SIZE_256KB 1105 bool 1106 1107choice 1108 prompt "MMU page size" 1109 1110config PAGE_SIZE_4KB 1111 bool "4KiB pages" 1112 depends on HAVE_PAGE_SIZE_4KB 1113 help 1114 This option select the standard 4KiB Linux page size and the only 1115 available option on many architectures. Using 4KiB page size will 1116 minimize memory consumption and is therefore recommended for low 1117 memory systems. 1118 Some software that is written for x86 systems makes incorrect 1119 assumptions about the page size and only runs on 4KiB pages. 1120 1121config PAGE_SIZE_8KB 1122 bool "8KiB pages" 1123 depends on HAVE_PAGE_SIZE_8KB 1124 help 1125 This option is the only supported page size on a few older 1126 processors, and can be slightly faster than 4KiB pages. 1127 1128config PAGE_SIZE_16KB 1129 bool "16KiB pages" 1130 depends on HAVE_PAGE_SIZE_16KB 1131 help 1132 This option is usually a good compromise between memory 1133 consumption and performance for typical desktop and server 1134 workloads, often saving a level of page table lookups compared 1135 to 4KB pages as well as reducing TLB pressure and overhead of 1136 per-page operations in the kernel at the expense of a larger 1137 page cache. 1138 1139config PAGE_SIZE_32KB 1140 bool "32KiB pages" 1141 depends on HAVE_PAGE_SIZE_32KB 1142 help 1143 Using 32KiB page size will result in slightly higher performance 1144 kernel at the price of higher memory consumption compared to 1145 16KiB pages. This option is available only on cnMIPS cores. 1146 Note that you will need a suitable Linux distribution to 1147 support this. 1148 1149config PAGE_SIZE_64KB 1150 bool "64KiB pages" 1151 depends on HAVE_PAGE_SIZE_64KB 1152 help 1153 Using 64KiB page size will result in slightly higher performance 1154 kernel at the price of much higher memory consumption compared to 1155 4KiB or 16KiB pages. 1156 This is not suitable for general-purpose workloads but the 1157 better performance may be worth the cost for certain types of 1158 supercomputing or database applications that work mostly with 1159 large in-memory data rather than small files. 1160 1161config PAGE_SIZE_256KB 1162 bool "256KiB pages" 1163 depends on HAVE_PAGE_SIZE_256KB 1164 help 1165 256KiB pages have little practical value due to their extreme 1166 memory usage. The kernel will only be able to run applications 1167 that have been compiled with '-zmax-page-size' set to 256KiB 1168 (the default is 64KiB or 4KiB on most architectures). 1169 1170endchoice 1171 1172config PAGE_SIZE_LESS_THAN_64KB 1173 def_bool y 1174 depends on !PAGE_SIZE_64KB 1175 depends on PAGE_SIZE_LESS_THAN_256KB 1176 1177config PAGE_SIZE_LESS_THAN_256KB 1178 def_bool y 1179 depends on !PAGE_SIZE_256KB 1180 1181config PAGE_SHIFT 1182 int 1183 default 12 if PAGE_SIZE_4KB 1184 default 13 if PAGE_SIZE_8KB 1185 default 14 if PAGE_SIZE_16KB 1186 default 15 if PAGE_SIZE_32KB 1187 default 16 if PAGE_SIZE_64KB 1188 default 18 if PAGE_SIZE_256KB 1189 1190# This allows to use a set of generic functions to determine mmap base 1191# address by giving priority to top-down scheme only if the process 1192# is not in legacy mode (compat task, unlimited stack size or 1193# sysctl_legacy_va_layout). 1194# Architecture that selects this option can provide its own version of: 1195# - STACK_RND_MASK 1196config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1197 bool 1198 depends on MMU 1199 select ARCH_HAS_ELF_RANDOMIZE 1200 1201config HAVE_OBJTOOL 1202 bool 1203 1204config HAVE_JUMP_LABEL_HACK 1205 bool 1206 1207config HAVE_NOINSTR_HACK 1208 bool 1209 1210config HAVE_NOINSTR_VALIDATION 1211 bool 1212 1213config HAVE_UACCESS_VALIDATION 1214 bool 1215 select OBJTOOL 1216 1217config HAVE_STACK_VALIDATION 1218 bool 1219 help 1220 Architecture supports objtool compile-time frame pointer rule 1221 validation. 1222 1223config HAVE_RELIABLE_STACKTRACE 1224 bool 1225 help 1226 Architecture has either save_stack_trace_tsk_reliable() or 1227 arch_stack_walk_reliable() function which only returns a stack trace 1228 if it can guarantee the trace is reliable. 1229 1230config HAVE_ARCH_HASH 1231 bool 1232 default n 1233 help 1234 If this is set, the architecture provides an <asm/hash.h> 1235 file which provides platform-specific implementations of some 1236 functions in <linux/hash.h> or fs/namei.c. 1237 1238config HAVE_ARCH_NVRAM_OPS 1239 bool 1240 1241config ISA_BUS_API 1242 def_bool ISA 1243 1244# 1245# ABI hall of shame 1246# 1247config CLONE_BACKWARDS 1248 bool 1249 help 1250 Architecture has tls passed as the 4th argument of clone(2), 1251 not the 5th one. 1252 1253config CLONE_BACKWARDS2 1254 bool 1255 help 1256 Architecture has the first two arguments of clone(2) swapped. 1257 1258config CLONE_BACKWARDS3 1259 bool 1260 help 1261 Architecture has tls passed as the 3rd argument of clone(2), 1262 not the 5th one. 1263 1264config ODD_RT_SIGACTION 1265 bool 1266 help 1267 Architecture has unusual rt_sigaction(2) arguments 1268 1269config OLD_SIGSUSPEND 1270 bool 1271 help 1272 Architecture has old sigsuspend(2) syscall, of one-argument variety 1273 1274config OLD_SIGSUSPEND3 1275 bool 1276 help 1277 Even weirder antique ABI - three-argument sigsuspend(2) 1278 1279config OLD_SIGACTION 1280 bool 1281 help 1282 Architecture has old sigaction(2) syscall. Nope, not the same 1283 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1284 but fairly different variant of sigaction(2), thanks to OSF/1 1285 compatibility... 1286 1287config COMPAT_OLD_SIGACTION 1288 bool 1289 1290config COMPAT_32BIT_TIME 1291 bool "Provide system calls for 32-bit time_t" 1292 default !64BIT || COMPAT 1293 help 1294 This enables 32 bit time_t support in addition to 64 bit time_t support. 1295 This is relevant on all 32-bit architectures, and 64-bit architectures 1296 as part of compat syscall handling. 1297 1298config ARCH_NO_PREEMPT 1299 bool 1300 1301config ARCH_SUPPORTS_RT 1302 bool 1303 1304config CPU_NO_EFFICIENT_FFS 1305 def_bool n 1306 1307config HAVE_ARCH_VMAP_STACK 1308 def_bool n 1309 help 1310 An arch should select this symbol if it can support kernel stacks 1311 in vmalloc space. This means: 1312 1313 - vmalloc space must be large enough to hold many kernel stacks. 1314 This may rule out many 32-bit architectures. 1315 1316 - Stacks in vmalloc space need to work reliably. For example, if 1317 vmap page tables are created on demand, either this mechanism 1318 needs to work while the stack points to a virtual address with 1319 unpopulated page tables or arch code (switch_to() and switch_mm(), 1320 most likely) needs to ensure that the stack's page table entries 1321 are populated before running on a possibly unpopulated stack. 1322 1323 - If the stack overflows into a guard page, something reasonable 1324 should happen. The definition of "reasonable" is flexible, but 1325 instantly rebooting without logging anything would be unfriendly. 1326 1327config VMAP_STACK 1328 default y 1329 bool "Use a virtually-mapped stack" 1330 depends on HAVE_ARCH_VMAP_STACK 1331 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1332 help 1333 Enable this if you want the use virtually-mapped kernel stacks 1334 with guard pages. This causes kernel stack overflows to be 1335 caught immediately rather than causing difficult-to-diagnose 1336 corruption. 1337 1338 To use this with software KASAN modes, the architecture must support 1339 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1340 must be enabled. 1341 1342config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1343 def_bool n 1344 help 1345 An arch should select this symbol if it can support kernel stack 1346 offset randomization with calls to add_random_kstack_offset() 1347 during syscall entry and choose_random_kstack_offset() during 1348 syscall exit. Careful removal of -fstack-protector-strong and 1349 -fstack-protector should also be applied to the entry code and 1350 closely examined, as the artificial stack bump looks like an array 1351 to the compiler, so it will attempt to add canary checks regardless 1352 of the static branch state. 1353 1354config RANDOMIZE_KSTACK_OFFSET 1355 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1356 default y 1357 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1358 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1359 help 1360 The kernel stack offset can be randomized (after pt_regs) by 1361 roughly 5 bits of entropy, frustrating memory corruption 1362 attacks that depend on stack address determinism or 1363 cross-syscall address exposures. 1364 1365 The feature is controlled via the "randomize_kstack_offset=on/off" 1366 kernel boot param, and if turned off has zero overhead due to its use 1367 of static branches (see JUMP_LABEL). 1368 1369 If unsure, say Y. 1370 1371config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1372 bool "Default state of kernel stack offset randomization" 1373 depends on RANDOMIZE_KSTACK_OFFSET 1374 help 1375 Kernel stack offset randomization is controlled by kernel boot param 1376 "randomize_kstack_offset=on/off", and this config chooses the default 1377 boot state. 1378 1379config ARCH_OPTIONAL_KERNEL_RWX 1380 def_bool n 1381 1382config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1383 def_bool n 1384 1385config ARCH_HAS_STRICT_KERNEL_RWX 1386 def_bool n 1387 1388config STRICT_KERNEL_RWX 1389 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1390 depends on ARCH_HAS_STRICT_KERNEL_RWX 1391 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1392 help 1393 If this is set, kernel text and rodata memory will be made read-only, 1394 and non-text memory will be made non-executable. This provides 1395 protection against certain security exploits (e.g. executing the heap 1396 or modifying text) 1397 1398 These features are considered standard security practice these days. 1399 You should say Y here in almost all cases. 1400 1401config ARCH_HAS_STRICT_MODULE_RWX 1402 def_bool n 1403 1404config STRICT_MODULE_RWX 1405 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1406 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1407 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1408 help 1409 If this is set, module text and rodata memory will be made read-only, 1410 and non-text memory will be made non-executable. This provides 1411 protection against certain security exploits (e.g. writing to text) 1412 1413# select if the architecture provides an asm/dma-direct.h header 1414config ARCH_HAS_PHYS_TO_DMA 1415 bool 1416 1417config HAVE_ARCH_COMPILER_H 1418 bool 1419 help 1420 An architecture can select this if it provides an 1421 asm/compiler.h header that should be included after 1422 linux/compiler-*.h in order to override macro definitions that those 1423 headers generally provide. 1424 1425config HAVE_ARCH_PREL32_RELOCATIONS 1426 bool 1427 help 1428 May be selected by an architecture if it supports place-relative 1429 32-bit relocations, both in the toolchain and in the module loader, 1430 in which case relative references can be used in special sections 1431 for PCI fixup, initcalls etc which are only half the size on 64 bit 1432 architectures, and don't require runtime relocation on relocatable 1433 kernels. 1434 1435config ARCH_USE_MEMREMAP_PROT 1436 bool 1437 1438config LOCK_EVENT_COUNTS 1439 bool "Locking event counts collection" 1440 depends on DEBUG_FS 1441 help 1442 Enable light-weight counting of various locking related events 1443 in the system with minimal performance impact. This reduces 1444 the chance of application behavior change because of timing 1445 differences. The counts are reported via debugfs. 1446 1447# Select if the architecture has support for applying RELR relocations. 1448config ARCH_HAS_RELR 1449 bool 1450 1451config RELR 1452 bool "Use RELR relocation packing" 1453 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1454 default y 1455 help 1456 Store the kernel's dynamic relocations in the RELR relocation packing 1457 format. Requires a compatible linker (LLD supports this feature), as 1458 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1459 are compatible). 1460 1461config ARCH_HAS_MEM_ENCRYPT 1462 bool 1463 1464config ARCH_HAS_CC_PLATFORM 1465 bool 1466 1467config HAVE_SPARSE_SYSCALL_NR 1468 bool 1469 help 1470 An architecture should select this if its syscall numbering is sparse 1471 to save space. For example, MIPS architecture has a syscall array with 1472 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1473 related optimizations for a given architecture. 1474 1475config ARCH_HAS_VDSO_DATA 1476 bool 1477 1478config HAVE_STATIC_CALL 1479 bool 1480 1481config HAVE_STATIC_CALL_INLINE 1482 bool 1483 depends on HAVE_STATIC_CALL 1484 select OBJTOOL 1485 1486config HAVE_PREEMPT_DYNAMIC 1487 bool 1488 1489config HAVE_PREEMPT_DYNAMIC_CALL 1490 bool 1491 depends on HAVE_STATIC_CALL 1492 select HAVE_PREEMPT_DYNAMIC 1493 help 1494 An architecture should select this if it can handle the preemption 1495 model being selected at boot time using static calls. 1496 1497 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1498 preemption function will be patched directly. 1499 1500 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1501 call to a preemption function will go through a trampoline, and the 1502 trampoline will be patched. 1503 1504 It is strongly advised to support inline static call to avoid any 1505 overhead. 1506 1507config HAVE_PREEMPT_DYNAMIC_KEY 1508 bool 1509 depends on HAVE_ARCH_JUMP_LABEL 1510 select HAVE_PREEMPT_DYNAMIC 1511 help 1512 An architecture should select this if it can handle the preemption 1513 model being selected at boot time using static keys. 1514 1515 Each preemption function will be given an early return based on a 1516 static key. This should have slightly lower overhead than non-inline 1517 static calls, as this effectively inlines each trampoline into the 1518 start of its callee. This may avoid redundant work, and may 1519 integrate better with CFI schemes. 1520 1521 This will have greater overhead than using inline static calls as 1522 the call to the preemption function cannot be entirely elided. 1523 1524config ARCH_WANT_LD_ORPHAN_WARN 1525 bool 1526 help 1527 An arch should select this symbol once all linker sections are explicitly 1528 included, size-asserted, or discarded in the linker scripts. This is 1529 important because we never want expected sections to be placed heuristically 1530 by the linker, since the locations of such sections can change between linker 1531 versions. 1532 1533config HAVE_ARCH_PFN_VALID 1534 bool 1535 1536config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1537 bool 1538 1539config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1540 bool 1541 1542config ARCH_SPLIT_ARG64 1543 bool 1544 help 1545 If a 32-bit architecture requires 64-bit arguments to be split into 1546 pairs of 32-bit arguments, select this option. 1547 1548config ARCH_HAS_ELFCORE_COMPAT 1549 bool 1550 1551config ARCH_HAS_PARANOID_L1D_FLUSH 1552 bool 1553 1554config ARCH_HAVE_TRACE_MMIO_ACCESS 1555 bool 1556 1557config DYNAMIC_SIGFRAME 1558 bool 1559 1560# Select, if arch has a named attribute group bound to NUMA device nodes. 1561config HAVE_ARCH_NODE_DEV_GROUP 1562 bool 1563 1564config ARCH_HAS_HW_PTE_YOUNG 1565 bool 1566 help 1567 Architectures that select this option are capable of setting the 1568 accessed bit in PTE entries when using them as part of linear address 1569 translations. Architectures that require runtime check should select 1570 this option and override arch_has_hw_pte_young(). 1571 1572config ARCH_HAS_NONLEAF_PMD_YOUNG 1573 bool 1574 help 1575 Architectures that select this option are capable of setting the 1576 accessed bit in non-leaf PMD entries when using them as part of linear 1577 address translations. Page table walkers that clear the accessed bit 1578 may use this capability to reduce their search space. 1579 1580source "kernel/gcov/Kconfig" 1581 1582source "scripts/gcc-plugins/Kconfig" 1583 1584config FUNCTION_ALIGNMENT_4B 1585 bool 1586 1587config FUNCTION_ALIGNMENT_8B 1588 bool 1589 1590config FUNCTION_ALIGNMENT_16B 1591 bool 1592 1593config FUNCTION_ALIGNMENT_32B 1594 bool 1595 1596config FUNCTION_ALIGNMENT_64B 1597 bool 1598 1599config FUNCTION_ALIGNMENT 1600 int 1601 default 64 if FUNCTION_ALIGNMENT_64B 1602 default 32 if FUNCTION_ALIGNMENT_32B 1603 default 16 if FUNCTION_ALIGNMENT_16B 1604 default 8 if FUNCTION_ALIGNMENT_8B 1605 default 4 if FUNCTION_ALIGNMENT_4B 1606 default 0 1607 1608config CC_HAS_MIN_FUNCTION_ALIGNMENT 1609 # Detect availability of the GCC option -fmin-function-alignment which 1610 # guarantees minimal alignment for all functions, unlike 1611 # -falign-functions which the compiler ignores for cold functions. 1612 def_bool $(cc-option, -fmin-function-alignment=8) 1613 1614config CC_HAS_SANE_FUNCTION_ALIGNMENT 1615 # Set if the guaranteed alignment with -fmin-function-alignment is 1616 # available or extra care is required in the kernel. Clang provides 1617 # strict alignment always, even with -falign-functions. 1618 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1619 1620endmenu 1621