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 12menu "General architecture-dependent options" 13 14config ARCH_HAS_SUBPAGE_FAULTS 15 bool 16 help 17 Select if the architecture can check permissions at sub-page 18 granularity (e.g. arm64 MTE). The probe_user_*() functions 19 must be implemented. 20 21config HOTPLUG_SMT 22 bool 23 24config SMT_NUM_THREADS_DYNAMIC 25 bool 26 27# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 28config HOTPLUG_CORE_SYNC 29 bool 30 31# Basic CPU dead synchronization selected by architecture 32config HOTPLUG_CORE_SYNC_DEAD 33 bool 34 select HOTPLUG_CORE_SYNC 35 36# Full CPU synchronization with alive state selected by architecture 37config HOTPLUG_CORE_SYNC_FULL 38 bool 39 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 40 select HOTPLUG_CORE_SYNC 41 42config HOTPLUG_SPLIT_STARTUP 43 bool 44 select HOTPLUG_CORE_SYNC_FULL 45 46config HOTPLUG_PARALLEL 47 bool 48 select HOTPLUG_SPLIT_STARTUP 49 50config GENERIC_ENTRY 51 bool 52 53config KPROBES 54 bool "Kprobes" 55 depends on MODULES 56 depends on HAVE_KPROBES 57 select KALLSYMS 58 select TASKS_RCU if PREEMPTION 59 help 60 Kprobes allows you to trap at almost any kernel address and 61 execute a callback function. register_kprobe() establishes 62 a probepoint and specifies the callback. Kprobes is useful 63 for kernel debugging, non-intrusive instrumentation and testing. 64 If in doubt, say "N". 65 66config JUMP_LABEL 67 bool "Optimize very unlikely/likely branches" 68 depends on HAVE_ARCH_JUMP_LABEL 69 select OBJTOOL if HAVE_JUMP_LABEL_HACK 70 help 71 This option enables a transparent branch optimization that 72 makes certain almost-always-true or almost-always-false branch 73 conditions even cheaper to execute within the kernel. 74 75 Certain performance-sensitive kernel code, such as trace points, 76 scheduler functionality, networking code and KVM have such 77 branches and include support for this optimization technique. 78 79 If it is detected that the compiler has support for "asm goto", 80 the kernel will compile such branches with just a nop 81 instruction. When the condition flag is toggled to true, the 82 nop will be converted to a jump instruction to execute the 83 conditional block of instructions. 84 85 This technique lowers overhead and stress on the branch prediction 86 of the processor and generally makes the kernel faster. The update 87 of the condition is slower, but those are always very rare. 88 89 ( On 32-bit x86, the necessary options added to the compiler 90 flags may increase the size of the kernel slightly. ) 91 92config STATIC_KEYS_SELFTEST 93 bool "Static key selftest" 94 depends on JUMP_LABEL 95 help 96 Boot time self-test of the branch patching code. 97 98config STATIC_CALL_SELFTEST 99 bool "Static call selftest" 100 depends on HAVE_STATIC_CALL 101 help 102 Boot time self-test of the call patching code. 103 104config OPTPROBES 105 def_bool y 106 depends on KPROBES && HAVE_OPTPROBES 107 select TASKS_RCU if PREEMPTION 108 109config KPROBES_ON_FTRACE 110 def_bool y 111 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 112 depends on DYNAMIC_FTRACE_WITH_REGS 113 help 114 If function tracer is enabled and the arch supports full 115 passing of pt_regs to function tracing, then kprobes can 116 optimize on top of function tracing. 117 118config UPROBES 119 def_bool n 120 depends on ARCH_SUPPORTS_UPROBES 121 help 122 Uprobes is the user-space counterpart to kprobes: they 123 enable instrumentation applications (such as 'perf probe') 124 to establish unintrusive probes in user-space binaries and 125 libraries, by executing handler functions when the probes 126 are hit by user-space applications. 127 128 ( These probes come in the form of single-byte breakpoints, 129 managed by the kernel and kept transparent to the probed 130 application. ) 131 132config HAVE_64BIT_ALIGNED_ACCESS 133 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 134 help 135 Some architectures require 64 bit accesses to be 64 bit 136 aligned, which also requires structs containing 64 bit values 137 to be 64 bit aligned too. This includes some 32 bit 138 architectures which can do 64 bit accesses, as well as 64 bit 139 architectures without unaligned access. 140 141 This symbol should be selected by an architecture if 64 bit 142 accesses are required to be 64 bit aligned in this way even 143 though it is not a 64 bit architecture. 144 145 See Documentation/core-api/unaligned-memory-access.rst for 146 more information on the topic of unaligned memory accesses. 147 148config HAVE_EFFICIENT_UNALIGNED_ACCESS 149 bool 150 help 151 Some architectures are unable to perform unaligned accesses 152 without the use of get_unaligned/put_unaligned. Others are 153 unable to perform such accesses efficiently (e.g. trap on 154 unaligned access and require fixing it up in the exception 155 handler.) 156 157 This symbol should be selected by an architecture if it can 158 perform unaligned accesses efficiently to allow different 159 code paths to be selected for these cases. Some network 160 drivers, for example, could opt to not fix up alignment 161 problems with received packets if doing so would not help 162 much. 163 164 See Documentation/core-api/unaligned-memory-access.rst for more 165 information on the topic of unaligned memory accesses. 166 167config ARCH_USE_BUILTIN_BSWAP 168 bool 169 help 170 Modern versions of GCC (since 4.4) have builtin functions 171 for handling byte-swapping. Using these, instead of the old 172 inline assembler that the architecture code provides in the 173 __arch_bswapXX() macros, allows the compiler to see what's 174 happening and offers more opportunity for optimisation. In 175 particular, the compiler will be able to combine the byteswap 176 with a nearby load or store and use load-and-swap or 177 store-and-swap instructions if the architecture has them. It 178 should almost *never* result in code which is worse than the 179 hand-coded assembler in <asm/swab.h>. But just in case it 180 does, the use of the builtins is optional. 181 182 Any architecture with load-and-swap or store-and-swap 183 instructions should set this. And it shouldn't hurt to set it 184 on architectures that don't have such instructions. 185 186config KRETPROBES 187 def_bool y 188 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 189 190config KRETPROBE_ON_RETHOOK 191 def_bool y 192 depends on HAVE_RETHOOK 193 depends on KRETPROBES 194 select RETHOOK 195 196config USER_RETURN_NOTIFIER 197 bool 198 depends on HAVE_USER_RETURN_NOTIFIER 199 help 200 Provide a kernel-internal notification when a cpu is about to 201 switch to user mode. 202 203config HAVE_IOREMAP_PROT 204 bool 205 206config HAVE_KPROBES 207 bool 208 209config HAVE_KRETPROBES 210 bool 211 212config HAVE_OPTPROBES 213 bool 214 215config HAVE_KPROBES_ON_FTRACE 216 bool 217 218config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 219 bool 220 help 221 Since kretprobes modifies return address on the stack, the 222 stacktrace may see the kretprobe trampoline address instead 223 of correct one. If the architecture stacktrace code and 224 unwinder can adjust such entries, select this configuration. 225 226config HAVE_FUNCTION_ERROR_INJECTION 227 bool 228 229config HAVE_NMI 230 bool 231 232config HAVE_FUNCTION_DESCRIPTORS 233 bool 234 235config TRACE_IRQFLAGS_SUPPORT 236 bool 237 238config TRACE_IRQFLAGS_NMI_SUPPORT 239 bool 240 241# 242# An arch should select this if it provides all these things: 243# 244# task_pt_regs() in asm/processor.h or asm/ptrace.h 245# arch_has_single_step() if there is hardware single-step support 246# arch_has_block_step() if there is hardware block-step support 247# asm/syscall.h supplying asm-generic/syscall.h interface 248# linux/regset.h user_regset interfaces 249# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 250# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 251# TIF_NOTIFY_RESUME calls resume_user_mode_work() 252# 253config HAVE_ARCH_TRACEHOOK 254 bool 255 256config HAVE_DMA_CONTIGUOUS 257 bool 258 259config GENERIC_SMP_IDLE_THREAD 260 bool 261 262config GENERIC_IDLE_POLL_SETUP 263 bool 264 265config ARCH_HAS_FORTIFY_SOURCE 266 bool 267 help 268 An architecture should select this when it can successfully 269 build and run with CONFIG_FORTIFY_SOURCE. 270 271# 272# Select if the arch provides a historic keepinit alias for the retain_initrd 273# command line option 274# 275config ARCH_HAS_KEEPINITRD 276 bool 277 278# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 279config ARCH_HAS_SET_MEMORY 280 bool 281 282# Select if arch has all set_direct_map_invalid/default() functions 283config ARCH_HAS_SET_DIRECT_MAP 284 bool 285 286# 287# Select if the architecture provides the arch_dma_set_uncached symbol to 288# either provide an uncached segment alias for a DMA allocation, or 289# to remap the page tables in place. 290# 291config ARCH_HAS_DMA_SET_UNCACHED 292 bool 293 294# 295# Select if the architectures provides the arch_dma_clear_uncached symbol 296# to undo an in-place page table remap for uncached access. 297# 298config ARCH_HAS_DMA_CLEAR_UNCACHED 299 bool 300 301config ARCH_HAS_CPU_FINALIZE_INIT 302 bool 303 304config HAVE_ARCH_THREAD_STRUCT_WHITELIST 305 bool 306 help 307 An architecture should select this to provide hardened usercopy 308 knowledge about what region of the thread_struct should be 309 whitelisted for copying to userspace. Normally this is only the 310 FPU registers. Specifically, arch_thread_struct_whitelist() 311 should be implemented. Without this, the entire thread_struct 312 field in task_struct will be left whitelisted. 313 314# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 315config ARCH_WANTS_DYNAMIC_TASK_STRUCT 316 bool 317 318config ARCH_WANTS_NO_INSTR 319 bool 320 help 321 An architecture should select this if the noinstr macro is being used on 322 functions to denote that the toolchain should avoid instrumenting such 323 functions and is required for correctness. 324 325config ARCH_32BIT_OFF_T 326 bool 327 depends on !64BIT 328 help 329 All new 32-bit architectures should have 64-bit off_t type on 330 userspace side which corresponds to the loff_t kernel type. This 331 is the requirement for modern ABIs. Some existing architectures 332 still support 32-bit off_t. This option is enabled for all such 333 architectures explicitly. 334 335# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 336config ARCH_32BIT_USTAT_F_TINODE 337 bool 338 339config HAVE_ASM_MODVERSIONS 340 bool 341 help 342 This symbol should be selected by an architecture if it provides 343 <asm/asm-prototypes.h> to support the module versioning for symbols 344 exported from assembly code. 345 346config HAVE_REGS_AND_STACK_ACCESS_API 347 bool 348 help 349 This symbol should be selected by an architecture if it supports 350 the API needed to access registers and stack entries from pt_regs, 351 declared in asm/ptrace.h 352 For example the kprobes-based event tracer needs this API. 353 354config HAVE_RSEQ 355 bool 356 depends on HAVE_REGS_AND_STACK_ACCESS_API 357 help 358 This symbol should be selected by an architecture if it 359 supports an implementation of restartable sequences. 360 361config HAVE_RUST 362 bool 363 help 364 This symbol should be selected by an architecture if it 365 supports Rust. 366 367config HAVE_FUNCTION_ARG_ACCESS_API 368 bool 369 help 370 This symbol should be selected by an architecture if it supports 371 the API needed to access function arguments from pt_regs, 372 declared in asm/ptrace.h 373 374config HAVE_HW_BREAKPOINT 375 bool 376 depends on PERF_EVENTS 377 378config HAVE_MIXED_BREAKPOINTS_REGS 379 bool 380 depends on HAVE_HW_BREAKPOINT 381 help 382 Depending on the arch implementation of hardware breakpoints, 383 some of them have separate registers for data and instruction 384 breakpoints addresses, others have mixed registers to store 385 them but define the access type in a control register. 386 Select this option if your arch implements breakpoints under the 387 latter fashion. 388 389config HAVE_USER_RETURN_NOTIFIER 390 bool 391 392config HAVE_PERF_EVENTS_NMI 393 bool 394 help 395 System hardware can generate an NMI using the perf event 396 subsystem. Also has support for calculating CPU cycle events 397 to determine how many clock cycles in a given period. 398 399config HAVE_HARDLOCKUP_DETECTOR_PERF 400 bool 401 depends on HAVE_PERF_EVENTS_NMI 402 help 403 The arch chooses to use the generic perf-NMI-based hardlockup 404 detector. Must define HAVE_PERF_EVENTS_NMI. 405 406config HAVE_HARDLOCKUP_DETECTOR_ARCH 407 bool 408 help 409 The arch provides its own hardlockup detector implementation instead 410 of the generic ones. 411 412 It uses the same command line parameters, and sysctl interface, 413 as the generic hardlockup detectors. 414 415config HAVE_PERF_REGS 416 bool 417 help 418 Support selective register dumps for perf events. This includes 419 bit-mapping of each registers and a unique architecture id. 420 421config HAVE_PERF_USER_STACK_DUMP 422 bool 423 help 424 Support user stack dumps for perf event samples. This needs 425 access to the user stack pointer which is not unified across 426 architectures. 427 428config HAVE_ARCH_JUMP_LABEL 429 bool 430 431config HAVE_ARCH_JUMP_LABEL_RELATIVE 432 bool 433 434config MMU_GATHER_TABLE_FREE 435 bool 436 437config MMU_GATHER_RCU_TABLE_FREE 438 bool 439 select MMU_GATHER_TABLE_FREE 440 441config MMU_GATHER_PAGE_SIZE 442 bool 443 444config MMU_GATHER_NO_RANGE 445 bool 446 select MMU_GATHER_MERGE_VMAS 447 448config MMU_GATHER_NO_FLUSH_CACHE 449 bool 450 451config MMU_GATHER_MERGE_VMAS 452 bool 453 454config MMU_GATHER_NO_GATHER 455 bool 456 depends on MMU_GATHER_TABLE_FREE 457 458config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 459 bool 460 help 461 Temporary select until all architectures can be converted to have 462 irqs disabled over activate_mm. Architectures that do IPI based TLB 463 shootdowns should enable this. 464 465# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 466# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 467# to/from kernel threads when the same mm is running on a lot of CPUs (a large 468# multi-threaded application), by reducing contention on the mm refcount. 469# 470# This can be disabled if the architecture ensures no CPUs are using an mm as a 471# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 472# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 473# final exit(2) TLB flush, for example. 474# 475# To implement this, an arch *must*: 476# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 477# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 478# converted already). 479config MMU_LAZY_TLB_REFCOUNT 480 def_bool y 481 depends on !MMU_LAZY_TLB_SHOOTDOWN 482 483# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 484# mm as a lazy tlb beyond its last reference count, by shooting down these 485# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 486# be using the mm as a lazy tlb, so that they may switch themselves to using 487# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 488# may be using mm as a lazy tlb mm. 489# 490# To implement this, an arch *must*: 491# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 492# at least all possible CPUs in which the mm is lazy. 493# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 494config MMU_LAZY_TLB_SHOOTDOWN 495 bool 496 497config ARCH_HAVE_NMI_SAFE_CMPXCHG 498 bool 499 500config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 501 bool 502 503config HAVE_ALIGNED_STRUCT_PAGE 504 bool 505 help 506 This makes sure that struct pages are double word aligned and that 507 e.g. the SLUB allocator can perform double word atomic operations 508 on a struct page for better performance. However selecting this 509 might increase the size of a struct page by a word. 510 511config HAVE_CMPXCHG_LOCAL 512 bool 513 514config HAVE_CMPXCHG_DOUBLE 515 bool 516 517config ARCH_WEAK_RELEASE_ACQUIRE 518 bool 519 520config ARCH_WANT_IPC_PARSE_VERSION 521 bool 522 523config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 524 bool 525 526config ARCH_WANT_OLD_COMPAT_IPC 527 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 528 bool 529 530config HAVE_ARCH_SECCOMP 531 bool 532 help 533 An arch should select this symbol to support seccomp mode 1 (the fixed 534 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 535 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 536 - __NR_seccomp_read_32 537 - __NR_seccomp_write_32 538 - __NR_seccomp_exit_32 539 - __NR_seccomp_sigreturn_32 540 541config HAVE_ARCH_SECCOMP_FILTER 542 bool 543 select HAVE_ARCH_SECCOMP 544 help 545 An arch should select this symbol if it provides all of these things: 546 - all the requirements for HAVE_ARCH_SECCOMP 547 - syscall_get_arch() 548 - syscall_get_arguments() 549 - syscall_rollback() 550 - syscall_set_return_value() 551 - SIGSYS siginfo_t support 552 - secure_computing is called from a ptrace_event()-safe context 553 - secure_computing return value is checked and a return value of -1 554 results in the system call being skipped immediately. 555 - seccomp syscall wired up 556 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 557 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 558 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 559 560config SECCOMP 561 prompt "Enable seccomp to safely execute untrusted bytecode" 562 def_bool y 563 depends on HAVE_ARCH_SECCOMP 564 help 565 This kernel feature is useful for number crunching applications 566 that may need to handle untrusted bytecode during their 567 execution. By using pipes or other transports made available 568 to the process as file descriptors supporting the read/write 569 syscalls, it's possible to isolate those applications in their 570 own address space using seccomp. Once seccomp is enabled via 571 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 572 disabled and the task is only allowed to execute a few safe 573 syscalls defined by each seccomp mode. 574 575 If unsure, say Y. 576 577config SECCOMP_FILTER 578 def_bool y 579 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 580 help 581 Enable tasks to build secure computing environments defined 582 in terms of Berkeley Packet Filter programs which implement 583 task-defined system call filtering polices. 584 585 See Documentation/userspace-api/seccomp_filter.rst for details. 586 587config SECCOMP_CACHE_DEBUG 588 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 589 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 590 depends on PROC_FS 591 help 592 This enables the /proc/pid/seccomp_cache interface to monitor 593 seccomp cache data. The file format is subject to change. Reading 594 the file requires CAP_SYS_ADMIN. 595 596 This option is for debugging only. Enabling presents the risk that 597 an adversary may be able to infer the seccomp filter logic. 598 599 If unsure, say N. 600 601config HAVE_ARCH_STACKLEAK 602 bool 603 help 604 An architecture should select this if it has the code which 605 fills the used part of the kernel stack with the STACKLEAK_POISON 606 value before returning from system calls. 607 608config HAVE_STACKPROTECTOR 609 bool 610 help 611 An arch should select this symbol if: 612 - it has implemented a stack canary (e.g. __stack_chk_guard) 613 614config STACKPROTECTOR 615 bool "Stack Protector buffer overflow detection" 616 depends on HAVE_STACKPROTECTOR 617 depends on $(cc-option,-fstack-protector) 618 default y 619 help 620 This option turns on the "stack-protector" GCC feature. This 621 feature puts, at the beginning of functions, a canary value on 622 the stack just before the return address, and validates 623 the value just before actually returning. Stack based buffer 624 overflows (that need to overwrite this return address) now also 625 overwrite the canary, which gets detected and the attack is then 626 neutralized via a kernel panic. 627 628 Functions will have the stack-protector canary logic added if they 629 have an 8-byte or larger character array on the stack. 630 631 This feature requires gcc version 4.2 or above, or a distribution 632 gcc with the feature backported ("-fstack-protector"). 633 634 On an x86 "defconfig" build, this feature adds canary checks to 635 about 3% of all kernel functions, which increases kernel code size 636 by about 0.3%. 637 638config STACKPROTECTOR_STRONG 639 bool "Strong Stack Protector" 640 depends on STACKPROTECTOR 641 depends on $(cc-option,-fstack-protector-strong) 642 default y 643 help 644 Functions will have the stack-protector canary logic added in any 645 of the following conditions: 646 647 - local variable's address used as part of the right hand side of an 648 assignment or function argument 649 - local variable is an array (or union containing an array), 650 regardless of array type or length 651 - uses register local variables 652 653 This feature requires gcc version 4.9 or above, or a distribution 654 gcc with the feature backported ("-fstack-protector-strong"). 655 656 On an x86 "defconfig" build, this feature adds canary checks to 657 about 20% of all kernel functions, which increases the kernel code 658 size by about 2%. 659 660config ARCH_SUPPORTS_SHADOW_CALL_STACK 661 bool 662 help 663 An architecture should select this if it supports the compiler's 664 Shadow Call Stack and implements runtime support for shadow stack 665 switching. 666 667config SHADOW_CALL_STACK 668 bool "Shadow Call Stack" 669 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 670 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 671 help 672 This option enables the compiler's Shadow Call Stack, which 673 uses a shadow stack to protect function return addresses from 674 being overwritten by an attacker. More information can be found 675 in the compiler's documentation: 676 677 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 678 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 679 680 Note that security guarantees in the kernel differ from the 681 ones documented for user space. The kernel must store addresses 682 of shadow stacks in memory, which means an attacker capable of 683 reading and writing arbitrary memory may be able to locate them 684 and hijack control flow by modifying the stacks. 685 686config DYNAMIC_SCS 687 bool 688 help 689 Set by the arch code if it relies on code patching to insert the 690 shadow call stack push and pop instructions rather than on the 691 compiler. 692 693config LTO 694 bool 695 help 696 Selected if the kernel will be built using the compiler's LTO feature. 697 698config LTO_CLANG 699 bool 700 select LTO 701 help 702 Selected if the kernel will be built using Clang's LTO feature. 703 704config ARCH_SUPPORTS_LTO_CLANG 705 bool 706 help 707 An architecture should select this option if it supports: 708 - compiling with Clang, 709 - compiling inline assembly with Clang's integrated assembler, 710 - and linking with LLD. 711 712config ARCH_SUPPORTS_LTO_CLANG_THIN 713 bool 714 help 715 An architecture should select this option if it can support Clang's 716 ThinLTO mode. 717 718config HAS_LTO_CLANG 719 def_bool y 720 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 721 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 722 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 723 depends on ARCH_SUPPORTS_LTO_CLANG 724 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 725 # https://github.com/ClangBuiltLinux/linux/issues/1721 726 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 727 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 728 depends on !GCOV_KERNEL 729 help 730 The compiler and Kconfig options support building with Clang's 731 LTO. 732 733choice 734 prompt "Link Time Optimization (LTO)" 735 default LTO_NONE 736 help 737 This option enables Link Time Optimization (LTO), which allows the 738 compiler to optimize binaries globally. 739 740 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 741 so it's disabled by default. 742 743config LTO_NONE 744 bool "None" 745 help 746 Build the kernel normally, without Link Time Optimization (LTO). 747 748config LTO_CLANG_FULL 749 bool "Clang Full LTO (EXPERIMENTAL)" 750 depends on HAS_LTO_CLANG 751 depends on !COMPILE_TEST 752 select LTO_CLANG 753 help 754 This option enables Clang's full Link Time Optimization (LTO), which 755 allows the compiler to optimize the kernel globally. If you enable 756 this option, the compiler generates LLVM bitcode instead of ELF 757 object files, and the actual compilation from bitcode happens at 758 the LTO link step, which may take several minutes depending on the 759 kernel configuration. More information can be found from LLVM's 760 documentation: 761 762 https://llvm.org/docs/LinkTimeOptimization.html 763 764 During link time, this option can use a large amount of RAM, and 765 may take much longer than the ThinLTO option. 766 767config LTO_CLANG_THIN 768 bool "Clang ThinLTO (EXPERIMENTAL)" 769 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 770 select LTO_CLANG 771 help 772 This option enables Clang's ThinLTO, which allows for parallel 773 optimization and faster incremental compiles compared to the 774 CONFIG_LTO_CLANG_FULL option. More information can be found 775 from Clang's documentation: 776 777 https://clang.llvm.org/docs/ThinLTO.html 778 779 If unsure, say Y. 780endchoice 781 782config ARCH_SUPPORTS_CFI_CLANG 783 bool 784 help 785 An architecture should select this option if it can support Clang's 786 Control-Flow Integrity (CFI) checking. 787 788config ARCH_USES_CFI_TRAPS 789 bool 790 791config CFI_CLANG 792 bool "Use Clang's Control Flow Integrity (CFI)" 793 depends on ARCH_SUPPORTS_CFI_CLANG 794 depends on $(cc-option,-fsanitize=kcfi) 795 help 796 This option enables Clang’s forward-edge Control Flow Integrity 797 (CFI) checking, where the compiler injects a runtime check to each 798 indirect function call to ensure the target is a valid function with 799 the correct static type. This restricts possible call targets and 800 makes it more difficult for an attacker to exploit bugs that allow 801 the modification of stored function pointers. More information can be 802 found from Clang's documentation: 803 804 https://clang.llvm.org/docs/ControlFlowIntegrity.html 805 806config CFI_PERMISSIVE 807 bool "Use CFI in permissive mode" 808 depends on CFI_CLANG 809 help 810 When selected, Control Flow Integrity (CFI) violations result in a 811 warning instead of a kernel panic. This option should only be used 812 for finding indirect call type mismatches during development. 813 814 If unsure, say N. 815 816config HAVE_ARCH_WITHIN_STACK_FRAMES 817 bool 818 help 819 An architecture should select this if it can walk the kernel stack 820 frames to determine if an object is part of either the arguments 821 or local variables (i.e. that it excludes saved return addresses, 822 and similar) by implementing an inline arch_within_stack_frames(), 823 which is used by CONFIG_HARDENED_USERCOPY. 824 825config HAVE_CONTEXT_TRACKING_USER 826 bool 827 help 828 Provide kernel/user boundaries probes necessary for subsystems 829 that need it, such as userspace RCU extended quiescent state. 830 Syscalls need to be wrapped inside user_exit()-user_enter(), either 831 optimized behind static key or through the slow path using TIF_NOHZ 832 flag. Exceptions handlers must be wrapped as well. Irqs are already 833 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 834 handling on irq exit still need to be protected. 835 836config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 837 bool 838 help 839 Architecture neither relies on exception_enter()/exception_exit() 840 nor on schedule_user(). Also preempt_schedule_notrace() and 841 preempt_schedule_irq() can't be called in a preemptible section 842 while context tracking is CONTEXT_USER. This feature reflects a sane 843 entry implementation where the following requirements are met on 844 critical entry code, ie: before user_exit() or after user_enter(): 845 846 - Critical entry code isn't preemptible (or better yet: 847 not interruptible). 848 - No use of RCU read side critical sections, unless ct_nmi_enter() 849 got called. 850 - No use of instrumentation, unless instrumentation_begin() got 851 called. 852 853config HAVE_TIF_NOHZ 854 bool 855 help 856 Arch relies on TIF_NOHZ and syscall slow path to implement context 857 tracking calls to user_enter()/user_exit(). 858 859config HAVE_VIRT_CPU_ACCOUNTING 860 bool 861 862config HAVE_VIRT_CPU_ACCOUNTING_IDLE 863 bool 864 help 865 Architecture has its own way to account idle CPU time and therefore 866 doesn't implement vtime_account_idle(). 867 868config ARCH_HAS_SCALED_CPUTIME 869 bool 870 871config HAVE_VIRT_CPU_ACCOUNTING_GEN 872 bool 873 default y if 64BIT 874 help 875 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 876 Before enabling this option, arch code must be audited 877 to ensure there are no races in concurrent read/write of 878 cputime_t. For example, reading/writing 64-bit cputime_t on 879 some 32-bit arches may require multiple accesses, so proper 880 locking is needed to protect against concurrent accesses. 881 882config HAVE_IRQ_TIME_ACCOUNTING 883 bool 884 help 885 Archs need to ensure they use a high enough resolution clock to 886 support irq time accounting and then call enable_sched_clock_irqtime(). 887 888config HAVE_MOVE_PUD 889 bool 890 help 891 Architectures that select this are able to move page tables at the 892 PUD level. If there are only 3 page table levels, the move effectively 893 happens at the PGD level. 894 895config HAVE_MOVE_PMD 896 bool 897 help 898 Archs that select this are able to move page tables at the PMD level. 899 900config HAVE_ARCH_TRANSPARENT_HUGEPAGE 901 bool 902 903config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 904 bool 905 906config HAVE_ARCH_HUGE_VMAP 907 bool 908 909# 910# Archs that select this would be capable of PMD-sized vmaps (i.e., 911# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 912# must be used to enable allocations to use hugepages. 913# 914config HAVE_ARCH_HUGE_VMALLOC 915 depends on HAVE_ARCH_HUGE_VMAP 916 bool 917 918config ARCH_WANT_HUGE_PMD_SHARE 919 bool 920 921# Archs that want to use pmd_mkwrite on kernel memory need it defined even 922# if there are no userspace memory management features that use it 923config ARCH_WANT_KERNEL_PMD_MKWRITE 924 bool 925 926config ARCH_WANT_PMD_MKWRITE 927 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 928 929config HAVE_ARCH_SOFT_DIRTY 930 bool 931 932config HAVE_MOD_ARCH_SPECIFIC 933 bool 934 help 935 The arch uses struct mod_arch_specific to store data. Many arches 936 just need a simple module loader without arch specific data - those 937 should not enable this. 938 939config MODULES_USE_ELF_RELA 940 bool 941 help 942 Modules only use ELF RELA relocations. Modules with ELF REL 943 relocations will give an error. 944 945config MODULES_USE_ELF_REL 946 bool 947 help 948 Modules only use ELF REL relocations. Modules with ELF RELA 949 relocations will give an error. 950 951config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 952 bool 953 help 954 For architectures like powerpc/32 which have constraints on module 955 allocation and need to allocate module data outside of module area. 956 957config HAVE_IRQ_EXIT_ON_IRQ_STACK 958 bool 959 help 960 Architecture doesn't only execute the irq handler on the irq stack 961 but also irq_exit(). This way we can process softirqs on this irq 962 stack instead of switching to a new one when we call __do_softirq() 963 in the end of an hardirq. 964 This spares a stack switch and improves cache usage on softirq 965 processing. 966 967config HAVE_SOFTIRQ_ON_OWN_STACK 968 bool 969 help 970 Architecture provides a function to run __do_softirq() on a 971 separate stack. 972 973config SOFTIRQ_ON_OWN_STACK 974 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 975 976config ALTERNATE_USER_ADDRESS_SPACE 977 bool 978 help 979 Architectures set this when the CPU uses separate address 980 spaces for kernel and user space pointers. In this case, the 981 access_ok() check on a __user pointer is skipped. 982 983config PGTABLE_LEVELS 984 int 985 default 2 986 987config ARCH_HAS_ELF_RANDOMIZE 988 bool 989 help 990 An architecture supports choosing randomized locations for 991 stack, mmap, brk, and ET_DYN. Defined functions: 992 - arch_mmap_rnd() 993 - arch_randomize_brk() 994 995config HAVE_ARCH_MMAP_RND_BITS 996 bool 997 help 998 An arch should select this symbol if it supports setting a variable 999 number of bits for use in establishing the base address for mmap 1000 allocations, has MMU enabled and provides values for both: 1001 - ARCH_MMAP_RND_BITS_MIN 1002 - ARCH_MMAP_RND_BITS_MAX 1003 1004config HAVE_EXIT_THREAD 1005 bool 1006 help 1007 An architecture implements exit_thread. 1008 1009config ARCH_MMAP_RND_BITS_MIN 1010 int 1011 1012config ARCH_MMAP_RND_BITS_MAX 1013 int 1014 1015config ARCH_MMAP_RND_BITS_DEFAULT 1016 int 1017 1018config ARCH_MMAP_RND_BITS 1019 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1020 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1021 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1022 default ARCH_MMAP_RND_BITS_MIN 1023 depends on HAVE_ARCH_MMAP_RND_BITS 1024 help 1025 This value can be used to select the number of bits to use to 1026 determine the random offset to the base address of vma regions 1027 resulting from mmap allocations. This value will be bounded 1028 by the architecture's minimum and maximum supported values. 1029 1030 This value can be changed after boot using the 1031 /proc/sys/vm/mmap_rnd_bits tunable 1032 1033config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1034 bool 1035 help 1036 An arch should select this symbol if it supports running applications 1037 in compatibility mode, supports setting a variable number of bits for 1038 use in establishing the base address for mmap allocations, has MMU 1039 enabled and provides values for both: 1040 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1041 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1042 1043config ARCH_MMAP_RND_COMPAT_BITS_MIN 1044 int 1045 1046config ARCH_MMAP_RND_COMPAT_BITS_MAX 1047 int 1048 1049config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1050 int 1051 1052config ARCH_MMAP_RND_COMPAT_BITS 1053 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1054 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1055 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1056 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1057 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1058 help 1059 This value can be used to select the number of bits to use to 1060 determine the random offset to the base address of vma regions 1061 resulting from mmap allocations for compatible applications This 1062 value will be bounded by the architecture's minimum and maximum 1063 supported values. 1064 1065 This value can be changed after boot using the 1066 /proc/sys/vm/mmap_rnd_compat_bits tunable 1067 1068config HAVE_ARCH_COMPAT_MMAP_BASES 1069 bool 1070 help 1071 This allows 64bit applications to invoke 32-bit mmap() syscall 1072 and vice-versa 32-bit applications to call 64-bit mmap(). 1073 Required for applications doing different bitness syscalls. 1074 1075config PAGE_SIZE_LESS_THAN_64KB 1076 def_bool y 1077 depends on !ARM64_64K_PAGES 1078 depends on !PAGE_SIZE_64KB 1079 depends on !PARISC_PAGE_SIZE_64KB 1080 depends on PAGE_SIZE_LESS_THAN_256KB 1081 1082config PAGE_SIZE_LESS_THAN_256KB 1083 def_bool y 1084 depends on !PAGE_SIZE_256KB 1085 1086# This allows to use a set of generic functions to determine mmap base 1087# address by giving priority to top-down scheme only if the process 1088# is not in legacy mode (compat task, unlimited stack size or 1089# sysctl_legacy_va_layout). 1090# Architecture that selects this option can provide its own version of: 1091# - STACK_RND_MASK 1092config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1093 bool 1094 depends on MMU 1095 select ARCH_HAS_ELF_RANDOMIZE 1096 1097config HAVE_OBJTOOL 1098 bool 1099 1100config HAVE_JUMP_LABEL_HACK 1101 bool 1102 1103config HAVE_NOINSTR_HACK 1104 bool 1105 1106config HAVE_NOINSTR_VALIDATION 1107 bool 1108 1109config HAVE_UACCESS_VALIDATION 1110 bool 1111 select OBJTOOL 1112 1113config HAVE_STACK_VALIDATION 1114 bool 1115 help 1116 Architecture supports objtool compile-time frame pointer rule 1117 validation. 1118 1119config HAVE_RELIABLE_STACKTRACE 1120 bool 1121 help 1122 Architecture has either save_stack_trace_tsk_reliable() or 1123 arch_stack_walk_reliable() function which only returns a stack trace 1124 if it can guarantee the trace is reliable. 1125 1126config HAVE_ARCH_HASH 1127 bool 1128 default n 1129 help 1130 If this is set, the architecture provides an <asm/hash.h> 1131 file which provides platform-specific implementations of some 1132 functions in <linux/hash.h> or fs/namei.c. 1133 1134config HAVE_ARCH_NVRAM_OPS 1135 bool 1136 1137config ISA_BUS_API 1138 def_bool ISA 1139 1140# 1141# ABI hall of shame 1142# 1143config CLONE_BACKWARDS 1144 bool 1145 help 1146 Architecture has tls passed as the 4th argument of clone(2), 1147 not the 5th one. 1148 1149config CLONE_BACKWARDS2 1150 bool 1151 help 1152 Architecture has the first two arguments of clone(2) swapped. 1153 1154config CLONE_BACKWARDS3 1155 bool 1156 help 1157 Architecture has tls passed as the 3rd argument of clone(2), 1158 not the 5th one. 1159 1160config ODD_RT_SIGACTION 1161 bool 1162 help 1163 Architecture has unusual rt_sigaction(2) arguments 1164 1165config OLD_SIGSUSPEND 1166 bool 1167 help 1168 Architecture has old sigsuspend(2) syscall, of one-argument variety 1169 1170config OLD_SIGSUSPEND3 1171 bool 1172 help 1173 Even weirder antique ABI - three-argument sigsuspend(2) 1174 1175config OLD_SIGACTION 1176 bool 1177 help 1178 Architecture has old sigaction(2) syscall. Nope, not the same 1179 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1180 but fairly different variant of sigaction(2), thanks to OSF/1 1181 compatibility... 1182 1183config COMPAT_OLD_SIGACTION 1184 bool 1185 1186config COMPAT_32BIT_TIME 1187 bool "Provide system calls for 32-bit time_t" 1188 default !64BIT || COMPAT 1189 help 1190 This enables 32 bit time_t support in addition to 64 bit time_t support. 1191 This is relevant on all 32-bit architectures, and 64-bit architectures 1192 as part of compat syscall handling. 1193 1194config ARCH_NO_PREEMPT 1195 bool 1196 1197config ARCH_SUPPORTS_RT 1198 bool 1199 1200config CPU_NO_EFFICIENT_FFS 1201 def_bool n 1202 1203config HAVE_ARCH_VMAP_STACK 1204 def_bool n 1205 help 1206 An arch should select this symbol if it can support kernel stacks 1207 in vmalloc space. This means: 1208 1209 - vmalloc space must be large enough to hold many kernel stacks. 1210 This may rule out many 32-bit architectures. 1211 1212 - Stacks in vmalloc space need to work reliably. For example, if 1213 vmap page tables are created on demand, either this mechanism 1214 needs to work while the stack points to a virtual address with 1215 unpopulated page tables or arch code (switch_to() and switch_mm(), 1216 most likely) needs to ensure that the stack's page table entries 1217 are populated before running on a possibly unpopulated stack. 1218 1219 - If the stack overflows into a guard page, something reasonable 1220 should happen. The definition of "reasonable" is flexible, but 1221 instantly rebooting without logging anything would be unfriendly. 1222 1223config VMAP_STACK 1224 default y 1225 bool "Use a virtually-mapped stack" 1226 depends on HAVE_ARCH_VMAP_STACK 1227 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1228 help 1229 Enable this if you want the use virtually-mapped kernel stacks 1230 with guard pages. This causes kernel stack overflows to be 1231 caught immediately rather than causing difficult-to-diagnose 1232 corruption. 1233 1234 To use this with software KASAN modes, the architecture must support 1235 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1236 must be enabled. 1237 1238config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1239 def_bool n 1240 help 1241 An arch should select this symbol if it can support kernel stack 1242 offset randomization with calls to add_random_kstack_offset() 1243 during syscall entry and choose_random_kstack_offset() during 1244 syscall exit. Careful removal of -fstack-protector-strong and 1245 -fstack-protector should also be applied to the entry code and 1246 closely examined, as the artificial stack bump looks like an array 1247 to the compiler, so it will attempt to add canary checks regardless 1248 of the static branch state. 1249 1250config RANDOMIZE_KSTACK_OFFSET 1251 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1252 default y 1253 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1254 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1255 help 1256 The kernel stack offset can be randomized (after pt_regs) by 1257 roughly 5 bits of entropy, frustrating memory corruption 1258 attacks that depend on stack address determinism or 1259 cross-syscall address exposures. 1260 1261 The feature is controlled via the "randomize_kstack_offset=on/off" 1262 kernel boot param, and if turned off has zero overhead due to its use 1263 of static branches (see JUMP_LABEL). 1264 1265 If unsure, say Y. 1266 1267config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1268 bool "Default state of kernel stack offset randomization" 1269 depends on RANDOMIZE_KSTACK_OFFSET 1270 help 1271 Kernel stack offset randomization is controlled by kernel boot param 1272 "randomize_kstack_offset=on/off", and this config chooses the default 1273 boot state. 1274 1275config ARCH_OPTIONAL_KERNEL_RWX 1276 def_bool n 1277 1278config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1279 def_bool n 1280 1281config ARCH_HAS_STRICT_KERNEL_RWX 1282 def_bool n 1283 1284config STRICT_KERNEL_RWX 1285 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1286 depends on ARCH_HAS_STRICT_KERNEL_RWX 1287 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1288 help 1289 If this is set, kernel text and rodata memory will be made read-only, 1290 and non-text memory will be made non-executable. This provides 1291 protection against certain security exploits (e.g. executing the heap 1292 or modifying text) 1293 1294 These features are considered standard security practice these days. 1295 You should say Y here in almost all cases. 1296 1297config ARCH_HAS_STRICT_MODULE_RWX 1298 def_bool n 1299 1300config STRICT_MODULE_RWX 1301 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1302 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1303 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1304 help 1305 If this is set, module text and rodata memory will be made read-only, 1306 and non-text memory will be made non-executable. This provides 1307 protection against certain security exploits (e.g. writing to text) 1308 1309# select if the architecture provides an asm/dma-direct.h header 1310config ARCH_HAS_PHYS_TO_DMA 1311 bool 1312 1313config HAVE_ARCH_COMPILER_H 1314 bool 1315 help 1316 An architecture can select this if it provides an 1317 asm/compiler.h header that should be included after 1318 linux/compiler-*.h in order to override macro definitions that those 1319 headers generally provide. 1320 1321config HAVE_ARCH_PREL32_RELOCATIONS 1322 bool 1323 help 1324 May be selected by an architecture if it supports place-relative 1325 32-bit relocations, both in the toolchain and in the module loader, 1326 in which case relative references can be used in special sections 1327 for PCI fixup, initcalls etc which are only half the size on 64 bit 1328 architectures, and don't require runtime relocation on relocatable 1329 kernels. 1330 1331config ARCH_USE_MEMREMAP_PROT 1332 bool 1333 1334config LOCK_EVENT_COUNTS 1335 bool "Locking event counts collection" 1336 depends on DEBUG_FS 1337 help 1338 Enable light-weight counting of various locking related events 1339 in the system with minimal performance impact. This reduces 1340 the chance of application behavior change because of timing 1341 differences. The counts are reported via debugfs. 1342 1343# Select if the architecture has support for applying RELR relocations. 1344config ARCH_HAS_RELR 1345 bool 1346 1347config RELR 1348 bool "Use RELR relocation packing" 1349 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1350 default y 1351 help 1352 Store the kernel's dynamic relocations in the RELR relocation packing 1353 format. Requires a compatible linker (LLD supports this feature), as 1354 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1355 are compatible). 1356 1357config ARCH_HAS_MEM_ENCRYPT 1358 bool 1359 1360config ARCH_HAS_CC_PLATFORM 1361 bool 1362 1363config HAVE_SPARSE_SYSCALL_NR 1364 bool 1365 help 1366 An architecture should select this if its syscall numbering is sparse 1367 to save space. For example, MIPS architecture has a syscall array with 1368 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1369 related optimizations for a given architecture. 1370 1371config ARCH_HAS_VDSO_DATA 1372 bool 1373 1374config HAVE_STATIC_CALL 1375 bool 1376 1377config HAVE_STATIC_CALL_INLINE 1378 bool 1379 depends on HAVE_STATIC_CALL 1380 select OBJTOOL 1381 1382config HAVE_PREEMPT_DYNAMIC 1383 bool 1384 1385config HAVE_PREEMPT_DYNAMIC_CALL 1386 bool 1387 depends on HAVE_STATIC_CALL 1388 select HAVE_PREEMPT_DYNAMIC 1389 help 1390 An architecture should select this if it can handle the preemption 1391 model being selected at boot time using static calls. 1392 1393 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1394 preemption function will be patched directly. 1395 1396 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1397 call to a preemption function will go through a trampoline, and the 1398 trampoline will be patched. 1399 1400 It is strongly advised to support inline static call to avoid any 1401 overhead. 1402 1403config HAVE_PREEMPT_DYNAMIC_KEY 1404 bool 1405 depends on HAVE_ARCH_JUMP_LABEL 1406 select HAVE_PREEMPT_DYNAMIC 1407 help 1408 An architecture should select this if it can handle the preemption 1409 model being selected at boot time using static keys. 1410 1411 Each preemption function will be given an early return based on a 1412 static key. This should have slightly lower overhead than non-inline 1413 static calls, as this effectively inlines each trampoline into the 1414 start of its callee. This may avoid redundant work, and may 1415 integrate better with CFI schemes. 1416 1417 This will have greater overhead than using inline static calls as 1418 the call to the preemption function cannot be entirely elided. 1419 1420config ARCH_WANT_LD_ORPHAN_WARN 1421 bool 1422 help 1423 An arch should select this symbol once all linker sections are explicitly 1424 included, size-asserted, or discarded in the linker scripts. This is 1425 important because we never want expected sections to be placed heuristically 1426 by the linker, since the locations of such sections can change between linker 1427 versions. 1428 1429config HAVE_ARCH_PFN_VALID 1430 bool 1431 1432config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1433 bool 1434 1435config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1436 bool 1437 1438config ARCH_SPLIT_ARG64 1439 bool 1440 help 1441 If a 32-bit architecture requires 64-bit arguments to be split into 1442 pairs of 32-bit arguments, select this option. 1443 1444config ARCH_HAS_ELFCORE_COMPAT 1445 bool 1446 1447config ARCH_HAS_PARANOID_L1D_FLUSH 1448 bool 1449 1450config ARCH_HAVE_TRACE_MMIO_ACCESS 1451 bool 1452 1453config DYNAMIC_SIGFRAME 1454 bool 1455 1456# Select, if arch has a named attribute group bound to NUMA device nodes. 1457config HAVE_ARCH_NODE_DEV_GROUP 1458 bool 1459 1460config ARCH_HAS_HW_PTE_YOUNG 1461 bool 1462 help 1463 Architectures that select this option are capable of setting the 1464 accessed bit in PTE entries when using them as part of linear address 1465 translations. Architectures that require runtime check should select 1466 this option and override arch_has_hw_pte_young(). 1467 1468config ARCH_HAS_NONLEAF_PMD_YOUNG 1469 bool 1470 help 1471 Architectures that select this option are capable of setting the 1472 accessed bit in non-leaf PMD entries when using them as part of linear 1473 address translations. Page table walkers that clear the accessed bit 1474 may use this capability to reduce their search space. 1475 1476source "kernel/gcov/Kconfig" 1477 1478source "scripts/gcc-plugins/Kconfig" 1479 1480config FUNCTION_ALIGNMENT_4B 1481 bool 1482 1483config FUNCTION_ALIGNMENT_8B 1484 bool 1485 1486config FUNCTION_ALIGNMENT_16B 1487 bool 1488 1489config FUNCTION_ALIGNMENT_32B 1490 bool 1491 1492config FUNCTION_ALIGNMENT_64B 1493 bool 1494 1495config FUNCTION_ALIGNMENT 1496 int 1497 default 64 if FUNCTION_ALIGNMENT_64B 1498 default 32 if FUNCTION_ALIGNMENT_32B 1499 default 16 if FUNCTION_ALIGNMENT_16B 1500 default 8 if FUNCTION_ALIGNMENT_8B 1501 default 4 if FUNCTION_ALIGNMENT_4B 1502 default 0 1503 1504endmenu 1505