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 CRASH_CORE 15 bool 16 17config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21config KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config ARCH_HAS_SUBPAGE_FAULTS 28 bool 29 help 30 Select if the architecture can check permissions at sub-page 31 granularity (e.g. arm64 MTE). The probe_user_*() functions 32 must be implemented. 33 34config HOTPLUG_SMT 35 bool 36 37config GENERIC_ENTRY 38 bool 39 40config KPROBES 41 bool "Kprobes" 42 depends on MODULES 43 depends on HAVE_KPROBES 44 select KALLSYMS 45 select TASKS_RCU if PREEMPTION 46 help 47 Kprobes allows you to trap at almost any kernel address and 48 execute a callback function. register_kprobe() establishes 49 a probepoint and specifies the callback. Kprobes is useful 50 for kernel debugging, non-intrusive instrumentation and testing. 51 If in doubt, say "N". 52 53config JUMP_LABEL 54 bool "Optimize very unlikely/likely branches" 55 depends on HAVE_ARCH_JUMP_LABEL 56 select OBJTOOL if HAVE_JUMP_LABEL_HACK 57 help 58 This option enables a transparent branch optimization that 59 makes certain almost-always-true or almost-always-false branch 60 conditions even cheaper to execute within the kernel. 61 62 Certain performance-sensitive kernel code, such as trace points, 63 scheduler functionality, networking code and KVM have such 64 branches and include support for this optimization technique. 65 66 If it is detected that the compiler has support for "asm goto", 67 the kernel will compile such branches with just a nop 68 instruction. When the condition flag is toggled to true, the 69 nop will be converted to a jump instruction to execute the 70 conditional block of instructions. 71 72 This technique lowers overhead and stress on the branch prediction 73 of the processor and generally makes the kernel faster. The update 74 of the condition is slower, but those are always very rare. 75 76 ( On 32-bit x86, the necessary options added to the compiler 77 flags may increase the size of the kernel slightly. ) 78 79config STATIC_KEYS_SELFTEST 80 bool "Static key selftest" 81 depends on JUMP_LABEL 82 help 83 Boot time self-test of the branch patching code. 84 85config STATIC_CALL_SELFTEST 86 bool "Static call selftest" 87 depends on HAVE_STATIC_CALL 88 help 89 Boot time self-test of the call patching code. 90 91config OPTPROBES 92 def_bool y 93 depends on KPROBES && HAVE_OPTPROBES 94 select TASKS_RCU if PREEMPTION 95 96config KPROBES_ON_FTRACE 97 def_bool y 98 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 99 depends on DYNAMIC_FTRACE_WITH_REGS 100 help 101 If function tracer is enabled and the arch supports full 102 passing of pt_regs to function tracing, then kprobes can 103 optimize on top of function tracing. 104 105config UPROBES 106 def_bool n 107 depends on ARCH_SUPPORTS_UPROBES 108 help 109 Uprobes is the user-space counterpart to kprobes: they 110 enable instrumentation applications (such as 'perf probe') 111 to establish unintrusive probes in user-space binaries and 112 libraries, by executing handler functions when the probes 113 are hit by user-space applications. 114 115 ( These probes come in the form of single-byte breakpoints, 116 managed by the kernel and kept transparent to the probed 117 application. ) 118 119config HAVE_64BIT_ALIGNED_ACCESS 120 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 121 help 122 Some architectures require 64 bit accesses to be 64 bit 123 aligned, which also requires structs containing 64 bit values 124 to be 64 bit aligned too. This includes some 32 bit 125 architectures which can do 64 bit accesses, as well as 64 bit 126 architectures without unaligned access. 127 128 This symbol should be selected by an architecture if 64 bit 129 accesses are required to be 64 bit aligned in this way even 130 though it is not a 64 bit architecture. 131 132 See Documentation/core-api/unaligned-memory-access.rst for 133 more information on the topic of unaligned memory accesses. 134 135config HAVE_EFFICIENT_UNALIGNED_ACCESS 136 bool 137 help 138 Some architectures are unable to perform unaligned accesses 139 without the use of get_unaligned/put_unaligned. Others are 140 unable to perform such accesses efficiently (e.g. trap on 141 unaligned access and require fixing it up in the exception 142 handler.) 143 144 This symbol should be selected by an architecture if it can 145 perform unaligned accesses efficiently to allow different 146 code paths to be selected for these cases. Some network 147 drivers, for example, could opt to not fix up alignment 148 problems with received packets if doing so would not help 149 much. 150 151 See Documentation/core-api/unaligned-memory-access.rst for more 152 information on the topic of unaligned memory accesses. 153 154config ARCH_USE_BUILTIN_BSWAP 155 bool 156 help 157 Modern versions of GCC (since 4.4) have builtin functions 158 for handling byte-swapping. Using these, instead of the old 159 inline assembler that the architecture code provides in the 160 __arch_bswapXX() macros, allows the compiler to see what's 161 happening and offers more opportunity for optimisation. In 162 particular, the compiler will be able to combine the byteswap 163 with a nearby load or store and use load-and-swap or 164 store-and-swap instructions if the architecture has them. It 165 should almost *never* result in code which is worse than the 166 hand-coded assembler in <asm/swab.h>. But just in case it 167 does, the use of the builtins is optional. 168 169 Any architecture with load-and-swap or store-and-swap 170 instructions should set this. And it shouldn't hurt to set it 171 on architectures that don't have such instructions. 172 173config KRETPROBES 174 def_bool y 175 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 176 177config KRETPROBE_ON_RETHOOK 178 def_bool y 179 depends on HAVE_RETHOOK 180 depends on KRETPROBES 181 select RETHOOK 182 183config USER_RETURN_NOTIFIER 184 bool 185 depends on HAVE_USER_RETURN_NOTIFIER 186 help 187 Provide a kernel-internal notification when a cpu is about to 188 switch to user mode. 189 190config HAVE_IOREMAP_PROT 191 bool 192 193config HAVE_KPROBES 194 bool 195 196config HAVE_KRETPROBES 197 bool 198 199config HAVE_OPTPROBES 200 bool 201 202config HAVE_KPROBES_ON_FTRACE 203 bool 204 205config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 206 bool 207 help 208 Since kretprobes modifies return address on the stack, the 209 stacktrace may see the kretprobe trampoline address instead 210 of correct one. If the architecture stacktrace code and 211 unwinder can adjust such entries, select this configuration. 212 213config HAVE_FUNCTION_ERROR_INJECTION 214 bool 215 216config HAVE_NMI 217 bool 218 219config HAVE_FUNCTION_DESCRIPTORS 220 bool 221 222config TRACE_IRQFLAGS_SUPPORT 223 bool 224 225config TRACE_IRQFLAGS_NMI_SUPPORT 226 bool 227 228# 229# An arch should select this if it provides all these things: 230# 231# task_pt_regs() in asm/processor.h or asm/ptrace.h 232# arch_has_single_step() if there is hardware single-step support 233# arch_has_block_step() if there is hardware block-step support 234# asm/syscall.h supplying asm-generic/syscall.h interface 235# linux/regset.h user_regset interfaces 236# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 237# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 238# TIF_NOTIFY_RESUME calls resume_user_mode_work() 239# 240config HAVE_ARCH_TRACEHOOK 241 bool 242 243config HAVE_DMA_CONTIGUOUS 244 bool 245 246config GENERIC_SMP_IDLE_THREAD 247 bool 248 249config GENERIC_IDLE_POLL_SETUP 250 bool 251 252config ARCH_HAS_FORTIFY_SOURCE 253 bool 254 help 255 An architecture should select this when it can successfully 256 build and run with CONFIG_FORTIFY_SOURCE. 257 258# 259# Select if the arch provides a historic keepinit alias for the retain_initrd 260# command line option 261# 262config ARCH_HAS_KEEPINITRD 263 bool 264 265# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 266config ARCH_HAS_SET_MEMORY 267 bool 268 269# Select if arch has all set_direct_map_invalid/default() functions 270config ARCH_HAS_SET_DIRECT_MAP 271 bool 272 273# 274# Select if the architecture provides the arch_dma_set_uncached symbol to 275# either provide an uncached segment alias for a DMA allocation, or 276# to remap the page tables in place. 277# 278config ARCH_HAS_DMA_SET_UNCACHED 279 bool 280 281# 282# Select if the architectures provides the arch_dma_clear_uncached symbol 283# to undo an in-place page table remap for uncached access. 284# 285config ARCH_HAS_DMA_CLEAR_UNCACHED 286 bool 287 288# Select if arch init_task must go in the __init_task_data section 289config ARCH_TASK_STRUCT_ON_STACK 290 bool 291 292# Select if arch has its private alloc_task_struct() function 293config ARCH_TASK_STRUCT_ALLOCATOR 294 bool 295 296config HAVE_ARCH_THREAD_STRUCT_WHITELIST 297 bool 298 depends on !ARCH_TASK_STRUCT_ALLOCATOR 299 help 300 An architecture should select this to provide hardened usercopy 301 knowledge about what region of the thread_struct should be 302 whitelisted for copying to userspace. Normally this is only the 303 FPU registers. Specifically, arch_thread_struct_whitelist() 304 should be implemented. Without this, the entire thread_struct 305 field in task_struct will be left whitelisted. 306 307# Select if arch has its private alloc_thread_stack() function 308config ARCH_THREAD_STACK_ALLOCATOR 309 bool 310 311# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 312config ARCH_WANTS_DYNAMIC_TASK_STRUCT 313 bool 314 315config ARCH_WANTS_NO_INSTR 316 bool 317 help 318 An architecture should select this if the noinstr macro is being used on 319 functions to denote that the toolchain should avoid instrumenting such 320 functions and is required for correctness. 321 322config ARCH_32BIT_OFF_T 323 bool 324 depends on !64BIT 325 help 326 All new 32-bit architectures should have 64-bit off_t type on 327 userspace side which corresponds to the loff_t kernel type. This 328 is the requirement for modern ABIs. Some existing architectures 329 still support 32-bit off_t. This option is enabled for all such 330 architectures explicitly. 331 332# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 333config ARCH_32BIT_USTAT_F_TINODE 334 bool 335 336config HAVE_ASM_MODVERSIONS 337 bool 338 help 339 This symbol should be selected by an architecture if it provides 340 <asm/asm-prototypes.h> to support the module versioning for symbols 341 exported from assembly code. 342 343config HAVE_REGS_AND_STACK_ACCESS_API 344 bool 345 help 346 This symbol should be selected by an architecture if it supports 347 the API needed to access registers and stack entries from pt_regs, 348 declared in asm/ptrace.h 349 For example the kprobes-based event tracer needs this API. 350 351config HAVE_RSEQ 352 bool 353 depends on HAVE_REGS_AND_STACK_ACCESS_API 354 help 355 This symbol should be selected by an architecture if it 356 supports an implementation of restartable sequences. 357 358config HAVE_RUST 359 bool 360 help 361 This symbol should be selected by an architecture if it 362 supports Rust. 363 364config HAVE_FUNCTION_ARG_ACCESS_API 365 bool 366 help 367 This symbol should be selected by an architecture if it supports 368 the API needed to access function arguments from pt_regs, 369 declared in asm/ptrace.h 370 371config HAVE_HW_BREAKPOINT 372 bool 373 depends on PERF_EVENTS 374 375config HAVE_MIXED_BREAKPOINTS_REGS 376 bool 377 depends on HAVE_HW_BREAKPOINT 378 help 379 Depending on the arch implementation of hardware breakpoints, 380 some of them have separate registers for data and instruction 381 breakpoints addresses, others have mixed registers to store 382 them but define the access type in a control register. 383 Select this option if your arch implements breakpoints under the 384 latter fashion. 385 386config HAVE_USER_RETURN_NOTIFIER 387 bool 388 389config HAVE_PERF_EVENTS_NMI 390 bool 391 help 392 System hardware can generate an NMI using the perf event 393 subsystem. Also has support for calculating CPU cycle events 394 to determine how many clock cycles in a given period. 395 396config HAVE_HARDLOCKUP_DETECTOR_PERF 397 bool 398 depends on HAVE_PERF_EVENTS_NMI 399 help 400 The arch chooses to use the generic perf-NMI-based hardlockup 401 detector. Must define HAVE_PERF_EVENTS_NMI. 402 403config HAVE_NMI_WATCHDOG 404 depends on HAVE_NMI 405 bool 406 help 407 The arch provides a low level NMI watchdog. It provides 408 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 409 410config HAVE_HARDLOCKUP_DETECTOR_ARCH 411 bool 412 select HAVE_NMI_WATCHDOG 413 help 414 The arch chooses to provide its own hardlockup detector, which is 415 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 416 interfaces and parameters provided by hardlockup detector subsystem. 417 418config HAVE_PERF_REGS 419 bool 420 help 421 Support selective register dumps for perf events. This includes 422 bit-mapping of each registers and a unique architecture id. 423 424config HAVE_PERF_USER_STACK_DUMP 425 bool 426 help 427 Support user stack dumps for perf event samples. This needs 428 access to the user stack pointer which is not unified across 429 architectures. 430 431config HAVE_ARCH_JUMP_LABEL 432 bool 433 434config HAVE_ARCH_JUMP_LABEL_RELATIVE 435 bool 436 437config MMU_GATHER_TABLE_FREE 438 bool 439 440config MMU_GATHER_RCU_TABLE_FREE 441 bool 442 select MMU_GATHER_TABLE_FREE 443 444config MMU_GATHER_PAGE_SIZE 445 bool 446 447config MMU_GATHER_NO_RANGE 448 bool 449 select MMU_GATHER_MERGE_VMAS 450 451config MMU_GATHER_NO_FLUSH_CACHE 452 bool 453 454config MMU_GATHER_MERGE_VMAS 455 bool 456 457config MMU_GATHER_NO_GATHER 458 bool 459 depends on MMU_GATHER_TABLE_FREE 460 461config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 462 bool 463 help 464 Temporary select until all architectures can be converted to have 465 irqs disabled over activate_mm. Architectures that do IPI based TLB 466 shootdowns should enable this. 467 468# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 469# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 470# to/from kernel threads when the same mm is running on a lot of CPUs (a large 471# multi-threaded application), by reducing contention on the mm refcount. 472# 473# This can be disabled if the architecture ensures no CPUs are using an mm as a 474# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 475# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 476# final exit(2) TLB flush, for example. 477# 478# To implement this, an arch *must*: 479# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 480# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 481# converted already). 482config MMU_LAZY_TLB_REFCOUNT 483 def_bool y 484 485config ARCH_HAVE_NMI_SAFE_CMPXCHG 486 bool 487 488config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 489 bool 490 491config HAVE_ALIGNED_STRUCT_PAGE 492 bool 493 help 494 This makes sure that struct pages are double word aligned and that 495 e.g. the SLUB allocator can perform double word atomic operations 496 on a struct page for better performance. However selecting this 497 might increase the size of a struct page by a word. 498 499config HAVE_CMPXCHG_LOCAL 500 bool 501 502config HAVE_CMPXCHG_DOUBLE 503 bool 504 505config ARCH_WEAK_RELEASE_ACQUIRE 506 bool 507 508config ARCH_WANT_IPC_PARSE_VERSION 509 bool 510 511config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 512 bool 513 514config ARCH_WANT_OLD_COMPAT_IPC 515 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 516 bool 517 518config HAVE_ARCH_SECCOMP 519 bool 520 help 521 An arch should select this symbol to support seccomp mode 1 (the fixed 522 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 523 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 524 - __NR_seccomp_read_32 525 - __NR_seccomp_write_32 526 - __NR_seccomp_exit_32 527 - __NR_seccomp_sigreturn_32 528 529config HAVE_ARCH_SECCOMP_FILTER 530 bool 531 select HAVE_ARCH_SECCOMP 532 help 533 An arch should select this symbol if it provides all of these things: 534 - all the requirements for HAVE_ARCH_SECCOMP 535 - syscall_get_arch() 536 - syscall_get_arguments() 537 - syscall_rollback() 538 - syscall_set_return_value() 539 - SIGSYS siginfo_t support 540 - secure_computing is called from a ptrace_event()-safe context 541 - secure_computing return value is checked and a return value of -1 542 results in the system call being skipped immediately. 543 - seccomp syscall wired up 544 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 545 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 546 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 547 548config SECCOMP 549 prompt "Enable seccomp to safely execute untrusted bytecode" 550 def_bool y 551 depends on HAVE_ARCH_SECCOMP 552 help 553 This kernel feature is useful for number crunching applications 554 that may need to handle untrusted bytecode during their 555 execution. By using pipes or other transports made available 556 to the process as file descriptors supporting the read/write 557 syscalls, it's possible to isolate those applications in their 558 own address space using seccomp. Once seccomp is enabled via 559 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 560 disabled and the task is only allowed to execute a few safe 561 syscalls defined by each seccomp mode. 562 563 If unsure, say Y. 564 565config SECCOMP_FILTER 566 def_bool y 567 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 568 help 569 Enable tasks to build secure computing environments defined 570 in terms of Berkeley Packet Filter programs which implement 571 task-defined system call filtering polices. 572 573 See Documentation/userspace-api/seccomp_filter.rst for details. 574 575config SECCOMP_CACHE_DEBUG 576 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 577 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 578 depends on PROC_FS 579 help 580 This enables the /proc/pid/seccomp_cache interface to monitor 581 seccomp cache data. The file format is subject to change. Reading 582 the file requires CAP_SYS_ADMIN. 583 584 This option is for debugging only. Enabling presents the risk that 585 an adversary may be able to infer the seccomp filter logic. 586 587 If unsure, say N. 588 589config HAVE_ARCH_STACKLEAK 590 bool 591 help 592 An architecture should select this if it has the code which 593 fills the used part of the kernel stack with the STACKLEAK_POISON 594 value before returning from system calls. 595 596config HAVE_STACKPROTECTOR 597 bool 598 help 599 An arch should select this symbol if: 600 - it has implemented a stack canary (e.g. __stack_chk_guard) 601 602config STACKPROTECTOR 603 bool "Stack Protector buffer overflow detection" 604 depends on HAVE_STACKPROTECTOR 605 depends on $(cc-option,-fstack-protector) 606 default y 607 help 608 This option turns on the "stack-protector" GCC feature. This 609 feature puts, at the beginning of functions, a canary value on 610 the stack just before the return address, and validates 611 the value just before actually returning. Stack based buffer 612 overflows (that need to overwrite this return address) now also 613 overwrite the canary, which gets detected and the attack is then 614 neutralized via a kernel panic. 615 616 Functions will have the stack-protector canary logic added if they 617 have an 8-byte or larger character array on the stack. 618 619 This feature requires gcc version 4.2 or above, or a distribution 620 gcc with the feature backported ("-fstack-protector"). 621 622 On an x86 "defconfig" build, this feature adds canary checks to 623 about 3% of all kernel functions, which increases kernel code size 624 by about 0.3%. 625 626config STACKPROTECTOR_STRONG 627 bool "Strong Stack Protector" 628 depends on STACKPROTECTOR 629 depends on $(cc-option,-fstack-protector-strong) 630 default y 631 help 632 Functions will have the stack-protector canary logic added in any 633 of the following conditions: 634 635 - local variable's address used as part of the right hand side of an 636 assignment or function argument 637 - local variable is an array (or union containing an array), 638 regardless of array type or length 639 - uses register local variables 640 641 This feature requires gcc version 4.9 or above, or a distribution 642 gcc with the feature backported ("-fstack-protector-strong"). 643 644 On an x86 "defconfig" build, this feature adds canary checks to 645 about 20% of all kernel functions, which increases the kernel code 646 size by about 2%. 647 648config ARCH_SUPPORTS_SHADOW_CALL_STACK 649 bool 650 help 651 An architecture should select this if it supports the compiler's 652 Shadow Call Stack and implements runtime support for shadow stack 653 switching. 654 655config SHADOW_CALL_STACK 656 bool "Shadow Call Stack" 657 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 658 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 659 help 660 This option enables the compiler's Shadow Call Stack, which 661 uses a shadow stack to protect function return addresses from 662 being overwritten by an attacker. More information can be found 663 in the compiler's documentation: 664 665 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 666 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 667 668 Note that security guarantees in the kernel differ from the 669 ones documented for user space. The kernel must store addresses 670 of shadow stacks in memory, which means an attacker capable of 671 reading and writing arbitrary memory may be able to locate them 672 and hijack control flow by modifying the stacks. 673 674config DYNAMIC_SCS 675 bool 676 help 677 Set by the arch code if it relies on code patching to insert the 678 shadow call stack push and pop instructions rather than on the 679 compiler. 680 681config LTO 682 bool 683 help 684 Selected if the kernel will be built using the compiler's LTO feature. 685 686config LTO_CLANG 687 bool 688 select LTO 689 help 690 Selected if the kernel will be built using Clang's LTO feature. 691 692config ARCH_SUPPORTS_LTO_CLANG 693 bool 694 help 695 An architecture should select this option if it supports: 696 - compiling with Clang, 697 - compiling inline assembly with Clang's integrated assembler, 698 - and linking with LLD. 699 700config ARCH_SUPPORTS_LTO_CLANG_THIN 701 bool 702 help 703 An architecture should select this option if it can support Clang's 704 ThinLTO mode. 705 706config HAS_LTO_CLANG 707 def_bool y 708 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 709 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 710 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 711 depends on ARCH_SUPPORTS_LTO_CLANG 712 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 713 depends on !KASAN || KASAN_HW_TAGS 714 depends on !GCOV_KERNEL 715 help 716 The compiler and Kconfig options support building with Clang's 717 LTO. 718 719choice 720 prompt "Link Time Optimization (LTO)" 721 default LTO_NONE 722 help 723 This option enables Link Time Optimization (LTO), which allows the 724 compiler to optimize binaries globally. 725 726 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 727 so it's disabled by default. 728 729config LTO_NONE 730 bool "None" 731 help 732 Build the kernel normally, without Link Time Optimization (LTO). 733 734config LTO_CLANG_FULL 735 bool "Clang Full LTO (EXPERIMENTAL)" 736 depends on HAS_LTO_CLANG 737 depends on !COMPILE_TEST 738 select LTO_CLANG 739 help 740 This option enables Clang's full Link Time Optimization (LTO), which 741 allows the compiler to optimize the kernel globally. If you enable 742 this option, the compiler generates LLVM bitcode instead of ELF 743 object files, and the actual compilation from bitcode happens at 744 the LTO link step, which may take several minutes depending on the 745 kernel configuration. More information can be found from LLVM's 746 documentation: 747 748 https://llvm.org/docs/LinkTimeOptimization.html 749 750 During link time, this option can use a large amount of RAM, and 751 may take much longer than the ThinLTO option. 752 753config LTO_CLANG_THIN 754 bool "Clang ThinLTO (EXPERIMENTAL)" 755 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 756 select LTO_CLANG 757 help 758 This option enables Clang's ThinLTO, which allows for parallel 759 optimization and faster incremental compiles compared to the 760 CONFIG_LTO_CLANG_FULL option. More information can be found 761 from Clang's documentation: 762 763 https://clang.llvm.org/docs/ThinLTO.html 764 765 If unsure, say Y. 766endchoice 767 768config ARCH_SUPPORTS_CFI_CLANG 769 bool 770 help 771 An architecture should select this option if it can support Clang's 772 Control-Flow Integrity (CFI) checking. 773 774config ARCH_USES_CFI_TRAPS 775 bool 776 777config CFI_CLANG 778 bool "Use Clang's Control Flow Integrity (CFI)" 779 depends on ARCH_SUPPORTS_CFI_CLANG 780 depends on $(cc-option,-fsanitize=kcfi) 781 help 782 This option enables Clang’s forward-edge Control Flow Integrity 783 (CFI) checking, where the compiler injects a runtime check to each 784 indirect function call to ensure the target is a valid function with 785 the correct static type. This restricts possible call targets and 786 makes it more difficult for an attacker to exploit bugs that allow 787 the modification of stored function pointers. More information can be 788 found from Clang's documentation: 789 790 https://clang.llvm.org/docs/ControlFlowIntegrity.html 791 792config CFI_PERMISSIVE 793 bool "Use CFI in permissive mode" 794 depends on CFI_CLANG 795 help 796 When selected, Control Flow Integrity (CFI) violations result in a 797 warning instead of a kernel panic. This option should only be used 798 for finding indirect call type mismatches during development. 799 800 If unsure, say N. 801 802config HAVE_ARCH_WITHIN_STACK_FRAMES 803 bool 804 help 805 An architecture should select this if it can walk the kernel stack 806 frames to determine if an object is part of either the arguments 807 or local variables (i.e. that it excludes saved return addresses, 808 and similar) by implementing an inline arch_within_stack_frames(), 809 which is used by CONFIG_HARDENED_USERCOPY. 810 811config HAVE_CONTEXT_TRACKING_USER 812 bool 813 help 814 Provide kernel/user boundaries probes necessary for subsystems 815 that need it, such as userspace RCU extended quiescent state. 816 Syscalls need to be wrapped inside user_exit()-user_enter(), either 817 optimized behind static key or through the slow path using TIF_NOHZ 818 flag. Exceptions handlers must be wrapped as well. Irqs are already 819 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 820 handling on irq exit still need to be protected. 821 822config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 823 bool 824 help 825 Architecture neither relies on exception_enter()/exception_exit() 826 nor on schedule_user(). Also preempt_schedule_notrace() and 827 preempt_schedule_irq() can't be called in a preemptible section 828 while context tracking is CONTEXT_USER. This feature reflects a sane 829 entry implementation where the following requirements are met on 830 critical entry code, ie: before user_exit() or after user_enter(): 831 832 - Critical entry code isn't preemptible (or better yet: 833 not interruptible). 834 - No use of RCU read side critical sections, unless ct_nmi_enter() 835 got called. 836 - No use of instrumentation, unless instrumentation_begin() got 837 called. 838 839config HAVE_TIF_NOHZ 840 bool 841 help 842 Arch relies on TIF_NOHZ and syscall slow path to implement context 843 tracking calls to user_enter()/user_exit(). 844 845config HAVE_VIRT_CPU_ACCOUNTING 846 bool 847 848config HAVE_VIRT_CPU_ACCOUNTING_IDLE 849 bool 850 help 851 Architecture has its own way to account idle CPU time and therefore 852 doesn't implement vtime_account_idle(). 853 854config ARCH_HAS_SCALED_CPUTIME 855 bool 856 857config HAVE_VIRT_CPU_ACCOUNTING_GEN 858 bool 859 default y if 64BIT 860 help 861 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 862 Before enabling this option, arch code must be audited 863 to ensure there are no races in concurrent read/write of 864 cputime_t. For example, reading/writing 64-bit cputime_t on 865 some 32-bit arches may require multiple accesses, so proper 866 locking is needed to protect against concurrent accesses. 867 868config HAVE_IRQ_TIME_ACCOUNTING 869 bool 870 help 871 Archs need to ensure they use a high enough resolution clock to 872 support irq time accounting and then call enable_sched_clock_irqtime(). 873 874config HAVE_MOVE_PUD 875 bool 876 help 877 Architectures that select this are able to move page tables at the 878 PUD level. If there are only 3 page table levels, the move effectively 879 happens at the PGD level. 880 881config HAVE_MOVE_PMD 882 bool 883 help 884 Archs that select this are able to move page tables at the PMD level. 885 886config HAVE_ARCH_TRANSPARENT_HUGEPAGE 887 bool 888 889config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 890 bool 891 892config HAVE_ARCH_HUGE_VMAP 893 bool 894 895# 896# Archs that select this would be capable of PMD-sized vmaps (i.e., 897# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 898# must be used to enable allocations to use hugepages. 899# 900config HAVE_ARCH_HUGE_VMALLOC 901 depends on HAVE_ARCH_HUGE_VMAP 902 bool 903 904config ARCH_WANT_HUGE_PMD_SHARE 905 bool 906 907config HAVE_ARCH_SOFT_DIRTY 908 bool 909 910config HAVE_MOD_ARCH_SPECIFIC 911 bool 912 help 913 The arch uses struct mod_arch_specific to store data. Many arches 914 just need a simple module loader without arch specific data - those 915 should not enable this. 916 917config MODULES_USE_ELF_RELA 918 bool 919 help 920 Modules only use ELF RELA relocations. Modules with ELF REL 921 relocations will give an error. 922 923config MODULES_USE_ELF_REL 924 bool 925 help 926 Modules only use ELF REL relocations. Modules with ELF RELA 927 relocations will give an error. 928 929config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 930 bool 931 help 932 For architectures like powerpc/32 which have constraints on module 933 allocation and need to allocate module data outside of module area. 934 935config HAVE_IRQ_EXIT_ON_IRQ_STACK 936 bool 937 help 938 Architecture doesn't only execute the irq handler on the irq stack 939 but also irq_exit(). This way we can process softirqs on this irq 940 stack instead of switching to a new one when we call __do_softirq() 941 in the end of an hardirq. 942 This spares a stack switch and improves cache usage on softirq 943 processing. 944 945config HAVE_SOFTIRQ_ON_OWN_STACK 946 bool 947 help 948 Architecture provides a function to run __do_softirq() on a 949 separate stack. 950 951config SOFTIRQ_ON_OWN_STACK 952 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 953 954config ALTERNATE_USER_ADDRESS_SPACE 955 bool 956 help 957 Architectures set this when the CPU uses separate address 958 spaces for kernel and user space pointers. In this case, the 959 access_ok() check on a __user pointer is skipped. 960 961config PGTABLE_LEVELS 962 int 963 default 2 964 965config ARCH_HAS_ELF_RANDOMIZE 966 bool 967 help 968 An architecture supports choosing randomized locations for 969 stack, mmap, brk, and ET_DYN. Defined functions: 970 - arch_mmap_rnd() 971 - arch_randomize_brk() 972 973config HAVE_ARCH_MMAP_RND_BITS 974 bool 975 help 976 An arch should select this symbol if it supports setting a variable 977 number of bits for use in establishing the base address for mmap 978 allocations, has MMU enabled and provides values for both: 979 - ARCH_MMAP_RND_BITS_MIN 980 - ARCH_MMAP_RND_BITS_MAX 981 982config HAVE_EXIT_THREAD 983 bool 984 help 985 An architecture implements exit_thread. 986 987config ARCH_MMAP_RND_BITS_MIN 988 int 989 990config ARCH_MMAP_RND_BITS_MAX 991 int 992 993config ARCH_MMAP_RND_BITS_DEFAULT 994 int 995 996config ARCH_MMAP_RND_BITS 997 int "Number of bits to use for ASLR of mmap base address" if EXPERT 998 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 999 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1000 default ARCH_MMAP_RND_BITS_MIN 1001 depends on HAVE_ARCH_MMAP_RND_BITS 1002 help 1003 This value can be used to select the number of bits to use to 1004 determine the random offset to the base address of vma regions 1005 resulting from mmap allocations. This value will be bounded 1006 by the architecture's minimum and maximum supported values. 1007 1008 This value can be changed after boot using the 1009 /proc/sys/vm/mmap_rnd_bits tunable 1010 1011config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1012 bool 1013 help 1014 An arch should select this symbol if it supports running applications 1015 in compatibility mode, supports setting a variable number of bits for 1016 use in establishing the base address for mmap allocations, has MMU 1017 enabled and provides values for both: 1018 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1019 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1020 1021config ARCH_MMAP_RND_COMPAT_BITS_MIN 1022 int 1023 1024config ARCH_MMAP_RND_COMPAT_BITS_MAX 1025 int 1026 1027config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1028 int 1029 1030config ARCH_MMAP_RND_COMPAT_BITS 1031 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1032 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1033 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1034 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1035 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1036 help 1037 This value can be used to select the number of bits to use to 1038 determine the random offset to the base address of vma regions 1039 resulting from mmap allocations for compatible applications This 1040 value will be bounded by the architecture's minimum and maximum 1041 supported values. 1042 1043 This value can be changed after boot using the 1044 /proc/sys/vm/mmap_rnd_compat_bits tunable 1045 1046config HAVE_ARCH_COMPAT_MMAP_BASES 1047 bool 1048 help 1049 This allows 64bit applications to invoke 32-bit mmap() syscall 1050 and vice-versa 32-bit applications to call 64-bit mmap(). 1051 Required for applications doing different bitness syscalls. 1052 1053config PAGE_SIZE_LESS_THAN_64KB 1054 def_bool y 1055 depends on !ARM64_64K_PAGES 1056 depends on !IA64_PAGE_SIZE_64KB 1057 depends on !PAGE_SIZE_64KB 1058 depends on !PARISC_PAGE_SIZE_64KB 1059 depends on PAGE_SIZE_LESS_THAN_256KB 1060 1061config PAGE_SIZE_LESS_THAN_256KB 1062 def_bool y 1063 depends on !PAGE_SIZE_256KB 1064 1065# This allows to use a set of generic functions to determine mmap base 1066# address by giving priority to top-down scheme only if the process 1067# is not in legacy mode (compat task, unlimited stack size or 1068# sysctl_legacy_va_layout). 1069# Architecture that selects this option can provide its own version of: 1070# - STACK_RND_MASK 1071config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1072 bool 1073 depends on MMU 1074 select ARCH_HAS_ELF_RANDOMIZE 1075 1076config HAVE_OBJTOOL 1077 bool 1078 1079config HAVE_JUMP_LABEL_HACK 1080 bool 1081 1082config HAVE_NOINSTR_HACK 1083 bool 1084 1085config HAVE_NOINSTR_VALIDATION 1086 bool 1087 1088config HAVE_UACCESS_VALIDATION 1089 bool 1090 select OBJTOOL 1091 1092config HAVE_STACK_VALIDATION 1093 bool 1094 help 1095 Architecture supports objtool compile-time frame pointer rule 1096 validation. 1097 1098config HAVE_RELIABLE_STACKTRACE 1099 bool 1100 help 1101 Architecture has either save_stack_trace_tsk_reliable() or 1102 arch_stack_walk_reliable() function which only returns a stack trace 1103 if it can guarantee the trace is reliable. 1104 1105config HAVE_ARCH_HASH 1106 bool 1107 default n 1108 help 1109 If this is set, the architecture provides an <asm/hash.h> 1110 file which provides platform-specific implementations of some 1111 functions in <linux/hash.h> or fs/namei.c. 1112 1113config HAVE_ARCH_NVRAM_OPS 1114 bool 1115 1116config ISA_BUS_API 1117 def_bool ISA 1118 1119# 1120# ABI hall of shame 1121# 1122config CLONE_BACKWARDS 1123 bool 1124 help 1125 Architecture has tls passed as the 4th argument of clone(2), 1126 not the 5th one. 1127 1128config CLONE_BACKWARDS2 1129 bool 1130 help 1131 Architecture has the first two arguments of clone(2) swapped. 1132 1133config CLONE_BACKWARDS3 1134 bool 1135 help 1136 Architecture has tls passed as the 3rd argument of clone(2), 1137 not the 5th one. 1138 1139config ODD_RT_SIGACTION 1140 bool 1141 help 1142 Architecture has unusual rt_sigaction(2) arguments 1143 1144config OLD_SIGSUSPEND 1145 bool 1146 help 1147 Architecture has old sigsuspend(2) syscall, of one-argument variety 1148 1149config OLD_SIGSUSPEND3 1150 bool 1151 help 1152 Even weirder antique ABI - three-argument sigsuspend(2) 1153 1154config OLD_SIGACTION 1155 bool 1156 help 1157 Architecture has old sigaction(2) syscall. Nope, not the same 1158 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1159 but fairly different variant of sigaction(2), thanks to OSF/1 1160 compatibility... 1161 1162config COMPAT_OLD_SIGACTION 1163 bool 1164 1165config COMPAT_32BIT_TIME 1166 bool "Provide system calls for 32-bit time_t" 1167 default !64BIT || COMPAT 1168 help 1169 This enables 32 bit time_t support in addition to 64 bit time_t support. 1170 This is relevant on all 32-bit architectures, and 64-bit architectures 1171 as part of compat syscall handling. 1172 1173config ARCH_NO_PREEMPT 1174 bool 1175 1176config ARCH_EPHEMERAL_INODES 1177 def_bool n 1178 help 1179 An arch should select this symbol if it doesn't keep track of inode 1180 instances on its own, but instead relies on something else (e.g. the 1181 host kernel for an UML kernel). 1182 1183config ARCH_SUPPORTS_RT 1184 bool 1185 1186config CPU_NO_EFFICIENT_FFS 1187 def_bool n 1188 1189config HAVE_ARCH_VMAP_STACK 1190 def_bool n 1191 help 1192 An arch should select this symbol if it can support kernel stacks 1193 in vmalloc space. This means: 1194 1195 - vmalloc space must be large enough to hold many kernel stacks. 1196 This may rule out many 32-bit architectures. 1197 1198 - Stacks in vmalloc space need to work reliably. For example, if 1199 vmap page tables are created on demand, either this mechanism 1200 needs to work while the stack points to a virtual address with 1201 unpopulated page tables or arch code (switch_to() and switch_mm(), 1202 most likely) needs to ensure that the stack's page table entries 1203 are populated before running on a possibly unpopulated stack. 1204 1205 - If the stack overflows into a guard page, something reasonable 1206 should happen. The definition of "reasonable" is flexible, but 1207 instantly rebooting without logging anything would be unfriendly. 1208 1209config VMAP_STACK 1210 default y 1211 bool "Use a virtually-mapped stack" 1212 depends on HAVE_ARCH_VMAP_STACK 1213 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1214 help 1215 Enable this if you want the use virtually-mapped kernel stacks 1216 with guard pages. This causes kernel stack overflows to be 1217 caught immediately rather than causing difficult-to-diagnose 1218 corruption. 1219 1220 To use this with software KASAN modes, the architecture must support 1221 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1222 must be enabled. 1223 1224config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1225 def_bool n 1226 help 1227 An arch should select this symbol if it can support kernel stack 1228 offset randomization with calls to add_random_kstack_offset() 1229 during syscall entry and choose_random_kstack_offset() during 1230 syscall exit. Careful removal of -fstack-protector-strong and 1231 -fstack-protector should also be applied to the entry code and 1232 closely examined, as the artificial stack bump looks like an array 1233 to the compiler, so it will attempt to add canary checks regardless 1234 of the static branch state. 1235 1236config RANDOMIZE_KSTACK_OFFSET 1237 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1238 default y 1239 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1240 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1241 help 1242 The kernel stack offset can be randomized (after pt_regs) by 1243 roughly 5 bits of entropy, frustrating memory corruption 1244 attacks that depend on stack address determinism or 1245 cross-syscall address exposures. 1246 1247 The feature is controlled via the "randomize_kstack_offset=on/off" 1248 kernel boot param, and if turned off has zero overhead due to its use 1249 of static branches (see JUMP_LABEL). 1250 1251 If unsure, say Y. 1252 1253config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1254 bool "Default state of kernel stack offset randomization" 1255 depends on RANDOMIZE_KSTACK_OFFSET 1256 help 1257 Kernel stack offset randomization is controlled by kernel boot param 1258 "randomize_kstack_offset=on/off", and this config chooses the default 1259 boot state. 1260 1261config ARCH_OPTIONAL_KERNEL_RWX 1262 def_bool n 1263 1264config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1265 def_bool n 1266 1267config ARCH_HAS_STRICT_KERNEL_RWX 1268 def_bool n 1269 1270config STRICT_KERNEL_RWX 1271 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1272 depends on ARCH_HAS_STRICT_KERNEL_RWX 1273 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1274 help 1275 If this is set, kernel text and rodata memory will be made read-only, 1276 and non-text memory will be made non-executable. This provides 1277 protection against certain security exploits (e.g. executing the heap 1278 or modifying text) 1279 1280 These features are considered standard security practice these days. 1281 You should say Y here in almost all cases. 1282 1283config ARCH_HAS_STRICT_MODULE_RWX 1284 def_bool n 1285 1286config STRICT_MODULE_RWX 1287 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1288 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1289 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1290 help 1291 If this is set, module text and rodata memory will be made read-only, 1292 and non-text memory will be made non-executable. This provides 1293 protection against certain security exploits (e.g. writing to text) 1294 1295# select if the architecture provides an asm/dma-direct.h header 1296config ARCH_HAS_PHYS_TO_DMA 1297 bool 1298 1299config HAVE_ARCH_COMPILER_H 1300 bool 1301 help 1302 An architecture can select this if it provides an 1303 asm/compiler.h header that should be included after 1304 linux/compiler-*.h in order to override macro definitions that those 1305 headers generally provide. 1306 1307config HAVE_ARCH_PREL32_RELOCATIONS 1308 bool 1309 help 1310 May be selected by an architecture if it supports place-relative 1311 32-bit relocations, both in the toolchain and in the module loader, 1312 in which case relative references can be used in special sections 1313 for PCI fixup, initcalls etc which are only half the size on 64 bit 1314 architectures, and don't require runtime relocation on relocatable 1315 kernels. 1316 1317config ARCH_USE_MEMREMAP_PROT 1318 bool 1319 1320config LOCK_EVENT_COUNTS 1321 bool "Locking event counts collection" 1322 depends on DEBUG_FS 1323 help 1324 Enable light-weight counting of various locking related events 1325 in the system with minimal performance impact. This reduces 1326 the chance of application behavior change because of timing 1327 differences. The counts are reported via debugfs. 1328 1329# Select if the architecture has support for applying RELR relocations. 1330config ARCH_HAS_RELR 1331 bool 1332 1333config RELR 1334 bool "Use RELR relocation packing" 1335 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1336 default y 1337 help 1338 Store the kernel's dynamic relocations in the RELR relocation packing 1339 format. Requires a compatible linker (LLD supports this feature), as 1340 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1341 are compatible). 1342 1343config ARCH_HAS_MEM_ENCRYPT 1344 bool 1345 1346config ARCH_HAS_CC_PLATFORM 1347 bool 1348 1349config HAVE_SPARSE_SYSCALL_NR 1350 bool 1351 help 1352 An architecture should select this if its syscall numbering is sparse 1353 to save space. For example, MIPS architecture has a syscall array with 1354 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1355 related optimizations for a given architecture. 1356 1357config ARCH_HAS_VDSO_DATA 1358 bool 1359 1360config HAVE_STATIC_CALL 1361 bool 1362 1363config HAVE_STATIC_CALL_INLINE 1364 bool 1365 depends on HAVE_STATIC_CALL 1366 select OBJTOOL 1367 1368config HAVE_PREEMPT_DYNAMIC 1369 bool 1370 1371config HAVE_PREEMPT_DYNAMIC_CALL 1372 bool 1373 depends on HAVE_STATIC_CALL 1374 select HAVE_PREEMPT_DYNAMIC 1375 help 1376 An architecture should select this if it can handle the preemption 1377 model being selected at boot time using static calls. 1378 1379 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1380 preemption function will be patched directly. 1381 1382 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1383 call to a preemption function will go through a trampoline, and the 1384 trampoline will be patched. 1385 1386 It is strongly advised to support inline static call to avoid any 1387 overhead. 1388 1389config HAVE_PREEMPT_DYNAMIC_KEY 1390 bool 1391 depends on HAVE_ARCH_JUMP_LABEL 1392 select HAVE_PREEMPT_DYNAMIC 1393 help 1394 An architecture should select this if it can handle the preemption 1395 model being selected at boot time using static keys. 1396 1397 Each preemption function will be given an early return based on a 1398 static key. This should have slightly lower overhead than non-inline 1399 static calls, as this effectively inlines each trampoline into the 1400 start of its callee. This may avoid redundant work, and may 1401 integrate better with CFI schemes. 1402 1403 This will have greater overhead than using inline static calls as 1404 the call to the preemption function cannot be entirely elided. 1405 1406config ARCH_WANT_LD_ORPHAN_WARN 1407 bool 1408 help 1409 An arch should select this symbol once all linker sections are explicitly 1410 included, size-asserted, or discarded in the linker scripts. This is 1411 important because we never want expected sections to be placed heuristically 1412 by the linker, since the locations of such sections can change between linker 1413 versions. 1414 1415config HAVE_ARCH_PFN_VALID 1416 bool 1417 1418config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1419 bool 1420 1421config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1422 bool 1423 1424config ARCH_SPLIT_ARG64 1425 bool 1426 help 1427 If a 32-bit architecture requires 64-bit arguments to be split into 1428 pairs of 32-bit arguments, select this option. 1429 1430config ARCH_HAS_ELFCORE_COMPAT 1431 bool 1432 1433config ARCH_HAS_PARANOID_L1D_FLUSH 1434 bool 1435 1436config ARCH_HAVE_TRACE_MMIO_ACCESS 1437 bool 1438 1439config DYNAMIC_SIGFRAME 1440 bool 1441 1442# Select, if arch has a named attribute group bound to NUMA device nodes. 1443config HAVE_ARCH_NODE_DEV_GROUP 1444 bool 1445 1446config ARCH_HAS_NONLEAF_PMD_YOUNG 1447 bool 1448 help 1449 Architectures that select this option are capable of setting the 1450 accessed bit in non-leaf PMD entries when using them as part of linear 1451 address translations. Page table walkers that clear the accessed bit 1452 may use this capability to reduce their search space. 1453 1454source "kernel/gcov/Kconfig" 1455 1456source "scripts/gcc-plugins/Kconfig" 1457 1458config FUNCTION_ALIGNMENT_4B 1459 bool 1460 1461config FUNCTION_ALIGNMENT_8B 1462 bool 1463 1464config FUNCTION_ALIGNMENT_16B 1465 bool 1466 1467config FUNCTION_ALIGNMENT_32B 1468 bool 1469 1470config FUNCTION_ALIGNMENT_64B 1471 bool 1472 1473config FUNCTION_ALIGNMENT 1474 int 1475 default 64 if FUNCTION_ALIGNMENT_64B 1476 default 32 if FUNCTION_ALIGNMENT_32B 1477 default 16 if FUNCTION_ALIGNMENT_16B 1478 default 8 if FUNCTION_ALIGNMENT_8B 1479 default 4 if FUNCTION_ALIGNMENT_4B 1480 default 0 1481 1482endmenu 1483