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 SMT_NUM_THREADS_DYNAMIC 38 bool 39 40# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 41config HOTPLUG_CORE_SYNC 42 bool 43 44# Basic CPU dead synchronization selected by architecture 45config HOTPLUG_CORE_SYNC_DEAD 46 bool 47 select HOTPLUG_CORE_SYNC 48 49# Full CPU synchronization with alive state selected by architecture 50config HOTPLUG_CORE_SYNC_FULL 51 bool 52 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 53 select HOTPLUG_CORE_SYNC 54 55config HOTPLUG_SPLIT_STARTUP 56 bool 57 select HOTPLUG_CORE_SYNC_FULL 58 59config HOTPLUG_PARALLEL 60 bool 61 select HOTPLUG_SPLIT_STARTUP 62 63config GENERIC_ENTRY 64 bool 65 66config KPROBES 67 bool "Kprobes" 68 depends on MODULES 69 depends on HAVE_KPROBES 70 select KALLSYMS 71 select TASKS_RCU if PREEMPTION 72 help 73 Kprobes allows you to trap at almost any kernel address and 74 execute a callback function. register_kprobe() establishes 75 a probepoint and specifies the callback. Kprobes is useful 76 for kernel debugging, non-intrusive instrumentation and testing. 77 If in doubt, say "N". 78 79config JUMP_LABEL 80 bool "Optimize very unlikely/likely branches" 81 depends on HAVE_ARCH_JUMP_LABEL 82 select OBJTOOL if HAVE_JUMP_LABEL_HACK 83 help 84 This option enables a transparent branch optimization that 85 makes certain almost-always-true or almost-always-false branch 86 conditions even cheaper to execute within the kernel. 87 88 Certain performance-sensitive kernel code, such as trace points, 89 scheduler functionality, networking code and KVM have such 90 branches and include support for this optimization technique. 91 92 If it is detected that the compiler has support for "asm goto", 93 the kernel will compile such branches with just a nop 94 instruction. When the condition flag is toggled to true, the 95 nop will be converted to a jump instruction to execute the 96 conditional block of instructions. 97 98 This technique lowers overhead and stress on the branch prediction 99 of the processor and generally makes the kernel faster. The update 100 of the condition is slower, but those are always very rare. 101 102 ( On 32-bit x86, the necessary options added to the compiler 103 flags may increase the size of the kernel slightly. ) 104 105config STATIC_KEYS_SELFTEST 106 bool "Static key selftest" 107 depends on JUMP_LABEL 108 help 109 Boot time self-test of the branch patching code. 110 111config STATIC_CALL_SELFTEST 112 bool "Static call selftest" 113 depends on HAVE_STATIC_CALL 114 help 115 Boot time self-test of the call patching code. 116 117config OPTPROBES 118 def_bool y 119 depends on KPROBES && HAVE_OPTPROBES 120 select TASKS_RCU if PREEMPTION 121 122config KPROBES_ON_FTRACE 123 def_bool y 124 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 125 depends on DYNAMIC_FTRACE_WITH_REGS 126 help 127 If function tracer is enabled and the arch supports full 128 passing of pt_regs to function tracing, then kprobes can 129 optimize on top of function tracing. 130 131config UPROBES 132 def_bool n 133 depends on ARCH_SUPPORTS_UPROBES 134 help 135 Uprobes is the user-space counterpart to kprobes: they 136 enable instrumentation applications (such as 'perf probe') 137 to establish unintrusive probes in user-space binaries and 138 libraries, by executing handler functions when the probes 139 are hit by user-space applications. 140 141 ( These probes come in the form of single-byte breakpoints, 142 managed by the kernel and kept transparent to the probed 143 application. ) 144 145config HAVE_64BIT_ALIGNED_ACCESS 146 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 147 help 148 Some architectures require 64 bit accesses to be 64 bit 149 aligned, which also requires structs containing 64 bit values 150 to be 64 bit aligned too. This includes some 32 bit 151 architectures which can do 64 bit accesses, as well as 64 bit 152 architectures without unaligned access. 153 154 This symbol should be selected by an architecture if 64 bit 155 accesses are required to be 64 bit aligned in this way even 156 though it is not a 64 bit architecture. 157 158 See Documentation/core-api/unaligned-memory-access.rst for 159 more information on the topic of unaligned memory accesses. 160 161config HAVE_EFFICIENT_UNALIGNED_ACCESS 162 bool 163 help 164 Some architectures are unable to perform unaligned accesses 165 without the use of get_unaligned/put_unaligned. Others are 166 unable to perform such accesses efficiently (e.g. trap on 167 unaligned access and require fixing it up in the exception 168 handler.) 169 170 This symbol should be selected by an architecture if it can 171 perform unaligned accesses efficiently to allow different 172 code paths to be selected for these cases. Some network 173 drivers, for example, could opt to not fix up alignment 174 problems with received packets if doing so would not help 175 much. 176 177 See Documentation/core-api/unaligned-memory-access.rst for more 178 information on the topic of unaligned memory accesses. 179 180config ARCH_USE_BUILTIN_BSWAP 181 bool 182 help 183 Modern versions of GCC (since 4.4) have builtin functions 184 for handling byte-swapping. Using these, instead of the old 185 inline assembler that the architecture code provides in the 186 __arch_bswapXX() macros, allows the compiler to see what's 187 happening and offers more opportunity for optimisation. In 188 particular, the compiler will be able to combine the byteswap 189 with a nearby load or store and use load-and-swap or 190 store-and-swap instructions if the architecture has them. It 191 should almost *never* result in code which is worse than the 192 hand-coded assembler in <asm/swab.h>. But just in case it 193 does, the use of the builtins is optional. 194 195 Any architecture with load-and-swap or store-and-swap 196 instructions should set this. And it shouldn't hurt to set it 197 on architectures that don't have such instructions. 198 199config KRETPROBES 200 def_bool y 201 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 202 203config KRETPROBE_ON_RETHOOK 204 def_bool y 205 depends on HAVE_RETHOOK 206 depends on KRETPROBES 207 select RETHOOK 208 209config USER_RETURN_NOTIFIER 210 bool 211 depends on HAVE_USER_RETURN_NOTIFIER 212 help 213 Provide a kernel-internal notification when a cpu is about to 214 switch to user mode. 215 216config HAVE_IOREMAP_PROT 217 bool 218 219config HAVE_KPROBES 220 bool 221 222config HAVE_KRETPROBES 223 bool 224 225config HAVE_OPTPROBES 226 bool 227 228config HAVE_KPROBES_ON_FTRACE 229 bool 230 231config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 232 bool 233 help 234 Since kretprobes modifies return address on the stack, the 235 stacktrace may see the kretprobe trampoline address instead 236 of correct one. If the architecture stacktrace code and 237 unwinder can adjust such entries, select this configuration. 238 239config HAVE_FUNCTION_ERROR_INJECTION 240 bool 241 242config HAVE_NMI 243 bool 244 245config HAVE_FUNCTION_DESCRIPTORS 246 bool 247 248config TRACE_IRQFLAGS_SUPPORT 249 bool 250 251config TRACE_IRQFLAGS_NMI_SUPPORT 252 bool 253 254# 255# An arch should select this if it provides all these things: 256# 257# task_pt_regs() in asm/processor.h or asm/ptrace.h 258# arch_has_single_step() if there is hardware single-step support 259# arch_has_block_step() if there is hardware block-step support 260# asm/syscall.h supplying asm-generic/syscall.h interface 261# linux/regset.h user_regset interfaces 262# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 263# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 264# TIF_NOTIFY_RESUME calls resume_user_mode_work() 265# 266config HAVE_ARCH_TRACEHOOK 267 bool 268 269config HAVE_DMA_CONTIGUOUS 270 bool 271 272config GENERIC_SMP_IDLE_THREAD 273 bool 274 275config GENERIC_IDLE_POLL_SETUP 276 bool 277 278config ARCH_HAS_FORTIFY_SOURCE 279 bool 280 help 281 An architecture should select this when it can successfully 282 build and run with CONFIG_FORTIFY_SOURCE. 283 284# 285# Select if the arch provides a historic keepinit alias for the retain_initrd 286# command line option 287# 288config ARCH_HAS_KEEPINITRD 289 bool 290 291# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 292config ARCH_HAS_SET_MEMORY 293 bool 294 295# Select if arch has all set_direct_map_invalid/default() functions 296config ARCH_HAS_SET_DIRECT_MAP 297 bool 298 299# 300# Select if the architecture provides the arch_dma_set_uncached symbol to 301# either provide an uncached segment alias for a DMA allocation, or 302# to remap the page tables in place. 303# 304config ARCH_HAS_DMA_SET_UNCACHED 305 bool 306 307# 308# Select if the architectures provides the arch_dma_clear_uncached symbol 309# to undo an in-place page table remap for uncached access. 310# 311config ARCH_HAS_DMA_CLEAR_UNCACHED 312 bool 313 314config ARCH_HAS_CPU_FINALIZE_INIT 315 bool 316 317# Select if arch init_task must go in the __init_task_data section 318config ARCH_TASK_STRUCT_ON_STACK 319 bool 320 321# Select if arch has its private alloc_task_struct() function 322config ARCH_TASK_STRUCT_ALLOCATOR 323 bool 324 325config HAVE_ARCH_THREAD_STRUCT_WHITELIST 326 bool 327 depends on !ARCH_TASK_STRUCT_ALLOCATOR 328 help 329 An architecture should select this to provide hardened usercopy 330 knowledge about what region of the thread_struct should be 331 whitelisted for copying to userspace. Normally this is only the 332 FPU registers. Specifically, arch_thread_struct_whitelist() 333 should be implemented. Without this, the entire thread_struct 334 field in task_struct will be left whitelisted. 335 336# Select if arch has its private alloc_thread_stack() function 337config ARCH_THREAD_STACK_ALLOCATOR 338 bool 339 340# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 341config ARCH_WANTS_DYNAMIC_TASK_STRUCT 342 bool 343 344config ARCH_WANTS_NO_INSTR 345 bool 346 help 347 An architecture should select this if the noinstr macro is being used on 348 functions to denote that the toolchain should avoid instrumenting such 349 functions and is required for correctness. 350 351config ARCH_32BIT_OFF_T 352 bool 353 depends on !64BIT 354 help 355 All new 32-bit architectures should have 64-bit off_t type on 356 userspace side which corresponds to the loff_t kernel type. This 357 is the requirement for modern ABIs. Some existing architectures 358 still support 32-bit off_t. This option is enabled for all such 359 architectures explicitly. 360 361# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 362config ARCH_32BIT_USTAT_F_TINODE 363 bool 364 365config HAVE_ASM_MODVERSIONS 366 bool 367 help 368 This symbol should be selected by an architecture if it provides 369 <asm/asm-prototypes.h> to support the module versioning for symbols 370 exported from assembly code. 371 372config HAVE_REGS_AND_STACK_ACCESS_API 373 bool 374 help 375 This symbol should be selected by an architecture if it supports 376 the API needed to access registers and stack entries from pt_regs, 377 declared in asm/ptrace.h 378 For example the kprobes-based event tracer needs this API. 379 380config HAVE_RSEQ 381 bool 382 depends on HAVE_REGS_AND_STACK_ACCESS_API 383 help 384 This symbol should be selected by an architecture if it 385 supports an implementation of restartable sequences. 386 387config HAVE_RUST 388 bool 389 help 390 This symbol should be selected by an architecture if it 391 supports Rust. 392 393config HAVE_FUNCTION_ARG_ACCESS_API 394 bool 395 help 396 This symbol should be selected by an architecture if it supports 397 the API needed to access function arguments from pt_regs, 398 declared in asm/ptrace.h 399 400config HAVE_HW_BREAKPOINT 401 bool 402 depends on PERF_EVENTS 403 404config HAVE_MIXED_BREAKPOINTS_REGS 405 bool 406 depends on HAVE_HW_BREAKPOINT 407 help 408 Depending on the arch implementation of hardware breakpoints, 409 some of them have separate registers for data and instruction 410 breakpoints addresses, others have mixed registers to store 411 them but define the access type in a control register. 412 Select this option if your arch implements breakpoints under the 413 latter fashion. 414 415config HAVE_USER_RETURN_NOTIFIER 416 bool 417 418config HAVE_PERF_EVENTS_NMI 419 bool 420 help 421 System hardware can generate an NMI using the perf event 422 subsystem. Also has support for calculating CPU cycle events 423 to determine how many clock cycles in a given period. 424 425config HAVE_HARDLOCKUP_DETECTOR_PERF 426 bool 427 depends on HAVE_PERF_EVENTS_NMI 428 help 429 The arch chooses to use the generic perf-NMI-based hardlockup 430 detector. Must define HAVE_PERF_EVENTS_NMI. 431 432config HAVE_HARDLOCKUP_DETECTOR_ARCH 433 bool 434 help 435 The arch provides its own hardlockup detector implementation instead 436 of the generic ones. 437 438 It uses the same command line parameters, and sysctl interface, 439 as the generic hardlockup detectors. 440 441config HAVE_PERF_REGS 442 bool 443 help 444 Support selective register dumps for perf events. This includes 445 bit-mapping of each registers and a unique architecture id. 446 447config HAVE_PERF_USER_STACK_DUMP 448 bool 449 help 450 Support user stack dumps for perf event samples. This needs 451 access to the user stack pointer which is not unified across 452 architectures. 453 454config HAVE_ARCH_JUMP_LABEL 455 bool 456 457config HAVE_ARCH_JUMP_LABEL_RELATIVE 458 bool 459 460config MMU_GATHER_TABLE_FREE 461 bool 462 463config MMU_GATHER_RCU_TABLE_FREE 464 bool 465 select MMU_GATHER_TABLE_FREE 466 467config MMU_GATHER_PAGE_SIZE 468 bool 469 470config MMU_GATHER_NO_RANGE 471 bool 472 select MMU_GATHER_MERGE_VMAS 473 474config MMU_GATHER_NO_FLUSH_CACHE 475 bool 476 477config MMU_GATHER_MERGE_VMAS 478 bool 479 480config MMU_GATHER_NO_GATHER 481 bool 482 depends on MMU_GATHER_TABLE_FREE 483 484config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 485 bool 486 help 487 Temporary select until all architectures can be converted to have 488 irqs disabled over activate_mm. Architectures that do IPI based TLB 489 shootdowns should enable this. 490 491# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 492# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 493# to/from kernel threads when the same mm is running on a lot of CPUs (a large 494# multi-threaded application), by reducing contention on the mm refcount. 495# 496# This can be disabled if the architecture ensures no CPUs are using an mm as a 497# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 498# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 499# final exit(2) TLB flush, for example. 500# 501# To implement this, an arch *must*: 502# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 503# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 504# converted already). 505config MMU_LAZY_TLB_REFCOUNT 506 def_bool y 507 depends on !MMU_LAZY_TLB_SHOOTDOWN 508 509# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 510# mm as a lazy tlb beyond its last reference count, by shooting down these 511# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 512# be using the mm as a lazy tlb, so that they may switch themselves to using 513# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 514# may be using mm as a lazy tlb mm. 515# 516# To implement this, an arch *must*: 517# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 518# at least all possible CPUs in which the mm is lazy. 519# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 520config MMU_LAZY_TLB_SHOOTDOWN 521 bool 522 523config ARCH_HAVE_NMI_SAFE_CMPXCHG 524 bool 525 526config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 527 bool 528 529config HAVE_ALIGNED_STRUCT_PAGE 530 bool 531 help 532 This makes sure that struct pages are double word aligned and that 533 e.g. the SLUB allocator can perform double word atomic operations 534 on a struct page for better performance. However selecting this 535 might increase the size of a struct page by a word. 536 537config HAVE_CMPXCHG_LOCAL 538 bool 539 540config HAVE_CMPXCHG_DOUBLE 541 bool 542 543config ARCH_WEAK_RELEASE_ACQUIRE 544 bool 545 546config ARCH_WANT_IPC_PARSE_VERSION 547 bool 548 549config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 550 bool 551 552config ARCH_WANT_OLD_COMPAT_IPC 553 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 554 bool 555 556config HAVE_ARCH_SECCOMP 557 bool 558 help 559 An arch should select this symbol to support seccomp mode 1 (the fixed 560 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 561 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 562 - __NR_seccomp_read_32 563 - __NR_seccomp_write_32 564 - __NR_seccomp_exit_32 565 - __NR_seccomp_sigreturn_32 566 567config HAVE_ARCH_SECCOMP_FILTER 568 bool 569 select HAVE_ARCH_SECCOMP 570 help 571 An arch should select this symbol if it provides all of these things: 572 - all the requirements for HAVE_ARCH_SECCOMP 573 - syscall_get_arch() 574 - syscall_get_arguments() 575 - syscall_rollback() 576 - syscall_set_return_value() 577 - SIGSYS siginfo_t support 578 - secure_computing is called from a ptrace_event()-safe context 579 - secure_computing return value is checked and a return value of -1 580 results in the system call being skipped immediately. 581 - seccomp syscall wired up 582 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 583 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 584 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 585 586config SECCOMP 587 prompt "Enable seccomp to safely execute untrusted bytecode" 588 def_bool y 589 depends on HAVE_ARCH_SECCOMP 590 help 591 This kernel feature is useful for number crunching applications 592 that may need to handle untrusted bytecode during their 593 execution. By using pipes or other transports made available 594 to the process as file descriptors supporting the read/write 595 syscalls, it's possible to isolate those applications in their 596 own address space using seccomp. Once seccomp is enabled via 597 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 598 disabled and the task is only allowed to execute a few safe 599 syscalls defined by each seccomp mode. 600 601 If unsure, say Y. 602 603config SECCOMP_FILTER 604 def_bool y 605 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 606 help 607 Enable tasks to build secure computing environments defined 608 in terms of Berkeley Packet Filter programs which implement 609 task-defined system call filtering polices. 610 611 See Documentation/userspace-api/seccomp_filter.rst for details. 612 613config SECCOMP_CACHE_DEBUG 614 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 615 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 616 depends on PROC_FS 617 help 618 This enables the /proc/pid/seccomp_cache interface to monitor 619 seccomp cache data. The file format is subject to change. Reading 620 the file requires CAP_SYS_ADMIN. 621 622 This option is for debugging only. Enabling presents the risk that 623 an adversary may be able to infer the seccomp filter logic. 624 625 If unsure, say N. 626 627config HAVE_ARCH_STACKLEAK 628 bool 629 help 630 An architecture should select this if it has the code which 631 fills the used part of the kernel stack with the STACKLEAK_POISON 632 value before returning from system calls. 633 634config HAVE_STACKPROTECTOR 635 bool 636 help 637 An arch should select this symbol if: 638 - it has implemented a stack canary (e.g. __stack_chk_guard) 639 640config STACKPROTECTOR 641 bool "Stack Protector buffer overflow detection" 642 depends on HAVE_STACKPROTECTOR 643 depends on $(cc-option,-fstack-protector) 644 default y 645 help 646 This option turns on the "stack-protector" GCC feature. This 647 feature puts, at the beginning of functions, a canary value on 648 the stack just before the return address, and validates 649 the value just before actually returning. Stack based buffer 650 overflows (that need to overwrite this return address) now also 651 overwrite the canary, which gets detected and the attack is then 652 neutralized via a kernel panic. 653 654 Functions will have the stack-protector canary logic added if they 655 have an 8-byte or larger character array on the stack. 656 657 This feature requires gcc version 4.2 or above, or a distribution 658 gcc with the feature backported ("-fstack-protector"). 659 660 On an x86 "defconfig" build, this feature adds canary checks to 661 about 3% of all kernel functions, which increases kernel code size 662 by about 0.3%. 663 664config STACKPROTECTOR_STRONG 665 bool "Strong Stack Protector" 666 depends on STACKPROTECTOR 667 depends on $(cc-option,-fstack-protector-strong) 668 default y 669 help 670 Functions will have the stack-protector canary logic added in any 671 of the following conditions: 672 673 - local variable's address used as part of the right hand side of an 674 assignment or function argument 675 - local variable is an array (or union containing an array), 676 regardless of array type or length 677 - uses register local variables 678 679 This feature requires gcc version 4.9 or above, or a distribution 680 gcc with the feature backported ("-fstack-protector-strong"). 681 682 On an x86 "defconfig" build, this feature adds canary checks to 683 about 20% of all kernel functions, which increases the kernel code 684 size by about 2%. 685 686config ARCH_SUPPORTS_SHADOW_CALL_STACK 687 bool 688 help 689 An architecture should select this if it supports the compiler's 690 Shadow Call Stack and implements runtime support for shadow stack 691 switching. 692 693config SHADOW_CALL_STACK 694 bool "Shadow Call Stack" 695 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 696 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 697 help 698 This option enables the compiler's Shadow Call Stack, which 699 uses a shadow stack to protect function return addresses from 700 being overwritten by an attacker. More information can be found 701 in the compiler's documentation: 702 703 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 704 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 705 706 Note that security guarantees in the kernel differ from the 707 ones documented for user space. The kernel must store addresses 708 of shadow stacks in memory, which means an attacker capable of 709 reading and writing arbitrary memory may be able to locate them 710 and hijack control flow by modifying the stacks. 711 712config DYNAMIC_SCS 713 bool 714 help 715 Set by the arch code if it relies on code patching to insert the 716 shadow call stack push and pop instructions rather than on the 717 compiler. 718 719config LTO 720 bool 721 help 722 Selected if the kernel will be built using the compiler's LTO feature. 723 724config LTO_CLANG 725 bool 726 select LTO 727 help 728 Selected if the kernel will be built using Clang's LTO feature. 729 730config ARCH_SUPPORTS_LTO_CLANG 731 bool 732 help 733 An architecture should select this option if it supports: 734 - compiling with Clang, 735 - compiling inline assembly with Clang's integrated assembler, 736 - and linking with LLD. 737 738config ARCH_SUPPORTS_LTO_CLANG_THIN 739 bool 740 help 741 An architecture should select this option if it can support Clang's 742 ThinLTO mode. 743 744config HAS_LTO_CLANG 745 def_bool y 746 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 747 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 748 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 749 depends on ARCH_SUPPORTS_LTO_CLANG 750 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 751 depends on !KASAN || KASAN_HW_TAGS 752 depends on !GCOV_KERNEL 753 help 754 The compiler and Kconfig options support building with Clang's 755 LTO. 756 757choice 758 prompt "Link Time Optimization (LTO)" 759 default LTO_NONE 760 help 761 This option enables Link Time Optimization (LTO), which allows the 762 compiler to optimize binaries globally. 763 764 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 765 so it's disabled by default. 766 767config LTO_NONE 768 bool "None" 769 help 770 Build the kernel normally, without Link Time Optimization (LTO). 771 772config LTO_CLANG_FULL 773 bool "Clang Full LTO (EXPERIMENTAL)" 774 depends on HAS_LTO_CLANG 775 depends on !COMPILE_TEST 776 select LTO_CLANG 777 help 778 This option enables Clang's full Link Time Optimization (LTO), which 779 allows the compiler to optimize the kernel globally. If you enable 780 this option, the compiler generates LLVM bitcode instead of ELF 781 object files, and the actual compilation from bitcode happens at 782 the LTO link step, which may take several minutes depending on the 783 kernel configuration. More information can be found from LLVM's 784 documentation: 785 786 https://llvm.org/docs/LinkTimeOptimization.html 787 788 During link time, this option can use a large amount of RAM, and 789 may take much longer than the ThinLTO option. 790 791config LTO_CLANG_THIN 792 bool "Clang ThinLTO (EXPERIMENTAL)" 793 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 794 select LTO_CLANG 795 help 796 This option enables Clang's ThinLTO, which allows for parallel 797 optimization and faster incremental compiles compared to the 798 CONFIG_LTO_CLANG_FULL option. More information can be found 799 from Clang's documentation: 800 801 https://clang.llvm.org/docs/ThinLTO.html 802 803 If unsure, say Y. 804endchoice 805 806config ARCH_SUPPORTS_CFI_CLANG 807 bool 808 help 809 An architecture should select this option if it can support Clang's 810 Control-Flow Integrity (CFI) checking. 811 812config ARCH_USES_CFI_TRAPS 813 bool 814 815config CFI_CLANG 816 bool "Use Clang's Control Flow Integrity (CFI)" 817 depends on ARCH_SUPPORTS_CFI_CLANG 818 depends on $(cc-option,-fsanitize=kcfi) 819 help 820 This option enables Clang’s forward-edge Control Flow Integrity 821 (CFI) checking, where the compiler injects a runtime check to each 822 indirect function call to ensure the target is a valid function with 823 the correct static type. This restricts possible call targets and 824 makes it more difficult for an attacker to exploit bugs that allow 825 the modification of stored function pointers. More information can be 826 found from Clang's documentation: 827 828 https://clang.llvm.org/docs/ControlFlowIntegrity.html 829 830config CFI_PERMISSIVE 831 bool "Use CFI in permissive mode" 832 depends on CFI_CLANG 833 help 834 When selected, Control Flow Integrity (CFI) violations result in a 835 warning instead of a kernel panic. This option should only be used 836 for finding indirect call type mismatches during development. 837 838 If unsure, say N. 839 840config HAVE_ARCH_WITHIN_STACK_FRAMES 841 bool 842 help 843 An architecture should select this if it can walk the kernel stack 844 frames to determine if an object is part of either the arguments 845 or local variables (i.e. that it excludes saved return addresses, 846 and similar) by implementing an inline arch_within_stack_frames(), 847 which is used by CONFIG_HARDENED_USERCOPY. 848 849config HAVE_CONTEXT_TRACKING_USER 850 bool 851 help 852 Provide kernel/user boundaries probes necessary for subsystems 853 that need it, such as userspace RCU extended quiescent state. 854 Syscalls need to be wrapped inside user_exit()-user_enter(), either 855 optimized behind static key or through the slow path using TIF_NOHZ 856 flag. Exceptions handlers must be wrapped as well. Irqs are already 857 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 858 handling on irq exit still need to be protected. 859 860config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 861 bool 862 help 863 Architecture neither relies on exception_enter()/exception_exit() 864 nor on schedule_user(). Also preempt_schedule_notrace() and 865 preempt_schedule_irq() can't be called in a preemptible section 866 while context tracking is CONTEXT_USER. This feature reflects a sane 867 entry implementation where the following requirements are met on 868 critical entry code, ie: before user_exit() or after user_enter(): 869 870 - Critical entry code isn't preemptible (or better yet: 871 not interruptible). 872 - No use of RCU read side critical sections, unless ct_nmi_enter() 873 got called. 874 - No use of instrumentation, unless instrumentation_begin() got 875 called. 876 877config HAVE_TIF_NOHZ 878 bool 879 help 880 Arch relies on TIF_NOHZ and syscall slow path to implement context 881 tracking calls to user_enter()/user_exit(). 882 883config HAVE_VIRT_CPU_ACCOUNTING 884 bool 885 886config HAVE_VIRT_CPU_ACCOUNTING_IDLE 887 bool 888 help 889 Architecture has its own way to account idle CPU time and therefore 890 doesn't implement vtime_account_idle(). 891 892config ARCH_HAS_SCALED_CPUTIME 893 bool 894 895config HAVE_VIRT_CPU_ACCOUNTING_GEN 896 bool 897 default y if 64BIT 898 help 899 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 900 Before enabling this option, arch code must be audited 901 to ensure there are no races in concurrent read/write of 902 cputime_t. For example, reading/writing 64-bit cputime_t on 903 some 32-bit arches may require multiple accesses, so proper 904 locking is needed to protect against concurrent accesses. 905 906config HAVE_IRQ_TIME_ACCOUNTING 907 bool 908 help 909 Archs need to ensure they use a high enough resolution clock to 910 support irq time accounting and then call enable_sched_clock_irqtime(). 911 912config HAVE_MOVE_PUD 913 bool 914 help 915 Architectures that select this are able to move page tables at the 916 PUD level. If there are only 3 page table levels, the move effectively 917 happens at the PGD level. 918 919config HAVE_MOVE_PMD 920 bool 921 help 922 Archs that select this are able to move page tables at the PMD level. 923 924config HAVE_ARCH_TRANSPARENT_HUGEPAGE 925 bool 926 927config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 928 bool 929 930config HAVE_ARCH_HUGE_VMAP 931 bool 932 933# 934# Archs that select this would be capable of PMD-sized vmaps (i.e., 935# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 936# must be used to enable allocations to use hugepages. 937# 938config HAVE_ARCH_HUGE_VMALLOC 939 depends on HAVE_ARCH_HUGE_VMAP 940 bool 941 942config ARCH_WANT_HUGE_PMD_SHARE 943 bool 944 945config HAVE_ARCH_SOFT_DIRTY 946 bool 947 948config HAVE_MOD_ARCH_SPECIFIC 949 bool 950 help 951 The arch uses struct mod_arch_specific to store data. Many arches 952 just need a simple module loader without arch specific data - those 953 should not enable this. 954 955config MODULES_USE_ELF_RELA 956 bool 957 help 958 Modules only use ELF RELA relocations. Modules with ELF REL 959 relocations will give an error. 960 961config MODULES_USE_ELF_REL 962 bool 963 help 964 Modules only use ELF REL relocations. Modules with ELF RELA 965 relocations will give an error. 966 967config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 968 bool 969 help 970 For architectures like powerpc/32 which have constraints on module 971 allocation and need to allocate module data outside of module area. 972 973config HAVE_IRQ_EXIT_ON_IRQ_STACK 974 bool 975 help 976 Architecture doesn't only execute the irq handler on the irq stack 977 but also irq_exit(). This way we can process softirqs on this irq 978 stack instead of switching to a new one when we call __do_softirq() 979 in the end of an hardirq. 980 This spares a stack switch and improves cache usage on softirq 981 processing. 982 983config HAVE_SOFTIRQ_ON_OWN_STACK 984 bool 985 help 986 Architecture provides a function to run __do_softirq() on a 987 separate stack. 988 989config SOFTIRQ_ON_OWN_STACK 990 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 991 992config ALTERNATE_USER_ADDRESS_SPACE 993 bool 994 help 995 Architectures set this when the CPU uses separate address 996 spaces for kernel and user space pointers. In this case, the 997 access_ok() check on a __user pointer is skipped. 998 999config PGTABLE_LEVELS 1000 int 1001 default 2 1002 1003config ARCH_HAS_ELF_RANDOMIZE 1004 bool 1005 help 1006 An architecture supports choosing randomized locations for 1007 stack, mmap, brk, and ET_DYN. Defined functions: 1008 - arch_mmap_rnd() 1009 - arch_randomize_brk() 1010 1011config HAVE_ARCH_MMAP_RND_BITS 1012 bool 1013 help 1014 An arch should select this symbol if it supports setting a variable 1015 number of bits for use in establishing the base address for mmap 1016 allocations, has MMU enabled and provides values for both: 1017 - ARCH_MMAP_RND_BITS_MIN 1018 - ARCH_MMAP_RND_BITS_MAX 1019 1020config HAVE_EXIT_THREAD 1021 bool 1022 help 1023 An architecture implements exit_thread. 1024 1025config ARCH_MMAP_RND_BITS_MIN 1026 int 1027 1028config ARCH_MMAP_RND_BITS_MAX 1029 int 1030 1031config ARCH_MMAP_RND_BITS_DEFAULT 1032 int 1033 1034config ARCH_MMAP_RND_BITS 1035 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1036 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1037 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1038 default ARCH_MMAP_RND_BITS_MIN 1039 depends on HAVE_ARCH_MMAP_RND_BITS 1040 help 1041 This value can be used to select the number of bits to use to 1042 determine the random offset to the base address of vma regions 1043 resulting from mmap allocations. This value will be bounded 1044 by the architecture's minimum and maximum supported values. 1045 1046 This value can be changed after boot using the 1047 /proc/sys/vm/mmap_rnd_bits tunable 1048 1049config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1050 bool 1051 help 1052 An arch should select this symbol if it supports running applications 1053 in compatibility mode, supports setting a variable number of bits for 1054 use in establishing the base address for mmap allocations, has MMU 1055 enabled and provides values for both: 1056 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1057 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1058 1059config ARCH_MMAP_RND_COMPAT_BITS_MIN 1060 int 1061 1062config ARCH_MMAP_RND_COMPAT_BITS_MAX 1063 int 1064 1065config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1066 int 1067 1068config ARCH_MMAP_RND_COMPAT_BITS 1069 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1070 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1071 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1072 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1073 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1074 help 1075 This value can be used to select the number of bits to use to 1076 determine the random offset to the base address of vma regions 1077 resulting from mmap allocations for compatible applications This 1078 value will be bounded by the architecture's minimum and maximum 1079 supported values. 1080 1081 This value can be changed after boot using the 1082 /proc/sys/vm/mmap_rnd_compat_bits tunable 1083 1084config HAVE_ARCH_COMPAT_MMAP_BASES 1085 bool 1086 help 1087 This allows 64bit applications to invoke 32-bit mmap() syscall 1088 and vice-versa 32-bit applications to call 64-bit mmap(). 1089 Required for applications doing different bitness syscalls. 1090 1091config PAGE_SIZE_LESS_THAN_64KB 1092 def_bool y 1093 depends on !ARM64_64K_PAGES 1094 depends on !IA64_PAGE_SIZE_64KB 1095 depends on !PAGE_SIZE_64KB 1096 depends on !PARISC_PAGE_SIZE_64KB 1097 depends on PAGE_SIZE_LESS_THAN_256KB 1098 1099config PAGE_SIZE_LESS_THAN_256KB 1100 def_bool y 1101 depends on !PAGE_SIZE_256KB 1102 1103# This allows to use a set of generic functions to determine mmap base 1104# address by giving priority to top-down scheme only if the process 1105# is not in legacy mode (compat task, unlimited stack size or 1106# sysctl_legacy_va_layout). 1107# Architecture that selects this option can provide its own version of: 1108# - STACK_RND_MASK 1109config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1110 bool 1111 depends on MMU 1112 select ARCH_HAS_ELF_RANDOMIZE 1113 1114config HAVE_OBJTOOL 1115 bool 1116 1117config HAVE_JUMP_LABEL_HACK 1118 bool 1119 1120config HAVE_NOINSTR_HACK 1121 bool 1122 1123config HAVE_NOINSTR_VALIDATION 1124 bool 1125 1126config HAVE_UACCESS_VALIDATION 1127 bool 1128 select OBJTOOL 1129 1130config HAVE_STACK_VALIDATION 1131 bool 1132 help 1133 Architecture supports objtool compile-time frame pointer rule 1134 validation. 1135 1136config HAVE_RELIABLE_STACKTRACE 1137 bool 1138 help 1139 Architecture has either save_stack_trace_tsk_reliable() or 1140 arch_stack_walk_reliable() function which only returns a stack trace 1141 if it can guarantee the trace is reliable. 1142 1143config HAVE_ARCH_HASH 1144 bool 1145 default n 1146 help 1147 If this is set, the architecture provides an <asm/hash.h> 1148 file which provides platform-specific implementations of some 1149 functions in <linux/hash.h> or fs/namei.c. 1150 1151config HAVE_ARCH_NVRAM_OPS 1152 bool 1153 1154config ISA_BUS_API 1155 def_bool ISA 1156 1157# 1158# ABI hall of shame 1159# 1160config CLONE_BACKWARDS 1161 bool 1162 help 1163 Architecture has tls passed as the 4th argument of clone(2), 1164 not the 5th one. 1165 1166config CLONE_BACKWARDS2 1167 bool 1168 help 1169 Architecture has the first two arguments of clone(2) swapped. 1170 1171config CLONE_BACKWARDS3 1172 bool 1173 help 1174 Architecture has tls passed as the 3rd argument of clone(2), 1175 not the 5th one. 1176 1177config ODD_RT_SIGACTION 1178 bool 1179 help 1180 Architecture has unusual rt_sigaction(2) arguments 1181 1182config OLD_SIGSUSPEND 1183 bool 1184 help 1185 Architecture has old sigsuspend(2) syscall, of one-argument variety 1186 1187config OLD_SIGSUSPEND3 1188 bool 1189 help 1190 Even weirder antique ABI - three-argument sigsuspend(2) 1191 1192config OLD_SIGACTION 1193 bool 1194 help 1195 Architecture has old sigaction(2) syscall. Nope, not the same 1196 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1197 but fairly different variant of sigaction(2), thanks to OSF/1 1198 compatibility... 1199 1200config COMPAT_OLD_SIGACTION 1201 bool 1202 1203config COMPAT_32BIT_TIME 1204 bool "Provide system calls for 32-bit time_t" 1205 default !64BIT || COMPAT 1206 help 1207 This enables 32 bit time_t support in addition to 64 bit time_t support. 1208 This is relevant on all 32-bit architectures, and 64-bit architectures 1209 as part of compat syscall handling. 1210 1211config ARCH_NO_PREEMPT 1212 bool 1213 1214config ARCH_SUPPORTS_RT 1215 bool 1216 1217config CPU_NO_EFFICIENT_FFS 1218 def_bool n 1219 1220config HAVE_ARCH_VMAP_STACK 1221 def_bool n 1222 help 1223 An arch should select this symbol if it can support kernel stacks 1224 in vmalloc space. This means: 1225 1226 - vmalloc space must be large enough to hold many kernel stacks. 1227 This may rule out many 32-bit architectures. 1228 1229 - Stacks in vmalloc space need to work reliably. For example, if 1230 vmap page tables are created on demand, either this mechanism 1231 needs to work while the stack points to a virtual address with 1232 unpopulated page tables or arch code (switch_to() and switch_mm(), 1233 most likely) needs to ensure that the stack's page table entries 1234 are populated before running on a possibly unpopulated stack. 1235 1236 - If the stack overflows into a guard page, something reasonable 1237 should happen. The definition of "reasonable" is flexible, but 1238 instantly rebooting without logging anything would be unfriendly. 1239 1240config VMAP_STACK 1241 default y 1242 bool "Use a virtually-mapped stack" 1243 depends on HAVE_ARCH_VMAP_STACK 1244 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1245 help 1246 Enable this if you want the use virtually-mapped kernel stacks 1247 with guard pages. This causes kernel stack overflows to be 1248 caught immediately rather than causing difficult-to-diagnose 1249 corruption. 1250 1251 To use this with software KASAN modes, the architecture must support 1252 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1253 must be enabled. 1254 1255config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1256 def_bool n 1257 help 1258 An arch should select this symbol if it can support kernel stack 1259 offset randomization with calls to add_random_kstack_offset() 1260 during syscall entry and choose_random_kstack_offset() during 1261 syscall exit. Careful removal of -fstack-protector-strong and 1262 -fstack-protector should also be applied to the entry code and 1263 closely examined, as the artificial stack bump looks like an array 1264 to the compiler, so it will attempt to add canary checks regardless 1265 of the static branch state. 1266 1267config RANDOMIZE_KSTACK_OFFSET 1268 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1269 default y 1270 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1271 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1272 help 1273 The kernel stack offset can be randomized (after pt_regs) by 1274 roughly 5 bits of entropy, frustrating memory corruption 1275 attacks that depend on stack address determinism or 1276 cross-syscall address exposures. 1277 1278 The feature is controlled via the "randomize_kstack_offset=on/off" 1279 kernel boot param, and if turned off has zero overhead due to its use 1280 of static branches (see JUMP_LABEL). 1281 1282 If unsure, say Y. 1283 1284config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1285 bool "Default state of kernel stack offset randomization" 1286 depends on RANDOMIZE_KSTACK_OFFSET 1287 help 1288 Kernel stack offset randomization is controlled by kernel boot param 1289 "randomize_kstack_offset=on/off", and this config chooses the default 1290 boot state. 1291 1292config ARCH_OPTIONAL_KERNEL_RWX 1293 def_bool n 1294 1295config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1296 def_bool n 1297 1298config ARCH_HAS_STRICT_KERNEL_RWX 1299 def_bool n 1300 1301config STRICT_KERNEL_RWX 1302 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1303 depends on ARCH_HAS_STRICT_KERNEL_RWX 1304 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1305 help 1306 If this is set, kernel text and rodata memory will be made read-only, 1307 and non-text memory will be made non-executable. This provides 1308 protection against certain security exploits (e.g. executing the heap 1309 or modifying text) 1310 1311 These features are considered standard security practice these days. 1312 You should say Y here in almost all cases. 1313 1314config ARCH_HAS_STRICT_MODULE_RWX 1315 def_bool n 1316 1317config STRICT_MODULE_RWX 1318 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1319 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1320 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1321 help 1322 If this is set, module text and rodata memory will be made read-only, 1323 and non-text memory will be made non-executable. This provides 1324 protection against certain security exploits (e.g. writing to text) 1325 1326# select if the architecture provides an asm/dma-direct.h header 1327config ARCH_HAS_PHYS_TO_DMA 1328 bool 1329 1330config HAVE_ARCH_COMPILER_H 1331 bool 1332 help 1333 An architecture can select this if it provides an 1334 asm/compiler.h header that should be included after 1335 linux/compiler-*.h in order to override macro definitions that those 1336 headers generally provide. 1337 1338config HAVE_ARCH_PREL32_RELOCATIONS 1339 bool 1340 help 1341 May be selected by an architecture if it supports place-relative 1342 32-bit relocations, both in the toolchain and in the module loader, 1343 in which case relative references can be used in special sections 1344 for PCI fixup, initcalls etc which are only half the size on 64 bit 1345 architectures, and don't require runtime relocation on relocatable 1346 kernels. 1347 1348config ARCH_USE_MEMREMAP_PROT 1349 bool 1350 1351config LOCK_EVENT_COUNTS 1352 bool "Locking event counts collection" 1353 depends on DEBUG_FS 1354 help 1355 Enable light-weight counting of various locking related events 1356 in the system with minimal performance impact. This reduces 1357 the chance of application behavior change because of timing 1358 differences. The counts are reported via debugfs. 1359 1360# Select if the architecture has support for applying RELR relocations. 1361config ARCH_HAS_RELR 1362 bool 1363 1364config RELR 1365 bool "Use RELR relocation packing" 1366 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1367 default y 1368 help 1369 Store the kernel's dynamic relocations in the RELR relocation packing 1370 format. Requires a compatible linker (LLD supports this feature), as 1371 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1372 are compatible). 1373 1374config ARCH_HAS_MEM_ENCRYPT 1375 bool 1376 1377config ARCH_HAS_CC_PLATFORM 1378 bool 1379 1380config HAVE_SPARSE_SYSCALL_NR 1381 bool 1382 help 1383 An architecture should select this if its syscall numbering is sparse 1384 to save space. For example, MIPS architecture has a syscall array with 1385 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1386 related optimizations for a given architecture. 1387 1388config ARCH_HAS_VDSO_DATA 1389 bool 1390 1391config HAVE_STATIC_CALL 1392 bool 1393 1394config HAVE_STATIC_CALL_INLINE 1395 bool 1396 depends on HAVE_STATIC_CALL 1397 select OBJTOOL 1398 1399config HAVE_PREEMPT_DYNAMIC 1400 bool 1401 1402config HAVE_PREEMPT_DYNAMIC_CALL 1403 bool 1404 depends on HAVE_STATIC_CALL 1405 select HAVE_PREEMPT_DYNAMIC 1406 help 1407 An architecture should select this if it can handle the preemption 1408 model being selected at boot time using static calls. 1409 1410 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1411 preemption function will be patched directly. 1412 1413 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1414 call to a preemption function will go through a trampoline, and the 1415 trampoline will be patched. 1416 1417 It is strongly advised to support inline static call to avoid any 1418 overhead. 1419 1420config HAVE_PREEMPT_DYNAMIC_KEY 1421 bool 1422 depends on HAVE_ARCH_JUMP_LABEL 1423 select HAVE_PREEMPT_DYNAMIC 1424 help 1425 An architecture should select this if it can handle the preemption 1426 model being selected at boot time using static keys. 1427 1428 Each preemption function will be given an early return based on a 1429 static key. This should have slightly lower overhead than non-inline 1430 static calls, as this effectively inlines each trampoline into the 1431 start of its callee. This may avoid redundant work, and may 1432 integrate better with CFI schemes. 1433 1434 This will have greater overhead than using inline static calls as 1435 the call to the preemption function cannot be entirely elided. 1436 1437config ARCH_WANT_LD_ORPHAN_WARN 1438 bool 1439 help 1440 An arch should select this symbol once all linker sections are explicitly 1441 included, size-asserted, or discarded in the linker scripts. This is 1442 important because we never want expected sections to be placed heuristically 1443 by the linker, since the locations of such sections can change between linker 1444 versions. 1445 1446config HAVE_ARCH_PFN_VALID 1447 bool 1448 1449config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1450 bool 1451 1452config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1453 bool 1454 1455config ARCH_SPLIT_ARG64 1456 bool 1457 help 1458 If a 32-bit architecture requires 64-bit arguments to be split into 1459 pairs of 32-bit arguments, select this option. 1460 1461config ARCH_HAS_ELFCORE_COMPAT 1462 bool 1463 1464config ARCH_HAS_PARANOID_L1D_FLUSH 1465 bool 1466 1467config ARCH_HAVE_TRACE_MMIO_ACCESS 1468 bool 1469 1470config DYNAMIC_SIGFRAME 1471 bool 1472 1473# Select, if arch has a named attribute group bound to NUMA device nodes. 1474config HAVE_ARCH_NODE_DEV_GROUP 1475 bool 1476 1477config ARCH_HAS_NONLEAF_PMD_YOUNG 1478 bool 1479 help 1480 Architectures that select this option are capable of setting the 1481 accessed bit in non-leaf PMD entries when using them as part of linear 1482 address translations. Page table walkers that clear the accessed bit 1483 may use this capability to reduce their search space. 1484 1485source "kernel/gcov/Kconfig" 1486 1487source "scripts/gcc-plugins/Kconfig" 1488 1489config FUNCTION_ALIGNMENT_4B 1490 bool 1491 1492config FUNCTION_ALIGNMENT_8B 1493 bool 1494 1495config FUNCTION_ALIGNMENT_16B 1496 bool 1497 1498config FUNCTION_ALIGNMENT_32B 1499 bool 1500 1501config FUNCTION_ALIGNMENT_64B 1502 bool 1503 1504config FUNCTION_ALIGNMENT 1505 int 1506 default 64 if FUNCTION_ALIGNMENT_64B 1507 default 32 if FUNCTION_ALIGNMENT_32B 1508 default 16 if FUNCTION_ALIGNMENT_16B 1509 default 8 if FUNCTION_ALIGNMENT_8B 1510 default 4 if FUNCTION_ALIGNMENT_4B 1511 default 0 1512 1513endmenu 1514