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 its own hardlockup detector implementation instead 408 of the generic ones. 409 410 Sparc64 defines this variable without HAVE_HARDLOCKUP_DETECTOR_ARCH. 411 It is the last arch-specific implementation which was developed before 412 adding the common infrastructure for handling hardlockup detectors. 413 It is always built. It does _not_ use the common command line 414 parameters and sysctl interface, except for 415 /proc/sys/kernel/nmi_watchdog. 416 417config HAVE_HARDLOCKUP_DETECTOR_ARCH 418 bool 419 select HAVE_NMI_WATCHDOG 420 help 421 The arch provides its own hardlockup detector implementation instead 422 of the generic ones. 423 424 It uses the same command line parameters, and sysctl interface, 425 as the generic hardlockup detectors. 426 427 HAVE_NMI_WATCHDOG is selected to build the code shared with 428 the sparc64 specific implementation. 429 430config HAVE_PERF_REGS 431 bool 432 help 433 Support selective register dumps for perf events. This includes 434 bit-mapping of each registers and a unique architecture id. 435 436config HAVE_PERF_USER_STACK_DUMP 437 bool 438 help 439 Support user stack dumps for perf event samples. This needs 440 access to the user stack pointer which is not unified across 441 architectures. 442 443config HAVE_ARCH_JUMP_LABEL 444 bool 445 446config HAVE_ARCH_JUMP_LABEL_RELATIVE 447 bool 448 449config MMU_GATHER_TABLE_FREE 450 bool 451 452config MMU_GATHER_RCU_TABLE_FREE 453 bool 454 select MMU_GATHER_TABLE_FREE 455 456config MMU_GATHER_PAGE_SIZE 457 bool 458 459config MMU_GATHER_NO_RANGE 460 bool 461 select MMU_GATHER_MERGE_VMAS 462 463config MMU_GATHER_NO_FLUSH_CACHE 464 bool 465 466config MMU_GATHER_MERGE_VMAS 467 bool 468 469config MMU_GATHER_NO_GATHER 470 bool 471 depends on MMU_GATHER_TABLE_FREE 472 473config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 474 bool 475 help 476 Temporary select until all architectures can be converted to have 477 irqs disabled over activate_mm. Architectures that do IPI based TLB 478 shootdowns should enable this. 479 480# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 481# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 482# to/from kernel threads when the same mm is running on a lot of CPUs (a large 483# multi-threaded application), by reducing contention on the mm refcount. 484# 485# This can be disabled if the architecture ensures no CPUs are using an mm as a 486# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 487# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 488# final exit(2) TLB flush, for example. 489# 490# To implement this, an arch *must*: 491# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 492# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 493# converted already). 494config MMU_LAZY_TLB_REFCOUNT 495 def_bool y 496 depends on !MMU_LAZY_TLB_SHOOTDOWN 497 498# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 499# mm as a lazy tlb beyond its last reference count, by shooting down these 500# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 501# be using the mm as a lazy tlb, so that they may switch themselves to using 502# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 503# may be using mm as a lazy tlb mm. 504# 505# To implement this, an arch *must*: 506# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 507# at least all possible CPUs in which the mm is lazy. 508# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 509config MMU_LAZY_TLB_SHOOTDOWN 510 bool 511 512config ARCH_HAVE_NMI_SAFE_CMPXCHG 513 bool 514 515config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 516 bool 517 518config HAVE_ALIGNED_STRUCT_PAGE 519 bool 520 help 521 This makes sure that struct pages are double word aligned and that 522 e.g. the SLUB allocator can perform double word atomic operations 523 on a struct page for better performance. However selecting this 524 might increase the size of a struct page by a word. 525 526config HAVE_CMPXCHG_LOCAL 527 bool 528 529config HAVE_CMPXCHG_DOUBLE 530 bool 531 532config ARCH_WEAK_RELEASE_ACQUIRE 533 bool 534 535config ARCH_WANT_IPC_PARSE_VERSION 536 bool 537 538config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 539 bool 540 541config ARCH_WANT_OLD_COMPAT_IPC 542 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 543 bool 544 545config HAVE_ARCH_SECCOMP 546 bool 547 help 548 An arch should select this symbol to support seccomp mode 1 (the fixed 549 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 550 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 551 - __NR_seccomp_read_32 552 - __NR_seccomp_write_32 553 - __NR_seccomp_exit_32 554 - __NR_seccomp_sigreturn_32 555 556config HAVE_ARCH_SECCOMP_FILTER 557 bool 558 select HAVE_ARCH_SECCOMP 559 help 560 An arch should select this symbol if it provides all of these things: 561 - all the requirements for HAVE_ARCH_SECCOMP 562 - syscall_get_arch() 563 - syscall_get_arguments() 564 - syscall_rollback() 565 - syscall_set_return_value() 566 - SIGSYS siginfo_t support 567 - secure_computing is called from a ptrace_event()-safe context 568 - secure_computing return value is checked and a return value of -1 569 results in the system call being skipped immediately. 570 - seccomp syscall wired up 571 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 572 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 573 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 574 575config SECCOMP 576 prompt "Enable seccomp to safely execute untrusted bytecode" 577 def_bool y 578 depends on HAVE_ARCH_SECCOMP 579 help 580 This kernel feature is useful for number crunching applications 581 that may need to handle untrusted bytecode during their 582 execution. By using pipes or other transports made available 583 to the process as file descriptors supporting the read/write 584 syscalls, it's possible to isolate those applications in their 585 own address space using seccomp. Once seccomp is enabled via 586 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 587 disabled and the task is only allowed to execute a few safe 588 syscalls defined by each seccomp mode. 589 590 If unsure, say Y. 591 592config SECCOMP_FILTER 593 def_bool y 594 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 595 help 596 Enable tasks to build secure computing environments defined 597 in terms of Berkeley Packet Filter programs which implement 598 task-defined system call filtering polices. 599 600 See Documentation/userspace-api/seccomp_filter.rst for details. 601 602config SECCOMP_CACHE_DEBUG 603 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 604 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 605 depends on PROC_FS 606 help 607 This enables the /proc/pid/seccomp_cache interface to monitor 608 seccomp cache data. The file format is subject to change. Reading 609 the file requires CAP_SYS_ADMIN. 610 611 This option is for debugging only. Enabling presents the risk that 612 an adversary may be able to infer the seccomp filter logic. 613 614 If unsure, say N. 615 616config HAVE_ARCH_STACKLEAK 617 bool 618 help 619 An architecture should select this if it has the code which 620 fills the used part of the kernel stack with the STACKLEAK_POISON 621 value before returning from system calls. 622 623config HAVE_STACKPROTECTOR 624 bool 625 help 626 An arch should select this symbol if: 627 - it has implemented a stack canary (e.g. __stack_chk_guard) 628 629config STACKPROTECTOR 630 bool "Stack Protector buffer overflow detection" 631 depends on HAVE_STACKPROTECTOR 632 depends on $(cc-option,-fstack-protector) 633 default y 634 help 635 This option turns on the "stack-protector" GCC feature. This 636 feature puts, at the beginning of functions, a canary value on 637 the stack just before the return address, and validates 638 the value just before actually returning. Stack based buffer 639 overflows (that need to overwrite this return address) now also 640 overwrite the canary, which gets detected and the attack is then 641 neutralized via a kernel panic. 642 643 Functions will have the stack-protector canary logic added if they 644 have an 8-byte or larger character array on the stack. 645 646 This feature requires gcc version 4.2 or above, or a distribution 647 gcc with the feature backported ("-fstack-protector"). 648 649 On an x86 "defconfig" build, this feature adds canary checks to 650 about 3% of all kernel functions, which increases kernel code size 651 by about 0.3%. 652 653config STACKPROTECTOR_STRONG 654 bool "Strong Stack Protector" 655 depends on STACKPROTECTOR 656 depends on $(cc-option,-fstack-protector-strong) 657 default y 658 help 659 Functions will have the stack-protector canary logic added in any 660 of the following conditions: 661 662 - local variable's address used as part of the right hand side of an 663 assignment or function argument 664 - local variable is an array (or union containing an array), 665 regardless of array type or length 666 - uses register local variables 667 668 This feature requires gcc version 4.9 or above, or a distribution 669 gcc with the feature backported ("-fstack-protector-strong"). 670 671 On an x86 "defconfig" build, this feature adds canary checks to 672 about 20% of all kernel functions, which increases the kernel code 673 size by about 2%. 674 675config ARCH_SUPPORTS_SHADOW_CALL_STACK 676 bool 677 help 678 An architecture should select this if it supports the compiler's 679 Shadow Call Stack and implements runtime support for shadow stack 680 switching. 681 682config SHADOW_CALL_STACK 683 bool "Shadow Call Stack" 684 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 685 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 686 help 687 This option enables the compiler's Shadow Call Stack, which 688 uses a shadow stack to protect function return addresses from 689 being overwritten by an attacker. More information can be found 690 in the compiler's documentation: 691 692 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 693 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 694 695 Note that security guarantees in the kernel differ from the 696 ones documented for user space. The kernel must store addresses 697 of shadow stacks in memory, which means an attacker capable of 698 reading and writing arbitrary memory may be able to locate them 699 and hijack control flow by modifying the stacks. 700 701config DYNAMIC_SCS 702 bool 703 help 704 Set by the arch code if it relies on code patching to insert the 705 shadow call stack push and pop instructions rather than on the 706 compiler. 707 708config LTO 709 bool 710 help 711 Selected if the kernel will be built using the compiler's LTO feature. 712 713config LTO_CLANG 714 bool 715 select LTO 716 help 717 Selected if the kernel will be built using Clang's LTO feature. 718 719config ARCH_SUPPORTS_LTO_CLANG 720 bool 721 help 722 An architecture should select this option if it supports: 723 - compiling with Clang, 724 - compiling inline assembly with Clang's integrated assembler, 725 - and linking with LLD. 726 727config ARCH_SUPPORTS_LTO_CLANG_THIN 728 bool 729 help 730 An architecture should select this option if it can support Clang's 731 ThinLTO mode. 732 733config HAS_LTO_CLANG 734 def_bool y 735 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 736 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 737 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 738 depends on ARCH_SUPPORTS_LTO_CLANG 739 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 740 depends on !KASAN || KASAN_HW_TAGS 741 depends on !GCOV_KERNEL 742 help 743 The compiler and Kconfig options support building with Clang's 744 LTO. 745 746choice 747 prompt "Link Time Optimization (LTO)" 748 default LTO_NONE 749 help 750 This option enables Link Time Optimization (LTO), which allows the 751 compiler to optimize binaries globally. 752 753 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 754 so it's disabled by default. 755 756config LTO_NONE 757 bool "None" 758 help 759 Build the kernel normally, without Link Time Optimization (LTO). 760 761config LTO_CLANG_FULL 762 bool "Clang Full LTO (EXPERIMENTAL)" 763 depends on HAS_LTO_CLANG 764 depends on !COMPILE_TEST 765 select LTO_CLANG 766 help 767 This option enables Clang's full Link Time Optimization (LTO), which 768 allows the compiler to optimize the kernel globally. If you enable 769 this option, the compiler generates LLVM bitcode instead of ELF 770 object files, and the actual compilation from bitcode happens at 771 the LTO link step, which may take several minutes depending on the 772 kernel configuration. More information can be found from LLVM's 773 documentation: 774 775 https://llvm.org/docs/LinkTimeOptimization.html 776 777 During link time, this option can use a large amount of RAM, and 778 may take much longer than the ThinLTO option. 779 780config LTO_CLANG_THIN 781 bool "Clang ThinLTO (EXPERIMENTAL)" 782 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 783 select LTO_CLANG 784 help 785 This option enables Clang's ThinLTO, which allows for parallel 786 optimization and faster incremental compiles compared to the 787 CONFIG_LTO_CLANG_FULL option. More information can be found 788 from Clang's documentation: 789 790 https://clang.llvm.org/docs/ThinLTO.html 791 792 If unsure, say Y. 793endchoice 794 795config ARCH_SUPPORTS_CFI_CLANG 796 bool 797 help 798 An architecture should select this option if it can support Clang's 799 Control-Flow Integrity (CFI) checking. 800 801config ARCH_USES_CFI_TRAPS 802 bool 803 804config CFI_CLANG 805 bool "Use Clang's Control Flow Integrity (CFI)" 806 depends on ARCH_SUPPORTS_CFI_CLANG 807 depends on $(cc-option,-fsanitize=kcfi) 808 help 809 This option enables Clang’s forward-edge Control Flow Integrity 810 (CFI) checking, where the compiler injects a runtime check to each 811 indirect function call to ensure the target is a valid function with 812 the correct static type. This restricts possible call targets and 813 makes it more difficult for an attacker to exploit bugs that allow 814 the modification of stored function pointers. More information can be 815 found from Clang's documentation: 816 817 https://clang.llvm.org/docs/ControlFlowIntegrity.html 818 819config CFI_PERMISSIVE 820 bool "Use CFI in permissive mode" 821 depends on CFI_CLANG 822 help 823 When selected, Control Flow Integrity (CFI) violations result in a 824 warning instead of a kernel panic. This option should only be used 825 for finding indirect call type mismatches during development. 826 827 If unsure, say N. 828 829config HAVE_ARCH_WITHIN_STACK_FRAMES 830 bool 831 help 832 An architecture should select this if it can walk the kernel stack 833 frames to determine if an object is part of either the arguments 834 or local variables (i.e. that it excludes saved return addresses, 835 and similar) by implementing an inline arch_within_stack_frames(), 836 which is used by CONFIG_HARDENED_USERCOPY. 837 838config HAVE_CONTEXT_TRACKING_USER 839 bool 840 help 841 Provide kernel/user boundaries probes necessary for subsystems 842 that need it, such as userspace RCU extended quiescent state. 843 Syscalls need to be wrapped inside user_exit()-user_enter(), either 844 optimized behind static key or through the slow path using TIF_NOHZ 845 flag. Exceptions handlers must be wrapped as well. Irqs are already 846 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 847 handling on irq exit still need to be protected. 848 849config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 850 bool 851 help 852 Architecture neither relies on exception_enter()/exception_exit() 853 nor on schedule_user(). Also preempt_schedule_notrace() and 854 preempt_schedule_irq() can't be called in a preemptible section 855 while context tracking is CONTEXT_USER. This feature reflects a sane 856 entry implementation where the following requirements are met on 857 critical entry code, ie: before user_exit() or after user_enter(): 858 859 - Critical entry code isn't preemptible (or better yet: 860 not interruptible). 861 - No use of RCU read side critical sections, unless ct_nmi_enter() 862 got called. 863 - No use of instrumentation, unless instrumentation_begin() got 864 called. 865 866config HAVE_TIF_NOHZ 867 bool 868 help 869 Arch relies on TIF_NOHZ and syscall slow path to implement context 870 tracking calls to user_enter()/user_exit(). 871 872config HAVE_VIRT_CPU_ACCOUNTING 873 bool 874 875config HAVE_VIRT_CPU_ACCOUNTING_IDLE 876 bool 877 help 878 Architecture has its own way to account idle CPU time and therefore 879 doesn't implement vtime_account_idle(). 880 881config ARCH_HAS_SCALED_CPUTIME 882 bool 883 884config HAVE_VIRT_CPU_ACCOUNTING_GEN 885 bool 886 default y if 64BIT 887 help 888 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 889 Before enabling this option, arch code must be audited 890 to ensure there are no races in concurrent read/write of 891 cputime_t. For example, reading/writing 64-bit cputime_t on 892 some 32-bit arches may require multiple accesses, so proper 893 locking is needed to protect against concurrent accesses. 894 895config HAVE_IRQ_TIME_ACCOUNTING 896 bool 897 help 898 Archs need to ensure they use a high enough resolution clock to 899 support irq time accounting and then call enable_sched_clock_irqtime(). 900 901config HAVE_MOVE_PUD 902 bool 903 help 904 Architectures that select this are able to move page tables at the 905 PUD level. If there are only 3 page table levels, the move effectively 906 happens at the PGD level. 907 908config HAVE_MOVE_PMD 909 bool 910 help 911 Archs that select this are able to move page tables at the PMD level. 912 913config HAVE_ARCH_TRANSPARENT_HUGEPAGE 914 bool 915 916config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 917 bool 918 919config HAVE_ARCH_HUGE_VMAP 920 bool 921 922# 923# Archs that select this would be capable of PMD-sized vmaps (i.e., 924# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 925# must be used to enable allocations to use hugepages. 926# 927config HAVE_ARCH_HUGE_VMALLOC 928 depends on HAVE_ARCH_HUGE_VMAP 929 bool 930 931config ARCH_WANT_HUGE_PMD_SHARE 932 bool 933 934config HAVE_ARCH_SOFT_DIRTY 935 bool 936 937config HAVE_MOD_ARCH_SPECIFIC 938 bool 939 help 940 The arch uses struct mod_arch_specific to store data. Many arches 941 just need a simple module loader without arch specific data - those 942 should not enable this. 943 944config MODULES_USE_ELF_RELA 945 bool 946 help 947 Modules only use ELF RELA relocations. Modules with ELF REL 948 relocations will give an error. 949 950config MODULES_USE_ELF_REL 951 bool 952 help 953 Modules only use ELF REL relocations. Modules with ELF RELA 954 relocations will give an error. 955 956config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 957 bool 958 help 959 For architectures like powerpc/32 which have constraints on module 960 allocation and need to allocate module data outside of module area. 961 962config HAVE_IRQ_EXIT_ON_IRQ_STACK 963 bool 964 help 965 Architecture doesn't only execute the irq handler on the irq stack 966 but also irq_exit(). This way we can process softirqs on this irq 967 stack instead of switching to a new one when we call __do_softirq() 968 in the end of an hardirq. 969 This spares a stack switch and improves cache usage on softirq 970 processing. 971 972config HAVE_SOFTIRQ_ON_OWN_STACK 973 bool 974 help 975 Architecture provides a function to run __do_softirq() on a 976 separate stack. 977 978config SOFTIRQ_ON_OWN_STACK 979 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 980 981config ALTERNATE_USER_ADDRESS_SPACE 982 bool 983 help 984 Architectures set this when the CPU uses separate address 985 spaces for kernel and user space pointers. In this case, the 986 access_ok() check on a __user pointer is skipped. 987 988config PGTABLE_LEVELS 989 int 990 default 2 991 992config ARCH_HAS_ELF_RANDOMIZE 993 bool 994 help 995 An architecture supports choosing randomized locations for 996 stack, mmap, brk, and ET_DYN. Defined functions: 997 - arch_mmap_rnd() 998 - arch_randomize_brk() 999 1000config HAVE_ARCH_MMAP_RND_BITS 1001 bool 1002 help 1003 An arch should select this symbol if it supports setting a variable 1004 number of bits for use in establishing the base address for mmap 1005 allocations, has MMU enabled and provides values for both: 1006 - ARCH_MMAP_RND_BITS_MIN 1007 - ARCH_MMAP_RND_BITS_MAX 1008 1009config HAVE_EXIT_THREAD 1010 bool 1011 help 1012 An architecture implements exit_thread. 1013 1014config ARCH_MMAP_RND_BITS_MIN 1015 int 1016 1017config ARCH_MMAP_RND_BITS_MAX 1018 int 1019 1020config ARCH_MMAP_RND_BITS_DEFAULT 1021 int 1022 1023config ARCH_MMAP_RND_BITS 1024 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1025 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1026 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1027 default ARCH_MMAP_RND_BITS_MIN 1028 depends on HAVE_ARCH_MMAP_RND_BITS 1029 help 1030 This value can be used to select the number of bits to use to 1031 determine the random offset to the base address of vma regions 1032 resulting from mmap allocations. This value will be bounded 1033 by the architecture's minimum and maximum supported values. 1034 1035 This value can be changed after boot using the 1036 /proc/sys/vm/mmap_rnd_bits tunable 1037 1038config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1039 bool 1040 help 1041 An arch should select this symbol if it supports running applications 1042 in compatibility mode, supports setting a variable number of bits for 1043 use in establishing the base address for mmap allocations, has MMU 1044 enabled and provides values for both: 1045 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1046 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1047 1048config ARCH_MMAP_RND_COMPAT_BITS_MIN 1049 int 1050 1051config ARCH_MMAP_RND_COMPAT_BITS_MAX 1052 int 1053 1054config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1055 int 1056 1057config ARCH_MMAP_RND_COMPAT_BITS 1058 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1059 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1060 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1061 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1062 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1063 help 1064 This value can be used to select the number of bits to use to 1065 determine the random offset to the base address of vma regions 1066 resulting from mmap allocations for compatible applications This 1067 value will be bounded by the architecture's minimum and maximum 1068 supported values. 1069 1070 This value can be changed after boot using the 1071 /proc/sys/vm/mmap_rnd_compat_bits tunable 1072 1073config HAVE_ARCH_COMPAT_MMAP_BASES 1074 bool 1075 help 1076 This allows 64bit applications to invoke 32-bit mmap() syscall 1077 and vice-versa 32-bit applications to call 64-bit mmap(). 1078 Required for applications doing different bitness syscalls. 1079 1080config PAGE_SIZE_LESS_THAN_64KB 1081 def_bool y 1082 depends on !ARM64_64K_PAGES 1083 depends on !IA64_PAGE_SIZE_64KB 1084 depends on !PAGE_SIZE_64KB 1085 depends on !PARISC_PAGE_SIZE_64KB 1086 depends on PAGE_SIZE_LESS_THAN_256KB 1087 1088config PAGE_SIZE_LESS_THAN_256KB 1089 def_bool y 1090 depends on !PAGE_SIZE_256KB 1091 1092# This allows to use a set of generic functions to determine mmap base 1093# address by giving priority to top-down scheme only if the process 1094# is not in legacy mode (compat task, unlimited stack size or 1095# sysctl_legacy_va_layout). 1096# Architecture that selects this option can provide its own version of: 1097# - STACK_RND_MASK 1098config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1099 bool 1100 depends on MMU 1101 select ARCH_HAS_ELF_RANDOMIZE 1102 1103config HAVE_OBJTOOL 1104 bool 1105 1106config HAVE_JUMP_LABEL_HACK 1107 bool 1108 1109config HAVE_NOINSTR_HACK 1110 bool 1111 1112config HAVE_NOINSTR_VALIDATION 1113 bool 1114 1115config HAVE_UACCESS_VALIDATION 1116 bool 1117 select OBJTOOL 1118 1119config HAVE_STACK_VALIDATION 1120 bool 1121 help 1122 Architecture supports objtool compile-time frame pointer rule 1123 validation. 1124 1125config HAVE_RELIABLE_STACKTRACE 1126 bool 1127 help 1128 Architecture has either save_stack_trace_tsk_reliable() or 1129 arch_stack_walk_reliable() function which only returns a stack trace 1130 if it can guarantee the trace is reliable. 1131 1132config HAVE_ARCH_HASH 1133 bool 1134 default n 1135 help 1136 If this is set, the architecture provides an <asm/hash.h> 1137 file which provides platform-specific implementations of some 1138 functions in <linux/hash.h> or fs/namei.c. 1139 1140config HAVE_ARCH_NVRAM_OPS 1141 bool 1142 1143config ISA_BUS_API 1144 def_bool ISA 1145 1146# 1147# ABI hall of shame 1148# 1149config CLONE_BACKWARDS 1150 bool 1151 help 1152 Architecture has tls passed as the 4th argument of clone(2), 1153 not the 5th one. 1154 1155config CLONE_BACKWARDS2 1156 bool 1157 help 1158 Architecture has the first two arguments of clone(2) swapped. 1159 1160config CLONE_BACKWARDS3 1161 bool 1162 help 1163 Architecture has tls passed as the 3rd argument of clone(2), 1164 not the 5th one. 1165 1166config ODD_RT_SIGACTION 1167 bool 1168 help 1169 Architecture has unusual rt_sigaction(2) arguments 1170 1171config OLD_SIGSUSPEND 1172 bool 1173 help 1174 Architecture has old sigsuspend(2) syscall, of one-argument variety 1175 1176config OLD_SIGSUSPEND3 1177 bool 1178 help 1179 Even weirder antique ABI - three-argument sigsuspend(2) 1180 1181config OLD_SIGACTION 1182 bool 1183 help 1184 Architecture has old sigaction(2) syscall. Nope, not the same 1185 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1186 but fairly different variant of sigaction(2), thanks to OSF/1 1187 compatibility... 1188 1189config COMPAT_OLD_SIGACTION 1190 bool 1191 1192config COMPAT_32BIT_TIME 1193 bool "Provide system calls for 32-bit time_t" 1194 default !64BIT || COMPAT 1195 help 1196 This enables 32 bit time_t support in addition to 64 bit time_t support. 1197 This is relevant on all 32-bit architectures, and 64-bit architectures 1198 as part of compat syscall handling. 1199 1200config ARCH_NO_PREEMPT 1201 bool 1202 1203config ARCH_EPHEMERAL_INODES 1204 def_bool n 1205 help 1206 An arch should select this symbol if it doesn't keep track of inode 1207 instances on its own, but instead relies on something else (e.g. the 1208 host kernel for an UML kernel). 1209 1210config ARCH_SUPPORTS_RT 1211 bool 1212 1213config CPU_NO_EFFICIENT_FFS 1214 def_bool n 1215 1216config HAVE_ARCH_VMAP_STACK 1217 def_bool n 1218 help 1219 An arch should select this symbol if it can support kernel stacks 1220 in vmalloc space. This means: 1221 1222 - vmalloc space must be large enough to hold many kernel stacks. 1223 This may rule out many 32-bit architectures. 1224 1225 - Stacks in vmalloc space need to work reliably. For example, if 1226 vmap page tables are created on demand, either this mechanism 1227 needs to work while the stack points to a virtual address with 1228 unpopulated page tables or arch code (switch_to() and switch_mm(), 1229 most likely) needs to ensure that the stack's page table entries 1230 are populated before running on a possibly unpopulated stack. 1231 1232 - If the stack overflows into a guard page, something reasonable 1233 should happen. The definition of "reasonable" is flexible, but 1234 instantly rebooting without logging anything would be unfriendly. 1235 1236config VMAP_STACK 1237 default y 1238 bool "Use a virtually-mapped stack" 1239 depends on HAVE_ARCH_VMAP_STACK 1240 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1241 help 1242 Enable this if you want the use virtually-mapped kernel stacks 1243 with guard pages. This causes kernel stack overflows to be 1244 caught immediately rather than causing difficult-to-diagnose 1245 corruption. 1246 1247 To use this with software KASAN modes, the architecture must support 1248 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1249 must be enabled. 1250 1251config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1252 def_bool n 1253 help 1254 An arch should select this symbol if it can support kernel stack 1255 offset randomization with calls to add_random_kstack_offset() 1256 during syscall entry and choose_random_kstack_offset() during 1257 syscall exit. Careful removal of -fstack-protector-strong and 1258 -fstack-protector should also be applied to the entry code and 1259 closely examined, as the artificial stack bump looks like an array 1260 to the compiler, so it will attempt to add canary checks regardless 1261 of the static branch state. 1262 1263config RANDOMIZE_KSTACK_OFFSET 1264 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1265 default y 1266 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1267 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1268 help 1269 The kernel stack offset can be randomized (after pt_regs) by 1270 roughly 5 bits of entropy, frustrating memory corruption 1271 attacks that depend on stack address determinism or 1272 cross-syscall address exposures. 1273 1274 The feature is controlled via the "randomize_kstack_offset=on/off" 1275 kernel boot param, and if turned off has zero overhead due to its use 1276 of static branches (see JUMP_LABEL). 1277 1278 If unsure, say Y. 1279 1280config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1281 bool "Default state of kernel stack offset randomization" 1282 depends on RANDOMIZE_KSTACK_OFFSET 1283 help 1284 Kernel stack offset randomization is controlled by kernel boot param 1285 "randomize_kstack_offset=on/off", and this config chooses the default 1286 boot state. 1287 1288config ARCH_OPTIONAL_KERNEL_RWX 1289 def_bool n 1290 1291config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1292 def_bool n 1293 1294config ARCH_HAS_STRICT_KERNEL_RWX 1295 def_bool n 1296 1297config STRICT_KERNEL_RWX 1298 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1299 depends on ARCH_HAS_STRICT_KERNEL_RWX 1300 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1301 help 1302 If this is set, kernel text and rodata memory will be made read-only, 1303 and non-text memory will be made non-executable. This provides 1304 protection against certain security exploits (e.g. executing the heap 1305 or modifying text) 1306 1307 These features are considered standard security practice these days. 1308 You should say Y here in almost all cases. 1309 1310config ARCH_HAS_STRICT_MODULE_RWX 1311 def_bool n 1312 1313config STRICT_MODULE_RWX 1314 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1315 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1316 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1317 help 1318 If this is set, module text and rodata memory will be made read-only, 1319 and non-text memory will be made non-executable. This provides 1320 protection against certain security exploits (e.g. writing to text) 1321 1322# select if the architecture provides an asm/dma-direct.h header 1323config ARCH_HAS_PHYS_TO_DMA 1324 bool 1325 1326config HAVE_ARCH_COMPILER_H 1327 bool 1328 help 1329 An architecture can select this if it provides an 1330 asm/compiler.h header that should be included after 1331 linux/compiler-*.h in order to override macro definitions that those 1332 headers generally provide. 1333 1334config HAVE_ARCH_PREL32_RELOCATIONS 1335 bool 1336 help 1337 May be selected by an architecture if it supports place-relative 1338 32-bit relocations, both in the toolchain and in the module loader, 1339 in which case relative references can be used in special sections 1340 for PCI fixup, initcalls etc which are only half the size on 64 bit 1341 architectures, and don't require runtime relocation on relocatable 1342 kernels. 1343 1344config ARCH_USE_MEMREMAP_PROT 1345 bool 1346 1347config LOCK_EVENT_COUNTS 1348 bool "Locking event counts collection" 1349 depends on DEBUG_FS 1350 help 1351 Enable light-weight counting of various locking related events 1352 in the system with minimal performance impact. This reduces 1353 the chance of application behavior change because of timing 1354 differences. The counts are reported via debugfs. 1355 1356# Select if the architecture has support for applying RELR relocations. 1357config ARCH_HAS_RELR 1358 bool 1359 1360config RELR 1361 bool "Use RELR relocation packing" 1362 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1363 default y 1364 help 1365 Store the kernel's dynamic relocations in the RELR relocation packing 1366 format. Requires a compatible linker (LLD supports this feature), as 1367 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1368 are compatible). 1369 1370config ARCH_HAS_MEM_ENCRYPT 1371 bool 1372 1373config ARCH_HAS_CC_PLATFORM 1374 bool 1375 1376config HAVE_SPARSE_SYSCALL_NR 1377 bool 1378 help 1379 An architecture should select this if its syscall numbering is sparse 1380 to save space. For example, MIPS architecture has a syscall array with 1381 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1382 related optimizations for a given architecture. 1383 1384config ARCH_HAS_VDSO_DATA 1385 bool 1386 1387config HAVE_STATIC_CALL 1388 bool 1389 1390config HAVE_STATIC_CALL_INLINE 1391 bool 1392 depends on HAVE_STATIC_CALL 1393 select OBJTOOL 1394 1395config HAVE_PREEMPT_DYNAMIC 1396 bool 1397 1398config HAVE_PREEMPT_DYNAMIC_CALL 1399 bool 1400 depends on HAVE_STATIC_CALL 1401 select HAVE_PREEMPT_DYNAMIC 1402 help 1403 An architecture should select this if it can handle the preemption 1404 model being selected at boot time using static calls. 1405 1406 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1407 preemption function will be patched directly. 1408 1409 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1410 call to a preemption function will go through a trampoline, and the 1411 trampoline will be patched. 1412 1413 It is strongly advised to support inline static call to avoid any 1414 overhead. 1415 1416config HAVE_PREEMPT_DYNAMIC_KEY 1417 bool 1418 depends on HAVE_ARCH_JUMP_LABEL 1419 select HAVE_PREEMPT_DYNAMIC 1420 help 1421 An architecture should select this if it can handle the preemption 1422 model being selected at boot time using static keys. 1423 1424 Each preemption function will be given an early return based on a 1425 static key. This should have slightly lower overhead than non-inline 1426 static calls, as this effectively inlines each trampoline into the 1427 start of its callee. This may avoid redundant work, and may 1428 integrate better with CFI schemes. 1429 1430 This will have greater overhead than using inline static calls as 1431 the call to the preemption function cannot be entirely elided. 1432 1433config ARCH_WANT_LD_ORPHAN_WARN 1434 bool 1435 help 1436 An arch should select this symbol once all linker sections are explicitly 1437 included, size-asserted, or discarded in the linker scripts. This is 1438 important because we never want expected sections to be placed heuristically 1439 by the linker, since the locations of such sections can change between linker 1440 versions. 1441 1442config HAVE_ARCH_PFN_VALID 1443 bool 1444 1445config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1446 bool 1447 1448config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1449 bool 1450 1451config ARCH_SPLIT_ARG64 1452 bool 1453 help 1454 If a 32-bit architecture requires 64-bit arguments to be split into 1455 pairs of 32-bit arguments, select this option. 1456 1457config ARCH_HAS_ELFCORE_COMPAT 1458 bool 1459 1460config ARCH_HAS_PARANOID_L1D_FLUSH 1461 bool 1462 1463config ARCH_HAVE_TRACE_MMIO_ACCESS 1464 bool 1465 1466config DYNAMIC_SIGFRAME 1467 bool 1468 1469# Select, if arch has a named attribute group bound to NUMA device nodes. 1470config HAVE_ARCH_NODE_DEV_GROUP 1471 bool 1472 1473config ARCH_HAS_NONLEAF_PMD_YOUNG 1474 bool 1475 help 1476 Architectures that select this option are capable of setting the 1477 accessed bit in non-leaf PMD entries when using them as part of linear 1478 address translations. Page table walkers that clear the accessed bit 1479 may use this capability to reduce their search space. 1480 1481source "kernel/gcov/Kconfig" 1482 1483source "scripts/gcc-plugins/Kconfig" 1484 1485config FUNCTION_ALIGNMENT_4B 1486 bool 1487 1488config FUNCTION_ALIGNMENT_8B 1489 bool 1490 1491config FUNCTION_ALIGNMENT_16B 1492 bool 1493 1494config FUNCTION_ALIGNMENT_32B 1495 bool 1496 1497config FUNCTION_ALIGNMENT_64B 1498 bool 1499 1500config FUNCTION_ALIGNMENT 1501 int 1502 default 64 if FUNCTION_ALIGNMENT_64B 1503 default 32 if FUNCTION_ALIGNMENT_32B 1504 default 16 if FUNCTION_ALIGNMENT_16B 1505 default 8 if FUNCTION_ALIGNMENT_8B 1506 default 4 if FUNCTION_ALIGNMENT_4B 1507 default 0 1508 1509endmenu 1510