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 37# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 38config HOTPLUG_CORE_SYNC 39 bool 40 41# Basic CPU dead synchronization selected by architecture 42config HOTPLUG_CORE_SYNC_DEAD 43 bool 44 select HOTPLUG_CORE_SYNC 45 46# Full CPU synchronization with alive state selected by architecture 47config HOTPLUG_CORE_SYNC_FULL 48 bool 49 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 50 select HOTPLUG_CORE_SYNC 51 52config HOTPLUG_SPLIT_STARTUP 53 bool 54 select HOTPLUG_CORE_SYNC_FULL 55 56config HOTPLUG_PARALLEL 57 bool 58 select HOTPLUG_SPLIT_STARTUP 59 60config GENERIC_ENTRY 61 bool 62 63config KPROBES 64 bool "Kprobes" 65 depends on MODULES 66 depends on HAVE_KPROBES 67 select KALLSYMS 68 select TASKS_RCU if PREEMPTION 69 help 70 Kprobes allows you to trap at almost any kernel address and 71 execute a callback function. register_kprobe() establishes 72 a probepoint and specifies the callback. Kprobes is useful 73 for kernel debugging, non-intrusive instrumentation and testing. 74 If in doubt, say "N". 75 76config JUMP_LABEL 77 bool "Optimize very unlikely/likely branches" 78 depends on HAVE_ARCH_JUMP_LABEL 79 select OBJTOOL if HAVE_JUMP_LABEL_HACK 80 help 81 This option enables a transparent branch optimization that 82 makes certain almost-always-true or almost-always-false branch 83 conditions even cheaper to execute within the kernel. 84 85 Certain performance-sensitive kernel code, such as trace points, 86 scheduler functionality, networking code and KVM have such 87 branches and include support for this optimization technique. 88 89 If it is detected that the compiler has support for "asm goto", 90 the kernel will compile such branches with just a nop 91 instruction. When the condition flag is toggled to true, the 92 nop will be converted to a jump instruction to execute the 93 conditional block of instructions. 94 95 This technique lowers overhead and stress on the branch prediction 96 of the processor and generally makes the kernel faster. The update 97 of the condition is slower, but those are always very rare. 98 99 ( On 32-bit x86, the necessary options added to the compiler 100 flags may increase the size of the kernel slightly. ) 101 102config STATIC_KEYS_SELFTEST 103 bool "Static key selftest" 104 depends on JUMP_LABEL 105 help 106 Boot time self-test of the branch patching code. 107 108config STATIC_CALL_SELFTEST 109 bool "Static call selftest" 110 depends on HAVE_STATIC_CALL 111 help 112 Boot time self-test of the call patching code. 113 114config OPTPROBES 115 def_bool y 116 depends on KPROBES && HAVE_OPTPROBES 117 select TASKS_RCU if PREEMPTION 118 119config KPROBES_ON_FTRACE 120 def_bool y 121 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 122 depends on DYNAMIC_FTRACE_WITH_REGS 123 help 124 If function tracer is enabled and the arch supports full 125 passing of pt_regs to function tracing, then kprobes can 126 optimize on top of function tracing. 127 128config UPROBES 129 def_bool n 130 depends on ARCH_SUPPORTS_UPROBES 131 help 132 Uprobes is the user-space counterpart to kprobes: they 133 enable instrumentation applications (such as 'perf probe') 134 to establish unintrusive probes in user-space binaries and 135 libraries, by executing handler functions when the probes 136 are hit by user-space applications. 137 138 ( These probes come in the form of single-byte breakpoints, 139 managed by the kernel and kept transparent to the probed 140 application. ) 141 142config HAVE_64BIT_ALIGNED_ACCESS 143 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 144 help 145 Some architectures require 64 bit accesses to be 64 bit 146 aligned, which also requires structs containing 64 bit values 147 to be 64 bit aligned too. This includes some 32 bit 148 architectures which can do 64 bit accesses, as well as 64 bit 149 architectures without unaligned access. 150 151 This symbol should be selected by an architecture if 64 bit 152 accesses are required to be 64 bit aligned in this way even 153 though it is not a 64 bit architecture. 154 155 See Documentation/core-api/unaligned-memory-access.rst for 156 more information on the topic of unaligned memory accesses. 157 158config HAVE_EFFICIENT_UNALIGNED_ACCESS 159 bool 160 help 161 Some architectures are unable to perform unaligned accesses 162 without the use of get_unaligned/put_unaligned. Others are 163 unable to perform such accesses efficiently (e.g. trap on 164 unaligned access and require fixing it up in the exception 165 handler.) 166 167 This symbol should be selected by an architecture if it can 168 perform unaligned accesses efficiently to allow different 169 code paths to be selected for these cases. Some network 170 drivers, for example, could opt to not fix up alignment 171 problems with received packets if doing so would not help 172 much. 173 174 See Documentation/core-api/unaligned-memory-access.rst for more 175 information on the topic of unaligned memory accesses. 176 177config ARCH_USE_BUILTIN_BSWAP 178 bool 179 help 180 Modern versions of GCC (since 4.4) have builtin functions 181 for handling byte-swapping. Using these, instead of the old 182 inline assembler that the architecture code provides in the 183 __arch_bswapXX() macros, allows the compiler to see what's 184 happening and offers more opportunity for optimisation. In 185 particular, the compiler will be able to combine the byteswap 186 with a nearby load or store and use load-and-swap or 187 store-and-swap instructions if the architecture has them. It 188 should almost *never* result in code which is worse than the 189 hand-coded assembler in <asm/swab.h>. But just in case it 190 does, the use of the builtins is optional. 191 192 Any architecture with load-and-swap or store-and-swap 193 instructions should set this. And it shouldn't hurt to set it 194 on architectures that don't have such instructions. 195 196config KRETPROBES 197 def_bool y 198 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 199 200config KRETPROBE_ON_RETHOOK 201 def_bool y 202 depends on HAVE_RETHOOK 203 depends on KRETPROBES 204 select RETHOOK 205 206config USER_RETURN_NOTIFIER 207 bool 208 depends on HAVE_USER_RETURN_NOTIFIER 209 help 210 Provide a kernel-internal notification when a cpu is about to 211 switch to user mode. 212 213config HAVE_IOREMAP_PROT 214 bool 215 216config HAVE_KPROBES 217 bool 218 219config HAVE_KRETPROBES 220 bool 221 222config HAVE_OPTPROBES 223 bool 224 225config HAVE_KPROBES_ON_FTRACE 226 bool 227 228config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 229 bool 230 help 231 Since kretprobes modifies return address on the stack, the 232 stacktrace may see the kretprobe trampoline address instead 233 of correct one. If the architecture stacktrace code and 234 unwinder can adjust such entries, select this configuration. 235 236config HAVE_FUNCTION_ERROR_INJECTION 237 bool 238 239config HAVE_NMI 240 bool 241 242config HAVE_FUNCTION_DESCRIPTORS 243 bool 244 245config TRACE_IRQFLAGS_SUPPORT 246 bool 247 248config TRACE_IRQFLAGS_NMI_SUPPORT 249 bool 250 251# 252# An arch should select this if it provides all these things: 253# 254# task_pt_regs() in asm/processor.h or asm/ptrace.h 255# arch_has_single_step() if there is hardware single-step support 256# arch_has_block_step() if there is hardware block-step support 257# asm/syscall.h supplying asm-generic/syscall.h interface 258# linux/regset.h user_regset interfaces 259# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 260# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 261# TIF_NOTIFY_RESUME calls resume_user_mode_work() 262# 263config HAVE_ARCH_TRACEHOOK 264 bool 265 266config HAVE_DMA_CONTIGUOUS 267 bool 268 269config GENERIC_SMP_IDLE_THREAD 270 bool 271 272config GENERIC_IDLE_POLL_SETUP 273 bool 274 275config ARCH_HAS_FORTIFY_SOURCE 276 bool 277 help 278 An architecture should select this when it can successfully 279 build and run with CONFIG_FORTIFY_SOURCE. 280 281# 282# Select if the arch provides a historic keepinit alias for the retain_initrd 283# command line option 284# 285config ARCH_HAS_KEEPINITRD 286 bool 287 288# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 289config ARCH_HAS_SET_MEMORY 290 bool 291 292# Select if arch has all set_direct_map_invalid/default() functions 293config ARCH_HAS_SET_DIRECT_MAP 294 bool 295 296# 297# Select if the architecture provides the arch_dma_set_uncached symbol to 298# either provide an uncached segment alias for a DMA allocation, or 299# to remap the page tables in place. 300# 301config ARCH_HAS_DMA_SET_UNCACHED 302 bool 303 304# 305# Select if the architectures provides the arch_dma_clear_uncached symbol 306# to undo an in-place page table remap for uncached access. 307# 308config ARCH_HAS_DMA_CLEAR_UNCACHED 309 bool 310 311config ARCH_HAS_CPU_FINALIZE_INIT 312 bool 313 314# Select if arch init_task must go in the __init_task_data section 315config ARCH_TASK_STRUCT_ON_STACK 316 bool 317 318# Select if arch has its private alloc_task_struct() function 319config ARCH_TASK_STRUCT_ALLOCATOR 320 bool 321 322config HAVE_ARCH_THREAD_STRUCT_WHITELIST 323 bool 324 depends on !ARCH_TASK_STRUCT_ALLOCATOR 325 help 326 An architecture should select this to provide hardened usercopy 327 knowledge about what region of the thread_struct should be 328 whitelisted for copying to userspace. Normally this is only the 329 FPU registers. Specifically, arch_thread_struct_whitelist() 330 should be implemented. Without this, the entire thread_struct 331 field in task_struct will be left whitelisted. 332 333# Select if arch has its private alloc_thread_stack() function 334config ARCH_THREAD_STACK_ALLOCATOR 335 bool 336 337# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 338config ARCH_WANTS_DYNAMIC_TASK_STRUCT 339 bool 340 341config ARCH_WANTS_NO_INSTR 342 bool 343 help 344 An architecture should select this if the noinstr macro is being used on 345 functions to denote that the toolchain should avoid instrumenting such 346 functions and is required for correctness. 347 348config ARCH_32BIT_OFF_T 349 bool 350 depends on !64BIT 351 help 352 All new 32-bit architectures should have 64-bit off_t type on 353 userspace side which corresponds to the loff_t kernel type. This 354 is the requirement for modern ABIs. Some existing architectures 355 still support 32-bit off_t. This option is enabled for all such 356 architectures explicitly. 357 358# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 359config ARCH_32BIT_USTAT_F_TINODE 360 bool 361 362config HAVE_ASM_MODVERSIONS 363 bool 364 help 365 This symbol should be selected by an architecture if it provides 366 <asm/asm-prototypes.h> to support the module versioning for symbols 367 exported from assembly code. 368 369config HAVE_REGS_AND_STACK_ACCESS_API 370 bool 371 help 372 This symbol should be selected by an architecture if it supports 373 the API needed to access registers and stack entries from pt_regs, 374 declared in asm/ptrace.h 375 For example the kprobes-based event tracer needs this API. 376 377config HAVE_RSEQ 378 bool 379 depends on HAVE_REGS_AND_STACK_ACCESS_API 380 help 381 This symbol should be selected by an architecture if it 382 supports an implementation of restartable sequences. 383 384config HAVE_RUST 385 bool 386 help 387 This symbol should be selected by an architecture if it 388 supports Rust. 389 390config HAVE_FUNCTION_ARG_ACCESS_API 391 bool 392 help 393 This symbol should be selected by an architecture if it supports 394 the API needed to access function arguments from pt_regs, 395 declared in asm/ptrace.h 396 397config HAVE_HW_BREAKPOINT 398 bool 399 depends on PERF_EVENTS 400 401config HAVE_MIXED_BREAKPOINTS_REGS 402 bool 403 depends on HAVE_HW_BREAKPOINT 404 help 405 Depending on the arch implementation of hardware breakpoints, 406 some of them have separate registers for data and instruction 407 breakpoints addresses, others have mixed registers to store 408 them but define the access type in a control register. 409 Select this option if your arch implements breakpoints under the 410 latter fashion. 411 412config HAVE_USER_RETURN_NOTIFIER 413 bool 414 415config HAVE_PERF_EVENTS_NMI 416 bool 417 help 418 System hardware can generate an NMI using the perf event 419 subsystem. Also has support for calculating CPU cycle events 420 to determine how many clock cycles in a given period. 421 422config HAVE_HARDLOCKUP_DETECTOR_PERF 423 bool 424 depends on HAVE_PERF_EVENTS_NMI 425 help 426 The arch chooses to use the generic perf-NMI-based hardlockup 427 detector. Must define HAVE_PERF_EVENTS_NMI. 428 429config HAVE_NMI_WATCHDOG 430 depends on HAVE_NMI 431 bool 432 help 433 The arch provides a low level NMI watchdog. It provides 434 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 435 436config HAVE_HARDLOCKUP_DETECTOR_ARCH 437 bool 438 select HAVE_NMI_WATCHDOG 439 help 440 The arch chooses to provide its own hardlockup detector, which is 441 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 442 interfaces and parameters provided by hardlockup detector subsystem. 443 444config HAVE_PERF_REGS 445 bool 446 help 447 Support selective register dumps for perf events. This includes 448 bit-mapping of each registers and a unique architecture id. 449 450config HAVE_PERF_USER_STACK_DUMP 451 bool 452 help 453 Support user stack dumps for perf event samples. This needs 454 access to the user stack pointer which is not unified across 455 architectures. 456 457config HAVE_ARCH_JUMP_LABEL 458 bool 459 460config HAVE_ARCH_JUMP_LABEL_RELATIVE 461 bool 462 463config MMU_GATHER_TABLE_FREE 464 bool 465 466config MMU_GATHER_RCU_TABLE_FREE 467 bool 468 select MMU_GATHER_TABLE_FREE 469 470config MMU_GATHER_PAGE_SIZE 471 bool 472 473config MMU_GATHER_NO_RANGE 474 bool 475 select MMU_GATHER_MERGE_VMAS 476 477config MMU_GATHER_NO_FLUSH_CACHE 478 bool 479 480config MMU_GATHER_MERGE_VMAS 481 bool 482 483config MMU_GATHER_NO_GATHER 484 bool 485 depends on MMU_GATHER_TABLE_FREE 486 487config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 488 bool 489 help 490 Temporary select until all architectures can be converted to have 491 irqs disabled over activate_mm. Architectures that do IPI based TLB 492 shootdowns should enable this. 493 494# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 495# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 496# to/from kernel threads when the same mm is running on a lot of CPUs (a large 497# multi-threaded application), by reducing contention on the mm refcount. 498# 499# This can be disabled if the architecture ensures no CPUs are using an mm as a 500# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 501# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 502# final exit(2) TLB flush, for example. 503# 504# To implement this, an arch *must*: 505# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 506# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 507# converted already). 508config MMU_LAZY_TLB_REFCOUNT 509 def_bool y 510 depends on !MMU_LAZY_TLB_SHOOTDOWN 511 512# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 513# mm as a lazy tlb beyond its last reference count, by shooting down these 514# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 515# be using the mm as a lazy tlb, so that they may switch themselves to using 516# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 517# may be using mm as a lazy tlb mm. 518# 519# To implement this, an arch *must*: 520# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 521# at least all possible CPUs in which the mm is lazy. 522# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 523config MMU_LAZY_TLB_SHOOTDOWN 524 bool 525 526config ARCH_HAVE_NMI_SAFE_CMPXCHG 527 bool 528 529config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 530 bool 531 532config HAVE_ALIGNED_STRUCT_PAGE 533 bool 534 help 535 This makes sure that struct pages are double word aligned and that 536 e.g. the SLUB allocator can perform double word atomic operations 537 on a struct page for better performance. However selecting this 538 might increase the size of a struct page by a word. 539 540config HAVE_CMPXCHG_LOCAL 541 bool 542 543config HAVE_CMPXCHG_DOUBLE 544 bool 545 546config ARCH_WEAK_RELEASE_ACQUIRE 547 bool 548 549config ARCH_WANT_IPC_PARSE_VERSION 550 bool 551 552config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 553 bool 554 555config ARCH_WANT_OLD_COMPAT_IPC 556 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 557 bool 558 559config HAVE_ARCH_SECCOMP 560 bool 561 help 562 An arch should select this symbol to support seccomp mode 1 (the fixed 563 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 564 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 565 - __NR_seccomp_read_32 566 - __NR_seccomp_write_32 567 - __NR_seccomp_exit_32 568 - __NR_seccomp_sigreturn_32 569 570config HAVE_ARCH_SECCOMP_FILTER 571 bool 572 select HAVE_ARCH_SECCOMP 573 help 574 An arch should select this symbol if it provides all of these things: 575 - all the requirements for HAVE_ARCH_SECCOMP 576 - syscall_get_arch() 577 - syscall_get_arguments() 578 - syscall_rollback() 579 - syscall_set_return_value() 580 - SIGSYS siginfo_t support 581 - secure_computing is called from a ptrace_event()-safe context 582 - secure_computing return value is checked and a return value of -1 583 results in the system call being skipped immediately. 584 - seccomp syscall wired up 585 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 586 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 587 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 588 589config SECCOMP 590 prompt "Enable seccomp to safely execute untrusted bytecode" 591 def_bool y 592 depends on HAVE_ARCH_SECCOMP 593 help 594 This kernel feature is useful for number crunching applications 595 that may need to handle untrusted bytecode during their 596 execution. By using pipes or other transports made available 597 to the process as file descriptors supporting the read/write 598 syscalls, it's possible to isolate those applications in their 599 own address space using seccomp. Once seccomp is enabled via 600 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 601 disabled and the task is only allowed to execute a few safe 602 syscalls defined by each seccomp mode. 603 604 If unsure, say Y. 605 606config SECCOMP_FILTER 607 def_bool y 608 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 609 help 610 Enable tasks to build secure computing environments defined 611 in terms of Berkeley Packet Filter programs which implement 612 task-defined system call filtering polices. 613 614 See Documentation/userspace-api/seccomp_filter.rst for details. 615 616config SECCOMP_CACHE_DEBUG 617 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 618 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 619 depends on PROC_FS 620 help 621 This enables the /proc/pid/seccomp_cache interface to monitor 622 seccomp cache data. The file format is subject to change. Reading 623 the file requires CAP_SYS_ADMIN. 624 625 This option is for debugging only. Enabling presents the risk that 626 an adversary may be able to infer the seccomp filter logic. 627 628 If unsure, say N. 629 630config HAVE_ARCH_STACKLEAK 631 bool 632 help 633 An architecture should select this if it has the code which 634 fills the used part of the kernel stack with the STACKLEAK_POISON 635 value before returning from system calls. 636 637config HAVE_STACKPROTECTOR 638 bool 639 help 640 An arch should select this symbol if: 641 - it has implemented a stack canary (e.g. __stack_chk_guard) 642 643config STACKPROTECTOR 644 bool "Stack Protector buffer overflow detection" 645 depends on HAVE_STACKPROTECTOR 646 depends on $(cc-option,-fstack-protector) 647 default y 648 help 649 This option turns on the "stack-protector" GCC feature. This 650 feature puts, at the beginning of functions, a canary value on 651 the stack just before the return address, and validates 652 the value just before actually returning. Stack based buffer 653 overflows (that need to overwrite this return address) now also 654 overwrite the canary, which gets detected and the attack is then 655 neutralized via a kernel panic. 656 657 Functions will have the stack-protector canary logic added if they 658 have an 8-byte or larger character array on the stack. 659 660 This feature requires gcc version 4.2 or above, or a distribution 661 gcc with the feature backported ("-fstack-protector"). 662 663 On an x86 "defconfig" build, this feature adds canary checks to 664 about 3% of all kernel functions, which increases kernel code size 665 by about 0.3%. 666 667config STACKPROTECTOR_STRONG 668 bool "Strong Stack Protector" 669 depends on STACKPROTECTOR 670 depends on $(cc-option,-fstack-protector-strong) 671 default y 672 help 673 Functions will have the stack-protector canary logic added in any 674 of the following conditions: 675 676 - local variable's address used as part of the right hand side of an 677 assignment or function argument 678 - local variable is an array (or union containing an array), 679 regardless of array type or length 680 - uses register local variables 681 682 This feature requires gcc version 4.9 or above, or a distribution 683 gcc with the feature backported ("-fstack-protector-strong"). 684 685 On an x86 "defconfig" build, this feature adds canary checks to 686 about 20% of all kernel functions, which increases the kernel code 687 size by about 2%. 688 689config ARCH_SUPPORTS_SHADOW_CALL_STACK 690 bool 691 help 692 An architecture should select this if it supports the compiler's 693 Shadow Call Stack and implements runtime support for shadow stack 694 switching. 695 696config SHADOW_CALL_STACK 697 bool "Shadow Call Stack" 698 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 699 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 700 help 701 This option enables the compiler's Shadow Call Stack, which 702 uses a shadow stack to protect function return addresses from 703 being overwritten by an attacker. More information can be found 704 in the compiler's documentation: 705 706 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 707 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 708 709 Note that security guarantees in the kernel differ from the 710 ones documented for user space. The kernel must store addresses 711 of shadow stacks in memory, which means an attacker capable of 712 reading and writing arbitrary memory may be able to locate them 713 and hijack control flow by modifying the stacks. 714 715config DYNAMIC_SCS 716 bool 717 help 718 Set by the arch code if it relies on code patching to insert the 719 shadow call stack push and pop instructions rather than on the 720 compiler. 721 722config LTO 723 bool 724 help 725 Selected if the kernel will be built using the compiler's LTO feature. 726 727config LTO_CLANG 728 bool 729 select LTO 730 help 731 Selected if the kernel will be built using Clang's LTO feature. 732 733config ARCH_SUPPORTS_LTO_CLANG 734 bool 735 help 736 An architecture should select this option if it supports: 737 - compiling with Clang, 738 - compiling inline assembly with Clang's integrated assembler, 739 - and linking with LLD. 740 741config ARCH_SUPPORTS_LTO_CLANG_THIN 742 bool 743 help 744 An architecture should select this option if it can support Clang's 745 ThinLTO mode. 746 747config HAS_LTO_CLANG 748 def_bool y 749 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 750 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 751 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 752 depends on ARCH_SUPPORTS_LTO_CLANG 753 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 754 depends on !KASAN || KASAN_HW_TAGS 755 depends on !GCOV_KERNEL 756 help 757 The compiler and Kconfig options support building with Clang's 758 LTO. 759 760choice 761 prompt "Link Time Optimization (LTO)" 762 default LTO_NONE 763 help 764 This option enables Link Time Optimization (LTO), which allows the 765 compiler to optimize binaries globally. 766 767 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 768 so it's disabled by default. 769 770config LTO_NONE 771 bool "None" 772 help 773 Build the kernel normally, without Link Time Optimization (LTO). 774 775config LTO_CLANG_FULL 776 bool "Clang Full LTO (EXPERIMENTAL)" 777 depends on HAS_LTO_CLANG 778 depends on !COMPILE_TEST 779 select LTO_CLANG 780 help 781 This option enables Clang's full Link Time Optimization (LTO), which 782 allows the compiler to optimize the kernel globally. If you enable 783 this option, the compiler generates LLVM bitcode instead of ELF 784 object files, and the actual compilation from bitcode happens at 785 the LTO link step, which may take several minutes depending on the 786 kernel configuration. More information can be found from LLVM's 787 documentation: 788 789 https://llvm.org/docs/LinkTimeOptimization.html 790 791 During link time, this option can use a large amount of RAM, and 792 may take much longer than the ThinLTO option. 793 794config LTO_CLANG_THIN 795 bool "Clang ThinLTO (EXPERIMENTAL)" 796 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 797 select LTO_CLANG 798 help 799 This option enables Clang's ThinLTO, which allows for parallel 800 optimization and faster incremental compiles compared to the 801 CONFIG_LTO_CLANG_FULL option. More information can be found 802 from Clang's documentation: 803 804 https://clang.llvm.org/docs/ThinLTO.html 805 806 If unsure, say Y. 807endchoice 808 809config ARCH_SUPPORTS_CFI_CLANG 810 bool 811 help 812 An architecture should select this option if it can support Clang's 813 Control-Flow Integrity (CFI) checking. 814 815config ARCH_USES_CFI_TRAPS 816 bool 817 818config CFI_CLANG 819 bool "Use Clang's Control Flow Integrity (CFI)" 820 depends on ARCH_SUPPORTS_CFI_CLANG 821 depends on $(cc-option,-fsanitize=kcfi) 822 help 823 This option enables Clang’s forward-edge Control Flow Integrity 824 (CFI) checking, where the compiler injects a runtime check to each 825 indirect function call to ensure the target is a valid function with 826 the correct static type. This restricts possible call targets and 827 makes it more difficult for an attacker to exploit bugs that allow 828 the modification of stored function pointers. More information can be 829 found from Clang's documentation: 830 831 https://clang.llvm.org/docs/ControlFlowIntegrity.html 832 833config CFI_PERMISSIVE 834 bool "Use CFI in permissive mode" 835 depends on CFI_CLANG 836 help 837 When selected, Control Flow Integrity (CFI) violations result in a 838 warning instead of a kernel panic. This option should only be used 839 for finding indirect call type mismatches during development. 840 841 If unsure, say N. 842 843config HAVE_ARCH_WITHIN_STACK_FRAMES 844 bool 845 help 846 An architecture should select this if it can walk the kernel stack 847 frames to determine if an object is part of either the arguments 848 or local variables (i.e. that it excludes saved return addresses, 849 and similar) by implementing an inline arch_within_stack_frames(), 850 which is used by CONFIG_HARDENED_USERCOPY. 851 852config HAVE_CONTEXT_TRACKING_USER 853 bool 854 help 855 Provide kernel/user boundaries probes necessary for subsystems 856 that need it, such as userspace RCU extended quiescent state. 857 Syscalls need to be wrapped inside user_exit()-user_enter(), either 858 optimized behind static key or through the slow path using TIF_NOHZ 859 flag. Exceptions handlers must be wrapped as well. Irqs are already 860 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 861 handling on irq exit still need to be protected. 862 863config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 864 bool 865 help 866 Architecture neither relies on exception_enter()/exception_exit() 867 nor on schedule_user(). Also preempt_schedule_notrace() and 868 preempt_schedule_irq() can't be called in a preemptible section 869 while context tracking is CONTEXT_USER. This feature reflects a sane 870 entry implementation where the following requirements are met on 871 critical entry code, ie: before user_exit() or after user_enter(): 872 873 - Critical entry code isn't preemptible (or better yet: 874 not interruptible). 875 - No use of RCU read side critical sections, unless ct_nmi_enter() 876 got called. 877 - No use of instrumentation, unless instrumentation_begin() got 878 called. 879 880config HAVE_TIF_NOHZ 881 bool 882 help 883 Arch relies on TIF_NOHZ and syscall slow path to implement context 884 tracking calls to user_enter()/user_exit(). 885 886config HAVE_VIRT_CPU_ACCOUNTING 887 bool 888 889config HAVE_VIRT_CPU_ACCOUNTING_IDLE 890 bool 891 help 892 Architecture has its own way to account idle CPU time and therefore 893 doesn't implement vtime_account_idle(). 894 895config ARCH_HAS_SCALED_CPUTIME 896 bool 897 898config HAVE_VIRT_CPU_ACCOUNTING_GEN 899 bool 900 default y if 64BIT 901 help 902 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 903 Before enabling this option, arch code must be audited 904 to ensure there are no races in concurrent read/write of 905 cputime_t. For example, reading/writing 64-bit cputime_t on 906 some 32-bit arches may require multiple accesses, so proper 907 locking is needed to protect against concurrent accesses. 908 909config HAVE_IRQ_TIME_ACCOUNTING 910 bool 911 help 912 Archs need to ensure they use a high enough resolution clock to 913 support irq time accounting and then call enable_sched_clock_irqtime(). 914 915config HAVE_MOVE_PUD 916 bool 917 help 918 Architectures that select this are able to move page tables at the 919 PUD level. If there are only 3 page table levels, the move effectively 920 happens at the PGD level. 921 922config HAVE_MOVE_PMD 923 bool 924 help 925 Archs that select this are able to move page tables at the PMD level. 926 927config HAVE_ARCH_TRANSPARENT_HUGEPAGE 928 bool 929 930config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 931 bool 932 933config HAVE_ARCH_HUGE_VMAP 934 bool 935 936# 937# Archs that select this would be capable of PMD-sized vmaps (i.e., 938# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 939# must be used to enable allocations to use hugepages. 940# 941config HAVE_ARCH_HUGE_VMALLOC 942 depends on HAVE_ARCH_HUGE_VMAP 943 bool 944 945config ARCH_WANT_HUGE_PMD_SHARE 946 bool 947 948config HAVE_ARCH_SOFT_DIRTY 949 bool 950 951config HAVE_MOD_ARCH_SPECIFIC 952 bool 953 help 954 The arch uses struct mod_arch_specific to store data. Many arches 955 just need a simple module loader without arch specific data - those 956 should not enable this. 957 958config MODULES_USE_ELF_RELA 959 bool 960 help 961 Modules only use ELF RELA relocations. Modules with ELF REL 962 relocations will give an error. 963 964config MODULES_USE_ELF_REL 965 bool 966 help 967 Modules only use ELF REL relocations. Modules with ELF RELA 968 relocations will give an error. 969 970config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 971 bool 972 help 973 For architectures like powerpc/32 which have constraints on module 974 allocation and need to allocate module data outside of module area. 975 976config HAVE_IRQ_EXIT_ON_IRQ_STACK 977 bool 978 help 979 Architecture doesn't only execute the irq handler on the irq stack 980 but also irq_exit(). This way we can process softirqs on this irq 981 stack instead of switching to a new one when we call __do_softirq() 982 in the end of an hardirq. 983 This spares a stack switch and improves cache usage on softirq 984 processing. 985 986config HAVE_SOFTIRQ_ON_OWN_STACK 987 bool 988 help 989 Architecture provides a function to run __do_softirq() on a 990 separate stack. 991 992config SOFTIRQ_ON_OWN_STACK 993 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 994 995config ALTERNATE_USER_ADDRESS_SPACE 996 bool 997 help 998 Architectures set this when the CPU uses separate address 999 spaces for kernel and user space pointers. In this case, the 1000 access_ok() check on a __user pointer is skipped. 1001 1002config PGTABLE_LEVELS 1003 int 1004 default 2 1005 1006config ARCH_HAS_ELF_RANDOMIZE 1007 bool 1008 help 1009 An architecture supports choosing randomized locations for 1010 stack, mmap, brk, and ET_DYN. Defined functions: 1011 - arch_mmap_rnd() 1012 - arch_randomize_brk() 1013 1014config HAVE_ARCH_MMAP_RND_BITS 1015 bool 1016 help 1017 An arch should select this symbol if it supports setting a variable 1018 number of bits for use in establishing the base address for mmap 1019 allocations, has MMU enabled and provides values for both: 1020 - ARCH_MMAP_RND_BITS_MIN 1021 - ARCH_MMAP_RND_BITS_MAX 1022 1023config HAVE_EXIT_THREAD 1024 bool 1025 help 1026 An architecture implements exit_thread. 1027 1028config ARCH_MMAP_RND_BITS_MIN 1029 int 1030 1031config ARCH_MMAP_RND_BITS_MAX 1032 int 1033 1034config ARCH_MMAP_RND_BITS_DEFAULT 1035 int 1036 1037config ARCH_MMAP_RND_BITS 1038 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1039 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1040 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1041 default ARCH_MMAP_RND_BITS_MIN 1042 depends on HAVE_ARCH_MMAP_RND_BITS 1043 help 1044 This value can be used to select the number of bits to use to 1045 determine the random offset to the base address of vma regions 1046 resulting from mmap allocations. This value will be bounded 1047 by the architecture's minimum and maximum supported values. 1048 1049 This value can be changed after boot using the 1050 /proc/sys/vm/mmap_rnd_bits tunable 1051 1052config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1053 bool 1054 help 1055 An arch should select this symbol if it supports running applications 1056 in compatibility mode, supports setting a variable number of bits for 1057 use in establishing the base address for mmap allocations, has MMU 1058 enabled and provides values for both: 1059 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1060 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1061 1062config ARCH_MMAP_RND_COMPAT_BITS_MIN 1063 int 1064 1065config ARCH_MMAP_RND_COMPAT_BITS_MAX 1066 int 1067 1068config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1069 int 1070 1071config ARCH_MMAP_RND_COMPAT_BITS 1072 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1073 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1074 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1075 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1076 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1077 help 1078 This value can be used to select the number of bits to use to 1079 determine the random offset to the base address of vma regions 1080 resulting from mmap allocations for compatible applications This 1081 value will be bounded by the architecture's minimum and maximum 1082 supported values. 1083 1084 This value can be changed after boot using the 1085 /proc/sys/vm/mmap_rnd_compat_bits tunable 1086 1087config HAVE_ARCH_COMPAT_MMAP_BASES 1088 bool 1089 help 1090 This allows 64bit applications to invoke 32-bit mmap() syscall 1091 and vice-versa 32-bit applications to call 64-bit mmap(). 1092 Required for applications doing different bitness syscalls. 1093 1094config PAGE_SIZE_LESS_THAN_64KB 1095 def_bool y 1096 depends on !ARM64_64K_PAGES 1097 depends on !IA64_PAGE_SIZE_64KB 1098 depends on !PAGE_SIZE_64KB 1099 depends on !PARISC_PAGE_SIZE_64KB 1100 depends on PAGE_SIZE_LESS_THAN_256KB 1101 1102config PAGE_SIZE_LESS_THAN_256KB 1103 def_bool y 1104 depends on !PAGE_SIZE_256KB 1105 1106# This allows to use a set of generic functions to determine mmap base 1107# address by giving priority to top-down scheme only if the process 1108# is not in legacy mode (compat task, unlimited stack size or 1109# sysctl_legacy_va_layout). 1110# Architecture that selects this option can provide its own version of: 1111# - STACK_RND_MASK 1112config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1113 bool 1114 depends on MMU 1115 select ARCH_HAS_ELF_RANDOMIZE 1116 1117config HAVE_OBJTOOL 1118 bool 1119 1120config HAVE_JUMP_LABEL_HACK 1121 bool 1122 1123config HAVE_NOINSTR_HACK 1124 bool 1125 1126config HAVE_NOINSTR_VALIDATION 1127 bool 1128 1129config HAVE_UACCESS_VALIDATION 1130 bool 1131 select OBJTOOL 1132 1133config HAVE_STACK_VALIDATION 1134 bool 1135 help 1136 Architecture supports objtool compile-time frame pointer rule 1137 validation. 1138 1139config HAVE_RELIABLE_STACKTRACE 1140 bool 1141 help 1142 Architecture has either save_stack_trace_tsk_reliable() or 1143 arch_stack_walk_reliable() function which only returns a stack trace 1144 if it can guarantee the trace is reliable. 1145 1146config HAVE_ARCH_HASH 1147 bool 1148 default n 1149 help 1150 If this is set, the architecture provides an <asm/hash.h> 1151 file which provides platform-specific implementations of some 1152 functions in <linux/hash.h> or fs/namei.c. 1153 1154config HAVE_ARCH_NVRAM_OPS 1155 bool 1156 1157config ISA_BUS_API 1158 def_bool ISA 1159 1160# 1161# ABI hall of shame 1162# 1163config CLONE_BACKWARDS 1164 bool 1165 help 1166 Architecture has tls passed as the 4th argument of clone(2), 1167 not the 5th one. 1168 1169config CLONE_BACKWARDS2 1170 bool 1171 help 1172 Architecture has the first two arguments of clone(2) swapped. 1173 1174config CLONE_BACKWARDS3 1175 bool 1176 help 1177 Architecture has tls passed as the 3rd argument of clone(2), 1178 not the 5th one. 1179 1180config ODD_RT_SIGACTION 1181 bool 1182 help 1183 Architecture has unusual rt_sigaction(2) arguments 1184 1185config OLD_SIGSUSPEND 1186 bool 1187 help 1188 Architecture has old sigsuspend(2) syscall, of one-argument variety 1189 1190config OLD_SIGSUSPEND3 1191 bool 1192 help 1193 Even weirder antique ABI - three-argument sigsuspend(2) 1194 1195config OLD_SIGACTION 1196 bool 1197 help 1198 Architecture has old sigaction(2) syscall. Nope, not the same 1199 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1200 but fairly different variant of sigaction(2), thanks to OSF/1 1201 compatibility... 1202 1203config COMPAT_OLD_SIGACTION 1204 bool 1205 1206config COMPAT_32BIT_TIME 1207 bool "Provide system calls for 32-bit time_t" 1208 default !64BIT || COMPAT 1209 help 1210 This enables 32 bit time_t support in addition to 64 bit time_t support. 1211 This is relevant on all 32-bit architectures, and 64-bit architectures 1212 as part of compat syscall handling. 1213 1214config ARCH_NO_PREEMPT 1215 bool 1216 1217config ARCH_SUPPORTS_RT 1218 bool 1219 1220config CPU_NO_EFFICIENT_FFS 1221 def_bool n 1222 1223config HAVE_ARCH_VMAP_STACK 1224 def_bool n 1225 help 1226 An arch should select this symbol if it can support kernel stacks 1227 in vmalloc space. This means: 1228 1229 - vmalloc space must be large enough to hold many kernel stacks. 1230 This may rule out many 32-bit architectures. 1231 1232 - Stacks in vmalloc space need to work reliably. For example, if 1233 vmap page tables are created on demand, either this mechanism 1234 needs to work while the stack points to a virtual address with 1235 unpopulated page tables or arch code (switch_to() and switch_mm(), 1236 most likely) needs to ensure that the stack's page table entries 1237 are populated before running on a possibly unpopulated stack. 1238 1239 - If the stack overflows into a guard page, something reasonable 1240 should happen. The definition of "reasonable" is flexible, but 1241 instantly rebooting without logging anything would be unfriendly. 1242 1243config VMAP_STACK 1244 default y 1245 bool "Use a virtually-mapped stack" 1246 depends on HAVE_ARCH_VMAP_STACK 1247 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1248 help 1249 Enable this if you want the use virtually-mapped kernel stacks 1250 with guard pages. This causes kernel stack overflows to be 1251 caught immediately rather than causing difficult-to-diagnose 1252 corruption. 1253 1254 To use this with software KASAN modes, the architecture must support 1255 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1256 must be enabled. 1257 1258config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1259 def_bool n 1260 help 1261 An arch should select this symbol if it can support kernel stack 1262 offset randomization with calls to add_random_kstack_offset() 1263 during syscall entry and choose_random_kstack_offset() during 1264 syscall exit. Careful removal of -fstack-protector-strong and 1265 -fstack-protector should also be applied to the entry code and 1266 closely examined, as the artificial stack bump looks like an array 1267 to the compiler, so it will attempt to add canary checks regardless 1268 of the static branch state. 1269 1270config RANDOMIZE_KSTACK_OFFSET 1271 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1272 default y 1273 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1274 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1275 help 1276 The kernel stack offset can be randomized (after pt_regs) by 1277 roughly 5 bits of entropy, frustrating memory corruption 1278 attacks that depend on stack address determinism or 1279 cross-syscall address exposures. 1280 1281 The feature is controlled via the "randomize_kstack_offset=on/off" 1282 kernel boot param, and if turned off has zero overhead due to its use 1283 of static branches (see JUMP_LABEL). 1284 1285 If unsure, say Y. 1286 1287config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1288 bool "Default state of kernel stack offset randomization" 1289 depends on RANDOMIZE_KSTACK_OFFSET 1290 help 1291 Kernel stack offset randomization is controlled by kernel boot param 1292 "randomize_kstack_offset=on/off", and this config chooses the default 1293 boot state. 1294 1295config ARCH_OPTIONAL_KERNEL_RWX 1296 def_bool n 1297 1298config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1299 def_bool n 1300 1301config ARCH_HAS_STRICT_KERNEL_RWX 1302 def_bool n 1303 1304config STRICT_KERNEL_RWX 1305 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1306 depends on ARCH_HAS_STRICT_KERNEL_RWX 1307 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1308 help 1309 If this is set, kernel text and rodata memory will be made read-only, 1310 and non-text memory will be made non-executable. This provides 1311 protection against certain security exploits (e.g. executing the heap 1312 or modifying text) 1313 1314 These features are considered standard security practice these days. 1315 You should say Y here in almost all cases. 1316 1317config ARCH_HAS_STRICT_MODULE_RWX 1318 def_bool n 1319 1320config STRICT_MODULE_RWX 1321 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1322 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1323 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1324 help 1325 If this is set, module text and rodata memory will be made read-only, 1326 and non-text memory will be made non-executable. This provides 1327 protection against certain security exploits (e.g. writing to text) 1328 1329# select if the architecture provides an asm/dma-direct.h header 1330config ARCH_HAS_PHYS_TO_DMA 1331 bool 1332 1333config HAVE_ARCH_COMPILER_H 1334 bool 1335 help 1336 An architecture can select this if it provides an 1337 asm/compiler.h header that should be included after 1338 linux/compiler-*.h in order to override macro definitions that those 1339 headers generally provide. 1340 1341config HAVE_ARCH_PREL32_RELOCATIONS 1342 bool 1343 help 1344 May be selected by an architecture if it supports place-relative 1345 32-bit relocations, both in the toolchain and in the module loader, 1346 in which case relative references can be used in special sections 1347 for PCI fixup, initcalls etc which are only half the size on 64 bit 1348 architectures, and don't require runtime relocation on relocatable 1349 kernels. 1350 1351config ARCH_USE_MEMREMAP_PROT 1352 bool 1353 1354config LOCK_EVENT_COUNTS 1355 bool "Locking event counts collection" 1356 depends on DEBUG_FS 1357 help 1358 Enable light-weight counting of various locking related events 1359 in the system with minimal performance impact. This reduces 1360 the chance of application behavior change because of timing 1361 differences. The counts are reported via debugfs. 1362 1363# Select if the architecture has support for applying RELR relocations. 1364config ARCH_HAS_RELR 1365 bool 1366 1367config RELR 1368 bool "Use RELR relocation packing" 1369 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1370 default y 1371 help 1372 Store the kernel's dynamic relocations in the RELR relocation packing 1373 format. Requires a compatible linker (LLD supports this feature), as 1374 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1375 are compatible). 1376 1377config ARCH_HAS_MEM_ENCRYPT 1378 bool 1379 1380config ARCH_HAS_CC_PLATFORM 1381 bool 1382 1383config HAVE_SPARSE_SYSCALL_NR 1384 bool 1385 help 1386 An architecture should select this if its syscall numbering is sparse 1387 to save space. For example, MIPS architecture has a syscall array with 1388 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1389 related optimizations for a given architecture. 1390 1391config ARCH_HAS_VDSO_DATA 1392 bool 1393 1394config HAVE_STATIC_CALL 1395 bool 1396 1397config HAVE_STATIC_CALL_INLINE 1398 bool 1399 depends on HAVE_STATIC_CALL 1400 select OBJTOOL 1401 1402config HAVE_PREEMPT_DYNAMIC 1403 bool 1404 1405config HAVE_PREEMPT_DYNAMIC_CALL 1406 bool 1407 depends on HAVE_STATIC_CALL 1408 select HAVE_PREEMPT_DYNAMIC 1409 help 1410 An architecture should select this if it can handle the preemption 1411 model being selected at boot time using static calls. 1412 1413 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1414 preemption function will be patched directly. 1415 1416 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1417 call to a preemption function will go through a trampoline, and the 1418 trampoline will be patched. 1419 1420 It is strongly advised to support inline static call to avoid any 1421 overhead. 1422 1423config HAVE_PREEMPT_DYNAMIC_KEY 1424 bool 1425 depends on HAVE_ARCH_JUMP_LABEL 1426 select HAVE_PREEMPT_DYNAMIC 1427 help 1428 An architecture should select this if it can handle the preemption 1429 model being selected at boot time using static keys. 1430 1431 Each preemption function will be given an early return based on a 1432 static key. This should have slightly lower overhead than non-inline 1433 static calls, as this effectively inlines each trampoline into the 1434 start of its callee. This may avoid redundant work, and may 1435 integrate better with CFI schemes. 1436 1437 This will have greater overhead than using inline static calls as 1438 the call to the preemption function cannot be entirely elided. 1439 1440config ARCH_WANT_LD_ORPHAN_WARN 1441 bool 1442 help 1443 An arch should select this symbol once all linker sections are explicitly 1444 included, size-asserted, or discarded in the linker scripts. This is 1445 important because we never want expected sections to be placed heuristically 1446 by the linker, since the locations of such sections can change between linker 1447 versions. 1448 1449config HAVE_ARCH_PFN_VALID 1450 bool 1451 1452config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1453 bool 1454 1455config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1456 bool 1457 1458config ARCH_SPLIT_ARG64 1459 bool 1460 help 1461 If a 32-bit architecture requires 64-bit arguments to be split into 1462 pairs of 32-bit arguments, select this option. 1463 1464config ARCH_HAS_ELFCORE_COMPAT 1465 bool 1466 1467config ARCH_HAS_PARANOID_L1D_FLUSH 1468 bool 1469 1470config ARCH_HAVE_TRACE_MMIO_ACCESS 1471 bool 1472 1473config DYNAMIC_SIGFRAME 1474 bool 1475 1476# Select, if arch has a named attribute group bound to NUMA device nodes. 1477config HAVE_ARCH_NODE_DEV_GROUP 1478 bool 1479 1480config ARCH_HAS_NONLEAF_PMD_YOUNG 1481 bool 1482 help 1483 Architectures that select this option are capable of setting the 1484 accessed bit in non-leaf PMD entries when using them as part of linear 1485 address translations. Page table walkers that clear the accessed bit 1486 may use this capability to reduce their search space. 1487 1488source "kernel/gcov/Kconfig" 1489 1490source "scripts/gcc-plugins/Kconfig" 1491 1492config FUNCTION_ALIGNMENT_4B 1493 bool 1494 1495config FUNCTION_ALIGNMENT_8B 1496 bool 1497 1498config FUNCTION_ALIGNMENT_16B 1499 bool 1500 1501config FUNCTION_ALIGNMENT_32B 1502 bool 1503 1504config FUNCTION_ALIGNMENT_64B 1505 bool 1506 1507config FUNCTION_ALIGNMENT 1508 int 1509 default 64 if FUNCTION_ALIGNMENT_64B 1510 default 32 if FUNCTION_ALIGNMENT_32B 1511 default 16 if FUNCTION_ALIGNMENT_16B 1512 default 8 if FUNCTION_ALIGNMENT_8B 1513 default 4 if FUNCTION_ALIGNMENT_4B 1514 default 0 1515 1516endmenu 1517