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 12config ARCH_CONFIGURES_CPU_MITIGATIONS 13 bool 14 15if !ARCH_CONFIGURES_CPU_MITIGATIONS 16config CPU_MITIGATIONS 17 def_bool y 18endif 19 20menu "General architecture-dependent options" 21 22config ARCH_HAS_SUBPAGE_FAULTS 23 bool 24 help 25 Select if the architecture can check permissions at sub-page 26 granularity (e.g. arm64 MTE). The probe_user_*() functions 27 must be implemented. 28 29config HOTPLUG_SMT 30 bool 31 32config SMT_NUM_THREADS_DYNAMIC 33 bool 34 35# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 36config HOTPLUG_CORE_SYNC 37 bool 38 39# Basic CPU dead synchronization selected by architecture 40config HOTPLUG_CORE_SYNC_DEAD 41 bool 42 select HOTPLUG_CORE_SYNC 43 44# Full CPU synchronization with alive state selected by architecture 45config HOTPLUG_CORE_SYNC_FULL 46 bool 47 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 48 select HOTPLUG_CORE_SYNC 49 50config HOTPLUG_SPLIT_STARTUP 51 bool 52 select HOTPLUG_CORE_SYNC_FULL 53 54config HOTPLUG_PARALLEL 55 bool 56 select HOTPLUG_SPLIT_STARTUP 57 58config GENERIC_ENTRY 59 bool 60 61config KPROBES 62 bool "Kprobes" 63 depends on HAVE_KPROBES 64 select KALLSYMS 65 select EXECMEM 66 select NEED_TASKS_RCU 67 help 68 Kprobes allows you to trap at almost any kernel address and 69 execute a callback function. register_kprobe() establishes 70 a probepoint and specifies the callback. Kprobes is useful 71 for kernel debugging, non-intrusive instrumentation and testing. 72 If in doubt, say "N". 73 74config JUMP_LABEL 75 bool "Optimize very unlikely/likely branches" 76 depends on HAVE_ARCH_JUMP_LABEL 77 select OBJTOOL if HAVE_JUMP_LABEL_HACK 78 help 79 This option enables a transparent branch optimization that 80 makes certain almost-always-true or almost-always-false branch 81 conditions even cheaper to execute within the kernel. 82 83 Certain performance-sensitive kernel code, such as trace points, 84 scheduler functionality, networking code and KVM have such 85 branches and include support for this optimization technique. 86 87 If it is detected that the compiler has support for "asm goto", 88 the kernel will compile such branches with just a nop 89 instruction. When the condition flag is toggled to true, the 90 nop will be converted to a jump instruction to execute the 91 conditional block of instructions. 92 93 This technique lowers overhead and stress on the branch prediction 94 of the processor and generally makes the kernel faster. The update 95 of the condition is slower, but those are always very rare. 96 97 ( On 32-bit x86, the necessary options added to the compiler 98 flags may increase the size of the kernel slightly. ) 99 100config STATIC_KEYS_SELFTEST 101 bool "Static key selftest" 102 depends on JUMP_LABEL 103 help 104 Boot time self-test of the branch patching code. 105 106config STATIC_CALL_SELFTEST 107 bool "Static call selftest" 108 depends on HAVE_STATIC_CALL 109 help 110 Boot time self-test of the call patching code. 111 112config OPTPROBES 113 def_bool y 114 depends on KPROBES && HAVE_OPTPROBES 115 select NEED_TASKS_RCU 116 117config KPROBES_ON_FTRACE 118 def_bool y 119 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 120 depends on DYNAMIC_FTRACE_WITH_REGS 121 help 122 If function tracer is enabled and the arch supports full 123 passing of pt_regs to function tracing, then kprobes can 124 optimize on top of function tracing. 125 126config UPROBES 127 def_bool n 128 depends on ARCH_SUPPORTS_UPROBES 129 help 130 Uprobes is the user-space counterpart to kprobes: they 131 enable instrumentation applications (such as 'perf probe') 132 to establish unintrusive probes in user-space binaries and 133 libraries, by executing handler functions when the probes 134 are hit by user-space applications. 135 136 ( These probes come in the form of single-byte breakpoints, 137 managed by the kernel and kept transparent to the probed 138 application. ) 139 140config HAVE_64BIT_ALIGNED_ACCESS 141 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 142 help 143 Some architectures require 64 bit accesses to be 64 bit 144 aligned, which also requires structs containing 64 bit values 145 to be 64 bit aligned too. This includes some 32 bit 146 architectures which can do 64 bit accesses, as well as 64 bit 147 architectures without unaligned access. 148 149 This symbol should be selected by an architecture if 64 bit 150 accesses are required to be 64 bit aligned in this way even 151 though it is not a 64 bit architecture. 152 153 See Documentation/core-api/unaligned-memory-access.rst for 154 more information on the topic of unaligned memory accesses. 155 156config HAVE_EFFICIENT_UNALIGNED_ACCESS 157 bool 158 help 159 Some architectures are unable to perform unaligned accesses 160 without the use of get_unaligned/put_unaligned. Others are 161 unable to perform such accesses efficiently (e.g. trap on 162 unaligned access and require fixing it up in the exception 163 handler.) 164 165 This symbol should be selected by an architecture if it can 166 perform unaligned accesses efficiently to allow different 167 code paths to be selected for these cases. Some network 168 drivers, for example, could opt to not fix up alignment 169 problems with received packets if doing so would not help 170 much. 171 172 See Documentation/core-api/unaligned-memory-access.rst for more 173 information on the topic of unaligned memory accesses. 174 175config ARCH_USE_BUILTIN_BSWAP 176 bool 177 help 178 Modern versions of GCC (since 4.4) have builtin functions 179 for handling byte-swapping. Using these, instead of the old 180 inline assembler that the architecture code provides in the 181 __arch_bswapXX() macros, allows the compiler to see what's 182 happening and offers more opportunity for optimisation. In 183 particular, the compiler will be able to combine the byteswap 184 with a nearby load or store and use load-and-swap or 185 store-and-swap instructions if the architecture has them. It 186 should almost *never* result in code which is worse than the 187 hand-coded assembler in <asm/swab.h>. But just in case it 188 does, the use of the builtins is optional. 189 190 Any architecture with load-and-swap or store-and-swap 191 instructions should set this. And it shouldn't hurt to set it 192 on architectures that don't have such instructions. 193 194config KRETPROBES 195 def_bool y 196 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 197 198config KRETPROBE_ON_RETHOOK 199 def_bool y 200 depends on HAVE_RETHOOK 201 depends on KRETPROBES 202 select RETHOOK 203 204config USER_RETURN_NOTIFIER 205 bool 206 depends on HAVE_USER_RETURN_NOTIFIER 207 help 208 Provide a kernel-internal notification when a cpu is about to 209 switch to user mode. 210 211config HAVE_IOREMAP_PROT 212 bool 213 214config HAVE_KPROBES 215 bool 216 217config HAVE_KRETPROBES 218 bool 219 220config HAVE_OPTPROBES 221 bool 222 223config HAVE_KPROBES_ON_FTRACE 224 bool 225 226config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 227 bool 228 help 229 Since kretprobes modifies return address on the stack, the 230 stacktrace may see the kretprobe trampoline address instead 231 of correct one. If the architecture stacktrace code and 232 unwinder can adjust such entries, select this configuration. 233 234config HAVE_FUNCTION_ERROR_INJECTION 235 bool 236 237config HAVE_NMI 238 bool 239 240config HAVE_FUNCTION_DESCRIPTORS 241 bool 242 243config TRACE_IRQFLAGS_SUPPORT 244 bool 245 246config TRACE_IRQFLAGS_NMI_SUPPORT 247 bool 248 249# 250# An arch should select this if it provides all these things: 251# 252# task_pt_regs() in asm/processor.h or asm/ptrace.h 253# arch_has_single_step() if there is hardware single-step support 254# arch_has_block_step() if there is hardware block-step support 255# asm/syscall.h supplying asm-generic/syscall.h interface 256# linux/regset.h user_regset interfaces 257# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 258# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 259# TIF_NOTIFY_RESUME calls resume_user_mode_work() 260# 261config HAVE_ARCH_TRACEHOOK 262 bool 263 264config HAVE_DMA_CONTIGUOUS 265 bool 266 267config GENERIC_SMP_IDLE_THREAD 268 bool 269 270config GENERIC_IDLE_POLL_SETUP 271 bool 272 273config ARCH_HAS_FORTIFY_SOURCE 274 bool 275 help 276 An architecture should select this when it can successfully 277 build and run with CONFIG_FORTIFY_SOURCE. 278 279# 280# Select if the arch provides a historic keepinit alias for the retain_initrd 281# command line option 282# 283config ARCH_HAS_KEEPINITRD 284 bool 285 286# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 287config ARCH_HAS_SET_MEMORY 288 bool 289 290# Select if arch has all set_direct_map_invalid/default() functions 291config ARCH_HAS_SET_DIRECT_MAP 292 bool 293 294# 295# Select if the architecture provides the arch_dma_set_uncached symbol to 296# either provide an uncached segment alias for a DMA allocation, or 297# to remap the page tables in place. 298# 299config ARCH_HAS_DMA_SET_UNCACHED 300 bool 301 302# 303# Select if the architectures provides the arch_dma_clear_uncached symbol 304# to undo an in-place page table remap for uncached access. 305# 306config ARCH_HAS_DMA_CLEAR_UNCACHED 307 bool 308 309config ARCH_HAS_CPU_FINALIZE_INIT 310 bool 311 312# The architecture has a per-task state that includes the mm's PASID 313config ARCH_HAS_CPU_PASID 314 bool 315 select IOMMU_MM_DATA 316 317config HAVE_ARCH_THREAD_STRUCT_WHITELIST 318 bool 319 help 320 An architecture should select this to provide hardened usercopy 321 knowledge about what region of the thread_struct should be 322 whitelisted for copying to userspace. Normally this is only the 323 FPU registers. Specifically, arch_thread_struct_whitelist() 324 should be implemented. Without this, the entire thread_struct 325 field in task_struct will be left whitelisted. 326 327# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 328config ARCH_WANTS_DYNAMIC_TASK_STRUCT 329 bool 330 331config ARCH_WANTS_NO_INSTR 332 bool 333 help 334 An architecture should select this if the noinstr macro is being used on 335 functions to denote that the toolchain should avoid instrumenting such 336 functions and is required for correctness. 337 338config ARCH_32BIT_OFF_T 339 bool 340 depends on !64BIT 341 help 342 All new 32-bit architectures should have 64-bit off_t type on 343 userspace side which corresponds to the loff_t kernel type. This 344 is the requirement for modern ABIs. Some existing architectures 345 still support 32-bit off_t. This option is enabled for all such 346 architectures explicitly. 347 348# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 349config ARCH_32BIT_USTAT_F_TINODE 350 bool 351 352config HAVE_ASM_MODVERSIONS 353 bool 354 help 355 This symbol should be selected by an architecture if it provides 356 <asm/asm-prototypes.h> to support the module versioning for symbols 357 exported from assembly code. 358 359config HAVE_REGS_AND_STACK_ACCESS_API 360 bool 361 help 362 This symbol should be selected by an architecture if it supports 363 the API needed to access registers and stack entries from pt_regs, 364 declared in asm/ptrace.h 365 For example the kprobes-based event tracer needs this API. 366 367config HAVE_RSEQ 368 bool 369 depends on HAVE_REGS_AND_STACK_ACCESS_API 370 help 371 This symbol should be selected by an architecture if it 372 supports an implementation of restartable sequences. 373 374config HAVE_RUST 375 bool 376 help 377 This symbol should be selected by an architecture if it 378 supports Rust. 379 380config HAVE_FUNCTION_ARG_ACCESS_API 381 bool 382 help 383 This symbol should be selected by an architecture if it supports 384 the API needed to access function arguments from pt_regs, 385 declared in asm/ptrace.h 386 387config HAVE_HW_BREAKPOINT 388 bool 389 depends on PERF_EVENTS 390 391config HAVE_MIXED_BREAKPOINTS_REGS 392 bool 393 depends on HAVE_HW_BREAKPOINT 394 help 395 Depending on the arch implementation of hardware breakpoints, 396 some of them have separate registers for data and instruction 397 breakpoints addresses, others have mixed registers to store 398 them but define the access type in a control register. 399 Select this option if your arch implements breakpoints under the 400 latter fashion. 401 402config HAVE_USER_RETURN_NOTIFIER 403 bool 404 405config HAVE_PERF_EVENTS_NMI 406 bool 407 help 408 System hardware can generate an NMI using the perf event 409 subsystem. Also has support for calculating CPU cycle events 410 to determine how many clock cycles in a given period. 411 412config HAVE_HARDLOCKUP_DETECTOR_PERF 413 bool 414 depends on HAVE_PERF_EVENTS_NMI 415 help 416 The arch chooses to use the generic perf-NMI-based hardlockup 417 detector. Must define HAVE_PERF_EVENTS_NMI. 418 419config HAVE_HARDLOCKUP_DETECTOR_ARCH 420 bool 421 help 422 The arch provides its own hardlockup detector implementation instead 423 of the generic ones. 424 425 It uses the same command line parameters, and sysctl interface, 426 as the generic hardlockup detectors. 427 428config HAVE_PERF_REGS 429 bool 430 help 431 Support selective register dumps for perf events. This includes 432 bit-mapping of each registers and a unique architecture id. 433 434config HAVE_PERF_USER_STACK_DUMP 435 bool 436 help 437 Support user stack dumps for perf event samples. This needs 438 access to the user stack pointer which is not unified across 439 architectures. 440 441config HAVE_ARCH_JUMP_LABEL 442 bool 443 444config HAVE_ARCH_JUMP_LABEL_RELATIVE 445 bool 446 447config MMU_GATHER_TABLE_FREE 448 bool 449 450config MMU_GATHER_RCU_TABLE_FREE 451 bool 452 select MMU_GATHER_TABLE_FREE 453 454config MMU_GATHER_PAGE_SIZE 455 bool 456 457config MMU_GATHER_NO_RANGE 458 bool 459 select MMU_GATHER_MERGE_VMAS 460 461config MMU_GATHER_NO_FLUSH_CACHE 462 bool 463 464config MMU_GATHER_MERGE_VMAS 465 bool 466 467config MMU_GATHER_NO_GATHER 468 bool 469 depends on MMU_GATHER_TABLE_FREE 470 471config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 472 bool 473 help 474 Temporary select until all architectures can be converted to have 475 irqs disabled over activate_mm. Architectures that do IPI based TLB 476 shootdowns should enable this. 477 478# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 479# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 480# to/from kernel threads when the same mm is running on a lot of CPUs (a large 481# multi-threaded application), by reducing contention on the mm refcount. 482# 483# This can be disabled if the architecture ensures no CPUs are using an mm as a 484# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 485# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 486# final exit(2) TLB flush, for example. 487# 488# To implement this, an arch *must*: 489# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 490# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 491# converted already). 492config MMU_LAZY_TLB_REFCOUNT 493 def_bool y 494 depends on !MMU_LAZY_TLB_SHOOTDOWN 495 496# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 497# mm as a lazy tlb beyond its last reference count, by shooting down these 498# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 499# be using the mm as a lazy tlb, so that they may switch themselves to using 500# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 501# may be using mm as a lazy tlb mm. 502# 503# To implement this, an arch *must*: 504# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 505# at least all possible CPUs in which the mm is lazy. 506# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 507config MMU_LAZY_TLB_SHOOTDOWN 508 bool 509 510config ARCH_HAVE_NMI_SAFE_CMPXCHG 511 bool 512 513config ARCH_HAVE_EXTRA_ELF_NOTES 514 bool 515 help 516 An architecture should select this in order to enable adding an 517 arch-specific ELF note section to core files. It must provide two 518 functions: elf_coredump_extra_notes_size() and 519 elf_coredump_extra_notes_write() which are invoked by the ELF core 520 dumper. 521 522config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 523 bool 524 525config HAVE_ALIGNED_STRUCT_PAGE 526 bool 527 help 528 This makes sure that struct pages are double word aligned and that 529 e.g. the SLUB allocator can perform double word atomic operations 530 on a struct page for better performance. However selecting this 531 might increase the size of a struct page by a word. 532 533config HAVE_CMPXCHG_LOCAL 534 bool 535 536config HAVE_CMPXCHG_DOUBLE 537 bool 538 539config ARCH_WEAK_RELEASE_ACQUIRE 540 bool 541 542config ARCH_WANT_IPC_PARSE_VERSION 543 bool 544 545config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 546 bool 547 548config ARCH_WANT_OLD_COMPAT_IPC 549 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 550 bool 551 552config HAVE_ARCH_SECCOMP 553 bool 554 help 555 An arch should select this symbol to support seccomp mode 1 (the fixed 556 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 557 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 558 - __NR_seccomp_read_32 559 - __NR_seccomp_write_32 560 - __NR_seccomp_exit_32 561 - __NR_seccomp_sigreturn_32 562 563config HAVE_ARCH_SECCOMP_FILTER 564 bool 565 select HAVE_ARCH_SECCOMP 566 help 567 An arch should select this symbol if it provides all of these things: 568 - all the requirements for HAVE_ARCH_SECCOMP 569 - syscall_get_arch() 570 - syscall_get_arguments() 571 - syscall_rollback() 572 - syscall_set_return_value() 573 - SIGSYS siginfo_t support 574 - secure_computing is called from a ptrace_event()-safe context 575 - secure_computing return value is checked and a return value of -1 576 results in the system call being skipped immediately. 577 - seccomp syscall wired up 578 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 579 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 580 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 581 582config SECCOMP 583 prompt "Enable seccomp to safely execute untrusted bytecode" 584 def_bool y 585 depends on HAVE_ARCH_SECCOMP 586 help 587 This kernel feature is useful for number crunching applications 588 that may need to handle untrusted bytecode during their 589 execution. By using pipes or other transports made available 590 to the process as file descriptors supporting the read/write 591 syscalls, it's possible to isolate those applications in their 592 own address space using seccomp. Once seccomp is enabled via 593 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 594 disabled and the task is only allowed to execute a few safe 595 syscalls defined by each seccomp mode. 596 597 If unsure, say Y. 598 599config SECCOMP_FILTER 600 def_bool y 601 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 602 help 603 Enable tasks to build secure computing environments defined 604 in terms of Berkeley Packet Filter programs which implement 605 task-defined system call filtering polices. 606 607 See Documentation/userspace-api/seccomp_filter.rst for details. 608 609config SECCOMP_CACHE_DEBUG 610 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 611 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 612 depends on PROC_FS 613 help 614 This enables the /proc/pid/seccomp_cache interface to monitor 615 seccomp cache data. The file format is subject to change. Reading 616 the file requires CAP_SYS_ADMIN. 617 618 This option is for debugging only. Enabling presents the risk that 619 an adversary may be able to infer the seccomp filter logic. 620 621 If unsure, say N. 622 623config HAVE_ARCH_STACKLEAK 624 bool 625 help 626 An architecture should select this if it has the code which 627 fills the used part of the kernel stack with the STACKLEAK_POISON 628 value before returning from system calls. 629 630config HAVE_STACKPROTECTOR 631 bool 632 help 633 An arch should select this symbol if: 634 - it has implemented a stack canary (e.g. __stack_chk_guard) 635 636config STACKPROTECTOR 637 bool "Stack Protector buffer overflow detection" 638 depends on HAVE_STACKPROTECTOR 639 depends on $(cc-option,-fstack-protector) 640 default y 641 help 642 This option turns on the "stack-protector" GCC feature. This 643 feature puts, at the beginning of functions, a canary value on 644 the stack just before the return address, and validates 645 the value just before actually returning. Stack based buffer 646 overflows (that need to overwrite this return address) now also 647 overwrite the canary, which gets detected and the attack is then 648 neutralized via a kernel panic. 649 650 Functions will have the stack-protector canary logic added if they 651 have an 8-byte or larger character array on the stack. 652 653 This feature requires gcc version 4.2 or above, or a distribution 654 gcc with the feature backported ("-fstack-protector"). 655 656 On an x86 "defconfig" build, this feature adds canary checks to 657 about 3% of all kernel functions, which increases kernel code size 658 by about 0.3%. 659 660config STACKPROTECTOR_STRONG 661 bool "Strong Stack Protector" 662 depends on STACKPROTECTOR 663 depends on $(cc-option,-fstack-protector-strong) 664 default y 665 help 666 Functions will have the stack-protector canary logic added in any 667 of the following conditions: 668 669 - local variable's address used as part of the right hand side of an 670 assignment or function argument 671 - local variable is an array (or union containing an array), 672 regardless of array type or length 673 - uses register local variables 674 675 This feature requires gcc version 4.9 or above, or a distribution 676 gcc with the feature backported ("-fstack-protector-strong"). 677 678 On an x86 "defconfig" build, this feature adds canary checks to 679 about 20% of all kernel functions, which increases the kernel code 680 size by about 2%. 681 682config ARCH_SUPPORTS_SHADOW_CALL_STACK 683 bool 684 help 685 An architecture should select this if it supports the compiler's 686 Shadow Call Stack and implements runtime support for shadow stack 687 switching. 688 689config SHADOW_CALL_STACK 690 bool "Shadow Call Stack" 691 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 692 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 693 depends on MMU 694 help 695 This option enables the compiler's Shadow Call Stack, which 696 uses a shadow stack to protect function return addresses from 697 being overwritten by an attacker. More information can be found 698 in the compiler's documentation: 699 700 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 701 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 702 703 Note that security guarantees in the kernel differ from the 704 ones documented for user space. The kernel must store addresses 705 of shadow stacks in memory, which means an attacker capable of 706 reading and writing arbitrary memory may be able to locate them 707 and hijack control flow by modifying the stacks. 708 709config DYNAMIC_SCS 710 bool 711 help 712 Set by the arch code if it relies on code patching to insert the 713 shadow call stack push and pop instructions rather than on the 714 compiler. 715 716config LTO 717 bool 718 help 719 Selected if the kernel will be built using the compiler's LTO feature. 720 721config LTO_CLANG 722 bool 723 select LTO 724 help 725 Selected if the kernel will be built using Clang's LTO feature. 726 727config ARCH_SUPPORTS_LTO_CLANG 728 bool 729 help 730 An architecture should select this option if it supports: 731 - compiling with Clang, 732 - compiling inline assembly with Clang's integrated assembler, 733 - and linking with LLD. 734 735config ARCH_SUPPORTS_LTO_CLANG_THIN 736 bool 737 help 738 An architecture should select this option if it can support Clang's 739 ThinLTO mode. 740 741config HAS_LTO_CLANG 742 def_bool y 743 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 744 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 745 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 746 depends on ARCH_SUPPORTS_LTO_CLANG 747 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 748 # https://github.com/ClangBuiltLinux/linux/issues/1721 749 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 750 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 751 depends on !GCOV_KERNEL 752 help 753 The compiler and Kconfig options support building with Clang's 754 LTO. 755 756choice 757 prompt "Link Time Optimization (LTO)" 758 default LTO_NONE 759 help 760 This option enables Link Time Optimization (LTO), which allows the 761 compiler to optimize binaries globally. 762 763 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 764 so it's disabled by default. 765 766config LTO_NONE 767 bool "None" 768 help 769 Build the kernel normally, without Link Time Optimization (LTO). 770 771config LTO_CLANG_FULL 772 bool "Clang Full LTO (EXPERIMENTAL)" 773 depends on HAS_LTO_CLANG 774 depends on !COMPILE_TEST 775 select LTO_CLANG 776 help 777 This option enables Clang's full Link Time Optimization (LTO), which 778 allows the compiler to optimize the kernel globally. If you enable 779 this option, the compiler generates LLVM bitcode instead of ELF 780 object files, and the actual compilation from bitcode happens at 781 the LTO link step, which may take several minutes depending on the 782 kernel configuration. More information can be found from LLVM's 783 documentation: 784 785 https://llvm.org/docs/LinkTimeOptimization.html 786 787 During link time, this option can use a large amount of RAM, and 788 may take much longer than the ThinLTO option. 789 790config LTO_CLANG_THIN 791 bool "Clang ThinLTO (EXPERIMENTAL)" 792 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 793 select LTO_CLANG 794 help 795 This option enables Clang's ThinLTO, which allows for parallel 796 optimization and faster incremental compiles compared to the 797 CONFIG_LTO_CLANG_FULL option. More information can be found 798 from Clang's documentation: 799 800 https://clang.llvm.org/docs/ThinLTO.html 801 802 If unsure, say Y. 803endchoice 804 805config ARCH_SUPPORTS_CFI_CLANG 806 bool 807 help 808 An architecture should select this option if it can support Clang's 809 Control-Flow Integrity (CFI) checking. 810 811config ARCH_USES_CFI_TRAPS 812 bool 813 814config CFI_CLANG 815 bool "Use Clang's Control Flow Integrity (CFI)" 816 depends on ARCH_SUPPORTS_CFI_CLANG 817 depends on $(cc-option,-fsanitize=kcfi) 818 help 819 This option enables Clang's forward-edge Control Flow Integrity 820 (CFI) checking, where the compiler injects a runtime check to each 821 indirect function call to ensure the target is a valid function with 822 the correct static type. This restricts possible call targets and 823 makes it more difficult for an attacker to exploit bugs that allow 824 the modification of stored function pointers. More information can be 825 found from Clang's documentation: 826 827 https://clang.llvm.org/docs/ControlFlowIntegrity.html 828 829config CFI_PERMISSIVE 830 bool "Use CFI in permissive mode" 831 depends on CFI_CLANG 832 help 833 When selected, Control Flow Integrity (CFI) violations result in a 834 warning instead of a kernel panic. This option should only be used 835 for finding indirect call type mismatches during development. 836 837 If unsure, say N. 838 839config HAVE_ARCH_WITHIN_STACK_FRAMES 840 bool 841 help 842 An architecture should select this if it can walk the kernel stack 843 frames to determine if an object is part of either the arguments 844 or local variables (i.e. that it excludes saved return addresses, 845 and similar) by implementing an inline arch_within_stack_frames(), 846 which is used by CONFIG_HARDENED_USERCOPY. 847 848config HAVE_CONTEXT_TRACKING_USER 849 bool 850 help 851 Provide kernel/user boundaries probes necessary for subsystems 852 that need it, such as userspace RCU extended quiescent state. 853 Syscalls need to be wrapped inside user_exit()-user_enter(), either 854 optimized behind static key or through the slow path using TIF_NOHZ 855 flag. Exceptions handlers must be wrapped as well. Irqs are already 856 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 857 handling on irq exit still need to be protected. 858 859config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 860 bool 861 help 862 Architecture neither relies on exception_enter()/exception_exit() 863 nor on schedule_user(). Also preempt_schedule_notrace() and 864 preempt_schedule_irq() can't be called in a preemptible section 865 while context tracking is CONTEXT_USER. This feature reflects a sane 866 entry implementation where the following requirements are met on 867 critical entry code, ie: before user_exit() or after user_enter(): 868 869 - Critical entry code isn't preemptible (or better yet: 870 not interruptible). 871 - No use of RCU read side critical sections, unless ct_nmi_enter() 872 got called. 873 - No use of instrumentation, unless instrumentation_begin() got 874 called. 875 876config HAVE_TIF_NOHZ 877 bool 878 help 879 Arch relies on TIF_NOHZ and syscall slow path to implement context 880 tracking calls to user_enter()/user_exit(). 881 882config HAVE_VIRT_CPU_ACCOUNTING 883 bool 884 885config HAVE_VIRT_CPU_ACCOUNTING_IDLE 886 bool 887 help 888 Architecture has its own way to account idle CPU time and therefore 889 doesn't implement vtime_account_idle(). 890 891config ARCH_HAS_SCALED_CPUTIME 892 bool 893 894config HAVE_VIRT_CPU_ACCOUNTING_GEN 895 bool 896 default y if 64BIT 897 help 898 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 899 Before enabling this option, arch code must be audited 900 to ensure there are no races in concurrent read/write of 901 cputime_t. For example, reading/writing 64-bit cputime_t on 902 some 32-bit arches may require multiple accesses, so proper 903 locking is needed to protect against concurrent accesses. 904 905config HAVE_IRQ_TIME_ACCOUNTING 906 bool 907 help 908 Archs need to ensure they use a high enough resolution clock to 909 support irq time accounting and then call enable_sched_clock_irqtime(). 910 911config HAVE_MOVE_PUD 912 bool 913 help 914 Architectures that select this are able to move page tables at the 915 PUD level. If there are only 3 page table levels, the move effectively 916 happens at the PGD level. 917 918config HAVE_MOVE_PMD 919 bool 920 help 921 Archs that select this are able to move page tables at the PMD level. 922 923config HAVE_ARCH_TRANSPARENT_HUGEPAGE 924 bool 925 926config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 927 bool 928 929config HAVE_ARCH_HUGE_VMAP 930 bool 931 932# 933# Archs that select this would be capable of PMD-sized vmaps (i.e., 934# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 935# must be used to enable allocations to use hugepages. 936# 937config HAVE_ARCH_HUGE_VMALLOC 938 depends on HAVE_ARCH_HUGE_VMAP 939 bool 940 941config ARCH_WANT_HUGE_PMD_SHARE 942 bool 943 944# Archs that want to use pmd_mkwrite on kernel memory need it defined even 945# if there are no userspace memory management features that use it 946config ARCH_WANT_KERNEL_PMD_MKWRITE 947 bool 948 949config ARCH_WANT_PMD_MKWRITE 950 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 951 952config HAVE_ARCH_SOFT_DIRTY 953 bool 954 955config HAVE_MOD_ARCH_SPECIFIC 956 bool 957 help 958 The arch uses struct mod_arch_specific to store data. Many arches 959 just need a simple module loader without arch specific data - those 960 should not enable this. 961 962config MODULES_USE_ELF_RELA 963 bool 964 help 965 Modules only use ELF RELA relocations. Modules with ELF REL 966 relocations will give an error. 967 968config MODULES_USE_ELF_REL 969 bool 970 help 971 Modules only use ELF REL relocations. Modules with ELF RELA 972 relocations will give an error. 973 974config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 975 bool 976 help 977 For architectures like powerpc/32 which have constraints on module 978 allocation and need to allocate module data outside of module area. 979 980config ARCH_WANTS_EXECMEM_LATE 981 bool 982 help 983 For architectures that do not allocate executable memory early on 984 boot, but rather require its initialization late when there is 985 enough entropy for module space randomization, for instance 986 arm64. 987 988config HAVE_IRQ_EXIT_ON_IRQ_STACK 989 bool 990 help 991 Architecture doesn't only execute the irq handler on the irq stack 992 but also irq_exit(). This way we can process softirqs on this irq 993 stack instead of switching to a new one when we call __do_softirq() 994 in the end of an hardirq. 995 This spares a stack switch and improves cache usage on softirq 996 processing. 997 998config HAVE_SOFTIRQ_ON_OWN_STACK 999 bool 1000 help 1001 Architecture provides a function to run __do_softirq() on a 1002 separate stack. 1003 1004config SOFTIRQ_ON_OWN_STACK 1005 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1006 1007config ALTERNATE_USER_ADDRESS_SPACE 1008 bool 1009 help 1010 Architectures set this when the CPU uses separate address 1011 spaces for kernel and user space pointers. In this case, the 1012 access_ok() check on a __user pointer is skipped. 1013 1014config PGTABLE_LEVELS 1015 int 1016 default 2 1017 1018config ARCH_HAS_ELF_RANDOMIZE 1019 bool 1020 help 1021 An architecture supports choosing randomized locations for 1022 stack, mmap, brk, and ET_DYN. Defined functions: 1023 - arch_mmap_rnd() 1024 - arch_randomize_brk() 1025 1026config HAVE_ARCH_MMAP_RND_BITS 1027 bool 1028 help 1029 An arch should select this symbol if it supports setting a variable 1030 number of bits for use in establishing the base address for mmap 1031 allocations, has MMU enabled and provides values for both: 1032 - ARCH_MMAP_RND_BITS_MIN 1033 - ARCH_MMAP_RND_BITS_MAX 1034 1035config HAVE_EXIT_THREAD 1036 bool 1037 help 1038 An architecture implements exit_thread. 1039 1040config ARCH_MMAP_RND_BITS_MIN 1041 int 1042 1043config ARCH_MMAP_RND_BITS_MAX 1044 int 1045 1046config ARCH_MMAP_RND_BITS_DEFAULT 1047 int 1048 1049config ARCH_MMAP_RND_BITS 1050 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1051 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1052 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1053 default ARCH_MMAP_RND_BITS_MIN 1054 depends on HAVE_ARCH_MMAP_RND_BITS 1055 help 1056 This value can be used to select the number of bits to use to 1057 determine the random offset to the base address of vma regions 1058 resulting from mmap allocations. This value will be bounded 1059 by the architecture's minimum and maximum supported values. 1060 1061 This value can be changed after boot using the 1062 /proc/sys/vm/mmap_rnd_bits tunable 1063 1064config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1065 bool 1066 help 1067 An arch should select this symbol if it supports running applications 1068 in compatibility mode, supports setting a variable number of bits for 1069 use in establishing the base address for mmap allocations, has MMU 1070 enabled and provides values for both: 1071 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1072 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1073 1074config ARCH_MMAP_RND_COMPAT_BITS_MIN 1075 int 1076 1077config ARCH_MMAP_RND_COMPAT_BITS_MAX 1078 int 1079 1080config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1081 int 1082 1083config ARCH_MMAP_RND_COMPAT_BITS 1084 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1085 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1086 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1087 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1088 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1089 help 1090 This value can be used to select the number of bits to use to 1091 determine the random offset to the base address of vma regions 1092 resulting from mmap allocations for compatible applications This 1093 value will be bounded by the architecture's minimum and maximum 1094 supported values. 1095 1096 This value can be changed after boot using the 1097 /proc/sys/vm/mmap_rnd_compat_bits tunable 1098 1099config HAVE_ARCH_COMPAT_MMAP_BASES 1100 bool 1101 help 1102 This allows 64bit applications to invoke 32-bit mmap() syscall 1103 and vice-versa 32-bit applications to call 64-bit mmap(). 1104 Required for applications doing different bitness syscalls. 1105 1106config HAVE_PAGE_SIZE_4KB 1107 bool 1108 1109config HAVE_PAGE_SIZE_8KB 1110 bool 1111 1112config HAVE_PAGE_SIZE_16KB 1113 bool 1114 1115config HAVE_PAGE_SIZE_32KB 1116 bool 1117 1118config HAVE_PAGE_SIZE_64KB 1119 bool 1120 1121config HAVE_PAGE_SIZE_256KB 1122 bool 1123 1124choice 1125 prompt "MMU page size" 1126 1127config PAGE_SIZE_4KB 1128 bool "4KiB pages" 1129 depends on HAVE_PAGE_SIZE_4KB 1130 help 1131 This option select the standard 4KiB Linux page size and the only 1132 available option on many architectures. Using 4KiB page size will 1133 minimize memory consumption and is therefore recommended for low 1134 memory systems. 1135 Some software that is written for x86 systems makes incorrect 1136 assumptions about the page size and only runs on 4KiB pages. 1137 1138config PAGE_SIZE_8KB 1139 bool "8KiB pages" 1140 depends on HAVE_PAGE_SIZE_8KB 1141 help 1142 This option is the only supported page size on a few older 1143 processors, and can be slightly faster than 4KiB pages. 1144 1145config PAGE_SIZE_16KB 1146 bool "16KiB pages" 1147 depends on HAVE_PAGE_SIZE_16KB 1148 help 1149 This option is usually a good compromise between memory 1150 consumption and performance for typical desktop and server 1151 workloads, often saving a level of page table lookups compared 1152 to 4KB pages as well as reducing TLB pressure and overhead of 1153 per-page operations in the kernel at the expense of a larger 1154 page cache. 1155 1156config PAGE_SIZE_32KB 1157 bool "32KiB pages" 1158 depends on HAVE_PAGE_SIZE_32KB 1159 help 1160 Using 32KiB page size will result in slightly higher performance 1161 kernel at the price of higher memory consumption compared to 1162 16KiB pages. This option is available only on cnMIPS cores. 1163 Note that you will need a suitable Linux distribution to 1164 support this. 1165 1166config PAGE_SIZE_64KB 1167 bool "64KiB pages" 1168 depends on HAVE_PAGE_SIZE_64KB 1169 help 1170 Using 64KiB page size will result in slightly higher performance 1171 kernel at the price of much higher memory consumption compared to 1172 4KiB or 16KiB pages. 1173 This is not suitable for general-purpose workloads but the 1174 better performance may be worth the cost for certain types of 1175 supercomputing or database applications that work mostly with 1176 large in-memory data rather than small files. 1177 1178config PAGE_SIZE_256KB 1179 bool "256KiB pages" 1180 depends on HAVE_PAGE_SIZE_256KB 1181 help 1182 256KiB pages have little practical value due to their extreme 1183 memory usage. The kernel will only be able to run applications 1184 that have been compiled with '-zmax-page-size' set to 256KiB 1185 (the default is 64KiB or 4KiB on most architectures). 1186 1187endchoice 1188 1189config PAGE_SIZE_LESS_THAN_64KB 1190 def_bool y 1191 depends on !PAGE_SIZE_64KB 1192 depends on PAGE_SIZE_LESS_THAN_256KB 1193 1194config PAGE_SIZE_LESS_THAN_256KB 1195 def_bool y 1196 depends on !PAGE_SIZE_256KB 1197 1198config PAGE_SHIFT 1199 int 1200 default 12 if PAGE_SIZE_4KB 1201 default 13 if PAGE_SIZE_8KB 1202 default 14 if PAGE_SIZE_16KB 1203 default 15 if PAGE_SIZE_32KB 1204 default 16 if PAGE_SIZE_64KB 1205 default 18 if PAGE_SIZE_256KB 1206 1207# This allows to use a set of generic functions to determine mmap base 1208# address by giving priority to top-down scheme only if the process 1209# is not in legacy mode (compat task, unlimited stack size or 1210# sysctl_legacy_va_layout). 1211# Architecture that selects this option can provide its own version of: 1212# - STACK_RND_MASK 1213config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1214 bool 1215 depends on MMU 1216 select ARCH_HAS_ELF_RANDOMIZE 1217 1218config HAVE_OBJTOOL 1219 bool 1220 1221config HAVE_JUMP_LABEL_HACK 1222 bool 1223 1224config HAVE_NOINSTR_HACK 1225 bool 1226 1227config HAVE_NOINSTR_VALIDATION 1228 bool 1229 1230config HAVE_UACCESS_VALIDATION 1231 bool 1232 select OBJTOOL 1233 1234config HAVE_STACK_VALIDATION 1235 bool 1236 help 1237 Architecture supports objtool compile-time frame pointer rule 1238 validation. 1239 1240config HAVE_RELIABLE_STACKTRACE 1241 bool 1242 help 1243 Architecture has either save_stack_trace_tsk_reliable() or 1244 arch_stack_walk_reliable() function which only returns a stack trace 1245 if it can guarantee the trace is reliable. 1246 1247config HAVE_ARCH_HASH 1248 bool 1249 default n 1250 help 1251 If this is set, the architecture provides an <asm/hash.h> 1252 file which provides platform-specific implementations of some 1253 functions in <linux/hash.h> or fs/namei.c. 1254 1255config HAVE_ARCH_NVRAM_OPS 1256 bool 1257 1258config ISA_BUS_API 1259 def_bool ISA 1260 1261# 1262# ABI hall of shame 1263# 1264config CLONE_BACKWARDS 1265 bool 1266 help 1267 Architecture has tls passed as the 4th argument of clone(2), 1268 not the 5th one. 1269 1270config CLONE_BACKWARDS2 1271 bool 1272 help 1273 Architecture has the first two arguments of clone(2) swapped. 1274 1275config CLONE_BACKWARDS3 1276 bool 1277 help 1278 Architecture has tls passed as the 3rd argument of clone(2), 1279 not the 5th one. 1280 1281config ODD_RT_SIGACTION 1282 bool 1283 help 1284 Architecture has unusual rt_sigaction(2) arguments 1285 1286config OLD_SIGSUSPEND 1287 bool 1288 help 1289 Architecture has old sigsuspend(2) syscall, of one-argument variety 1290 1291config OLD_SIGSUSPEND3 1292 bool 1293 help 1294 Even weirder antique ABI - three-argument sigsuspend(2) 1295 1296config OLD_SIGACTION 1297 bool 1298 help 1299 Architecture has old sigaction(2) syscall. Nope, not the same 1300 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1301 but fairly different variant of sigaction(2), thanks to OSF/1 1302 compatibility... 1303 1304config COMPAT_OLD_SIGACTION 1305 bool 1306 1307config COMPAT_32BIT_TIME 1308 bool "Provide system calls for 32-bit time_t" 1309 default !64BIT || COMPAT 1310 help 1311 This enables 32 bit time_t support in addition to 64 bit time_t support. 1312 This is relevant on all 32-bit architectures, and 64-bit architectures 1313 as part of compat syscall handling. 1314 1315config ARCH_NO_PREEMPT 1316 bool 1317 1318config ARCH_SUPPORTS_RT 1319 bool 1320 1321config CPU_NO_EFFICIENT_FFS 1322 def_bool n 1323 1324config HAVE_ARCH_VMAP_STACK 1325 def_bool n 1326 help 1327 An arch should select this symbol if it can support kernel stacks 1328 in vmalloc space. This means: 1329 1330 - vmalloc space must be large enough to hold many kernel stacks. 1331 This may rule out many 32-bit architectures. 1332 1333 - Stacks in vmalloc space need to work reliably. For example, if 1334 vmap page tables are created on demand, either this mechanism 1335 needs to work while the stack points to a virtual address with 1336 unpopulated page tables or arch code (switch_to() and switch_mm(), 1337 most likely) needs to ensure that the stack's page table entries 1338 are populated before running on a possibly unpopulated stack. 1339 1340 - If the stack overflows into a guard page, something reasonable 1341 should happen. The definition of "reasonable" is flexible, but 1342 instantly rebooting without logging anything would be unfriendly. 1343 1344config VMAP_STACK 1345 default y 1346 bool "Use a virtually-mapped stack" 1347 depends on HAVE_ARCH_VMAP_STACK 1348 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1349 help 1350 Enable this if you want the use virtually-mapped kernel stacks 1351 with guard pages. This causes kernel stack overflows to be 1352 caught immediately rather than causing difficult-to-diagnose 1353 corruption. 1354 1355 To use this with software KASAN modes, the architecture must support 1356 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1357 must be enabled. 1358 1359config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1360 def_bool n 1361 help 1362 An arch should select this symbol if it can support kernel stack 1363 offset randomization with calls to add_random_kstack_offset() 1364 during syscall entry and choose_random_kstack_offset() during 1365 syscall exit. Careful removal of -fstack-protector-strong and 1366 -fstack-protector should also be applied to the entry code and 1367 closely examined, as the artificial stack bump looks like an array 1368 to the compiler, so it will attempt to add canary checks regardless 1369 of the static branch state. 1370 1371config RANDOMIZE_KSTACK_OFFSET 1372 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1373 default y 1374 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1375 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1376 help 1377 The kernel stack offset can be randomized (after pt_regs) by 1378 roughly 5 bits of entropy, frustrating memory corruption 1379 attacks that depend on stack address determinism or 1380 cross-syscall address exposures. 1381 1382 The feature is controlled via the "randomize_kstack_offset=on/off" 1383 kernel boot param, and if turned off has zero overhead due to its use 1384 of static branches (see JUMP_LABEL). 1385 1386 If unsure, say Y. 1387 1388config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1389 bool "Default state of kernel stack offset randomization" 1390 depends on RANDOMIZE_KSTACK_OFFSET 1391 help 1392 Kernel stack offset randomization is controlled by kernel boot param 1393 "randomize_kstack_offset=on/off", and this config chooses the default 1394 boot state. 1395 1396config ARCH_OPTIONAL_KERNEL_RWX 1397 def_bool n 1398 1399config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1400 def_bool n 1401 1402config ARCH_HAS_STRICT_KERNEL_RWX 1403 def_bool n 1404 1405config STRICT_KERNEL_RWX 1406 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1407 depends on ARCH_HAS_STRICT_KERNEL_RWX 1408 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1409 help 1410 If this is set, kernel text and rodata memory will be made read-only, 1411 and non-text memory will be made non-executable. This provides 1412 protection against certain security exploits (e.g. executing the heap 1413 or modifying text) 1414 1415 These features are considered standard security practice these days. 1416 You should say Y here in almost all cases. 1417 1418config ARCH_HAS_STRICT_MODULE_RWX 1419 def_bool n 1420 1421config STRICT_MODULE_RWX 1422 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1423 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1424 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1425 help 1426 If this is set, module text and rodata memory will be made read-only, 1427 and non-text memory will be made non-executable. This provides 1428 protection against certain security exploits (e.g. writing to text) 1429 1430# select if the architecture provides an asm/dma-direct.h header 1431config ARCH_HAS_PHYS_TO_DMA 1432 bool 1433 1434config HAVE_ARCH_COMPILER_H 1435 bool 1436 help 1437 An architecture can select this if it provides an 1438 asm/compiler.h header that should be included after 1439 linux/compiler-*.h in order to override macro definitions that those 1440 headers generally provide. 1441 1442config HAVE_ARCH_PREL32_RELOCATIONS 1443 bool 1444 help 1445 May be selected by an architecture if it supports place-relative 1446 32-bit relocations, both in the toolchain and in the module loader, 1447 in which case relative references can be used in special sections 1448 for PCI fixup, initcalls etc which are only half the size on 64 bit 1449 architectures, and don't require runtime relocation on relocatable 1450 kernels. 1451 1452config ARCH_USE_MEMREMAP_PROT 1453 bool 1454 1455config LOCK_EVENT_COUNTS 1456 bool "Locking event counts collection" 1457 depends on DEBUG_FS 1458 help 1459 Enable light-weight counting of various locking related events 1460 in the system with minimal performance impact. This reduces 1461 the chance of application behavior change because of timing 1462 differences. The counts are reported via debugfs. 1463 1464# Select if the architecture has support for applying RELR relocations. 1465config ARCH_HAS_RELR 1466 bool 1467 1468config RELR 1469 bool "Use RELR relocation packing" 1470 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1471 default y 1472 help 1473 Store the kernel's dynamic relocations in the RELR relocation packing 1474 format. Requires a compatible linker (LLD supports this feature), as 1475 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1476 are compatible). 1477 1478config ARCH_HAS_MEM_ENCRYPT 1479 bool 1480 1481config ARCH_HAS_CC_PLATFORM 1482 bool 1483 1484config HAVE_SPARSE_SYSCALL_NR 1485 bool 1486 help 1487 An architecture should select this if its syscall numbering is sparse 1488 to save space. For example, MIPS architecture has a syscall array with 1489 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1490 related optimizations for a given architecture. 1491 1492config ARCH_HAS_VDSO_DATA 1493 bool 1494 1495config HAVE_STATIC_CALL 1496 bool 1497 1498config HAVE_STATIC_CALL_INLINE 1499 bool 1500 depends on HAVE_STATIC_CALL 1501 select OBJTOOL 1502 1503config HAVE_PREEMPT_DYNAMIC 1504 bool 1505 1506config HAVE_PREEMPT_DYNAMIC_CALL 1507 bool 1508 depends on HAVE_STATIC_CALL 1509 select HAVE_PREEMPT_DYNAMIC 1510 help 1511 An architecture should select this if it can handle the preemption 1512 model being selected at boot time using static calls. 1513 1514 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1515 preemption function will be patched directly. 1516 1517 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1518 call to a preemption function will go through a trampoline, and the 1519 trampoline will be patched. 1520 1521 It is strongly advised to support inline static call to avoid any 1522 overhead. 1523 1524config HAVE_PREEMPT_DYNAMIC_KEY 1525 bool 1526 depends on HAVE_ARCH_JUMP_LABEL 1527 select HAVE_PREEMPT_DYNAMIC 1528 help 1529 An architecture should select this if it can handle the preemption 1530 model being selected at boot time using static keys. 1531 1532 Each preemption function will be given an early return based on a 1533 static key. This should have slightly lower overhead than non-inline 1534 static calls, as this effectively inlines each trampoline into the 1535 start of its callee. This may avoid redundant work, and may 1536 integrate better with CFI schemes. 1537 1538 This will have greater overhead than using inline static calls as 1539 the call to the preemption function cannot be entirely elided. 1540 1541config ARCH_WANT_LD_ORPHAN_WARN 1542 bool 1543 help 1544 An arch should select this symbol once all linker sections are explicitly 1545 included, size-asserted, or discarded in the linker scripts. This is 1546 important because we never want expected sections to be placed heuristically 1547 by the linker, since the locations of such sections can change between linker 1548 versions. 1549 1550config HAVE_ARCH_PFN_VALID 1551 bool 1552 1553config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1554 bool 1555 1556config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1557 bool 1558 1559config ARCH_SPLIT_ARG64 1560 bool 1561 help 1562 If a 32-bit architecture requires 64-bit arguments to be split into 1563 pairs of 32-bit arguments, select this option. 1564 1565config ARCH_HAS_ELFCORE_COMPAT 1566 bool 1567 1568config ARCH_HAS_PARANOID_L1D_FLUSH 1569 bool 1570 1571config ARCH_HAVE_TRACE_MMIO_ACCESS 1572 bool 1573 1574config DYNAMIC_SIGFRAME 1575 bool 1576 1577# Select, if arch has a named attribute group bound to NUMA device nodes. 1578config HAVE_ARCH_NODE_DEV_GROUP 1579 bool 1580 1581config ARCH_HAS_HW_PTE_YOUNG 1582 bool 1583 help 1584 Architectures that select this option are capable of setting the 1585 accessed bit in PTE entries when using them as part of linear address 1586 translations. Architectures that require runtime check should select 1587 this option and override arch_has_hw_pte_young(). 1588 1589config ARCH_HAS_NONLEAF_PMD_YOUNG 1590 bool 1591 help 1592 Architectures that select this option are capable of setting the 1593 accessed bit in non-leaf PMD entries when using them as part of linear 1594 address translations. Page table walkers that clear the accessed bit 1595 may use this capability to reduce their search space. 1596 1597source "kernel/gcov/Kconfig" 1598 1599source "scripts/gcc-plugins/Kconfig" 1600 1601config FUNCTION_ALIGNMENT_4B 1602 bool 1603 1604config FUNCTION_ALIGNMENT_8B 1605 bool 1606 1607config FUNCTION_ALIGNMENT_16B 1608 bool 1609 1610config FUNCTION_ALIGNMENT_32B 1611 bool 1612 1613config FUNCTION_ALIGNMENT_64B 1614 bool 1615 1616config FUNCTION_ALIGNMENT 1617 int 1618 default 64 if FUNCTION_ALIGNMENT_64B 1619 default 32 if FUNCTION_ALIGNMENT_32B 1620 default 16 if FUNCTION_ALIGNMENT_16B 1621 default 8 if FUNCTION_ALIGNMENT_8B 1622 default 4 if FUNCTION_ALIGNMENT_4B 1623 default 0 1624 1625config CC_HAS_MIN_FUNCTION_ALIGNMENT 1626 # Detect availability of the GCC option -fmin-function-alignment which 1627 # guarantees minimal alignment for all functions, unlike 1628 # -falign-functions which the compiler ignores for cold functions. 1629 def_bool $(cc-option, -fmin-function-alignment=8) 1630 1631config CC_HAS_SANE_FUNCTION_ALIGNMENT 1632 # Set if the guaranteed alignment with -fmin-function-alignment is 1633 # available or extra care is required in the kernel. Clang provides 1634 # strict alignment always, even with -falign-functions. 1635 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1636 1637config ARCH_NEED_CMPXCHG_1_EMU 1638 bool 1639 1640endmenu 1641