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 20# 21# Selected by architectures that need custom DMA operations for e.g. legacy 22# IOMMUs not handled by dma-iommu. Drivers must never select this symbol. 23# 24config ARCH_HAS_DMA_OPS 25 depends on HAS_DMA 26 select DMA_OPS_HELPERS 27 bool 28 29menu "General architecture-dependent options" 30 31config ARCH_HAS_SUBPAGE_FAULTS 32 bool 33 help 34 Select if the architecture can check permissions at sub-page 35 granularity (e.g. arm64 MTE). The probe_user_*() functions 36 must be implemented. 37 38config HOTPLUG_SMT 39 bool 40 41config SMT_NUM_THREADS_DYNAMIC 42 bool 43 44# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 45config HOTPLUG_CORE_SYNC 46 bool 47 48# Basic CPU dead synchronization selected by architecture 49config HOTPLUG_CORE_SYNC_DEAD 50 bool 51 select HOTPLUG_CORE_SYNC 52 53# Full CPU synchronization with alive state selected by architecture 54config HOTPLUG_CORE_SYNC_FULL 55 bool 56 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 57 select HOTPLUG_CORE_SYNC 58 59config HOTPLUG_SPLIT_STARTUP 60 bool 61 select HOTPLUG_CORE_SYNC_FULL 62 63config HOTPLUG_PARALLEL 64 bool 65 select HOTPLUG_SPLIT_STARTUP 66 67config GENERIC_ENTRY 68 bool 69 70config KPROBES 71 bool "Kprobes" 72 depends on HAVE_KPROBES 73 select KALLSYMS 74 select EXECMEM 75 select NEED_TASKS_RCU 76 help 77 Kprobes allows you to trap at almost any kernel address and 78 execute a callback function. register_kprobe() establishes 79 a probepoint and specifies the callback. Kprobes is useful 80 for kernel debugging, non-intrusive instrumentation and testing. 81 If in doubt, say "N". 82 83config JUMP_LABEL 84 bool "Optimize very unlikely/likely branches" 85 depends on HAVE_ARCH_JUMP_LABEL 86 select OBJTOOL if HAVE_JUMP_LABEL_HACK 87 help 88 This option enables a transparent branch optimization that 89 makes certain almost-always-true or almost-always-false branch 90 conditions even cheaper to execute within the kernel. 91 92 Certain performance-sensitive kernel code, such as trace points, 93 scheduler functionality, networking code and KVM have such 94 branches and include support for this optimization technique. 95 96 If it is detected that the compiler has support for "asm goto", 97 the kernel will compile such branches with just a nop 98 instruction. When the condition flag is toggled to true, the 99 nop will be converted to a jump instruction to execute the 100 conditional block of instructions. 101 102 This technique lowers overhead and stress on the branch prediction 103 of the processor and generally makes the kernel faster. The update 104 of the condition is slower, but those are always very rare. 105 106 ( On 32-bit x86, the necessary options added to the compiler 107 flags may increase the size of the kernel slightly. ) 108 109config STATIC_KEYS_SELFTEST 110 bool "Static key selftest" 111 depends on JUMP_LABEL 112 help 113 Boot time self-test of the branch patching code. 114 115config STATIC_CALL_SELFTEST 116 bool "Static call selftest" 117 depends on HAVE_STATIC_CALL 118 help 119 Boot time self-test of the call patching code. 120 121config OPTPROBES 122 def_bool y 123 depends on KPROBES && HAVE_OPTPROBES 124 select NEED_TASKS_RCU 125 126config KPROBES_ON_FTRACE 127 def_bool y 128 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 129 depends on DYNAMIC_FTRACE_WITH_REGS 130 help 131 If function tracer is enabled and the arch supports full 132 passing of pt_regs to function tracing, then kprobes can 133 optimize on top of function tracing. 134 135config UPROBES 136 def_bool n 137 depends on ARCH_SUPPORTS_UPROBES 138 select TASKS_TRACE_RCU 139 help 140 Uprobes is the user-space counterpart to kprobes: they 141 enable instrumentation applications (such as 'perf probe') 142 to establish unintrusive probes in user-space binaries and 143 libraries, by executing handler functions when the probes 144 are hit by user-space applications. 145 146 ( These probes come in the form of single-byte breakpoints, 147 managed by the kernel and kept transparent to the probed 148 application. ) 149 150config HAVE_64BIT_ALIGNED_ACCESS 151 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 152 help 153 Some architectures require 64 bit accesses to be 64 bit 154 aligned, which also requires structs containing 64 bit values 155 to be 64 bit aligned too. This includes some 32 bit 156 architectures which can do 64 bit accesses, as well as 64 bit 157 architectures without unaligned access. 158 159 This symbol should be selected by an architecture if 64 bit 160 accesses are required to be 64 bit aligned in this way even 161 though it is not a 64 bit architecture. 162 163 See Documentation/core-api/unaligned-memory-access.rst for 164 more information on the topic of unaligned memory accesses. 165 166config HAVE_EFFICIENT_UNALIGNED_ACCESS 167 bool 168 help 169 Some architectures are unable to perform unaligned accesses 170 without the use of get_unaligned/put_unaligned. Others are 171 unable to perform such accesses efficiently (e.g. trap on 172 unaligned access and require fixing it up in the exception 173 handler.) 174 175 This symbol should be selected by an architecture if it can 176 perform unaligned accesses efficiently to allow different 177 code paths to be selected for these cases. Some network 178 drivers, for example, could opt to not fix up alignment 179 problems with received packets if doing so would not help 180 much. 181 182 See Documentation/core-api/unaligned-memory-access.rst for more 183 information on the topic of unaligned memory accesses. 184 185config ARCH_USE_BUILTIN_BSWAP 186 bool 187 help 188 Modern versions of GCC (since 4.4) have builtin functions 189 for handling byte-swapping. Using these, instead of the old 190 inline assembler that the architecture code provides in the 191 __arch_bswapXX() macros, allows the compiler to see what's 192 happening and offers more opportunity for optimisation. In 193 particular, the compiler will be able to combine the byteswap 194 with a nearby load or store and use load-and-swap or 195 store-and-swap instructions if the architecture has them. It 196 should almost *never* result in code which is worse than the 197 hand-coded assembler in <asm/swab.h>. But just in case it 198 does, the use of the builtins is optional. 199 200 Any architecture with load-and-swap or store-and-swap 201 instructions should set this. And it shouldn't hurt to set it 202 on architectures that don't have such instructions. 203 204config KRETPROBES 205 def_bool y 206 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 207 208config KRETPROBE_ON_RETHOOK 209 def_bool y 210 depends on HAVE_RETHOOK 211 depends on KRETPROBES 212 select RETHOOK 213 214config USER_RETURN_NOTIFIER 215 bool 216 depends on HAVE_USER_RETURN_NOTIFIER 217 help 218 Provide a kernel-internal notification when a cpu is about to 219 switch to user mode. 220 221config HAVE_IOREMAP_PROT 222 bool 223 224config HAVE_KPROBES 225 bool 226 227config HAVE_KRETPROBES 228 bool 229 230config HAVE_OPTPROBES 231 bool 232 233config HAVE_KPROBES_ON_FTRACE 234 bool 235 236config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 237 bool 238 help 239 Since kretprobes modifies return address on the stack, the 240 stacktrace may see the kretprobe trampoline address instead 241 of correct one. If the architecture stacktrace code and 242 unwinder can adjust such entries, select this configuration. 243 244config HAVE_FUNCTION_ERROR_INJECTION 245 bool 246 247config HAVE_NMI 248 bool 249 250config HAVE_FUNCTION_DESCRIPTORS 251 bool 252 253config TRACE_IRQFLAGS_SUPPORT 254 bool 255 256config TRACE_IRQFLAGS_NMI_SUPPORT 257 bool 258 259# 260# An arch should select this if it provides all these things: 261# 262# task_pt_regs() in asm/processor.h or asm/ptrace.h 263# arch_has_single_step() if there is hardware single-step support 264# arch_has_block_step() if there is hardware block-step support 265# asm/syscall.h supplying asm-generic/syscall.h interface 266# linux/regset.h user_regset interfaces 267# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 268# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 269# TIF_NOTIFY_RESUME calls resume_user_mode_work() 270# 271config HAVE_ARCH_TRACEHOOK 272 bool 273 274config HAVE_DMA_CONTIGUOUS 275 bool 276 277config GENERIC_SMP_IDLE_THREAD 278 bool 279 280config GENERIC_IDLE_POLL_SETUP 281 bool 282 283config ARCH_HAS_FORTIFY_SOURCE 284 bool 285 help 286 An architecture should select this when it can successfully 287 build and run with CONFIG_FORTIFY_SOURCE. 288 289# 290# Select if the arch provides a historic keepinit alias for the retain_initrd 291# command line option 292# 293config ARCH_HAS_KEEPINITRD 294 bool 295 296# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 297config ARCH_HAS_SET_MEMORY 298 bool 299 300# Select if arch has all set_direct_map_invalid/default() functions 301config ARCH_HAS_SET_DIRECT_MAP 302 bool 303 304# 305# Select if the architecture provides the arch_dma_set_uncached symbol to 306# either provide an uncached segment alias for a DMA allocation, or 307# to remap the page tables in place. 308# 309config ARCH_HAS_DMA_SET_UNCACHED 310 bool 311 312# 313# Select if the architectures provides the arch_dma_clear_uncached symbol 314# to undo an in-place page table remap for uncached access. 315# 316config ARCH_HAS_DMA_CLEAR_UNCACHED 317 bool 318 319config ARCH_HAS_CPU_FINALIZE_INIT 320 bool 321 322# The architecture has a per-task state that includes the mm's PASID 323config ARCH_HAS_CPU_PASID 324 bool 325 select IOMMU_MM_DATA 326 327config HAVE_ARCH_THREAD_STRUCT_WHITELIST 328 bool 329 help 330 An architecture should select this to provide hardened usercopy 331 knowledge about what region of the thread_struct should be 332 whitelisted for copying to userspace. Normally this is only the 333 FPU registers. Specifically, arch_thread_struct_whitelist() 334 should be implemented. Without this, the entire thread_struct 335 field in task_struct will be left whitelisted. 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_HARDLOCKUP_DETECTOR_ARCH 430 bool 431 help 432 The arch provides its own hardlockup detector implementation instead 433 of the generic ones. 434 435 It uses the same command line parameters, and sysctl interface, 436 as the generic hardlockup detectors. 437 438config UNWIND_USER 439 bool 440 441config HAVE_UNWIND_USER_FP 442 bool 443 select UNWIND_USER 444 445config HAVE_PERF_REGS 446 bool 447 help 448 Support selective register dumps for perf events. This includes 449 bit-mapping of each registers and a unique architecture id. 450 451config HAVE_PERF_USER_STACK_DUMP 452 bool 453 help 454 Support user stack dumps for perf event samples. This needs 455 access to the user stack pointer which is not unified across 456 architectures. 457 458config HAVE_ARCH_JUMP_LABEL 459 bool 460 461config HAVE_ARCH_JUMP_LABEL_RELATIVE 462 bool 463 464config MMU_GATHER_TABLE_FREE 465 bool 466 467config MMU_GATHER_RCU_TABLE_FREE 468 bool 469 select MMU_GATHER_TABLE_FREE 470 471config MMU_GATHER_PAGE_SIZE 472 bool 473 474config MMU_GATHER_NO_RANGE 475 bool 476 select MMU_GATHER_MERGE_VMAS 477 478config MMU_GATHER_NO_FLUSH_CACHE 479 bool 480 481config MMU_GATHER_MERGE_VMAS 482 bool 483 484config MMU_GATHER_NO_GATHER 485 bool 486 depends on MMU_GATHER_TABLE_FREE 487 488config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 489 bool 490 help 491 Temporary select until all architectures can be converted to have 492 irqs disabled over activate_mm. Architectures that do IPI based TLB 493 shootdowns should enable this. 494 495# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 496# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 497# to/from kernel threads when the same mm is running on a lot of CPUs (a large 498# multi-threaded application), by reducing contention on the mm refcount. 499# 500# This can be disabled if the architecture ensures no CPUs are using an mm as a 501# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 502# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 503# final exit(2) TLB flush, for example. 504# 505# To implement this, an arch *must*: 506# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 507# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 508# converted already). 509config MMU_LAZY_TLB_REFCOUNT 510 def_bool y 511 depends on !MMU_LAZY_TLB_SHOOTDOWN 512 513# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 514# mm as a lazy tlb beyond its last reference count, by shooting down these 515# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 516# be using the mm as a lazy tlb, so that they may switch themselves to using 517# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 518# may be using mm as a lazy tlb mm. 519# 520# To implement this, an arch *must*: 521# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 522# at least all possible CPUs in which the mm is lazy. 523# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 524config MMU_LAZY_TLB_SHOOTDOWN 525 bool 526 527config ARCH_HAVE_NMI_SAFE_CMPXCHG 528 bool 529 530config ARCH_HAVE_EXTRA_ELF_NOTES 531 bool 532 help 533 An architecture should select this in order to enable adding an 534 arch-specific ELF note section to core files. It must provide two 535 functions: elf_coredump_extra_notes_size() and 536 elf_coredump_extra_notes_write() which are invoked by the ELF core 537 dumper. 538 539config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 540 bool 541 542config HAVE_ALIGNED_STRUCT_PAGE 543 bool 544 help 545 This makes sure that struct pages are double word aligned and that 546 e.g. the SLUB allocator can perform double word atomic operations 547 on a struct page for better performance. However selecting this 548 might increase the size of a struct page by a word. 549 550config HAVE_CMPXCHG_LOCAL 551 bool 552 553config HAVE_CMPXCHG_DOUBLE 554 bool 555 556config ARCH_WEAK_RELEASE_ACQUIRE 557 bool 558 559config ARCH_WANT_IPC_PARSE_VERSION 560 bool 561 562config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 563 bool 564 565config ARCH_WANT_OLD_COMPAT_IPC 566 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 567 bool 568 569config HAVE_ARCH_SECCOMP 570 bool 571 help 572 An arch should select this symbol to support seccomp mode 1 (the fixed 573 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 574 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 575 - __NR_seccomp_read_32 576 - __NR_seccomp_write_32 577 - __NR_seccomp_exit_32 578 - __NR_seccomp_sigreturn_32 579 580config HAVE_ARCH_SECCOMP_FILTER 581 bool 582 select HAVE_ARCH_SECCOMP 583 help 584 An arch should select this symbol if it provides all of these things: 585 - all the requirements for HAVE_ARCH_SECCOMP 586 - syscall_get_arch() 587 - syscall_get_arguments() 588 - syscall_rollback() 589 - syscall_set_return_value() 590 - SIGSYS siginfo_t support 591 - secure_computing is called from a ptrace_event()-safe context 592 - secure_computing return value is checked and a return value of -1 593 results in the system call being skipped immediately. 594 - seccomp syscall wired up 595 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 596 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 597 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 598 599config SECCOMP 600 prompt "Enable seccomp to safely execute untrusted bytecode" 601 def_bool y 602 depends on HAVE_ARCH_SECCOMP 603 help 604 This kernel feature is useful for number crunching applications 605 that may need to handle untrusted bytecode during their 606 execution. By using pipes or other transports made available 607 to the process as file descriptors supporting the read/write 608 syscalls, it's possible to isolate those applications in their 609 own address space using seccomp. Once seccomp is enabled via 610 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 611 disabled and the task is only allowed to execute a few safe 612 syscalls defined by each seccomp mode. 613 614 If unsure, say Y. 615 616config SECCOMP_FILTER 617 def_bool y 618 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 619 help 620 Enable tasks to build secure computing environments defined 621 in terms of Berkeley Packet Filter programs which implement 622 task-defined system call filtering polices. 623 624 See Documentation/userspace-api/seccomp_filter.rst for details. 625 626config SECCOMP_CACHE_DEBUG 627 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 628 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 629 depends on PROC_FS 630 help 631 This enables the /proc/pid/seccomp_cache interface to monitor 632 seccomp cache data. The file format is subject to change. Reading 633 the file requires CAP_SYS_ADMIN. 634 635 This option is for debugging only. Enabling presents the risk that 636 an adversary may be able to infer the seccomp filter logic. 637 638 If unsure, say N. 639 640config HAVE_ARCH_STACKLEAK 641 bool 642 help 643 An architecture should select this if it has the code which 644 fills the used part of the kernel stack with the STACKLEAK_POISON 645 value before returning from system calls. 646 647config HAVE_STACKPROTECTOR 648 bool 649 help 650 An arch should select this symbol if: 651 - it has implemented a stack canary (e.g. __stack_chk_guard) 652 653config STACKPROTECTOR 654 bool "Stack Protector buffer overflow detection" 655 depends on HAVE_STACKPROTECTOR 656 depends on $(cc-option,-fstack-protector) 657 default y 658 help 659 This option turns on the "stack-protector" GCC feature. This 660 feature puts, at the beginning of functions, a canary value on 661 the stack just before the return address, and validates 662 the value just before actually returning. Stack based buffer 663 overflows (that need to overwrite this return address) now also 664 overwrite the canary, which gets detected and the attack is then 665 neutralized via a kernel panic. 666 667 Functions will have the stack-protector canary logic added if they 668 have an 8-byte or larger character array on the stack. 669 670 This feature requires gcc version 4.2 or above, or a distribution 671 gcc with the feature backported ("-fstack-protector"). 672 673 On an x86 "defconfig" build, this feature adds canary checks to 674 about 3% of all kernel functions, which increases kernel code size 675 by about 0.3%. 676 677config STACKPROTECTOR_STRONG 678 bool "Strong Stack Protector" 679 depends on STACKPROTECTOR 680 depends on $(cc-option,-fstack-protector-strong) 681 default y 682 help 683 Functions will have the stack-protector canary logic added in any 684 of the following conditions: 685 686 - local variable's address used as part of the right hand side of an 687 assignment or function argument 688 - local variable is an array (or union containing an array), 689 regardless of array type or length 690 - uses register local variables 691 692 This feature requires gcc version 4.9 or above, or a distribution 693 gcc with the feature backported ("-fstack-protector-strong"). 694 695 On an x86 "defconfig" build, this feature adds canary checks to 696 about 20% of all kernel functions, which increases the kernel code 697 size by about 2%. 698 699config ARCH_SUPPORTS_SHADOW_CALL_STACK 700 bool 701 help 702 An architecture should select this if it supports the compiler's 703 Shadow Call Stack and implements runtime support for shadow stack 704 switching. 705 706config SHADOW_CALL_STACK 707 bool "Shadow Call Stack" 708 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 709 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 710 depends on MMU 711 help 712 This option enables the compiler's Shadow Call Stack, which 713 uses a shadow stack to protect function return addresses from 714 being overwritten by an attacker. More information can be found 715 in the compiler's documentation: 716 717 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 718 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 719 720 Note that security guarantees in the kernel differ from the 721 ones documented for user space. The kernel must store addresses 722 of shadow stacks in memory, which means an attacker capable of 723 reading and writing arbitrary memory may be able to locate them 724 and hijack control flow by modifying the stacks. 725 726config DYNAMIC_SCS 727 bool 728 help 729 Set by the arch code if it relies on code patching to insert the 730 shadow call stack push and pop instructions rather than on the 731 compiler. 732 733config LTO 734 bool 735 help 736 Selected if the kernel will be built using the compiler's LTO feature. 737 738config LTO_CLANG 739 bool 740 select LTO 741 help 742 Selected if the kernel will be built using Clang's LTO feature. 743 744config ARCH_SUPPORTS_LTO_CLANG 745 bool 746 help 747 An architecture should select this option if it supports: 748 - compiling with Clang, 749 - compiling inline assembly with Clang's integrated assembler, 750 - and linking with LLD. 751 752config ARCH_SUPPORTS_LTO_CLANG_THIN 753 bool 754 help 755 An architecture should select this option if it can support Clang's 756 ThinLTO mode. 757 758config HAS_LTO_CLANG 759 def_bool y 760 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 761 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 762 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 763 depends on ARCH_SUPPORTS_LTO_CLANG 764 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 765 # https://github.com/ClangBuiltLinux/linux/issues/1721 766 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 767 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 768 depends on !GCOV_KERNEL 769 help 770 The compiler and Kconfig options support building with Clang's 771 LTO. 772 773choice 774 prompt "Link Time Optimization (LTO)" 775 default LTO_NONE 776 help 777 This option enables Link Time Optimization (LTO), which allows the 778 compiler to optimize binaries globally. 779 780 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 781 so it's disabled by default. 782 783config LTO_NONE 784 bool "None" 785 help 786 Build the kernel normally, without Link Time Optimization (LTO). 787 788config LTO_CLANG_FULL 789 bool "Clang Full LTO (EXPERIMENTAL)" 790 depends on HAS_LTO_CLANG 791 depends on !COMPILE_TEST 792 select LTO_CLANG 793 help 794 This option enables Clang's full Link Time Optimization (LTO), which 795 allows the compiler to optimize the kernel globally. If you enable 796 this option, the compiler generates LLVM bitcode instead of ELF 797 object files, and the actual compilation from bitcode happens at 798 the LTO link step, which may take several minutes depending on the 799 kernel configuration. More information can be found from LLVM's 800 documentation: 801 802 https://llvm.org/docs/LinkTimeOptimization.html 803 804 During link time, this option can use a large amount of RAM, and 805 may take much longer than the ThinLTO option. 806 807config LTO_CLANG_THIN 808 bool "Clang ThinLTO (EXPERIMENTAL)" 809 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 810 select LTO_CLANG 811 help 812 This option enables Clang's ThinLTO, which allows for parallel 813 optimization and faster incremental compiles compared to the 814 CONFIG_LTO_CLANG_FULL option. More information can be found 815 from Clang's documentation: 816 817 https://clang.llvm.org/docs/ThinLTO.html 818 819 If unsure, say Y. 820endchoice 821 822config ARCH_SUPPORTS_AUTOFDO_CLANG 823 bool 824 825config AUTOFDO_CLANG 826 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 827 depends on ARCH_SUPPORTS_AUTOFDO_CLANG 828 depends on CC_IS_CLANG && CLANG_VERSION >= 170000 829 help 830 This option enables Clang’s AutoFDO build. When 831 an AutoFDO profile is specified in variable 832 CLANG_AUTOFDO_PROFILE during the build process, 833 Clang uses the profile to optimize the kernel. 834 835 If no profile is specified, AutoFDO options are 836 still passed to Clang to facilitate the collection 837 of perf data for creating an AutoFDO profile in 838 subsequent builds. 839 840 If unsure, say N. 841 842config ARCH_SUPPORTS_PROPELLER_CLANG 843 bool 844 845config PROPELLER_CLANG 846 bool "Enable Clang's Propeller build" 847 depends on ARCH_SUPPORTS_PROPELLER_CLANG 848 depends on CC_IS_CLANG && CLANG_VERSION >= 190000 849 help 850 This option enables Clang’s Propeller build. When the Propeller 851 profiles is specified in variable CLANG_PROPELLER_PROFILE_PREFIX 852 during the build process, Clang uses the profiles to optimize 853 the kernel. 854 855 If no profile is specified, Propeller options are still passed 856 to Clang to facilitate the collection of perf data for creating 857 the Propeller profiles in subsequent builds. 858 859 If unsure, say N. 860 861config ARCH_SUPPORTS_CFI_CLANG 862 bool 863 help 864 An architecture should select this option if it can support Clang's 865 Control-Flow Integrity (CFI) checking. 866 867config ARCH_USES_CFI_TRAPS 868 bool 869 870config CFI_CLANG 871 bool "Use Clang's Control Flow Integrity (CFI)" 872 depends on ARCH_SUPPORTS_CFI_CLANG 873 depends on $(cc-option,-fsanitize=kcfi) 874 help 875 This option enables Clang's forward-edge Control Flow Integrity 876 (CFI) checking, where the compiler injects a runtime check to each 877 indirect function call to ensure the target is a valid function with 878 the correct static type. This restricts possible call targets and 879 makes it more difficult for an attacker to exploit bugs that allow 880 the modification of stored function pointers. More information can be 881 found from Clang's documentation: 882 883 https://clang.llvm.org/docs/ControlFlowIntegrity.html 884 885config CFI_ICALL_NORMALIZE_INTEGERS 886 bool "Normalize CFI tags for integers" 887 depends on CFI_CLANG 888 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 889 help 890 This option normalizes the CFI tags for integer types so that all 891 integer types of the same size and signedness receive the same CFI 892 tag. 893 894 The option is separate from CONFIG_RUST because it affects the ABI. 895 When working with build systems that care about the ABI, it is 896 convenient to be able to turn on this flag first, before Rust is 897 turned on. 898 899 This option is necessary for using CFI with Rust. If unsure, say N. 900 901config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 902 def_bool y 903 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 904 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 905 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 906 907config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 908 def_bool y 909 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 910 depends on RUSTC_VERSION >= 107900 911 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 912 depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \ 913 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 914 915config CFI_PERMISSIVE 916 bool "Use CFI in permissive mode" 917 depends on CFI_CLANG 918 help 919 When selected, Control Flow Integrity (CFI) violations result in a 920 warning instead of a kernel panic. This option should only be used 921 for finding indirect call type mismatches during development. 922 923 If unsure, say N. 924 925config HAVE_ARCH_WITHIN_STACK_FRAMES 926 bool 927 help 928 An architecture should select this if it can walk the kernel stack 929 frames to determine if an object is part of either the arguments 930 or local variables (i.e. that it excludes saved return addresses, 931 and similar) by implementing an inline arch_within_stack_frames(), 932 which is used by CONFIG_HARDENED_USERCOPY. 933 934config HAVE_CONTEXT_TRACKING_USER 935 bool 936 help 937 Provide kernel/user boundaries probes necessary for subsystems 938 that need it, such as userspace RCU extended quiescent state. 939 Syscalls need to be wrapped inside user_exit()-user_enter(), either 940 optimized behind static key or through the slow path using TIF_NOHZ 941 flag. Exceptions handlers must be wrapped as well. Irqs are already 942 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 943 handling on irq exit still need to be protected. 944 945config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 946 bool 947 help 948 Architecture neither relies on exception_enter()/exception_exit() 949 nor on schedule_user(). Also preempt_schedule_notrace() and 950 preempt_schedule_irq() can't be called in a preemptible section 951 while context tracking is CT_STATE_USER. This feature reflects a sane 952 entry implementation where the following requirements are met on 953 critical entry code, ie: before user_exit() or after user_enter(): 954 955 - Critical entry code isn't preemptible (or better yet: 956 not interruptible). 957 - No use of RCU read side critical sections, unless ct_nmi_enter() 958 got called. 959 - No use of instrumentation, unless instrumentation_begin() got 960 called. 961 962config HAVE_TIF_NOHZ 963 bool 964 help 965 Arch relies on TIF_NOHZ and syscall slow path to implement context 966 tracking calls to user_enter()/user_exit(). 967 968config HAVE_VIRT_CPU_ACCOUNTING 969 bool 970 971config HAVE_VIRT_CPU_ACCOUNTING_IDLE 972 bool 973 help 974 Architecture has its own way to account idle CPU time and therefore 975 doesn't implement vtime_account_idle(). 976 977config ARCH_HAS_SCALED_CPUTIME 978 bool 979 980config HAVE_VIRT_CPU_ACCOUNTING_GEN 981 bool 982 default y if 64BIT 983 help 984 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 985 Before enabling this option, arch code must be audited 986 to ensure there are no races in concurrent read/write of 987 cputime_t. For example, reading/writing 64-bit cputime_t on 988 some 32-bit arches may require multiple accesses, so proper 989 locking is needed to protect against concurrent accesses. 990 991config HAVE_IRQ_TIME_ACCOUNTING 992 bool 993 help 994 Archs need to ensure they use a high enough resolution clock to 995 support irq time accounting and then call enable_sched_clock_irqtime(). 996 997config HAVE_MOVE_PUD 998 bool 999 help 1000 Architectures that select this are able to move page tables at the 1001 PUD level. If there are only 3 page table levels, the move effectively 1002 happens at the PGD level. 1003 1004config HAVE_MOVE_PMD 1005 bool 1006 help 1007 Archs that select this are able to move page tables at the PMD level. 1008 1009config HAVE_ARCH_TRANSPARENT_HUGEPAGE 1010 bool 1011 1012config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1013 bool 1014 1015config HAVE_ARCH_HUGE_VMAP 1016 bool 1017 1018# 1019# Archs that select this would be capable of PMD-sized vmaps (i.e., 1020# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 1021# must be used to enable allocations to use hugepages. 1022# 1023config HAVE_ARCH_HUGE_VMALLOC 1024 depends on HAVE_ARCH_HUGE_VMAP 1025 bool 1026 1027config ARCH_WANT_HUGE_PMD_SHARE 1028 bool 1029 1030# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1031# if there are no userspace memory management features that use it 1032config ARCH_WANT_KERNEL_PMD_MKWRITE 1033 bool 1034 1035config ARCH_WANT_PMD_MKWRITE 1036 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1037 1038config HAVE_ARCH_SOFT_DIRTY 1039 bool 1040 1041config HAVE_MOD_ARCH_SPECIFIC 1042 bool 1043 help 1044 The arch uses struct mod_arch_specific to store data. Many arches 1045 just need a simple module loader without arch specific data - those 1046 should not enable this. 1047 1048config MODULES_USE_ELF_RELA 1049 bool 1050 help 1051 Modules only use ELF RELA relocations. Modules with ELF REL 1052 relocations will give an error. 1053 1054config MODULES_USE_ELF_REL 1055 bool 1056 help 1057 Modules only use ELF REL relocations. Modules with ELF RELA 1058 relocations will give an error. 1059 1060config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1061 bool 1062 help 1063 For architectures like powerpc/32 which have constraints on module 1064 allocation and need to allocate module data outside of module area. 1065 1066config ARCH_WANTS_EXECMEM_LATE 1067 bool 1068 help 1069 For architectures that do not allocate executable memory early on 1070 boot, but rather require its initialization late when there is 1071 enough entropy for module space randomization, for instance 1072 arm64. 1073 1074config ARCH_HAS_EXECMEM_ROX 1075 bool 1076 depends on MMU && !HIGHMEM 1077 help 1078 For architectures that support allocations of executable memory 1079 with read-only execute permissions. Architecture must implement 1080 execmem_fill_trapping_insns() callback to enable this. 1081 1082config HAVE_IRQ_EXIT_ON_IRQ_STACK 1083 bool 1084 help 1085 Architecture doesn't only execute the irq handler on the irq stack 1086 but also irq_exit(). This way we can process softirqs on this irq 1087 stack instead of switching to a new one when we call __do_softirq() 1088 in the end of an hardirq. 1089 This spares a stack switch and improves cache usage on softirq 1090 processing. 1091 1092config HAVE_SOFTIRQ_ON_OWN_STACK 1093 bool 1094 help 1095 Architecture provides a function to run __do_softirq() on a 1096 separate stack. 1097 1098config SOFTIRQ_ON_OWN_STACK 1099 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1100 1101config ALTERNATE_USER_ADDRESS_SPACE 1102 bool 1103 help 1104 Architectures set this when the CPU uses separate address 1105 spaces for kernel and user space pointers. In this case, the 1106 access_ok() check on a __user pointer is skipped. 1107 1108config PGTABLE_LEVELS 1109 int 1110 default 2 1111 1112config ARCH_HAS_ELF_RANDOMIZE 1113 bool 1114 help 1115 An architecture supports choosing randomized locations for 1116 stack, mmap, brk, and ET_DYN. Defined functions: 1117 - arch_mmap_rnd() 1118 - arch_randomize_brk() 1119 1120config HAVE_ARCH_MMAP_RND_BITS 1121 bool 1122 help 1123 An arch should select this symbol if it supports setting a variable 1124 number of bits for use in establishing the base address for mmap 1125 allocations, has MMU enabled and provides values for both: 1126 - ARCH_MMAP_RND_BITS_MIN 1127 - ARCH_MMAP_RND_BITS_MAX 1128 1129config HAVE_EXIT_THREAD 1130 bool 1131 help 1132 An architecture implements exit_thread. 1133 1134config ARCH_MMAP_RND_BITS_MIN 1135 int 1136 1137config ARCH_MMAP_RND_BITS_MAX 1138 int 1139 1140config ARCH_MMAP_RND_BITS_DEFAULT 1141 int 1142 1143config ARCH_MMAP_RND_BITS 1144 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1145 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1146 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1147 default ARCH_MMAP_RND_BITS_MIN 1148 depends on HAVE_ARCH_MMAP_RND_BITS 1149 help 1150 This value can be used to select the number of bits to use to 1151 determine the random offset to the base address of vma regions 1152 resulting from mmap allocations. This value will be bounded 1153 by the architecture's minimum and maximum supported values. 1154 1155 This value can be changed after boot using the 1156 /proc/sys/vm/mmap_rnd_bits tunable 1157 1158config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1159 bool 1160 help 1161 An arch should select this symbol if it supports running applications 1162 in compatibility mode, supports setting a variable number of bits for 1163 use in establishing the base address for mmap allocations, has MMU 1164 enabled and provides values for both: 1165 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1166 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1167 1168config ARCH_MMAP_RND_COMPAT_BITS_MIN 1169 int 1170 1171config ARCH_MMAP_RND_COMPAT_BITS_MAX 1172 int 1173 1174config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1175 int 1176 1177config ARCH_MMAP_RND_COMPAT_BITS 1178 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1179 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1180 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1181 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1182 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1183 help 1184 This value can be used to select the number of bits to use to 1185 determine the random offset to the base address of vma regions 1186 resulting from mmap allocations for compatible applications This 1187 value will be bounded by the architecture's minimum and maximum 1188 supported values. 1189 1190 This value can be changed after boot using the 1191 /proc/sys/vm/mmap_rnd_compat_bits tunable 1192 1193config HAVE_ARCH_COMPAT_MMAP_BASES 1194 bool 1195 help 1196 This allows 64bit applications to invoke 32-bit mmap() syscall 1197 and vice-versa 32-bit applications to call 64-bit mmap(). 1198 Required for applications doing different bitness syscalls. 1199 1200config HAVE_PAGE_SIZE_4KB 1201 bool 1202 1203config HAVE_PAGE_SIZE_8KB 1204 bool 1205 1206config HAVE_PAGE_SIZE_16KB 1207 bool 1208 1209config HAVE_PAGE_SIZE_32KB 1210 bool 1211 1212config HAVE_PAGE_SIZE_64KB 1213 bool 1214 1215config HAVE_PAGE_SIZE_256KB 1216 bool 1217 1218choice 1219 prompt "MMU page size" 1220 1221config PAGE_SIZE_4KB 1222 bool "4KiB pages" 1223 depends on HAVE_PAGE_SIZE_4KB 1224 help 1225 This option select the standard 4KiB Linux page size and the only 1226 available option on many architectures. Using 4KiB page size will 1227 minimize memory consumption and is therefore recommended for low 1228 memory systems. 1229 Some software that is written for x86 systems makes incorrect 1230 assumptions about the page size and only runs on 4KiB pages. 1231 1232config PAGE_SIZE_8KB 1233 bool "8KiB pages" 1234 depends on HAVE_PAGE_SIZE_8KB 1235 help 1236 This option is the only supported page size on a few older 1237 processors, and can be slightly faster than 4KiB pages. 1238 1239config PAGE_SIZE_16KB 1240 bool "16KiB pages" 1241 depends on HAVE_PAGE_SIZE_16KB 1242 help 1243 This option is usually a good compromise between memory 1244 consumption and performance for typical desktop and server 1245 workloads, often saving a level of page table lookups compared 1246 to 4KB pages as well as reducing TLB pressure and overhead of 1247 per-page operations in the kernel at the expense of a larger 1248 page cache. 1249 1250config PAGE_SIZE_32KB 1251 bool "32KiB pages" 1252 depends on HAVE_PAGE_SIZE_32KB 1253 help 1254 Using 32KiB page size will result in slightly higher performance 1255 kernel at the price of higher memory consumption compared to 1256 16KiB pages. This option is available only on cnMIPS cores. 1257 Note that you will need a suitable Linux distribution to 1258 support this. 1259 1260config PAGE_SIZE_64KB 1261 bool "64KiB pages" 1262 depends on HAVE_PAGE_SIZE_64KB 1263 help 1264 Using 64KiB page size will result in slightly higher performance 1265 kernel at the price of much higher memory consumption compared to 1266 4KiB or 16KiB pages. 1267 This is not suitable for general-purpose workloads but the 1268 better performance may be worth the cost for certain types of 1269 supercomputing or database applications that work mostly with 1270 large in-memory data rather than small files. 1271 1272config PAGE_SIZE_256KB 1273 bool "256KiB pages" 1274 depends on HAVE_PAGE_SIZE_256KB 1275 help 1276 256KiB pages have little practical value due to their extreme 1277 memory usage. The kernel will only be able to run applications 1278 that have been compiled with '-zmax-page-size' set to 256KiB 1279 (the default is 64KiB or 4KiB on most architectures). 1280 1281endchoice 1282 1283config PAGE_SIZE_LESS_THAN_64KB 1284 def_bool y 1285 depends on !PAGE_SIZE_64KB 1286 depends on PAGE_SIZE_LESS_THAN_256KB 1287 1288config PAGE_SIZE_LESS_THAN_256KB 1289 def_bool y 1290 depends on !PAGE_SIZE_256KB 1291 1292config PAGE_SHIFT 1293 int 1294 default 12 if PAGE_SIZE_4KB 1295 default 13 if PAGE_SIZE_8KB 1296 default 14 if PAGE_SIZE_16KB 1297 default 15 if PAGE_SIZE_32KB 1298 default 16 if PAGE_SIZE_64KB 1299 default 18 if PAGE_SIZE_256KB 1300 1301# This allows to use a set of generic functions to determine mmap base 1302# address by giving priority to top-down scheme only if the process 1303# is not in legacy mode (compat task, unlimited stack size or 1304# sysctl_legacy_va_layout). 1305# Architecture that selects this option can provide its own version of: 1306# - STACK_RND_MASK 1307config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1308 bool 1309 depends on MMU 1310 select ARCH_HAS_ELF_RANDOMIZE 1311 1312config HAVE_OBJTOOL 1313 bool 1314 1315config HAVE_JUMP_LABEL_HACK 1316 bool 1317 1318config HAVE_NOINSTR_HACK 1319 bool 1320 1321config HAVE_NOINSTR_VALIDATION 1322 bool 1323 1324config HAVE_UACCESS_VALIDATION 1325 bool 1326 select OBJTOOL 1327 1328config HAVE_STACK_VALIDATION 1329 bool 1330 help 1331 Architecture supports objtool compile-time frame pointer rule 1332 validation. 1333 1334config HAVE_RELIABLE_STACKTRACE 1335 bool 1336 help 1337 Architecture has either save_stack_trace_tsk_reliable() or 1338 arch_stack_walk_reliable() function which only returns a stack trace 1339 if it can guarantee the trace is reliable. 1340 1341config HAVE_ARCH_HASH 1342 bool 1343 default n 1344 help 1345 If this is set, the architecture provides an <asm/hash.h> 1346 file which provides platform-specific implementations of some 1347 functions in <linux/hash.h> or fs/namei.c. 1348 1349config HAVE_ARCH_NVRAM_OPS 1350 bool 1351 1352config ISA_BUS_API 1353 def_bool ISA 1354 1355# 1356# ABI hall of shame 1357# 1358config CLONE_BACKWARDS 1359 bool 1360 help 1361 Architecture has tls passed as the 4th argument of clone(2), 1362 not the 5th one. 1363 1364config CLONE_BACKWARDS2 1365 bool 1366 help 1367 Architecture has the first two arguments of clone(2) swapped. 1368 1369config CLONE_BACKWARDS3 1370 bool 1371 help 1372 Architecture has tls passed as the 3rd argument of clone(2), 1373 not the 5th one. 1374 1375config ODD_RT_SIGACTION 1376 bool 1377 help 1378 Architecture has unusual rt_sigaction(2) arguments 1379 1380config OLD_SIGSUSPEND 1381 bool 1382 help 1383 Architecture has old sigsuspend(2) syscall, of one-argument variety 1384 1385config OLD_SIGSUSPEND3 1386 bool 1387 help 1388 Even weirder antique ABI - three-argument sigsuspend(2) 1389 1390config OLD_SIGACTION 1391 bool 1392 help 1393 Architecture has old sigaction(2) syscall. Nope, not the same 1394 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1395 but fairly different variant of sigaction(2), thanks to OSF/1 1396 compatibility... 1397 1398config COMPAT_OLD_SIGACTION 1399 bool 1400 1401config COMPAT_32BIT_TIME 1402 bool "Provide system calls for 32-bit time_t" 1403 default !64BIT || COMPAT 1404 help 1405 This enables 32 bit time_t support in addition to 64 bit time_t support. 1406 This is relevant on all 32-bit architectures, and 64-bit architectures 1407 as part of compat syscall handling. 1408 1409config ARCH_NO_PREEMPT 1410 bool 1411 1412config ARCH_SUPPORTS_RT 1413 bool 1414 1415config CPU_NO_EFFICIENT_FFS 1416 def_bool n 1417 1418config HAVE_ARCH_VMAP_STACK 1419 def_bool n 1420 help 1421 An arch should select this symbol if it can support kernel stacks 1422 in vmalloc space. This means: 1423 1424 - vmalloc space must be large enough to hold many kernel stacks. 1425 This may rule out many 32-bit architectures. 1426 1427 - Stacks in vmalloc space need to work reliably. For example, if 1428 vmap page tables are created on demand, either this mechanism 1429 needs to work while the stack points to a virtual address with 1430 unpopulated page tables or arch code (switch_to() and switch_mm(), 1431 most likely) needs to ensure that the stack's page table entries 1432 are populated before running on a possibly unpopulated stack. 1433 1434 - If the stack overflows into a guard page, something reasonable 1435 should happen. The definition of "reasonable" is flexible, but 1436 instantly rebooting without logging anything would be unfriendly. 1437 1438config VMAP_STACK 1439 default y 1440 bool "Use a virtually-mapped stack" 1441 depends on HAVE_ARCH_VMAP_STACK 1442 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1443 help 1444 Enable this if you want the use virtually-mapped kernel stacks 1445 with guard pages. This causes kernel stack overflows to be 1446 caught immediately rather than causing difficult-to-diagnose 1447 corruption. 1448 1449 To use this with software KASAN modes, the architecture must support 1450 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1451 must be enabled. 1452 1453config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1454 def_bool n 1455 help 1456 An arch should select this symbol if it can support kernel stack 1457 offset randomization with calls to add_random_kstack_offset() 1458 during syscall entry and choose_random_kstack_offset() during 1459 syscall exit. Careful removal of -fstack-protector-strong and 1460 -fstack-protector should also be applied to the entry code and 1461 closely examined, as the artificial stack bump looks like an array 1462 to the compiler, so it will attempt to add canary checks regardless 1463 of the static branch state. 1464 1465config RANDOMIZE_KSTACK_OFFSET 1466 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1467 default y 1468 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1469 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1470 help 1471 The kernel stack offset can be randomized (after pt_regs) by 1472 roughly 5 bits of entropy, frustrating memory corruption 1473 attacks that depend on stack address determinism or 1474 cross-syscall address exposures. 1475 1476 The feature is controlled via the "randomize_kstack_offset=on/off" 1477 kernel boot param, and if turned off has zero overhead due to its use 1478 of static branches (see JUMP_LABEL). 1479 1480 If unsure, say Y. 1481 1482config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1483 bool "Default state of kernel stack offset randomization" 1484 depends on RANDOMIZE_KSTACK_OFFSET 1485 help 1486 Kernel stack offset randomization is controlled by kernel boot param 1487 "randomize_kstack_offset=on/off", and this config chooses the default 1488 boot state. 1489 1490config ARCH_OPTIONAL_KERNEL_RWX 1491 def_bool n 1492 1493config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1494 def_bool n 1495 1496config ARCH_HAS_STRICT_KERNEL_RWX 1497 def_bool n 1498 1499config STRICT_KERNEL_RWX 1500 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1501 depends on ARCH_HAS_STRICT_KERNEL_RWX 1502 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1503 help 1504 If this is set, kernel text and rodata memory will be made read-only, 1505 and non-text memory will be made non-executable. This provides 1506 protection against certain security exploits (e.g. executing the heap 1507 or modifying text) 1508 1509 These features are considered standard security practice these days. 1510 You should say Y here in almost all cases. 1511 1512config ARCH_HAS_STRICT_MODULE_RWX 1513 def_bool n 1514 1515config STRICT_MODULE_RWX 1516 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1517 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1518 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1519 help 1520 If this is set, module text and rodata memory will be made read-only, 1521 and non-text memory will be made non-executable. This provides 1522 protection against certain security exploits (e.g. writing to text) 1523 1524# select if the architecture provides an asm/dma-direct.h header 1525config ARCH_HAS_PHYS_TO_DMA 1526 bool 1527 1528config ARCH_HAS_CPU_RESCTRL 1529 bool 1530 help 1531 An architecture selects this option to indicate that the necessary 1532 hooks are provided to support the common memory system usage 1533 monitoring and control interfaces provided by the 'resctrl' 1534 filesystem (see RESCTRL_FS). 1535 1536config HAVE_ARCH_COMPILER_H 1537 bool 1538 help 1539 An architecture can select this if it provides an 1540 asm/compiler.h header that should be included after 1541 linux/compiler-*.h in order to override macro definitions that those 1542 headers generally provide. 1543 1544config HAVE_ARCH_LIBGCC_H 1545 bool 1546 help 1547 An architecture can select this if it provides an 1548 asm/libgcc.h header that should be included after 1549 linux/libgcc.h in order to override macro definitions that 1550 header generally provides. 1551 1552config HAVE_ARCH_PREL32_RELOCATIONS 1553 bool 1554 help 1555 May be selected by an architecture if it supports place-relative 1556 32-bit relocations, both in the toolchain and in the module loader, 1557 in which case relative references can be used in special sections 1558 for PCI fixup, initcalls etc which are only half the size on 64 bit 1559 architectures, and don't require runtime relocation on relocatable 1560 kernels. 1561 1562config ARCH_USE_MEMREMAP_PROT 1563 bool 1564 1565config LOCK_EVENT_COUNTS 1566 bool "Locking event counts collection" 1567 depends on DEBUG_FS 1568 help 1569 Enable light-weight counting of various locking related events 1570 in the system with minimal performance impact. This reduces 1571 the chance of application behavior change because of timing 1572 differences. The counts are reported via debugfs. 1573 1574# Select if the architecture has support for applying RELR relocations. 1575config ARCH_HAS_RELR 1576 bool 1577 1578config RELR 1579 bool "Use RELR relocation packing" 1580 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1581 default y 1582 help 1583 Store the kernel's dynamic relocations in the RELR relocation packing 1584 format. Requires a compatible linker (LLD supports this feature), as 1585 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1586 are compatible). 1587 1588config ARCH_HAS_MEM_ENCRYPT 1589 bool 1590 1591config ARCH_HAS_CC_PLATFORM 1592 bool 1593 1594config HAVE_SPARSE_SYSCALL_NR 1595 bool 1596 help 1597 An architecture should select this if its syscall numbering is sparse 1598 to save space. For example, MIPS architecture has a syscall array with 1599 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1600 related optimizations for a given architecture. 1601 1602config ARCH_HAS_VDSO_ARCH_DATA 1603 depends on GENERIC_VDSO_DATA_STORE 1604 bool 1605 1606config ARCH_HAS_VDSO_TIME_DATA 1607 bool 1608 1609config HAVE_STATIC_CALL 1610 bool 1611 1612config HAVE_STATIC_CALL_INLINE 1613 bool 1614 depends on HAVE_STATIC_CALL 1615 select OBJTOOL 1616 1617config HAVE_PREEMPT_DYNAMIC 1618 bool 1619 1620config HAVE_PREEMPT_DYNAMIC_CALL 1621 bool 1622 depends on HAVE_STATIC_CALL 1623 select HAVE_PREEMPT_DYNAMIC 1624 help 1625 An architecture should select this if it can handle the preemption 1626 model being selected at boot time using static calls. 1627 1628 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1629 preemption function will be patched directly. 1630 1631 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1632 call to a preemption function will go through a trampoline, and the 1633 trampoline will be patched. 1634 1635 It is strongly advised to support inline static call to avoid any 1636 overhead. 1637 1638config HAVE_PREEMPT_DYNAMIC_KEY 1639 bool 1640 depends on HAVE_ARCH_JUMP_LABEL 1641 select HAVE_PREEMPT_DYNAMIC 1642 help 1643 An architecture should select this if it can handle the preemption 1644 model being selected at boot time using static keys. 1645 1646 Each preemption function will be given an early return based on a 1647 static key. This should have slightly lower overhead than non-inline 1648 static calls, as this effectively inlines each trampoline into the 1649 start of its callee. This may avoid redundant work, and may 1650 integrate better with CFI schemes. 1651 1652 This will have greater overhead than using inline static calls as 1653 the call to the preemption function cannot be entirely elided. 1654 1655config ARCH_WANT_LD_ORPHAN_WARN 1656 bool 1657 help 1658 An arch should select this symbol once all linker sections are explicitly 1659 included, size-asserted, or discarded in the linker scripts. This is 1660 important because we never want expected sections to be placed heuristically 1661 by the linker, since the locations of such sections can change between linker 1662 versions. 1663 1664config HAVE_ARCH_PFN_VALID 1665 bool 1666 1667config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1668 bool 1669 1670config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1671 bool 1672 1673config ARCH_SPLIT_ARG64 1674 bool 1675 help 1676 If a 32-bit architecture requires 64-bit arguments to be split into 1677 pairs of 32-bit arguments, select this option. 1678 1679config ARCH_HAS_ELFCORE_COMPAT 1680 bool 1681 1682config ARCH_HAS_PARANOID_L1D_FLUSH 1683 bool 1684 1685config ARCH_HAVE_TRACE_MMIO_ACCESS 1686 bool 1687 1688config DYNAMIC_SIGFRAME 1689 bool 1690 1691# Select, if arch has a named attribute group bound to NUMA device nodes. 1692config HAVE_ARCH_NODE_DEV_GROUP 1693 bool 1694 1695config ARCH_HAS_HW_PTE_YOUNG 1696 bool 1697 help 1698 Architectures that select this option are capable of setting the 1699 accessed bit in PTE entries when using them as part of linear address 1700 translations. Architectures that require runtime check should select 1701 this option and override arch_has_hw_pte_young(). 1702 1703config ARCH_HAS_NONLEAF_PMD_YOUNG 1704 bool 1705 help 1706 Architectures that select this option are capable of setting the 1707 accessed bit in non-leaf PMD entries when using them as part of linear 1708 address translations. Page table walkers that clear the accessed bit 1709 may use this capability to reduce their search space. 1710 1711config ARCH_HAS_KERNEL_FPU_SUPPORT 1712 bool 1713 help 1714 Architectures that select this option can run floating-point code in 1715 the kernel, as described in Documentation/core-api/floating-point.rst. 1716 1717config ARCH_VMLINUX_NEEDS_RELOCS 1718 bool 1719 help 1720 Whether the architecture needs vmlinux to be built with static 1721 relocations preserved. This is used by some architectures to 1722 construct bespoke relocation tables for KASLR. 1723 1724source "kernel/gcov/Kconfig" 1725 1726source "scripts/gcc-plugins/Kconfig" 1727 1728config FUNCTION_ALIGNMENT_4B 1729 bool 1730 1731config FUNCTION_ALIGNMENT_8B 1732 bool 1733 1734config FUNCTION_ALIGNMENT_16B 1735 bool 1736 1737config FUNCTION_ALIGNMENT_32B 1738 bool 1739 1740config FUNCTION_ALIGNMENT_64B 1741 bool 1742 1743config FUNCTION_ALIGNMENT 1744 int 1745 default 64 if FUNCTION_ALIGNMENT_64B 1746 default 32 if FUNCTION_ALIGNMENT_32B 1747 default 16 if FUNCTION_ALIGNMENT_16B 1748 default 8 if FUNCTION_ALIGNMENT_8B 1749 default 4 if FUNCTION_ALIGNMENT_4B 1750 default 0 1751 1752config CC_HAS_MIN_FUNCTION_ALIGNMENT 1753 # Detect availability of the GCC option -fmin-function-alignment which 1754 # guarantees minimal alignment for all functions, unlike 1755 # -falign-functions which the compiler ignores for cold functions. 1756 def_bool $(cc-option, -fmin-function-alignment=8) 1757 1758config CC_HAS_SANE_FUNCTION_ALIGNMENT 1759 # Set if the guaranteed alignment with -fmin-function-alignment is 1760 # available or extra care is required in the kernel. Clang provides 1761 # strict alignment always, even with -falign-functions. 1762 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1763 1764config ARCH_NEED_CMPXCHG_1_EMU 1765 bool 1766 1767config ARCH_WANTS_PRE_LINK_VMLINUX 1768 bool 1769 help 1770 An architecture can select this if it provides arch/<arch>/tools/Makefile 1771 with .arch.vmlinux.o target to be linked into vmlinux. 1772 1773endmenu 1774