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 help 139 Uprobes is the user-space counterpart to kprobes: they 140 enable instrumentation applications (such as 'perf probe') 141 to establish unintrusive probes in user-space binaries and 142 libraries, by executing handler functions when the probes 143 are hit by user-space applications. 144 145 ( These probes come in the form of single-byte breakpoints, 146 managed by the kernel and kept transparent to the probed 147 application. ) 148 149config HAVE_64BIT_ALIGNED_ACCESS 150 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 151 help 152 Some architectures require 64 bit accesses to be 64 bit 153 aligned, which also requires structs containing 64 bit values 154 to be 64 bit aligned too. This includes some 32 bit 155 architectures which can do 64 bit accesses, as well as 64 bit 156 architectures without unaligned access. 157 158 This symbol should be selected by an architecture if 64 bit 159 accesses are required to be 64 bit aligned in this way even 160 though it is not a 64 bit architecture. 161 162 See Documentation/core-api/unaligned-memory-access.rst for 163 more information on the topic of unaligned memory accesses. 164 165config HAVE_EFFICIENT_UNALIGNED_ACCESS 166 bool 167 help 168 Some architectures are unable to perform unaligned accesses 169 without the use of get_unaligned/put_unaligned. Others are 170 unable to perform such accesses efficiently (e.g. trap on 171 unaligned access and require fixing it up in the exception 172 handler.) 173 174 This symbol should be selected by an architecture if it can 175 perform unaligned accesses efficiently to allow different 176 code paths to be selected for these cases. Some network 177 drivers, for example, could opt to not fix up alignment 178 problems with received packets if doing so would not help 179 much. 180 181 See Documentation/core-api/unaligned-memory-access.rst for more 182 information on the topic of unaligned memory accesses. 183 184config ARCH_USE_BUILTIN_BSWAP 185 bool 186 help 187 Modern versions of GCC (since 4.4) have builtin functions 188 for handling byte-swapping. Using these, instead of the old 189 inline assembler that the architecture code provides in the 190 __arch_bswapXX() macros, allows the compiler to see what's 191 happening and offers more opportunity for optimisation. In 192 particular, the compiler will be able to combine the byteswap 193 with a nearby load or store and use load-and-swap or 194 store-and-swap instructions if the architecture has them. It 195 should almost *never* result in code which is worse than the 196 hand-coded assembler in <asm/swab.h>. But just in case it 197 does, the use of the builtins is optional. 198 199 Any architecture with load-and-swap or store-and-swap 200 instructions should set this. And it shouldn't hurt to set it 201 on architectures that don't have such instructions. 202 203config KRETPROBES 204 def_bool y 205 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 206 207config KRETPROBE_ON_RETHOOK 208 def_bool y 209 depends on HAVE_RETHOOK 210 depends on KRETPROBES 211 select RETHOOK 212 213config USER_RETURN_NOTIFIER 214 bool 215 depends on HAVE_USER_RETURN_NOTIFIER 216 help 217 Provide a kernel-internal notification when a cpu is about to 218 switch to user mode. 219 220config HAVE_IOREMAP_PROT 221 bool 222 223config HAVE_KPROBES 224 bool 225 226config HAVE_KRETPROBES 227 bool 228 229config HAVE_OPTPROBES 230 bool 231 232config HAVE_KPROBES_ON_FTRACE 233 bool 234 235config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 236 bool 237 help 238 Since kretprobes modifies return address on the stack, the 239 stacktrace may see the kretprobe trampoline address instead 240 of correct one. If the architecture stacktrace code and 241 unwinder can adjust such entries, select this configuration. 242 243config HAVE_FUNCTION_ERROR_INJECTION 244 bool 245 246config HAVE_NMI 247 bool 248 249config HAVE_FUNCTION_DESCRIPTORS 250 bool 251 252config TRACE_IRQFLAGS_SUPPORT 253 bool 254 255config TRACE_IRQFLAGS_NMI_SUPPORT 256 bool 257 258# 259# An arch should select this if it provides all these things: 260# 261# task_pt_regs() in asm/processor.h or asm/ptrace.h 262# arch_has_single_step() if there is hardware single-step support 263# arch_has_block_step() if there is hardware block-step support 264# asm/syscall.h supplying asm-generic/syscall.h interface 265# linux/regset.h user_regset interfaces 266# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 267# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 268# TIF_NOTIFY_RESUME calls resume_user_mode_work() 269# 270config HAVE_ARCH_TRACEHOOK 271 bool 272 273config HAVE_DMA_CONTIGUOUS 274 bool 275 276config GENERIC_SMP_IDLE_THREAD 277 bool 278 279config GENERIC_IDLE_POLL_SETUP 280 bool 281 282config ARCH_HAS_FORTIFY_SOURCE 283 bool 284 help 285 An architecture should select this when it can successfully 286 build and run with CONFIG_FORTIFY_SOURCE. 287 288# 289# Select if the arch provides a historic keepinit alias for the retain_initrd 290# command line option 291# 292config ARCH_HAS_KEEPINITRD 293 bool 294 295# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 296config ARCH_HAS_SET_MEMORY 297 bool 298 299# Select if arch has all set_direct_map_invalid/default() functions 300config ARCH_HAS_SET_DIRECT_MAP 301 bool 302 303# 304# Select if the architecture provides the arch_dma_set_uncached symbol to 305# either provide an uncached segment alias for a DMA allocation, or 306# to remap the page tables in place. 307# 308config ARCH_HAS_DMA_SET_UNCACHED 309 bool 310 311# 312# Select if the architectures provides the arch_dma_clear_uncached symbol 313# to undo an in-place page table remap for uncached access. 314# 315config ARCH_HAS_DMA_CLEAR_UNCACHED 316 bool 317 318config ARCH_HAS_CPU_FINALIZE_INIT 319 bool 320 321# The architecture has a per-task state that includes the mm's PASID 322config ARCH_HAS_CPU_PASID 323 bool 324 select IOMMU_MM_DATA 325 326config HAVE_ARCH_THREAD_STRUCT_WHITELIST 327 bool 328 help 329 An architecture should select this to provide hardened usercopy 330 knowledge about what region of the thread_struct should be 331 whitelisted for copying to userspace. Normally this is only the 332 FPU registers. Specifically, arch_thread_struct_whitelist() 333 should be implemented. Without this, the entire thread_struct 334 field in task_struct will be left whitelisted. 335 336# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 337config ARCH_WANTS_DYNAMIC_TASK_STRUCT 338 bool 339 340config ARCH_WANTS_NO_INSTR 341 bool 342 help 343 An architecture should select this if the noinstr macro is being used on 344 functions to denote that the toolchain should avoid instrumenting such 345 functions and is required for correctness. 346 347config ARCH_32BIT_OFF_T 348 bool 349 depends on !64BIT 350 help 351 All new 32-bit architectures should have 64-bit off_t type on 352 userspace side which corresponds to the loff_t kernel type. This 353 is the requirement for modern ABIs. Some existing architectures 354 still support 32-bit off_t. This option is enabled for all such 355 architectures explicitly. 356 357# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 358config ARCH_32BIT_USTAT_F_TINODE 359 bool 360 361config HAVE_ASM_MODVERSIONS 362 bool 363 help 364 This symbol should be selected by an architecture if it provides 365 <asm/asm-prototypes.h> to support the module versioning for symbols 366 exported from assembly code. 367 368config HAVE_REGS_AND_STACK_ACCESS_API 369 bool 370 help 371 This symbol should be selected by an architecture if it supports 372 the API needed to access registers and stack entries from pt_regs, 373 declared in asm/ptrace.h 374 For example the kprobes-based event tracer needs this API. 375 376config HAVE_RSEQ 377 bool 378 depends on HAVE_REGS_AND_STACK_ACCESS_API 379 help 380 This symbol should be selected by an architecture if it 381 supports an implementation of restartable sequences. 382 383config HAVE_RUST 384 bool 385 help 386 This symbol should be selected by an architecture if it 387 supports Rust. 388 389config HAVE_FUNCTION_ARG_ACCESS_API 390 bool 391 help 392 This symbol should be selected by an architecture if it supports 393 the API needed to access function arguments from pt_regs, 394 declared in asm/ptrace.h 395 396config HAVE_HW_BREAKPOINT 397 bool 398 depends on PERF_EVENTS 399 400config HAVE_MIXED_BREAKPOINTS_REGS 401 bool 402 depends on HAVE_HW_BREAKPOINT 403 help 404 Depending on the arch implementation of hardware breakpoints, 405 some of them have separate registers for data and instruction 406 breakpoints addresses, others have mixed registers to store 407 them but define the access type in a control register. 408 Select this option if your arch implements breakpoints under the 409 latter fashion. 410 411config HAVE_USER_RETURN_NOTIFIER 412 bool 413 414config HAVE_PERF_EVENTS_NMI 415 bool 416 help 417 System hardware can generate an NMI using the perf event 418 subsystem. Also has support for calculating CPU cycle events 419 to determine how many clock cycles in a given period. 420 421config HAVE_HARDLOCKUP_DETECTOR_PERF 422 bool 423 depends on HAVE_PERF_EVENTS_NMI 424 help 425 The arch chooses to use the generic perf-NMI-based hardlockup 426 detector. Must define HAVE_PERF_EVENTS_NMI. 427 428config HAVE_HARDLOCKUP_DETECTOR_ARCH 429 bool 430 help 431 The arch provides its own hardlockup detector implementation instead 432 of the generic ones. 433 434 It uses the same command line parameters, and sysctl interface, 435 as the generic hardlockup detectors. 436 437config HAVE_PERF_REGS 438 bool 439 help 440 Support selective register dumps for perf events. This includes 441 bit-mapping of each registers and a unique architecture id. 442 443config HAVE_PERF_USER_STACK_DUMP 444 bool 445 help 446 Support user stack dumps for perf event samples. This needs 447 access to the user stack pointer which is not unified across 448 architectures. 449 450config HAVE_ARCH_JUMP_LABEL 451 bool 452 453config HAVE_ARCH_JUMP_LABEL_RELATIVE 454 bool 455 456config MMU_GATHER_TABLE_FREE 457 bool 458 459config MMU_GATHER_RCU_TABLE_FREE 460 bool 461 select MMU_GATHER_TABLE_FREE 462 463config MMU_GATHER_PAGE_SIZE 464 bool 465 466config MMU_GATHER_NO_RANGE 467 bool 468 select MMU_GATHER_MERGE_VMAS 469 470config MMU_GATHER_NO_FLUSH_CACHE 471 bool 472 473config MMU_GATHER_MERGE_VMAS 474 bool 475 476config MMU_GATHER_NO_GATHER 477 bool 478 depends on MMU_GATHER_TABLE_FREE 479 480config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 481 bool 482 help 483 Temporary select until all architectures can be converted to have 484 irqs disabled over activate_mm. Architectures that do IPI based TLB 485 shootdowns should enable this. 486 487# Use normal mm refcounting for MMU_LAZY_TLB kernel thread references. 488# MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching 489# to/from kernel threads when the same mm is running on a lot of CPUs (a large 490# multi-threaded application), by reducing contention on the mm refcount. 491# 492# This can be disabled if the architecture ensures no CPUs are using an mm as a 493# "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm 494# or its kernel page tables). This could be arranged by arch_exit_mmap(), or 495# final exit(2) TLB flush, for example. 496# 497# To implement this, an arch *must*: 498# Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating 499# the lazy tlb reference of a kthread's ->active_mm (non-arch code has been 500# converted already). 501config MMU_LAZY_TLB_REFCOUNT 502 def_bool y 503 depends on !MMU_LAZY_TLB_SHOOTDOWN 504 505# This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an 506# mm as a lazy tlb beyond its last reference count, by shooting down these 507# users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may 508# be using the mm as a lazy tlb, so that they may switch themselves to using 509# init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs 510# may be using mm as a lazy tlb mm. 511# 512# To implement this, an arch *must*: 513# - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains 514# at least all possible CPUs in which the mm is lazy. 515# - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above). 516config MMU_LAZY_TLB_SHOOTDOWN 517 bool 518 519config ARCH_HAVE_NMI_SAFE_CMPXCHG 520 bool 521 522config ARCH_HAVE_EXTRA_ELF_NOTES 523 bool 524 help 525 An architecture should select this in order to enable adding an 526 arch-specific ELF note section to core files. It must provide two 527 functions: elf_coredump_extra_notes_size() and 528 elf_coredump_extra_notes_write() which are invoked by the ELF core 529 dumper. 530 531config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 532 bool 533 534config HAVE_ALIGNED_STRUCT_PAGE 535 bool 536 help 537 This makes sure that struct pages are double word aligned and that 538 e.g. the SLUB allocator can perform double word atomic operations 539 on a struct page for better performance. However selecting this 540 might increase the size of a struct page by a word. 541 542config HAVE_CMPXCHG_LOCAL 543 bool 544 545config HAVE_CMPXCHG_DOUBLE 546 bool 547 548config ARCH_WEAK_RELEASE_ACQUIRE 549 bool 550 551config ARCH_WANT_IPC_PARSE_VERSION 552 bool 553 554config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 555 bool 556 557config ARCH_WANT_OLD_COMPAT_IPC 558 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 559 bool 560 561config HAVE_ARCH_SECCOMP 562 bool 563 help 564 An arch should select this symbol to support seccomp mode 1 (the fixed 565 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 566 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 567 - __NR_seccomp_read_32 568 - __NR_seccomp_write_32 569 - __NR_seccomp_exit_32 570 - __NR_seccomp_sigreturn_32 571 572config HAVE_ARCH_SECCOMP_FILTER 573 bool 574 select HAVE_ARCH_SECCOMP 575 help 576 An arch should select this symbol if it provides all of these things: 577 - all the requirements for HAVE_ARCH_SECCOMP 578 - syscall_get_arch() 579 - syscall_get_arguments() 580 - syscall_rollback() 581 - syscall_set_return_value() 582 - SIGSYS siginfo_t support 583 - secure_computing is called from a ptrace_event()-safe context 584 - secure_computing return value is checked and a return value of -1 585 results in the system call being skipped immediately. 586 - seccomp syscall wired up 587 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 588 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 589 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 590 591config SECCOMP 592 prompt "Enable seccomp to safely execute untrusted bytecode" 593 def_bool y 594 depends on HAVE_ARCH_SECCOMP 595 help 596 This kernel feature is useful for number crunching applications 597 that may need to handle untrusted bytecode during their 598 execution. By using pipes or other transports made available 599 to the process as file descriptors supporting the read/write 600 syscalls, it's possible to isolate those applications in their 601 own address space using seccomp. Once seccomp is enabled via 602 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 603 disabled and the task is only allowed to execute a few safe 604 syscalls defined by each seccomp mode. 605 606 If unsure, say Y. 607 608config SECCOMP_FILTER 609 def_bool y 610 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 611 help 612 Enable tasks to build secure computing environments defined 613 in terms of Berkeley Packet Filter programs which implement 614 task-defined system call filtering polices. 615 616 See Documentation/userspace-api/seccomp_filter.rst for details. 617 618config SECCOMP_CACHE_DEBUG 619 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 620 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 621 depends on PROC_FS 622 help 623 This enables the /proc/pid/seccomp_cache interface to monitor 624 seccomp cache data. The file format is subject to change. Reading 625 the file requires CAP_SYS_ADMIN. 626 627 This option is for debugging only. Enabling presents the risk that 628 an adversary may be able to infer the seccomp filter logic. 629 630 If unsure, say N. 631 632config HAVE_ARCH_STACKLEAK 633 bool 634 help 635 An architecture should select this if it has the code which 636 fills the used part of the kernel stack with the STACKLEAK_POISON 637 value before returning from system calls. 638 639config HAVE_STACKPROTECTOR 640 bool 641 help 642 An arch should select this symbol if: 643 - it has implemented a stack canary (e.g. __stack_chk_guard) 644 645config STACKPROTECTOR 646 bool "Stack Protector buffer overflow detection" 647 depends on HAVE_STACKPROTECTOR 648 depends on $(cc-option,-fstack-protector) 649 default y 650 help 651 This option turns on the "stack-protector" GCC feature. This 652 feature puts, at the beginning of functions, a canary value on 653 the stack just before the return address, and validates 654 the value just before actually returning. Stack based buffer 655 overflows (that need to overwrite this return address) now also 656 overwrite the canary, which gets detected and the attack is then 657 neutralized via a kernel panic. 658 659 Functions will have the stack-protector canary logic added if they 660 have an 8-byte or larger character array on the stack. 661 662 This feature requires gcc version 4.2 or above, or a distribution 663 gcc with the feature backported ("-fstack-protector"). 664 665 On an x86 "defconfig" build, this feature adds canary checks to 666 about 3% of all kernel functions, which increases kernel code size 667 by about 0.3%. 668 669config STACKPROTECTOR_STRONG 670 bool "Strong Stack Protector" 671 depends on STACKPROTECTOR 672 depends on $(cc-option,-fstack-protector-strong) 673 default y 674 help 675 Functions will have the stack-protector canary logic added in any 676 of the following conditions: 677 678 - local variable's address used as part of the right hand side of an 679 assignment or function argument 680 - local variable is an array (or union containing an array), 681 regardless of array type or length 682 - uses register local variables 683 684 This feature requires gcc version 4.9 or above, or a distribution 685 gcc with the feature backported ("-fstack-protector-strong"). 686 687 On an x86 "defconfig" build, this feature adds canary checks to 688 about 20% of all kernel functions, which increases the kernel code 689 size by about 2%. 690 691config ARCH_SUPPORTS_SHADOW_CALL_STACK 692 bool 693 help 694 An architecture should select this if it supports the compiler's 695 Shadow Call Stack and implements runtime support for shadow stack 696 switching. 697 698config SHADOW_CALL_STACK 699 bool "Shadow Call Stack" 700 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 701 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 702 depends on MMU 703 help 704 This option enables the compiler's Shadow Call Stack, which 705 uses a shadow stack to protect function return addresses from 706 being overwritten by an attacker. More information can be found 707 in the compiler's documentation: 708 709 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 710 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 711 712 Note that security guarantees in the kernel differ from the 713 ones documented for user space. The kernel must store addresses 714 of shadow stacks in memory, which means an attacker capable of 715 reading and writing arbitrary memory may be able to locate them 716 and hijack control flow by modifying the stacks. 717 718config DYNAMIC_SCS 719 bool 720 help 721 Set by the arch code if it relies on code patching to insert the 722 shadow call stack push and pop instructions rather than on the 723 compiler. 724 725config LTO 726 bool 727 help 728 Selected if the kernel will be built using the compiler's LTO feature. 729 730config LTO_CLANG 731 bool 732 select LTO 733 help 734 Selected if the kernel will be built using Clang's LTO feature. 735 736config ARCH_SUPPORTS_LTO_CLANG 737 bool 738 help 739 An architecture should select this option if it supports: 740 - compiling with Clang, 741 - compiling inline assembly with Clang's integrated assembler, 742 - and linking with LLD. 743 744config ARCH_SUPPORTS_LTO_CLANG_THIN 745 bool 746 help 747 An architecture should select this option if it can support Clang's 748 ThinLTO mode. 749 750config HAS_LTO_CLANG 751 def_bool y 752 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 753 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 754 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 755 depends on ARCH_SUPPORTS_LTO_CLANG 756 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 757 # https://github.com/ClangBuiltLinux/linux/issues/1721 758 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO 759 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO 760 depends on !GCOV_KERNEL 761 help 762 The compiler and Kconfig options support building with Clang's 763 LTO. 764 765choice 766 prompt "Link Time Optimization (LTO)" 767 default LTO_NONE 768 help 769 This option enables Link Time Optimization (LTO), which allows the 770 compiler to optimize binaries globally. 771 772 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 773 so it's disabled by default. 774 775config LTO_NONE 776 bool "None" 777 help 778 Build the kernel normally, without Link Time Optimization (LTO). 779 780config LTO_CLANG_FULL 781 bool "Clang Full LTO (EXPERIMENTAL)" 782 depends on HAS_LTO_CLANG 783 depends on !COMPILE_TEST 784 select LTO_CLANG 785 help 786 This option enables Clang's full Link Time Optimization (LTO), which 787 allows the compiler to optimize the kernel globally. If you enable 788 this option, the compiler generates LLVM bitcode instead of ELF 789 object files, and the actual compilation from bitcode happens at 790 the LTO link step, which may take several minutes depending on the 791 kernel configuration. More information can be found from LLVM's 792 documentation: 793 794 https://llvm.org/docs/LinkTimeOptimization.html 795 796 During link time, this option can use a large amount of RAM, and 797 may take much longer than the ThinLTO option. 798 799config LTO_CLANG_THIN 800 bool "Clang ThinLTO (EXPERIMENTAL)" 801 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 802 select LTO_CLANG 803 help 804 This option enables Clang's ThinLTO, which allows for parallel 805 optimization and faster incremental compiles compared to the 806 CONFIG_LTO_CLANG_FULL option. More information can be found 807 from Clang's documentation: 808 809 https://clang.llvm.org/docs/ThinLTO.html 810 811 If unsure, say Y. 812endchoice 813 814config ARCH_SUPPORTS_AUTOFDO_CLANG 815 bool 816 817config AUTOFDO_CLANG 818 bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" 819 depends on ARCH_SUPPORTS_AUTOFDO_CLANG 820 depends on CC_IS_CLANG && CLANG_VERSION >= 170000 821 help 822 This option enables Clang’s AutoFDO build. When 823 an AutoFDO profile is specified in variable 824 CLANG_AUTOFDO_PROFILE during the build process, 825 Clang uses the profile to optimize the kernel. 826 827 If no profile is specified, AutoFDO options are 828 still passed to Clang to facilitate the collection 829 of perf data for creating an AutoFDO profile in 830 subsequent builds. 831 832 If unsure, say N. 833 834config ARCH_SUPPORTS_CFI_CLANG 835 bool 836 help 837 An architecture should select this option if it can support Clang's 838 Control-Flow Integrity (CFI) checking. 839 840config ARCH_USES_CFI_TRAPS 841 bool 842 843config CFI_CLANG 844 bool "Use Clang's Control Flow Integrity (CFI)" 845 depends on ARCH_SUPPORTS_CFI_CLANG 846 depends on $(cc-option,-fsanitize=kcfi) 847 help 848 This option enables Clang's forward-edge Control Flow Integrity 849 (CFI) checking, where the compiler injects a runtime check to each 850 indirect function call to ensure the target is a valid function with 851 the correct static type. This restricts possible call targets and 852 makes it more difficult for an attacker to exploit bugs that allow 853 the modification of stored function pointers. More information can be 854 found from Clang's documentation: 855 856 https://clang.llvm.org/docs/ControlFlowIntegrity.html 857 858config CFI_ICALL_NORMALIZE_INTEGERS 859 bool "Normalize CFI tags for integers" 860 depends on CFI_CLANG 861 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 862 help 863 This option normalizes the CFI tags for integer types so that all 864 integer types of the same size and signedness receive the same CFI 865 tag. 866 867 The option is separate from CONFIG_RUST because it affects the ABI. 868 When working with build systems that care about the ABI, it is 869 convenient to be able to turn on this flag first, before Rust is 870 turned on. 871 872 This option is necessary for using CFI with Rust. If unsure, say N. 873 874config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 875 def_bool y 876 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 877 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 878 # ANDROID: This version number has been changed due to backports in Android's compiler. 879 depends on CLANG_VERSION >= 190001 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 880 881config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 882 def_bool y 883 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 884 depends on RUSTC_VERSION >= 107900 885 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 886 # ANDROID: This version number has been changed due to backports in Android's compiler. 887 depends on (RUSTC_LLVM_VERSION >= 190001 && RUSTC_VERSION >= 108200) || \ 888 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 889 890config CFI_PERMISSIVE 891 bool "Use CFI in permissive mode" 892 depends on CFI_CLANG 893 help 894 When selected, Control Flow Integrity (CFI) violations result in a 895 warning instead of a kernel panic. This option should only be used 896 for finding indirect call type mismatches during development. 897 898 If unsure, say N. 899 900config HAVE_ARCH_WITHIN_STACK_FRAMES 901 bool 902 help 903 An architecture should select this if it can walk the kernel stack 904 frames to determine if an object is part of either the arguments 905 or local variables (i.e. that it excludes saved return addresses, 906 and similar) by implementing an inline arch_within_stack_frames(), 907 which is used by CONFIG_HARDENED_USERCOPY. 908 909config HAVE_CONTEXT_TRACKING_USER 910 bool 911 help 912 Provide kernel/user boundaries probes necessary for subsystems 913 that need it, such as userspace RCU extended quiescent state. 914 Syscalls need to be wrapped inside user_exit()-user_enter(), either 915 optimized behind static key or through the slow path using TIF_NOHZ 916 flag. Exceptions handlers must be wrapped as well. Irqs are already 917 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 918 handling on irq exit still need to be protected. 919 920config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 921 bool 922 help 923 Architecture neither relies on exception_enter()/exception_exit() 924 nor on schedule_user(). Also preempt_schedule_notrace() and 925 preempt_schedule_irq() can't be called in a preemptible section 926 while context tracking is CT_STATE_USER. This feature reflects a sane 927 entry implementation where the following requirements are met on 928 critical entry code, ie: before user_exit() or after user_enter(): 929 930 - Critical entry code isn't preemptible (or better yet: 931 not interruptible). 932 - No use of RCU read side critical sections, unless ct_nmi_enter() 933 got called. 934 - No use of instrumentation, unless instrumentation_begin() got 935 called. 936 937config HAVE_TIF_NOHZ 938 bool 939 help 940 Arch relies on TIF_NOHZ and syscall slow path to implement context 941 tracking calls to user_enter()/user_exit(). 942 943config HAVE_VIRT_CPU_ACCOUNTING 944 bool 945 946config HAVE_VIRT_CPU_ACCOUNTING_IDLE 947 bool 948 help 949 Architecture has its own way to account idle CPU time and therefore 950 doesn't implement vtime_account_idle(). 951 952config ARCH_HAS_SCALED_CPUTIME 953 bool 954 955config HAVE_VIRT_CPU_ACCOUNTING_GEN 956 bool 957 default y if 64BIT 958 help 959 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 960 Before enabling this option, arch code must be audited 961 to ensure there are no races in concurrent read/write of 962 cputime_t. For example, reading/writing 64-bit cputime_t on 963 some 32-bit arches may require multiple accesses, so proper 964 locking is needed to protect against concurrent accesses. 965 966config HAVE_IRQ_TIME_ACCOUNTING 967 bool 968 help 969 Archs need to ensure they use a high enough resolution clock to 970 support irq time accounting and then call enable_sched_clock_irqtime(). 971 972config HAVE_MOVE_PUD 973 bool 974 help 975 Architectures that select this are able to move page tables at the 976 PUD level. If there are only 3 page table levels, the move effectively 977 happens at the PGD level. 978 979config HAVE_MOVE_PMD 980 bool 981 help 982 Archs that select this are able to move page tables at the PMD level. 983 984config HAVE_ARCH_TRANSPARENT_HUGEPAGE 985 bool 986 987config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 988 bool 989 990config HAVE_ARCH_HUGE_VMAP 991 bool 992 993# 994# Archs that select this would be capable of PMD-sized vmaps (i.e., 995# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 996# must be used to enable allocations to use hugepages. 997# 998config HAVE_ARCH_HUGE_VMALLOC 999 depends on HAVE_ARCH_HUGE_VMAP 1000 bool 1001 1002config ARCH_WANT_HUGE_PMD_SHARE 1003 bool 1004 1005# Archs that want to use pmd_mkwrite on kernel memory need it defined even 1006# if there are no userspace memory management features that use it 1007config ARCH_WANT_KERNEL_PMD_MKWRITE 1008 bool 1009 1010config ARCH_WANT_PMD_MKWRITE 1011 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 1012 1013config HAVE_ARCH_SOFT_DIRTY 1014 bool 1015 1016config HAVE_MOD_ARCH_SPECIFIC 1017 bool 1018 help 1019 The arch uses struct mod_arch_specific to store data. Many arches 1020 just need a simple module loader without arch specific data - those 1021 should not enable this. 1022 1023config MODULES_USE_ELF_RELA 1024 bool 1025 help 1026 Modules only use ELF RELA relocations. Modules with ELF REL 1027 relocations will give an error. 1028 1029config MODULES_USE_ELF_REL 1030 bool 1031 help 1032 Modules only use ELF REL relocations. Modules with ELF RELA 1033 relocations will give an error. 1034 1035config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1036 bool 1037 help 1038 For architectures like powerpc/32 which have constraints on module 1039 allocation and need to allocate module data outside of module area. 1040 1041config ARCH_WANTS_EXECMEM_LATE 1042 bool 1043 help 1044 For architectures that do not allocate executable memory early on 1045 boot, but rather require its initialization late when there is 1046 enough entropy for module space randomization, for instance 1047 arm64. 1048 1049config HAVE_IRQ_EXIT_ON_IRQ_STACK 1050 bool 1051 help 1052 Architecture doesn't only execute the irq handler on the irq stack 1053 but also irq_exit(). This way we can process softirqs on this irq 1054 stack instead of switching to a new one when we call __do_softirq() 1055 in the end of an hardirq. 1056 This spares a stack switch and improves cache usage on softirq 1057 processing. 1058 1059config HAVE_SOFTIRQ_ON_OWN_STACK 1060 bool 1061 help 1062 Architecture provides a function to run __do_softirq() on a 1063 separate stack. 1064 1065config SOFTIRQ_ON_OWN_STACK 1066 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1067 1068config ALTERNATE_USER_ADDRESS_SPACE 1069 bool 1070 help 1071 Architectures set this when the CPU uses separate address 1072 spaces for kernel and user space pointers. In this case, the 1073 access_ok() check on a __user pointer is skipped. 1074 1075config PGTABLE_LEVELS 1076 int 1077 default 2 1078 1079config ARCH_HAS_ELF_RANDOMIZE 1080 bool 1081 help 1082 An architecture supports choosing randomized locations for 1083 stack, mmap, brk, and ET_DYN. Defined functions: 1084 - arch_mmap_rnd() 1085 - arch_randomize_brk() 1086 1087config HAVE_ARCH_MMAP_RND_BITS 1088 bool 1089 help 1090 An arch should select this symbol if it supports setting a variable 1091 number of bits for use in establishing the base address for mmap 1092 allocations, has MMU enabled and provides values for both: 1093 - ARCH_MMAP_RND_BITS_MIN 1094 - ARCH_MMAP_RND_BITS_MAX 1095 1096config HAVE_EXIT_THREAD 1097 bool 1098 help 1099 An architecture implements exit_thread. 1100 1101config ARCH_MMAP_RND_BITS_MIN 1102 int 1103 1104config ARCH_MMAP_RND_BITS_MAX 1105 int 1106 1107config ARCH_MMAP_RND_BITS_DEFAULT 1108 int 1109 1110config ARCH_MMAP_RND_BITS 1111 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1112 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1113 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1114 default ARCH_MMAP_RND_BITS_MIN 1115 depends on HAVE_ARCH_MMAP_RND_BITS 1116 help 1117 This value can be used to select the number of bits to use to 1118 determine the random offset to the base address of vma regions 1119 resulting from mmap allocations. This value will be bounded 1120 by the architecture's minimum and maximum supported values. 1121 1122 This value can be changed after boot using the 1123 /proc/sys/vm/mmap_rnd_bits tunable 1124 1125config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1126 bool 1127 help 1128 An arch should select this symbol if it supports running applications 1129 in compatibility mode, supports setting a variable number of bits for 1130 use in establishing the base address for mmap allocations, has MMU 1131 enabled and provides values for both: 1132 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1133 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1134 1135config ARCH_MMAP_RND_COMPAT_BITS_MIN 1136 int 1137 1138config ARCH_MMAP_RND_COMPAT_BITS_MAX 1139 int 1140 1141config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1142 int 1143 1144config ARCH_MMAP_RND_COMPAT_BITS 1145 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1146 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1147 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1148 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1149 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1150 help 1151 This value can be used to select the number of bits to use to 1152 determine the random offset to the base address of vma regions 1153 resulting from mmap allocations for compatible applications This 1154 value will be bounded by the architecture's minimum and maximum 1155 supported values. 1156 1157 This value can be changed after boot using the 1158 /proc/sys/vm/mmap_rnd_compat_bits tunable 1159 1160config HAVE_ARCH_COMPAT_MMAP_BASES 1161 bool 1162 help 1163 This allows 64bit applications to invoke 32-bit mmap() syscall 1164 and vice-versa 32-bit applications to call 64-bit mmap(). 1165 Required for applications doing different bitness syscalls. 1166 1167config HAVE_PAGE_SIZE_4KB 1168 bool 1169 1170config HAVE_PAGE_SIZE_8KB 1171 bool 1172 1173config HAVE_PAGE_SIZE_16KB 1174 bool 1175 1176config HAVE_PAGE_SIZE_32KB 1177 bool 1178 1179config HAVE_PAGE_SIZE_64KB 1180 bool 1181 1182config HAVE_PAGE_SIZE_256KB 1183 bool 1184 1185choice 1186 prompt "MMU page size" 1187 1188config PAGE_SIZE_4KB 1189 bool "4KiB pages" 1190 depends on HAVE_PAGE_SIZE_4KB 1191 help 1192 This option select the standard 4KiB Linux page size and the only 1193 available option on many architectures. Using 4KiB page size will 1194 minimize memory consumption and is therefore recommended for low 1195 memory systems. 1196 Some software that is written for x86 systems makes incorrect 1197 assumptions about the page size and only runs on 4KiB pages. 1198 1199config PAGE_SIZE_8KB 1200 bool "8KiB pages" 1201 depends on HAVE_PAGE_SIZE_8KB 1202 help 1203 This option is the only supported page size on a few older 1204 processors, and can be slightly faster than 4KiB pages. 1205 1206config PAGE_SIZE_16KB 1207 bool "16KiB pages" 1208 depends on HAVE_PAGE_SIZE_16KB 1209 help 1210 This option is usually a good compromise between memory 1211 consumption and performance for typical desktop and server 1212 workloads, often saving a level of page table lookups compared 1213 to 4KB pages as well as reducing TLB pressure and overhead of 1214 per-page operations in the kernel at the expense of a larger 1215 page cache. 1216 1217config PAGE_SIZE_32KB 1218 bool "32KiB pages" 1219 depends on HAVE_PAGE_SIZE_32KB 1220 help 1221 Using 32KiB page size will result in slightly higher performance 1222 kernel at the price of higher memory consumption compared to 1223 16KiB pages. This option is available only on cnMIPS cores. 1224 Note that you will need a suitable Linux distribution to 1225 support this. 1226 1227config PAGE_SIZE_64KB 1228 bool "64KiB pages" 1229 depends on HAVE_PAGE_SIZE_64KB 1230 help 1231 Using 64KiB page size will result in slightly higher performance 1232 kernel at the price of much higher memory consumption compared to 1233 4KiB or 16KiB pages. 1234 This is not suitable for general-purpose workloads but the 1235 better performance may be worth the cost for certain types of 1236 supercomputing or database applications that work mostly with 1237 large in-memory data rather than small files. 1238 1239config PAGE_SIZE_256KB 1240 bool "256KiB pages" 1241 depends on HAVE_PAGE_SIZE_256KB 1242 help 1243 256KiB pages have little practical value due to their extreme 1244 memory usage. The kernel will only be able to run applications 1245 that have been compiled with '-zmax-page-size' set to 256KiB 1246 (the default is 64KiB or 4KiB on most architectures). 1247 1248endchoice 1249 1250config PAGE_SIZE_LESS_THAN_64KB 1251 def_bool y 1252 depends on !PAGE_SIZE_64KB 1253 depends on PAGE_SIZE_LESS_THAN_256KB 1254 1255config PAGE_SIZE_LESS_THAN_256KB 1256 def_bool y 1257 depends on !PAGE_SIZE_256KB 1258 1259config PAGE_SHIFT 1260 int 1261 default 12 if PAGE_SIZE_4KB 1262 default 13 if PAGE_SIZE_8KB 1263 default 14 if PAGE_SIZE_16KB 1264 default 15 if PAGE_SIZE_32KB 1265 default 16 if PAGE_SIZE_64KB 1266 default 18 if PAGE_SIZE_256KB 1267 1268# This allows to use a set of generic functions to determine mmap base 1269# address by giving priority to top-down scheme only if the process 1270# is not in legacy mode (compat task, unlimited stack size or 1271# sysctl_legacy_va_layout). 1272# Architecture that selects this option can provide its own version of: 1273# - STACK_RND_MASK 1274config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1275 bool 1276 depends on MMU 1277 select ARCH_HAS_ELF_RANDOMIZE 1278 1279config HAVE_OBJTOOL 1280 bool 1281 1282config HAVE_JUMP_LABEL_HACK 1283 bool 1284 1285config HAVE_NOINSTR_HACK 1286 bool 1287 1288config HAVE_NOINSTR_VALIDATION 1289 bool 1290 1291config HAVE_UACCESS_VALIDATION 1292 bool 1293 select OBJTOOL 1294 1295config HAVE_STACK_VALIDATION 1296 bool 1297 help 1298 Architecture supports objtool compile-time frame pointer rule 1299 validation. 1300 1301config HAVE_RELIABLE_STACKTRACE 1302 bool 1303 help 1304 Architecture has either save_stack_trace_tsk_reliable() or 1305 arch_stack_walk_reliable() function which only returns a stack trace 1306 if it can guarantee the trace is reliable. 1307 1308config HAVE_ARCH_HASH 1309 bool 1310 default n 1311 help 1312 If this is set, the architecture provides an <asm/hash.h> 1313 file which provides platform-specific implementations of some 1314 functions in <linux/hash.h> or fs/namei.c. 1315 1316config HAVE_ARCH_NVRAM_OPS 1317 bool 1318 1319config ISA_BUS_API 1320 def_bool ISA 1321 1322# 1323# ABI hall of shame 1324# 1325config CLONE_BACKWARDS 1326 bool 1327 help 1328 Architecture has tls passed as the 4th argument of clone(2), 1329 not the 5th one. 1330 1331config CLONE_BACKWARDS2 1332 bool 1333 help 1334 Architecture has the first two arguments of clone(2) swapped. 1335 1336config CLONE_BACKWARDS3 1337 bool 1338 help 1339 Architecture has tls passed as the 3rd argument of clone(2), 1340 not the 5th one. 1341 1342config ODD_RT_SIGACTION 1343 bool 1344 help 1345 Architecture has unusual rt_sigaction(2) arguments 1346 1347config OLD_SIGSUSPEND 1348 bool 1349 help 1350 Architecture has old sigsuspend(2) syscall, of one-argument variety 1351 1352config OLD_SIGSUSPEND3 1353 bool 1354 help 1355 Even weirder antique ABI - three-argument sigsuspend(2) 1356 1357config OLD_SIGACTION 1358 bool 1359 help 1360 Architecture has old sigaction(2) syscall. Nope, not the same 1361 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1362 but fairly different variant of sigaction(2), thanks to OSF/1 1363 compatibility... 1364 1365config COMPAT_OLD_SIGACTION 1366 bool 1367 1368config COMPAT_32BIT_TIME 1369 bool "Provide system calls for 32-bit time_t" 1370 default !64BIT || COMPAT 1371 help 1372 This enables 32 bit time_t support in addition to 64 bit time_t support. 1373 This is relevant on all 32-bit architectures, and 64-bit architectures 1374 as part of compat syscall handling. 1375 1376config ARCH_NO_PREEMPT 1377 bool 1378 1379config ARCH_SUPPORTS_RT 1380 bool 1381 1382config CPU_NO_EFFICIENT_FFS 1383 def_bool n 1384 1385config HAVE_ARCH_VMAP_STACK 1386 def_bool n 1387 help 1388 An arch should select this symbol if it can support kernel stacks 1389 in vmalloc space. This means: 1390 1391 - vmalloc space must be large enough to hold many kernel stacks. 1392 This may rule out many 32-bit architectures. 1393 1394 - Stacks in vmalloc space need to work reliably. For example, if 1395 vmap page tables are created on demand, either this mechanism 1396 needs to work while the stack points to a virtual address with 1397 unpopulated page tables or arch code (switch_to() and switch_mm(), 1398 most likely) needs to ensure that the stack's page table entries 1399 are populated before running on a possibly unpopulated stack. 1400 1401 - If the stack overflows into a guard page, something reasonable 1402 should happen. The definition of "reasonable" is flexible, but 1403 instantly rebooting without logging anything would be unfriendly. 1404 1405config VMAP_STACK 1406 default y 1407 bool "Use a virtually-mapped stack" 1408 depends on HAVE_ARCH_VMAP_STACK 1409 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1410 help 1411 Enable this if you want the use virtually-mapped kernel stacks 1412 with guard pages. This causes kernel stack overflows to be 1413 caught immediately rather than causing difficult-to-diagnose 1414 corruption. 1415 1416 To use this with software KASAN modes, the architecture must support 1417 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1418 must be enabled. 1419 1420config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1421 def_bool n 1422 help 1423 An arch should select this symbol if it can support kernel stack 1424 offset randomization with calls to add_random_kstack_offset() 1425 during syscall entry and choose_random_kstack_offset() during 1426 syscall exit. Careful removal of -fstack-protector-strong and 1427 -fstack-protector should also be applied to the entry code and 1428 closely examined, as the artificial stack bump looks like an array 1429 to the compiler, so it will attempt to add canary checks regardless 1430 of the static branch state. 1431 1432config RANDOMIZE_KSTACK_OFFSET 1433 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1434 default y 1435 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1436 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1437 help 1438 The kernel stack offset can be randomized (after pt_regs) by 1439 roughly 5 bits of entropy, frustrating memory corruption 1440 attacks that depend on stack address determinism or 1441 cross-syscall address exposures. 1442 1443 The feature is controlled via the "randomize_kstack_offset=on/off" 1444 kernel boot param, and if turned off has zero overhead due to its use 1445 of static branches (see JUMP_LABEL). 1446 1447 If unsure, say Y. 1448 1449config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1450 bool "Default state of kernel stack offset randomization" 1451 depends on RANDOMIZE_KSTACK_OFFSET 1452 help 1453 Kernel stack offset randomization is controlled by kernel boot param 1454 "randomize_kstack_offset=on/off", and this config chooses the default 1455 boot state. 1456 1457config ARCH_OPTIONAL_KERNEL_RWX 1458 def_bool n 1459 1460config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1461 def_bool n 1462 1463config ARCH_HAS_STRICT_KERNEL_RWX 1464 def_bool n 1465 1466config STRICT_KERNEL_RWX 1467 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1468 depends on ARCH_HAS_STRICT_KERNEL_RWX 1469 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1470 help 1471 If this is set, kernel text and rodata memory will be made read-only, 1472 and non-text memory will be made non-executable. This provides 1473 protection against certain security exploits (e.g. executing the heap 1474 or modifying text) 1475 1476 These features are considered standard security practice these days. 1477 You should say Y here in almost all cases. 1478 1479config ARCH_HAS_STRICT_MODULE_RWX 1480 def_bool n 1481 1482config STRICT_MODULE_RWX 1483 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1484 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1485 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1486 help 1487 If this is set, module text and rodata memory will be made read-only, 1488 and non-text memory will be made non-executable. This provides 1489 protection against certain security exploits (e.g. writing to text) 1490 1491# select if the architecture provides an asm/dma-direct.h header 1492config ARCH_HAS_PHYS_TO_DMA 1493 bool 1494 1495config HAVE_ARCH_COMPILER_H 1496 bool 1497 help 1498 An architecture can select this if it provides an 1499 asm/compiler.h header that should be included after 1500 linux/compiler-*.h in order to override macro definitions that those 1501 headers generally provide. 1502 1503config HAVE_ARCH_PREL32_RELOCATIONS 1504 bool 1505 help 1506 May be selected by an architecture if it supports place-relative 1507 32-bit relocations, both in the toolchain and in the module loader, 1508 in which case relative references can be used in special sections 1509 for PCI fixup, initcalls etc which are only half the size on 64 bit 1510 architectures, and don't require runtime relocation on relocatable 1511 kernels. 1512 1513config ARCH_USE_MEMREMAP_PROT 1514 bool 1515 1516config LOCK_EVENT_COUNTS 1517 bool "Locking event counts collection" 1518 depends on DEBUG_FS 1519 help 1520 Enable light-weight counting of various locking related events 1521 in the system with minimal performance impact. This reduces 1522 the chance of application behavior change because of timing 1523 differences. The counts are reported via debugfs. 1524 1525# Select if the architecture has support for applying RELR relocations. 1526config ARCH_HAS_RELR 1527 bool 1528 1529config RELR 1530 bool "Use RELR relocation packing" 1531 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1532 default y 1533 help 1534 Store the kernel's dynamic relocations in the RELR relocation packing 1535 format. Requires a compatible linker (LLD supports this feature), as 1536 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1537 are compatible). 1538 1539config ARCH_HAS_MEM_ENCRYPT 1540 bool 1541 1542config ARCH_HAS_VIRTIO_BALLOON_HYP_OPS 1543 bool 1544 1545config ARCH_HAS_CC_PLATFORM 1546 bool 1547 1548config HAVE_SPARSE_SYSCALL_NR 1549 bool 1550 help 1551 An architecture should select this if its syscall numbering is sparse 1552 to save space. For example, MIPS architecture has a syscall array with 1553 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1554 related optimizations for a given architecture. 1555 1556config ARCH_HAS_VDSO_DATA 1557 bool 1558 1559config HAVE_STATIC_CALL 1560 bool 1561 1562config HAVE_STATIC_CALL_INLINE 1563 bool 1564 depends on HAVE_STATIC_CALL 1565 select OBJTOOL 1566 1567config HAVE_PREEMPT_DYNAMIC 1568 bool 1569 1570config HAVE_PREEMPT_DYNAMIC_CALL 1571 bool 1572 depends on HAVE_STATIC_CALL 1573 select HAVE_PREEMPT_DYNAMIC 1574 help 1575 An architecture should select this if it can handle the preemption 1576 model being selected at boot time using static calls. 1577 1578 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1579 preemption function will be patched directly. 1580 1581 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1582 call to a preemption function will go through a trampoline, and the 1583 trampoline will be patched. 1584 1585 It is strongly advised to support inline static call to avoid any 1586 overhead. 1587 1588config HAVE_PREEMPT_DYNAMIC_KEY 1589 bool 1590 depends on HAVE_ARCH_JUMP_LABEL 1591 select HAVE_PREEMPT_DYNAMIC 1592 help 1593 An architecture should select this if it can handle the preemption 1594 model being selected at boot time using static keys. 1595 1596 Each preemption function will be given an early return based on a 1597 static key. This should have slightly lower overhead than non-inline 1598 static calls, as this effectively inlines each trampoline into the 1599 start of its callee. This may avoid redundant work, and may 1600 integrate better with CFI schemes. 1601 1602 This will have greater overhead than using inline static calls as 1603 the call to the preemption function cannot be entirely elided. 1604 1605config ARCH_WANT_LD_ORPHAN_WARN 1606 bool 1607 help 1608 An arch should select this symbol once all linker sections are explicitly 1609 included, size-asserted, or discarded in the linker scripts. This is 1610 important because we never want expected sections to be placed heuristically 1611 by the linker, since the locations of such sections can change between linker 1612 versions. 1613 1614config HAVE_ARCH_PFN_VALID 1615 bool 1616 1617config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1618 bool 1619 1620config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1621 bool 1622 1623config ARCH_SPLIT_ARG64 1624 bool 1625 help 1626 If a 32-bit architecture requires 64-bit arguments to be split into 1627 pairs of 32-bit arguments, select this option. 1628 1629config ARCH_HAS_ELFCORE_COMPAT 1630 bool 1631 1632config ARCH_HAS_PARANOID_L1D_FLUSH 1633 bool 1634 1635config ARCH_HAVE_TRACE_MMIO_ACCESS 1636 bool 1637 1638config DYNAMIC_SIGFRAME 1639 bool 1640 1641# Select, if arch has a named attribute group bound to NUMA device nodes. 1642config HAVE_ARCH_NODE_DEV_GROUP 1643 bool 1644 1645config ARCH_HAS_HW_PTE_YOUNG 1646 bool 1647 help 1648 Architectures that select this option are capable of setting the 1649 accessed bit in PTE entries when using them as part of linear address 1650 translations. Architectures that require runtime check should select 1651 this option and override arch_has_hw_pte_young(). 1652 1653config ARCH_HAS_NONLEAF_PMD_YOUNG 1654 bool 1655 help 1656 Architectures that select this option are capable of setting the 1657 accessed bit in non-leaf PMD entries when using them as part of linear 1658 address translations. Page table walkers that clear the accessed bit 1659 may use this capability to reduce their search space. 1660 1661config ARCH_HAS_KERNEL_FPU_SUPPORT 1662 bool 1663 help 1664 Architectures that select this option can run floating-point code in 1665 the kernel, as described in Documentation/core-api/floating-point.rst. 1666 1667source "kernel/gcov/Kconfig" 1668 1669source "scripts/gcc-plugins/Kconfig" 1670 1671config FUNCTION_ALIGNMENT_4B 1672 bool 1673 1674config FUNCTION_ALIGNMENT_8B 1675 bool 1676 1677config FUNCTION_ALIGNMENT_16B 1678 bool 1679 1680config FUNCTION_ALIGNMENT_32B 1681 bool 1682 1683config FUNCTION_ALIGNMENT_64B 1684 bool 1685 1686config FUNCTION_ALIGNMENT 1687 int 1688 default 64 if FUNCTION_ALIGNMENT_64B 1689 default 32 if FUNCTION_ALIGNMENT_32B 1690 default 16 if FUNCTION_ALIGNMENT_16B 1691 default 8 if FUNCTION_ALIGNMENT_8B 1692 default 4 if FUNCTION_ALIGNMENT_4B 1693 default 0 1694 1695config CC_HAS_MIN_FUNCTION_ALIGNMENT 1696 # Detect availability of the GCC option -fmin-function-alignment which 1697 # guarantees minimal alignment for all functions, unlike 1698 # -falign-functions which the compiler ignores for cold functions. 1699 def_bool $(cc-option, -fmin-function-alignment=8) 1700 1701config CC_HAS_SANE_FUNCTION_ALIGNMENT 1702 # Set if the guaranteed alignment with -fmin-function-alignment is 1703 # available or extra care is required in the kernel. Clang provides 1704 # strict alignment always, even with -falign-functions. 1705 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1706 1707config ARCH_NEED_CMPXCHG_1_EMU 1708 bool 1709 1710endmenu 1711