1 # SPDX-License-Identifier: GPL-2.0 2 # 3 # General architecture dependent options 4 # 5 6 # 7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8 # override the default values in this file. 9 # 10 source "arch/$(SRCARCH)/Kconfig" 11 12 config ARCH_CONFIGURES_CPU_MITIGATIONS 13 bool 14 15 if !ARCH_CONFIGURES_CPU_MITIGATIONS 16 config CPU_MITIGATIONS 17 def_bool y 18 endif 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 # 24 config ARCH_HAS_DMA_OPS 25 depends on HAS_DMA 26 select DMA_OPS_HELPERS 27 bool 28 29 menu "General architecture-dependent options" 30 31 config 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 38 config HOTPLUG_SMT 39 bool 40 41 config SMT_NUM_THREADS_DYNAMIC 42 bool 43 44 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL 45 config HOTPLUG_CORE_SYNC 46 bool 47 48 # Basic CPU dead synchronization selected by architecture 49 config HOTPLUG_CORE_SYNC_DEAD 50 bool 51 select HOTPLUG_CORE_SYNC 52 53 # Full CPU synchronization with alive state selected by architecture 54 config HOTPLUG_CORE_SYNC_FULL 55 bool 56 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU 57 select HOTPLUG_CORE_SYNC 58 59 config HOTPLUG_SPLIT_STARTUP 60 bool 61 select HOTPLUG_CORE_SYNC_FULL 62 63 config HOTPLUG_PARALLEL 64 bool 65 select HOTPLUG_SPLIT_STARTUP 66 67 config GENERIC_ENTRY 68 bool 69 70 config 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 83 config 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. ) 108 109 config 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. 114 115 config 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. 120 121 config OPTPROBES 122 def_bool y 123 depends on KPROBES && HAVE_OPTPROBES 124 select NEED_TASKS_RCU 125 126 config 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. 134 135 config 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. ) 148 149 config 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. 164 165 config 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. 183 184 config 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. 202 203 config KRETPROBES 204 def_bool y 205 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 206 207 config KRETPROBE_ON_RETHOOK 208 def_bool y 209 depends on HAVE_RETHOOK 210 depends on KRETPROBES 211 select RETHOOK 212 213 config 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. 219 220 config HAVE_IOREMAP_PROT 221 bool 222 223 config HAVE_KPROBES 224 bool 225 226 config HAVE_KRETPROBES 227 bool 228 229 config HAVE_OPTPROBES 230 bool 231 232 config HAVE_KPROBES_ON_FTRACE 233 bool 234 235 config 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. 242 243 config HAVE_FUNCTION_ERROR_INJECTION 244 bool 245 246 config HAVE_NMI 247 bool 248 249 config HAVE_FUNCTION_DESCRIPTORS 250 bool 251 252 config TRACE_IRQFLAGS_SUPPORT 253 bool 254 255 config 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 # 270 config HAVE_ARCH_TRACEHOOK 271 bool 272 273 config HAVE_DMA_CONTIGUOUS 274 bool 275 276 config GENERIC_SMP_IDLE_THREAD 277 bool 278 279 config GENERIC_IDLE_POLL_SETUP 280 bool 281 282 config 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 # 292 config ARCH_HAS_KEEPINITRD 293 bool 294 295 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 296 config ARCH_HAS_SET_MEMORY 297 bool 298 299 # Select if arch has all set_direct_map_invalid/default() functions 300 config 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 # 308 config 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 # 315 config ARCH_HAS_DMA_CLEAR_UNCACHED 316 bool 317 318 config ARCH_HAS_CPU_FINALIZE_INIT 319 bool 320 321 # The architecture has a per-task state that includes the mm's PASID 322 config ARCH_HAS_CPU_PASID 323 bool 324 select IOMMU_MM_DATA 325 326 config 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: 337 config ARCH_WANTS_DYNAMIC_TASK_STRUCT 338 bool 339 340 config 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. 346 347 config 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 358 config ARCH_32BIT_USTAT_F_TINODE 359 bool 360 361 config 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. 367 368 config 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. 375 376 config 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. 382 383 config HAVE_RUST 384 bool 385 help 386 This symbol should be selected by an architecture if it 387 supports Rust. 388 389 config 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 395 396 config HAVE_HW_BREAKPOINT 397 bool 398 depends on PERF_EVENTS 399 400 config 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. 410 411 config HAVE_USER_RETURN_NOTIFIER 412 bool 413 414 config 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. 420 421 config 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. 427 428 config 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. 436 437 config 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. 442 443 config 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. 449 450 config HAVE_ARCH_JUMP_LABEL 451 bool 452 453 config HAVE_ARCH_JUMP_LABEL_RELATIVE 454 bool 455 456 config MMU_GATHER_TABLE_FREE 457 bool 458 459 config MMU_GATHER_RCU_TABLE_FREE 460 bool 461 select MMU_GATHER_TABLE_FREE 462 463 config MMU_GATHER_PAGE_SIZE 464 bool 465 466 config MMU_GATHER_NO_RANGE 467 bool 468 select MMU_GATHER_MERGE_VMAS 469 470 config MMU_GATHER_NO_FLUSH_CACHE 471 bool 472 473 config MMU_GATHER_MERGE_VMAS 474 bool 475 476 config MMU_GATHER_NO_GATHER 477 bool 478 depends on MMU_GATHER_TABLE_FREE 479 480 config 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). 501 config 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). 516 config MMU_LAZY_TLB_SHOOTDOWN 517 bool 518 519 config ARCH_HAVE_NMI_SAFE_CMPXCHG 520 bool 521 522 config 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. 530 531 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 532 bool 533 534 config 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. 541 542 config HAVE_CMPXCHG_LOCAL 543 bool 544 545 config HAVE_CMPXCHG_DOUBLE 546 bool 547 548 config ARCH_WEAK_RELEASE_ACQUIRE 549 bool 550 551 config ARCH_WANT_IPC_PARSE_VERSION 552 bool 553 554 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 555 bool 556 557 config ARCH_WANT_OLD_COMPAT_IPC 558 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 559 bool 560 561 config 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_32 571 572 config 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. 590 591 config 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. 607 608 config 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. 617 618 config 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. 631 632 config 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. 638 639 config 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) 644 645 config 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%. 668 669 config 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%. 690 691 config 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. 697 698 config 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. 717 718 config 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. 724 725 config LTO 726 bool 727 help 728 Selected if the kernel will be built using the compiler's LTO feature. 729 730 config LTO_CLANG 731 bool 732 select LTO 733 help 734 Selected if the kernel will be built using Clang's LTO feature. 735 736 config 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. 743 744 config 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. 749 750 config 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. 764 765 choice 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. 774 775 config LTO_NONE 776 bool "None" 777 help 778 Build the kernel normally, without Link Time Optimization (LTO). 779 780 config 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. 798 799 config 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. 812 endchoice 813 814 config ARCH_SUPPORTS_CFI_CLANG 815 bool 816 help 817 An architecture should select this option if it can support Clang's 818 Control-Flow Integrity (CFI) checking. 819 820 config ARCH_USES_CFI_TRAPS 821 bool 822 823 config CFI_CLANG 824 bool "Use Clang's Control Flow Integrity (CFI)" 825 depends on ARCH_SUPPORTS_CFI_CLANG 826 depends on $(cc-option,-fsanitize=kcfi) 827 help 828 This option enables Clang's forward-edge Control Flow Integrity 829 (CFI) checking, where the compiler injects a runtime check to each 830 indirect function call to ensure the target is a valid function with 831 the correct static type. This restricts possible call targets and 832 makes it more difficult for an attacker to exploit bugs that allow 833 the modification of stored function pointers. More information can be 834 found from Clang's documentation: 835 836 https://clang.llvm.org/docs/ControlFlowIntegrity.html 837 838 config CFI_ICALL_NORMALIZE_INTEGERS 839 bool "Normalize CFI tags for integers" 840 depends on CFI_CLANG 841 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 842 help 843 This option normalizes the CFI tags for integer types so that all 844 integer types of the same size and signedness receive the same CFI 845 tag. 846 847 The option is separate from CONFIG_RUST because it affects the ABI. 848 When working with build systems that care about the ABI, it is 849 convenient to be able to turn on this flag first, before Rust is 850 turned on. 851 852 This option is necessary for using CFI with Rust. If unsure, say N. 853 854 config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 855 def_bool y 856 depends on $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) 857 # With GCOV/KASAN we need this fix: https://github.com/llvm/llvm-project/pull/104826 858 depends on CLANG_VERSION >= 190103 || (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 859 860 config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC 861 def_bool y 862 depends on HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG 863 depends on RUSTC_VERSION >= 107900 864 # With GCOV/KASAN we need this fix: https://github.com/rust-lang/rust/pull/129373 865 depends on (RUSTC_LLVM_VERSION >= 190103 && RUSTC_VERSION >= 108200) || \ 866 (!GCOV_KERNEL && !KASAN_GENERIC && !KASAN_SW_TAGS) 867 868 config CFI_PERMISSIVE 869 bool "Use CFI in permissive mode" 870 depends on CFI_CLANG 871 help 872 When selected, Control Flow Integrity (CFI) violations result in a 873 warning instead of a kernel panic. This option should only be used 874 for finding indirect call type mismatches during development. 875 876 If unsure, say N. 877 878 config HAVE_ARCH_WITHIN_STACK_FRAMES 879 bool 880 help 881 An architecture should select this if it can walk the kernel stack 882 frames to determine if an object is part of either the arguments 883 or local variables (i.e. that it excludes saved return addresses, 884 and similar) by implementing an inline arch_within_stack_frames(), 885 which is used by CONFIG_HARDENED_USERCOPY. 886 887 config HAVE_CONTEXT_TRACKING_USER 888 bool 889 help 890 Provide kernel/user boundaries probes necessary for subsystems 891 that need it, such as userspace RCU extended quiescent state. 892 Syscalls need to be wrapped inside user_exit()-user_enter(), either 893 optimized behind static key or through the slow path using TIF_NOHZ 894 flag. Exceptions handlers must be wrapped as well. Irqs are already 895 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal 896 handling on irq exit still need to be protected. 897 898 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 899 bool 900 help 901 Architecture neither relies on exception_enter()/exception_exit() 902 nor on schedule_user(). Also preempt_schedule_notrace() and 903 preempt_schedule_irq() can't be called in a preemptible section 904 while context tracking is CT_STATE_USER. This feature reflects a sane 905 entry implementation where the following requirements are met on 906 critical entry code, ie: before user_exit() or after user_enter(): 907 908 - Critical entry code isn't preemptible (or better yet: 909 not interruptible). 910 - No use of RCU read side critical sections, unless ct_nmi_enter() 911 got called. 912 - No use of instrumentation, unless instrumentation_begin() got 913 called. 914 915 config HAVE_TIF_NOHZ 916 bool 917 help 918 Arch relies on TIF_NOHZ and syscall slow path to implement context 919 tracking calls to user_enter()/user_exit(). 920 921 config HAVE_VIRT_CPU_ACCOUNTING 922 bool 923 924 config HAVE_VIRT_CPU_ACCOUNTING_IDLE 925 bool 926 help 927 Architecture has its own way to account idle CPU time and therefore 928 doesn't implement vtime_account_idle(). 929 930 config ARCH_HAS_SCALED_CPUTIME 931 bool 932 933 config HAVE_VIRT_CPU_ACCOUNTING_GEN 934 bool 935 default y if 64BIT 936 help 937 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 938 Before enabling this option, arch code must be audited 939 to ensure there are no races in concurrent read/write of 940 cputime_t. For example, reading/writing 64-bit cputime_t on 941 some 32-bit arches may require multiple accesses, so proper 942 locking is needed to protect against concurrent accesses. 943 944 config HAVE_IRQ_TIME_ACCOUNTING 945 bool 946 help 947 Archs need to ensure they use a high enough resolution clock to 948 support irq time accounting and then call enable_sched_clock_irqtime(). 949 950 config HAVE_MOVE_PUD 951 bool 952 help 953 Architectures that select this are able to move page tables at the 954 PUD level. If there are only 3 page table levels, the move effectively 955 happens at the PGD level. 956 957 config HAVE_MOVE_PMD 958 bool 959 help 960 Archs that select this are able to move page tables at the PMD level. 961 962 config HAVE_ARCH_TRANSPARENT_HUGEPAGE 963 bool 964 965 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 966 bool 967 968 config HAVE_ARCH_HUGE_VMAP 969 bool 970 971 # 972 # Archs that select this would be capable of PMD-sized vmaps (i.e., 973 # arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 974 # must be used to enable allocations to use hugepages. 975 # 976 config HAVE_ARCH_HUGE_VMALLOC 977 depends on HAVE_ARCH_HUGE_VMAP 978 bool 979 980 config ARCH_WANT_HUGE_PMD_SHARE 981 bool 982 983 # Archs that want to use pmd_mkwrite on kernel memory need it defined even 984 # if there are no userspace memory management features that use it 985 config ARCH_WANT_KERNEL_PMD_MKWRITE 986 bool 987 988 config ARCH_WANT_PMD_MKWRITE 989 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE 990 991 config HAVE_ARCH_SOFT_DIRTY 992 bool 993 994 config HAVE_MOD_ARCH_SPECIFIC 995 bool 996 help 997 The arch uses struct mod_arch_specific to store data. Many arches 998 just need a simple module loader without arch specific data - those 999 should not enable this. 1000 1001 config MODULES_USE_ELF_RELA 1002 bool 1003 help 1004 Modules only use ELF RELA relocations. Modules with ELF REL 1005 relocations will give an error. 1006 1007 config MODULES_USE_ELF_REL 1008 bool 1009 help 1010 Modules only use ELF REL relocations. Modules with ELF RELA 1011 relocations will give an error. 1012 1013 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 1014 bool 1015 help 1016 For architectures like powerpc/32 which have constraints on module 1017 allocation and need to allocate module data outside of module area. 1018 1019 config ARCH_WANTS_EXECMEM_LATE 1020 bool 1021 help 1022 For architectures that do not allocate executable memory early on 1023 boot, but rather require its initialization late when there is 1024 enough entropy for module space randomization, for instance 1025 arm64. 1026 1027 config HAVE_IRQ_EXIT_ON_IRQ_STACK 1028 bool 1029 help 1030 Architecture doesn't only execute the irq handler on the irq stack 1031 but also irq_exit(). This way we can process softirqs on this irq 1032 stack instead of switching to a new one when we call __do_softirq() 1033 in the end of an hardirq. 1034 This spares a stack switch and improves cache usage on softirq 1035 processing. 1036 1037 config HAVE_SOFTIRQ_ON_OWN_STACK 1038 bool 1039 help 1040 Architecture provides a function to run __do_softirq() on a 1041 separate stack. 1042 1043 config SOFTIRQ_ON_OWN_STACK 1044 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT 1045 1046 config ALTERNATE_USER_ADDRESS_SPACE 1047 bool 1048 help 1049 Architectures set this when the CPU uses separate address 1050 spaces for kernel and user space pointers. In this case, the 1051 access_ok() check on a __user pointer is skipped. 1052 1053 config PGTABLE_LEVELS 1054 int 1055 default 2 1056 1057 config ARCH_HAS_ELF_RANDOMIZE 1058 bool 1059 help 1060 An architecture supports choosing randomized locations for 1061 stack, mmap, brk, and ET_DYN. Defined functions: 1062 - arch_mmap_rnd() 1063 - arch_randomize_brk() 1064 1065 config HAVE_ARCH_MMAP_RND_BITS 1066 bool 1067 help 1068 An arch should select this symbol if it supports setting a variable 1069 number of bits for use in establishing the base address for mmap 1070 allocations, has MMU enabled and provides values for both: 1071 - ARCH_MMAP_RND_BITS_MIN 1072 - ARCH_MMAP_RND_BITS_MAX 1073 1074 config HAVE_EXIT_THREAD 1075 bool 1076 help 1077 An architecture implements exit_thread. 1078 1079 config ARCH_MMAP_RND_BITS_MIN 1080 int 1081 1082 config ARCH_MMAP_RND_BITS_MAX 1083 int 1084 1085 config ARCH_MMAP_RND_BITS_DEFAULT 1086 int 1087 1088 config ARCH_MMAP_RND_BITS 1089 int "Number of bits to use for ASLR of mmap base address" if EXPERT 1090 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 1091 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 1092 default ARCH_MMAP_RND_BITS_MIN 1093 depends on HAVE_ARCH_MMAP_RND_BITS 1094 help 1095 This value can be used to select the number of bits to use to 1096 determine the random offset to the base address of vma regions 1097 resulting from mmap allocations. This value will be bounded 1098 by the architecture's minimum and maximum supported values. 1099 1100 This value can be changed after boot using the 1101 /proc/sys/vm/mmap_rnd_bits tunable 1102 1103 config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1104 bool 1105 help 1106 An arch should select this symbol if it supports running applications 1107 in compatibility mode, supports setting a variable number of bits for 1108 use in establishing the base address for mmap allocations, has MMU 1109 enabled and provides values for both: 1110 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1111 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1112 1113 config ARCH_MMAP_RND_COMPAT_BITS_MIN 1114 int 1115 1116 config ARCH_MMAP_RND_COMPAT_BITS_MAX 1117 int 1118 1119 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1120 int 1121 1122 config ARCH_MMAP_RND_COMPAT_BITS 1123 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 1124 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 1125 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1126 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1127 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 1128 help 1129 This value can be used to select the number of bits to use to 1130 determine the random offset to the base address of vma regions 1131 resulting from mmap allocations for compatible applications This 1132 value will be bounded by the architecture's minimum and maximum 1133 supported values. 1134 1135 This value can be changed after boot using the 1136 /proc/sys/vm/mmap_rnd_compat_bits tunable 1137 1138 config HAVE_ARCH_COMPAT_MMAP_BASES 1139 bool 1140 help 1141 This allows 64bit applications to invoke 32-bit mmap() syscall 1142 and vice-versa 32-bit applications to call 64-bit mmap(). 1143 Required for applications doing different bitness syscalls. 1144 1145 config HAVE_PAGE_SIZE_4KB 1146 bool 1147 1148 config HAVE_PAGE_SIZE_8KB 1149 bool 1150 1151 config HAVE_PAGE_SIZE_16KB 1152 bool 1153 1154 config HAVE_PAGE_SIZE_32KB 1155 bool 1156 1157 config HAVE_PAGE_SIZE_64KB 1158 bool 1159 1160 config HAVE_PAGE_SIZE_256KB 1161 bool 1162 1163 choice 1164 prompt "MMU page size" 1165 1166 config PAGE_SIZE_4KB 1167 bool "4KiB pages" 1168 depends on HAVE_PAGE_SIZE_4KB 1169 help 1170 This option select the standard 4KiB Linux page size and the only 1171 available option on many architectures. Using 4KiB page size will 1172 minimize memory consumption and is therefore recommended for low 1173 memory systems. 1174 Some software that is written for x86 systems makes incorrect 1175 assumptions about the page size and only runs on 4KiB pages. 1176 1177 config PAGE_SIZE_8KB 1178 bool "8KiB pages" 1179 depends on HAVE_PAGE_SIZE_8KB 1180 help 1181 This option is the only supported page size on a few older 1182 processors, and can be slightly faster than 4KiB pages. 1183 1184 config PAGE_SIZE_16KB 1185 bool "16KiB pages" 1186 depends on HAVE_PAGE_SIZE_16KB 1187 help 1188 This option is usually a good compromise between memory 1189 consumption and performance for typical desktop and server 1190 workloads, often saving a level of page table lookups compared 1191 to 4KB pages as well as reducing TLB pressure and overhead of 1192 per-page operations in the kernel at the expense of a larger 1193 page cache. 1194 1195 config PAGE_SIZE_32KB 1196 bool "32KiB pages" 1197 depends on HAVE_PAGE_SIZE_32KB 1198 help 1199 Using 32KiB page size will result in slightly higher performance 1200 kernel at the price of higher memory consumption compared to 1201 16KiB pages. This option is available only on cnMIPS cores. 1202 Note that you will need a suitable Linux distribution to 1203 support this. 1204 1205 config PAGE_SIZE_64KB 1206 bool "64KiB pages" 1207 depends on HAVE_PAGE_SIZE_64KB 1208 help 1209 Using 64KiB page size will result in slightly higher performance 1210 kernel at the price of much higher memory consumption compared to 1211 4KiB or 16KiB pages. 1212 This is not suitable for general-purpose workloads but the 1213 better performance may be worth the cost for certain types of 1214 supercomputing or database applications that work mostly with 1215 large in-memory data rather than small files. 1216 1217 config PAGE_SIZE_256KB 1218 bool "256KiB pages" 1219 depends on HAVE_PAGE_SIZE_256KB 1220 help 1221 256KiB pages have little practical value due to their extreme 1222 memory usage. The kernel will only be able to run applications 1223 that have been compiled with '-zmax-page-size' set to 256KiB 1224 (the default is 64KiB or 4KiB on most architectures). 1225 1226 endchoice 1227 1228 config PAGE_SIZE_LESS_THAN_64KB 1229 def_bool y 1230 depends on !PAGE_SIZE_64KB 1231 depends on PAGE_SIZE_LESS_THAN_256KB 1232 1233 config PAGE_SIZE_LESS_THAN_256KB 1234 def_bool y 1235 depends on !PAGE_SIZE_256KB 1236 1237 config PAGE_SHIFT 1238 int 1239 default 12 if PAGE_SIZE_4KB 1240 default 13 if PAGE_SIZE_8KB 1241 default 14 if PAGE_SIZE_16KB 1242 default 15 if PAGE_SIZE_32KB 1243 default 16 if PAGE_SIZE_64KB 1244 default 18 if PAGE_SIZE_256KB 1245 1246 # This allows to use a set of generic functions to determine mmap base 1247 # address by giving priority to top-down scheme only if the process 1248 # is not in legacy mode (compat task, unlimited stack size or 1249 # sysctl_legacy_va_layout). 1250 # Architecture that selects this option can provide its own version of: 1251 # - STACK_RND_MASK 1252 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1253 bool 1254 depends on MMU 1255 select ARCH_HAS_ELF_RANDOMIZE 1256 1257 config HAVE_OBJTOOL 1258 bool 1259 1260 config HAVE_JUMP_LABEL_HACK 1261 bool 1262 1263 config HAVE_NOINSTR_HACK 1264 bool 1265 1266 config HAVE_NOINSTR_VALIDATION 1267 bool 1268 1269 config HAVE_UACCESS_VALIDATION 1270 bool 1271 select OBJTOOL 1272 1273 config HAVE_STACK_VALIDATION 1274 bool 1275 help 1276 Architecture supports objtool compile-time frame pointer rule 1277 validation. 1278 1279 config HAVE_RELIABLE_STACKTRACE 1280 bool 1281 help 1282 Architecture has either save_stack_trace_tsk_reliable() or 1283 arch_stack_walk_reliable() function which only returns a stack trace 1284 if it can guarantee the trace is reliable. 1285 1286 config HAVE_ARCH_HASH 1287 bool 1288 default n 1289 help 1290 If this is set, the architecture provides an <asm/hash.h> 1291 file which provides platform-specific implementations of some 1292 functions in <linux/hash.h> or fs/namei.c. 1293 1294 config HAVE_ARCH_NVRAM_OPS 1295 bool 1296 1297 config ISA_BUS_API 1298 def_bool ISA 1299 1300 # 1301 # ABI hall of shame 1302 # 1303 config CLONE_BACKWARDS 1304 bool 1305 help 1306 Architecture has tls passed as the 4th argument of clone(2), 1307 not the 5th one. 1308 1309 config CLONE_BACKWARDS2 1310 bool 1311 help 1312 Architecture has the first two arguments of clone(2) swapped. 1313 1314 config CLONE_BACKWARDS3 1315 bool 1316 help 1317 Architecture has tls passed as the 3rd argument of clone(2), 1318 not the 5th one. 1319 1320 config ODD_RT_SIGACTION 1321 bool 1322 help 1323 Architecture has unusual rt_sigaction(2) arguments 1324 1325 config OLD_SIGSUSPEND 1326 bool 1327 help 1328 Architecture has old sigsuspend(2) syscall, of one-argument variety 1329 1330 config OLD_SIGSUSPEND3 1331 bool 1332 help 1333 Even weirder antique ABI - three-argument sigsuspend(2) 1334 1335 config OLD_SIGACTION 1336 bool 1337 help 1338 Architecture has old sigaction(2) syscall. Nope, not the same 1339 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1340 but fairly different variant of sigaction(2), thanks to OSF/1 1341 compatibility... 1342 1343 config COMPAT_OLD_SIGACTION 1344 bool 1345 1346 config COMPAT_32BIT_TIME 1347 bool "Provide system calls for 32-bit time_t" 1348 default !64BIT || COMPAT 1349 help 1350 This enables 32 bit time_t support in addition to 64 bit time_t support. 1351 This is relevant on all 32-bit architectures, and 64-bit architectures 1352 as part of compat syscall handling. 1353 1354 config ARCH_NO_PREEMPT 1355 bool 1356 1357 config ARCH_SUPPORTS_RT 1358 bool 1359 1360 config CPU_NO_EFFICIENT_FFS 1361 def_bool n 1362 1363 config HAVE_ARCH_VMAP_STACK 1364 def_bool n 1365 help 1366 An arch should select this symbol if it can support kernel stacks 1367 in vmalloc space. This means: 1368 1369 - vmalloc space must be large enough to hold many kernel stacks. 1370 This may rule out many 32-bit architectures. 1371 1372 - Stacks in vmalloc space need to work reliably. For example, if 1373 vmap page tables are created on demand, either this mechanism 1374 needs to work while the stack points to a virtual address with 1375 unpopulated page tables or arch code (switch_to() and switch_mm(), 1376 most likely) needs to ensure that the stack's page table entries 1377 are populated before running on a possibly unpopulated stack. 1378 1379 - If the stack overflows into a guard page, something reasonable 1380 should happen. The definition of "reasonable" is flexible, but 1381 instantly rebooting without logging anything would be unfriendly. 1382 1383 config VMAP_STACK 1384 default y 1385 bool "Use a virtually-mapped stack" 1386 depends on HAVE_ARCH_VMAP_STACK 1387 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1388 help 1389 Enable this if you want the use virtually-mapped kernel stacks 1390 with guard pages. This causes kernel stack overflows to be 1391 caught immediately rather than causing difficult-to-diagnose 1392 corruption. 1393 1394 To use this with software KASAN modes, the architecture must support 1395 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1396 must be enabled. 1397 1398 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1399 def_bool n 1400 help 1401 An arch should select this symbol if it can support kernel stack 1402 offset randomization with calls to add_random_kstack_offset() 1403 during syscall entry and choose_random_kstack_offset() during 1404 syscall exit. Careful removal of -fstack-protector-strong and 1405 -fstack-protector should also be applied to the entry code and 1406 closely examined, as the artificial stack bump looks like an array 1407 to the compiler, so it will attempt to add canary checks regardless 1408 of the static branch state. 1409 1410 config RANDOMIZE_KSTACK_OFFSET 1411 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1412 default y 1413 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1414 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1415 help 1416 The kernel stack offset can be randomized (after pt_regs) by 1417 roughly 5 bits of entropy, frustrating memory corruption 1418 attacks that depend on stack address determinism or 1419 cross-syscall address exposures. 1420 1421 The feature is controlled via the "randomize_kstack_offset=on/off" 1422 kernel boot param, and if turned off has zero overhead due to its use 1423 of static branches (see JUMP_LABEL). 1424 1425 If unsure, say Y. 1426 1427 config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1428 bool "Default state of kernel stack offset randomization" 1429 depends on RANDOMIZE_KSTACK_OFFSET 1430 help 1431 Kernel stack offset randomization is controlled by kernel boot param 1432 "randomize_kstack_offset=on/off", and this config chooses the default 1433 boot state. 1434 1435 config ARCH_OPTIONAL_KERNEL_RWX 1436 def_bool n 1437 1438 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1439 def_bool n 1440 1441 config ARCH_HAS_STRICT_KERNEL_RWX 1442 def_bool n 1443 1444 config STRICT_KERNEL_RWX 1445 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1446 depends on ARCH_HAS_STRICT_KERNEL_RWX 1447 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1448 help 1449 If this is set, kernel text and rodata memory will be made read-only, 1450 and non-text memory will be made non-executable. This provides 1451 protection against certain security exploits (e.g. executing the heap 1452 or modifying text) 1453 1454 These features are considered standard security practice these days. 1455 You should say Y here in almost all cases. 1456 1457 config ARCH_HAS_STRICT_MODULE_RWX 1458 def_bool n 1459 1460 config STRICT_MODULE_RWX 1461 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1462 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1463 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1464 help 1465 If this is set, module text and rodata memory will be made read-only, 1466 and non-text memory will be made non-executable. This provides 1467 protection against certain security exploits (e.g. writing to text) 1468 1469 # select if the architecture provides an asm/dma-direct.h header 1470 config ARCH_HAS_PHYS_TO_DMA 1471 bool 1472 1473 config HAVE_ARCH_COMPILER_H 1474 bool 1475 help 1476 An architecture can select this if it provides an 1477 asm/compiler.h header that should be included after 1478 linux/compiler-*.h in order to override macro definitions that those 1479 headers generally provide. 1480 1481 config HAVE_ARCH_PREL32_RELOCATIONS 1482 bool 1483 help 1484 May be selected by an architecture if it supports place-relative 1485 32-bit relocations, both in the toolchain and in the module loader, 1486 in which case relative references can be used in special sections 1487 for PCI fixup, initcalls etc which are only half the size on 64 bit 1488 architectures, and don't require runtime relocation on relocatable 1489 kernels. 1490 1491 config ARCH_USE_MEMREMAP_PROT 1492 bool 1493 1494 config LOCK_EVENT_COUNTS 1495 bool "Locking event counts collection" 1496 depends on DEBUG_FS 1497 help 1498 Enable light-weight counting of various locking related events 1499 in the system with minimal performance impact. This reduces 1500 the chance of application behavior change because of timing 1501 differences. The counts are reported via debugfs. 1502 1503 # Select if the architecture has support for applying RELR relocations. 1504 config ARCH_HAS_RELR 1505 bool 1506 1507 config RELR 1508 bool "Use RELR relocation packing" 1509 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1510 default y 1511 help 1512 Store the kernel's dynamic relocations in the RELR relocation packing 1513 format. Requires a compatible linker (LLD supports this feature), as 1514 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1515 are compatible). 1516 1517 config ARCH_HAS_MEM_ENCRYPT 1518 bool 1519 1520 config ARCH_HAS_CC_PLATFORM 1521 bool 1522 1523 config HAVE_SPARSE_SYSCALL_NR 1524 bool 1525 help 1526 An architecture should select this if its syscall numbering is sparse 1527 to save space. For example, MIPS architecture has a syscall array with 1528 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1529 related optimizations for a given architecture. 1530 1531 config ARCH_HAS_VDSO_DATA 1532 bool 1533 1534 config HAVE_STATIC_CALL 1535 bool 1536 1537 config HAVE_STATIC_CALL_INLINE 1538 bool 1539 depends on HAVE_STATIC_CALL 1540 select OBJTOOL 1541 1542 config HAVE_PREEMPT_DYNAMIC 1543 bool 1544 1545 config HAVE_PREEMPT_DYNAMIC_CALL 1546 bool 1547 depends on HAVE_STATIC_CALL 1548 select HAVE_PREEMPT_DYNAMIC 1549 help 1550 An architecture should select this if it can handle the preemption 1551 model being selected at boot time using static calls. 1552 1553 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1554 preemption function will be patched directly. 1555 1556 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1557 call to a preemption function will go through a trampoline, and the 1558 trampoline will be patched. 1559 1560 It is strongly advised to support inline static call to avoid any 1561 overhead. 1562 1563 config HAVE_PREEMPT_DYNAMIC_KEY 1564 bool 1565 depends on HAVE_ARCH_JUMP_LABEL 1566 select HAVE_PREEMPT_DYNAMIC 1567 help 1568 An architecture should select this if it can handle the preemption 1569 model being selected at boot time using static keys. 1570 1571 Each preemption function will be given an early return based on a 1572 static key. This should have slightly lower overhead than non-inline 1573 static calls, as this effectively inlines each trampoline into the 1574 start of its callee. This may avoid redundant work, and may 1575 integrate better with CFI schemes. 1576 1577 This will have greater overhead than using inline static calls as 1578 the call to the preemption function cannot be entirely elided. 1579 1580 config ARCH_WANT_LD_ORPHAN_WARN 1581 bool 1582 help 1583 An arch should select this symbol once all linker sections are explicitly 1584 included, size-asserted, or discarded in the linker scripts. This is 1585 important because we never want expected sections to be placed heuristically 1586 by the linker, since the locations of such sections can change between linker 1587 versions. 1588 1589 config HAVE_ARCH_PFN_VALID 1590 bool 1591 1592 config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1593 bool 1594 1595 config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1596 bool 1597 1598 config ARCH_SPLIT_ARG64 1599 bool 1600 help 1601 If a 32-bit architecture requires 64-bit arguments to be split into 1602 pairs of 32-bit arguments, select this option. 1603 1604 config ARCH_HAS_ELFCORE_COMPAT 1605 bool 1606 1607 config ARCH_HAS_PARANOID_L1D_FLUSH 1608 bool 1609 1610 config ARCH_HAVE_TRACE_MMIO_ACCESS 1611 bool 1612 1613 config DYNAMIC_SIGFRAME 1614 bool 1615 1616 # Select, if arch has a named attribute group bound to NUMA device nodes. 1617 config HAVE_ARCH_NODE_DEV_GROUP 1618 bool 1619 1620 config ARCH_HAS_HW_PTE_YOUNG 1621 bool 1622 help 1623 Architectures that select this option are capable of setting the 1624 accessed bit in PTE entries when using them as part of linear address 1625 translations. Architectures that require runtime check should select 1626 this option and override arch_has_hw_pte_young(). 1627 1628 config ARCH_HAS_NONLEAF_PMD_YOUNG 1629 bool 1630 help 1631 Architectures that select this option are capable of setting the 1632 accessed bit in non-leaf PMD entries when using them as part of linear 1633 address translations. Page table walkers that clear the accessed bit 1634 may use this capability to reduce their search space. 1635 1636 config ARCH_HAS_KERNEL_FPU_SUPPORT 1637 bool 1638 help 1639 Architectures that select this option can run floating-point code in 1640 the kernel, as described in Documentation/core-api/floating-point.rst. 1641 1642 source "kernel/gcov/Kconfig" 1643 1644 source "scripts/gcc-plugins/Kconfig" 1645 1646 config FUNCTION_ALIGNMENT_4B 1647 bool 1648 1649 config FUNCTION_ALIGNMENT_8B 1650 bool 1651 1652 config FUNCTION_ALIGNMENT_16B 1653 bool 1654 1655 config FUNCTION_ALIGNMENT_32B 1656 bool 1657 1658 config FUNCTION_ALIGNMENT_64B 1659 bool 1660 1661 config FUNCTION_ALIGNMENT 1662 int 1663 default 64 if FUNCTION_ALIGNMENT_64B 1664 default 32 if FUNCTION_ALIGNMENT_32B 1665 default 16 if FUNCTION_ALIGNMENT_16B 1666 default 8 if FUNCTION_ALIGNMENT_8B 1667 default 4 if FUNCTION_ALIGNMENT_4B 1668 default 0 1669 1670 config CC_HAS_MIN_FUNCTION_ALIGNMENT 1671 # Detect availability of the GCC option -fmin-function-alignment which 1672 # guarantees minimal alignment for all functions, unlike 1673 # -falign-functions which the compiler ignores for cold functions. 1674 def_bool $(cc-option, -fmin-function-alignment=8) 1675 1676 config CC_HAS_SANE_FUNCTION_ALIGNMENT 1677 # Set if the guaranteed alignment with -fmin-function-alignment is 1678 # available or extra care is required in the kernel. Clang provides 1679 # strict alignment always, even with -falign-functions. 1680 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG 1681 1682 config ARCH_NEED_CMPXCHG_1_EMU 1683 bool 1684 1685 endmenu 1686