1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6# 7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8# override the default values in this file. 9# 10source "arch/$(SRCARCH)/Kconfig" 11 12menu "General architecture-dependent options" 13 14config CRASH_CORE 15 bool 16 17config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21config KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config HOTPLUG_SMT 28 bool 29 30config GENERIC_ENTRY 31 bool 32 33config KPROBES 34 bool "Kprobes" 35 depends on MODULES 36 depends on HAVE_KPROBES 37 select KALLSYMS 38 help 39 Kprobes allows you to trap at almost any kernel address and 40 execute a callback function. register_kprobe() establishes 41 a probepoint and specifies the callback. Kprobes is useful 42 for kernel debugging, non-intrusive instrumentation and testing. 43 If in doubt, say "N". 44 45config JUMP_LABEL 46 bool "Optimize very unlikely/likely branches" 47 depends on HAVE_ARCH_JUMP_LABEL 48 depends on CC_HAS_ASM_GOTO 49 help 50 This option enables a transparent branch optimization that 51 makes certain almost-always-true or almost-always-false branch 52 conditions even cheaper to execute within the kernel. 53 54 Certain performance-sensitive kernel code, such as trace points, 55 scheduler functionality, networking code and KVM have such 56 branches and include support for this optimization technique. 57 58 If it is detected that the compiler has support for "asm goto", 59 the kernel will compile such branches with just a nop 60 instruction. When the condition flag is toggled to true, the 61 nop will be converted to a jump instruction to execute the 62 conditional block of instructions. 63 64 This technique lowers overhead and stress on the branch prediction 65 of the processor and generally makes the kernel faster. The update 66 of the condition is slower, but those are always very rare. 67 68 ( On 32-bit x86, the necessary options added to the compiler 69 flags may increase the size of the kernel slightly. ) 70 71config STATIC_KEYS_SELFTEST 72 bool "Static key selftest" 73 depends on JUMP_LABEL 74 help 75 Boot time self-test of the branch patching code. 76 77config STATIC_CALL_SELFTEST 78 bool "Static call selftest" 79 depends on HAVE_STATIC_CALL 80 help 81 Boot time self-test of the call patching code. 82 83config OPTPROBES 84 def_bool y 85 depends on KPROBES && HAVE_OPTPROBES 86 select TASKS_RCU if PREEMPTION 87 88config KPROBES_ON_FTRACE 89 def_bool y 90 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 91 depends on DYNAMIC_FTRACE_WITH_REGS 92 help 93 If function tracer is enabled and the arch supports full 94 passing of pt_regs to function tracing, then kprobes can 95 optimize on top of function tracing. 96 97config UPROBES 98 def_bool n 99 depends on ARCH_SUPPORTS_UPROBES 100 help 101 Uprobes is the user-space counterpart to kprobes: they 102 enable instrumentation applications (such as 'perf probe') 103 to establish unintrusive probes in user-space binaries and 104 libraries, by executing handler functions when the probes 105 are hit by user-space applications. 106 107 ( These probes come in the form of single-byte breakpoints, 108 managed by the kernel and kept transparent to the probed 109 application. ) 110 111config HAVE_64BIT_ALIGNED_ACCESS 112 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 113 help 114 Some architectures require 64 bit accesses to be 64 bit 115 aligned, which also requires structs containing 64 bit values 116 to be 64 bit aligned too. This includes some 32 bit 117 architectures which can do 64 bit accesses, as well as 64 bit 118 architectures without unaligned access. 119 120 This symbol should be selected by an architecture if 64 bit 121 accesses are required to be 64 bit aligned in this way even 122 though it is not a 64 bit architecture. 123 124 See Documentation/core-api/unaligned-memory-access.rst for 125 more information on the topic of unaligned memory accesses. 126 127config HAVE_EFFICIENT_UNALIGNED_ACCESS 128 bool 129 help 130 Some architectures are unable to perform unaligned accesses 131 without the use of get_unaligned/put_unaligned. Others are 132 unable to perform such accesses efficiently (e.g. trap on 133 unaligned access and require fixing it up in the exception 134 handler.) 135 136 This symbol should be selected by an architecture if it can 137 perform unaligned accesses efficiently to allow different 138 code paths to be selected for these cases. Some network 139 drivers, for example, could opt to not fix up alignment 140 problems with received packets if doing so would not help 141 much. 142 143 See Documentation/core-api/unaligned-memory-access.rst for more 144 information on the topic of unaligned memory accesses. 145 146config ARCH_USE_BUILTIN_BSWAP 147 bool 148 help 149 Modern versions of GCC (since 4.4) have builtin functions 150 for handling byte-swapping. Using these, instead of the old 151 inline assembler that the architecture code provides in the 152 __arch_bswapXX() macros, allows the compiler to see what's 153 happening and offers more opportunity for optimisation. In 154 particular, the compiler will be able to combine the byteswap 155 with a nearby load or store and use load-and-swap or 156 store-and-swap instructions if the architecture has them. It 157 should almost *never* result in code which is worse than the 158 hand-coded assembler in <asm/swab.h>. But just in case it 159 does, the use of the builtins is optional. 160 161 Any architecture with load-and-swap or store-and-swap 162 instructions should set this. And it shouldn't hurt to set it 163 on architectures that don't have such instructions. 164 165config KRETPROBES 166 def_bool y 167 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK) 168 169config KRETPROBE_ON_RETHOOK 170 def_bool y 171 depends on HAVE_RETHOOK 172 depends on KRETPROBES 173 select RETHOOK 174 175config USER_RETURN_NOTIFIER 176 bool 177 depends on HAVE_USER_RETURN_NOTIFIER 178 help 179 Provide a kernel-internal notification when a cpu is about to 180 switch to user mode. 181 182config HAVE_IOREMAP_PROT 183 bool 184 185config HAVE_KPROBES 186 bool 187 188config HAVE_KRETPROBES 189 bool 190 191config HAVE_OPTPROBES 192 bool 193 194config HAVE_KPROBES_ON_FTRACE 195 bool 196 197config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 198 bool 199 help 200 Since kretprobes modifies return address on the stack, the 201 stacktrace may see the kretprobe trampoline address instead 202 of correct one. If the architecture stacktrace code and 203 unwinder can adjust such entries, select this configuration. 204 205config HAVE_FUNCTION_ERROR_INJECTION 206 bool 207 208config HAVE_NMI 209 bool 210 211config HAVE_FUNCTION_DESCRIPTORS 212 bool 213 214config TRACE_IRQFLAGS_SUPPORT 215 bool 216 217# 218# An arch should select this if it provides all these things: 219# 220# task_pt_regs() in asm/processor.h or asm/ptrace.h 221# arch_has_single_step() if there is hardware single-step support 222# arch_has_block_step() if there is hardware block-step support 223# asm/syscall.h supplying asm-generic/syscall.h interface 224# linux/regset.h user_regset interfaces 225# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 226# TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit} 227# TIF_NOTIFY_RESUME calls resume_user_mode_work() 228# 229config HAVE_ARCH_TRACEHOOK 230 bool 231 232config HAVE_DMA_CONTIGUOUS 233 bool 234 235config GENERIC_SMP_IDLE_THREAD 236 bool 237 238config GENERIC_IDLE_POLL_SETUP 239 bool 240 241config ARCH_HAS_FORTIFY_SOURCE 242 bool 243 help 244 An architecture should select this when it can successfully 245 build and run with CONFIG_FORTIFY_SOURCE. 246 247# 248# Select if the arch provides a historic keepinit alias for the retain_initrd 249# command line option 250# 251config ARCH_HAS_KEEPINITRD 252 bool 253 254# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 255config ARCH_HAS_SET_MEMORY 256 bool 257 258# Select if arch has all set_direct_map_invalid/default() functions 259config ARCH_HAS_SET_DIRECT_MAP 260 bool 261 262# 263# Select if the architecture provides the arch_dma_set_uncached symbol to 264# either provide an uncached segment alias for a DMA allocation, or 265# to remap the page tables in place. 266# 267config ARCH_HAS_DMA_SET_UNCACHED 268 bool 269 270# 271# Select if the architectures provides the arch_dma_clear_uncached symbol 272# to undo an in-place page table remap for uncached access. 273# 274config ARCH_HAS_DMA_CLEAR_UNCACHED 275 bool 276 277# Select if arch init_task must go in the __init_task_data section 278config ARCH_TASK_STRUCT_ON_STACK 279 bool 280 281# Select if arch has its private alloc_task_struct() function 282config ARCH_TASK_STRUCT_ALLOCATOR 283 bool 284 285config HAVE_ARCH_THREAD_STRUCT_WHITELIST 286 bool 287 depends on !ARCH_TASK_STRUCT_ALLOCATOR 288 help 289 An architecture should select this to provide hardened usercopy 290 knowledge about what region of the thread_struct should be 291 whitelisted for copying to userspace. Normally this is only the 292 FPU registers. Specifically, arch_thread_struct_whitelist() 293 should be implemented. Without this, the entire thread_struct 294 field in task_struct will be left whitelisted. 295 296# Select if arch has its private alloc_thread_stack() function 297config ARCH_THREAD_STACK_ALLOCATOR 298 bool 299 300# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 301config ARCH_WANTS_DYNAMIC_TASK_STRUCT 302 bool 303 304config ARCH_WANTS_NO_INSTR 305 bool 306 help 307 An architecture should select this if the noinstr macro is being used on 308 functions to denote that the toolchain should avoid instrumenting such 309 functions and is required for correctness. 310 311config ARCH_32BIT_OFF_T 312 bool 313 depends on !64BIT 314 help 315 All new 32-bit architectures should have 64-bit off_t type on 316 userspace side which corresponds to the loff_t kernel type. This 317 is the requirement for modern ABIs. Some existing architectures 318 still support 32-bit off_t. This option is enabled for all such 319 architectures explicitly. 320 321# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 322config ARCH_32BIT_USTAT_F_TINODE 323 bool 324 325config HAVE_ASM_MODVERSIONS 326 bool 327 help 328 This symbol should be selected by an architecture if it provides 329 <asm/asm-prototypes.h> to support the module versioning for symbols 330 exported from assembly code. 331 332config HAVE_REGS_AND_STACK_ACCESS_API 333 bool 334 help 335 This symbol should be selected by an architecture if it supports 336 the API needed to access registers and stack entries from pt_regs, 337 declared in asm/ptrace.h 338 For example the kprobes-based event tracer needs this API. 339 340config HAVE_RSEQ 341 bool 342 depends on HAVE_REGS_AND_STACK_ACCESS_API 343 help 344 This symbol should be selected by an architecture if it 345 supports an implementation of restartable sequences. 346 347config HAVE_FUNCTION_ARG_ACCESS_API 348 bool 349 help 350 This symbol should be selected by an architecture if it supports 351 the API needed to access function arguments from pt_regs, 352 declared in asm/ptrace.h 353 354config HAVE_HW_BREAKPOINT 355 bool 356 depends on PERF_EVENTS 357 358config HAVE_MIXED_BREAKPOINTS_REGS 359 bool 360 depends on HAVE_HW_BREAKPOINT 361 help 362 Depending on the arch implementation of hardware breakpoints, 363 some of them have separate registers for data and instruction 364 breakpoints addresses, others have mixed registers to store 365 them but define the access type in a control register. 366 Select this option if your arch implements breakpoints under the 367 latter fashion. 368 369config HAVE_USER_RETURN_NOTIFIER 370 bool 371 372config HAVE_PERF_EVENTS_NMI 373 bool 374 help 375 System hardware can generate an NMI using the perf event 376 subsystem. Also has support for calculating CPU cycle events 377 to determine how many clock cycles in a given period. 378 379config HAVE_HARDLOCKUP_DETECTOR_PERF 380 bool 381 depends on HAVE_PERF_EVENTS_NMI 382 help 383 The arch chooses to use the generic perf-NMI-based hardlockup 384 detector. Must define HAVE_PERF_EVENTS_NMI. 385 386config HAVE_NMI_WATCHDOG 387 depends on HAVE_NMI 388 bool 389 help 390 The arch provides a low level NMI watchdog. It provides 391 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 392 393config HAVE_HARDLOCKUP_DETECTOR_ARCH 394 bool 395 select HAVE_NMI_WATCHDOG 396 help 397 The arch chooses to provide its own hardlockup detector, which is 398 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 399 interfaces and parameters provided by hardlockup detector subsystem. 400 401config HAVE_PERF_REGS 402 bool 403 help 404 Support selective register dumps for perf events. This includes 405 bit-mapping of each registers and a unique architecture id. 406 407config HAVE_PERF_USER_STACK_DUMP 408 bool 409 help 410 Support user stack dumps for perf event samples. This needs 411 access to the user stack pointer which is not unified across 412 architectures. 413 414config HAVE_ARCH_JUMP_LABEL 415 bool 416 417config HAVE_ARCH_JUMP_LABEL_RELATIVE 418 bool 419 420config MMU_GATHER_TABLE_FREE 421 bool 422 423config MMU_GATHER_RCU_TABLE_FREE 424 bool 425 select MMU_GATHER_TABLE_FREE 426 427config MMU_GATHER_PAGE_SIZE 428 bool 429 430config MMU_GATHER_NO_RANGE 431 bool 432 433config MMU_GATHER_NO_GATHER 434 bool 435 depends on MMU_GATHER_TABLE_FREE 436 437config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 438 bool 439 help 440 Temporary select until all architectures can be converted to have 441 irqs disabled over activate_mm. Architectures that do IPI based TLB 442 shootdowns should enable this. 443 444config ARCH_HAVE_NMI_SAFE_CMPXCHG 445 bool 446 447config HAVE_ALIGNED_STRUCT_PAGE 448 bool 449 help 450 This makes sure that struct pages are double word aligned and that 451 e.g. the SLUB allocator can perform double word atomic operations 452 on a struct page for better performance. However selecting this 453 might increase the size of a struct page by a word. 454 455config HAVE_CMPXCHG_LOCAL 456 bool 457 458config HAVE_CMPXCHG_DOUBLE 459 bool 460 461config ARCH_WEAK_RELEASE_ACQUIRE 462 bool 463 464config ARCH_WANT_IPC_PARSE_VERSION 465 bool 466 467config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 468 bool 469 470config ARCH_WANT_OLD_COMPAT_IPC 471 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 472 bool 473 474config HAVE_ARCH_SECCOMP 475 bool 476 help 477 An arch should select this symbol to support seccomp mode 1 (the fixed 478 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 479 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 480 - __NR_seccomp_read_32 481 - __NR_seccomp_write_32 482 - __NR_seccomp_exit_32 483 - __NR_seccomp_sigreturn_32 484 485config HAVE_ARCH_SECCOMP_FILTER 486 bool 487 select HAVE_ARCH_SECCOMP 488 help 489 An arch should select this symbol if it provides all of these things: 490 - all the requirements for HAVE_ARCH_SECCOMP 491 - syscall_get_arch() 492 - syscall_get_arguments() 493 - syscall_rollback() 494 - syscall_set_return_value() 495 - SIGSYS siginfo_t support 496 - secure_computing is called from a ptrace_event()-safe context 497 - secure_computing return value is checked and a return value of -1 498 results in the system call being skipped immediately. 499 - seccomp syscall wired up 500 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 501 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 502 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 503 504config SECCOMP 505 prompt "Enable seccomp to safely execute untrusted bytecode" 506 def_bool y 507 depends on HAVE_ARCH_SECCOMP 508 help 509 This kernel feature is useful for number crunching applications 510 that may need to handle untrusted bytecode during their 511 execution. By using pipes or other transports made available 512 to the process as file descriptors supporting the read/write 513 syscalls, it's possible to isolate those applications in their 514 own address space using seccomp. Once seccomp is enabled via 515 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 516 disabled and the task is only allowed to execute a few safe 517 syscalls defined by each seccomp mode. 518 519 If unsure, say Y. 520 521config SECCOMP_FILTER 522 def_bool y 523 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 524 help 525 Enable tasks to build secure computing environments defined 526 in terms of Berkeley Packet Filter programs which implement 527 task-defined system call filtering polices. 528 529 See Documentation/userspace-api/seccomp_filter.rst for details. 530 531config SECCOMP_CACHE_DEBUG 532 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 533 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 534 depends on PROC_FS 535 help 536 This enables the /proc/pid/seccomp_cache interface to monitor 537 seccomp cache data. The file format is subject to change. Reading 538 the file requires CAP_SYS_ADMIN. 539 540 This option is for debugging only. Enabling presents the risk that 541 an adversary may be able to infer the seccomp filter logic. 542 543 If unsure, say N. 544 545config HAVE_ARCH_STACKLEAK 546 bool 547 help 548 An architecture should select this if it has the code which 549 fills the used part of the kernel stack with the STACKLEAK_POISON 550 value before returning from system calls. 551 552config HAVE_STACKPROTECTOR 553 bool 554 help 555 An arch should select this symbol if: 556 - it has implemented a stack canary (e.g. __stack_chk_guard) 557 558config STACKPROTECTOR 559 bool "Stack Protector buffer overflow detection" 560 depends on HAVE_STACKPROTECTOR 561 depends on $(cc-option,-fstack-protector) 562 default y 563 help 564 This option turns on the "stack-protector" GCC feature. This 565 feature puts, at the beginning of functions, a canary value on 566 the stack just before the return address, and validates 567 the value just before actually returning. Stack based buffer 568 overflows (that need to overwrite this return address) now also 569 overwrite the canary, which gets detected and the attack is then 570 neutralized via a kernel panic. 571 572 Functions will have the stack-protector canary logic added if they 573 have an 8-byte or larger character array on the stack. 574 575 This feature requires gcc version 4.2 or above, or a distribution 576 gcc with the feature backported ("-fstack-protector"). 577 578 On an x86 "defconfig" build, this feature adds canary checks to 579 about 3% of all kernel functions, which increases kernel code size 580 by about 0.3%. 581 582config STACKPROTECTOR_STRONG 583 bool "Strong Stack Protector" 584 depends on STACKPROTECTOR 585 depends on $(cc-option,-fstack-protector-strong) 586 default y 587 help 588 Functions will have the stack-protector canary logic added in any 589 of the following conditions: 590 591 - local variable's address used as part of the right hand side of an 592 assignment or function argument 593 - local variable is an array (or union containing an array), 594 regardless of array type or length 595 - uses register local variables 596 597 This feature requires gcc version 4.9 or above, or a distribution 598 gcc with the feature backported ("-fstack-protector-strong"). 599 600 On an x86 "defconfig" build, this feature adds canary checks to 601 about 20% of all kernel functions, which increases the kernel code 602 size by about 2%. 603 604config ARCH_SUPPORTS_SHADOW_CALL_STACK 605 bool 606 help 607 An architecture should select this if it supports the compiler's 608 Shadow Call Stack and implements runtime support for shadow stack 609 switching. 610 611config SHADOW_CALL_STACK 612 bool "Shadow Call Stack" 613 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK 614 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 615 help 616 This option enables the compiler's Shadow Call Stack, which 617 uses a shadow stack to protect function return addresses from 618 being overwritten by an attacker. More information can be found 619 in the compiler's documentation: 620 621 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html 622 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options 623 624 Note that security guarantees in the kernel differ from the 625 ones documented for user space. The kernel must store addresses 626 of shadow stacks in memory, which means an attacker capable of 627 reading and writing arbitrary memory may be able to locate them 628 and hijack control flow by modifying the stacks. 629 630config LTO 631 bool 632 help 633 Selected if the kernel will be built using the compiler's LTO feature. 634 635config LTO_CLANG 636 bool 637 select LTO 638 help 639 Selected if the kernel will be built using Clang's LTO feature. 640 641config ARCH_SUPPORTS_LTO_CLANG 642 bool 643 help 644 An architecture should select this option if it supports: 645 - compiling with Clang, 646 - compiling inline assembly with Clang's integrated assembler, 647 - and linking with LLD. 648 649config ARCH_SUPPORTS_LTO_CLANG_THIN 650 bool 651 help 652 An architecture should select this option if it can support Clang's 653 ThinLTO mode. 654 655config HAS_LTO_CLANG 656 def_bool y 657 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM 658 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 659 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 660 depends on ARCH_SUPPORTS_LTO_CLANG 661 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 662 depends on !KASAN || KASAN_HW_TAGS 663 depends on !GCOV_KERNEL 664 help 665 The compiler and Kconfig options support building with Clang's 666 LTO. 667 668choice 669 prompt "Link Time Optimization (LTO)" 670 default LTO_NONE 671 help 672 This option enables Link Time Optimization (LTO), which allows the 673 compiler to optimize binaries globally. 674 675 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 676 so it's disabled by default. 677 678config LTO_NONE 679 bool "None" 680 help 681 Build the kernel normally, without Link Time Optimization (LTO). 682 683config LTO_CLANG_FULL 684 bool "Clang Full LTO (EXPERIMENTAL)" 685 depends on HAS_LTO_CLANG 686 depends on !COMPILE_TEST 687 select LTO_CLANG 688 help 689 This option enables Clang's full Link Time Optimization (LTO), which 690 allows the compiler to optimize the kernel globally. If you enable 691 this option, the compiler generates LLVM bitcode instead of ELF 692 object files, and the actual compilation from bitcode happens at 693 the LTO link step, which may take several minutes depending on the 694 kernel configuration. More information can be found from LLVM's 695 documentation: 696 697 https://llvm.org/docs/LinkTimeOptimization.html 698 699 During link time, this option can use a large amount of RAM, and 700 may take much longer than the ThinLTO option. 701 702config LTO_CLANG_THIN 703 bool "Clang ThinLTO (EXPERIMENTAL)" 704 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 705 select LTO_CLANG 706 help 707 This option enables Clang's ThinLTO, which allows for parallel 708 optimization and faster incremental compiles compared to the 709 CONFIG_LTO_CLANG_FULL option. More information can be found 710 from Clang's documentation: 711 712 https://clang.llvm.org/docs/ThinLTO.html 713 714 If unsure, say Y. 715endchoice 716 717config ARCH_SUPPORTS_CFI_CLANG 718 bool 719 help 720 An architecture should select this option if it can support Clang's 721 Control-Flow Integrity (CFI) checking. 722 723config CFI_CLANG 724 bool "Use Clang's Control Flow Integrity (CFI)" 725 depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG 726 # Clang >= 12: 727 # - https://bugs.llvm.org/show_bug.cgi?id=46258 728 # - https://bugs.llvm.org/show_bug.cgi?id=47479 729 depends on CLANG_VERSION >= 120000 730 select KALLSYMS 731 help 732 This option enables Clang’s forward-edge Control Flow Integrity 733 (CFI) checking, where the compiler injects a runtime check to each 734 indirect function call to ensure the target is a valid function with 735 the correct static type. This restricts possible call targets and 736 makes it more difficult for an attacker to exploit bugs that allow 737 the modification of stored function pointers. More information can be 738 found from Clang's documentation: 739 740 https://clang.llvm.org/docs/ControlFlowIntegrity.html 741 742config CFI_CLANG_SHADOW 743 bool "Use CFI shadow to speed up cross-module checks" 744 default y 745 depends on CFI_CLANG && MODULES 746 help 747 If you select this option, the kernel builds a fast look-up table of 748 CFI check functions in loaded modules to reduce performance overhead. 749 750 If unsure, say Y. 751 752config CFI_PERMISSIVE 753 bool "Use CFI in permissive mode" 754 depends on CFI_CLANG 755 help 756 When selected, Control Flow Integrity (CFI) violations result in a 757 warning instead of a kernel panic. This option should only be used 758 for finding indirect call type mismatches during development. 759 760 If unsure, say N. 761 762config HAVE_ARCH_WITHIN_STACK_FRAMES 763 bool 764 help 765 An architecture should select this if it can walk the kernel stack 766 frames to determine if an object is part of either the arguments 767 or local variables (i.e. that it excludes saved return addresses, 768 and similar) by implementing an inline arch_within_stack_frames(), 769 which is used by CONFIG_HARDENED_USERCOPY. 770 771config HAVE_CONTEXT_TRACKING 772 bool 773 help 774 Provide kernel/user boundaries probes necessary for subsystems 775 that need it, such as userspace RCU extended quiescent state. 776 Syscalls need to be wrapped inside user_exit()-user_enter(), either 777 optimized behind static key or through the slow path using TIF_NOHZ 778 flag. Exceptions handlers must be wrapped as well. Irqs are already 779 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 780 handling on irq exit still need to be protected. 781 782config HAVE_CONTEXT_TRACKING_OFFSTACK 783 bool 784 help 785 Architecture neither relies on exception_enter()/exception_exit() 786 nor on schedule_user(). Also preempt_schedule_notrace() and 787 preempt_schedule_irq() can't be called in a preemptible section 788 while context tracking is CONTEXT_USER. This feature reflects a sane 789 entry implementation where the following requirements are met on 790 critical entry code, ie: before user_exit() or after user_enter(): 791 792 - Critical entry code isn't preemptible (or better yet: 793 not interruptible). 794 - No use of RCU read side critical sections, unless rcu_nmi_enter() 795 got called. 796 - No use of instrumentation, unless instrumentation_begin() got 797 called. 798 799config HAVE_TIF_NOHZ 800 bool 801 help 802 Arch relies on TIF_NOHZ and syscall slow path to implement context 803 tracking calls to user_enter()/user_exit(). 804 805config HAVE_VIRT_CPU_ACCOUNTING 806 bool 807 808config HAVE_VIRT_CPU_ACCOUNTING_IDLE 809 bool 810 help 811 Architecture has its own way to account idle CPU time and therefore 812 doesn't implement vtime_account_idle(). 813 814config ARCH_HAS_SCALED_CPUTIME 815 bool 816 817config HAVE_VIRT_CPU_ACCOUNTING_GEN 818 bool 819 default y if 64BIT 820 help 821 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 822 Before enabling this option, arch code must be audited 823 to ensure there are no races in concurrent read/write of 824 cputime_t. For example, reading/writing 64-bit cputime_t on 825 some 32-bit arches may require multiple accesses, so proper 826 locking is needed to protect against concurrent accesses. 827 828config HAVE_IRQ_TIME_ACCOUNTING 829 bool 830 help 831 Archs need to ensure they use a high enough resolution clock to 832 support irq time accounting and then call enable_sched_clock_irqtime(). 833 834config HAVE_MOVE_PUD 835 bool 836 help 837 Architectures that select this are able to move page tables at the 838 PUD level. If there are only 3 page table levels, the move effectively 839 happens at the PGD level. 840 841config HAVE_MOVE_PMD 842 bool 843 help 844 Archs that select this are able to move page tables at the PMD level. 845 846config HAVE_ARCH_TRANSPARENT_HUGEPAGE 847 bool 848 849config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 850 bool 851 852config HAVE_ARCH_HUGE_VMAP 853 bool 854 855# 856# Archs that select this would be capable of PMD-sized vmaps (i.e., 857# arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag 858# must be used to enable allocations to use hugepages. 859# 860config HAVE_ARCH_HUGE_VMALLOC 861 depends on HAVE_ARCH_HUGE_VMAP 862 bool 863 864config ARCH_WANT_HUGE_PMD_SHARE 865 bool 866 867config HAVE_ARCH_SOFT_DIRTY 868 bool 869 870config HAVE_MOD_ARCH_SPECIFIC 871 bool 872 help 873 The arch uses struct mod_arch_specific to store data. Many arches 874 just need a simple module loader without arch specific data - those 875 should not enable this. 876 877config MODULES_USE_ELF_RELA 878 bool 879 help 880 Modules only use ELF RELA relocations. Modules with ELF REL 881 relocations will give an error. 882 883config MODULES_USE_ELF_REL 884 bool 885 help 886 Modules only use ELF REL relocations. Modules with ELF RELA 887 relocations will give an error. 888 889config HAVE_IRQ_EXIT_ON_IRQ_STACK 890 bool 891 help 892 Architecture doesn't only execute the irq handler on the irq stack 893 but also irq_exit(). This way we can process softirqs on this irq 894 stack instead of switching to a new one when we call __do_softirq() 895 in the end of an hardirq. 896 This spares a stack switch and improves cache usage on softirq 897 processing. 898 899config HAVE_SOFTIRQ_ON_OWN_STACK 900 bool 901 help 902 Architecture provides a function to run __do_softirq() on a 903 separate stack. 904 905config ALTERNATE_USER_ADDRESS_SPACE 906 bool 907 help 908 Architectures set this when the CPU uses separate address 909 spaces for kernel and user space pointers. In this case, the 910 access_ok() check on a __user pointer is skipped. 911 912config PGTABLE_LEVELS 913 int 914 default 2 915 916config ARCH_HAS_ELF_RANDOMIZE 917 bool 918 help 919 An architecture supports choosing randomized locations for 920 stack, mmap, brk, and ET_DYN. Defined functions: 921 - arch_mmap_rnd() 922 - arch_randomize_brk() 923 924config HAVE_ARCH_MMAP_RND_BITS 925 bool 926 help 927 An arch should select this symbol if it supports setting a variable 928 number of bits for use in establishing the base address for mmap 929 allocations, has MMU enabled and provides values for both: 930 - ARCH_MMAP_RND_BITS_MIN 931 - ARCH_MMAP_RND_BITS_MAX 932 933config HAVE_EXIT_THREAD 934 bool 935 help 936 An architecture implements exit_thread. 937 938config ARCH_MMAP_RND_BITS_MIN 939 int 940 941config ARCH_MMAP_RND_BITS_MAX 942 int 943 944config ARCH_MMAP_RND_BITS_DEFAULT 945 int 946 947config ARCH_MMAP_RND_BITS 948 int "Number of bits to use for ASLR of mmap base address" if EXPERT 949 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 950 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 951 default ARCH_MMAP_RND_BITS_MIN 952 depends on HAVE_ARCH_MMAP_RND_BITS 953 help 954 This value can be used to select the number of bits to use to 955 determine the random offset to the base address of vma regions 956 resulting from mmap allocations. This value will be bounded 957 by the architecture's minimum and maximum supported values. 958 959 This value can be changed after boot using the 960 /proc/sys/vm/mmap_rnd_bits tunable 961 962config HAVE_ARCH_MMAP_RND_COMPAT_BITS 963 bool 964 help 965 An arch should select this symbol if it supports running applications 966 in compatibility mode, supports setting a variable number of bits for 967 use in establishing the base address for mmap allocations, has MMU 968 enabled and provides values for both: 969 - ARCH_MMAP_RND_COMPAT_BITS_MIN 970 - ARCH_MMAP_RND_COMPAT_BITS_MAX 971 972config ARCH_MMAP_RND_COMPAT_BITS_MIN 973 int 974 975config ARCH_MMAP_RND_COMPAT_BITS_MAX 976 int 977 978config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 979 int 980 981config ARCH_MMAP_RND_COMPAT_BITS 982 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 983 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 984 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 985 default ARCH_MMAP_RND_COMPAT_BITS_MIN 986 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 987 help 988 This value can be used to select the number of bits to use to 989 determine the random offset to the base address of vma regions 990 resulting from mmap allocations for compatible applications This 991 value will be bounded by the architecture's minimum and maximum 992 supported values. 993 994 This value can be changed after boot using the 995 /proc/sys/vm/mmap_rnd_compat_bits tunable 996 997config HAVE_ARCH_COMPAT_MMAP_BASES 998 bool 999 help 1000 This allows 64bit applications to invoke 32-bit mmap() syscall 1001 and vice-versa 32-bit applications to call 64-bit mmap(). 1002 Required for applications doing different bitness syscalls. 1003 1004config PAGE_SIZE_LESS_THAN_64KB 1005 def_bool y 1006 depends on !ARM64_64K_PAGES 1007 depends on !IA64_PAGE_SIZE_64KB 1008 depends on !PAGE_SIZE_64KB 1009 depends on !PARISC_PAGE_SIZE_64KB 1010 depends on !PPC_64K_PAGES 1011 depends on PAGE_SIZE_LESS_THAN_256KB 1012 1013config PAGE_SIZE_LESS_THAN_256KB 1014 def_bool y 1015 depends on !PPC_256K_PAGES 1016 depends on !PAGE_SIZE_256KB 1017 1018# This allows to use a set of generic functions to determine mmap base 1019# address by giving priority to top-down scheme only if the process 1020# is not in legacy mode (compat task, unlimited stack size or 1021# sysctl_legacy_va_layout). 1022# Architecture that selects this option can provide its own version of: 1023# - STACK_RND_MASK 1024config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1025 bool 1026 depends on MMU 1027 select ARCH_HAS_ELF_RANDOMIZE 1028 1029config HAVE_STACK_VALIDATION 1030 bool 1031 help 1032 Architecture supports the 'objtool check' host tool command, which 1033 performs compile-time stack metadata validation. 1034 1035config HAVE_RELIABLE_STACKTRACE 1036 bool 1037 help 1038 Architecture has either save_stack_trace_tsk_reliable() or 1039 arch_stack_walk_reliable() function which only returns a stack trace 1040 if it can guarantee the trace is reliable. 1041 1042config HAVE_ARCH_HASH 1043 bool 1044 default n 1045 help 1046 If this is set, the architecture provides an <asm/hash.h> 1047 file which provides platform-specific implementations of some 1048 functions in <linux/hash.h> or fs/namei.c. 1049 1050config HAVE_ARCH_NVRAM_OPS 1051 bool 1052 1053config ISA_BUS_API 1054 def_bool ISA 1055 1056# 1057# ABI hall of shame 1058# 1059config CLONE_BACKWARDS 1060 bool 1061 help 1062 Architecture has tls passed as the 4th argument of clone(2), 1063 not the 5th one. 1064 1065config CLONE_BACKWARDS2 1066 bool 1067 help 1068 Architecture has the first two arguments of clone(2) swapped. 1069 1070config CLONE_BACKWARDS3 1071 bool 1072 help 1073 Architecture has tls passed as the 3rd argument of clone(2), 1074 not the 5th one. 1075 1076config ODD_RT_SIGACTION 1077 bool 1078 help 1079 Architecture has unusual rt_sigaction(2) arguments 1080 1081config OLD_SIGSUSPEND 1082 bool 1083 help 1084 Architecture has old sigsuspend(2) syscall, of one-argument variety 1085 1086config OLD_SIGSUSPEND3 1087 bool 1088 help 1089 Even weirder antique ABI - three-argument sigsuspend(2) 1090 1091config OLD_SIGACTION 1092 bool 1093 help 1094 Architecture has old sigaction(2) syscall. Nope, not the same 1095 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1096 but fairly different variant of sigaction(2), thanks to OSF/1 1097 compatibility... 1098 1099config COMPAT_OLD_SIGACTION 1100 bool 1101 1102config COMPAT_32BIT_TIME 1103 bool "Provide system calls for 32-bit time_t" 1104 default !64BIT || COMPAT 1105 help 1106 This enables 32 bit time_t support in addition to 64 bit time_t support. 1107 This is relevant on all 32-bit architectures, and 64-bit architectures 1108 as part of compat syscall handling. 1109 1110config ARCH_NO_PREEMPT 1111 bool 1112 1113config ARCH_EPHEMERAL_INODES 1114 def_bool n 1115 help 1116 An arch should select this symbol if it doesn't keep track of inode 1117 instances on its own, but instead relies on something else (e.g. the 1118 host kernel for an UML kernel). 1119 1120config ARCH_SUPPORTS_RT 1121 bool 1122 1123config CPU_NO_EFFICIENT_FFS 1124 def_bool n 1125 1126config HAVE_ARCH_VMAP_STACK 1127 def_bool n 1128 help 1129 An arch should select this symbol if it can support kernel stacks 1130 in vmalloc space. This means: 1131 1132 - vmalloc space must be large enough to hold many kernel stacks. 1133 This may rule out many 32-bit architectures. 1134 1135 - Stacks in vmalloc space need to work reliably. For example, if 1136 vmap page tables are created on demand, either this mechanism 1137 needs to work while the stack points to a virtual address with 1138 unpopulated page tables or arch code (switch_to() and switch_mm(), 1139 most likely) needs to ensure that the stack's page table entries 1140 are populated before running on a possibly unpopulated stack. 1141 1142 - If the stack overflows into a guard page, something reasonable 1143 should happen. The definition of "reasonable" is flexible, but 1144 instantly rebooting without logging anything would be unfriendly. 1145 1146config VMAP_STACK 1147 default y 1148 bool "Use a virtually-mapped stack" 1149 depends on HAVE_ARCH_VMAP_STACK 1150 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1151 help 1152 Enable this if you want the use virtually-mapped kernel stacks 1153 with guard pages. This causes kernel stack overflows to be 1154 caught immediately rather than causing difficult-to-diagnose 1155 corruption. 1156 1157 To use this with software KASAN modes, the architecture must support 1158 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1159 must be enabled. 1160 1161config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1162 def_bool n 1163 help 1164 An arch should select this symbol if it can support kernel stack 1165 offset randomization with calls to add_random_kstack_offset() 1166 during syscall entry and choose_random_kstack_offset() during 1167 syscall exit. Careful removal of -fstack-protector-strong and 1168 -fstack-protector should also be applied to the entry code and 1169 closely examined, as the artificial stack bump looks like an array 1170 to the compiler, so it will attempt to add canary checks regardless 1171 of the static branch state. 1172 1173config RANDOMIZE_KSTACK_OFFSET 1174 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1175 default y 1176 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1177 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1178 help 1179 The kernel stack offset can be randomized (after pt_regs) by 1180 roughly 5 bits of entropy, frustrating memory corruption 1181 attacks that depend on stack address determinism or 1182 cross-syscall address exposures. 1183 1184 The feature is controlled via the "randomize_kstack_offset=on/off" 1185 kernel boot param, and if turned off has zero overhead due to its use 1186 of static branches (see JUMP_LABEL). 1187 1188 If unsure, say Y. 1189 1190config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1191 bool "Default state of kernel stack offset randomization" 1192 depends on RANDOMIZE_KSTACK_OFFSET 1193 help 1194 Kernel stack offset randomization is controlled by kernel boot param 1195 "randomize_kstack_offset=on/off", and this config chooses the default 1196 boot state. 1197 1198config ARCH_OPTIONAL_KERNEL_RWX 1199 def_bool n 1200 1201config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1202 def_bool n 1203 1204config ARCH_HAS_STRICT_KERNEL_RWX 1205 def_bool n 1206 1207config STRICT_KERNEL_RWX 1208 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1209 depends on ARCH_HAS_STRICT_KERNEL_RWX 1210 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1211 help 1212 If this is set, kernel text and rodata memory will be made read-only, 1213 and non-text memory will be made non-executable. This provides 1214 protection against certain security exploits (e.g. executing the heap 1215 or modifying text) 1216 1217 These features are considered standard security practice these days. 1218 You should say Y here in almost all cases. 1219 1220config ARCH_HAS_STRICT_MODULE_RWX 1221 def_bool n 1222 1223config STRICT_MODULE_RWX 1224 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1225 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1226 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1227 help 1228 If this is set, module text and rodata memory will be made read-only, 1229 and non-text memory will be made non-executable. This provides 1230 protection against certain security exploits (e.g. writing to text) 1231 1232# select if the architecture provides an asm/dma-direct.h header 1233config ARCH_HAS_PHYS_TO_DMA 1234 bool 1235 1236config HAVE_ARCH_COMPILER_H 1237 bool 1238 help 1239 An architecture can select this if it provides an 1240 asm/compiler.h header that should be included after 1241 linux/compiler-*.h in order to override macro definitions that those 1242 headers generally provide. 1243 1244config HAVE_ARCH_PREL32_RELOCATIONS 1245 bool 1246 help 1247 May be selected by an architecture if it supports place-relative 1248 32-bit relocations, both in the toolchain and in the module loader, 1249 in which case relative references can be used in special sections 1250 for PCI fixup, initcalls etc which are only half the size on 64 bit 1251 architectures, and don't require runtime relocation on relocatable 1252 kernels. 1253 1254config ARCH_USE_MEMREMAP_PROT 1255 bool 1256 1257config LOCK_EVENT_COUNTS 1258 bool "Locking event counts collection" 1259 depends on DEBUG_FS 1260 help 1261 Enable light-weight counting of various locking related events 1262 in the system with minimal performance impact. This reduces 1263 the chance of application behavior change because of timing 1264 differences. The counts are reported via debugfs. 1265 1266# Select if the architecture has support for applying RELR relocations. 1267config ARCH_HAS_RELR 1268 bool 1269 1270config RELR 1271 bool "Use RELR relocation packing" 1272 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1273 default y 1274 help 1275 Store the kernel's dynamic relocations in the RELR relocation packing 1276 format. Requires a compatible linker (LLD supports this feature), as 1277 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1278 are compatible). 1279 1280config ARCH_HAS_MEM_ENCRYPT 1281 bool 1282 1283config ARCH_HAS_CC_PLATFORM 1284 bool 1285 1286config HAVE_SPARSE_SYSCALL_NR 1287 bool 1288 help 1289 An architecture should select this if its syscall numbering is sparse 1290 to save space. For example, MIPS architecture has a syscall array with 1291 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1292 related optimizations for a given architecture. 1293 1294config ARCH_HAS_VDSO_DATA 1295 bool 1296 1297config HAVE_STATIC_CALL 1298 bool 1299 1300config HAVE_STATIC_CALL_INLINE 1301 bool 1302 depends on HAVE_STATIC_CALL 1303 1304config HAVE_PREEMPT_DYNAMIC 1305 bool 1306 1307config HAVE_PREEMPT_DYNAMIC_CALL 1308 bool 1309 depends on HAVE_STATIC_CALL 1310 select HAVE_PREEMPT_DYNAMIC 1311 help 1312 An architecture should select this if it can handle the preemption 1313 model being selected at boot time using static calls. 1314 1315 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1316 preemption function will be patched directly. 1317 1318 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1319 call to a preemption function will go through a trampoline, and the 1320 trampoline will be patched. 1321 1322 It is strongly advised to support inline static call to avoid any 1323 overhead. 1324 1325config HAVE_PREEMPT_DYNAMIC_KEY 1326 bool 1327 depends on HAVE_ARCH_JUMP_LABEL && CC_HAS_ASM_GOTO 1328 select HAVE_PREEMPT_DYNAMIC 1329 help 1330 An architecture should select this if it can handle the preemption 1331 model being selected at boot time using static keys. 1332 1333 Each preemption function will be given an early return based on a 1334 static key. This should have slightly lower overhead than non-inline 1335 static calls, as this effectively inlines each trampoline into the 1336 start of its callee. This may avoid redundant work, and may 1337 integrate better with CFI schemes. 1338 1339 This will have greater overhead than using inline static calls as 1340 the call to the preemption function cannot be entirely elided. 1341 1342config ARCH_WANT_LD_ORPHAN_WARN 1343 bool 1344 help 1345 An arch should select this symbol once all linker sections are explicitly 1346 included, size-asserted, or discarded in the linker scripts. This is 1347 important because we never want expected sections to be placed heuristically 1348 by the linker, since the locations of such sections can change between linker 1349 versions. 1350 1351config HAVE_ARCH_PFN_VALID 1352 bool 1353 1354config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1355 bool 1356 1357config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1358 bool 1359 1360config ARCH_SPLIT_ARG64 1361 bool 1362 help 1363 If a 32-bit architecture requires 64-bit arguments to be split into 1364 pairs of 32-bit arguments, select this option. 1365 1366config ARCH_HAS_ELFCORE_COMPAT 1367 bool 1368 1369config ARCH_HAS_PARANOID_L1D_FLUSH 1370 bool 1371 1372config DYNAMIC_SIGFRAME 1373 bool 1374 1375# Select, if arch has a named attribute group bound to NUMA device nodes. 1376config HAVE_ARCH_NODE_DEV_GROUP 1377 bool 1378 1379source "kernel/gcov/Kconfig" 1380 1381source "scripts/gcc-plugins/Kconfig" 1382 1383endmenu 1384