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