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 HAVE_FUNCTION_ERROR_INJECTION 195 bool 196 197config HAVE_NMI 198 bool 199 200config TRACE_IRQFLAGS_SUPPORT 201 bool 202 203config TRACE_IRQFLAGS_NMI_SUPPORT 204 bool 205 206# 207# An arch should select this if it provides all these things: 208# 209# task_pt_regs() in asm/processor.h or asm/ptrace.h 210# arch_has_single_step() if there is hardware single-step support 211# arch_has_block_step() if there is hardware block-step support 212# asm/syscall.h supplying asm-generic/syscall.h interface 213# linux/regset.h user_regset interfaces 214# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 215# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 216# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 217# signal delivery calls tracehook_signal_handler() 218# 219config HAVE_ARCH_TRACEHOOK 220 bool 221 222config HAVE_DMA_CONTIGUOUS 223 bool 224 225config GENERIC_SMP_IDLE_THREAD 226 bool 227 228config GENERIC_IDLE_POLL_SETUP 229 bool 230 231config ARCH_HAS_FORTIFY_SOURCE 232 bool 233 help 234 An architecture should select this when it can successfully 235 build and run with CONFIG_FORTIFY_SOURCE. 236 237# 238# Select if the arch provides a historic keepinit alias for the retain_initrd 239# command line option 240# 241config ARCH_HAS_KEEPINITRD 242 bool 243 244# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 245config ARCH_HAS_SET_MEMORY 246 bool 247 248# Select if arch has all set_direct_map_invalid/default() functions 249config ARCH_HAS_SET_DIRECT_MAP 250 bool 251 252# 253# Select if the architecture provides the arch_dma_set_uncached symbol to 254# either provide an uncached segment alias for a DMA allocation, or 255# to remap the page tables in place. 256# 257config ARCH_HAS_DMA_SET_UNCACHED 258 bool 259 260# 261# Select if the architectures provides the arch_dma_clear_uncached symbol 262# to undo an in-place page table remap for uncached access. 263# 264config ARCH_HAS_DMA_CLEAR_UNCACHED 265 bool 266 267config ARCH_HAS_CPU_FINALIZE_INIT 268 bool 269 270# Select if arch init_task must go in the __init_task_data section 271config ARCH_TASK_STRUCT_ON_STACK 272 bool 273 274# Select if arch has its private alloc_task_struct() function 275config ARCH_TASK_STRUCT_ALLOCATOR 276 bool 277 278config HAVE_ARCH_THREAD_STRUCT_WHITELIST 279 bool 280 depends on !ARCH_TASK_STRUCT_ALLOCATOR 281 help 282 An architecture should select this to provide hardened usercopy 283 knowledge about what region of the thread_struct should be 284 whitelisted for copying to userspace. Normally this is only the 285 FPU registers. Specifically, arch_thread_struct_whitelist() 286 should be implemented. Without this, the entire thread_struct 287 field in task_struct will be left whitelisted. 288 289# Select if arch has its private alloc_thread_stack() function 290config ARCH_THREAD_STACK_ALLOCATOR 291 bool 292 293# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 294config ARCH_WANTS_DYNAMIC_TASK_STRUCT 295 bool 296 297config ARCH_WANTS_NO_INSTR 298 bool 299 help 300 An architecture should select this if the noinstr macro is being used on 301 functions to denote that the toolchain should avoid instrumenting such 302 functions and is required for correctness. 303 304config ARCH_32BIT_OFF_T 305 bool 306 depends on !64BIT 307 help 308 All new 32-bit architectures should have 64-bit off_t type on 309 userspace side which corresponds to the loff_t kernel type. This 310 is the requirement for modern ABIs. Some existing architectures 311 still support 32-bit off_t. This option is enabled for all such 312 architectures explicitly. 313 314# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 315config ARCH_32BIT_USTAT_F_TINODE 316 bool 317 318config HAVE_ASM_MODVERSIONS 319 bool 320 help 321 This symbol should be selected by an architecture if it provides 322 <asm/asm-prototypes.h> to support the module versioning for symbols 323 exported from assembly code. 324 325config HAVE_REGS_AND_STACK_ACCESS_API 326 bool 327 help 328 This symbol should be selected by an architecture if it supports 329 the API needed to access registers and stack entries from pt_regs, 330 declared in asm/ptrace.h 331 For example the kprobes-based event tracer needs this API. 332 333config HAVE_RSEQ 334 bool 335 depends on HAVE_REGS_AND_STACK_ACCESS_API 336 help 337 This symbol should be selected by an architecture if it 338 supports an implementation of restartable sequences. 339 340config HAVE_FUNCTION_ARG_ACCESS_API 341 bool 342 help 343 This symbol should be selected by an architecture if it supports 344 the API needed to access function arguments from pt_regs, 345 declared in asm/ptrace.h 346 347config HAVE_HW_BREAKPOINT 348 bool 349 depends on PERF_EVENTS 350 351config HAVE_MIXED_BREAKPOINTS_REGS 352 bool 353 depends on HAVE_HW_BREAKPOINT 354 help 355 Depending on the arch implementation of hardware breakpoints, 356 some of them have separate registers for data and instruction 357 breakpoints addresses, others have mixed registers to store 358 them but define the access type in a control register. 359 Select this option if your arch implements breakpoints under the 360 latter fashion. 361 362config HAVE_USER_RETURN_NOTIFIER 363 bool 364 365config HAVE_PERF_EVENTS_NMI 366 bool 367 help 368 System hardware can generate an NMI using the perf event 369 subsystem. Also has support for calculating CPU cycle events 370 to determine how many clock cycles in a given period. 371 372config HAVE_HARDLOCKUP_DETECTOR_PERF 373 bool 374 depends on HAVE_PERF_EVENTS_NMI 375 help 376 The arch chooses to use the generic perf-NMI-based hardlockup 377 detector. Must define HAVE_PERF_EVENTS_NMI. 378 379config HAVE_NMI_WATCHDOG 380 depends on HAVE_NMI 381 bool 382 help 383 The arch provides a low level NMI watchdog. It provides 384 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 385 386config HAVE_HARDLOCKUP_DETECTOR_ARCH 387 bool 388 select HAVE_NMI_WATCHDOG 389 help 390 The arch chooses to provide its own hardlockup detector, which is 391 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 392 interfaces and parameters provided by hardlockup detector subsystem. 393 394config HAVE_PERF_REGS 395 bool 396 help 397 Support selective register dumps for perf events. This includes 398 bit-mapping of each registers and a unique architecture id. 399 400config HAVE_PERF_USER_STACK_DUMP 401 bool 402 help 403 Support user stack dumps for perf event samples. This needs 404 access to the user stack pointer which is not unified across 405 architectures. 406 407config HAVE_ARCH_JUMP_LABEL 408 bool 409 410config HAVE_ARCH_JUMP_LABEL_RELATIVE 411 bool 412 413config MMU_GATHER_TABLE_FREE 414 bool 415 416config MMU_GATHER_RCU_TABLE_FREE 417 bool 418 select MMU_GATHER_TABLE_FREE 419 420config MMU_GATHER_PAGE_SIZE 421 bool 422 423config MMU_GATHER_NO_RANGE 424 bool 425 426config MMU_GATHER_NO_GATHER 427 bool 428 depends on MMU_GATHER_TABLE_FREE 429 430config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 431 bool 432 help 433 Temporary select until all architectures can be converted to have 434 irqs disabled over activate_mm. Architectures that do IPI based TLB 435 shootdowns should enable this. 436 437config ARCH_HAVE_NMI_SAFE_CMPXCHG 438 bool 439 440config HAVE_ALIGNED_STRUCT_PAGE 441 bool 442 help 443 This makes sure that struct pages are double word aligned and that 444 e.g. the SLUB allocator can perform double word atomic operations 445 on a struct page for better performance. However selecting this 446 might increase the size of a struct page by a word. 447 448config HAVE_CMPXCHG_LOCAL 449 bool 450 451config HAVE_CMPXCHG_DOUBLE 452 bool 453 454config ARCH_WEAK_RELEASE_ACQUIRE 455 bool 456 457config ARCH_WANT_IPC_PARSE_VERSION 458 bool 459 460config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 461 bool 462 463config ARCH_WANT_OLD_COMPAT_IPC 464 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 465 bool 466 467config HAVE_ARCH_SECCOMP 468 bool 469 help 470 An arch should select this symbol to support seccomp mode 1 (the fixed 471 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 472 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 473 - __NR_seccomp_read_32 474 - __NR_seccomp_write_32 475 - __NR_seccomp_exit_32 476 - __NR_seccomp_sigreturn_32 477 478config HAVE_ARCH_SECCOMP_FILTER 479 bool 480 select HAVE_ARCH_SECCOMP 481 help 482 An arch should select this symbol if it provides all of these things: 483 - all the requirements for HAVE_ARCH_SECCOMP 484 - syscall_get_arch() 485 - syscall_get_arguments() 486 - syscall_rollback() 487 - syscall_set_return_value() 488 - SIGSYS siginfo_t support 489 - secure_computing is called from a ptrace_event()-safe context 490 - secure_computing return value is checked and a return value of -1 491 results in the system call being skipped immediately. 492 - seccomp syscall wired up 493 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 494 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 495 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 496 497config SECCOMP 498 prompt "Enable seccomp to safely execute untrusted bytecode" 499 def_bool y 500 depends on HAVE_ARCH_SECCOMP 501 help 502 This kernel feature is useful for number crunching applications 503 that may need to handle untrusted bytecode during their 504 execution. By using pipes or other transports made available 505 to the process as file descriptors supporting the read/write 506 syscalls, it's possible to isolate those applications in their 507 own address space using seccomp. Once seccomp is enabled via 508 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 509 disabled and the task is only allowed to execute a few safe 510 syscalls defined by each seccomp mode. 511 512 If unsure, say Y. 513 514config SECCOMP_FILTER 515 def_bool y 516 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 517 help 518 Enable tasks to build secure computing environments defined 519 in terms of Berkeley Packet Filter programs which implement 520 task-defined system call filtering polices. 521 522 See Documentation/userspace-api/seccomp_filter.rst for details. 523 524config SECCOMP_CACHE_DEBUG 525 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 526 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 527 depends on PROC_FS 528 help 529 This enables the /proc/pid/seccomp_cache interface to monitor 530 seccomp cache data. The file format is subject to change. Reading 531 the file requires CAP_SYS_ADMIN. 532 533 This option is for debugging only. Enabling presents the risk that 534 an adversary may be able to infer the seccomp filter logic. 535 536 If unsure, say N. 537 538config HAVE_ARCH_STACKLEAK 539 bool 540 help 541 An architecture should select this if it has the code which 542 fills the used part of the kernel stack with the STACKLEAK_POISON 543 value before returning from system calls. 544 545config HAVE_STACKPROTECTOR 546 bool 547 help 548 An arch should select this symbol if: 549 - it has implemented a stack canary (e.g. __stack_chk_guard) 550 551config STACKPROTECTOR 552 bool "Stack Protector buffer overflow detection" 553 depends on HAVE_STACKPROTECTOR 554 depends on $(cc-option,-fstack-protector) 555 default y 556 help 557 This option turns on the "stack-protector" GCC feature. This 558 feature puts, at the beginning of functions, a canary value on 559 the stack just before the return address, and validates 560 the value just before actually returning. Stack based buffer 561 overflows (that need to overwrite this return address) now also 562 overwrite the canary, which gets detected and the attack is then 563 neutralized via a kernel panic. 564 565 Functions will have the stack-protector canary logic added if they 566 have an 8-byte or larger character array on the stack. 567 568 This feature requires gcc version 4.2 or above, or a distribution 569 gcc with the feature backported ("-fstack-protector"). 570 571 On an x86 "defconfig" build, this feature adds canary checks to 572 about 3% of all kernel functions, which increases kernel code size 573 by about 0.3%. 574 575config STACKPROTECTOR_STRONG 576 bool "Strong Stack Protector" 577 depends on STACKPROTECTOR 578 depends on $(cc-option,-fstack-protector-strong) 579 default y 580 help 581 Functions will have the stack-protector canary logic added in any 582 of the following conditions: 583 584 - local variable's address used as part of the right hand side of an 585 assignment or function argument 586 - local variable is an array (or union containing an array), 587 regardless of array type or length 588 - uses register local variables 589 590 This feature requires gcc version 4.9 or above, or a distribution 591 gcc with the feature backported ("-fstack-protector-strong"). 592 593 On an x86 "defconfig" build, this feature adds canary checks to 594 about 20% of all kernel functions, which increases the kernel code 595 size by about 2%. 596 597config ARCH_SUPPORTS_SHADOW_CALL_STACK 598 bool 599 help 600 An architecture should select this if it supports Clang's Shadow 601 Call Stack and implements runtime support for shadow stack 602 switching. 603 604config SHADOW_CALL_STACK 605 bool "Clang Shadow Call Stack" 606 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 607 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 608 depends on MMU 609 help 610 This option enables Clang's Shadow Call Stack, which uses a 611 shadow stack to protect function return addresses from being 612 overwritten by an attacker. More information can be found in 613 Clang's documentation: 614 615 https://clang.llvm.org/docs/ShadowCallStack.html 616 617 Note that security guarantees in the kernel differ from the 618 ones documented for user space. The kernel must store addresses 619 of shadow stacks in memory, which means an attacker capable of 620 reading and writing arbitrary memory may be able to locate them 621 and hijack control flow by modifying the stacks. 622 623config LTO 624 bool 625 help 626 Selected if the kernel will be built using the compiler's LTO feature. 627 628config LTO_CLANG 629 bool 630 select LTO 631 help 632 Selected if the kernel will be built using Clang's LTO feature. 633 634config ARCH_SUPPORTS_LTO_CLANG 635 bool 636 help 637 An architecture should select this option if it supports: 638 - compiling with Clang, 639 - compiling inline assembly with Clang's integrated assembler, 640 - and linking with LLD. 641 642config ARCH_SUPPORTS_LTO_CLANG_THIN 643 bool 644 help 645 An architecture should select this option if it can support Clang's 646 ThinLTO mode. 647 648config HAS_LTO_CLANG 649 def_bool y 650 # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510 651 depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && 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. 992 993# This allows to use a set of generic functions to determine mmap base 994# address by giving priority to top-down scheme only if the process 995# is not in legacy mode (compat task, unlimited stack size or 996# sysctl_legacy_va_layout). 997# Architecture that selects this option can provide its own version of: 998# - STACK_RND_MASK 999config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1000 bool 1001 depends on MMU 1002 select ARCH_HAS_ELF_RANDOMIZE 1003 1004config HAVE_STACK_VALIDATION 1005 bool 1006 help 1007 Architecture supports the 'objtool check' host tool command, which 1008 performs compile-time stack metadata validation. 1009 1010config HAVE_RELIABLE_STACKTRACE 1011 bool 1012 help 1013 Architecture has either save_stack_trace_tsk_reliable() or 1014 arch_stack_walk_reliable() function which only returns a stack trace 1015 if it can guarantee the trace is reliable. 1016 1017config HAVE_ARCH_HASH 1018 bool 1019 default n 1020 help 1021 If this is set, the architecture provides an <asm/hash.h> 1022 file which provides platform-specific implementations of some 1023 functions in <linux/hash.h> or fs/namei.c. 1024 1025config HAVE_ARCH_NVRAM_OPS 1026 bool 1027 1028config ISA_BUS_API 1029 def_bool ISA 1030 1031# 1032# ABI hall of shame 1033# 1034config CLONE_BACKWARDS 1035 bool 1036 help 1037 Architecture has tls passed as the 4th argument of clone(2), 1038 not the 5th one. 1039 1040config CLONE_BACKWARDS2 1041 bool 1042 help 1043 Architecture has the first two arguments of clone(2) swapped. 1044 1045config CLONE_BACKWARDS3 1046 bool 1047 help 1048 Architecture has tls passed as the 3rd argument of clone(2), 1049 not the 5th one. 1050 1051config ODD_RT_SIGACTION 1052 bool 1053 help 1054 Architecture has unusual rt_sigaction(2) arguments 1055 1056config OLD_SIGSUSPEND 1057 bool 1058 help 1059 Architecture has old sigsuspend(2) syscall, of one-argument variety 1060 1061config OLD_SIGSUSPEND3 1062 bool 1063 help 1064 Even weirder antique ABI - three-argument sigsuspend(2) 1065 1066config OLD_SIGACTION 1067 bool 1068 help 1069 Architecture has old sigaction(2) syscall. Nope, not the same 1070 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1071 but fairly different variant of sigaction(2), thanks to OSF/1 1072 compatibility... 1073 1074config COMPAT_OLD_SIGACTION 1075 bool 1076 1077config COMPAT_32BIT_TIME 1078 bool "Provide system calls for 32-bit time_t" 1079 default !64BIT || COMPAT 1080 help 1081 This enables 32 bit time_t support in addition to 64 bit time_t support. 1082 This is relevant on all 32-bit architectures, and 64-bit architectures 1083 as part of compat syscall handling. 1084 1085config ARCH_NO_PREEMPT 1086 bool 1087 1088config ARCH_EPHEMERAL_INODES 1089 def_bool n 1090 help 1091 An arch should select this symbol if it doesn't keep track of inode 1092 instances on its own, but instead relies on something else (e.g. the 1093 host kernel for an UML kernel). 1094 1095config ARCH_SUPPORTS_RT 1096 bool 1097 1098config CPU_NO_EFFICIENT_FFS 1099 def_bool n 1100 1101config HAVE_ARCH_VMAP_STACK 1102 def_bool n 1103 help 1104 An arch should select this symbol if it can support kernel stacks 1105 in vmalloc space. This means: 1106 1107 - vmalloc space must be large enough to hold many kernel stacks. 1108 This may rule out many 32-bit architectures. 1109 1110 - Stacks in vmalloc space need to work reliably. For example, if 1111 vmap page tables are created on demand, either this mechanism 1112 needs to work while the stack points to a virtual address with 1113 unpopulated page tables or arch code (switch_to() and switch_mm(), 1114 most likely) needs to ensure that the stack's page table entries 1115 are populated before running on a possibly unpopulated stack. 1116 1117 - If the stack overflows into a guard page, something reasonable 1118 should happen. The definition of "reasonable" is flexible, but 1119 instantly rebooting without logging anything would be unfriendly. 1120 1121config VMAP_STACK 1122 default y 1123 bool "Use a virtually-mapped stack" 1124 depends on HAVE_ARCH_VMAP_STACK 1125 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1126 help 1127 Enable this if you want the use virtually-mapped kernel stacks 1128 with guard pages. This causes kernel stack overflows to be 1129 caught immediately rather than causing difficult-to-diagnose 1130 corruption. 1131 1132 To use this with software KASAN modes, the architecture must support 1133 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1134 must be enabled. 1135 1136config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1137 def_bool n 1138 help 1139 An arch should select this symbol if it can support kernel stack 1140 offset randomization with calls to add_random_kstack_offset() 1141 during syscall entry and choose_random_kstack_offset() during 1142 syscall exit. Careful removal of -fstack-protector-strong and 1143 -fstack-protector should also be applied to the entry code and 1144 closely examined, as the artificial stack bump looks like an array 1145 to the compiler, so it will attempt to add canary checks regardless 1146 of the static branch state. 1147 1148config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1149 bool "Randomize kernel stack offset on syscall entry" 1150 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1151 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1152 help 1153 The kernel stack offset can be randomized (after pt_regs) by 1154 roughly 5 bits of entropy, frustrating memory corruption 1155 attacks that depend on stack address determinism or 1156 cross-syscall address exposures. This feature is controlled 1157 by kernel boot param "randomize_kstack_offset=on/off", and this 1158 config chooses the default boot state. 1159 1160config ARCH_OPTIONAL_KERNEL_RWX 1161 def_bool n 1162 1163config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1164 def_bool n 1165 1166config ARCH_HAS_STRICT_KERNEL_RWX 1167 def_bool n 1168 1169config STRICT_KERNEL_RWX 1170 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1171 depends on ARCH_HAS_STRICT_KERNEL_RWX 1172 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1173 help 1174 If this is set, kernel text and rodata memory will be made read-only, 1175 and non-text memory will be made non-executable. This provides 1176 protection against certain security exploits (e.g. executing the heap 1177 or modifying text) 1178 1179 These features are considered standard security practice these days. 1180 You should say Y here in almost all cases. 1181 1182config ARCH_HAS_STRICT_MODULE_RWX 1183 def_bool n 1184 1185config STRICT_MODULE_RWX 1186 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1187 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1188 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1189 help 1190 If this is set, module text and rodata memory will be made read-only, 1191 and non-text memory will be made non-executable. This provides 1192 protection against certain security exploits (e.g. writing to text) 1193 1194# select if the architecture provides an asm/dma-direct.h header 1195config ARCH_HAS_PHYS_TO_DMA 1196 bool 1197 1198config HAVE_ARCH_COMPILER_H 1199 bool 1200 help 1201 An architecture can select this if it provides an 1202 asm/compiler.h header that should be included after 1203 linux/compiler-*.h in order to override macro definitions that those 1204 headers generally provide. 1205 1206config HAVE_ARCH_PREL32_RELOCATIONS 1207 bool 1208 help 1209 May be selected by an architecture if it supports place-relative 1210 32-bit relocations, both in the toolchain and in the module loader, 1211 in which case relative references can be used in special sections 1212 for PCI fixup, initcalls etc which are only half the size on 64 bit 1213 architectures, and don't require runtime relocation on relocatable 1214 kernels. 1215 1216config ARCH_USE_MEMREMAP_PROT 1217 bool 1218 1219config LOCK_EVENT_COUNTS 1220 bool "Locking event counts collection" 1221 depends on DEBUG_FS 1222 help 1223 Enable light-weight counting of various locking related events 1224 in the system with minimal performance impact. This reduces 1225 the chance of application behavior change because of timing 1226 differences. The counts are reported via debugfs. 1227 1228# Select if the architecture has support for applying RELR relocations. 1229config ARCH_HAS_RELR 1230 bool 1231 1232config RELR 1233 bool "Use RELR relocation packing" 1234 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1235 default y 1236 help 1237 Store the kernel's dynamic relocations in the RELR relocation packing 1238 format. Requires a compatible linker (LLD supports this feature), as 1239 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1240 are compatible). 1241 1242config ARCH_HAS_MEM_ENCRYPT 1243 bool 1244 1245config ARCH_HAS_CC_PLATFORM 1246 bool 1247 1248config HAVE_SPARSE_SYSCALL_NR 1249 bool 1250 help 1251 An architecture should select this if its syscall numbering is sparse 1252 to save space. For example, MIPS architecture has a syscall array with 1253 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1254 related optimizations for a given architecture. 1255 1256config ARCH_HAS_VDSO_DATA 1257 bool 1258 1259config HAVE_STATIC_CALL 1260 bool 1261 1262config HAVE_STATIC_CALL_INLINE 1263 bool 1264 depends on HAVE_STATIC_CALL 1265 1266config HAVE_PREEMPT_DYNAMIC 1267 bool 1268 depends on HAVE_STATIC_CALL 1269 depends on GENERIC_ENTRY 1270 help 1271 Select this if the architecture support boot time preempt setting 1272 on top of static calls. It is strongly advised to support inline 1273 static call to avoid any overhead. 1274 1275config ARCH_WANT_LD_ORPHAN_WARN 1276 bool 1277 help 1278 An arch should select this symbol once all linker sections are explicitly 1279 included, size-asserted, or discarded in the linker scripts. This is 1280 important because we never want expected sections to be placed heuristically 1281 by the linker, since the locations of such sections can change between linker 1282 versions. 1283 1284config HAVE_ARCH_PFN_VALID 1285 bool 1286 1287config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1288 bool 1289 1290config ARCH_SPLIT_ARG64 1291 bool 1292 help 1293 If a 32-bit architecture requires 64-bit arguments to be split into 1294 pairs of 32-bit arguments, select this option. 1295 1296config ARCH_HAS_ELFCORE_COMPAT 1297 bool 1298 1299config ARCH_HAS_PARANOID_L1D_FLUSH 1300 bool 1301 1302config ARCH_HAVE_TRACE_MMIO_ACCESS 1303 bool 1304 1305config ARCH_HAS_NONLEAF_PMD_YOUNG 1306 bool 1307 help 1308 Architectures that select this option are capable of setting the 1309 accessed bit in non-leaf PMD entries when using them as part of linear 1310 address translations. Page table walkers that clear the accessed bit 1311 may use this capability to reduce their search space. 1312 1313source "kernel/gcov/Kconfig" 1314 1315source "scripts/gcc-plugins/Kconfig" 1316 1317endmenu 1318