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), and they must make no assumptions 858# that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag 859# can be used to prohibit arch-specific allocations from using hugepages to 860# help with this (e.g., modules may require it). 861# 862config HAVE_ARCH_HUGE_VMALLOC 863 depends on HAVE_ARCH_HUGE_VMAP 864 bool 865 866config ARCH_WANT_HUGE_PMD_SHARE 867 bool 868 869config HAVE_ARCH_SOFT_DIRTY 870 bool 871 872config HAVE_MOD_ARCH_SPECIFIC 873 bool 874 help 875 The arch uses struct mod_arch_specific to store data. Many arches 876 just need a simple module loader without arch specific data - those 877 should not enable this. 878 879config MODULES_USE_ELF_RELA 880 bool 881 help 882 Modules only use ELF RELA relocations. Modules with ELF REL 883 relocations will give an error. 884 885config MODULES_USE_ELF_REL 886 bool 887 help 888 Modules only use ELF REL relocations. Modules with ELF RELA 889 relocations will give an error. 890 891config HAVE_IRQ_EXIT_ON_IRQ_STACK 892 bool 893 help 894 Architecture doesn't only execute the irq handler on the irq stack 895 but also irq_exit(). This way we can process softirqs on this irq 896 stack instead of switching to a new one when we call __do_softirq() 897 in the end of an hardirq. 898 This spares a stack switch and improves cache usage on softirq 899 processing. 900 901config HAVE_SOFTIRQ_ON_OWN_STACK 902 bool 903 help 904 Architecture provides a function to run __do_softirq() on a 905 separate stack. 906 907config ALTERNATE_USER_ADDRESS_SPACE 908 bool 909 help 910 Architectures set this when the CPU uses separate address 911 spaces for kernel and user space pointers. In this case, the 912 access_ok() check on a __user pointer is skipped. 913 914config PGTABLE_LEVELS 915 int 916 default 2 917 918config ARCH_HAS_ELF_RANDOMIZE 919 bool 920 help 921 An architecture supports choosing randomized locations for 922 stack, mmap, brk, and ET_DYN. Defined functions: 923 - arch_mmap_rnd() 924 - arch_randomize_brk() 925 926config HAVE_ARCH_MMAP_RND_BITS 927 bool 928 help 929 An arch should select this symbol if it supports setting a variable 930 number of bits for use in establishing the base address for mmap 931 allocations, has MMU enabled and provides values for both: 932 - ARCH_MMAP_RND_BITS_MIN 933 - ARCH_MMAP_RND_BITS_MAX 934 935config HAVE_EXIT_THREAD 936 bool 937 help 938 An architecture implements exit_thread. 939 940config ARCH_MMAP_RND_BITS_MIN 941 int 942 943config ARCH_MMAP_RND_BITS_MAX 944 int 945 946config ARCH_MMAP_RND_BITS_DEFAULT 947 int 948 949config ARCH_MMAP_RND_BITS 950 int "Number of bits to use for ASLR of mmap base address" if EXPERT 951 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 952 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 953 default ARCH_MMAP_RND_BITS_MIN 954 depends on HAVE_ARCH_MMAP_RND_BITS 955 help 956 This value can be used to select the number of bits to use to 957 determine the random offset to the base address of vma regions 958 resulting from mmap allocations. This value will be bounded 959 by the architecture's minimum and maximum supported values. 960 961 This value can be changed after boot using the 962 /proc/sys/vm/mmap_rnd_bits tunable 963 964config HAVE_ARCH_MMAP_RND_COMPAT_BITS 965 bool 966 help 967 An arch should select this symbol if it supports running applications 968 in compatibility mode, supports setting a variable number of bits for 969 use in establishing the base address for mmap allocations, has MMU 970 enabled and provides values for both: 971 - ARCH_MMAP_RND_COMPAT_BITS_MIN 972 - ARCH_MMAP_RND_COMPAT_BITS_MAX 973 974config ARCH_MMAP_RND_COMPAT_BITS_MIN 975 int 976 977config ARCH_MMAP_RND_COMPAT_BITS_MAX 978 int 979 980config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 981 int 982 983config ARCH_MMAP_RND_COMPAT_BITS 984 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 985 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 986 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 987 default ARCH_MMAP_RND_COMPAT_BITS_MIN 988 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 989 help 990 This value can be used to select the number of bits to use to 991 determine the random offset to the base address of vma regions 992 resulting from mmap allocations for compatible applications This 993 value will be bounded by the architecture's minimum and maximum 994 supported values. 995 996 This value can be changed after boot using the 997 /proc/sys/vm/mmap_rnd_compat_bits tunable 998 999config HAVE_ARCH_COMPAT_MMAP_BASES 1000 bool 1001 help 1002 This allows 64bit applications to invoke 32-bit mmap() syscall 1003 and vice-versa 32-bit applications to call 64-bit mmap(). 1004 Required for applications doing different bitness syscalls. 1005 1006config PAGE_SIZE_LESS_THAN_64KB 1007 def_bool y 1008 depends on !ARM64_64K_PAGES 1009 depends on !IA64_PAGE_SIZE_64KB 1010 depends on !PAGE_SIZE_64KB 1011 depends on !PARISC_PAGE_SIZE_64KB 1012 depends on !PPC_64K_PAGES 1013 depends on PAGE_SIZE_LESS_THAN_256KB 1014 1015config PAGE_SIZE_LESS_THAN_256KB 1016 def_bool y 1017 depends on !PPC_256K_PAGES 1018 depends on !PAGE_SIZE_256KB 1019 1020# This allows to use a set of generic functions to determine mmap base 1021# address by giving priority to top-down scheme only if the process 1022# is not in legacy mode (compat task, unlimited stack size or 1023# sysctl_legacy_va_layout). 1024# Architecture that selects this option can provide its own version of: 1025# - STACK_RND_MASK 1026config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1027 bool 1028 depends on MMU 1029 select ARCH_HAS_ELF_RANDOMIZE 1030 1031config HAVE_STACK_VALIDATION 1032 bool 1033 help 1034 Architecture supports the 'objtool check' host tool command, which 1035 performs compile-time stack metadata validation. 1036 1037config HAVE_RELIABLE_STACKTRACE 1038 bool 1039 help 1040 Architecture has either save_stack_trace_tsk_reliable() or 1041 arch_stack_walk_reliable() function which only returns a stack trace 1042 if it can guarantee the trace is reliable. 1043 1044config HAVE_ARCH_HASH 1045 bool 1046 default n 1047 help 1048 If this is set, the architecture provides an <asm/hash.h> 1049 file which provides platform-specific implementations of some 1050 functions in <linux/hash.h> or fs/namei.c. 1051 1052config HAVE_ARCH_NVRAM_OPS 1053 bool 1054 1055config ISA_BUS_API 1056 def_bool ISA 1057 1058# 1059# ABI hall of shame 1060# 1061config CLONE_BACKWARDS 1062 bool 1063 help 1064 Architecture has tls passed as the 4th argument of clone(2), 1065 not the 5th one. 1066 1067config CLONE_BACKWARDS2 1068 bool 1069 help 1070 Architecture has the first two arguments of clone(2) swapped. 1071 1072config CLONE_BACKWARDS3 1073 bool 1074 help 1075 Architecture has tls passed as the 3rd argument of clone(2), 1076 not the 5th one. 1077 1078config ODD_RT_SIGACTION 1079 bool 1080 help 1081 Architecture has unusual rt_sigaction(2) arguments 1082 1083config OLD_SIGSUSPEND 1084 bool 1085 help 1086 Architecture has old sigsuspend(2) syscall, of one-argument variety 1087 1088config OLD_SIGSUSPEND3 1089 bool 1090 help 1091 Even weirder antique ABI - three-argument sigsuspend(2) 1092 1093config OLD_SIGACTION 1094 bool 1095 help 1096 Architecture has old sigaction(2) syscall. Nope, not the same 1097 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1098 but fairly different variant of sigaction(2), thanks to OSF/1 1099 compatibility... 1100 1101config COMPAT_OLD_SIGACTION 1102 bool 1103 1104config COMPAT_32BIT_TIME 1105 bool "Provide system calls for 32-bit time_t" 1106 default !64BIT || COMPAT 1107 help 1108 This enables 32 bit time_t support in addition to 64 bit time_t support. 1109 This is relevant on all 32-bit architectures, and 64-bit architectures 1110 as part of compat syscall handling. 1111 1112config ARCH_NO_PREEMPT 1113 bool 1114 1115config ARCH_EPHEMERAL_INODES 1116 def_bool n 1117 help 1118 An arch should select this symbol if it doesn't keep track of inode 1119 instances on its own, but instead relies on something else (e.g. the 1120 host kernel for an UML kernel). 1121 1122config ARCH_SUPPORTS_RT 1123 bool 1124 1125config CPU_NO_EFFICIENT_FFS 1126 def_bool n 1127 1128config HAVE_ARCH_VMAP_STACK 1129 def_bool n 1130 help 1131 An arch should select this symbol if it can support kernel stacks 1132 in vmalloc space. This means: 1133 1134 - vmalloc space must be large enough to hold many kernel stacks. 1135 This may rule out many 32-bit architectures. 1136 1137 - Stacks in vmalloc space need to work reliably. For example, if 1138 vmap page tables are created on demand, either this mechanism 1139 needs to work while the stack points to a virtual address with 1140 unpopulated page tables or arch code (switch_to() and switch_mm(), 1141 most likely) needs to ensure that the stack's page table entries 1142 are populated before running on a possibly unpopulated stack. 1143 1144 - If the stack overflows into a guard page, something reasonable 1145 should happen. The definition of "reasonable" is flexible, but 1146 instantly rebooting without logging anything would be unfriendly. 1147 1148config VMAP_STACK 1149 default y 1150 bool "Use a virtually-mapped stack" 1151 depends on HAVE_ARCH_VMAP_STACK 1152 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1153 help 1154 Enable this if you want the use virtually-mapped kernel stacks 1155 with guard pages. This causes kernel stack overflows to be 1156 caught immediately rather than causing difficult-to-diagnose 1157 corruption. 1158 1159 To use this with software KASAN modes, the architecture must support 1160 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1161 must be enabled. 1162 1163config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1164 def_bool n 1165 help 1166 An arch should select this symbol if it can support kernel stack 1167 offset randomization with calls to add_random_kstack_offset() 1168 during syscall entry and choose_random_kstack_offset() during 1169 syscall exit. Careful removal of -fstack-protector-strong and 1170 -fstack-protector should also be applied to the entry code and 1171 closely examined, as the artificial stack bump looks like an array 1172 to the compiler, so it will attempt to add canary checks regardless 1173 of the static branch state. 1174 1175config RANDOMIZE_KSTACK_OFFSET 1176 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT 1177 default y 1178 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1179 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000 1180 help 1181 The kernel stack offset can be randomized (after pt_regs) by 1182 roughly 5 bits of entropy, frustrating memory corruption 1183 attacks that depend on stack address determinism or 1184 cross-syscall address exposures. 1185 1186 The feature is controlled via the "randomize_kstack_offset=on/off" 1187 kernel boot param, and if turned off has zero overhead due to its use 1188 of static branches (see JUMP_LABEL). 1189 1190 If unsure, say Y. 1191 1192config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1193 bool "Default state of kernel stack offset randomization" 1194 depends on RANDOMIZE_KSTACK_OFFSET 1195 help 1196 Kernel stack offset randomization is controlled by kernel boot param 1197 "randomize_kstack_offset=on/off", and this config chooses the default 1198 boot state. 1199 1200config ARCH_OPTIONAL_KERNEL_RWX 1201 def_bool n 1202 1203config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1204 def_bool n 1205 1206config ARCH_HAS_STRICT_KERNEL_RWX 1207 def_bool n 1208 1209config STRICT_KERNEL_RWX 1210 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1211 depends on ARCH_HAS_STRICT_KERNEL_RWX 1212 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1213 help 1214 If this is set, kernel text and rodata memory will be made read-only, 1215 and non-text memory will be made non-executable. This provides 1216 protection against certain security exploits (e.g. executing the heap 1217 or modifying text) 1218 1219 These features are considered standard security practice these days. 1220 You should say Y here in almost all cases. 1221 1222config ARCH_HAS_STRICT_MODULE_RWX 1223 def_bool n 1224 1225config STRICT_MODULE_RWX 1226 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1227 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1228 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1229 help 1230 If this is set, module text and rodata memory will be made read-only, 1231 and non-text memory will be made non-executable. This provides 1232 protection against certain security exploits (e.g. writing to text) 1233 1234# select if the architecture provides an asm/dma-direct.h header 1235config ARCH_HAS_PHYS_TO_DMA 1236 bool 1237 1238config HAVE_ARCH_COMPILER_H 1239 bool 1240 help 1241 An architecture can select this if it provides an 1242 asm/compiler.h header that should be included after 1243 linux/compiler-*.h in order to override macro definitions that those 1244 headers generally provide. 1245 1246config HAVE_ARCH_PREL32_RELOCATIONS 1247 bool 1248 help 1249 May be selected by an architecture if it supports place-relative 1250 32-bit relocations, both in the toolchain and in the module loader, 1251 in which case relative references can be used in special sections 1252 for PCI fixup, initcalls etc which are only half the size on 64 bit 1253 architectures, and don't require runtime relocation on relocatable 1254 kernels. 1255 1256config ARCH_USE_MEMREMAP_PROT 1257 bool 1258 1259config LOCK_EVENT_COUNTS 1260 bool "Locking event counts collection" 1261 depends on DEBUG_FS 1262 help 1263 Enable light-weight counting of various locking related events 1264 in the system with minimal performance impact. This reduces 1265 the chance of application behavior change because of timing 1266 differences. The counts are reported via debugfs. 1267 1268# Select if the architecture has support for applying RELR relocations. 1269config ARCH_HAS_RELR 1270 bool 1271 1272config RELR 1273 bool "Use RELR relocation packing" 1274 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1275 default y 1276 help 1277 Store the kernel's dynamic relocations in the RELR relocation packing 1278 format. Requires a compatible linker (LLD supports this feature), as 1279 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1280 are compatible). 1281 1282config ARCH_HAS_MEM_ENCRYPT 1283 bool 1284 1285config ARCH_HAS_CC_PLATFORM 1286 bool 1287 1288config HAVE_SPARSE_SYSCALL_NR 1289 bool 1290 help 1291 An architecture should select this if its syscall numbering is sparse 1292 to save space. For example, MIPS architecture has a syscall array with 1293 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1294 related optimizations for a given architecture. 1295 1296config ARCH_HAS_VDSO_DATA 1297 bool 1298 1299config HAVE_STATIC_CALL 1300 bool 1301 1302config HAVE_STATIC_CALL_INLINE 1303 bool 1304 depends on HAVE_STATIC_CALL 1305 1306config HAVE_PREEMPT_DYNAMIC 1307 bool 1308 1309config HAVE_PREEMPT_DYNAMIC_CALL 1310 bool 1311 depends on HAVE_STATIC_CALL 1312 select HAVE_PREEMPT_DYNAMIC 1313 help 1314 An architecture should select this if it can handle the preemption 1315 model being selected at boot time using static calls. 1316 1317 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a 1318 preemption function will be patched directly. 1319 1320 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any 1321 call to a preemption function will go through a trampoline, and the 1322 trampoline will be patched. 1323 1324 It is strongly advised to support inline static call to avoid any 1325 overhead. 1326 1327config HAVE_PREEMPT_DYNAMIC_KEY 1328 bool 1329 depends on HAVE_ARCH_JUMP_LABEL && CC_HAS_ASM_GOTO 1330 select HAVE_PREEMPT_DYNAMIC 1331 help 1332 An architecture should select this if it can handle the preemption 1333 model being selected at boot time using static keys. 1334 1335 Each preemption function will be given an early return based on a 1336 static key. This should have slightly lower overhead than non-inline 1337 static calls, as this effectively inlines each trampoline into the 1338 start of its callee. This may avoid redundant work, and may 1339 integrate better with CFI schemes. 1340 1341 This will have greater overhead than using inline static calls as 1342 the call to the preemption function cannot be entirely elided. 1343 1344config ARCH_WANT_LD_ORPHAN_WARN 1345 bool 1346 help 1347 An arch should select this symbol once all linker sections are explicitly 1348 included, size-asserted, or discarded in the linker scripts. This is 1349 important because we never want expected sections to be placed heuristically 1350 by the linker, since the locations of such sections can change between linker 1351 versions. 1352 1353config HAVE_ARCH_PFN_VALID 1354 bool 1355 1356config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1357 bool 1358 1359config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1360 bool 1361 1362config ARCH_SPLIT_ARG64 1363 bool 1364 help 1365 If a 32-bit architecture requires 64-bit arguments to be split into 1366 pairs of 32-bit arguments, select this option. 1367 1368config ARCH_HAS_ELFCORE_COMPAT 1369 bool 1370 1371config ARCH_HAS_PARANOID_L1D_FLUSH 1372 bool 1373 1374config DYNAMIC_SIGFRAME 1375 bool 1376 1377# Select, if arch has a named attribute group bound to NUMA device nodes. 1378config HAVE_ARCH_NODE_DEV_GROUP 1379 bool 1380 1381source "kernel/gcov/Kconfig" 1382 1383source "scripts/gcc-plugins/Kconfig" 1384 1385endmenu 1386