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 202 203# 204# An arch should select this if it provides all these things: 205# 206# task_pt_regs() in asm/processor.h or asm/ptrace.h 207# arch_has_single_step() if there is hardware single-step support 208# arch_has_block_step() if there is hardware block-step support 209# asm/syscall.h supplying asm-generic/syscall.h interface 210# linux/regset.h user_regset interfaces 211# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 212# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 213# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 214# signal delivery calls tracehook_signal_handler() 215# 216config HAVE_ARCH_TRACEHOOK 217 bool 218 219config HAVE_DMA_CONTIGUOUS 220 bool 221 222config GENERIC_SMP_IDLE_THREAD 223 bool 224 225config GENERIC_IDLE_POLL_SETUP 226 bool 227 228config ARCH_HAS_FORTIFY_SOURCE 229 bool 230 help 231 An architecture should select this when it can successfully 232 build and run with CONFIG_FORTIFY_SOURCE. 233 234# 235# Select if the arch provides a historic keepinit alias for the retain_initrd 236# command line option 237# 238config ARCH_HAS_KEEPINITRD 239 bool 240 241# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 242config ARCH_HAS_SET_MEMORY 243 bool 244 245# Select if arch has all set_direct_map_invalid/default() functions 246config ARCH_HAS_SET_DIRECT_MAP 247 bool 248 249# 250# Select if the architecture provides the arch_dma_set_uncached symbol to 251# either provide an uncached segment alias for a DMA allocation, or 252# to remap the page tables in place. 253# 254config ARCH_HAS_DMA_SET_UNCACHED 255 bool 256 257# 258# Select if the architectures provides the arch_dma_clear_uncached symbol 259# to undo an in-place page table remap for uncached access. 260# 261config ARCH_HAS_DMA_CLEAR_UNCACHED 262 bool 263 264# Select if arch init_task must go in the __init_task_data section 265config ARCH_TASK_STRUCT_ON_STACK 266 bool 267 268# Select if arch has its private alloc_task_struct() function 269config ARCH_TASK_STRUCT_ALLOCATOR 270 bool 271 272config HAVE_ARCH_THREAD_STRUCT_WHITELIST 273 bool 274 depends on !ARCH_TASK_STRUCT_ALLOCATOR 275 help 276 An architecture should select this to provide hardened usercopy 277 knowledge about what region of the thread_struct should be 278 whitelisted for copying to userspace. Normally this is only the 279 FPU registers. Specifically, arch_thread_struct_whitelist() 280 should be implemented. Without this, the entire thread_struct 281 field in task_struct will be left whitelisted. 282 283# Select if arch has its private alloc_thread_stack() function 284config ARCH_THREAD_STACK_ALLOCATOR 285 bool 286 287# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 288config ARCH_WANTS_DYNAMIC_TASK_STRUCT 289 bool 290 291config ARCH_WANTS_NO_INSTR 292 bool 293 help 294 An architecture should select this if the noinstr macro is being used on 295 functions to denote that the toolchain should avoid instrumenting such 296 functions and is required for correctness. 297 298config ARCH_32BIT_OFF_T 299 bool 300 depends on !64BIT 301 help 302 All new 32-bit architectures should have 64-bit off_t type on 303 userspace side which corresponds to the loff_t kernel type. This 304 is the requirement for modern ABIs. Some existing architectures 305 still support 32-bit off_t. This option is enabled for all such 306 architectures explicitly. 307 308# Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 309config ARCH_32BIT_USTAT_F_TINODE 310 bool 311 312config HAVE_ASM_MODVERSIONS 313 bool 314 help 315 This symbol should be selected by an architecture if it provides 316 <asm/asm-prototypes.h> to support the module versioning for symbols 317 exported from assembly code. 318 319config HAVE_REGS_AND_STACK_ACCESS_API 320 bool 321 help 322 This symbol should be selected by an architecture if it supports 323 the API needed to access registers and stack entries from pt_regs, 324 declared in asm/ptrace.h 325 For example the kprobes-based event tracer needs this API. 326 327config HAVE_RSEQ 328 bool 329 depends on HAVE_REGS_AND_STACK_ACCESS_API 330 help 331 This symbol should be selected by an architecture if it 332 supports an implementation of restartable sequences. 333 334config HAVE_FUNCTION_ARG_ACCESS_API 335 bool 336 help 337 This symbol should be selected by an architecture if it supports 338 the API needed to access function arguments from pt_regs, 339 declared in asm/ptrace.h 340 341config HAVE_HW_BREAKPOINT 342 bool 343 depends on PERF_EVENTS 344 345config HAVE_MIXED_BREAKPOINTS_REGS 346 bool 347 depends on HAVE_HW_BREAKPOINT 348 help 349 Depending on the arch implementation of hardware breakpoints, 350 some of them have separate registers for data and instruction 351 breakpoints addresses, others have mixed registers to store 352 them but define the access type in a control register. 353 Select this option if your arch implements breakpoints under the 354 latter fashion. 355 356config HAVE_USER_RETURN_NOTIFIER 357 bool 358 359config HAVE_PERF_EVENTS_NMI 360 bool 361 help 362 System hardware can generate an NMI using the perf event 363 subsystem. Also has support for calculating CPU cycle events 364 to determine how many clock cycles in a given period. 365 366config HAVE_HARDLOCKUP_DETECTOR_PERF 367 bool 368 depends on HAVE_PERF_EVENTS_NMI 369 help 370 The arch chooses to use the generic perf-NMI-based hardlockup 371 detector. Must define HAVE_PERF_EVENTS_NMI. 372 373config HAVE_NMI_WATCHDOG 374 depends on HAVE_NMI 375 bool 376 help 377 The arch provides a low level NMI watchdog. It provides 378 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 379 380config HAVE_HARDLOCKUP_DETECTOR_ARCH 381 bool 382 select HAVE_NMI_WATCHDOG 383 help 384 The arch chooses to provide its own hardlockup detector, which is 385 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 386 interfaces and parameters provided by hardlockup detector subsystem. 387 388config HAVE_PERF_REGS 389 bool 390 help 391 Support selective register dumps for perf events. This includes 392 bit-mapping of each registers and a unique architecture id. 393 394config HAVE_PERF_USER_STACK_DUMP 395 bool 396 help 397 Support user stack dumps for perf event samples. This needs 398 access to the user stack pointer which is not unified across 399 architectures. 400 401config HAVE_ARCH_JUMP_LABEL 402 bool 403 404config HAVE_ARCH_JUMP_LABEL_RELATIVE 405 bool 406 407config MMU_GATHER_TABLE_FREE 408 bool 409 410config MMU_GATHER_RCU_TABLE_FREE 411 bool 412 select MMU_GATHER_TABLE_FREE 413 414config MMU_GATHER_PAGE_SIZE 415 bool 416 417config MMU_GATHER_NO_RANGE 418 bool 419 420config MMU_GATHER_NO_GATHER 421 bool 422 depends on MMU_GATHER_TABLE_FREE 423 424config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 425 bool 426 help 427 Temporary select until all architectures can be converted to have 428 irqs disabled over activate_mm. Architectures that do IPI based TLB 429 shootdowns should enable this. 430 431config ARCH_HAVE_NMI_SAFE_CMPXCHG 432 bool 433 434config HAVE_ALIGNED_STRUCT_PAGE 435 bool 436 help 437 This makes sure that struct pages are double word aligned and that 438 e.g. the SLUB allocator can perform double word atomic operations 439 on a struct page for better performance. However selecting this 440 might increase the size of a struct page by a word. 441 442config HAVE_CMPXCHG_LOCAL 443 bool 444 445config HAVE_CMPXCHG_DOUBLE 446 bool 447 448config ARCH_WEAK_RELEASE_ACQUIRE 449 bool 450 451config ARCH_WANT_IPC_PARSE_VERSION 452 bool 453 454config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 455 bool 456 457config ARCH_WANT_OLD_COMPAT_IPC 458 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 459 bool 460 461config HAVE_ARCH_SECCOMP 462 bool 463 help 464 An arch should select this symbol to support seccomp mode 1 (the fixed 465 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 466 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 467 - __NR_seccomp_read_32 468 - __NR_seccomp_write_32 469 - __NR_seccomp_exit_32 470 - __NR_seccomp_sigreturn_32 471 472config HAVE_ARCH_SECCOMP_FILTER 473 bool 474 select HAVE_ARCH_SECCOMP 475 help 476 An arch should select this symbol if it provides all of these things: 477 - all the requirements for HAVE_ARCH_SECCOMP 478 - syscall_get_arch() 479 - syscall_get_arguments() 480 - syscall_rollback() 481 - syscall_set_return_value() 482 - SIGSYS siginfo_t support 483 - secure_computing is called from a ptrace_event()-safe context 484 - secure_computing return value is checked and a return value of -1 485 results in the system call being skipped immediately. 486 - seccomp syscall wired up 487 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 488 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 489 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 490 491config SECCOMP 492 prompt "Enable seccomp to safely execute untrusted bytecode" 493 def_bool y 494 depends on HAVE_ARCH_SECCOMP 495 help 496 This kernel feature is useful for number crunching applications 497 that may need to handle untrusted bytecode during their 498 execution. By using pipes or other transports made available 499 to the process as file descriptors supporting the read/write 500 syscalls, it's possible to isolate those applications in their 501 own address space using seccomp. Once seccomp is enabled via 502 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 503 disabled and the task is only allowed to execute a few safe 504 syscalls defined by each seccomp mode. 505 506 If unsure, say Y. 507 508config SECCOMP_FILTER 509 def_bool y 510 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 511 help 512 Enable tasks to build secure computing environments defined 513 in terms of Berkeley Packet Filter programs which implement 514 task-defined system call filtering polices. 515 516 See Documentation/userspace-api/seccomp_filter.rst for details. 517 518config SECCOMP_CACHE_DEBUG 519 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 520 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 521 depends on PROC_FS 522 help 523 This enables the /proc/pid/seccomp_cache interface to monitor 524 seccomp cache data. The file format is subject to change. Reading 525 the file requires CAP_SYS_ADMIN. 526 527 This option is for debugging only. Enabling presents the risk that 528 an adversary may be able to infer the seccomp filter logic. 529 530 If unsure, say N. 531 532config HAVE_ARCH_STACKLEAK 533 bool 534 help 535 An architecture should select this if it has the code which 536 fills the used part of the kernel stack with the STACKLEAK_POISON 537 value before returning from system calls. 538 539config HAVE_STACKPROTECTOR 540 bool 541 help 542 An arch should select this symbol if: 543 - it has implemented a stack canary (e.g. __stack_chk_guard) 544 545config STACKPROTECTOR 546 bool "Stack Protector buffer overflow detection" 547 depends on HAVE_STACKPROTECTOR 548 depends on $(cc-option,-fstack-protector) 549 default y 550 help 551 This option turns on the "stack-protector" GCC feature. This 552 feature puts, at the beginning of functions, a canary value on 553 the stack just before the return address, and validates 554 the value just before actually returning. Stack based buffer 555 overflows (that need to overwrite this return address) now also 556 overwrite the canary, which gets detected and the attack is then 557 neutralized via a kernel panic. 558 559 Functions will have the stack-protector canary logic added if they 560 have an 8-byte or larger character array on the stack. 561 562 This feature requires gcc version 4.2 or above, or a distribution 563 gcc with the feature backported ("-fstack-protector"). 564 565 On an x86 "defconfig" build, this feature adds canary checks to 566 about 3% of all kernel functions, which increases kernel code size 567 by about 0.3%. 568 569config STACKPROTECTOR_STRONG 570 bool "Strong Stack Protector" 571 depends on STACKPROTECTOR 572 depends on $(cc-option,-fstack-protector-strong) 573 default y 574 help 575 Functions will have the stack-protector canary logic added in any 576 of the following conditions: 577 578 - local variable's address used as part of the right hand side of an 579 assignment or function argument 580 - local variable is an array (or union containing an array), 581 regardless of array type or length 582 - uses register local variables 583 584 This feature requires gcc version 4.9 or above, or a distribution 585 gcc with the feature backported ("-fstack-protector-strong"). 586 587 On an x86 "defconfig" build, this feature adds canary checks to 588 about 20% of all kernel functions, which increases the kernel code 589 size by about 2%. 590 591config ARCH_SUPPORTS_SHADOW_CALL_STACK 592 bool 593 help 594 An architecture should select this if it supports Clang's Shadow 595 Call Stack and implements runtime support for shadow stack 596 switching. 597 598config SHADOW_CALL_STACK 599 bool "Clang Shadow Call Stack" 600 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 601 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 602 help 603 This option enables Clang's Shadow Call Stack, which uses a 604 shadow stack to protect function return addresses from being 605 overwritten by an attacker. More information can be found in 606 Clang's documentation: 607 608 https://clang.llvm.org/docs/ShadowCallStack.html 609 610 Note that security guarantees in the kernel differ from the 611 ones documented for user space. The kernel must store addresses 612 of shadow stacks in memory, which means an attacker capable of 613 reading and writing arbitrary memory may be able to locate them 614 and hijack control flow by modifying the stacks. 615 616config LTO 617 bool 618 help 619 Selected if the kernel will be built using the compiler's LTO feature. 620 621config LTO_CLANG 622 bool 623 select LTO 624 help 625 Selected if the kernel will be built using Clang's LTO feature. 626 627config ARCH_SUPPORTS_LTO_CLANG 628 bool 629 help 630 An architecture should select this option if it supports: 631 - compiling with Clang, 632 - compiling inline assembly with Clang's integrated assembler, 633 - and linking with LLD. 634 635config ARCH_SUPPORTS_LTO_CLANG_THIN 636 bool 637 help 638 An architecture should select this option if it can support Clang's 639 ThinLTO mode. 640 641config HAS_LTO_CLANG 642 def_bool y 643 # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510 644 depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM 645 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 646 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 647 depends on ARCH_SUPPORTS_LTO_CLANG 648 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 649 depends on !KASAN || KASAN_HW_TAGS 650 depends on !GCOV_KERNEL 651 help 652 The compiler and Kconfig options support building with Clang's 653 LTO. 654 655choice 656 prompt "Link Time Optimization (LTO)" 657 default LTO_NONE 658 help 659 This option enables Link Time Optimization (LTO), which allows the 660 compiler to optimize binaries globally. 661 662 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 663 so it's disabled by default. 664 665config LTO_NONE 666 bool "None" 667 help 668 Build the kernel normally, without Link Time Optimization (LTO). 669 670config LTO_CLANG_FULL 671 bool "Clang Full LTO (EXPERIMENTAL)" 672 depends on HAS_LTO_CLANG 673 depends on !COMPILE_TEST 674 select LTO_CLANG 675 help 676 This option enables Clang's full Link Time Optimization (LTO), which 677 allows the compiler to optimize the kernel globally. If you enable 678 this option, the compiler generates LLVM bitcode instead of ELF 679 object files, and the actual compilation from bitcode happens at 680 the LTO link step, which may take several minutes depending on the 681 kernel configuration. More information can be found from LLVM's 682 documentation: 683 684 https://llvm.org/docs/LinkTimeOptimization.html 685 686 During link time, this option can use a large amount of RAM, and 687 may take much longer than the ThinLTO option. 688 689config LTO_CLANG_THIN 690 bool "Clang ThinLTO (EXPERIMENTAL)" 691 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 692 select LTO_CLANG 693 help 694 This option enables Clang's ThinLTO, which allows for parallel 695 optimization and faster incremental compiles compared to the 696 CONFIG_LTO_CLANG_FULL option. More information can be found 697 from Clang's documentation: 698 699 https://clang.llvm.org/docs/ThinLTO.html 700 701 If unsure, say Y. 702endchoice 703 704config ARCH_SUPPORTS_CFI_CLANG 705 bool 706 help 707 An architecture should select this option if it can support Clang's 708 Control-Flow Integrity (CFI) checking. 709 710config CFI_CLANG 711 bool "Use Clang's Control Flow Integrity (CFI)" 712 depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG 713 # Clang >= 12: 714 # - https://bugs.llvm.org/show_bug.cgi?id=46258 715 # - https://bugs.llvm.org/show_bug.cgi?id=47479 716 depends on CLANG_VERSION >= 120000 717 select KALLSYMS 718 help 719 This option enables Clang’s forward-edge Control Flow Integrity 720 (CFI) checking, where the compiler injects a runtime check to each 721 indirect function call to ensure the target is a valid function with 722 the correct static type. This restricts possible call targets and 723 makes it more difficult for an attacker to exploit bugs that allow 724 the modification of stored function pointers. More information can be 725 found from Clang's documentation: 726 727 https://clang.llvm.org/docs/ControlFlowIntegrity.html 728 729config CFI_CLANG_SHADOW 730 bool "Use CFI shadow to speed up cross-module checks" 731 default y 732 depends on CFI_CLANG && MODULES 733 help 734 If you select this option, the kernel builds a fast look-up table of 735 CFI check functions in loaded modules to reduce performance overhead. 736 737 If unsure, say Y. 738 739config CFI_PERMISSIVE 740 bool "Use CFI in permissive mode" 741 depends on CFI_CLANG 742 help 743 When selected, Control Flow Integrity (CFI) violations result in a 744 warning instead of a kernel panic. This option should only be used 745 for finding indirect call type mismatches during development. 746 747 If unsure, say N. 748 749config HAVE_ARCH_WITHIN_STACK_FRAMES 750 bool 751 help 752 An architecture should select this if it can walk the kernel stack 753 frames to determine if an object is part of either the arguments 754 or local variables (i.e. that it excludes saved return addresses, 755 and similar) by implementing an inline arch_within_stack_frames(), 756 which is used by CONFIG_HARDENED_USERCOPY. 757 758config HAVE_CONTEXT_TRACKING 759 bool 760 help 761 Provide kernel/user boundaries probes necessary for subsystems 762 that need it, such as userspace RCU extended quiescent state. 763 Syscalls need to be wrapped inside user_exit()-user_enter(), either 764 optimized behind static key or through the slow path using TIF_NOHZ 765 flag. Exceptions handlers must be wrapped as well. Irqs are already 766 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 767 handling on irq exit still need to be protected. 768 769config HAVE_CONTEXT_TRACKING_OFFSTACK 770 bool 771 help 772 Architecture neither relies on exception_enter()/exception_exit() 773 nor on schedule_user(). Also preempt_schedule_notrace() and 774 preempt_schedule_irq() can't be called in a preemptible section 775 while context tracking is CONTEXT_USER. This feature reflects a sane 776 entry implementation where the following requirements are met on 777 critical entry code, ie: before user_exit() or after user_enter(): 778 779 - Critical entry code isn't preemptible (or better yet: 780 not interruptible). 781 - No use of RCU read side critical sections, unless rcu_nmi_enter() 782 got called. 783 - No use of instrumentation, unless instrumentation_begin() got 784 called. 785 786config HAVE_TIF_NOHZ 787 bool 788 help 789 Arch relies on TIF_NOHZ and syscall slow path to implement context 790 tracking calls to user_enter()/user_exit(). 791 792config HAVE_VIRT_CPU_ACCOUNTING 793 bool 794 795config HAVE_VIRT_CPU_ACCOUNTING_IDLE 796 bool 797 help 798 Architecture has its own way to account idle CPU time and therefore 799 doesn't implement vtime_account_idle(). 800 801config ARCH_HAS_SCALED_CPUTIME 802 bool 803 804config HAVE_VIRT_CPU_ACCOUNTING_GEN 805 bool 806 default y if 64BIT 807 help 808 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 809 Before enabling this option, arch code must be audited 810 to ensure there are no races in concurrent read/write of 811 cputime_t. For example, reading/writing 64-bit cputime_t on 812 some 32-bit arches may require multiple accesses, so proper 813 locking is needed to protect against concurrent accesses. 814 815config HAVE_IRQ_TIME_ACCOUNTING 816 bool 817 help 818 Archs need to ensure they use a high enough resolution clock to 819 support irq time accounting and then call enable_sched_clock_irqtime(). 820 821config HAVE_MOVE_PUD 822 bool 823 help 824 Architectures that select this are able to move page tables at the 825 PUD level. If there are only 3 page table levels, the move effectively 826 happens at the PGD level. 827 828config HAVE_MOVE_PMD 829 bool 830 help 831 Archs that select this are able to move page tables at the PMD level. 832 833config HAVE_ARCH_TRANSPARENT_HUGEPAGE 834 bool 835 836config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 837 bool 838 839config HAVE_ARCH_HUGE_VMAP 840 bool 841 842# 843# Archs that select this would be capable of PMD-sized vmaps (i.e., 844# arch_vmap_pmd_supported() returns true), and they must make no assumptions 845# that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag 846# can be used to prohibit arch-specific allocations from using hugepages to 847# help with this (e.g., modules may require it). 848# 849config HAVE_ARCH_HUGE_VMALLOC 850 depends on HAVE_ARCH_HUGE_VMAP 851 bool 852 853config ARCH_WANT_HUGE_PMD_SHARE 854 bool 855 856config HAVE_ARCH_SOFT_DIRTY 857 bool 858 859config HAVE_MOD_ARCH_SPECIFIC 860 bool 861 help 862 The arch uses struct mod_arch_specific to store data. Many arches 863 just need a simple module loader without arch specific data - those 864 should not enable this. 865 866config MODULES_USE_ELF_RELA 867 bool 868 help 869 Modules only use ELF RELA relocations. Modules with ELF REL 870 relocations will give an error. 871 872config MODULES_USE_ELF_REL 873 bool 874 help 875 Modules only use ELF REL relocations. Modules with ELF RELA 876 relocations will give an error. 877 878config HAVE_IRQ_EXIT_ON_IRQ_STACK 879 bool 880 help 881 Architecture doesn't only execute the irq handler on the irq stack 882 but also irq_exit(). This way we can process softirqs on this irq 883 stack instead of switching to a new one when we call __do_softirq() 884 in the end of an hardirq. 885 This spares a stack switch and improves cache usage on softirq 886 processing. 887 888config HAVE_SOFTIRQ_ON_OWN_STACK 889 bool 890 help 891 Architecture provides a function to run __do_softirq() on a 892 separate stack. 893 894config PGTABLE_LEVELS 895 int 896 default 2 897 898config ARCH_HAS_ELF_RANDOMIZE 899 bool 900 help 901 An architecture supports choosing randomized locations for 902 stack, mmap, brk, and ET_DYN. Defined functions: 903 - arch_mmap_rnd() 904 - arch_randomize_brk() 905 906config HAVE_ARCH_MMAP_RND_BITS 907 bool 908 help 909 An arch should select this symbol if it supports setting a variable 910 number of bits for use in establishing the base address for mmap 911 allocations, has MMU enabled and provides values for both: 912 - ARCH_MMAP_RND_BITS_MIN 913 - ARCH_MMAP_RND_BITS_MAX 914 915config HAVE_EXIT_THREAD 916 bool 917 help 918 An architecture implements exit_thread. 919 920config ARCH_MMAP_RND_BITS_MIN 921 int 922 923config ARCH_MMAP_RND_BITS_MAX 924 int 925 926config ARCH_MMAP_RND_BITS_DEFAULT 927 int 928 929config ARCH_MMAP_RND_BITS 930 int "Number of bits to use for ASLR of mmap base address" if EXPERT 931 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 932 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 933 default ARCH_MMAP_RND_BITS_MIN 934 depends on HAVE_ARCH_MMAP_RND_BITS 935 help 936 This value can be used to select the number of bits to use to 937 determine the random offset to the base address of vma regions 938 resulting from mmap allocations. This value will be bounded 939 by the architecture's minimum and maximum supported values. 940 941 This value can be changed after boot using the 942 /proc/sys/vm/mmap_rnd_bits tunable 943 944config HAVE_ARCH_MMAP_RND_COMPAT_BITS 945 bool 946 help 947 An arch should select this symbol if it supports running applications 948 in compatibility mode, supports setting a variable number of bits for 949 use in establishing the base address for mmap allocations, has MMU 950 enabled and provides values for both: 951 - ARCH_MMAP_RND_COMPAT_BITS_MIN 952 - ARCH_MMAP_RND_COMPAT_BITS_MAX 953 954config ARCH_MMAP_RND_COMPAT_BITS_MIN 955 int 956 957config ARCH_MMAP_RND_COMPAT_BITS_MAX 958 int 959 960config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 961 int 962 963config ARCH_MMAP_RND_COMPAT_BITS 964 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 965 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 966 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 967 default ARCH_MMAP_RND_COMPAT_BITS_MIN 968 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 969 help 970 This value can be used to select the number of bits to use to 971 determine the random offset to the base address of vma regions 972 resulting from mmap allocations for compatible applications This 973 value will be bounded by the architecture's minimum and maximum 974 supported values. 975 976 This value can be changed after boot using the 977 /proc/sys/vm/mmap_rnd_compat_bits tunable 978 979config HAVE_ARCH_COMPAT_MMAP_BASES 980 bool 981 help 982 This allows 64bit applications to invoke 32-bit mmap() syscall 983 and vice-versa 32-bit applications to call 64-bit mmap(). 984 Required for applications doing different bitness syscalls. 985 986# This allows to use a set of generic functions to determine mmap base 987# address by giving priority to top-down scheme only if the process 988# is not in legacy mode (compat task, unlimited stack size or 989# sysctl_legacy_va_layout). 990# Architecture that selects this option can provide its own version of: 991# - STACK_RND_MASK 992config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 993 bool 994 depends on MMU 995 select ARCH_HAS_ELF_RANDOMIZE 996 997config HAVE_STACK_VALIDATION 998 bool 999 help 1000 Architecture supports the 'objtool check' host tool command, which 1001 performs compile-time stack metadata validation. 1002 1003config HAVE_RELIABLE_STACKTRACE 1004 bool 1005 help 1006 Architecture has either save_stack_trace_tsk_reliable() or 1007 arch_stack_walk_reliable() function which only returns a stack trace 1008 if it can guarantee the trace is reliable. 1009 1010config HAVE_ARCH_HASH 1011 bool 1012 default n 1013 help 1014 If this is set, the architecture provides an <asm/hash.h> 1015 file which provides platform-specific implementations of some 1016 functions in <linux/hash.h> or fs/namei.c. 1017 1018config HAVE_ARCH_NVRAM_OPS 1019 bool 1020 1021config ISA_BUS_API 1022 def_bool ISA 1023 1024# 1025# ABI hall of shame 1026# 1027config CLONE_BACKWARDS 1028 bool 1029 help 1030 Architecture has tls passed as the 4th argument of clone(2), 1031 not the 5th one. 1032 1033config CLONE_BACKWARDS2 1034 bool 1035 help 1036 Architecture has the first two arguments of clone(2) swapped. 1037 1038config CLONE_BACKWARDS3 1039 bool 1040 help 1041 Architecture has tls passed as the 3rd argument of clone(2), 1042 not the 5th one. 1043 1044config ODD_RT_SIGACTION 1045 bool 1046 help 1047 Architecture has unusual rt_sigaction(2) arguments 1048 1049config OLD_SIGSUSPEND 1050 bool 1051 help 1052 Architecture has old sigsuspend(2) syscall, of one-argument variety 1053 1054config OLD_SIGSUSPEND3 1055 bool 1056 help 1057 Even weirder antique ABI - three-argument sigsuspend(2) 1058 1059config OLD_SIGACTION 1060 bool 1061 help 1062 Architecture has old sigaction(2) syscall. Nope, not the same 1063 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1064 but fairly different variant of sigaction(2), thanks to OSF/1 1065 compatibility... 1066 1067config COMPAT_OLD_SIGACTION 1068 bool 1069 1070config COMPAT_32BIT_TIME 1071 bool "Provide system calls for 32-bit time_t" 1072 default !64BIT || COMPAT 1073 help 1074 This enables 32 bit time_t support in addition to 64 bit time_t support. 1075 This is relevant on all 32-bit architectures, and 64-bit architectures 1076 as part of compat syscall handling. 1077 1078config ARCH_NO_PREEMPT 1079 bool 1080 1081config ARCH_EPHEMERAL_INODES 1082 def_bool n 1083 help 1084 An arch should select this symbol if it doesn't keep track of inode 1085 instances on its own, but instead relies on something else (e.g. the 1086 host kernel for an UML kernel). 1087 1088config ARCH_SUPPORTS_RT 1089 bool 1090 1091config CPU_NO_EFFICIENT_FFS 1092 def_bool n 1093 1094config HAVE_ARCH_VMAP_STACK 1095 def_bool n 1096 help 1097 An arch should select this symbol if it can support kernel stacks 1098 in vmalloc space. This means: 1099 1100 - vmalloc space must be large enough to hold many kernel stacks. 1101 This may rule out many 32-bit architectures. 1102 1103 - Stacks in vmalloc space need to work reliably. For example, if 1104 vmap page tables are created on demand, either this mechanism 1105 needs to work while the stack points to a virtual address with 1106 unpopulated page tables or arch code (switch_to() and switch_mm(), 1107 most likely) needs to ensure that the stack's page table entries 1108 are populated before running on a possibly unpopulated stack. 1109 1110 - If the stack overflows into a guard page, something reasonable 1111 should happen. The definition of "reasonable" is flexible, but 1112 instantly rebooting without logging anything would be unfriendly. 1113 1114config VMAP_STACK 1115 default y 1116 bool "Use a virtually-mapped stack" 1117 depends on HAVE_ARCH_VMAP_STACK 1118 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1119 help 1120 Enable this if you want the use virtually-mapped kernel stacks 1121 with guard pages. This causes kernel stack overflows to be 1122 caught immediately rather than causing difficult-to-diagnose 1123 corruption. 1124 1125 To use this with software KASAN modes, the architecture must support 1126 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1127 must be enabled. 1128 1129config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1130 def_bool n 1131 help 1132 An arch should select this symbol if it can support kernel stack 1133 offset randomization with calls to add_random_kstack_offset() 1134 during syscall entry and choose_random_kstack_offset() during 1135 syscall exit. Careful removal of -fstack-protector-strong and 1136 -fstack-protector should also be applied to the entry code and 1137 closely examined, as the artificial stack bump looks like an array 1138 to the compiler, so it will attempt to add canary checks regardless 1139 of the static branch state. 1140 1141config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1142 bool "Randomize kernel stack offset on syscall entry" 1143 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1144 help 1145 The kernel stack offset can be randomized (after pt_regs) by 1146 roughly 5 bits of entropy, frustrating memory corruption 1147 attacks that depend on stack address determinism or 1148 cross-syscall address exposures. This feature is controlled 1149 by kernel boot param "randomize_kstack_offset=on/off", and this 1150 config chooses the default boot state. 1151 1152config ARCH_OPTIONAL_KERNEL_RWX 1153 def_bool n 1154 1155config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1156 def_bool n 1157 1158config ARCH_HAS_STRICT_KERNEL_RWX 1159 def_bool n 1160 1161config STRICT_KERNEL_RWX 1162 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1163 depends on ARCH_HAS_STRICT_KERNEL_RWX 1164 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1165 help 1166 If this is set, kernel text and rodata memory will be made read-only, 1167 and non-text memory will be made non-executable. This provides 1168 protection against certain security exploits (e.g. executing the heap 1169 or modifying text) 1170 1171 These features are considered standard security practice these days. 1172 You should say Y here in almost all cases. 1173 1174config ARCH_HAS_STRICT_MODULE_RWX 1175 def_bool n 1176 1177config STRICT_MODULE_RWX 1178 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1179 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1180 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1181 help 1182 If this is set, module text and rodata memory will be made read-only, 1183 and non-text memory will be made non-executable. This provides 1184 protection against certain security exploits (e.g. writing to text) 1185 1186# select if the architecture provides an asm/dma-direct.h header 1187config ARCH_HAS_PHYS_TO_DMA 1188 bool 1189 1190config HAVE_ARCH_COMPILER_H 1191 bool 1192 help 1193 An architecture can select this if it provides an 1194 asm/compiler.h header that should be included after 1195 linux/compiler-*.h in order to override macro definitions that those 1196 headers generally provide. 1197 1198config HAVE_ARCH_PREL32_RELOCATIONS 1199 bool 1200 help 1201 May be selected by an architecture if it supports place-relative 1202 32-bit relocations, both in the toolchain and in the module loader, 1203 in which case relative references can be used in special sections 1204 for PCI fixup, initcalls etc which are only half the size on 64 bit 1205 architectures, and don't require runtime relocation on relocatable 1206 kernels. 1207 1208config ARCH_USE_MEMREMAP_PROT 1209 bool 1210 1211config LOCK_EVENT_COUNTS 1212 bool "Locking event counts collection" 1213 depends on DEBUG_FS 1214 help 1215 Enable light-weight counting of various locking related events 1216 in the system with minimal performance impact. This reduces 1217 the chance of application behavior change because of timing 1218 differences. The counts are reported via debugfs. 1219 1220# Select if the architecture has support for applying RELR relocations. 1221config ARCH_HAS_RELR 1222 bool 1223 1224config RELR 1225 bool "Use RELR relocation packing" 1226 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1227 default y 1228 help 1229 Store the kernel's dynamic relocations in the RELR relocation packing 1230 format. Requires a compatible linker (LLD supports this feature), as 1231 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1232 are compatible). 1233 1234config ARCH_HAS_MEM_ENCRYPT 1235 bool 1236 1237config HAVE_SPARSE_SYSCALL_NR 1238 bool 1239 help 1240 An architecture should select this if its syscall numbering is sparse 1241 to save space. For example, MIPS architecture has a syscall array with 1242 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1243 related optimizations for a given architecture. 1244 1245config ARCH_HAS_VDSO_DATA 1246 bool 1247 1248config HAVE_STATIC_CALL 1249 bool 1250 1251config HAVE_STATIC_CALL_INLINE 1252 bool 1253 depends on HAVE_STATIC_CALL 1254 1255config HAVE_PREEMPT_DYNAMIC 1256 bool 1257 depends on HAVE_STATIC_CALL 1258 depends on GENERIC_ENTRY 1259 help 1260 Select this if the architecture support boot time preempt setting 1261 on top of static calls. It is strongly advised to support inline 1262 static call to avoid any overhead. 1263 1264config ARCH_WANT_LD_ORPHAN_WARN 1265 bool 1266 help 1267 An arch should select this symbol once all linker sections are explicitly 1268 included, size-asserted, or discarded in the linker scripts. This is 1269 important because we never want expected sections to be placed heuristically 1270 by the linker, since the locations of such sections can change between linker 1271 versions. 1272 1273config HAVE_ARCH_PFN_VALID 1274 bool 1275 1276config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1277 bool 1278 1279config ARCH_SPLIT_ARG64 1280 bool 1281 help 1282 If a 32-bit architecture requires 64-bit arguments to be split into 1283 pairs of 32-bit arguments, select this option. 1284 1285config ARCH_HAS_ELFCORE_COMPAT 1286 bool 1287 1288config ARCH_HAS_PARANOID_L1D_FLUSH 1289 bool 1290 1291source "kernel/gcov/Kconfig" 1292 1293source "scripts/gcc-plugins/Kconfig" 1294 1295endmenu 1296