1 # SPDX-License-Identifier: GPL-2.0 2 # 3 # General architecture dependent options 4 # 5 6 # 7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8 # override the default values in this file. 9 # 10 source "arch/$(SRCARCH)/Kconfig" 11 12 menu "General architecture-dependent options" 13 14 config CRASH_CORE 15 bool 16 17 config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21 config KEXEC_ELF 22 bool 23 24 config HAVE_IMA_KEXEC 25 bool 26 27 config SET_FS 28 bool 29 30 config HOTPLUG_SMT 31 bool 32 33 config GENERIC_ENTRY 34 bool 35 36 config 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 48 config 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 74 config 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 80 config 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 86 config OPTPROBES 87 def_bool y 88 depends on KPROBES && HAVE_OPTPROBES 89 select TASKS_RCU if PREEMPTION 90 91 config 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. 99 100 config 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. ) 113 114 config 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. 129 130 config 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. 148 149 config 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. 167 168 config KRETPROBES 169 def_bool y 170 depends on KPROBES && HAVE_KRETPROBES 171 172 config 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. 178 179 config HAVE_IOREMAP_PROT 180 bool 181 182 config HAVE_KPROBES 183 bool 184 185 config HAVE_KRETPROBES 186 bool 187 188 config HAVE_OPTPROBES 189 bool 190 191 config HAVE_KPROBES_ON_FTRACE 192 bool 193 194 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 195 bool 196 help 197 Since kretprobes modifies return address on the stack, the 198 stacktrace may see the kretprobe trampoline address instead 199 of correct one. If the architecture stacktrace code and 200 unwinder can adjust such entries, select this configuration. 201 202 config HAVE_FUNCTION_ERROR_INJECTION 203 bool 204 205 config HAVE_NMI 206 bool 207 208 config TRACE_IRQFLAGS_SUPPORT 209 bool 210 211 # 212 # An arch should select this if it provides all these things: 213 # 214 # task_pt_regs() in asm/processor.h or asm/ptrace.h 215 # arch_has_single_step() if there is hardware single-step support 216 # arch_has_block_step() if there is hardware block-step support 217 # asm/syscall.h supplying asm-generic/syscall.h interface 218 # linux/regset.h user_regset interfaces 219 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h 220 # TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 221 # TIF_NOTIFY_RESUME calls tracehook_notify_resume() 222 # signal delivery calls tracehook_signal_handler() 223 # 224 config HAVE_ARCH_TRACEHOOK 225 bool 226 227 config HAVE_DMA_CONTIGUOUS 228 bool 229 230 config GENERIC_SMP_IDLE_THREAD 231 bool 232 233 config GENERIC_IDLE_POLL_SETUP 234 bool 235 236 config ARCH_HAS_FORTIFY_SOURCE 237 bool 238 help 239 An architecture should select this when it can successfully 240 build and run with CONFIG_FORTIFY_SOURCE. 241 242 # 243 # Select if the arch provides a historic keepinit alias for the retain_initrd 244 # command line option 245 # 246 config ARCH_HAS_KEEPINITRD 247 bool 248 249 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 250 config ARCH_HAS_SET_MEMORY 251 bool 252 253 # Select if arch has all set_direct_map_invalid/default() functions 254 config ARCH_HAS_SET_DIRECT_MAP 255 bool 256 257 # 258 # Select if the architecture provides the arch_dma_set_uncached symbol to 259 # either provide an uncached segment alias for a DMA allocation, or 260 # to remap the page tables in place. 261 # 262 config ARCH_HAS_DMA_SET_UNCACHED 263 bool 264 265 # 266 # Select if the architectures provides the arch_dma_clear_uncached symbol 267 # to undo an in-place page table remap for uncached access. 268 # 269 config ARCH_HAS_DMA_CLEAR_UNCACHED 270 bool 271 272 # Select if arch init_task must go in the __init_task_data section 273 config ARCH_TASK_STRUCT_ON_STACK 274 bool 275 276 # Select if arch has its private alloc_task_struct() function 277 config ARCH_TASK_STRUCT_ALLOCATOR 278 bool 279 280 config HAVE_ARCH_THREAD_STRUCT_WHITELIST 281 bool 282 depends on !ARCH_TASK_STRUCT_ALLOCATOR 283 help 284 An architecture should select this to provide hardened usercopy 285 knowledge about what region of the thread_struct should be 286 whitelisted for copying to userspace. Normally this is only the 287 FPU registers. Specifically, arch_thread_struct_whitelist() 288 should be implemented. Without this, the entire thread_struct 289 field in task_struct will be left whitelisted. 290 291 # Select if arch has its private alloc_thread_stack() function 292 config ARCH_THREAD_STACK_ALLOCATOR 293 bool 294 295 # Select if arch wants to size task_struct dynamically via arch_task_struct_size: 296 config ARCH_WANTS_DYNAMIC_TASK_STRUCT 297 bool 298 299 config ARCH_WANTS_NO_INSTR 300 bool 301 help 302 An architecture should select this if the noinstr macro is being used on 303 functions to denote that the toolchain should avoid instrumenting such 304 functions and is required for correctness. 305 306 config ARCH_32BIT_OFF_T 307 bool 308 depends on !64BIT 309 help 310 All new 32-bit architectures should have 64-bit off_t type on 311 userspace side which corresponds to the loff_t kernel type. This 312 is the requirement for modern ABIs. Some existing architectures 313 still support 32-bit off_t. This option is enabled for all such 314 architectures explicitly. 315 316 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat 317 config ARCH_32BIT_USTAT_F_TINODE 318 bool 319 320 config HAVE_ASM_MODVERSIONS 321 bool 322 help 323 This symbol should be selected by an architecture if it provides 324 <asm/asm-prototypes.h> to support the module versioning for symbols 325 exported from assembly code. 326 327 config HAVE_REGS_AND_STACK_ACCESS_API 328 bool 329 help 330 This symbol should be selected by an architecture if it supports 331 the API needed to access registers and stack entries from pt_regs, 332 declared in asm/ptrace.h 333 For example the kprobes-based event tracer needs this API. 334 335 config HAVE_RSEQ 336 bool 337 depends on HAVE_REGS_AND_STACK_ACCESS_API 338 help 339 This symbol should be selected by an architecture if it 340 supports an implementation of restartable sequences. 341 342 config HAVE_FUNCTION_ARG_ACCESS_API 343 bool 344 help 345 This symbol should be selected by an architecture if it supports 346 the API needed to access function arguments from pt_regs, 347 declared in asm/ptrace.h 348 349 config HAVE_HW_BREAKPOINT 350 bool 351 depends on PERF_EVENTS 352 353 config HAVE_MIXED_BREAKPOINTS_REGS 354 bool 355 depends on HAVE_HW_BREAKPOINT 356 help 357 Depending on the arch implementation of hardware breakpoints, 358 some of them have separate registers for data and instruction 359 breakpoints addresses, others have mixed registers to store 360 them but define the access type in a control register. 361 Select this option if your arch implements breakpoints under the 362 latter fashion. 363 364 config HAVE_USER_RETURN_NOTIFIER 365 bool 366 367 config HAVE_PERF_EVENTS_NMI 368 bool 369 help 370 System hardware can generate an NMI using the perf event 371 subsystem. Also has support for calculating CPU cycle events 372 to determine how many clock cycles in a given period. 373 374 config HAVE_HARDLOCKUP_DETECTOR_PERF 375 bool 376 depends on HAVE_PERF_EVENTS_NMI 377 help 378 The arch chooses to use the generic perf-NMI-based hardlockup 379 detector. Must define HAVE_PERF_EVENTS_NMI. 380 381 config HAVE_NMI_WATCHDOG 382 depends on HAVE_NMI 383 bool 384 help 385 The arch provides a low level NMI watchdog. It provides 386 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 387 388 config HAVE_HARDLOCKUP_DETECTOR_ARCH 389 bool 390 select HAVE_NMI_WATCHDOG 391 help 392 The arch chooses to provide its own hardlockup detector, which is 393 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 394 interfaces and parameters provided by hardlockup detector subsystem. 395 396 config HAVE_PERF_REGS 397 bool 398 help 399 Support selective register dumps for perf events. This includes 400 bit-mapping of each registers and a unique architecture id. 401 402 config HAVE_PERF_USER_STACK_DUMP 403 bool 404 help 405 Support user stack dumps for perf event samples. This needs 406 access to the user stack pointer which is not unified across 407 architectures. 408 409 config HAVE_ARCH_JUMP_LABEL 410 bool 411 412 config HAVE_ARCH_JUMP_LABEL_RELATIVE 413 bool 414 415 config MMU_GATHER_TABLE_FREE 416 bool 417 418 config MMU_GATHER_RCU_TABLE_FREE 419 bool 420 select MMU_GATHER_TABLE_FREE 421 422 config MMU_GATHER_PAGE_SIZE 423 bool 424 425 config MMU_GATHER_NO_RANGE 426 bool 427 428 config MMU_GATHER_NO_GATHER 429 bool 430 depends on MMU_GATHER_TABLE_FREE 431 432 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 433 bool 434 help 435 Temporary select until all architectures can be converted to have 436 irqs disabled over activate_mm. Architectures that do IPI based TLB 437 shootdowns should enable this. 438 439 config ARCH_HAVE_NMI_SAFE_CMPXCHG 440 bool 441 442 config HAVE_ALIGNED_STRUCT_PAGE 443 bool 444 help 445 This makes sure that struct pages are double word aligned and that 446 e.g. the SLUB allocator can perform double word atomic operations 447 on a struct page for better performance. However selecting this 448 might increase the size of a struct page by a word. 449 450 config HAVE_CMPXCHG_LOCAL 451 bool 452 453 config HAVE_CMPXCHG_DOUBLE 454 bool 455 456 config ARCH_WEAK_RELEASE_ACQUIRE 457 bool 458 459 config ARCH_WANT_IPC_PARSE_VERSION 460 bool 461 462 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 463 bool 464 465 config ARCH_WANT_OLD_COMPAT_IPC 466 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 467 bool 468 469 config HAVE_ARCH_SECCOMP 470 bool 471 help 472 An arch should select this symbol to support seccomp mode 1 (the fixed 473 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 474 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 475 - __NR_seccomp_read_32 476 - __NR_seccomp_write_32 477 - __NR_seccomp_exit_32 478 - __NR_seccomp_sigreturn_32 479 480 config HAVE_ARCH_SECCOMP_FILTER 481 bool 482 select HAVE_ARCH_SECCOMP 483 help 484 An arch should select this symbol if it provides all of these things: 485 - all the requirements for HAVE_ARCH_SECCOMP 486 - syscall_get_arch() 487 - syscall_get_arguments() 488 - syscall_rollback() 489 - syscall_set_return_value() 490 - SIGSYS siginfo_t support 491 - secure_computing is called from a ptrace_event()-safe context 492 - secure_computing return value is checked and a return value of -1 493 results in the system call being skipped immediately. 494 - seccomp syscall wired up 495 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE, 496 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If 497 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too. 498 499 config SECCOMP 500 prompt "Enable seccomp to safely execute untrusted bytecode" 501 def_bool y 502 depends on HAVE_ARCH_SECCOMP 503 help 504 This kernel feature is useful for number crunching applications 505 that may need to handle untrusted bytecode during their 506 execution. By using pipes or other transports made available 507 to the process as file descriptors supporting the read/write 508 syscalls, it's possible to isolate those applications in their 509 own address space using seccomp. Once seccomp is enabled via 510 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 511 disabled and the task is only allowed to execute a few safe 512 syscalls defined by each seccomp mode. 513 514 If unsure, say Y. 515 516 config SECCOMP_FILTER 517 def_bool y 518 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 519 help 520 Enable tasks to build secure computing environments defined 521 in terms of Berkeley Packet Filter programs which implement 522 task-defined system call filtering polices. 523 524 See Documentation/userspace-api/seccomp_filter.rst for details. 525 526 config SECCOMP_CACHE_DEBUG 527 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache" 528 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR 529 depends on PROC_FS 530 help 531 This enables the /proc/pid/seccomp_cache interface to monitor 532 seccomp cache data. The file format is subject to change. Reading 533 the file requires CAP_SYS_ADMIN. 534 535 This option is for debugging only. Enabling presents the risk that 536 an adversary may be able to infer the seccomp filter logic. 537 538 If unsure, say N. 539 540 config HAVE_ARCH_STACKLEAK 541 bool 542 help 543 An architecture should select this if it has the code which 544 fills the used part of the kernel stack with the STACKLEAK_POISON 545 value before returning from system calls. 546 547 config HAVE_STACKPROTECTOR 548 bool 549 help 550 An arch should select this symbol if: 551 - it has implemented a stack canary (e.g. __stack_chk_guard) 552 553 config STACKPROTECTOR 554 bool "Stack Protector buffer overflow detection" 555 depends on HAVE_STACKPROTECTOR 556 depends on $(cc-option,-fstack-protector) 557 default y 558 help 559 This option turns on the "stack-protector" GCC feature. This 560 feature puts, at the beginning of functions, a canary value on 561 the stack just before the return address, and validates 562 the value just before actually returning. Stack based buffer 563 overflows (that need to overwrite this return address) now also 564 overwrite the canary, which gets detected and the attack is then 565 neutralized via a kernel panic. 566 567 Functions will have the stack-protector canary logic added if they 568 have an 8-byte or larger character array on the stack. 569 570 This feature requires gcc version 4.2 or above, or a distribution 571 gcc with the feature backported ("-fstack-protector"). 572 573 On an x86 "defconfig" build, this feature adds canary checks to 574 about 3% of all kernel functions, which increases kernel code size 575 by about 0.3%. 576 577 config STACKPROTECTOR_STRONG 578 bool "Strong Stack Protector" 579 depends on STACKPROTECTOR 580 depends on $(cc-option,-fstack-protector-strong) 581 default y 582 help 583 Functions will have the stack-protector canary logic added in any 584 of the following conditions: 585 586 - local variable's address used as part of the right hand side of an 587 assignment or function argument 588 - local variable is an array (or union containing an array), 589 regardless of array type or length 590 - uses register local variables 591 592 This feature requires gcc version 4.9 or above, or a distribution 593 gcc with the feature backported ("-fstack-protector-strong"). 594 595 On an x86 "defconfig" build, this feature adds canary checks to 596 about 20% of all kernel functions, which increases the kernel code 597 size by about 2%. 598 599 config ARCH_SUPPORTS_SHADOW_CALL_STACK 600 bool 601 help 602 An architecture should select this if it supports Clang's Shadow 603 Call Stack and implements runtime support for shadow stack 604 switching. 605 606 config SHADOW_CALL_STACK 607 bool "Clang Shadow Call Stack" 608 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 609 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 610 help 611 This option enables Clang's Shadow Call Stack, which uses a 612 shadow stack to protect function return addresses from being 613 overwritten by an attacker. More information can be found in 614 Clang's documentation: 615 616 https://clang.llvm.org/docs/ShadowCallStack.html 617 618 Note that security guarantees in the kernel differ from the 619 ones documented for user space. The kernel must store addresses 620 of shadow stacks in memory, which means an attacker capable of 621 reading and writing arbitrary memory may be able to locate them 622 and hijack control flow by modifying the stacks. 623 624 config LTO 625 bool 626 help 627 Selected if the kernel will be built using the compiler's LTO feature. 628 629 config LTO_CLANG 630 bool 631 select LTO 632 help 633 Selected if the kernel will be built using Clang's LTO feature. 634 635 config ARCH_SUPPORTS_LTO_CLANG 636 bool 637 help 638 An architecture should select this option if it supports: 639 - compiling with Clang, 640 - compiling inline assembly with Clang's integrated assembler, 641 - and linking with LLD. 642 643 config ARCH_SUPPORTS_LTO_CLANG_THIN 644 bool 645 help 646 An architecture should select this option if it can support Clang's 647 ThinLTO mode. 648 649 config HAS_LTO_CLANG 650 def_bool y 651 # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510 652 depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM 653 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 654 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 655 depends on ARCH_SUPPORTS_LTO_CLANG 656 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 657 depends on !KASAN || KASAN_HW_TAGS 658 depends on !GCOV_KERNEL 659 help 660 The compiler and Kconfig options support building with Clang's 661 LTO. 662 663 choice 664 prompt "Link Time Optimization (LTO)" 665 default LTO_NONE 666 help 667 This option enables Link Time Optimization (LTO), which allows the 668 compiler to optimize binaries globally. 669 670 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 671 so it's disabled by default. 672 673 config LTO_NONE 674 bool "None" 675 help 676 Build the kernel normally, without Link Time Optimization (LTO). 677 678 config LTO_CLANG_FULL 679 bool "Clang Full LTO (EXPERIMENTAL)" 680 depends on HAS_LTO_CLANG 681 depends on !COMPILE_TEST 682 select LTO_CLANG 683 help 684 This option enables Clang's full Link Time Optimization (LTO), which 685 allows the compiler to optimize the kernel globally. If you enable 686 this option, the compiler generates LLVM bitcode instead of ELF 687 object files, and the actual compilation from bitcode happens at 688 the LTO link step, which may take several minutes depending on the 689 kernel configuration. More information can be found from LLVM's 690 documentation: 691 692 https://llvm.org/docs/LinkTimeOptimization.html 693 694 During link time, this option can use a large amount of RAM, and 695 may take much longer than the ThinLTO option. 696 697 config LTO_CLANG_THIN 698 bool "Clang ThinLTO (EXPERIMENTAL)" 699 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 700 select LTO_CLANG 701 help 702 This option enables Clang's ThinLTO, which allows for parallel 703 optimization and faster incremental compiles compared to the 704 CONFIG_LTO_CLANG_FULL option. More information can be found 705 from Clang's documentation: 706 707 https://clang.llvm.org/docs/ThinLTO.html 708 709 If unsure, say Y. 710 endchoice 711 712 config ARCH_SUPPORTS_CFI_CLANG 713 bool 714 help 715 An architecture should select this option if it can support Clang's 716 Control-Flow Integrity (CFI) checking. 717 718 config CFI_CLANG 719 bool "Use Clang's Control Flow Integrity (CFI)" 720 depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG 721 # Clang >= 12: 722 # - https://bugs.llvm.org/show_bug.cgi?id=46258 723 # - https://bugs.llvm.org/show_bug.cgi?id=47479 724 depends on CLANG_VERSION >= 120000 725 select KALLSYMS 726 help 727 This option enables Clang’s forward-edge Control Flow Integrity 728 (CFI) checking, where the compiler injects a runtime check to each 729 indirect function call to ensure the target is a valid function with 730 the correct static type. This restricts possible call targets and 731 makes it more difficult for an attacker to exploit bugs that allow 732 the modification of stored function pointers. More information can be 733 found from Clang's documentation: 734 735 https://clang.llvm.org/docs/ControlFlowIntegrity.html 736 737 config CFI_CLANG_SHADOW 738 bool "Use CFI shadow to speed up cross-module checks" 739 default y 740 depends on CFI_CLANG && MODULES 741 help 742 If you select this option, the kernel builds a fast look-up table of 743 CFI check functions in loaded modules to reduce performance overhead. 744 745 If unsure, say Y. 746 747 config CFI_PERMISSIVE 748 bool "Use CFI in permissive mode" 749 depends on CFI_CLANG 750 help 751 When selected, Control Flow Integrity (CFI) violations result in a 752 warning instead of a kernel panic. This option should only be used 753 for finding indirect call type mismatches during development. 754 755 If unsure, say N. 756 757 config HAVE_ARCH_WITHIN_STACK_FRAMES 758 bool 759 help 760 An architecture should select this if it can walk the kernel stack 761 frames to determine if an object is part of either the arguments 762 or local variables (i.e. that it excludes saved return addresses, 763 and similar) by implementing an inline arch_within_stack_frames(), 764 which is used by CONFIG_HARDENED_USERCOPY. 765 766 config HAVE_CONTEXT_TRACKING 767 bool 768 help 769 Provide kernel/user boundaries probes necessary for subsystems 770 that need it, such as userspace RCU extended quiescent state. 771 Syscalls need to be wrapped inside user_exit()-user_enter(), either 772 optimized behind static key or through the slow path using TIF_NOHZ 773 flag. Exceptions handlers must be wrapped as well. Irqs are already 774 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 775 handling on irq exit still need to be protected. 776 777 config HAVE_CONTEXT_TRACKING_OFFSTACK 778 bool 779 help 780 Architecture neither relies on exception_enter()/exception_exit() 781 nor on schedule_user(). Also preempt_schedule_notrace() and 782 preempt_schedule_irq() can't be called in a preemptible section 783 while context tracking is CONTEXT_USER. This feature reflects a sane 784 entry implementation where the following requirements are met on 785 critical entry code, ie: before user_exit() or after user_enter(): 786 787 - Critical entry code isn't preemptible (or better yet: 788 not interruptible). 789 - No use of RCU read side critical sections, unless rcu_nmi_enter() 790 got called. 791 - No use of instrumentation, unless instrumentation_begin() got 792 called. 793 794 config HAVE_TIF_NOHZ 795 bool 796 help 797 Arch relies on TIF_NOHZ and syscall slow path to implement context 798 tracking calls to user_enter()/user_exit(). 799 800 config HAVE_VIRT_CPU_ACCOUNTING 801 bool 802 803 config HAVE_VIRT_CPU_ACCOUNTING_IDLE 804 bool 805 help 806 Architecture has its own way to account idle CPU time and therefore 807 doesn't implement vtime_account_idle(). 808 809 config ARCH_HAS_SCALED_CPUTIME 810 bool 811 812 config HAVE_VIRT_CPU_ACCOUNTING_GEN 813 bool 814 default y if 64BIT 815 help 816 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 817 Before enabling this option, arch code must be audited 818 to ensure there are no races in concurrent read/write of 819 cputime_t. For example, reading/writing 64-bit cputime_t on 820 some 32-bit arches may require multiple accesses, so proper 821 locking is needed to protect against concurrent accesses. 822 823 config HAVE_IRQ_TIME_ACCOUNTING 824 bool 825 help 826 Archs need to ensure they use a high enough resolution clock to 827 support irq time accounting and then call enable_sched_clock_irqtime(). 828 829 config HAVE_MOVE_PUD 830 bool 831 help 832 Architectures that select this are able to move page tables at the 833 PUD level. If there are only 3 page table levels, the move effectively 834 happens at the PGD level. 835 836 config HAVE_MOVE_PMD 837 bool 838 help 839 Archs that select this are able to move page tables at the PMD level. 840 841 config HAVE_ARCH_TRANSPARENT_HUGEPAGE 842 bool 843 844 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 845 bool 846 847 config HAVE_ARCH_HUGE_VMAP 848 bool 849 850 # 851 # Archs that select this would be capable of PMD-sized vmaps (i.e., 852 # arch_vmap_pmd_supported() returns true), and they must make no assumptions 853 # that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag 854 # can be used to prohibit arch-specific allocations from using hugepages to 855 # help with this (e.g., modules may require it). 856 # 857 config HAVE_ARCH_HUGE_VMALLOC 858 depends on HAVE_ARCH_HUGE_VMAP 859 bool 860 861 config ARCH_WANT_HUGE_PMD_SHARE 862 bool 863 864 config HAVE_ARCH_SOFT_DIRTY 865 bool 866 867 config HAVE_MOD_ARCH_SPECIFIC 868 bool 869 help 870 The arch uses struct mod_arch_specific to store data. Many arches 871 just need a simple module loader without arch specific data - those 872 should not enable this. 873 874 config MODULES_USE_ELF_RELA 875 bool 876 help 877 Modules only use ELF RELA relocations. Modules with ELF REL 878 relocations will give an error. 879 880 config MODULES_USE_ELF_REL 881 bool 882 help 883 Modules only use ELF REL relocations. Modules with ELF RELA 884 relocations will give an error. 885 886 config HAVE_IRQ_EXIT_ON_IRQ_STACK 887 bool 888 help 889 Architecture doesn't only execute the irq handler on the irq stack 890 but also irq_exit(). This way we can process softirqs on this irq 891 stack instead of switching to a new one when we call __do_softirq() 892 in the end of an hardirq. 893 This spares a stack switch and improves cache usage on softirq 894 processing. 895 896 config HAVE_SOFTIRQ_ON_OWN_STACK 897 bool 898 help 899 Architecture provides a function to run __do_softirq() on a 900 separate stack. 901 902 config PGTABLE_LEVELS 903 int 904 default 2 905 906 config ARCH_HAS_ELF_RANDOMIZE 907 bool 908 help 909 An architecture supports choosing randomized locations for 910 stack, mmap, brk, and ET_DYN. Defined functions: 911 - arch_mmap_rnd() 912 - arch_randomize_brk() 913 914 config HAVE_ARCH_MMAP_RND_BITS 915 bool 916 help 917 An arch should select this symbol if it supports setting a variable 918 number of bits for use in establishing the base address for mmap 919 allocations, has MMU enabled and provides values for both: 920 - ARCH_MMAP_RND_BITS_MIN 921 - ARCH_MMAP_RND_BITS_MAX 922 923 config HAVE_EXIT_THREAD 924 bool 925 help 926 An architecture implements exit_thread. 927 928 config ARCH_MMAP_RND_BITS_MIN 929 int 930 931 config ARCH_MMAP_RND_BITS_MAX 932 int 933 934 config ARCH_MMAP_RND_BITS_DEFAULT 935 int 936 937 config ARCH_MMAP_RND_BITS 938 int "Number of bits to use for ASLR of mmap base address" if EXPERT 939 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 940 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 941 default ARCH_MMAP_RND_BITS_MIN 942 depends on HAVE_ARCH_MMAP_RND_BITS 943 help 944 This value can be used to select the number of bits to use to 945 determine the random offset to the base address of vma regions 946 resulting from mmap allocations. This value will be bounded 947 by the architecture's minimum and maximum supported values. 948 949 This value can be changed after boot using the 950 /proc/sys/vm/mmap_rnd_bits tunable 951 952 config HAVE_ARCH_MMAP_RND_COMPAT_BITS 953 bool 954 help 955 An arch should select this symbol if it supports running applications 956 in compatibility mode, supports setting a variable number of bits for 957 use in establishing the base address for mmap allocations, has MMU 958 enabled and provides values for both: 959 - ARCH_MMAP_RND_COMPAT_BITS_MIN 960 - ARCH_MMAP_RND_COMPAT_BITS_MAX 961 962 config ARCH_MMAP_RND_COMPAT_BITS_MIN 963 int 964 965 config ARCH_MMAP_RND_COMPAT_BITS_MAX 966 int 967 968 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 969 int 970 971 config ARCH_MMAP_RND_COMPAT_BITS 972 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 973 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 974 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 975 default ARCH_MMAP_RND_COMPAT_BITS_MIN 976 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 977 help 978 This value can be used to select the number of bits to use to 979 determine the random offset to the base address of vma regions 980 resulting from mmap allocations for compatible applications This 981 value will be bounded by the architecture's minimum and maximum 982 supported values. 983 984 This value can be changed after boot using the 985 /proc/sys/vm/mmap_rnd_compat_bits tunable 986 987 config HAVE_ARCH_COMPAT_MMAP_BASES 988 bool 989 help 990 This allows 64bit applications to invoke 32-bit mmap() syscall 991 and vice-versa 32-bit applications to call 64-bit mmap(). 992 Required for applications doing different bitness syscalls. 993 994 config PAGE_SIZE_LESS_THAN_64KB 995 def_bool y 996 depends on !ARM64_64K_PAGES 997 depends on !IA64_PAGE_SIZE_64KB 998 depends on !PAGE_SIZE_64KB 999 depends on !PARISC_PAGE_SIZE_64KB 1000 depends on !PPC_64K_PAGES 1001 depends on !PPC_256K_PAGES 1002 depends on !PAGE_SIZE_256KB 1003 1004 # This allows to use a set of generic functions to determine mmap base 1005 # address by giving priority to top-down scheme only if the process 1006 # is not in legacy mode (compat task, unlimited stack size or 1007 # sysctl_legacy_va_layout). 1008 # Architecture that selects this option can provide its own version of: 1009 # - STACK_RND_MASK 1010 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1011 bool 1012 depends on MMU 1013 select ARCH_HAS_ELF_RANDOMIZE 1014 1015 config HAVE_STACK_VALIDATION 1016 bool 1017 help 1018 Architecture supports the 'objtool check' host tool command, which 1019 performs compile-time stack metadata validation. 1020 1021 config HAVE_RELIABLE_STACKTRACE 1022 bool 1023 help 1024 Architecture has either save_stack_trace_tsk_reliable() or 1025 arch_stack_walk_reliable() function which only returns a stack trace 1026 if it can guarantee the trace is reliable. 1027 1028 config HAVE_ARCH_HASH 1029 bool 1030 default n 1031 help 1032 If this is set, the architecture provides an <asm/hash.h> 1033 file which provides platform-specific implementations of some 1034 functions in <linux/hash.h> or fs/namei.c. 1035 1036 config HAVE_ARCH_NVRAM_OPS 1037 bool 1038 1039 config ISA_BUS_API 1040 def_bool ISA 1041 1042 # 1043 # ABI hall of shame 1044 # 1045 config CLONE_BACKWARDS 1046 bool 1047 help 1048 Architecture has tls passed as the 4th argument of clone(2), 1049 not the 5th one. 1050 1051 config CLONE_BACKWARDS2 1052 bool 1053 help 1054 Architecture has the first two arguments of clone(2) swapped. 1055 1056 config CLONE_BACKWARDS3 1057 bool 1058 help 1059 Architecture has tls passed as the 3rd argument of clone(2), 1060 not the 5th one. 1061 1062 config ODD_RT_SIGACTION 1063 bool 1064 help 1065 Architecture has unusual rt_sigaction(2) arguments 1066 1067 config OLD_SIGSUSPEND 1068 bool 1069 help 1070 Architecture has old sigsuspend(2) syscall, of one-argument variety 1071 1072 config OLD_SIGSUSPEND3 1073 bool 1074 help 1075 Even weirder antique ABI - three-argument sigsuspend(2) 1076 1077 config OLD_SIGACTION 1078 bool 1079 help 1080 Architecture has old sigaction(2) syscall. Nope, not the same 1081 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1082 but fairly different variant of sigaction(2), thanks to OSF/1 1083 compatibility... 1084 1085 config COMPAT_OLD_SIGACTION 1086 bool 1087 1088 config COMPAT_32BIT_TIME 1089 bool "Provide system calls for 32-bit time_t" 1090 default !64BIT || COMPAT 1091 help 1092 This enables 32 bit time_t support in addition to 64 bit time_t support. 1093 This is relevant on all 32-bit architectures, and 64-bit architectures 1094 as part of compat syscall handling. 1095 1096 config ARCH_NO_PREEMPT 1097 bool 1098 1099 config ARCH_EPHEMERAL_INODES 1100 def_bool n 1101 help 1102 An arch should select this symbol if it doesn't keep track of inode 1103 instances on its own, but instead relies on something else (e.g. the 1104 host kernel for an UML kernel). 1105 1106 config ARCH_SUPPORTS_RT 1107 bool 1108 1109 config CPU_NO_EFFICIENT_FFS 1110 def_bool n 1111 1112 config HAVE_ARCH_VMAP_STACK 1113 def_bool n 1114 help 1115 An arch should select this symbol if it can support kernel stacks 1116 in vmalloc space. This means: 1117 1118 - vmalloc space must be large enough to hold many kernel stacks. 1119 This may rule out many 32-bit architectures. 1120 1121 - Stacks in vmalloc space need to work reliably. For example, if 1122 vmap page tables are created on demand, either this mechanism 1123 needs to work while the stack points to a virtual address with 1124 unpopulated page tables or arch code (switch_to() and switch_mm(), 1125 most likely) needs to ensure that the stack's page table entries 1126 are populated before running on a possibly unpopulated stack. 1127 1128 - If the stack overflows into a guard page, something reasonable 1129 should happen. The definition of "reasonable" is flexible, but 1130 instantly rebooting without logging anything would be unfriendly. 1131 1132 config VMAP_STACK 1133 default y 1134 bool "Use a virtually-mapped stack" 1135 depends on HAVE_ARCH_VMAP_STACK 1136 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC 1137 help 1138 Enable this if you want the use virtually-mapped kernel stacks 1139 with guard pages. This causes kernel stack overflows to be 1140 caught immediately rather than causing difficult-to-diagnose 1141 corruption. 1142 1143 To use this with software KASAN modes, the architecture must support 1144 backing virtual mappings with real shadow memory, and KASAN_VMALLOC 1145 must be enabled. 1146 1147 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1148 def_bool n 1149 help 1150 An arch should select this symbol if it can support kernel stack 1151 offset randomization with calls to add_random_kstack_offset() 1152 during syscall entry and choose_random_kstack_offset() during 1153 syscall exit. Careful removal of -fstack-protector-strong and 1154 -fstack-protector should also be applied to the entry code and 1155 closely examined, as the artificial stack bump looks like an array 1156 to the compiler, so it will attempt to add canary checks regardless 1157 of the static branch state. 1158 1159 config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1160 bool "Randomize kernel stack offset on syscall entry" 1161 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1162 help 1163 The kernel stack offset can be randomized (after pt_regs) by 1164 roughly 5 bits of entropy, frustrating memory corruption 1165 attacks that depend on stack address determinism or 1166 cross-syscall address exposures. This feature is controlled 1167 by kernel boot param "randomize_kstack_offset=on/off", and this 1168 config chooses the default boot state. 1169 1170 config ARCH_OPTIONAL_KERNEL_RWX 1171 def_bool n 1172 1173 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1174 def_bool n 1175 1176 config ARCH_HAS_STRICT_KERNEL_RWX 1177 def_bool n 1178 1179 config STRICT_KERNEL_RWX 1180 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1181 depends on ARCH_HAS_STRICT_KERNEL_RWX 1182 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1183 help 1184 If this is set, kernel text and rodata memory will be made read-only, 1185 and non-text memory will be made non-executable. This provides 1186 protection against certain security exploits (e.g. executing the heap 1187 or modifying text) 1188 1189 These features are considered standard security practice these days. 1190 You should say Y here in almost all cases. 1191 1192 config ARCH_HAS_STRICT_MODULE_RWX 1193 def_bool n 1194 1195 config STRICT_MODULE_RWX 1196 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1197 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1198 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1199 help 1200 If this is set, module text and rodata memory will be made read-only, 1201 and non-text memory will be made non-executable. This provides 1202 protection against certain security exploits (e.g. writing to text) 1203 1204 # select if the architecture provides an asm/dma-direct.h header 1205 config ARCH_HAS_PHYS_TO_DMA 1206 bool 1207 1208 config HAVE_ARCH_COMPILER_H 1209 bool 1210 help 1211 An architecture can select this if it provides an 1212 asm/compiler.h header that should be included after 1213 linux/compiler-*.h in order to override macro definitions that those 1214 headers generally provide. 1215 1216 config HAVE_ARCH_PREL32_RELOCATIONS 1217 bool 1218 help 1219 May be selected by an architecture if it supports place-relative 1220 32-bit relocations, both in the toolchain and in the module loader, 1221 in which case relative references can be used in special sections 1222 for PCI fixup, initcalls etc which are only half the size on 64 bit 1223 architectures, and don't require runtime relocation on relocatable 1224 kernels. 1225 1226 config ARCH_USE_MEMREMAP_PROT 1227 bool 1228 1229 config LOCK_EVENT_COUNTS 1230 bool "Locking event counts collection" 1231 depends on DEBUG_FS 1232 help 1233 Enable light-weight counting of various locking related events 1234 in the system with minimal performance impact. This reduces 1235 the chance of application behavior change because of timing 1236 differences. The counts are reported via debugfs. 1237 1238 # Select if the architecture has support for applying RELR relocations. 1239 config ARCH_HAS_RELR 1240 bool 1241 1242 config RELR 1243 bool "Use RELR relocation packing" 1244 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1245 default y 1246 help 1247 Store the kernel's dynamic relocations in the RELR relocation packing 1248 format. Requires a compatible linker (LLD supports this feature), as 1249 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1250 are compatible). 1251 1252 config ARCH_HAS_MEM_ENCRYPT 1253 bool 1254 1255 config ARCH_HAS_CC_PLATFORM 1256 bool 1257 1258 config HAVE_SPARSE_SYSCALL_NR 1259 bool 1260 help 1261 An architecture should select this if its syscall numbering is sparse 1262 to save space. For example, MIPS architecture has a syscall array with 1263 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1264 related optimizations for a given architecture. 1265 1266 config ARCH_HAS_VDSO_DATA 1267 bool 1268 1269 config HAVE_STATIC_CALL 1270 bool 1271 1272 config HAVE_STATIC_CALL_INLINE 1273 bool 1274 depends on HAVE_STATIC_CALL 1275 1276 config HAVE_PREEMPT_DYNAMIC 1277 bool 1278 depends on HAVE_STATIC_CALL 1279 depends on GENERIC_ENTRY 1280 help 1281 Select this if the architecture support boot time preempt setting 1282 on top of static calls. It is strongly advised to support inline 1283 static call to avoid any overhead. 1284 1285 config ARCH_WANT_LD_ORPHAN_WARN 1286 bool 1287 help 1288 An arch should select this symbol once all linker sections are explicitly 1289 included, size-asserted, or discarded in the linker scripts. This is 1290 important because we never want expected sections to be placed heuristically 1291 by the linker, since the locations of such sections can change between linker 1292 versions. 1293 1294 config HAVE_ARCH_PFN_VALID 1295 bool 1296 1297 config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1298 bool 1299 1300 config ARCH_SPLIT_ARG64 1301 bool 1302 help 1303 If a 32-bit architecture requires 64-bit arguments to be split into 1304 pairs of 32-bit arguments, select this option. 1305 1306 config ARCH_HAS_ELFCORE_COMPAT 1307 bool 1308 1309 config ARCH_HAS_PARANOID_L1D_FLUSH 1310 bool 1311 1312 config DYNAMIC_SIGFRAME 1313 bool 1314 1315 source "kernel/gcov/Kconfig" 1316 1317 source "scripts/gcc-plugins/Kconfig" 1318 1319 endmenu 1320