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 OPROFILE 37 tristate "OProfile system profiling" 38 depends on PROFILING 39 depends on HAVE_OPROFILE 40 select RING_BUFFER 41 select RING_BUFFER_ALLOW_SWAP 42 help 43 OProfile is a profiling system capable of profiling the 44 whole system, include the kernel, kernel modules, libraries, 45 and applications. 46 47 If unsure, say N. 48 49config OPROFILE_EVENT_MULTIPLEX 50 bool "OProfile multiplexing support (EXPERIMENTAL)" 51 default n 52 depends on OPROFILE && X86 53 help 54 The number of hardware counters is limited. The multiplexing 55 feature enables OProfile to gather more events than counters 56 are provided by the hardware. This is realized by switching 57 between events at a user specified time interval. 58 59 If unsure, say N. 60 61config HAVE_OPROFILE 62 bool 63 64config OPROFILE_NMI_TIMER 65 def_bool y 66 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 67 68config KPROBES 69 bool "Kprobes" 70 depends on MODULES 71 depends on HAVE_KPROBES 72 select KALLSYMS 73 help 74 Kprobes allows you to trap at almost any kernel address and 75 execute a callback function. register_kprobe() establishes 76 a probepoint and specifies the callback. Kprobes is useful 77 for kernel debugging, non-intrusive instrumentation and testing. 78 If in doubt, say "N". 79 80config JUMP_LABEL 81 bool "Optimize very unlikely/likely branches" 82 depends on HAVE_ARCH_JUMP_LABEL 83 depends on CC_HAS_ASM_GOTO 84 help 85 This option enables a transparent branch optimization that 86 makes certain almost-always-true or almost-always-false branch 87 conditions even cheaper to execute within the kernel. 88 89 Certain performance-sensitive kernel code, such as trace points, 90 scheduler functionality, networking code and KVM have such 91 branches and include support for this optimization technique. 92 93 If it is detected that the compiler has support for "asm goto", 94 the kernel will compile such branches with just a nop 95 instruction. When the condition flag is toggled to true, the 96 nop will be converted to a jump instruction to execute the 97 conditional block of instructions. 98 99 This technique lowers overhead and stress on the branch prediction 100 of the processor and generally makes the kernel faster. The update 101 of the condition is slower, but those are always very rare. 102 103 ( On 32-bit x86, the necessary options added to the compiler 104 flags may increase the size of the kernel slightly. ) 105 106config STATIC_KEYS_SELFTEST 107 bool "Static key selftest" 108 depends on JUMP_LABEL 109 help 110 Boot time self-test of the branch patching code. 111 112config STATIC_CALL_SELFTEST 113 bool "Static call selftest" 114 depends on HAVE_STATIC_CALL 115 help 116 Boot time self-test of the call patching code. 117 118config OPTPROBES 119 def_bool y 120 depends on KPROBES && HAVE_OPTPROBES 121 select TASKS_RCU if PREEMPTION 122 123config KPROBES_ON_FTRACE 124 def_bool y 125 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 126 depends on DYNAMIC_FTRACE_WITH_REGS 127 help 128 If function tracer is enabled and the arch supports full 129 passing of pt_regs to function tracing, then kprobes can 130 optimize on top of function tracing. 131 132config UPROBES 133 def_bool n 134 depends on ARCH_SUPPORTS_UPROBES 135 help 136 Uprobes is the user-space counterpart to kprobes: they 137 enable instrumentation applications (such as 'perf probe') 138 to establish unintrusive probes in user-space binaries and 139 libraries, by executing handler functions when the probes 140 are hit by user-space applications. 141 142 ( These probes come in the form of single-byte breakpoints, 143 managed by the kernel and kept transparent to the probed 144 application. ) 145 146config HAVE_64BIT_ALIGNED_ACCESS 147 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 148 help 149 Some architectures require 64 bit accesses to be 64 bit 150 aligned, which also requires structs containing 64 bit values 151 to be 64 bit aligned too. This includes some 32 bit 152 architectures which can do 64 bit accesses, as well as 64 bit 153 architectures without unaligned access. 154 155 This symbol should be selected by an architecture if 64 bit 156 accesses are required to be 64 bit aligned in this way even 157 though it is not a 64 bit architecture. 158 159 See Documentation/unaligned-memory-access.txt for more 160 information on the topic of unaligned memory accesses. 161 162config HAVE_EFFICIENT_UNALIGNED_ACCESS 163 bool 164 help 165 Some architectures are unable to perform unaligned accesses 166 without the use of get_unaligned/put_unaligned. Others are 167 unable to perform such accesses efficiently (e.g. trap on 168 unaligned access and require fixing it up in the exception 169 handler.) 170 171 This symbol should be selected by an architecture if it can 172 perform unaligned accesses efficiently to allow different 173 code paths to be selected for these cases. Some network 174 drivers, for example, could opt to not fix up alignment 175 problems with received packets if doing so would not help 176 much. 177 178 See Documentation/core-api/unaligned-memory-access.rst for more 179 information on the topic of unaligned memory accesses. 180 181config ARCH_USE_BUILTIN_BSWAP 182 bool 183 help 184 Modern versions of GCC (since 4.4) have builtin functions 185 for handling byte-swapping. Using these, instead of the old 186 inline assembler that the architecture code provides in the 187 __arch_bswapXX() macros, allows the compiler to see what's 188 happening and offers more opportunity for optimisation. In 189 particular, the compiler will be able to combine the byteswap 190 with a nearby load or store and use load-and-swap or 191 store-and-swap instructions if the architecture has them. It 192 should almost *never* result in code which is worse than the 193 hand-coded assembler in <asm/swab.h>. But just in case it 194 does, the use of the builtins is optional. 195 196 Any architecture with load-and-swap or store-and-swap 197 instructions should set this. And it shouldn't hurt to set it 198 on architectures that don't have such instructions. 199 200config KRETPROBES 201 def_bool y 202 depends on KPROBES && HAVE_KRETPROBES 203 204config USER_RETURN_NOTIFIER 205 bool 206 depends on HAVE_USER_RETURN_NOTIFIER 207 help 208 Provide a kernel-internal notification when a cpu is about to 209 switch to user mode. 210 211config HAVE_IOREMAP_PROT 212 bool 213 214config HAVE_KPROBES 215 bool 216 217config HAVE_KRETPROBES 218 bool 219 220config HAVE_OPTPROBES 221 bool 222 223config HAVE_KPROBES_ON_FTRACE 224 bool 225 226config HAVE_FUNCTION_ERROR_INJECTION 227 bool 228 229config HAVE_NMI 230 bool 231 232# 233# An arch should select this if it provides all these things: 234# 235# task_pt_regs() in asm/processor.h or asm/ptrace.h 236# arch_has_single_step() if there is hardware single-step support 237# arch_has_block_step() if there is hardware block-step support 238# asm/syscall.h supplying asm-generic/syscall.h interface 239# linux/regset.h user_regset interfaces 240# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 241# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 242# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 243# signal delivery calls tracehook_signal_handler() 244# 245config HAVE_ARCH_TRACEHOOK 246 bool 247 248config HAVE_DMA_CONTIGUOUS 249 bool 250 251config GENERIC_SMP_IDLE_THREAD 252 bool 253 254config GENERIC_IDLE_POLL_SETUP 255 bool 256 257config ARCH_HAS_FORTIFY_SOURCE 258 bool 259 help 260 An architecture should select this when it can successfully 261 build and run with CONFIG_FORTIFY_SOURCE. 262 263# 264# Select if the arch provides a historic keepinit alias for the retain_initrd 265# command line option 266# 267config ARCH_HAS_KEEPINITRD 268 bool 269 270# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 271config ARCH_HAS_SET_MEMORY 272 bool 273 274# Select if arch has all set_direct_map_invalid/default() functions 275config ARCH_HAS_SET_DIRECT_MAP 276 bool 277 278# 279# Select if the architecture provides the arch_dma_set_uncached symbol to 280# either provide an uncached segement alias for a DMA allocation, or 281# to remap the page tables in place. 282# 283config ARCH_HAS_DMA_SET_UNCACHED 284 bool 285 286# 287# Select if the architectures provides the arch_dma_clear_uncached symbol 288# to undo an in-place page table remap for uncached access. 289# 290config ARCH_HAS_DMA_CLEAR_UNCACHED 291 bool 292 293config ARCH_HAS_CPU_FINALIZE_INIT 294 bool 295 296# Select if arch init_task must go in the __init_task_data section 297config ARCH_TASK_STRUCT_ON_STACK 298 bool 299 300# Select if arch has its private alloc_task_struct() function 301config ARCH_TASK_STRUCT_ALLOCATOR 302 bool 303 304config HAVE_ARCH_THREAD_STRUCT_WHITELIST 305 bool 306 depends on !ARCH_TASK_STRUCT_ALLOCATOR 307 help 308 An architecture should select this to provide hardened usercopy 309 knowledge about what region of the thread_struct should be 310 whitelisted for copying to userspace. Normally this is only the 311 FPU registers. Specifically, arch_thread_struct_whitelist() 312 should be implemented. Without this, the entire thread_struct 313 field in task_struct will be left whitelisted. 314 315# Select if arch has its private alloc_thread_stack() function 316config ARCH_THREAD_STACK_ALLOCATOR 317 bool 318 319# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 320config ARCH_WANTS_DYNAMIC_TASK_STRUCT 321 bool 322 323config ARCH_32BIT_OFF_T 324 bool 325 depends on !64BIT 326 help 327 All new 32-bit architectures should have 64-bit off_t type on 328 userspace side which corresponds to the loff_t kernel type. This 329 is the requirement for modern ABIs. Some existing architectures 330 still support 32-bit off_t. This option is enabled for all such 331 architectures explicitly. 332 333config HAVE_ASM_MODVERSIONS 334 bool 335 help 336 This symbol should be selected by an architecure if it provides 337 <asm/asm-prototypes.h> to support the module versioning for symbols 338 exported from assembly code. 339 340config HAVE_REGS_AND_STACK_ACCESS_API 341 bool 342 help 343 This symbol should be selected by an architecure if it supports 344 the API needed to access registers and stack entries from pt_regs, 345 declared in asm/ptrace.h 346 For example the kprobes-based event tracer needs this API. 347 348config HAVE_RSEQ 349 bool 350 depends on HAVE_REGS_AND_STACK_ACCESS_API 351 help 352 This symbol should be selected by an architecture if it 353 supports an implementation of restartable sequences. 354 355config HAVE_FUNCTION_ARG_ACCESS_API 356 bool 357 help 358 This symbol should be selected by an architecure if it supports 359 the API needed to access function arguments from pt_regs, 360 declared in asm/ptrace.h 361 362config HAVE_HW_BREAKPOINT 363 bool 364 depends on PERF_EVENTS 365 366config HAVE_MIXED_BREAKPOINTS_REGS 367 bool 368 depends on HAVE_HW_BREAKPOINT 369 help 370 Depending on the arch implementation of hardware breakpoints, 371 some of them have separate registers for data and instruction 372 breakpoints addresses, others have mixed registers to store 373 them but define the access type in a control register. 374 Select this option if your arch implements breakpoints under the 375 latter fashion. 376 377config HAVE_USER_RETURN_NOTIFIER 378 bool 379 380config HAVE_PERF_EVENTS_NMI 381 bool 382 help 383 System hardware can generate an NMI using the perf event 384 subsystem. Also has support for calculating CPU cycle events 385 to determine how many clock cycles in a given period. 386 387config HAVE_HARDLOCKUP_DETECTOR_PERF 388 bool 389 depends on HAVE_PERF_EVENTS_NMI 390 help 391 The arch chooses to use the generic perf-NMI-based hardlockup 392 detector. Must define HAVE_PERF_EVENTS_NMI. 393 394config HAVE_NMI_WATCHDOG 395 depends on HAVE_NMI 396 bool 397 help 398 The arch provides a low level NMI watchdog. It provides 399 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 400 401config HAVE_HARDLOCKUP_DETECTOR_ARCH 402 bool 403 select HAVE_NMI_WATCHDOG 404 help 405 The arch chooses to provide its own hardlockup detector, which is 406 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 407 interfaces and parameters provided by hardlockup detector subsystem. 408 409config HAVE_PERF_REGS 410 bool 411 help 412 Support selective register dumps for perf events. This includes 413 bit-mapping of each registers and a unique architecture id. 414 415config HAVE_PERF_USER_STACK_DUMP 416 bool 417 help 418 Support user stack dumps for perf event samples. This needs 419 access to the user stack pointer which is not unified across 420 architectures. 421 422config HAVE_ARCH_JUMP_LABEL 423 bool 424 425config HAVE_ARCH_JUMP_LABEL_RELATIVE 426 bool 427 428config MMU_GATHER_TABLE_FREE 429 bool 430 431config MMU_GATHER_RCU_TABLE_FREE 432 bool 433 select MMU_GATHER_TABLE_FREE 434 435config MMU_GATHER_PAGE_SIZE 436 bool 437 438config MMU_GATHER_NO_RANGE 439 bool 440 441config MMU_GATHER_NO_GATHER 442 bool 443 depends on MMU_GATHER_TABLE_FREE 444 445config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 446 bool 447 help 448 Temporary select until all architectures can be converted to have 449 irqs disabled over activate_mm. Architectures that do IPI based TLB 450 shootdowns should enable this. 451 452config ARCH_HAVE_NMI_SAFE_CMPXCHG 453 bool 454 455config HAVE_ALIGNED_STRUCT_PAGE 456 bool 457 help 458 This makes sure that struct pages are double word aligned and that 459 e.g. the SLUB allocator can perform double word atomic operations 460 on a struct page for better performance. However selecting this 461 might increase the size of a struct page by a word. 462 463config HAVE_CMPXCHG_LOCAL 464 bool 465 466config HAVE_CMPXCHG_DOUBLE 467 bool 468 469config ARCH_WEAK_RELEASE_ACQUIRE 470 bool 471 472config ARCH_WANT_IPC_PARSE_VERSION 473 bool 474 475config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 476 bool 477 478config ARCH_WANT_OLD_COMPAT_IPC 479 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 480 bool 481 482config HAVE_ARCH_SECCOMP 483 bool 484 help 485 An arch should select this symbol to support seccomp mode 1 (the fixed 486 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 487 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 488 - __NR_seccomp_read_32 489 - __NR_seccomp_write_32 490 - __NR_seccomp_exit_32 491 - __NR_seccomp_sigreturn_32 492 493config HAVE_ARCH_SECCOMP_FILTER 494 bool 495 select HAVE_ARCH_SECCOMP 496 help 497 An arch should select this symbol if it provides all of these things: 498 - all the requirements for HAVE_ARCH_SECCOMP 499 - syscall_get_arch() 500 - syscall_get_arguments() 501 - syscall_rollback() 502 - syscall_set_return_value() 503 - SIGSYS siginfo_t support 504 - secure_computing is called from a ptrace_event()-safe context 505 - secure_computing return value is checked and a return value of -1 506 results in the system call being skipped immediately. 507 - seccomp syscall wired up 508 509config SECCOMP 510 prompt "Enable seccomp to safely execute untrusted bytecode" 511 def_bool y 512 depends on HAVE_ARCH_SECCOMP 513 help 514 This kernel feature is useful for number crunching applications 515 that may need to handle untrusted bytecode during their 516 execution. By using pipes or other transports made available 517 to the process as file descriptors supporting the read/write 518 syscalls, it's possible to isolate those applications in their 519 own address space using seccomp. Once seccomp is enabled via 520 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 521 disabled and the task is only allowed to execute a few safe 522 syscalls defined by each seccomp mode. 523 524 If unsure, say Y. 525 526config SECCOMP_FILTER 527 def_bool y 528 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 529 help 530 Enable tasks to build secure computing environments defined 531 in terms of Berkeley Packet Filter programs which implement 532 task-defined system call filtering polices. 533 534 See Documentation/userspace-api/seccomp_filter.rst for details. 535 536config HAVE_ARCH_STACKLEAK 537 bool 538 help 539 An architecture should select this if it has the code which 540 fills the used part of the kernel stack with the STACKLEAK_POISON 541 value before returning from system calls. 542 543config HAVE_STACKPROTECTOR 544 bool 545 help 546 An arch should select this symbol if: 547 - it has implemented a stack canary (e.g. __stack_chk_guard) 548 549config STACKPROTECTOR 550 bool "Stack Protector buffer overflow detection" 551 depends on HAVE_STACKPROTECTOR 552 depends on $(cc-option,-fstack-protector) 553 default y 554 help 555 This option turns on the "stack-protector" GCC feature. This 556 feature puts, at the beginning of functions, a canary value on 557 the stack just before the return address, and validates 558 the value just before actually returning. Stack based buffer 559 overflows (that need to overwrite this return address) now also 560 overwrite the canary, which gets detected and the attack is then 561 neutralized via a kernel panic. 562 563 Functions will have the stack-protector canary logic added if they 564 have an 8-byte or larger character array on the stack. 565 566 This feature requires gcc version 4.2 or above, or a distribution 567 gcc with the feature backported ("-fstack-protector"). 568 569 On an x86 "defconfig" build, this feature adds canary checks to 570 about 3% of all kernel functions, which increases kernel code size 571 by about 0.3%. 572 573config STACKPROTECTOR_STRONG 574 bool "Strong Stack Protector" 575 depends on STACKPROTECTOR 576 depends on $(cc-option,-fstack-protector-strong) 577 default y 578 help 579 Functions will have the stack-protector canary logic added in any 580 of the following conditions: 581 582 - local variable's address used as part of the right hand side of an 583 assignment or function argument 584 - local variable is an array (or union containing an array), 585 regardless of array type or length 586 - uses register local variables 587 588 This feature requires gcc version 4.9 or above, or a distribution 589 gcc with the feature backported ("-fstack-protector-strong"). 590 591 On an x86 "defconfig" build, this feature adds canary checks to 592 about 20% of all kernel functions, which increases the kernel code 593 size by about 2%. 594 595config ARCH_SUPPORTS_SHADOW_CALL_STACK 596 bool 597 help 598 An architecture should select this if it supports Clang's Shadow 599 Call Stack and implements runtime support for shadow stack 600 switching. 601 602config SHADOW_CALL_STACK 603 bool "Clang Shadow Call Stack" 604 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 605 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 606 help 607 This option enables Clang's Shadow Call Stack, which uses a 608 shadow stack to protect function return addresses from being 609 overwritten by an attacker. More information can be found in 610 Clang's documentation: 611 612 https://clang.llvm.org/docs/ShadowCallStack.html 613 614 Note that security guarantees in the kernel differ from the 615 ones documented for user space. The kernel must store addresses 616 of shadow stacks in memory, which means an attacker capable of 617 reading and writing arbitrary memory may be able to locate them 618 and hijack control flow by modifying the stacks. 619 620config LTO 621 bool 622 help 623 Selected if the kernel will be built using the compiler's LTO feature. 624 625config LTO_CLANG 626 bool 627 select LTO 628 help 629 Selected if the kernel will be built using Clang's LTO feature. 630 631config ARCH_SUPPORTS_LTO_CLANG 632 bool 633 help 634 An architecture should select this option if it supports: 635 - compiling with Clang, 636 - compiling inline assembly with Clang's integrated assembler, 637 - and linking with LLD. 638 639config ARCH_SUPPORTS_LTO_CLANG_THIN 640 bool 641 help 642 An architecture should select this option if it can support Clang's 643 ThinLTO mode. 644 645config HAS_LTO_CLANG 646 def_bool y 647 # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510 648 depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD 649 depends on $(success,test $(LLVM_IAS) -eq 1) 650 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) 651 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) 652 depends on ARCH_SUPPORTS_LTO_CLANG 653 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT 654 depends on !KASAN 655 depends on !GCOV_KERNEL 656 help 657 The compiler and Kconfig options support building with Clang's 658 LTO. 659 660choice 661 prompt "Link Time Optimization (LTO)" 662 default LTO_NONE 663 help 664 This option enables Link Time Optimization (LTO), which allows the 665 compiler to optimize binaries globally. 666 667 If unsure, select LTO_NONE. Note that LTO is very resource-intensive 668 so it's disabled by default. 669 670config LTO_NONE 671 bool "None" 672 help 673 Build the kernel normally, without Link Time Optimization (LTO). 674 675config LTO_CLANG_FULL 676 bool "Clang Full LTO (EXPERIMENTAL)" 677 depends on HAS_LTO_CLANG 678 depends on !COMPILE_TEST 679 select LTO_CLANG 680 help 681 This option enables Clang's full Link Time Optimization (LTO), which 682 allows the compiler to optimize the kernel globally. If you enable 683 this option, the compiler generates LLVM bitcode instead of ELF 684 object files, and the actual compilation from bitcode happens at 685 the LTO link step, which may take several minutes depending on the 686 kernel configuration. More information can be found from LLVM's 687 documentation: 688 689 https://llvm.org/docs/LinkTimeOptimization.html 690 691 During link time, this option can use a large amount of RAM, and 692 may take much longer than the ThinLTO option. 693 694config LTO_CLANG_THIN 695 bool "Clang ThinLTO (EXPERIMENTAL)" 696 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN 697 select LTO_CLANG 698 help 699 This option enables Clang's ThinLTO, which allows for parallel 700 optimization and faster incremental compiles compared to the 701 CONFIG_LTO_CLANG_FULL option. More information can be found 702 from Clang's documentation: 703 704 https://clang.llvm.org/docs/ThinLTO.html 705 706 If unsure, say Y. 707endchoice 708 709config ARCH_SUPPORTS_CFI_CLANG 710 bool 711 help 712 An architecture should select this option if it can support Clang's 713 Control-Flow Integrity (CFI) checking. 714 715config CFI_CLANG 716 bool "Use Clang's Control Flow Integrity (CFI)" 717 depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG 718 # Clang >= 12: 719 # - https://bugs.llvm.org/show_bug.cgi?id=46258 720 # - https://bugs.llvm.org/show_bug.cgi?id=47479 721 depends on CLANG_VERSION >= 120000 722 select KALLSYMS 723 help 724 This option enables Clang’s forward-edge Control Flow Integrity 725 (CFI) checking, where the compiler injects a runtime check to each 726 indirect function call to ensure the target is a valid function with 727 the correct static type. This restricts possible call targets and 728 makes it more difficult for an attacker to exploit bugs that allow 729 the modification of stored function pointers. More information can be 730 found from Clang's documentation: 731 732 https://clang.llvm.org/docs/ControlFlowIntegrity.html 733 734config CFI_CLANG_SHADOW 735 bool "Use CFI shadow to speed up cross-module checks" 736 default y 737 depends on CFI_CLANG && MODULES 738 help 739 If you select this option, the kernel builds a fast look-up table of 740 CFI check functions in loaded modules to reduce performance overhead. 741 742 If unsure, say Y. 743 744config CFI_PERMISSIVE 745 bool "Use CFI in permissive mode" 746 depends on CFI_CLANG 747 help 748 When selected, Control Flow Integrity (CFI) violations result in a 749 warning instead of a kernel panic. This option should only be used 750 for finding indirect call type mismatches during development. 751 752 If unsure, say N. 753 754config HAVE_ARCH_WITHIN_STACK_FRAMES 755 bool 756 help 757 An architecture should select this if it can walk the kernel stack 758 frames to determine if an object is part of either the arguments 759 or local variables (i.e. that it excludes saved return addresses, 760 and similar) by implementing an inline arch_within_stack_frames(), 761 which is used by CONFIG_HARDENED_USERCOPY. 762 763config HAVE_CONTEXT_TRACKING 764 bool 765 help 766 Provide kernel/user boundaries probes necessary for subsystems 767 that need it, such as userspace RCU extended quiescent state. 768 Syscalls need to be wrapped inside user_exit()-user_enter(), either 769 optimized behind static key or through the slow path using TIF_NOHZ 770 flag. Exceptions handlers must be wrapped as well. Irqs are already 771 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 772 handling on irq exit still need to be protected. 773 774config HAVE_TIF_NOHZ 775 bool 776 help 777 Arch relies on TIF_NOHZ and syscall slow path to implement context 778 tracking calls to user_enter()/user_exit(). 779 780config HAVE_VIRT_CPU_ACCOUNTING 781 bool 782 783config ARCH_HAS_SCALED_CPUTIME 784 bool 785 786config HAVE_VIRT_CPU_ACCOUNTING_GEN 787 bool 788 default y if 64BIT 789 help 790 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 791 Before enabling this option, arch code must be audited 792 to ensure there are no races in concurrent read/write of 793 cputime_t. For example, reading/writing 64-bit cputime_t on 794 some 32-bit arches may require multiple accesses, so proper 795 locking is needed to protect against concurrent accesses. 796 797 798config HAVE_IRQ_TIME_ACCOUNTING 799 bool 800 help 801 Archs need to ensure they use a high enough resolution clock to 802 support irq time accounting and then call enable_sched_clock_irqtime(). 803 804config HAVE_MOVE_PMD 805 bool 806 help 807 Archs that select this are able to move page tables at the PMD level. 808 809config HAVE_ARCH_TRANSPARENT_HUGEPAGE 810 bool 811 812config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 813 bool 814 815config HAVE_ARCH_HUGE_VMAP 816 bool 817 818config ARCH_WANT_HUGE_PMD_SHARE 819 bool 820 821config HAVE_ARCH_SOFT_DIRTY 822 bool 823 824config HAVE_MOD_ARCH_SPECIFIC 825 bool 826 help 827 The arch uses struct mod_arch_specific to store data. Many arches 828 just need a simple module loader without arch specific data - those 829 should not enable this. 830 831config MODULES_USE_ELF_RELA 832 bool 833 help 834 Modules only use ELF RELA relocations. Modules with ELF REL 835 relocations will give an error. 836 837config MODULES_USE_ELF_REL 838 bool 839 help 840 Modules only use ELF REL relocations. Modules with ELF RELA 841 relocations will give an error. 842 843config HAVE_IRQ_EXIT_ON_IRQ_STACK 844 bool 845 help 846 Architecture doesn't only execute the irq handler on the irq stack 847 but also irq_exit(). This way we can process softirqs on this irq 848 stack instead of switching to a new one when we call __do_softirq() 849 in the end of an hardirq. 850 This spares a stack switch and improves cache usage on softirq 851 processing. 852 853config PGTABLE_LEVELS 854 int 855 default 2 856 857config ARCH_HAS_ELF_RANDOMIZE 858 bool 859 help 860 An architecture supports choosing randomized locations for 861 stack, mmap, brk, and ET_DYN. Defined functions: 862 - arch_mmap_rnd() 863 - arch_randomize_brk() 864 865config HAVE_ARCH_MMAP_RND_BITS 866 bool 867 help 868 An arch should select this symbol if it supports setting a variable 869 number of bits for use in establishing the base address for mmap 870 allocations, has MMU enabled and provides values for both: 871 - ARCH_MMAP_RND_BITS_MIN 872 - ARCH_MMAP_RND_BITS_MAX 873 874config HAVE_EXIT_THREAD 875 bool 876 help 877 An architecture implements exit_thread. 878 879config ARCH_MMAP_RND_BITS_MIN 880 int 881 882config ARCH_MMAP_RND_BITS_MAX 883 int 884 885config ARCH_MMAP_RND_BITS_DEFAULT 886 int 887 888config ARCH_MMAP_RND_BITS 889 int "Number of bits to use for ASLR of mmap base address" if EXPERT 890 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 891 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 892 default ARCH_MMAP_RND_BITS_MIN 893 depends on HAVE_ARCH_MMAP_RND_BITS 894 help 895 This value can be used to select the number of bits to use to 896 determine the random offset to the base address of vma regions 897 resulting from mmap allocations. This value will be bounded 898 by the architecture's minimum and maximum supported values. 899 900 This value can be changed after boot using the 901 /proc/sys/vm/mmap_rnd_bits tunable 902 903config HAVE_ARCH_MMAP_RND_COMPAT_BITS 904 bool 905 help 906 An arch should select this symbol if it supports running applications 907 in compatibility mode, supports setting a variable number of bits for 908 use in establishing the base address for mmap allocations, has MMU 909 enabled and provides values for both: 910 - ARCH_MMAP_RND_COMPAT_BITS_MIN 911 - ARCH_MMAP_RND_COMPAT_BITS_MAX 912 913config ARCH_MMAP_RND_COMPAT_BITS_MIN 914 int 915 916config ARCH_MMAP_RND_COMPAT_BITS_MAX 917 int 918 919config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 920 int 921 922config ARCH_MMAP_RND_COMPAT_BITS 923 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 924 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 925 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 926 default ARCH_MMAP_RND_COMPAT_BITS_MIN 927 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 928 help 929 This value can be used to select the number of bits to use to 930 determine the random offset to the base address of vma regions 931 resulting from mmap allocations for compatible applications This 932 value will be bounded by the architecture's minimum and maximum 933 supported values. 934 935 This value can be changed after boot using the 936 /proc/sys/vm/mmap_rnd_compat_bits tunable 937 938config HAVE_ARCH_COMPAT_MMAP_BASES 939 bool 940 help 941 This allows 64bit applications to invoke 32-bit mmap() syscall 942 and vice-versa 32-bit applications to call 64-bit mmap(). 943 Required for applications doing different bitness syscalls. 944 945# This allows to use a set of generic functions to determine mmap base 946# address by giving priority to top-down scheme only if the process 947# is not in legacy mode (compat task, unlimited stack size or 948# sysctl_legacy_va_layout). 949# Architecture that selects this option can provide its own version of: 950# - STACK_RND_MASK 951config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 952 bool 953 depends on MMU 954 select ARCH_HAS_ELF_RANDOMIZE 955 956config HAVE_STACK_VALIDATION 957 bool 958 help 959 Architecture supports the 'objtool check' host tool command, which 960 performs compile-time stack metadata validation. 961 962config HAVE_RELIABLE_STACKTRACE 963 bool 964 help 965 Architecture has either save_stack_trace_tsk_reliable() or 966 arch_stack_walk_reliable() function which only returns a stack trace 967 if it can guarantee the trace is reliable. 968 969config HAVE_ARCH_HASH 970 bool 971 default n 972 help 973 If this is set, the architecture provides an <asm/hash.h> 974 file which provides platform-specific implementations of some 975 functions in <linux/hash.h> or fs/namei.c. 976 977config HAVE_ARCH_NVRAM_OPS 978 bool 979 980config ISA_BUS_API 981 def_bool ISA 982 983# 984# ABI hall of shame 985# 986config CLONE_BACKWARDS 987 bool 988 help 989 Architecture has tls passed as the 4th argument of clone(2), 990 not the 5th one. 991 992config CLONE_BACKWARDS2 993 bool 994 help 995 Architecture has the first two arguments of clone(2) swapped. 996 997config CLONE_BACKWARDS3 998 bool 999 help 1000 Architecture has tls passed as the 3rd argument of clone(2), 1001 not the 5th one. 1002 1003config ODD_RT_SIGACTION 1004 bool 1005 help 1006 Architecture has unusual rt_sigaction(2) arguments 1007 1008config OLD_SIGSUSPEND 1009 bool 1010 help 1011 Architecture has old sigsuspend(2) syscall, of one-argument variety 1012 1013config OLD_SIGSUSPEND3 1014 bool 1015 help 1016 Even weirder antique ABI - three-argument sigsuspend(2) 1017 1018config OLD_SIGACTION 1019 bool 1020 help 1021 Architecture has old sigaction(2) syscall. Nope, not the same 1022 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 1023 but fairly different variant of sigaction(2), thanks to OSF/1 1024 compatibility... 1025 1026config COMPAT_OLD_SIGACTION 1027 bool 1028 1029config COMPAT_32BIT_TIME 1030 bool "Provide system calls for 32-bit time_t" 1031 default !64BIT || COMPAT 1032 help 1033 This enables 32 bit time_t support in addition to 64 bit time_t support. 1034 This is relevant on all 32-bit architectures, and 64-bit architectures 1035 as part of compat syscall handling. 1036 1037config ARCH_NO_PREEMPT 1038 bool 1039 1040config ARCH_SUPPORTS_RT 1041 bool 1042 1043config CPU_NO_EFFICIENT_FFS 1044 def_bool n 1045 1046config HAVE_ARCH_VMAP_STACK 1047 def_bool n 1048 help 1049 An arch should select this symbol if it can support kernel stacks 1050 in vmalloc space. This means: 1051 1052 - vmalloc space must be large enough to hold many kernel stacks. 1053 This may rule out many 32-bit architectures. 1054 1055 - Stacks in vmalloc space need to work reliably. For example, if 1056 vmap page tables are created on demand, either this mechanism 1057 needs to work while the stack points to a virtual address with 1058 unpopulated page tables or arch code (switch_to() and switch_mm(), 1059 most likely) needs to ensure that the stack's page table entries 1060 are populated before running on a possibly unpopulated stack. 1061 1062 - If the stack overflows into a guard page, something reasonable 1063 should happen. The definition of "reasonable" is flexible, but 1064 instantly rebooting without logging anything would be unfriendly. 1065 1066config VMAP_STACK 1067 default y 1068 bool "Use a virtually-mapped stack" 1069 depends on HAVE_ARCH_VMAP_STACK 1070 depends on !KASAN || KASAN_VMALLOC 1071 help 1072 Enable this if you want the use virtually-mapped kernel stacks 1073 with guard pages. This causes kernel stack overflows to be 1074 caught immediately rather than causing difficult-to-diagnose 1075 corruption. 1076 1077 To use this with KASAN, the architecture must support backing 1078 virtual mappings with real shadow memory, and KASAN_VMALLOC must 1079 be enabled. 1080 1081config ARCH_OPTIONAL_KERNEL_RWX 1082 def_bool n 1083 1084config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1085 def_bool n 1086 1087config ARCH_HAS_STRICT_KERNEL_RWX 1088 def_bool n 1089 1090config STRICT_KERNEL_RWX 1091 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 1092 depends on ARCH_HAS_STRICT_KERNEL_RWX 1093 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1094 help 1095 If this is set, kernel text and rodata memory will be made read-only, 1096 and non-text memory will be made non-executable. This provides 1097 protection against certain security exploits (e.g. executing the heap 1098 or modifying text) 1099 1100 These features are considered standard security practice these days. 1101 You should say Y here in almost all cases. 1102 1103config ARCH_HAS_STRICT_MODULE_RWX 1104 def_bool n 1105 1106config STRICT_MODULE_RWX 1107 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 1108 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 1109 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1110 help 1111 If this is set, module text and rodata memory will be made read-only, 1112 and non-text memory will be made non-executable. This provides 1113 protection against certain security exploits (e.g. writing to text) 1114 1115# select if the architecture provides an asm/dma-direct.h header 1116config ARCH_HAS_PHYS_TO_DMA 1117 bool 1118 1119config HAVE_ARCH_COMPILER_H 1120 bool 1121 help 1122 An architecture can select this if it provides an 1123 asm/compiler.h header that should be included after 1124 linux/compiler-*.h in order to override macro definitions that those 1125 headers generally provide. 1126 1127config HAVE_ARCH_PREL32_RELOCATIONS 1128 bool 1129 help 1130 May be selected by an architecture if it supports place-relative 1131 32-bit relocations, both in the toolchain and in the module loader, 1132 in which case relative references can be used in special sections 1133 for PCI fixup, initcalls etc which are only half the size on 64 bit 1134 architectures, and don't require runtime relocation on relocatable 1135 kernels. 1136 1137config ARCH_USE_MEMREMAP_PROT 1138 bool 1139 1140config LOCK_EVENT_COUNTS 1141 bool "Locking event counts collection" 1142 depends on DEBUG_FS 1143 help 1144 Enable light-weight counting of various locking related events 1145 in the system with minimal performance impact. This reduces 1146 the chance of application behavior change because of timing 1147 differences. The counts are reported via debugfs. 1148 1149# Select if the architecture has support for applying RELR relocations. 1150config ARCH_HAS_RELR 1151 bool 1152 1153config RELR 1154 bool "Use RELR relocation packing" 1155 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1156 default y 1157 help 1158 Store the kernel's dynamic relocations in the RELR relocation packing 1159 format. Requires a compatible linker (LLD supports this feature), as 1160 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1161 are compatible). 1162 1163config ARCH_HAS_MEM_ENCRYPT 1164 bool 1165 1166config ARCH_HAS_CC_PLATFORM 1167 bool 1168 1169config HAVE_SPARSE_SYSCALL_NR 1170 bool 1171 help 1172 An architecture should select this if its syscall numbering is sparse 1173 to save space. For example, MIPS architecture has a syscall array with 1174 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1175 related optimizations for a given architecture. 1176 1177config ARCH_HAS_VDSO_DATA 1178 bool 1179 1180config HAVE_STATIC_CALL 1181 bool 1182 1183config HAVE_STATIC_CALL_INLINE 1184 bool 1185 depends on HAVE_STATIC_CALL 1186 1187config ARCH_WANT_LD_ORPHAN_WARN 1188 bool 1189 help 1190 An arch should select this symbol once all linker sections are explicitly 1191 included, size-asserted, or discarded in the linker scripts. This is 1192 important because we never want expected sections to be placed heuristically 1193 by the linker, since the locations of such sections can change between linker 1194 versions. 1195 1196config ARCH_SPLIT_ARG64 1197 bool 1198 help 1199 If a 32-bit architecture requires 64-bit arguments to be split into 1200 pairs of 32-bit arguments, select this option. 1201 1202source "kernel/gcov/Kconfig" 1203 1204source "scripts/gcc-plugins/Kconfig" 1205 1206endmenu 1207