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_EFFICIENT_UNALIGNED_ACCESS 147 bool 148 help 149 Some architectures are unable to perform unaligned accesses 150 without the use of get_unaligned/put_unaligned. Others are 151 unable to perform such accesses efficiently (e.g. trap on 152 unaligned access and require fixing it up in the exception 153 handler.) 154 155 This symbol should be selected by an architecture if it can 156 perform unaligned accesses efficiently to allow different 157 code paths to be selected for these cases. Some network 158 drivers, for example, could opt to not fix up alignment 159 problems with received packets if doing so would not help 160 much. 161 162 See Documentation/core-api/unaligned-memory-access.rst for more 163 information on the topic of unaligned memory accesses. 164 165config ARCH_USE_BUILTIN_BSWAP 166 bool 167 help 168 Modern versions of GCC (since 4.4) have builtin functions 169 for handling byte-swapping. Using these, instead of the old 170 inline assembler that the architecture code provides in the 171 __arch_bswapXX() macros, allows the compiler to see what's 172 happening and offers more opportunity for optimisation. In 173 particular, the compiler will be able to combine the byteswap 174 with a nearby load or store and use load-and-swap or 175 store-and-swap instructions if the architecture has them. It 176 should almost *never* result in code which is worse than the 177 hand-coded assembler in <asm/swab.h>. But just in case it 178 does, the use of the builtins is optional. 179 180 Any architecture with load-and-swap or store-and-swap 181 instructions should set this. And it shouldn't hurt to set it 182 on architectures that don't have such instructions. 183 184config KRETPROBES 185 def_bool y 186 depends on KPROBES && HAVE_KRETPROBES 187 188config USER_RETURN_NOTIFIER 189 bool 190 depends on HAVE_USER_RETURN_NOTIFIER 191 help 192 Provide a kernel-internal notification when a cpu is about to 193 switch to user mode. 194 195config HAVE_IOREMAP_PROT 196 bool 197 198config HAVE_KPROBES 199 bool 200 201config HAVE_KRETPROBES 202 bool 203 204config HAVE_OPTPROBES 205 bool 206 207config HAVE_KPROBES_ON_FTRACE 208 bool 209 210config HAVE_FUNCTION_ERROR_INJECTION 211 bool 212 213config HAVE_NMI 214 bool 215 216# 217# An arch should select this if it provides all these things: 218# 219# task_pt_regs() in asm/processor.h or asm/ptrace.h 220# arch_has_single_step() if there is hardware single-step support 221# arch_has_block_step() if there is hardware block-step support 222# asm/syscall.h supplying asm-generic/syscall.h interface 223# linux/regset.h user_regset interfaces 224# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 225# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 226# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 227# signal delivery calls tracehook_signal_handler() 228# 229config HAVE_ARCH_TRACEHOOK 230 bool 231 232config HAVE_DMA_CONTIGUOUS 233 bool 234 235config GENERIC_SMP_IDLE_THREAD 236 bool 237 238config GENERIC_IDLE_POLL_SETUP 239 bool 240 241config ARCH_HAS_FORTIFY_SOURCE 242 bool 243 help 244 An architecture should select this when it can successfully 245 build and run with CONFIG_FORTIFY_SOURCE. 246 247# 248# Select if the arch provides a historic keepinit alias for the retain_initrd 249# command line option 250# 251config ARCH_HAS_KEEPINITRD 252 bool 253 254# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 255config ARCH_HAS_SET_MEMORY 256 bool 257 258# Select if arch has all set_direct_map_invalid/default() functions 259config ARCH_HAS_SET_DIRECT_MAP 260 bool 261 262# 263# Select if the architecture provides the arch_dma_set_uncached symbol to 264# either provide an uncached segement alias for a DMA allocation, or 265# to remap the page tables in place. 266# 267config ARCH_HAS_DMA_SET_UNCACHED 268 bool 269 270# 271# Select if the architectures provides the arch_dma_clear_uncached symbol 272# to undo an in-place page table remap for uncached access. 273# 274config ARCH_HAS_DMA_CLEAR_UNCACHED 275 bool 276 277# Select if arch init_task must go in the __init_task_data section 278config ARCH_TASK_STRUCT_ON_STACK 279 bool 280 281# Select if arch has its private alloc_task_struct() function 282config ARCH_TASK_STRUCT_ALLOCATOR 283 bool 284 285config HAVE_ARCH_THREAD_STRUCT_WHITELIST 286 bool 287 depends on !ARCH_TASK_STRUCT_ALLOCATOR 288 help 289 An architecture should select this to provide hardened usercopy 290 knowledge about what region of the thread_struct should be 291 whitelisted for copying to userspace. Normally this is only the 292 FPU registers. Specifically, arch_thread_struct_whitelist() 293 should be implemented. Without this, the entire thread_struct 294 field in task_struct will be left whitelisted. 295 296# Select if arch has its private alloc_thread_stack() function 297config ARCH_THREAD_STACK_ALLOCATOR 298 bool 299 300# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 301config ARCH_WANTS_DYNAMIC_TASK_STRUCT 302 bool 303 304config ARCH_32BIT_OFF_T 305 bool 306 depends on !64BIT 307 help 308 All new 32-bit architectures should have 64-bit off_t type on 309 userspace side which corresponds to the loff_t kernel type. This 310 is the requirement for modern ABIs. Some existing architectures 311 still support 32-bit off_t. This option is enabled for all such 312 architectures explicitly. 313 314config HAVE_ASM_MODVERSIONS 315 bool 316 help 317 This symbol should be selected by an architecure if it provides 318 <asm/asm-prototypes.h> to support the module versioning for symbols 319 exported from assembly code. 320 321config HAVE_REGS_AND_STACK_ACCESS_API 322 bool 323 help 324 This symbol should be selected by an architecure if it supports 325 the API needed to access registers and stack entries from pt_regs, 326 declared in asm/ptrace.h 327 For example the kprobes-based event tracer needs this API. 328 329config HAVE_RSEQ 330 bool 331 depends on HAVE_REGS_AND_STACK_ACCESS_API 332 help 333 This symbol should be selected by an architecture if it 334 supports an implementation of restartable sequences. 335 336config HAVE_FUNCTION_ARG_ACCESS_API 337 bool 338 help 339 This symbol should be selected by an architecure if it supports 340 the API needed to access function arguments from pt_regs, 341 declared in asm/ptrace.h 342 343config HAVE_HW_BREAKPOINT 344 bool 345 depends on PERF_EVENTS 346 347config HAVE_MIXED_BREAKPOINTS_REGS 348 bool 349 depends on HAVE_HW_BREAKPOINT 350 help 351 Depending on the arch implementation of hardware breakpoints, 352 some of them have separate registers for data and instruction 353 breakpoints addresses, others have mixed registers to store 354 them but define the access type in a control register. 355 Select this option if your arch implements breakpoints under the 356 latter fashion. 357 358config HAVE_USER_RETURN_NOTIFIER 359 bool 360 361config HAVE_PERF_EVENTS_NMI 362 bool 363 help 364 System hardware can generate an NMI using the perf event 365 subsystem. Also has support for calculating CPU cycle events 366 to determine how many clock cycles in a given period. 367 368config HAVE_HARDLOCKUP_DETECTOR_PERF 369 bool 370 depends on HAVE_PERF_EVENTS_NMI 371 help 372 The arch chooses to use the generic perf-NMI-based hardlockup 373 detector. Must define HAVE_PERF_EVENTS_NMI. 374 375config HAVE_NMI_WATCHDOG 376 depends on HAVE_NMI 377 bool 378 help 379 The arch provides a low level NMI watchdog. It provides 380 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 381 382config HAVE_HARDLOCKUP_DETECTOR_ARCH 383 bool 384 select HAVE_NMI_WATCHDOG 385 help 386 The arch chooses to provide its own hardlockup detector, which is 387 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 388 interfaces and parameters provided by hardlockup detector subsystem. 389 390config HAVE_PERF_REGS 391 bool 392 help 393 Support selective register dumps for perf events. This includes 394 bit-mapping of each registers and a unique architecture id. 395 396config HAVE_PERF_USER_STACK_DUMP 397 bool 398 help 399 Support user stack dumps for perf event samples. This needs 400 access to the user stack pointer which is not unified across 401 architectures. 402 403config HAVE_ARCH_JUMP_LABEL 404 bool 405 406config HAVE_ARCH_JUMP_LABEL_RELATIVE 407 bool 408 409config MMU_GATHER_TABLE_FREE 410 bool 411 412config MMU_GATHER_RCU_TABLE_FREE 413 bool 414 select MMU_GATHER_TABLE_FREE 415 416config MMU_GATHER_PAGE_SIZE 417 bool 418 419config MMU_GATHER_NO_RANGE 420 bool 421 422config MMU_GATHER_NO_GATHER 423 bool 424 depends on MMU_GATHER_TABLE_FREE 425 426config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 427 bool 428 help 429 Temporary select until all architectures can be converted to have 430 irqs disabled over activate_mm. Architectures that do IPI based TLB 431 shootdowns should enable this. 432 433config ARCH_HAVE_NMI_SAFE_CMPXCHG 434 bool 435 436config HAVE_ALIGNED_STRUCT_PAGE 437 bool 438 help 439 This makes sure that struct pages are double word aligned and that 440 e.g. the SLUB allocator can perform double word atomic operations 441 on a struct page for better performance. However selecting this 442 might increase the size of a struct page by a word. 443 444config HAVE_CMPXCHG_LOCAL 445 bool 446 447config HAVE_CMPXCHG_DOUBLE 448 bool 449 450config ARCH_WEAK_RELEASE_ACQUIRE 451 bool 452 453config ARCH_WANT_IPC_PARSE_VERSION 454 bool 455 456config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 457 bool 458 459config ARCH_WANT_OLD_COMPAT_IPC 460 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 461 bool 462 463config HAVE_ARCH_SECCOMP 464 bool 465 help 466 An arch should select this symbol to support seccomp mode 1 (the fixed 467 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 468 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 469 - __NR_seccomp_read_32 470 - __NR_seccomp_write_32 471 - __NR_seccomp_exit_32 472 - __NR_seccomp_sigreturn_32 473 474config HAVE_ARCH_SECCOMP_FILTER 475 bool 476 select HAVE_ARCH_SECCOMP 477 help 478 An arch should select this symbol if it provides all of these things: 479 - all the requirements for HAVE_ARCH_SECCOMP 480 - syscall_get_arch() 481 - syscall_get_arguments() 482 - syscall_rollback() 483 - syscall_set_return_value() 484 - SIGSYS siginfo_t support 485 - secure_computing is called from a ptrace_event()-safe context 486 - secure_computing return value is checked and a return value of -1 487 results in the system call being skipped immediately. 488 - seccomp syscall wired up 489 490config SECCOMP 491 prompt "Enable seccomp to safely execute untrusted bytecode" 492 def_bool y 493 depends on HAVE_ARCH_SECCOMP 494 help 495 This kernel feature is useful for number crunching applications 496 that may need to handle untrusted bytecode during their 497 execution. By using pipes or other transports made available 498 to the process as file descriptors supporting the read/write 499 syscalls, it's possible to isolate those applications in their 500 own address space using seccomp. Once seccomp is enabled via 501 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 502 disabled and the task is only allowed to execute a few safe 503 syscalls defined by each seccomp mode. 504 505 If unsure, say Y. 506 507config SECCOMP_FILTER 508 def_bool y 509 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 510 help 511 Enable tasks to build secure computing environments defined 512 in terms of Berkeley Packet Filter programs which implement 513 task-defined system call filtering polices. 514 515 See Documentation/userspace-api/seccomp_filter.rst for details. 516 517config HAVE_ARCH_STACKLEAK 518 bool 519 help 520 An architecture should select this if it has the code which 521 fills the used part of the kernel stack with the STACKLEAK_POISON 522 value before returning from system calls. 523 524config HAVE_STACKPROTECTOR 525 bool 526 help 527 An arch should select this symbol if: 528 - it has implemented a stack canary (e.g. __stack_chk_guard) 529 530config STACKPROTECTOR 531 bool "Stack Protector buffer overflow detection" 532 depends on HAVE_STACKPROTECTOR 533 depends on $(cc-option,-fstack-protector) 534 default y 535 help 536 This option turns on the "stack-protector" GCC feature. This 537 feature puts, at the beginning of functions, a canary value on 538 the stack just before the return address, and validates 539 the value just before actually returning. Stack based buffer 540 overflows (that need to overwrite this return address) now also 541 overwrite the canary, which gets detected and the attack is then 542 neutralized via a kernel panic. 543 544 Functions will have the stack-protector canary logic added if they 545 have an 8-byte or larger character array on the stack. 546 547 This feature requires gcc version 4.2 or above, or a distribution 548 gcc with the feature backported ("-fstack-protector"). 549 550 On an x86 "defconfig" build, this feature adds canary checks to 551 about 3% of all kernel functions, which increases kernel code size 552 by about 0.3%. 553 554config STACKPROTECTOR_STRONG 555 bool "Strong Stack Protector" 556 depends on STACKPROTECTOR 557 depends on $(cc-option,-fstack-protector-strong) 558 default y 559 help 560 Functions will have the stack-protector canary logic added in any 561 of the following conditions: 562 563 - local variable's address used as part of the right hand side of an 564 assignment or function argument 565 - local variable is an array (or union containing an array), 566 regardless of array type or length 567 - uses register local variables 568 569 This feature requires gcc version 4.9 or above, or a distribution 570 gcc with the feature backported ("-fstack-protector-strong"). 571 572 On an x86 "defconfig" build, this feature adds canary checks to 573 about 20% of all kernel functions, which increases the kernel code 574 size by about 2%. 575 576config ARCH_SUPPORTS_SHADOW_CALL_STACK 577 bool 578 help 579 An architecture should select this if it supports Clang's Shadow 580 Call Stack and implements runtime support for shadow stack 581 switching. 582 583config SHADOW_CALL_STACK 584 bool "Clang Shadow Call Stack" 585 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 586 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 587 help 588 This option enables Clang's Shadow Call Stack, which uses a 589 shadow stack to protect function return addresses from being 590 overwritten by an attacker. More information can be found in 591 Clang's documentation: 592 593 https://clang.llvm.org/docs/ShadowCallStack.html 594 595 Note that security guarantees in the kernel differ from the 596 ones documented for user space. The kernel must store addresses 597 of shadow stacks in memory, which means an attacker capable of 598 reading and writing arbitrary memory may be able to locate them 599 and hijack control flow by modifying the stacks. 600 601config HAVE_ARCH_WITHIN_STACK_FRAMES 602 bool 603 help 604 An architecture should select this if it can walk the kernel stack 605 frames to determine if an object is part of either the arguments 606 or local variables (i.e. that it excludes saved return addresses, 607 and similar) by implementing an inline arch_within_stack_frames(), 608 which is used by CONFIG_HARDENED_USERCOPY. 609 610config HAVE_CONTEXT_TRACKING 611 bool 612 help 613 Provide kernel/user boundaries probes necessary for subsystems 614 that need it, such as userspace RCU extended quiescent state. 615 Syscalls need to be wrapped inside user_exit()-user_enter(), either 616 optimized behind static key or through the slow path using TIF_NOHZ 617 flag. Exceptions handlers must be wrapped as well. Irqs are already 618 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 619 handling on irq exit still need to be protected. 620 621config HAVE_TIF_NOHZ 622 bool 623 help 624 Arch relies on TIF_NOHZ and syscall slow path to implement context 625 tracking calls to user_enter()/user_exit(). 626 627config HAVE_VIRT_CPU_ACCOUNTING 628 bool 629 630config ARCH_HAS_SCALED_CPUTIME 631 bool 632 633config HAVE_VIRT_CPU_ACCOUNTING_GEN 634 bool 635 default y if 64BIT 636 help 637 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 638 Before enabling this option, arch code must be audited 639 to ensure there are no races in concurrent read/write of 640 cputime_t. For example, reading/writing 64-bit cputime_t on 641 some 32-bit arches may require multiple accesses, so proper 642 locking is needed to protect against concurrent accesses. 643 644 645config HAVE_IRQ_TIME_ACCOUNTING 646 bool 647 help 648 Archs need to ensure they use a high enough resolution clock to 649 support irq time accounting and then call enable_sched_clock_irqtime(). 650 651config HAVE_MOVE_PMD 652 bool 653 help 654 Archs that select this are able to move page tables at the PMD level. 655 656config HAVE_ARCH_TRANSPARENT_HUGEPAGE 657 bool 658 659config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 660 bool 661 662config HAVE_ARCH_HUGE_VMAP 663 bool 664 665config ARCH_WANT_HUGE_PMD_SHARE 666 bool 667 668config HAVE_ARCH_SOFT_DIRTY 669 bool 670 671config HAVE_MOD_ARCH_SPECIFIC 672 bool 673 help 674 The arch uses struct mod_arch_specific to store data. Many arches 675 just need a simple module loader without arch specific data - those 676 should not enable this. 677 678config MODULES_USE_ELF_RELA 679 bool 680 help 681 Modules only use ELF RELA relocations. Modules with ELF REL 682 relocations will give an error. 683 684config MODULES_USE_ELF_REL 685 bool 686 help 687 Modules only use ELF REL relocations. Modules with ELF RELA 688 relocations will give an error. 689 690config HAVE_IRQ_EXIT_ON_IRQ_STACK 691 bool 692 help 693 Architecture doesn't only execute the irq handler on the irq stack 694 but also irq_exit(). This way we can process softirqs on this irq 695 stack instead of switching to a new one when we call __do_softirq() 696 in the end of an hardirq. 697 This spares a stack switch and improves cache usage on softirq 698 processing. 699 700config PGTABLE_LEVELS 701 int 702 default 2 703 704config ARCH_HAS_ELF_RANDOMIZE 705 bool 706 help 707 An architecture supports choosing randomized locations for 708 stack, mmap, brk, and ET_DYN. Defined functions: 709 - arch_mmap_rnd() 710 - arch_randomize_brk() 711 712config HAVE_ARCH_MMAP_RND_BITS 713 bool 714 help 715 An arch should select this symbol if it supports setting a variable 716 number of bits for use in establishing the base address for mmap 717 allocations, has MMU enabled and provides values for both: 718 - ARCH_MMAP_RND_BITS_MIN 719 - ARCH_MMAP_RND_BITS_MAX 720 721config HAVE_EXIT_THREAD 722 bool 723 help 724 An architecture implements exit_thread. 725 726config ARCH_MMAP_RND_BITS_MIN 727 int 728 729config ARCH_MMAP_RND_BITS_MAX 730 int 731 732config ARCH_MMAP_RND_BITS_DEFAULT 733 int 734 735config ARCH_MMAP_RND_BITS 736 int "Number of bits to use for ASLR of mmap base address" if EXPERT 737 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 738 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 739 default ARCH_MMAP_RND_BITS_MIN 740 depends on HAVE_ARCH_MMAP_RND_BITS 741 help 742 This value can be used to select the number of bits to use to 743 determine the random offset to the base address of vma regions 744 resulting from mmap allocations. This value will be bounded 745 by the architecture's minimum and maximum supported values. 746 747 This value can be changed after boot using the 748 /proc/sys/vm/mmap_rnd_bits tunable 749 750config HAVE_ARCH_MMAP_RND_COMPAT_BITS 751 bool 752 help 753 An arch should select this symbol if it supports running applications 754 in compatibility mode, supports setting a variable number of bits for 755 use in establishing the base address for mmap allocations, has MMU 756 enabled and provides values for both: 757 - ARCH_MMAP_RND_COMPAT_BITS_MIN 758 - ARCH_MMAP_RND_COMPAT_BITS_MAX 759 760config ARCH_MMAP_RND_COMPAT_BITS_MIN 761 int 762 763config ARCH_MMAP_RND_COMPAT_BITS_MAX 764 int 765 766config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 767 int 768 769config ARCH_MMAP_RND_COMPAT_BITS 770 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 771 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 772 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 773 default ARCH_MMAP_RND_COMPAT_BITS_MIN 774 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 775 help 776 This value can be used to select the number of bits to use to 777 determine the random offset to the base address of vma regions 778 resulting from mmap allocations for compatible applications This 779 value will be bounded by the architecture's minimum and maximum 780 supported values. 781 782 This value can be changed after boot using the 783 /proc/sys/vm/mmap_rnd_compat_bits tunable 784 785config HAVE_ARCH_COMPAT_MMAP_BASES 786 bool 787 help 788 This allows 64bit applications to invoke 32-bit mmap() syscall 789 and vice-versa 32-bit applications to call 64-bit mmap(). 790 Required for applications doing different bitness syscalls. 791 792# This allows to use a set of generic functions to determine mmap base 793# address by giving priority to top-down scheme only if the process 794# is not in legacy mode (compat task, unlimited stack size or 795# sysctl_legacy_va_layout). 796# Architecture that selects this option can provide its own version of: 797# - STACK_RND_MASK 798config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 799 bool 800 depends on MMU 801 select ARCH_HAS_ELF_RANDOMIZE 802 803config HAVE_STACK_VALIDATION 804 bool 805 help 806 Architecture supports the 'objtool check' host tool command, which 807 performs compile-time stack metadata validation. 808 809config HAVE_RELIABLE_STACKTRACE 810 bool 811 help 812 Architecture has either save_stack_trace_tsk_reliable() or 813 arch_stack_walk_reliable() function which only returns a stack trace 814 if it can guarantee the trace is reliable. 815 816config HAVE_ARCH_HASH 817 bool 818 default n 819 help 820 If this is set, the architecture provides an <asm/hash.h> 821 file which provides platform-specific implementations of some 822 functions in <linux/hash.h> or fs/namei.c. 823 824config HAVE_ARCH_NVRAM_OPS 825 bool 826 827config ISA_BUS_API 828 def_bool ISA 829 830# 831# ABI hall of shame 832# 833config CLONE_BACKWARDS 834 bool 835 help 836 Architecture has tls passed as the 4th argument of clone(2), 837 not the 5th one. 838 839config CLONE_BACKWARDS2 840 bool 841 help 842 Architecture has the first two arguments of clone(2) swapped. 843 844config CLONE_BACKWARDS3 845 bool 846 help 847 Architecture has tls passed as the 3rd argument of clone(2), 848 not the 5th one. 849 850config ODD_RT_SIGACTION 851 bool 852 help 853 Architecture has unusual rt_sigaction(2) arguments 854 855config OLD_SIGSUSPEND 856 bool 857 help 858 Architecture has old sigsuspend(2) syscall, of one-argument variety 859 860config OLD_SIGSUSPEND3 861 bool 862 help 863 Even weirder antique ABI - three-argument sigsuspend(2) 864 865config OLD_SIGACTION 866 bool 867 help 868 Architecture has old sigaction(2) syscall. Nope, not the same 869 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 870 but fairly different variant of sigaction(2), thanks to OSF/1 871 compatibility... 872 873config COMPAT_OLD_SIGACTION 874 bool 875 876config COMPAT_32BIT_TIME 877 bool "Provide system calls for 32-bit time_t" 878 default !64BIT || COMPAT 879 help 880 This enables 32 bit time_t support in addition to 64 bit time_t support. 881 This is relevant on all 32-bit architectures, and 64-bit architectures 882 as part of compat syscall handling. 883 884config ARCH_NO_PREEMPT 885 bool 886 887config ARCH_SUPPORTS_RT 888 bool 889 890config CPU_NO_EFFICIENT_FFS 891 def_bool n 892 893config HAVE_ARCH_VMAP_STACK 894 def_bool n 895 help 896 An arch should select this symbol if it can support kernel stacks 897 in vmalloc space. This means: 898 899 - vmalloc space must be large enough to hold many kernel stacks. 900 This may rule out many 32-bit architectures. 901 902 - Stacks in vmalloc space need to work reliably. For example, if 903 vmap page tables are created on demand, either this mechanism 904 needs to work while the stack points to a virtual address with 905 unpopulated page tables or arch code (switch_to() and switch_mm(), 906 most likely) needs to ensure that the stack's page table entries 907 are populated before running on a possibly unpopulated stack. 908 909 - If the stack overflows into a guard page, something reasonable 910 should happen. The definition of "reasonable" is flexible, but 911 instantly rebooting without logging anything would be unfriendly. 912 913config VMAP_STACK 914 default y 915 bool "Use a virtually-mapped stack" 916 depends on HAVE_ARCH_VMAP_STACK 917 depends on !KASAN || KASAN_VMALLOC 918 help 919 Enable this if you want the use virtually-mapped kernel stacks 920 with guard pages. This causes kernel stack overflows to be 921 caught immediately rather than causing difficult-to-diagnose 922 corruption. 923 924 To use this with KASAN, the architecture must support backing 925 virtual mappings with real shadow memory, and KASAN_VMALLOC must 926 be enabled. 927 928config ARCH_OPTIONAL_KERNEL_RWX 929 def_bool n 930 931config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 932 def_bool n 933 934config ARCH_HAS_STRICT_KERNEL_RWX 935 def_bool n 936 937config STRICT_KERNEL_RWX 938 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 939 depends on ARCH_HAS_STRICT_KERNEL_RWX 940 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 941 help 942 If this is set, kernel text and rodata memory will be made read-only, 943 and non-text memory will be made non-executable. This provides 944 protection against certain security exploits (e.g. executing the heap 945 or modifying text) 946 947 These features are considered standard security practice these days. 948 You should say Y here in almost all cases. 949 950config ARCH_HAS_STRICT_MODULE_RWX 951 def_bool n 952 953config STRICT_MODULE_RWX 954 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 955 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 956 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 957 help 958 If this is set, module text and rodata memory will be made read-only, 959 and non-text memory will be made non-executable. This provides 960 protection against certain security exploits (e.g. writing to text) 961 962# select if the architecture provides an asm/dma-direct.h header 963config ARCH_HAS_PHYS_TO_DMA 964 bool 965 966config HAVE_ARCH_COMPILER_H 967 bool 968 help 969 An architecture can select this if it provides an 970 asm/compiler.h header that should be included after 971 linux/compiler-*.h in order to override macro definitions that those 972 headers generally provide. 973 974config HAVE_ARCH_PREL32_RELOCATIONS 975 bool 976 help 977 May be selected by an architecture if it supports place-relative 978 32-bit relocations, both in the toolchain and in the module loader, 979 in which case relative references can be used in special sections 980 for PCI fixup, initcalls etc which are only half the size on 64 bit 981 architectures, and don't require runtime relocation on relocatable 982 kernels. 983 984config ARCH_USE_MEMREMAP_PROT 985 bool 986 987config LOCK_EVENT_COUNTS 988 bool "Locking event counts collection" 989 depends on DEBUG_FS 990 help 991 Enable light-weight counting of various locking related events 992 in the system with minimal performance impact. This reduces 993 the chance of application behavior change because of timing 994 differences. The counts are reported via debugfs. 995 996# Select if the architecture has support for applying RELR relocations. 997config ARCH_HAS_RELR 998 bool 999 1000config RELR 1001 bool "Use RELR relocation packing" 1002 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1003 default y 1004 help 1005 Store the kernel's dynamic relocations in the RELR relocation packing 1006 format. Requires a compatible linker (LLD supports this feature), as 1007 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1008 are compatible). 1009 1010config ARCH_HAS_MEM_ENCRYPT 1011 bool 1012 1013config HAVE_SPARSE_SYSCALL_NR 1014 bool 1015 help 1016 An architecture should select this if its syscall numbering is sparse 1017 to save space. For example, MIPS architecture has a syscall array with 1018 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1019 related optimizations for a given architecture. 1020 1021config ARCH_HAS_VDSO_DATA 1022 bool 1023 1024config HAVE_STATIC_CALL 1025 bool 1026 1027config HAVE_STATIC_CALL_INLINE 1028 bool 1029 depends on HAVE_STATIC_CALL 1030 1031source "kernel/gcov/Kconfig" 1032 1033source "scripts/gcc-plugins/Kconfig" 1034 1035endmenu 1036