arch/Kconfig

   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 HOTPLUG_SMT
  28         bool
  29
  30 config OPROFILE
  31         tristate "OProfile system profiling"
  32         depends on PROFILING
  33         depends on HAVE_OPROFILE
  34         select RING_BUFFER
  35         select RING_BUFFER_ALLOW_SWAP
  36         help
  37           OProfile is a profiling system capable of profiling the
  38           whole system, include the kernel, kernel modules, libraries,
  39           and applications.
  40
  41           If unsure, say N.
  42
  43 config OPROFILE_EVENT_MULTIPLEX
  44         bool "OProfile multiplexing support (EXPERIMENTAL)"
  45         default n
  46         depends on OPROFILE && X86
  47         help
  48           The number of hardware counters is limited. The multiplexing
  49           feature enables OProfile to gather more events than counters
  50           are provided by the hardware. This is realized by switching
  51           between events at a user specified time interval.
  52
  53           If unsure, say N.
  54
  55 config HAVE_OPROFILE
  56         bool
  57
  58 config OPROFILE_NMI_TIMER
  59         def_bool y
  60         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  61
  62 config KPROBES
  63         bool "Kprobes"
  64         depends on MODULES
  65         depends on HAVE_KPROBES
  66         select KALLSYMS
  67         help
  68           Kprobes allows you to trap at almost any kernel address and
  69           execute a callback function.  register_kprobe() establishes
  70           a probepoint and specifies the callback.  Kprobes is useful
  71           for kernel debugging, non-intrusive instrumentation and testing.
  72           If in doubt, say "N".
  73
  74 config JUMP_LABEL
  75         bool "Optimize very unlikely/likely branches"
  76         depends on HAVE_ARCH_JUMP_LABEL
  77         depends on CC_HAS_ASM_GOTO
  78         help
  79          This option enables a transparent branch optimization that
  80          makes certain almost-always-true or almost-always-false branch
  81          conditions even cheaper to execute within the kernel.
  82
  83          Certain performance-sensitive kernel code, such as trace points,
  84          scheduler functionality, networking code and KVM have such
  85          branches and include support for this optimization technique.
  86
  87          If it is detected that the compiler has support for "asm goto",
  88          the kernel will compile such branches with just a nop
  89          instruction. When the condition flag is toggled to true, the
  90          nop will be converted to a jump instruction to execute the
  91          conditional block of instructions.
  92
  93          This technique lowers overhead and stress on the branch prediction
  94          of the processor and generally makes the kernel faster. The update
  95          of the condition is slower, but those are always very rare.
  96
  97          ( On 32-bit x86, the necessary options added to the compiler
  98            flags may increase the size of the kernel slightly. )
  99
 100 config STATIC_KEYS_SELFTEST
 101         bool "Static key selftest"
 102         depends on JUMP_LABEL
 103         help
 104           Boot time self-test of the branch patching code.
 105
 106 config OPTPROBES
 107         def_bool y
 108         depends on KPROBES && HAVE_OPTPROBES
 109         select TASKS_RCU if PREEMPTION
 110
 111 config KPROBES_ON_FTRACE
 112         def_bool y
 113         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 114         depends on DYNAMIC_FTRACE_WITH_REGS
 115         help
 116          If function tracer is enabled and the arch supports full
 117          passing of pt_regs to function tracing, then kprobes can
 118          optimize on top of function tracing.
 119
 120 config UPROBES
 121         def_bool n
 122         depends on ARCH_SUPPORTS_UPROBES
 123         help
 124           Uprobes is the user-space counterpart to kprobes: they
 125           enable instrumentation applications (such as 'perf probe')
 126           to establish unintrusive probes in user-space binaries and
 127           libraries, by executing handler functions when the probes
 128           are hit by user-space applications.
 129
 130           ( These probes come in the form of single-byte breakpoints,
 131             managed by the kernel and kept transparent to the probed
 132             application. )
 133
 134 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 135         bool
 136         help
 137           Some architectures are unable to perform unaligned accesses
 138           without the use of get_unaligned/put_unaligned. Others are
 139           unable to perform such accesses efficiently (e.g. trap on
 140           unaligned access and require fixing it up in the exception
 141           handler.)
 142
 143           This symbol should be selected by an architecture if it can
 144           perform unaligned accesses efficiently to allow different
 145           code paths to be selected for these cases. Some network
 146           drivers, for example, could opt to not fix up alignment
 147           problems with received packets if doing so would not help
 148           much.
 149
 150           See Documentation/unaligned-memory-access.txt for more
 151           information on the topic of unaligned memory accesses.
 152
 153 config ARCH_USE_BUILTIN_BSWAP
 154         bool
 155         help
 156          Modern versions of GCC (since 4.4) have builtin functions
 157          for handling byte-swapping. Using these, instead of the old
 158          inline assembler that the architecture code provides in the
 159          __arch_bswapXX() macros, allows the compiler to see what's
 160          happening and offers more opportunity for optimisation. In
 161          particular, the compiler will be able to combine the byteswap
 162          with a nearby load or store and use load-and-swap or
 163          store-and-swap instructions if the architecture has them. It
 164          should almost *never* result in code which is worse than the
 165          hand-coded assembler in <asm/swab.h>.  But just in case it
 166          does, the use of the builtins is optional.
 167
 168          Any architecture with load-and-swap or store-and-swap
 169          instructions should set this. And it shouldn't hurt to set it
 170          on architectures that don't have such instructions.
 171
 172 config KRETPROBES
 173         def_bool y
 174         depends on KPROBES && HAVE_KRETPROBES
 175
 176 config USER_RETURN_NOTIFIER
 177         bool
 178         depends on HAVE_USER_RETURN_NOTIFIER
 179         help
 180           Provide a kernel-internal notification when a cpu is about to
 181           switch to user mode.
 182
 183 config HAVE_IOREMAP_PROT
 184         bool
 185
 186 config HAVE_KPROBES
 187         bool
 188
 189 config HAVE_KRETPROBES
 190         bool
 191
 192 config HAVE_OPTPROBES
 193         bool
 194
 195 config HAVE_KPROBES_ON_FTRACE
 196         bool
 197
 198 config HAVE_FUNCTION_ERROR_INJECTION
 199         bool
 200
 201 config HAVE_NMI
 202         bool
 203
 204 #
 205 # An arch should select this if it provides all these things:
 206 #
 207 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 208 #       arch_has_single_step()  if there is hardware single-step support
 209 #       arch_has_block_step()   if there is hardware block-step support
 210 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 211 #       linux/regset.h          user_regset interfaces
 212 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 213 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 214 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 215 #       signal delivery         calls tracehook_signal_handler()
 216 #
 217 config HAVE_ARCH_TRACEHOOK
 218         bool
 219
 220 config HAVE_DMA_CONTIGUOUS
 221         bool
 222
 223 config GENERIC_SMP_IDLE_THREAD
 224         bool
 225
 226 config GENERIC_IDLE_POLL_SETUP
 227         bool
 228
 229 config ARCH_HAS_FORTIFY_SOURCE
 230         bool
 231         help
 232           An architecture should select this when it can successfully
 233           build and run with CONFIG_FORTIFY_SOURCE.
 234
 235 #
 236 # Select if the arch provides a historic keepinit alias for the retain_initrd
 237 # command line option
 238 #
 239 config ARCH_HAS_KEEPINITRD
 240         bool
 241
 242 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 243 config ARCH_HAS_SET_MEMORY
 244         bool
 245
 246 # Select if arch has all set_direct_map_invalid/default() functions
 247 config ARCH_HAS_SET_DIRECT_MAP
 248         bool
 249
 250 #
 251 # Select if the architecture provides the arch_dma_set_uncached symbol to
 252 # either provide an uncached segement alias for a DMA allocation, or
 253 # to remap the page tables in place.
 254 #
 255 config ARCH_HAS_DMA_SET_UNCACHED
 256         bool
 257
 258 #
 259 # Select if the architectures provides the arch_dma_clear_uncached symbol
 260 # to undo an in-place page table remap for uncached access.
 261 #
 262 config ARCH_HAS_DMA_CLEAR_UNCACHED
 263         bool
 264
 265 # Select if arch init_task must go in the __init_task_data section
 266 config ARCH_TASK_STRUCT_ON_STACK
 267         bool
 268
 269 # Select if arch has its private alloc_task_struct() function
 270 config ARCH_TASK_STRUCT_ALLOCATOR
 271         bool
 272
 273 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 274         bool
 275         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 276         help
 277           An architecture should select this to provide hardened usercopy
 278           knowledge about what region of the thread_struct should be
 279           whitelisted for copying to userspace. Normally this is only the
 280           FPU registers. Specifically, arch_thread_struct_whitelist()
 281           should be implemented. Without this, the entire thread_struct
 282           field in task_struct will be left whitelisted.
 283
 284 # Select if arch has its private alloc_thread_stack() function
 285 config ARCH_THREAD_STACK_ALLOCATOR
 286         bool
 287
 288 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 289 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 290         bool
 291
 292 config ARCH_32BIT_OFF_T
 293         bool
 294         depends on !64BIT
 295         help
 296           All new 32-bit architectures should have 64-bit off_t type on
 297           userspace side which corresponds to the loff_t kernel type. This
 298           is the requirement for modern ABIs. Some existing architectures
 299           still support 32-bit off_t. This option is enabled for all such
 300           architectures explicitly.
 301
 302 config HAVE_ASM_MODVERSIONS
 303         bool
 304         help
 305           This symbol should be selected by an architecure if it provides
 306           <asm/asm-prototypes.h> to support the module versioning for symbols
 307           exported from assembly code.
 308
 309 config HAVE_REGS_AND_STACK_ACCESS_API
 310         bool
 311         help
 312           This symbol should be selected by an architecure if it supports
 313           the API needed to access registers and stack entries from pt_regs,
 314           declared in asm/ptrace.h
 315           For example the kprobes-based event tracer needs this API.
 316
 317 config HAVE_RSEQ
 318         bool
 319         depends on HAVE_REGS_AND_STACK_ACCESS_API
 320         help
 321           This symbol should be selected by an architecture if it
 322           supports an implementation of restartable sequences.
 323
 324 config HAVE_FUNCTION_ARG_ACCESS_API
 325         bool
 326         help
 327           This symbol should be selected by an architecure if it supports
 328           the API needed to access function arguments from pt_regs,
 329           declared in asm/ptrace.h
 330
 331 config HAVE_CLK
 332         bool
 333         help
 334           The <linux/clk.h> calls support software clock gating and
 335           thus are a key power management tool on many systems.
 336
 337 config HAVE_HW_BREAKPOINT
 338         bool
 339         depends on PERF_EVENTS
 340
 341 config HAVE_MIXED_BREAKPOINTS_REGS
 342         bool
 343         depends on HAVE_HW_BREAKPOINT
 344         help
 345           Depending on the arch implementation of hardware breakpoints,
 346           some of them have separate registers for data and instruction
 347           breakpoints addresses, others have mixed registers to store
 348           them but define the access type in a control register.
 349           Select this option if your arch implements breakpoints under the
 350           latter fashion.
 351
 352 config HAVE_USER_RETURN_NOTIFIER
 353         bool
 354
 355 config HAVE_PERF_EVENTS_NMI
 356         bool
 357         help
 358           System hardware can generate an NMI using the perf event
 359           subsystem.  Also has support for calculating CPU cycle events
 360           to determine how many clock cycles in a given period.
 361
 362 config HAVE_HARDLOCKUP_DETECTOR_PERF
 363         bool
 364         depends on HAVE_PERF_EVENTS_NMI
 365         help
 366           The arch chooses to use the generic perf-NMI-based hardlockup
 367           detector. Must define HAVE_PERF_EVENTS_NMI.
 368
 369 config HAVE_NMI_WATCHDOG
 370         depends on HAVE_NMI
 371         bool
 372         help
 373           The arch provides a low level NMI watchdog. It provides
 374           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 375
 376 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 377         bool
 378         select HAVE_NMI_WATCHDOG
 379         help
 380           The arch chooses to provide its own hardlockup detector, which is
 381           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 382           interfaces and parameters provided by hardlockup detector subsystem.
 383
 384 config HAVE_PERF_REGS
 385         bool
 386         help
 387           Support selective register dumps for perf events. This includes
 388           bit-mapping of each registers and a unique architecture id.
 389
 390 config HAVE_PERF_USER_STACK_DUMP
 391         bool
 392         help
 393           Support user stack dumps for perf event samples. This needs
 394           access to the user stack pointer which is not unified across
 395           architectures.
 396
 397 config HAVE_ARCH_JUMP_LABEL
 398         bool
 399
 400 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 401         bool
 402
 403 config MMU_GATHER_TABLE_FREE
 404         bool
 405
 406 config MMU_GATHER_RCU_TABLE_FREE
 407         bool
 408         select MMU_GATHER_TABLE_FREE
 409
 410 config MMU_GATHER_PAGE_SIZE
 411         bool
 412
 413 config MMU_GATHER_NO_RANGE
 414         bool
 415
 416 config MMU_GATHER_NO_GATHER
 417         bool
 418         depends on MMU_GATHER_TABLE_FREE
 419
 420 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 421         bool
 422
 423 config HAVE_ALIGNED_STRUCT_PAGE
 424         bool
 425         help
 426           This makes sure that struct pages are double word aligned and that
 427           e.g. the SLUB allocator can perform double word atomic operations
 428           on a struct page for better performance. However selecting this
 429           might increase the size of a struct page by a word.
 430
 431 config HAVE_CMPXCHG_LOCAL
 432         bool
 433
 434 config HAVE_CMPXCHG_DOUBLE
 435         bool
 436
 437 config ARCH_WEAK_RELEASE_ACQUIRE
 438         bool
 439
 440 config ARCH_WANT_IPC_PARSE_VERSION
 441         bool
 442
 443 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 444         bool
 445
 446 config ARCH_WANT_OLD_COMPAT_IPC
 447         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 448         bool
 449
 450 config HAVE_ARCH_SECCOMP_FILTER
 451         bool
 452         help
 453           An arch should select this symbol if it provides all of these things:
 454           - syscall_get_arch()
 455           - syscall_get_arguments()
 456           - syscall_rollback()
 457           - syscall_set_return_value()
 458           - SIGSYS siginfo_t support
 459           - secure_computing is called from a ptrace_event()-safe context
 460           - secure_computing return value is checked and a return value of -1
 461             results in the system call being skipped immediately.
 462           - seccomp syscall wired up
 463
 464 config SECCOMP_FILTER
 465         def_bool y
 466         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 467         help
 468           Enable tasks to build secure computing environments defined
 469           in terms of Berkeley Packet Filter programs which implement
 470           task-defined system call filtering polices.
 471
 472           See Documentation/userspace-api/seccomp_filter.rst for details.
 473
 474 config HAVE_ARCH_STACKLEAK
 475         bool
 476         help
 477           An architecture should select this if it has the code which
 478           fills the used part of the kernel stack with the STACKLEAK_POISON
 479           value before returning from system calls.
 480
 481 config HAVE_STACKPROTECTOR
 482         bool
 483         help
 484           An arch should select this symbol if:
 485           - it has implemented a stack canary (e.g. __stack_chk_guard)
 486
 487 config CC_HAS_STACKPROTECTOR_NONE
 488         def_bool $(cc-option,-fno-stack-protector)
 489
 490 config STACKPROTECTOR
 491         bool "Stack Protector buffer overflow detection"
 492         depends on HAVE_STACKPROTECTOR
 493         depends on $(cc-option,-fstack-protector)
 494         default y
 495         help
 496           This option turns on the "stack-protector" GCC feature. This
 497           feature puts, at the beginning of functions, a canary value on
 498           the stack just before the return address, and validates
 499           the value just before actually returning.  Stack based buffer
 500           overflows (that need to overwrite this return address) now also
 501           overwrite the canary, which gets detected and the attack is then
 502           neutralized via a kernel panic.
 503
 504           Functions will have the stack-protector canary logic added if they
 505           have an 8-byte or larger character array on the stack.
 506
 507           This feature requires gcc version 4.2 or above, or a distribution
 508           gcc with the feature backported ("-fstack-protector").
 509
 510           On an x86 "defconfig" build, this feature adds canary checks to
 511           about 3% of all kernel functions, which increases kernel code size
 512           by about 0.3%.
 513
 514 config STACKPROTECTOR_STRONG
 515         bool "Strong Stack Protector"
 516         depends on STACKPROTECTOR
 517         depends on $(cc-option,-fstack-protector-strong)
 518         default y
 519         help
 520           Functions will have the stack-protector canary logic added in any
 521           of the following conditions:
 522
 523           - local variable's address used as part of the right hand side of an
 524             assignment or function argument
 525           - local variable is an array (or union containing an array),
 526             regardless of array type or length
 527           - uses register local variables
 528
 529           This feature requires gcc version 4.9 or above, or a distribution
 530           gcc with the feature backported ("-fstack-protector-strong").
 531
 532           On an x86 "defconfig" build, this feature adds canary checks to
 533           about 20% of all kernel functions, which increases the kernel code
 534           size by about 2%.
 535
 536 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 537         bool
 538         help
 539           An architecture should select this if it supports Clang's Shadow
 540           Call Stack and implements runtime support for shadow stack
 541           switching.
 542
 543 config SHADOW_CALL_STACK
 544         bool "Clang Shadow Call Stack"
 545         depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
 546         depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 547         help
 548           This option enables Clang's Shadow Call Stack, which uses a
 549           shadow stack to protect function return addresses from being
 550           overwritten by an attacker. More information can be found in
 551           Clang's documentation:
 552
 553             https://clang.llvm.org/docs/ShadowCallStack.html
 554
 555           Note that security guarantees in the kernel differ from the
 556           ones documented for user space. The kernel must store addresses
 557           of shadow stacks in memory, which means an attacker capable of
 558           reading and writing arbitrary memory may be able to locate them
 559           and hijack control flow by modifying the stacks.
 560
 561 config HAVE_ARCH_WITHIN_STACK_FRAMES
 562         bool
 563         help
 564           An architecture should select this if it can walk the kernel stack
 565           frames to determine if an object is part of either the arguments
 566           or local variables (i.e. that it excludes saved return addresses,
 567           and similar) by implementing an inline arch_within_stack_frames(),
 568           which is used by CONFIG_HARDENED_USERCOPY.
 569
 570 config HAVE_CONTEXT_TRACKING
 571         bool
 572         help
 573           Provide kernel/user boundaries probes necessary for subsystems
 574           that need it, such as userspace RCU extended quiescent state.
 575           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 576           optimized behind static key or through the slow path using TIF_NOHZ
 577           flag. Exceptions handlers must be wrapped as well. Irqs are already
 578           protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
 579           handling on irq exit still need to be protected.
 580
 581 config HAVE_TIF_NOHZ
 582         bool
 583         help
 584           Arch relies on TIF_NOHZ and syscall slow path to implement context
 585           tracking calls to user_enter()/user_exit().
 586
 587 config HAVE_VIRT_CPU_ACCOUNTING
 588         bool
 589
 590 config ARCH_HAS_SCALED_CPUTIME
 591         bool
 592
 593 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 594         bool
 595         default y if 64BIT
 596         help
 597           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 598           Before enabling this option, arch code must be audited
 599           to ensure there are no races in concurrent read/write of
 600           cputime_t. For example, reading/writing 64-bit cputime_t on
 601           some 32-bit arches may require multiple accesses, so proper
 602           locking is needed to protect against concurrent accesses.
 603
 604
 605 config HAVE_IRQ_TIME_ACCOUNTING
 606         bool
 607         help
 608           Archs need to ensure they use a high enough resolution clock to
 609           support irq time accounting and then call enable_sched_clock_irqtime().
 610
 611 config HAVE_MOVE_PMD
 612         bool
 613         help
 614           Archs that select this are able to move page tables at the PMD level.
 615
 616 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 617         bool
 618
 619 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 620         bool
 621
 622 config HAVE_ARCH_HUGE_VMAP
 623         bool
 624
 625 config ARCH_WANT_HUGE_PMD_SHARE
 626         bool
 627
 628 config HAVE_ARCH_SOFT_DIRTY
 629         bool
 630
 631 config HAVE_MOD_ARCH_SPECIFIC
 632         bool
 633         help
 634           The arch uses struct mod_arch_specific to store data.  Many arches
 635           just need a simple module loader without arch specific data - those
 636           should not enable this.
 637
 638 config MODULES_USE_ELF_RELA
 639         bool
 640         help
 641           Modules only use ELF RELA relocations.  Modules with ELF REL
 642           relocations will give an error.
 643
 644 config MODULES_USE_ELF_REL
 645         bool
 646         help
 647           Modules only use ELF REL relocations.  Modules with ELF RELA
 648           relocations will give an error.
 649
 650 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 651         bool
 652         help
 653           Architecture doesn't only execute the irq handler on the irq stack
 654           but also irq_exit(). This way we can process softirqs on this irq
 655           stack instead of switching to a new one when we call __do_softirq()
 656           in the end of an hardirq.
 657           This spares a stack switch and improves cache usage on softirq
 658           processing.
 659
 660 config PGTABLE_LEVELS
 661         int
 662         default 2
 663
 664 config ARCH_HAS_ELF_RANDOMIZE
 665         bool
 666         help
 667           An architecture supports choosing randomized locations for
 668           stack, mmap, brk, and ET_DYN. Defined functions:
 669           - arch_mmap_rnd()
 670           - arch_randomize_brk()
 671
 672 config HAVE_ARCH_MMAP_RND_BITS
 673         bool
 674         help
 675           An arch should select this symbol if it supports setting a variable
 676           number of bits for use in establishing the base address for mmap
 677           allocations, has MMU enabled and provides values for both:
 678           - ARCH_MMAP_RND_BITS_MIN
 679           - ARCH_MMAP_RND_BITS_MAX
 680
 681 config HAVE_EXIT_THREAD
 682         bool
 683         help
 684           An architecture implements exit_thread.
 685
 686 config ARCH_MMAP_RND_BITS_MIN
 687         int
 688
 689 config ARCH_MMAP_RND_BITS_MAX
 690         int
 691
 692 config ARCH_MMAP_RND_BITS_DEFAULT
 693         int
 694
 695 config ARCH_MMAP_RND_BITS
 696         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 697         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 698         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 699         default ARCH_MMAP_RND_BITS_MIN
 700         depends on HAVE_ARCH_MMAP_RND_BITS
 701         help
 702           This value can be used to select the number of bits to use to
 703           determine the random offset to the base address of vma regions
 704           resulting from mmap allocations. This value will be bounded
 705           by the architecture's minimum and maximum supported values.
 706
 707           This value can be changed after boot using the
 708           /proc/sys/vm/mmap_rnd_bits tunable
 709
 710 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 711         bool
 712         help
 713           An arch should select this symbol if it supports running applications
 714           in compatibility mode, supports setting a variable number of bits for
 715           use in establishing the base address for mmap allocations, has MMU
 716           enabled and provides values for both:
 717           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 718           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 719
 720 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 721         int
 722
 723 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 724         int
 725
 726 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 727         int
 728
 729 config ARCH_MMAP_RND_COMPAT_BITS
 730         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 731         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 732         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 733         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 734         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 735         help
 736           This value can be used to select the number of bits to use to
 737           determine the random offset to the base address of vma regions
 738           resulting from mmap allocations for compatible applications This
 739           value will be bounded by the architecture's minimum and maximum
 740           supported values.
 741
 742           This value can be changed after boot using the
 743           /proc/sys/vm/mmap_rnd_compat_bits tunable
 744
 745 config HAVE_ARCH_COMPAT_MMAP_BASES
 746         bool
 747         help
 748           This allows 64bit applications to invoke 32-bit mmap() syscall
 749           and vice-versa 32-bit applications to call 64-bit mmap().
 750           Required for applications doing different bitness syscalls.
 751
 752 # This allows to use a set of generic functions to determine mmap base
 753 # address by giving priority to top-down scheme only if the process
 754 # is not in legacy mode (compat task, unlimited stack size or
 755 # sysctl_legacy_va_layout).
 756 # Architecture that selects this option can provide its own version of:
 757 # - STACK_RND_MASK
 758 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 759         bool
 760         depends on MMU
 761         select ARCH_HAS_ELF_RANDOMIZE
 762
 763 config HAVE_COPY_THREAD_TLS
 764         bool
 765         help
 766           Architecture provides copy_thread_tls to accept tls argument via
 767           normal C parameter passing, rather than extracting the syscall
 768           argument from pt_regs.
 769
 770 config HAVE_STACK_VALIDATION
 771         bool
 772         help
 773           Architecture supports the 'objtool check' host tool command, which
 774           performs compile-time stack metadata validation.
 775
 776 config HAVE_RELIABLE_STACKTRACE
 777         bool
 778         help
 779           Architecture has either save_stack_trace_tsk_reliable() or
 780           arch_stack_walk_reliable() function which only returns a stack trace
 781           if it can guarantee the trace is reliable.
 782
 783 config HAVE_ARCH_HASH
 784         bool
 785         default n
 786         help
 787           If this is set, the architecture provides an <asm/hash.h>
 788           file which provides platform-specific implementations of some
 789           functions in <linux/hash.h> or fs/namei.c.
 790
 791 config HAVE_ARCH_NVRAM_OPS
 792         bool
 793
 794 config ISA_BUS_API
 795         def_bool ISA
 796
 797 #
 798 # ABI hall of shame
 799 #
 800 config CLONE_BACKWARDS
 801         bool
 802         help
 803           Architecture has tls passed as the 4th argument of clone(2),
 804           not the 5th one.
 805
 806 config CLONE_BACKWARDS2
 807         bool
 808         help
 809           Architecture has the first two arguments of clone(2) swapped.
 810
 811 config CLONE_BACKWARDS3
 812         bool
 813         help
 814           Architecture has tls passed as the 3rd argument of clone(2),
 815           not the 5th one.
 816
 817 config ODD_RT_SIGACTION
 818         bool
 819         help
 820           Architecture has unusual rt_sigaction(2) arguments
 821
 822 config OLD_SIGSUSPEND
 823         bool
 824         help
 825           Architecture has old sigsuspend(2) syscall, of one-argument variety
 826
 827 config OLD_SIGSUSPEND3
 828         bool
 829         help
 830           Even weirder antique ABI - three-argument sigsuspend(2)
 831
 832 config OLD_SIGACTION
 833         bool
 834         help
 835           Architecture has old sigaction(2) syscall.  Nope, not the same
 836           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 837           but fairly different variant of sigaction(2), thanks to OSF/1
 838           compatibility...
 839
 840 config COMPAT_OLD_SIGACTION
 841         bool
 842
 843 config COMPAT_32BIT_TIME
 844         bool "Provide system calls for 32-bit time_t"
 845         default !64BIT || COMPAT
 846         help
 847           This enables 32 bit time_t support in addition to 64 bit time_t support.
 848           This is relevant on all 32-bit architectures, and 64-bit architectures
 849           as part of compat syscall handling.
 850
 851 config ARCH_NO_PREEMPT
 852         bool
 853
 854 config ARCH_SUPPORTS_RT
 855         bool
 856
 857 config CPU_NO_EFFICIENT_FFS
 858         def_bool n
 859
 860 config HAVE_ARCH_VMAP_STACK
 861         def_bool n
 862         help
 863           An arch should select this symbol if it can support kernel stacks
 864           in vmalloc space.  This means:
 865
 866           - vmalloc space must be large enough to hold many kernel stacks.
 867             This may rule out many 32-bit architectures.
 868
 869           - Stacks in vmalloc space need to work reliably.  For example, if
 870             vmap page tables are created on demand, either this mechanism
 871             needs to work while the stack points to a virtual address with
 872             unpopulated page tables or arch code (switch_to() and switch_mm(),
 873             most likely) needs to ensure that the stack's page table entries
 874             are populated before running on a possibly unpopulated stack.
 875
 876           - If the stack overflows into a guard page, something reasonable
 877             should happen.  The definition of "reasonable" is flexible, but
 878             instantly rebooting without logging anything would be unfriendly.
 879
 880 config VMAP_STACK
 881         default y
 882         bool "Use a virtually-mapped stack"
 883         depends on HAVE_ARCH_VMAP_STACK
 884         depends on !KASAN || KASAN_VMALLOC
 885         ---help---
 886           Enable this if you want the use virtually-mapped kernel stacks
 887           with guard pages.  This causes kernel stack overflows to be
 888           caught immediately rather than causing difficult-to-diagnose
 889           corruption.
 890
 891           To use this with KASAN, the architecture must support backing
 892           virtual mappings with real shadow memory, and KASAN_VMALLOC must
 893           be enabled.
 894
 895 config ARCH_OPTIONAL_KERNEL_RWX
 896         def_bool n
 897
 898 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 899         def_bool n
 900
 901 config ARCH_HAS_STRICT_KERNEL_RWX
 902         def_bool n
 903
 904 config STRICT_KERNEL_RWX
 905         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 906         depends on ARCH_HAS_STRICT_KERNEL_RWX
 907         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 908         help
 909           If this is set, kernel text and rodata memory will be made read-only,
 910           and non-text memory will be made non-executable. This provides
 911           protection against certain security exploits (e.g. executing the heap
 912           or modifying text)
 913
 914           These features are considered standard security practice these days.
 915           You should say Y here in almost all cases.
 916
 917 config ARCH_HAS_STRICT_MODULE_RWX
 918         def_bool n
 919
 920 config STRICT_MODULE_RWX
 921         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 922         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 923         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 924         help
 925           If this is set, module text and rodata memory will be made read-only,
 926           and non-text memory will be made non-executable. This provides
 927           protection against certain security exploits (e.g. writing to text)
 928
 929 # select if the architecture provides an asm/dma-direct.h header
 930 config ARCH_HAS_PHYS_TO_DMA
 931         bool
 932
 933 config HAVE_ARCH_COMPILER_H
 934         bool
 935         help
 936           An architecture can select this if it provides an
 937           asm/compiler.h header that should be included after
 938           linux/compiler-*.h in order to override macro definitions that those
 939           headers generally provide.
 940
 941 config HAVE_ARCH_PREL32_RELOCATIONS
 942         bool
 943         help
 944           May be selected by an architecture if it supports place-relative
 945           32-bit relocations, both in the toolchain and in the module loader,
 946           in which case relative references can be used in special sections
 947           for PCI fixup, initcalls etc which are only half the size on 64 bit
 948           architectures, and don't require runtime relocation on relocatable
 949           kernels.
 950
 951 config ARCH_USE_MEMREMAP_PROT
 952         bool
 953
 954 config LOCK_EVENT_COUNTS
 955         bool "Locking event counts collection"
 956         depends on DEBUG_FS
 957         ---help---
 958           Enable light-weight counting of various locking related events
 959           in the system with minimal performance impact. This reduces
 960           the chance of application behavior change because of timing
 961           differences. The counts are reported via debugfs.
 962
 963 # Select if the architecture has support for applying RELR relocations.
 964 config ARCH_HAS_RELR
 965         bool
 966
 967 config RELR
 968         bool "Use RELR relocation packing"
 969         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
 970         default y
 971         help
 972           Store the kernel's dynamic relocations in the RELR relocation packing
 973           format. Requires a compatible linker (LLD supports this feature), as
 974           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
 975           are compatible).
 976
 977 config ARCH_HAS_MEM_ENCRYPT
 978         bool
 979
 980 config HAVE_SPARSE_SYSCALL_NR
 981        bool
 982        help
 983           An architecture should select this if its syscall numbering is sparse
 984           to save space. For example, MIPS architecture has a syscall array with
 985           entries at 4000, 5000 and 6000 locations. This option turns on syscall
 986           related optimizations for a given architecture.
 987
 988 source "kernel/gcov/Kconfig"
 989
 990 source "scripts/gcc-plugins/Kconfig"
 991
 992 endmenu