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 arch has an uncached kernel segment and provides the
 252 # uncached_kernel_address / cached_kernel_address symbols to use it
 253 #
 254 config ARCH_HAS_UNCACHED_SEGMENT
 255         select ARCH_HAS_DMA_PREP_COHERENT
 256         bool
 257
 258 # Select if arch init_task must go in the __init_task_data section
 259 config ARCH_TASK_STRUCT_ON_STACK
 260         bool
 261
 262 # Select if arch has its private alloc_task_struct() function
 263 config ARCH_TASK_STRUCT_ALLOCATOR
 264         bool
 265
 266 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 267         bool
 268         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 269         help
 270           An architecture should select this to provide hardened usercopy
 271           knowledge about what region of the thread_struct should be
 272           whitelisted for copying to userspace. Normally this is only the
 273           FPU registers. Specifically, arch_thread_struct_whitelist()
 274           should be implemented. Without this, the entire thread_struct
 275           field in task_struct will be left whitelisted.
 276
 277 # Select if arch has its private alloc_thread_stack() function
 278 config ARCH_THREAD_STACK_ALLOCATOR
 279         bool
 280
 281 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 282 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 283         bool
 284
 285 config ARCH_32BIT_OFF_T
 286         bool
 287         depends on !64BIT
 288         help
 289           All new 32-bit architectures should have 64-bit off_t type on
 290           userspace side which corresponds to the loff_t kernel type. This
 291           is the requirement for modern ABIs. Some existing architectures
 292           still support 32-bit off_t. This option is enabled for all such
 293           architectures explicitly.
 294
 295 config HAVE_ASM_MODVERSIONS
 296         bool
 297         help
 298           This symbol should be selected by an architecure if it provides
 299           <asm/asm-prototypes.h> to support the module versioning for symbols
 300           exported from assembly code.
 301
 302 config HAVE_REGS_AND_STACK_ACCESS_API
 303         bool
 304         help
 305           This symbol should be selected by an architecure if it supports
 306           the API needed to access registers and stack entries from pt_regs,
 307           declared in asm/ptrace.h
 308           For example the kprobes-based event tracer needs this API.
 309
 310 config HAVE_RSEQ
 311         bool
 312         depends on HAVE_REGS_AND_STACK_ACCESS_API
 313         help
 314           This symbol should be selected by an architecture if it
 315           supports an implementation of restartable sequences.
 316
 317 config HAVE_FUNCTION_ARG_ACCESS_API
 318         bool
 319         help
 320           This symbol should be selected by an architecure if it supports
 321           the API needed to access function arguments from pt_regs,
 322           declared in asm/ptrace.h
 323
 324 config HAVE_CLK
 325         bool
 326         help
 327           The <linux/clk.h> calls support software clock gating and
 328           thus are a key power management tool on many systems.
 329
 330 config HAVE_HW_BREAKPOINT
 331         bool
 332         depends on PERF_EVENTS
 333
 334 config HAVE_MIXED_BREAKPOINTS_REGS
 335         bool
 336         depends on HAVE_HW_BREAKPOINT
 337         help
 338           Depending on the arch implementation of hardware breakpoints,
 339           some of them have separate registers for data and instruction
 340           breakpoints addresses, others have mixed registers to store
 341           them but define the access type in a control register.
 342           Select this option if your arch implements breakpoints under the
 343           latter fashion.
 344
 345 config HAVE_USER_RETURN_NOTIFIER
 346         bool
 347
 348 config HAVE_PERF_EVENTS_NMI
 349         bool
 350         help
 351           System hardware can generate an NMI using the perf event
 352           subsystem.  Also has support for calculating CPU cycle events
 353           to determine how many clock cycles in a given period.
 354
 355 config HAVE_HARDLOCKUP_DETECTOR_PERF
 356         bool
 357         depends on HAVE_PERF_EVENTS_NMI
 358         help
 359           The arch chooses to use the generic perf-NMI-based hardlockup
 360           detector. Must define HAVE_PERF_EVENTS_NMI.
 361
 362 config HAVE_NMI_WATCHDOG
 363         depends on HAVE_NMI
 364         bool
 365         help
 366           The arch provides a low level NMI watchdog. It provides
 367           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 368
 369 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 370         bool
 371         select HAVE_NMI_WATCHDOG
 372         help
 373           The arch chooses to provide its own hardlockup detector, which is
 374           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 375           interfaces and parameters provided by hardlockup detector subsystem.
 376
 377 config HAVE_PERF_REGS
 378         bool
 379         help
 380           Support selective register dumps for perf events. This includes
 381           bit-mapping of each registers and a unique architecture id.
 382
 383 config HAVE_PERF_USER_STACK_DUMP
 384         bool
 385         help
 386           Support user stack dumps for perf event samples. This needs
 387           access to the user stack pointer which is not unified across
 388           architectures.
 389
 390 config HAVE_ARCH_JUMP_LABEL
 391         bool
 392
 393 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 394         bool
 395
 396 config MMU_GATHER_TABLE_FREE
 397         bool
 398
 399 config MMU_GATHER_RCU_TABLE_FREE
 400         bool
 401         select MMU_GATHER_TABLE_FREE
 402
 403 config MMU_GATHER_PAGE_SIZE
 404         bool
 405
 406 config MMU_GATHER_NO_RANGE
 407         bool
 408
 409 config MMU_GATHER_NO_GATHER
 410         bool
 411         depends on MMU_GATHER_TABLE_FREE
 412
 413 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 414         bool
 415
 416 config HAVE_ALIGNED_STRUCT_PAGE
 417         bool
 418         help
 419           This makes sure that struct pages are double word aligned and that
 420           e.g. the SLUB allocator can perform double word atomic operations
 421           on a struct page for better performance. However selecting this
 422           might increase the size of a struct page by a word.
 423
 424 config HAVE_CMPXCHG_LOCAL
 425         bool
 426
 427 config HAVE_CMPXCHG_DOUBLE
 428         bool
 429
 430 config ARCH_WEAK_RELEASE_ACQUIRE
 431         bool
 432
 433 config ARCH_WANT_IPC_PARSE_VERSION
 434         bool
 435
 436 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 437         bool
 438
 439 config ARCH_WANT_OLD_COMPAT_IPC
 440         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 441         bool
 442
 443 config HAVE_ARCH_SECCOMP_FILTER
 444         bool
 445         help
 446           An arch should select this symbol if it provides all of these things:
 447           - syscall_get_arch()
 448           - syscall_get_arguments()
 449           - syscall_rollback()
 450           - syscall_set_return_value()
 451           - SIGSYS siginfo_t support
 452           - secure_computing is called from a ptrace_event()-safe context
 453           - secure_computing return value is checked and a return value of -1
 454             results in the system call being skipped immediately.
 455           - seccomp syscall wired up
 456
 457 config SECCOMP_FILTER
 458         def_bool y
 459         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 460         help
 461           Enable tasks to build secure computing environments defined
 462           in terms of Berkeley Packet Filter programs which implement
 463           task-defined system call filtering polices.
 464
 465           See Documentation/userspace-api/seccomp_filter.rst for details.
 466
 467 config HAVE_ARCH_STACKLEAK
 468         bool
 469         help
 470           An architecture should select this if it has the code which
 471           fills the used part of the kernel stack with the STACKLEAK_POISON
 472           value before returning from system calls.
 473
 474 config HAVE_STACKPROTECTOR
 475         bool
 476         help
 477           An arch should select this symbol if:
 478           - it has implemented a stack canary (e.g. __stack_chk_guard)
 479
 480 config CC_HAS_STACKPROTECTOR_NONE
 481         def_bool $(cc-option,-fno-stack-protector)
 482
 483 config STACKPROTECTOR
 484         bool "Stack Protector buffer overflow detection"
 485         depends on HAVE_STACKPROTECTOR
 486         depends on $(cc-option,-fstack-protector)
 487         default y
 488         help
 489           This option turns on the "stack-protector" GCC feature. This
 490           feature puts, at the beginning of functions, a canary value on
 491           the stack just before the return address, and validates
 492           the value just before actually returning.  Stack based buffer
 493           overflows (that need to overwrite this return address) now also
 494           overwrite the canary, which gets detected and the attack is then
 495           neutralized via a kernel panic.
 496
 497           Functions will have the stack-protector canary logic added if they
 498           have an 8-byte or larger character array on the stack.
 499
 500           This feature requires gcc version 4.2 or above, or a distribution
 501           gcc with the feature backported ("-fstack-protector").
 502
 503           On an x86 "defconfig" build, this feature adds canary checks to
 504           about 3% of all kernel functions, which increases kernel code size
 505           by about 0.3%.
 506
 507 config STACKPROTECTOR_STRONG
 508         bool "Strong Stack Protector"
 509         depends on STACKPROTECTOR
 510         depends on $(cc-option,-fstack-protector-strong)
 511         default y
 512         help
 513           Functions will have the stack-protector canary logic added in any
 514           of the following conditions:
 515
 516           - local variable's address used as part of the right hand side of an
 517             assignment or function argument
 518           - local variable is an array (or union containing an array),
 519             regardless of array type or length
 520           - uses register local variables
 521
 522           This feature requires gcc version 4.9 or above, or a distribution
 523           gcc with the feature backported ("-fstack-protector-strong").
 524
 525           On an x86 "defconfig" build, this feature adds canary checks to
 526           about 20% of all kernel functions, which increases the kernel code
 527           size by about 2%.
 528
 529 config HAVE_ARCH_WITHIN_STACK_FRAMES
 530         bool
 531         help
 532           An architecture should select this if it can walk the kernel stack
 533           frames to determine if an object is part of either the arguments
 534           or local variables (i.e. that it excludes saved return addresses,
 535           and similar) by implementing an inline arch_within_stack_frames(),
 536           which is used by CONFIG_HARDENED_USERCOPY.
 537
 538 config HAVE_CONTEXT_TRACKING
 539         bool
 540         help
 541           Provide kernel/user boundaries probes necessary for subsystems
 542           that need it, such as userspace RCU extended quiescent state.
 543           Syscalls need to be wrapped inside user_exit()-user_enter() through
 544           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 545           wrapped as well. Irqs are already protected inside
 546           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 547           irq exit still need to be protected.
 548
 549 config HAVE_VIRT_CPU_ACCOUNTING
 550         bool
 551
 552 config ARCH_HAS_SCALED_CPUTIME
 553         bool
 554
 555 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 556         bool
 557         default y if 64BIT
 558         help
 559           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 560           Before enabling this option, arch code must be audited
 561           to ensure there are no races in concurrent read/write of
 562           cputime_t. For example, reading/writing 64-bit cputime_t on
 563           some 32-bit arches may require multiple accesses, so proper
 564           locking is needed to protect against concurrent accesses.
 565
 566
 567 config HAVE_IRQ_TIME_ACCOUNTING
 568         bool
 569         help
 570           Archs need to ensure they use a high enough resolution clock to
 571           support irq time accounting and then call enable_sched_clock_irqtime().
 572
 573 config HAVE_MOVE_PMD
 574         bool
 575         help
 576           Archs that select this are able to move page tables at the PMD level.
 577
 578 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 579         bool
 580
 581 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 582         bool
 583
 584 config HAVE_ARCH_HUGE_VMAP
 585         bool
 586
 587 config ARCH_WANT_HUGE_PMD_SHARE
 588         bool
 589
 590 config HAVE_ARCH_SOFT_DIRTY
 591         bool
 592
 593 config HAVE_MOD_ARCH_SPECIFIC
 594         bool
 595         help
 596           The arch uses struct mod_arch_specific to store data.  Many arches
 597           just need a simple module loader without arch specific data - those
 598           should not enable this.
 599
 600 config MODULES_USE_ELF_RELA
 601         bool
 602         help
 603           Modules only use ELF RELA relocations.  Modules with ELF REL
 604           relocations will give an error.
 605
 606 config MODULES_USE_ELF_REL
 607         bool
 608         help
 609           Modules only use ELF REL relocations.  Modules with ELF RELA
 610           relocations will give an error.
 611
 612 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 613         bool
 614         help
 615           Architecture doesn't only execute the irq handler on the irq stack
 616           but also irq_exit(). This way we can process softirqs on this irq
 617           stack instead of switching to a new one when we call __do_softirq()
 618           in the end of an hardirq.
 619           This spares a stack switch and improves cache usage on softirq
 620           processing.
 621
 622 config PGTABLE_LEVELS
 623         int
 624         default 2
 625
 626 config ARCH_HAS_ELF_RANDOMIZE
 627         bool
 628         help
 629           An architecture supports choosing randomized locations for
 630           stack, mmap, brk, and ET_DYN. Defined functions:
 631           - arch_mmap_rnd()
 632           - arch_randomize_brk()
 633
 634 config HAVE_ARCH_MMAP_RND_BITS
 635         bool
 636         help
 637           An arch should select this symbol if it supports setting a variable
 638           number of bits for use in establishing the base address for mmap
 639           allocations, has MMU enabled and provides values for both:
 640           - ARCH_MMAP_RND_BITS_MIN
 641           - ARCH_MMAP_RND_BITS_MAX
 642
 643 config HAVE_EXIT_THREAD
 644         bool
 645         help
 646           An architecture implements exit_thread.
 647
 648 config ARCH_MMAP_RND_BITS_MIN
 649         int
 650
 651 config ARCH_MMAP_RND_BITS_MAX
 652         int
 653
 654 config ARCH_MMAP_RND_BITS_DEFAULT
 655         int
 656
 657 config ARCH_MMAP_RND_BITS
 658         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 659         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 660         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 661         default ARCH_MMAP_RND_BITS_MIN
 662         depends on HAVE_ARCH_MMAP_RND_BITS
 663         help
 664           This value can be used to select the number of bits to use to
 665           determine the random offset to the base address of vma regions
 666           resulting from mmap allocations. This value will be bounded
 667           by the architecture's minimum and maximum supported values.
 668
 669           This value can be changed after boot using the
 670           /proc/sys/vm/mmap_rnd_bits tunable
 671
 672 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 673         bool
 674         help
 675           An arch should select this symbol if it supports running applications
 676           in compatibility mode, supports setting a variable number of bits for
 677           use in establishing the base address for mmap allocations, has MMU
 678           enabled and provides values for both:
 679           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 680           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 681
 682 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 683         int
 684
 685 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 686         int
 687
 688 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 689         int
 690
 691 config ARCH_MMAP_RND_COMPAT_BITS
 692         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 693         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 694         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 695         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 696         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 697         help
 698           This value can be used to select the number of bits to use to
 699           determine the random offset to the base address of vma regions
 700           resulting from mmap allocations for compatible applications This
 701           value will be bounded by the architecture's minimum and maximum
 702           supported values.
 703
 704           This value can be changed after boot using the
 705           /proc/sys/vm/mmap_rnd_compat_bits tunable
 706
 707 config HAVE_ARCH_COMPAT_MMAP_BASES
 708         bool
 709         help
 710           This allows 64bit applications to invoke 32-bit mmap() syscall
 711           and vice-versa 32-bit applications to call 64-bit mmap().
 712           Required for applications doing different bitness syscalls.
 713
 714 # This allows to use a set of generic functions to determine mmap base
 715 # address by giving priority to top-down scheme only if the process
 716 # is not in legacy mode (compat task, unlimited stack size or
 717 # sysctl_legacy_va_layout).
 718 # Architecture that selects this option can provide its own version of:
 719 # - STACK_RND_MASK
 720 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 721         bool
 722         depends on MMU
 723         select ARCH_HAS_ELF_RANDOMIZE
 724
 725 config HAVE_COPY_THREAD_TLS
 726         bool
 727         help
 728           Architecture provides copy_thread_tls to accept tls argument via
 729           normal C parameter passing, rather than extracting the syscall
 730           argument from pt_regs.
 731
 732 config HAVE_STACK_VALIDATION
 733         bool
 734         help
 735           Architecture supports the 'objtool check' host tool command, which
 736           performs compile-time stack metadata validation.
 737
 738 config HAVE_RELIABLE_STACKTRACE
 739         bool
 740         help
 741           Architecture has a save_stack_trace_tsk_reliable() function which
 742           only returns a stack trace if it can guarantee the trace is reliable.
 743
 744 config HAVE_ARCH_HASH
 745         bool
 746         default n
 747         help
 748           If this is set, the architecture provides an <asm/hash.h>
 749           file which provides platform-specific implementations of some
 750           functions in <linux/hash.h> or fs/namei.c.
 751
 752 config HAVE_ARCH_NVRAM_OPS
 753         bool
 754
 755 config ISA_BUS_API
 756         def_bool ISA
 757
 758 #
 759 # ABI hall of shame
 760 #
 761 config CLONE_BACKWARDS
 762         bool
 763         help
 764           Architecture has tls passed as the 4th argument of clone(2),
 765           not the 5th one.
 766
 767 config CLONE_BACKWARDS2
 768         bool
 769         help
 770           Architecture has the first two arguments of clone(2) swapped.
 771
 772 config CLONE_BACKWARDS3
 773         bool
 774         help
 775           Architecture has tls passed as the 3rd argument of clone(2),
 776           not the 5th one.
 777
 778 config ODD_RT_SIGACTION
 779         bool
 780         help
 781           Architecture has unusual rt_sigaction(2) arguments
 782
 783 config OLD_SIGSUSPEND
 784         bool
 785         help
 786           Architecture has old sigsuspend(2) syscall, of one-argument variety
 787
 788 config OLD_SIGSUSPEND3
 789         bool
 790         help
 791           Even weirder antique ABI - three-argument sigsuspend(2)
 792
 793 config OLD_SIGACTION
 794         bool
 795         help
 796           Architecture has old sigaction(2) syscall.  Nope, not the same
 797           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 798           but fairly different variant of sigaction(2), thanks to OSF/1
 799           compatibility...
 800
 801 config COMPAT_OLD_SIGACTION
 802         bool
 803
 804 config COMPAT_32BIT_TIME
 805         bool "Provide system calls for 32-bit time_t"
 806         default !64BIT || COMPAT
 807         help
 808           This enables 32 bit time_t support in addition to 64 bit time_t support.
 809           This is relevant on all 32-bit architectures, and 64-bit architectures
 810           as part of compat syscall handling.
 811
 812 config ARCH_NO_PREEMPT
 813         bool
 814
 815 config ARCH_SUPPORTS_RT
 816         bool
 817
 818 config CPU_NO_EFFICIENT_FFS
 819         def_bool n
 820
 821 config HAVE_ARCH_VMAP_STACK
 822         def_bool n
 823         help
 824           An arch should select this symbol if it can support kernel stacks
 825           in vmalloc space.  This means:
 826
 827           - vmalloc space must be large enough to hold many kernel stacks.
 828             This may rule out many 32-bit architectures.
 829
 830           - Stacks in vmalloc space need to work reliably.  For example, if
 831             vmap page tables are created on demand, either this mechanism
 832             needs to work while the stack points to a virtual address with
 833             unpopulated page tables or arch code (switch_to() and switch_mm(),
 834             most likely) needs to ensure that the stack's page table entries
 835             are populated before running on a possibly unpopulated stack.
 836
 837           - If the stack overflows into a guard page, something reasonable
 838             should happen.  The definition of "reasonable" is flexible, but
 839             instantly rebooting without logging anything would be unfriendly.
 840
 841 config VMAP_STACK
 842         default y
 843         bool "Use a virtually-mapped stack"
 844         depends on HAVE_ARCH_VMAP_STACK
 845         depends on !KASAN || KASAN_VMALLOC
 846         ---help---
 847           Enable this if you want the use virtually-mapped kernel stacks
 848           with guard pages.  This causes kernel stack overflows to be
 849           caught immediately rather than causing difficult-to-diagnose
 850           corruption.
 851
 852           To use this with KASAN, the architecture must support backing
 853           virtual mappings with real shadow memory, and KASAN_VMALLOC must
 854           be enabled.
 855
 856 config ARCH_OPTIONAL_KERNEL_RWX
 857         def_bool n
 858
 859 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 860         def_bool n
 861
 862 config ARCH_HAS_STRICT_KERNEL_RWX
 863         def_bool n
 864
 865 config STRICT_KERNEL_RWX
 866         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 867         depends on ARCH_HAS_STRICT_KERNEL_RWX
 868         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 869         help
 870           If this is set, kernel text and rodata memory will be made read-only,
 871           and non-text memory will be made non-executable. This provides
 872           protection against certain security exploits (e.g. executing the heap
 873           or modifying text)
 874
 875           These features are considered standard security practice these days.
 876           You should say Y here in almost all cases.
 877
 878 config ARCH_HAS_STRICT_MODULE_RWX
 879         def_bool n
 880
 881 config STRICT_MODULE_RWX
 882         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 883         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 884         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 885         help
 886           If this is set, module text and rodata memory will be made read-only,
 887           and non-text memory will be made non-executable. This provides
 888           protection against certain security exploits (e.g. writing to text)
 889
 890 # select if the architecture provides an asm/dma-direct.h header
 891 config ARCH_HAS_PHYS_TO_DMA
 892         bool
 893
 894 config HAVE_ARCH_COMPILER_H
 895         bool
 896         help
 897           An architecture can select this if it provides an
 898           asm/compiler.h header that should be included after
 899           linux/compiler-*.h in order to override macro definitions that those
 900           headers generally provide.
 901
 902 config HAVE_ARCH_PREL32_RELOCATIONS
 903         bool
 904         help
 905           May be selected by an architecture if it supports place-relative
 906           32-bit relocations, both in the toolchain and in the module loader,
 907           in which case relative references can be used in special sections
 908           for PCI fixup, initcalls etc which are only half the size on 64 bit
 909           architectures, and don't require runtime relocation on relocatable
 910           kernels.
 911
 912 config ARCH_USE_MEMREMAP_PROT
 913         bool
 914
 915 config LOCK_EVENT_COUNTS
 916         bool "Locking event counts collection"
 917         depends on DEBUG_FS
 918         ---help---
 919           Enable light-weight counting of various locking related events
 920           in the system with minimal performance impact. This reduces
 921           the chance of application behavior change because of timing
 922           differences. The counts are reported via debugfs.
 923
 924 # Select if the architecture has support for applying RELR relocations.
 925 config ARCH_HAS_RELR
 926         bool
 927
 928 config RELR
 929         bool "Use RELR relocation packing"
 930         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
 931         default y
 932         help
 933           Store the kernel's dynamic relocations in the RELR relocation packing
 934           format. Requires a compatible linker (LLD supports this feature), as
 935           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
 936           are compatible).
 937
 938 config ARCH_HAS_MEM_ENCRYPT
 939         bool
 940
 941 config HAVE_SPARSE_SYSCALL_NR
 942        bool
 943        help
 944           An architecture should select this if its syscall numbering is sparse
 945           to save space. For example, MIPS architecture has a syscall array with
 946           entries at 4000, 5000 and 6000 locations. This option turns on syscall
 947           related optimizations for a given architecture.
 948
 949 source "kernel/gcov/Kconfig"
 950
 951 source "scripts/gcc-plugins/Kconfig"
 952
 953 endmenu