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