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 HAVE_IMA_KEXEC
  22         bool
  23
  24 config HOTPLUG_SMT
  25         bool
  26
  27 config OPROFILE
  28         tristate "OProfile system profiling"
  29         depends on PROFILING
  30         depends on HAVE_OPROFILE
  31         select RING_BUFFER
  32         select RING_BUFFER_ALLOW_SWAP
  33         help
  34           OProfile is a profiling system capable of profiling the
  35           whole system, include the kernel, kernel modules, libraries,
  36           and applications.
  37
  38           If unsure, say N.
  39
  40 config OPROFILE_EVENT_MULTIPLEX
  41         bool "OProfile multiplexing support (EXPERIMENTAL)"
  42         default n
  43         depends on OPROFILE && X86
  44         help
  45           The number of hardware counters is limited. The multiplexing
  46           feature enables OProfile to gather more events than counters
  47           are provided by the hardware. This is realized by switching
  48           between events at a user specified time interval.
  49
  50           If unsure, say N.
  51
  52 config HAVE_OPROFILE
  53         bool
  54
  55 config OPROFILE_NMI_TIMER
  56         def_bool y
  57         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  58
  59 config KPROBES
  60         bool "Kprobes"
  61         depends on MODULES
  62         depends on HAVE_KPROBES
  63         select KALLSYMS
  64         help
  65           Kprobes allows you to trap at almost any kernel address and
  66           execute a callback function.  register_kprobe() establishes
  67           a probepoint and specifies the callback.  Kprobes is useful
  68           for kernel debugging, non-intrusive instrumentation and testing.
  69           If in doubt, say "N".
  70
  71 config JUMP_LABEL
  72        bool "Optimize very unlikely/likely branches"
  73        depends on HAVE_ARCH_JUMP_LABEL
  74        depends on CC_HAS_ASM_GOTO
  75        help
  76          This option enables a transparent branch optimization that
  77          makes certain almost-always-true or almost-always-false branch
  78          conditions even cheaper to execute within the kernel.
  79
  80          Certain performance-sensitive kernel code, such as trace points,
  81          scheduler functionality, networking code and KVM have such
  82          branches and include support for this optimization technique.
  83
  84          If it is detected that the compiler has support for "asm goto",
  85          the kernel will compile such branches with just a nop
  86          instruction. When the condition flag is toggled to true, the
  87          nop will be converted to a jump instruction to execute the
  88          conditional block of instructions.
  89
  90          This technique lowers overhead and stress on the branch prediction
  91          of the processor and generally makes the kernel faster. The update
  92          of the condition is slower, but those are always very rare.
  93
  94          ( On 32-bit x86, the necessary options added to the compiler
  95            flags may increase the size of the kernel slightly. )
  96
  97 config STATIC_KEYS_SELFTEST
  98         bool "Static key selftest"
  99         depends on JUMP_LABEL
 100         help
 101           Boot time self-test of the branch patching code.
 102
 103 config OPTPROBES
 104         def_bool y
 105         depends on KPROBES && HAVE_OPTPROBES
 106         select TASKS_RCU if PREEMPT
 107
 108 config KPROBES_ON_FTRACE
 109         def_bool y
 110         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 111         depends on DYNAMIC_FTRACE_WITH_REGS
 112         help
 113          If function tracer is enabled and the arch supports full
 114          passing of pt_regs to function tracing, then kprobes can
 115          optimize on top of function tracing.
 116
 117 config UPROBES
 118         def_bool n
 119         depends on ARCH_SUPPORTS_UPROBES
 120         help
 121           Uprobes is the user-space counterpart to kprobes: they
 122           enable instrumentation applications (such as 'perf probe')
 123           to establish unintrusive probes in user-space binaries and
 124           libraries, by executing handler functions when the probes
 125           are hit by user-space applications.
 126
 127           ( These probes come in the form of single-byte breakpoints,
 128             managed by the kernel and kept transparent to the probed
 129             application. )
 130
 131 config HAVE_64BIT_ALIGNED_ACCESS
 132         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 133         help
 134           Some architectures require 64 bit accesses to be 64 bit
 135           aligned, which also requires structs containing 64 bit values
 136           to be 64 bit aligned too. This includes some 32 bit
 137           architectures which can do 64 bit accesses, as well as 64 bit
 138           architectures without unaligned access.
 139
 140           This symbol should be selected by an architecture if 64 bit
 141           accesses are required to be 64 bit aligned in this way even
 142           though it is not a 64 bit architecture.
 143
 144           See Documentation/unaligned-memory-access.txt for more
 145           information on the topic of unaligned memory accesses.
 146
 147 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 148         bool
 149         help
 150           Some architectures are unable to perform unaligned accesses
 151           without the use of get_unaligned/put_unaligned. Others are
 152           unable to perform such accesses efficiently (e.g. trap on
 153           unaligned access and require fixing it up in the exception
 154           handler.)
 155
 156           This symbol should be selected by an architecture if it can
 157           perform unaligned accesses efficiently to allow different
 158           code paths to be selected for these cases. Some network
 159           drivers, for example, could opt to not fix up alignment
 160           problems with received packets if doing so would not help
 161           much.
 162
 163           See Documentation/unaligned-memory-access.txt for more
 164           information on the topic of unaligned memory accesses.
 165
 166 config ARCH_USE_BUILTIN_BSWAP
 167        bool
 168        help
 169          Modern versions of GCC (since 4.4) have builtin functions
 170          for handling byte-swapping. Using these, instead of the old
 171          inline assembler that the architecture code provides in the
 172          __arch_bswapXX() macros, allows the compiler to see what's
 173          happening and offers more opportunity for optimisation. In
 174          particular, the compiler will be able to combine the byteswap
 175          with a nearby load or store and use load-and-swap or
 176          store-and-swap instructions if the architecture has them. It
 177          should almost *never* result in code which is worse than the
 178          hand-coded assembler in <asm/swab.h>.  But just in case it
 179          does, the use of the builtins is optional.
 180
 181          Any architecture with load-and-swap or store-and-swap
 182          instructions should set this. And it shouldn't hurt to set it
 183          on architectures that don't have such instructions.
 184
 185 config KRETPROBES
 186         def_bool y
 187         depends on KPROBES && HAVE_KRETPROBES
 188
 189 config USER_RETURN_NOTIFIER
 190         bool
 191         depends on HAVE_USER_RETURN_NOTIFIER
 192         help
 193           Provide a kernel-internal notification when a cpu is about to
 194           switch to user mode.
 195
 196 config HAVE_IOREMAP_PROT
 197         bool
 198
 199 config HAVE_KPROBES
 200         bool
 201
 202 config HAVE_KRETPROBES
 203         bool
 204
 205 config HAVE_OPTPROBES
 206         bool
 207
 208 config HAVE_KPROBES_ON_FTRACE
 209         bool
 210
 211 config HAVE_FUNCTION_ERROR_INJECTION
 212         bool
 213
 214 config HAVE_NMI
 215         bool
 216
 217 #
 218 # An arch should select this if it provides all these things:
 219 #
 220 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 221 #       arch_has_single_step()  if there is hardware single-step support
 222 #       arch_has_block_step()   if there is hardware block-step support
 223 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 224 #       linux/regset.h          user_regset interfaces
 225 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 226 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 227 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 228 #       signal delivery         calls tracehook_signal_handler()
 229 #
 230 config HAVE_ARCH_TRACEHOOK
 231         bool
 232
 233 config HAVE_DMA_CONTIGUOUS
 234         bool
 235
 236 config GENERIC_SMP_IDLE_THREAD
 237        bool
 238
 239 config GENERIC_IDLE_POLL_SETUP
 240        bool
 241
 242 config ARCH_HAS_FORTIFY_SOURCE
 243         bool
 244         help
 245           An architecture should select this when it can successfully
 246           build and run with CONFIG_FORTIFY_SOURCE.
 247
 248 #
 249 # Select if the arch provides a historic keepinit alias for the retain_initrd
 250 # command line option
 251 #
 252 config ARCH_HAS_KEEPINITRD
 253         bool
 254
 255 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 256 config ARCH_HAS_SET_MEMORY
 257         bool
 258
 259 # Select if arch has all set_direct_map_invalid/default() functions
 260 config ARCH_HAS_SET_DIRECT_MAP
 261         bool
 262
 263 # Select if arch init_task must go in the __init_task_data section
 264 config ARCH_TASK_STRUCT_ON_STACK
 265        bool
 266
 267 # Select if arch has its private alloc_task_struct() function
 268 config ARCH_TASK_STRUCT_ALLOCATOR
 269         bool
 270
 271 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 272         bool
 273         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 274         help
 275           An architecture should select this to provide hardened usercopy
 276           knowledge about what region of the thread_struct should be
 277           whitelisted for copying to userspace. Normally this is only the
 278           FPU registers. Specifically, arch_thread_struct_whitelist()
 279           should be implemented. Without this, the entire thread_struct
 280           field in task_struct will be left whitelisted.
 281
 282 # Select if arch has its private alloc_thread_stack() function
 283 config ARCH_THREAD_STACK_ALLOCATOR
 284         bool
 285
 286 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 287 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 288         bool
 289
 290 config ARCH_32BIT_OFF_T
 291         bool
 292         depends on !64BIT
 293         help
 294           All new 32-bit architectures should have 64-bit off_t type on
 295           userspace side which corresponds to the loff_t kernel type. This
 296           is the requirement for modern ABIs. Some existing architectures
 297           still support 32-bit off_t. This option is enabled for all such
 298           architectures explicitly.
 299
 300 config HAVE_REGS_AND_STACK_ACCESS_API
 301         bool
 302         help
 303           This symbol should be selected by an architecure if it supports
 304           the API needed to access registers and stack entries from pt_regs,
 305           declared in asm/ptrace.h
 306           For example the kprobes-based event tracer needs this API.
 307
 308 config HAVE_RSEQ
 309         bool
 310         depends on HAVE_REGS_AND_STACK_ACCESS_API
 311         help
 312           This symbol should be selected by an architecture if it
 313           supports an implementation of restartable sequences.
 314
 315 config HAVE_FUNCTION_ARG_ACCESS_API
 316         bool
 317         help
 318           This symbol should be selected by an architecure if it supports
 319           the API needed to access function arguments from pt_regs,
 320           declared in asm/ptrace.h
 321
 322 config HAVE_CLK
 323         bool
 324         help
 325           The <linux/clk.h> calls support software clock gating and
 326           thus are a key power management tool on many systems.
 327
 328 config HAVE_HW_BREAKPOINT
 329         bool
 330         depends on PERF_EVENTS
 331
 332 config HAVE_MIXED_BREAKPOINTS_REGS
 333         bool
 334         depends on HAVE_HW_BREAKPOINT
 335         help
 336           Depending on the arch implementation of hardware breakpoints,
 337           some of them have separate registers for data and instruction
 338           breakpoints addresses, others have mixed registers to store
 339           them but define the access type in a control register.
 340           Select this option if your arch implements breakpoints under the
 341           latter fashion.
 342
 343 config HAVE_USER_RETURN_NOTIFIER
 344         bool
 345
 346 config HAVE_PERF_EVENTS_NMI
 347         bool
 348         help
 349           System hardware can generate an NMI using the perf event
 350           subsystem.  Also has support for calculating CPU cycle events
 351           to determine how many clock cycles in a given period.
 352
 353 config HAVE_HARDLOCKUP_DETECTOR_PERF
 354         bool
 355         depends on HAVE_PERF_EVENTS_NMI
 356         help
 357           The arch chooses to use the generic perf-NMI-based hardlockup
 358           detector. Must define HAVE_PERF_EVENTS_NMI.
 359
 360 config HAVE_NMI_WATCHDOG
 361         depends on HAVE_NMI
 362         bool
 363         help
 364           The arch provides a low level NMI watchdog. It provides
 365           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 366
 367 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 368         bool
 369         select HAVE_NMI_WATCHDOG
 370         help
 371           The arch chooses to provide its own hardlockup detector, which is
 372           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 373           interfaces and parameters provided by hardlockup detector subsystem.
 374
 375 config HAVE_PERF_REGS
 376         bool
 377         help
 378           Support selective register dumps for perf events. This includes
 379           bit-mapping of each registers and a unique architecture id.
 380
 381 config HAVE_PERF_USER_STACK_DUMP
 382         bool
 383         help
 384           Support user stack dumps for perf event samples. This needs
 385           access to the user stack pointer which is not unified across
 386           architectures.
 387
 388 config HAVE_ARCH_JUMP_LABEL
 389         bool
 390
 391 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 392         bool
 393
 394 config HAVE_RCU_TABLE_FREE
 395         bool
 396
 397 config HAVE_RCU_TABLE_NO_INVALIDATE
 398         bool
 399
 400 config HAVE_MMU_GATHER_PAGE_SIZE
 401         bool
 402
 403 config HAVE_MMU_GATHER_NO_GATHER
 404         bool
 405
 406 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 407         bool
 408
 409 config HAVE_ALIGNED_STRUCT_PAGE
 410         bool
 411         help
 412           This makes sure that struct pages are double word aligned and that
 413           e.g. the SLUB allocator can perform double word atomic operations
 414           on a struct page for better performance. However selecting this
 415           might increase the size of a struct page by a word.
 416
 417 config HAVE_CMPXCHG_LOCAL
 418         bool
 419
 420 config HAVE_CMPXCHG_DOUBLE
 421         bool
 422
 423 config ARCH_WEAK_RELEASE_ACQUIRE
 424         bool
 425
 426 config ARCH_WANT_IPC_PARSE_VERSION
 427         bool
 428
 429 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 430         bool
 431
 432 config ARCH_WANT_OLD_COMPAT_IPC
 433         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 434         bool
 435
 436 config HAVE_ARCH_SECCOMP_FILTER
 437         bool
 438         help
 439           An arch should select this symbol if it provides all of these things:
 440           - syscall_get_arch()
 441           - syscall_get_arguments()
 442           - syscall_rollback()
 443           - syscall_set_return_value()
 444           - SIGSYS siginfo_t support
 445           - secure_computing is called from a ptrace_event()-safe context
 446           - secure_computing return value is checked and a return value of -1
 447             results in the system call being skipped immediately.
 448           - seccomp syscall wired up
 449
 450 config SECCOMP_FILTER
 451         def_bool y
 452         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 453         help
 454           Enable tasks to build secure computing environments defined
 455           in terms of Berkeley Packet Filter programs which implement
 456           task-defined system call filtering polices.
 457
 458           See Documentation/userspace-api/seccomp_filter.rst for details.
 459
 460 config HAVE_ARCH_STACKLEAK
 461         bool
 462         help
 463           An architecture should select this if it has the code which
 464           fills the used part of the kernel stack with the STACKLEAK_POISON
 465           value before returning from system calls.
 466
 467 config HAVE_STACKPROTECTOR
 468         bool
 469         help
 470           An arch should select this symbol if:
 471           - it has implemented a stack canary (e.g. __stack_chk_guard)
 472
 473 config CC_HAS_STACKPROTECTOR_NONE
 474         def_bool $(cc-option,-fno-stack-protector)
 475
 476 config STACKPROTECTOR
 477         bool "Stack Protector buffer overflow detection"
 478         depends on HAVE_STACKPROTECTOR
 479         depends on $(cc-option,-fstack-protector)
 480         default y
 481         help
 482           This option turns on the "stack-protector" GCC feature. This
 483           feature puts, at the beginning of functions, a canary value on
 484           the stack just before the return address, and validates
 485           the value just before actually returning.  Stack based buffer
 486           overflows (that need to overwrite this return address) now also
 487           overwrite the canary, which gets detected and the attack is then
 488           neutralized via a kernel panic.
 489
 490           Functions will have the stack-protector canary logic added if they
 491           have an 8-byte or larger character array on the stack.
 492
 493           This feature requires gcc version 4.2 or above, or a distribution
 494           gcc with the feature backported ("-fstack-protector").
 495
 496           On an x86 "defconfig" build, this feature adds canary checks to
 497           about 3% of all kernel functions, which increases kernel code size
 498           by about 0.3%.
 499
 500 config STACKPROTECTOR_STRONG
 501         bool "Strong Stack Protector"
 502         depends on STACKPROTECTOR
 503         depends on $(cc-option,-fstack-protector-strong)
 504         default y
 505         help
 506           Functions will have the stack-protector canary logic added in any
 507           of the following conditions:
 508
 509           - local variable's address used as part of the right hand side of an
 510             assignment or function argument
 511           - local variable is an array (or union containing an array),
 512             regardless of array type or length
 513           - uses register local variables
 514
 515           This feature requires gcc version 4.9 or above, or a distribution
 516           gcc with the feature backported ("-fstack-protector-strong").
 517
 518           On an x86 "defconfig" build, this feature adds canary checks to
 519           about 20% of all kernel functions, which increases the kernel code
 520           size by about 2%.
 521
 522 config HAVE_ARCH_WITHIN_STACK_FRAMES
 523         bool
 524         help
 525           An architecture should select this if it can walk the kernel stack
 526           frames to determine if an object is part of either the arguments
 527           or local variables (i.e. that it excludes saved return addresses,
 528           and similar) by implementing an inline arch_within_stack_frames(),
 529           which is used by CONFIG_HARDENED_USERCOPY.
 530
 531 config HAVE_CONTEXT_TRACKING
 532         bool
 533         help
 534           Provide kernel/user boundaries probes necessary for subsystems
 535           that need it, such as userspace RCU extended quiescent state.
 536           Syscalls need to be wrapped inside user_exit()-user_enter() through
 537           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 538           wrapped as well. Irqs are already protected inside
 539           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 540           irq exit still need to be protected.
 541
 542 config HAVE_VIRT_CPU_ACCOUNTING
 543         bool
 544
 545 config ARCH_HAS_SCALED_CPUTIME
 546         bool
 547
 548 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 549         bool
 550         default y if 64BIT
 551         help
 552           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 553           Before enabling this option, arch code must be audited
 554           to ensure there are no races in concurrent read/write of
 555           cputime_t. For example, reading/writing 64-bit cputime_t on
 556           some 32-bit arches may require multiple accesses, so proper
 557           locking is needed to protect against concurrent accesses.
 558
 559
 560 config HAVE_IRQ_TIME_ACCOUNTING
 561         bool
 562         help
 563           Archs need to ensure they use a high enough resolution clock to
 564           support irq time accounting and then call enable_sched_clock_irqtime().
 565
 566 config HAVE_MOVE_PMD
 567         bool
 568         help
 569           Archs that select this are able to move page tables at the PMD level.
 570
 571 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 572         bool
 573
 574 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 575         bool
 576
 577 config HAVE_ARCH_HUGE_VMAP
 578         bool
 579
 580 config HAVE_ARCH_SOFT_DIRTY
 581         bool
 582
 583 config HAVE_MOD_ARCH_SPECIFIC
 584         bool
 585         help
 586           The arch uses struct mod_arch_specific to store data.  Many arches
 587           just need a simple module loader without arch specific data - those
 588           should not enable this.
 589
 590 config MODULES_USE_ELF_RELA
 591         bool
 592         help
 593           Modules only use ELF RELA relocations.  Modules with ELF REL
 594           relocations will give an error.
 595
 596 config MODULES_USE_ELF_REL
 597         bool
 598         help
 599           Modules only use ELF REL relocations.  Modules with ELF RELA
 600           relocations will give an error.
 601
 602 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 603         bool
 604         help
 605           Architecture doesn't only execute the irq handler on the irq stack
 606           but also irq_exit(). This way we can process softirqs on this irq
 607           stack instead of switching to a new one when we call __do_softirq()
 608           in the end of an hardirq.
 609           This spares a stack switch and improves cache usage on softirq
 610           processing.
 611
 612 config PGTABLE_LEVELS
 613         int
 614         default 2
 615
 616 config ARCH_HAS_ELF_RANDOMIZE
 617         bool
 618         help
 619           An architecture supports choosing randomized locations for
 620           stack, mmap, brk, and ET_DYN. Defined functions:
 621           - arch_mmap_rnd()
 622           - arch_randomize_brk()
 623
 624 config HAVE_ARCH_MMAP_RND_BITS
 625         bool
 626         help
 627           An arch should select this symbol if it supports setting a variable
 628           number of bits for use in establishing the base address for mmap
 629           allocations, has MMU enabled and provides values for both:
 630           - ARCH_MMAP_RND_BITS_MIN
 631           - ARCH_MMAP_RND_BITS_MAX
 632
 633 config HAVE_EXIT_THREAD
 634         bool
 635         help
 636           An architecture implements exit_thread.
 637
 638 config ARCH_MMAP_RND_BITS_MIN
 639         int
 640
 641 config ARCH_MMAP_RND_BITS_MAX
 642         int
 643
 644 config ARCH_MMAP_RND_BITS_DEFAULT
 645         int
 646
 647 config ARCH_MMAP_RND_BITS
 648         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 649         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 650         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 651         default ARCH_MMAP_RND_BITS_MIN
 652         depends on HAVE_ARCH_MMAP_RND_BITS
 653         help
 654           This value can be used to select the number of bits to use to
 655           determine the random offset to the base address of vma regions
 656           resulting from mmap allocations. This value will be bounded
 657           by the architecture's minimum and maximum supported values.
 658
 659           This value can be changed after boot using the
 660           /proc/sys/vm/mmap_rnd_bits tunable
 661
 662 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 663         bool
 664         help
 665           An arch should select this symbol if it supports running applications
 666           in compatibility mode, supports setting a variable number of bits for
 667           use in establishing the base address for mmap allocations, has MMU
 668           enabled and provides values for both:
 669           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 670           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 671
 672 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 673         int
 674
 675 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 676         int
 677
 678 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 679         int
 680
 681 config ARCH_MMAP_RND_COMPAT_BITS
 682         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 683         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 684         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 685         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 686         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 687         help
 688           This value can be used to select the number of bits to use to
 689           determine the random offset to the base address of vma regions
 690           resulting from mmap allocations for compatible applications This
 691           value will be bounded by the architecture's minimum and maximum
 692           supported values.
 693
 694           This value can be changed after boot using the
 695           /proc/sys/vm/mmap_rnd_compat_bits tunable
 696
 697 config HAVE_ARCH_COMPAT_MMAP_BASES
 698         bool
 699         help
 700           This allows 64bit applications to invoke 32-bit mmap() syscall
 701           and vice-versa 32-bit applications to call 64-bit mmap().
 702           Required for applications doing different bitness syscalls.
 703
 704 config HAVE_COPY_THREAD_TLS
 705         bool
 706         help
 707           Architecture provides copy_thread_tls to accept tls argument via
 708           normal C parameter passing, rather than extracting the syscall
 709           argument from pt_regs.
 710
 711 config HAVE_STACK_VALIDATION
 712         bool
 713         help
 714           Architecture supports the 'objtool check' host tool command, which
 715           performs compile-time stack metadata validation.
 716
 717 config HAVE_RELIABLE_STACKTRACE
 718         bool
 719         help
 720           Architecture has a save_stack_trace_tsk_reliable() function which
 721           only returns a stack trace if it can guarantee the trace is reliable.
 722
 723 config HAVE_ARCH_HASH
 724         bool
 725         default n
 726         help
 727           If this is set, the architecture provides an <asm/hash.h>
 728           file which provides platform-specific implementations of some
 729           functions in <linux/hash.h> or fs/namei.c.
 730
 731 config HAVE_ARCH_NVRAM_OPS
 732         bool
 733
 734 config ISA_BUS_API
 735         def_bool ISA
 736
 737 #
 738 # ABI hall of shame
 739 #
 740 config CLONE_BACKWARDS
 741         bool
 742         help
 743           Architecture has tls passed as the 4th argument of clone(2),
 744           not the 5th one.
 745
 746 config CLONE_BACKWARDS2
 747         bool
 748         help
 749           Architecture has the first two arguments of clone(2) swapped.
 750
 751 config CLONE_BACKWARDS3
 752         bool
 753         help
 754           Architecture has tls passed as the 3rd argument of clone(2),
 755           not the 5th one.
 756
 757 config ODD_RT_SIGACTION
 758         bool
 759         help
 760           Architecture has unusual rt_sigaction(2) arguments
 761
 762 config OLD_SIGSUSPEND
 763         bool
 764         help
 765           Architecture has old sigsuspend(2) syscall, of one-argument variety
 766
 767 config OLD_SIGSUSPEND3
 768         bool
 769         help
 770           Even weirder antique ABI - three-argument sigsuspend(2)
 771
 772 config OLD_SIGACTION
 773         bool
 774         help
 775           Architecture has old sigaction(2) syscall.  Nope, not the same
 776           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 777           but fairly different variant of sigaction(2), thanks to OSF/1
 778           compatibility...
 779
 780 config COMPAT_OLD_SIGACTION
 781         bool
 782
 783 config 64BIT_TIME
 784         def_bool y
 785         help
 786           This should be selected by all architectures that need to support
 787           new system calls with a 64-bit time_t. This is relevant on all 32-bit
 788           architectures, and 64-bit architectures as part of compat syscall
 789           handling.
 790
 791 config COMPAT_32BIT_TIME
 792         def_bool !64BIT || COMPAT
 793         help
 794           This enables 32 bit time_t support in addition to 64 bit time_t support.
 795           This is relevant on all 32-bit architectures, and 64-bit architectures
 796           as part of compat syscall handling.
 797
 798 config ARCH_NO_COHERENT_DMA_MMAP
 799         bool
 800
 801 config ARCH_NO_PREEMPT
 802         bool
 803
 804 config CPU_NO_EFFICIENT_FFS
 805         def_bool n
 806
 807 config HAVE_ARCH_VMAP_STACK
 808         def_bool n
 809         help
 810           An arch should select this symbol if it can support kernel stacks
 811           in vmalloc space.  This means:
 812
 813           - vmalloc space must be large enough to hold many kernel stacks.
 814             This may rule out many 32-bit architectures.
 815
 816           - Stacks in vmalloc space need to work reliably.  For example, if
 817             vmap page tables are created on demand, either this mechanism
 818             needs to work while the stack points to a virtual address with
 819             unpopulated page tables or arch code (switch_to() and switch_mm(),
 820             most likely) needs to ensure that the stack's page table entries
 821             are populated before running on a possibly unpopulated stack.
 822
 823           - If the stack overflows into a guard page, something reasonable
 824             should happen.  The definition of "reasonable" is flexible, but
 825             instantly rebooting without logging anything would be unfriendly.
 826
 827 config VMAP_STACK
 828         default y
 829         bool "Use a virtually-mapped stack"
 830         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 831         ---help---
 832           Enable this if you want the use virtually-mapped kernel stacks
 833           with guard pages.  This causes kernel stack overflows to be
 834           caught immediately rather than causing difficult-to-diagnose
 835           corruption.
 836
 837           This is presently incompatible with KASAN because KASAN expects
 838           the stack to map directly to the KASAN shadow map using a formula
 839           that is incorrect if the stack is in vmalloc space.
 840
 841 config ARCH_OPTIONAL_KERNEL_RWX
 842         def_bool n
 843
 844 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 845         def_bool n
 846
 847 config ARCH_HAS_STRICT_KERNEL_RWX
 848         def_bool n
 849
 850 config STRICT_KERNEL_RWX
 851         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 852         depends on ARCH_HAS_STRICT_KERNEL_RWX
 853         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 854         help
 855           If this is set, kernel text and rodata memory will be made read-only,
 856           and non-text memory will be made non-executable. This provides
 857           protection against certain security exploits (e.g. executing the heap
 858           or modifying text)
 859
 860           These features are considered standard security practice these days.
 861           You should say Y here in almost all cases.
 862
 863 config ARCH_HAS_STRICT_MODULE_RWX
 864         def_bool n
 865
 866 config STRICT_MODULE_RWX
 867         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 868         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 869         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 870         help
 871           If this is set, module text and rodata memory will be made read-only,
 872           and non-text memory will be made non-executable. This provides
 873           protection against certain security exploits (e.g. writing to text)
 874
 875 # select if the architecture provides an asm/dma-direct.h header
 876 config ARCH_HAS_PHYS_TO_DMA
 877         bool
 878
 879 config ARCH_HAS_REFCOUNT
 880         bool
 881         help
 882           An architecture selects this when it has implemented refcount_t
 883           using open coded assembly primitives that provide an optimized
 884           refcount_t implementation, possibly at the expense of some full
 885           refcount state checks of CONFIG_REFCOUNT_FULL=y.
 886
 887           The refcount overflow check behavior, however, must be retained.
 888           Catching overflows is the primary security concern for protecting
 889           against bugs in reference counts.
 890
 891 config REFCOUNT_FULL
 892         bool "Perform full reference count validation at the expense of speed"
 893         help
 894           Enabling this switches the refcounting infrastructure from a fast
 895           unchecked atomic_t implementation to a fully state checked
 896           implementation, which can be (slightly) slower but provides protections
 897           against various use-after-free conditions that can be used in
 898           security flaw exploits.
 899
 900 config HAVE_ARCH_COMPILER_H
 901         bool
 902         help
 903           An architecture can select this if it provides an
 904           asm/compiler.h header that should be included after
 905           linux/compiler-*.h in order to override macro definitions that those
 906           headers generally provide.
 907
 908 config HAVE_ARCH_PREL32_RELOCATIONS
 909         bool
 910         help
 911           May be selected by an architecture if it supports place-relative
 912           32-bit relocations, both in the toolchain and in the module loader,
 913           in which case relative references can be used in special sections
 914           for PCI fixup, initcalls etc which are only half the size on 64 bit
 915           architectures, and don't require runtime relocation on relocatable
 916           kernels.
 917
 918 config ARCH_USE_MEMREMAP_PROT
 919         bool
 920
 921 config LOCK_EVENT_COUNTS
 922         bool "Locking event counts collection"
 923         depends on DEBUG_FS
 924         ---help---
 925           Enable light-weight counting of various locking related events
 926           in the system with minimal performance impact. This reduces
 927           the chance of application behavior change because of timing
 928           differences. The counts are reported via debugfs.
 929
 930 source "kernel/gcov/Kconfig"
 931
 932 source "scripts/gcc-plugins/Kconfig"
 933
 934 endmenu