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