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 SET_FS
  28         bool
  29
  30 config HOTPLUG_SMT
  31         bool
  32
  33 config GENERIC_ENTRY
  34        bool
  35
  36 config OPROFILE
  37         tristate "OProfile system profiling"
  38         depends on PROFILING
  39         depends on HAVE_OPROFILE
  40         select RING_BUFFER
  41         select RING_BUFFER_ALLOW_SWAP
  42         help
  43           OProfile is a profiling system capable of profiling the
  44           whole system, include the kernel, kernel modules, libraries,
  45           and applications.
  46
  47           If unsure, say N.
  48
  49 config OPROFILE_EVENT_MULTIPLEX
  50         bool "OProfile multiplexing support (EXPERIMENTAL)"
  51         default n
  52         depends on OPROFILE && X86
  53         help
  54           The number of hardware counters is limited. The multiplexing
  55           feature enables OProfile to gather more events than counters
  56           are provided by the hardware. This is realized by switching
  57           between events at a user specified time interval.
  58
  59           If unsure, say N.
  60
  61 config HAVE_OPROFILE
  62         bool
  63
  64 config OPROFILE_NMI_TIMER
  65         def_bool y
  66         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  67
  68 config KPROBES
  69         bool "Kprobes"
  70         depends on MODULES
  71         depends on HAVE_KPROBES
  72         select KALLSYMS
  73         help
  74           Kprobes allows you to trap at almost any kernel address and
  75           execute a callback function.  register_kprobe() establishes
  76           a probepoint and specifies the callback.  Kprobes is useful
  77           for kernel debugging, non-intrusive instrumentation and testing.
  78           If in doubt, say "N".
  79
  80 config JUMP_LABEL
  81         bool "Optimize very unlikely/likely branches"
  82         depends on HAVE_ARCH_JUMP_LABEL
  83         depends on CC_HAS_ASM_GOTO
  84         help
  85          This option enables a transparent branch optimization that
  86          makes certain almost-always-true or almost-always-false branch
  87          conditions even cheaper to execute within the kernel.
  88
  89          Certain performance-sensitive kernel code, such as trace points,
  90          scheduler functionality, networking code and KVM have such
  91          branches and include support for this optimization technique.
  92
  93          If it is detected that the compiler has support for "asm goto",
  94          the kernel will compile such branches with just a nop
  95          instruction. When the condition flag is toggled to true, the
  96          nop will be converted to a jump instruction to execute the
  97          conditional block of instructions.
  98
  99          This technique lowers overhead and stress on the branch prediction
 100          of the processor and generally makes the kernel faster. The update
 101          of the condition is slower, but those are always very rare.
 102
 103          ( On 32-bit x86, the necessary options added to the compiler
 104            flags may increase the size of the kernel slightly. )
 105
 106 config STATIC_KEYS_SELFTEST
 107         bool "Static key selftest"
 108         depends on JUMP_LABEL
 109         help
 110           Boot time self-test of the branch patching code.
 111
 112 config STATIC_CALL_SELFTEST
 113         bool "Static call selftest"
 114         depends on HAVE_STATIC_CALL
 115         help
 116           Boot time self-test of the call patching code.
 117
 118 config OPTPROBES
 119         def_bool y
 120         depends on KPROBES && HAVE_OPTPROBES
 121         select TASKS_RCU if PREEMPTION
 122
 123 config KPROBES_ON_FTRACE
 124         def_bool y
 125         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 126         depends on DYNAMIC_FTRACE_WITH_REGS
 127         help
 128          If function tracer is enabled and the arch supports full
 129          passing of pt_regs to function tracing, then kprobes can
 130          optimize on top of function tracing.
 131
 132 config UPROBES
 133         def_bool n
 134         depends on ARCH_SUPPORTS_UPROBES
 135         help
 136           Uprobes is the user-space counterpart to kprobes: they
 137           enable instrumentation applications (such as 'perf probe')
 138           to establish unintrusive probes in user-space binaries and
 139           libraries, by executing handler functions when the probes
 140           are hit by user-space applications.
 141
 142           ( These probes come in the form of single-byte breakpoints,
 143             managed by the kernel and kept transparent to the probed
 144             application. )
 145
 146 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 147         bool
 148         help
 149           Some architectures are unable to perform unaligned accesses
 150           without the use of get_unaligned/put_unaligned. Others are
 151           unable to perform such accesses efficiently (e.g. trap on
 152           unaligned access and require fixing it up in the exception
 153           handler.)
 154
 155           This symbol should be selected by an architecture if it can
 156           perform unaligned accesses efficiently to allow different
 157           code paths to be selected for these cases. Some network
 158           drivers, for example, could opt to not fix up alignment
 159           problems with received packets if doing so would not help
 160           much.
 161
 162           See Documentation/core-api/unaligned-memory-access.rst for more
 163           information on the topic of unaligned memory accesses.
 164
 165 config ARCH_USE_BUILTIN_BSWAP
 166         bool
 167         help
 168          Modern versions of GCC (since 4.4) have builtin functions
 169          for handling byte-swapping. Using these, instead of the old
 170          inline assembler that the architecture code provides in the
 171          __arch_bswapXX() macros, allows the compiler to see what's
 172          happening and offers more opportunity for optimisation. In
 173          particular, the compiler will be able to combine the byteswap
 174          with a nearby load or store and use load-and-swap or
 175          store-and-swap instructions if the architecture has them. It
 176          should almost *never* result in code which is worse than the
 177          hand-coded assembler in <asm/swab.h>.  But just in case it
 178          does, the use of the builtins is optional.
 179
 180          Any architecture with load-and-swap or store-and-swap
 181          instructions should set this. And it shouldn't hurt to set it
 182          on architectures that don't have such instructions.
 183
 184 config KRETPROBES
 185         def_bool y
 186         depends on KPROBES && HAVE_KRETPROBES
 187
 188 config USER_RETURN_NOTIFIER
 189         bool
 190         depends on HAVE_USER_RETURN_NOTIFIER
 191         help
 192           Provide a kernel-internal notification when a cpu is about to
 193           switch to user mode.
 194
 195 config HAVE_IOREMAP_PROT
 196         bool
 197
 198 config HAVE_KPROBES
 199         bool
 200
 201 config HAVE_KRETPROBES
 202         bool
 203
 204 config HAVE_OPTPROBES
 205         bool
 206
 207 config HAVE_KPROBES_ON_FTRACE
 208         bool
 209
 210 config HAVE_FUNCTION_ERROR_INJECTION
 211         bool
 212
 213 config HAVE_NMI
 214         bool
 215
 216 #
 217 # An arch should select this if it provides all these things:
 218 #
 219 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 220 #       arch_has_single_step()  if there is hardware single-step support
 221 #       arch_has_block_step()   if there is hardware block-step support
 222 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 223 #       linux/regset.h          user_regset interfaces
 224 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 225 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 226 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 227 #       signal delivery         calls tracehook_signal_handler()
 228 #
 229 config HAVE_ARCH_TRACEHOOK
 230         bool
 231
 232 config HAVE_DMA_CONTIGUOUS
 233         bool
 234
 235 config GENERIC_SMP_IDLE_THREAD
 236         bool
 237
 238 config GENERIC_IDLE_POLL_SETUP
 239         bool
 240
 241 config ARCH_HAS_FORTIFY_SOURCE
 242         bool
 243         help
 244           An architecture should select this when it can successfully
 245           build and run with CONFIG_FORTIFY_SOURCE.
 246
 247 #
 248 # Select if the arch provides a historic keepinit alias for the retain_initrd
 249 # command line option
 250 #
 251 config ARCH_HAS_KEEPINITRD
 252         bool
 253
 254 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 255 config ARCH_HAS_SET_MEMORY
 256         bool
 257
 258 # Select if arch has all set_direct_map_invalid/default() functions
 259 config ARCH_HAS_SET_DIRECT_MAP
 260         bool
 261
 262 #
 263 # Select if the architecture provides the arch_dma_set_uncached symbol to
 264 # either provide an uncached segement alias for a DMA allocation, or
 265 # to remap the page tables in place.
 266 #
 267 config ARCH_HAS_DMA_SET_UNCACHED
 268         bool
 269
 270 #
 271 # Select if the architectures provides the arch_dma_clear_uncached symbol
 272 # to undo an in-place page table remap for uncached access.
 273 #
 274 config ARCH_HAS_DMA_CLEAR_UNCACHED
 275         bool
 276
 277 # Select if arch init_task must go in the __init_task_data section
 278 config ARCH_TASK_STRUCT_ON_STACK
 279         bool
 280
 281 # Select if arch has its private alloc_task_struct() function
 282 config ARCH_TASK_STRUCT_ALLOCATOR
 283         bool
 284
 285 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 286         bool
 287         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 288         help
 289           An architecture should select this to provide hardened usercopy
 290           knowledge about what region of the thread_struct should be
 291           whitelisted for copying to userspace. Normally this is only the
 292           FPU registers. Specifically, arch_thread_struct_whitelist()
 293           should be implemented. Without this, the entire thread_struct
 294           field in task_struct will be left whitelisted.
 295
 296 # Select if arch has its private alloc_thread_stack() function
 297 config ARCH_THREAD_STACK_ALLOCATOR
 298         bool
 299
 300 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 301 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 302         bool
 303
 304 config ARCH_32BIT_OFF_T
 305         bool
 306         depends on !64BIT
 307         help
 308           All new 32-bit architectures should have 64-bit off_t type on
 309           userspace side which corresponds to the loff_t kernel type. This
 310           is the requirement for modern ABIs. Some existing architectures
 311           still support 32-bit off_t. This option is enabled for all such
 312           architectures explicitly.
 313
 314 config HAVE_ASM_MODVERSIONS
 315         bool
 316         help
 317           This symbol should be selected by an architecure if it provides
 318           <asm/asm-prototypes.h> to support the module versioning for symbols
 319           exported from assembly code.
 320
 321 config HAVE_REGS_AND_STACK_ACCESS_API
 322         bool
 323         help
 324           This symbol should be selected by an architecure if it supports
 325           the API needed to access registers and stack entries from pt_regs,
 326           declared in asm/ptrace.h
 327           For example the kprobes-based event tracer needs this API.
 328
 329 config HAVE_RSEQ
 330         bool
 331         depends on HAVE_REGS_AND_STACK_ACCESS_API
 332         help
 333           This symbol should be selected by an architecture if it
 334           supports an implementation of restartable sequences.
 335
 336 config HAVE_FUNCTION_ARG_ACCESS_API
 337         bool
 338         help
 339           This symbol should be selected by an architecure if it supports
 340           the API needed to access function arguments from pt_regs,
 341           declared in asm/ptrace.h
 342
 343 config HAVE_HW_BREAKPOINT
 344         bool
 345         depends on PERF_EVENTS
 346
 347 config HAVE_MIXED_BREAKPOINTS_REGS
 348         bool
 349         depends on HAVE_HW_BREAKPOINT
 350         help
 351           Depending on the arch implementation of hardware breakpoints,
 352           some of them have separate registers for data and instruction
 353           breakpoints addresses, others have mixed registers to store
 354           them but define the access type in a control register.
 355           Select this option if your arch implements breakpoints under the
 356           latter fashion.
 357
 358 config HAVE_USER_RETURN_NOTIFIER
 359         bool
 360
 361 config HAVE_PERF_EVENTS_NMI
 362         bool
 363         help
 364           System hardware can generate an NMI using the perf event
 365           subsystem.  Also has support for calculating CPU cycle events
 366           to determine how many clock cycles in a given period.
 367
 368 config HAVE_HARDLOCKUP_DETECTOR_PERF
 369         bool
 370         depends on HAVE_PERF_EVENTS_NMI
 371         help
 372           The arch chooses to use the generic perf-NMI-based hardlockup
 373           detector. Must define HAVE_PERF_EVENTS_NMI.
 374
 375 config HAVE_NMI_WATCHDOG
 376         depends on HAVE_NMI
 377         bool
 378         help
 379           The arch provides a low level NMI watchdog. It provides
 380           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 381
 382 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 383         bool
 384         select HAVE_NMI_WATCHDOG
 385         help
 386           The arch chooses to provide its own hardlockup detector, which is
 387           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 388           interfaces and parameters provided by hardlockup detector subsystem.
 389
 390 config HAVE_PERF_REGS
 391         bool
 392         help
 393           Support selective register dumps for perf events. This includes
 394           bit-mapping of each registers and a unique architecture id.
 395
 396 config HAVE_PERF_USER_STACK_DUMP
 397         bool
 398         help
 399           Support user stack dumps for perf event samples. This needs
 400           access to the user stack pointer which is not unified across
 401           architectures.
 402
 403 config HAVE_ARCH_JUMP_LABEL
 404         bool
 405
 406 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 407         bool
 408
 409 config MMU_GATHER_TABLE_FREE
 410         bool
 411
 412 config MMU_GATHER_RCU_TABLE_FREE
 413         bool
 414         select MMU_GATHER_TABLE_FREE
 415
 416 config MMU_GATHER_PAGE_SIZE
 417         bool
 418
 419 config MMU_GATHER_NO_RANGE
 420         bool
 421
 422 config MMU_GATHER_NO_GATHER
 423         bool
 424         depends on MMU_GATHER_TABLE_FREE
 425
 426 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 427         bool
 428         help
 429           Temporary select until all architectures can be converted to have
 430           irqs disabled over activate_mm. Architectures that do IPI based TLB
 431           shootdowns should enable this.
 432
 433 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 434         bool
 435
 436 config HAVE_ALIGNED_STRUCT_PAGE
 437         bool
 438         help
 439           This makes sure that struct pages are double word aligned and that
 440           e.g. the SLUB allocator can perform double word atomic operations
 441           on a struct page for better performance. However selecting this
 442           might increase the size of a struct page by a word.
 443
 444 config HAVE_CMPXCHG_LOCAL
 445         bool
 446
 447 config HAVE_CMPXCHG_DOUBLE
 448         bool
 449
 450 config ARCH_WEAK_RELEASE_ACQUIRE
 451         bool
 452
 453 config ARCH_WANT_IPC_PARSE_VERSION
 454         bool
 455
 456 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 457         bool
 458
 459 config ARCH_WANT_OLD_COMPAT_IPC
 460         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 461         bool
 462
 463 config HAVE_ARCH_SECCOMP
 464         bool
 465         help
 466           An arch should select this symbol to support seccomp mode 1 (the fixed
 467           syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 468           and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 469           - __NR_seccomp_read_32
 470           - __NR_seccomp_write_32
 471           - __NR_seccomp_exit_32
 472           - __NR_seccomp_sigreturn_32
 473
 474 config HAVE_ARCH_SECCOMP_FILTER
 475         bool
 476         select HAVE_ARCH_SECCOMP
 477         help
 478           An arch should select this symbol if it provides all of these things:
 479           - all the requirements for HAVE_ARCH_SECCOMP
 480           - syscall_get_arch()
 481           - syscall_get_arguments()
 482           - syscall_rollback()
 483           - syscall_set_return_value()
 484           - SIGSYS siginfo_t support
 485           - secure_computing is called from a ptrace_event()-safe context
 486           - secure_computing return value is checked and a return value of -1
 487             results in the system call being skipped immediately.
 488           - seccomp syscall wired up
 489
 490 config SECCOMP
 491         prompt "Enable seccomp to safely execute untrusted bytecode"
 492         def_bool y
 493         depends on HAVE_ARCH_SECCOMP
 494         help
 495           This kernel feature is useful for number crunching applications
 496           that may need to handle untrusted bytecode during their
 497           execution. By using pipes or other transports made available
 498           to the process as file descriptors supporting the read/write
 499           syscalls, it's possible to isolate those applications in their
 500           own address space using seccomp. Once seccomp is enabled via
 501           prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 502           disabled and the task is only allowed to execute a few safe
 503           syscalls defined by each seccomp mode.
 504
 505           If unsure, say Y.
 506
 507 config SECCOMP_FILTER
 508         def_bool y
 509         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 510         help
 511           Enable tasks to build secure computing environments defined
 512           in terms of Berkeley Packet Filter programs which implement
 513           task-defined system call filtering polices.
 514
 515           See Documentation/userspace-api/seccomp_filter.rst for details.
 516
 517 config HAVE_ARCH_STACKLEAK
 518         bool
 519         help
 520           An architecture should select this if it has the code which
 521           fills the used part of the kernel stack with the STACKLEAK_POISON
 522           value before returning from system calls.
 523
 524 config HAVE_STACKPROTECTOR
 525         bool
 526         help
 527           An arch should select this symbol if:
 528           - it has implemented a stack canary (e.g. __stack_chk_guard)
 529
 530 config STACKPROTECTOR
 531         bool "Stack Protector buffer overflow detection"
 532         depends on HAVE_STACKPROTECTOR
 533         depends on $(cc-option,-fstack-protector)
 534         default y
 535         help
 536           This option turns on the "stack-protector" GCC feature. This
 537           feature puts, at the beginning of functions, a canary value on
 538           the stack just before the return address, and validates
 539           the value just before actually returning.  Stack based buffer
 540           overflows (that need to overwrite this return address) now also
 541           overwrite the canary, which gets detected and the attack is then
 542           neutralized via a kernel panic.
 543
 544           Functions will have the stack-protector canary logic added if they
 545           have an 8-byte or larger character array on the stack.
 546
 547           This feature requires gcc version 4.2 or above, or a distribution
 548           gcc with the feature backported ("-fstack-protector").
 549
 550           On an x86 "defconfig" build, this feature adds canary checks to
 551           about 3% of all kernel functions, which increases kernel code size
 552           by about 0.3%.
 553
 554 config STACKPROTECTOR_STRONG
 555         bool "Strong Stack Protector"
 556         depends on STACKPROTECTOR
 557         depends on $(cc-option,-fstack-protector-strong)
 558         default y
 559         help
 560           Functions will have the stack-protector canary logic added in any
 561           of the following conditions:
 562
 563           - local variable's address used as part of the right hand side of an
 564             assignment or function argument
 565           - local variable is an array (or union containing an array),
 566             regardless of array type or length
 567           - uses register local variables
 568
 569           This feature requires gcc version 4.9 or above, or a distribution
 570           gcc with the feature backported ("-fstack-protector-strong").
 571
 572           On an x86 "defconfig" build, this feature adds canary checks to
 573           about 20% of all kernel functions, which increases the kernel code
 574           size by about 2%.
 575
 576 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 577         bool
 578         help
 579           An architecture should select this if it supports Clang's Shadow
 580           Call Stack and implements runtime support for shadow stack
 581           switching.
 582
 583 config SHADOW_CALL_STACK
 584         bool "Clang Shadow Call Stack"
 585         depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
 586         depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 587         help
 588           This option enables Clang's Shadow Call Stack, which uses a
 589           shadow stack to protect function return addresses from being
 590           overwritten by an attacker. More information can be found in
 591           Clang's documentation:
 592
 593             https://clang.llvm.org/docs/ShadowCallStack.html
 594
 595           Note that security guarantees in the kernel differ from the
 596           ones documented for user space. The kernel must store addresses
 597           of shadow stacks in memory, which means an attacker capable of
 598           reading and writing arbitrary memory may be able to locate them
 599           and hijack control flow by modifying the stacks.
 600
 601 config HAVE_ARCH_WITHIN_STACK_FRAMES
 602         bool
 603         help
 604           An architecture should select this if it can walk the kernel stack
 605           frames to determine if an object is part of either the arguments
 606           or local variables (i.e. that it excludes saved return addresses,
 607           and similar) by implementing an inline arch_within_stack_frames(),
 608           which is used by CONFIG_HARDENED_USERCOPY.
 609
 610 config HAVE_CONTEXT_TRACKING
 611         bool
 612         help
 613           Provide kernel/user boundaries probes necessary for subsystems
 614           that need it, such as userspace RCU extended quiescent state.
 615           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 616           optimized behind static key or through the slow path using TIF_NOHZ
 617           flag. Exceptions handlers must be wrapped as well. Irqs are already
 618           protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
 619           handling on irq exit still need to be protected.
 620
 621 config HAVE_TIF_NOHZ
 622         bool
 623         help
 624           Arch relies on TIF_NOHZ and syscall slow path to implement context
 625           tracking calls to user_enter()/user_exit().
 626
 627 config HAVE_VIRT_CPU_ACCOUNTING
 628         bool
 629
 630 config ARCH_HAS_SCALED_CPUTIME
 631         bool
 632
 633 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 634         bool
 635         default y if 64BIT
 636         help
 637           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 638           Before enabling this option, arch code must be audited
 639           to ensure there are no races in concurrent read/write of
 640           cputime_t. For example, reading/writing 64-bit cputime_t on
 641           some 32-bit arches may require multiple accesses, so proper
 642           locking is needed to protect against concurrent accesses.
 643
 644
 645 config HAVE_IRQ_TIME_ACCOUNTING
 646         bool
 647         help
 648           Archs need to ensure they use a high enough resolution clock to
 649           support irq time accounting and then call enable_sched_clock_irqtime().
 650
 651 config HAVE_MOVE_PMD
 652         bool
 653         help
 654           Archs that select this are able to move page tables at the PMD level.
 655
 656 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 657         bool
 658
 659 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 660         bool
 661
 662 config HAVE_ARCH_HUGE_VMAP
 663         bool
 664
 665 config ARCH_WANT_HUGE_PMD_SHARE
 666         bool
 667
 668 config HAVE_ARCH_SOFT_DIRTY
 669         bool
 670
 671 config HAVE_MOD_ARCH_SPECIFIC
 672         bool
 673         help
 674           The arch uses struct mod_arch_specific to store data.  Many arches
 675           just need a simple module loader without arch specific data - those
 676           should not enable this.
 677
 678 config MODULES_USE_ELF_RELA
 679         bool
 680         help
 681           Modules only use ELF RELA relocations.  Modules with ELF REL
 682           relocations will give an error.
 683
 684 config MODULES_USE_ELF_REL
 685         bool
 686         help
 687           Modules only use ELF REL relocations.  Modules with ELF RELA
 688           relocations will give an error.
 689
 690 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 691         bool
 692         help
 693           Architecture doesn't only execute the irq handler on the irq stack
 694           but also irq_exit(). This way we can process softirqs on this irq
 695           stack instead of switching to a new one when we call __do_softirq()
 696           in the end of an hardirq.
 697           This spares a stack switch and improves cache usage on softirq
 698           processing.
 699
 700 config PGTABLE_LEVELS
 701         int
 702         default 2
 703
 704 config ARCH_HAS_ELF_RANDOMIZE
 705         bool
 706         help
 707           An architecture supports choosing randomized locations for
 708           stack, mmap, brk, and ET_DYN. Defined functions:
 709           - arch_mmap_rnd()
 710           - arch_randomize_brk()
 711
 712 config HAVE_ARCH_MMAP_RND_BITS
 713         bool
 714         help
 715           An arch should select this symbol if it supports setting a variable
 716           number of bits for use in establishing the base address for mmap
 717           allocations, has MMU enabled and provides values for both:
 718           - ARCH_MMAP_RND_BITS_MIN
 719           - ARCH_MMAP_RND_BITS_MAX
 720
 721 config HAVE_EXIT_THREAD
 722         bool
 723         help
 724           An architecture implements exit_thread.
 725
 726 config ARCH_MMAP_RND_BITS_MIN
 727         int
 728
 729 config ARCH_MMAP_RND_BITS_MAX
 730         int
 731
 732 config ARCH_MMAP_RND_BITS_DEFAULT
 733         int
 734
 735 config ARCH_MMAP_RND_BITS
 736         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 737         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 738         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 739         default ARCH_MMAP_RND_BITS_MIN
 740         depends on HAVE_ARCH_MMAP_RND_BITS
 741         help
 742           This value can be used to select the number of bits to use to
 743           determine the random offset to the base address of vma regions
 744           resulting from mmap allocations. This value will be bounded
 745           by the architecture's minimum and maximum supported values.
 746
 747           This value can be changed after boot using the
 748           /proc/sys/vm/mmap_rnd_bits tunable
 749
 750 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 751         bool
 752         help
 753           An arch should select this symbol if it supports running applications
 754           in compatibility mode, supports setting a variable number of bits for
 755           use in establishing the base address for mmap allocations, has MMU
 756           enabled and provides values for both:
 757           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 758           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 759
 760 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 761         int
 762
 763 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 764         int
 765
 766 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 767         int
 768
 769 config ARCH_MMAP_RND_COMPAT_BITS
 770         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 771         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 772         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 773         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 774         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 775         help
 776           This value can be used to select the number of bits to use to
 777           determine the random offset to the base address of vma regions
 778           resulting from mmap allocations for compatible applications This
 779           value will be bounded by the architecture's minimum and maximum
 780           supported values.
 781
 782           This value can be changed after boot using the
 783           /proc/sys/vm/mmap_rnd_compat_bits tunable
 784
 785 config HAVE_ARCH_COMPAT_MMAP_BASES
 786         bool
 787         help
 788           This allows 64bit applications to invoke 32-bit mmap() syscall
 789           and vice-versa 32-bit applications to call 64-bit mmap().
 790           Required for applications doing different bitness syscalls.
 791
 792 # This allows to use a set of generic functions to determine mmap base
 793 # address by giving priority to top-down scheme only if the process
 794 # is not in legacy mode (compat task, unlimited stack size or
 795 # sysctl_legacy_va_layout).
 796 # Architecture that selects this option can provide its own version of:
 797 # - STACK_RND_MASK
 798 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 799         bool
 800         depends on MMU
 801         select ARCH_HAS_ELF_RANDOMIZE
 802
 803 config HAVE_STACK_VALIDATION
 804         bool
 805         help
 806           Architecture supports the 'objtool check' host tool command, which
 807           performs compile-time stack metadata validation.
 808
 809 config HAVE_RELIABLE_STACKTRACE
 810         bool
 811         help
 812           Architecture has either save_stack_trace_tsk_reliable() or
 813           arch_stack_walk_reliable() function which only returns a stack trace
 814           if it can guarantee the trace is reliable.
 815
 816 config HAVE_ARCH_HASH
 817         bool
 818         default n
 819         help
 820           If this is set, the architecture provides an <asm/hash.h>
 821           file which provides platform-specific implementations of some
 822           functions in <linux/hash.h> or fs/namei.c.
 823
 824 config HAVE_ARCH_NVRAM_OPS
 825         bool
 826
 827 config ISA_BUS_API
 828         def_bool ISA
 829
 830 #
 831 # ABI hall of shame
 832 #
 833 config CLONE_BACKWARDS
 834         bool
 835         help
 836           Architecture has tls passed as the 4th argument of clone(2),
 837           not the 5th one.
 838
 839 config CLONE_BACKWARDS2
 840         bool
 841         help
 842           Architecture has the first two arguments of clone(2) swapped.
 843
 844 config CLONE_BACKWARDS3
 845         bool
 846         help
 847           Architecture has tls passed as the 3rd argument of clone(2),
 848           not the 5th one.
 849
 850 config ODD_RT_SIGACTION
 851         bool
 852         help
 853           Architecture has unusual rt_sigaction(2) arguments
 854
 855 config OLD_SIGSUSPEND
 856         bool
 857         help
 858           Architecture has old sigsuspend(2) syscall, of one-argument variety
 859
 860 config OLD_SIGSUSPEND3
 861         bool
 862         help
 863           Even weirder antique ABI - three-argument sigsuspend(2)
 864
 865 config OLD_SIGACTION
 866         bool
 867         help
 868           Architecture has old sigaction(2) syscall.  Nope, not the same
 869           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 870           but fairly different variant of sigaction(2), thanks to OSF/1
 871           compatibility...
 872
 873 config COMPAT_OLD_SIGACTION
 874         bool
 875
 876 config COMPAT_32BIT_TIME
 877         bool "Provide system calls for 32-bit time_t"
 878         default !64BIT || COMPAT
 879         help
 880           This enables 32 bit time_t support in addition to 64 bit time_t support.
 881           This is relevant on all 32-bit architectures, and 64-bit architectures
 882           as part of compat syscall handling.
 883
 884 config ARCH_NO_PREEMPT
 885         bool
 886
 887 config ARCH_SUPPORTS_RT
 888         bool
 889
 890 config CPU_NO_EFFICIENT_FFS
 891         def_bool n
 892
 893 config HAVE_ARCH_VMAP_STACK
 894         def_bool n
 895         help
 896           An arch should select this symbol if it can support kernel stacks
 897           in vmalloc space.  This means:
 898
 899           - vmalloc space must be large enough to hold many kernel stacks.
 900             This may rule out many 32-bit architectures.
 901
 902           - Stacks in vmalloc space need to work reliably.  For example, if
 903             vmap page tables are created on demand, either this mechanism
 904             needs to work while the stack points to a virtual address with
 905             unpopulated page tables or arch code (switch_to() and switch_mm(),
 906             most likely) needs to ensure that the stack's page table entries
 907             are populated before running on a possibly unpopulated stack.
 908
 909           - If the stack overflows into a guard page, something reasonable
 910             should happen.  The definition of "reasonable" is flexible, but
 911             instantly rebooting without logging anything would be unfriendly.
 912
 913 config VMAP_STACK
 914         default y
 915         bool "Use a virtually-mapped stack"
 916         depends on HAVE_ARCH_VMAP_STACK
 917         depends on !KASAN || KASAN_VMALLOC
 918         help
 919           Enable this if you want the use virtually-mapped kernel stacks
 920           with guard pages.  This causes kernel stack overflows to be
 921           caught immediately rather than causing difficult-to-diagnose
 922           corruption.
 923
 924           To use this with KASAN, the architecture must support backing
 925           virtual mappings with real shadow memory, and KASAN_VMALLOC must
 926           be enabled.
 927
 928 config ARCH_OPTIONAL_KERNEL_RWX
 929         def_bool n
 930
 931 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 932         def_bool n
 933
 934 config ARCH_HAS_STRICT_KERNEL_RWX
 935         def_bool n
 936
 937 config STRICT_KERNEL_RWX
 938         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 939         depends on ARCH_HAS_STRICT_KERNEL_RWX
 940         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 941         help
 942           If this is set, kernel text and rodata memory will be made read-only,
 943           and non-text memory will be made non-executable. This provides
 944           protection against certain security exploits (e.g. executing the heap
 945           or modifying text)
 946
 947           These features are considered standard security practice these days.
 948           You should say Y here in almost all cases.
 949
 950 config ARCH_HAS_STRICT_MODULE_RWX
 951         def_bool n
 952
 953 config STRICT_MODULE_RWX
 954         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 955         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 956         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 957         help
 958           If this is set, module text and rodata memory will be made read-only,
 959           and non-text memory will be made non-executable. This provides
 960           protection against certain security exploits (e.g. writing to text)
 961
 962 # select if the architecture provides an asm/dma-direct.h header
 963 config ARCH_HAS_PHYS_TO_DMA
 964         bool
 965
 966 config HAVE_ARCH_COMPILER_H
 967         bool
 968         help
 969           An architecture can select this if it provides an
 970           asm/compiler.h header that should be included after
 971           linux/compiler-*.h in order to override macro definitions that those
 972           headers generally provide.
 973
 974 config HAVE_ARCH_PREL32_RELOCATIONS
 975         bool
 976         help
 977           May be selected by an architecture if it supports place-relative
 978           32-bit relocations, both in the toolchain and in the module loader,
 979           in which case relative references can be used in special sections
 980           for PCI fixup, initcalls etc which are only half the size on 64 bit
 981           architectures, and don't require runtime relocation on relocatable
 982           kernels.
 983
 984 config ARCH_USE_MEMREMAP_PROT
 985         bool
 986
 987 config LOCK_EVENT_COUNTS
 988         bool "Locking event counts collection"
 989         depends on DEBUG_FS
 990         help
 991           Enable light-weight counting of various locking related events
 992           in the system with minimal performance impact. This reduces
 993           the chance of application behavior change because of timing
 994           differences. The counts are reported via debugfs.
 995
 996 # Select if the architecture has support for applying RELR relocations.
 997 config ARCH_HAS_RELR
 998         bool
 999
1000 config RELR
1001         bool "Use RELR relocation packing"
1002         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1003         default y
1004         help
1005           Store the kernel's dynamic relocations in the RELR relocation packing
1006           format. Requires a compatible linker (LLD supports this feature), as
1007           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1008           are compatible).
1009
1010 config ARCH_HAS_MEM_ENCRYPT
1011         bool
1012
1013 config HAVE_SPARSE_SYSCALL_NR
1014        bool
1015        help
1016           An architecture should select this if its syscall numbering is sparse
1017           to save space. For example, MIPS architecture has a syscall array with
1018           entries at 4000, 5000 and 6000 locations. This option turns on syscall
1019           related optimizations for a given architecture.
1020
1021 config ARCH_HAS_VDSO_DATA
1022         bool
1023
1024 config HAVE_STATIC_CALL
1025         bool
1026
1027 config HAVE_STATIC_CALL_INLINE
1028         bool
1029         depends on HAVE_STATIC_CALL
1030
1031 source "kernel/gcov/Kconfig"
1032
1033 source "scripts/gcc-plugins/Kconfig"
1034
1035 endmenu