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 ARCH_HAS_SUBPAGE_FAULTS
  15         bool
  16         help
  17           Select if the architecture can check permissions at sub-page
  18           granularity (e.g. arm64 MTE). The probe_user_*() functions
  19           must be implemented.
  20
  21 config HOTPLUG_SMT
  22         bool
  23
  24 config SMT_NUM_THREADS_DYNAMIC
  25         bool
  26
  27 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
  28 config HOTPLUG_CORE_SYNC
  29         bool
  30
  31 # Basic CPU dead synchronization selected by architecture
  32 config HOTPLUG_CORE_SYNC_DEAD
  33         bool
  34         select HOTPLUG_CORE_SYNC
  35
  36 # Full CPU synchronization with alive state selected by architecture
  37 config HOTPLUG_CORE_SYNC_FULL
  38         bool
  39         select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
  40         select HOTPLUG_CORE_SYNC
  41
  42 config HOTPLUG_SPLIT_STARTUP
  43         bool
  44         select HOTPLUG_CORE_SYNC_FULL
  45
  46 config HOTPLUG_PARALLEL
  47         bool
  48         select HOTPLUG_SPLIT_STARTUP
  49
  50 config GENERIC_ENTRY
  51         bool
  52
  53 config KPROBES
  54         bool "Kprobes"
  55         depends on MODULES
  56         depends on HAVE_KPROBES
  57         select KALLSYMS
  58         select TASKS_RCU if PREEMPTION
  59         help
  60           Kprobes allows you to trap at almost any kernel address and
  61           execute a callback function.  register_kprobe() establishes
  62           a probepoint and specifies the callback.  Kprobes is useful
  63           for kernel debugging, non-intrusive instrumentation and testing.
  64           If in doubt, say "N".
  65
  66 config JUMP_LABEL
  67         bool "Optimize very unlikely/likely branches"
  68         depends on HAVE_ARCH_JUMP_LABEL
  69         select OBJTOOL if HAVE_JUMP_LABEL_HACK
  70         help
  71           This option enables a transparent branch optimization that
  72           makes certain almost-always-true or almost-always-false branch
  73           conditions even cheaper to execute within the kernel.
  74
  75           Certain performance-sensitive kernel code, such as trace points,
  76           scheduler functionality, networking code and KVM have such
  77           branches and include support for this optimization technique.
  78
  79           If it is detected that the compiler has support for "asm goto",
  80           the kernel will compile such branches with just a nop
  81           instruction. When the condition flag is toggled to true, the
  82           nop will be converted to a jump instruction to execute the
  83           conditional block of instructions.
  84
  85           This technique lowers overhead and stress on the branch prediction
  86           of the processor and generally makes the kernel faster. The update
  87           of the condition is slower, but those are always very rare.
  88
  89           ( On 32-bit x86, the necessary options added to the compiler
  90             flags may increase the size of the kernel slightly. )
  91
  92 config STATIC_KEYS_SELFTEST
  93         bool "Static key selftest"
  94         depends on JUMP_LABEL
  95         help
  96           Boot time self-test of the branch patching code.
  97
  98 config STATIC_CALL_SELFTEST
  99         bool "Static call selftest"
 100         depends on HAVE_STATIC_CALL
 101         help
 102           Boot time self-test of the call patching code.
 103
 104 config OPTPROBES
 105         def_bool y
 106         depends on KPROBES && HAVE_OPTPROBES
 107         select TASKS_RCU if PREEMPTION
 108
 109 config KPROBES_ON_FTRACE
 110         def_bool y
 111         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 112         depends on DYNAMIC_FTRACE_WITH_REGS
 113         help
 114           If function tracer is enabled and the arch supports full
 115           passing of pt_regs to function tracing, then kprobes can
 116           optimize on top of function tracing.
 117
 118 config UPROBES
 119         def_bool n
 120         depends on ARCH_SUPPORTS_UPROBES
 121         help
 122           Uprobes is the user-space counterpart to kprobes: they
 123           enable instrumentation applications (such as 'perf probe')
 124           to establish unintrusive probes in user-space binaries and
 125           libraries, by executing handler functions when the probes
 126           are hit by user-space applications.
 127
 128           ( These probes come in the form of single-byte breakpoints,
 129             managed by the kernel and kept transparent to the probed
 130             application. )
 131
 132 config HAVE_64BIT_ALIGNED_ACCESS
 133         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 134         help
 135           Some architectures require 64 bit accesses to be 64 bit
 136           aligned, which also requires structs containing 64 bit values
 137           to be 64 bit aligned too. This includes some 32 bit
 138           architectures which can do 64 bit accesses, as well as 64 bit
 139           architectures without unaligned access.
 140
 141           This symbol should be selected by an architecture if 64 bit
 142           accesses are required to be 64 bit aligned in this way even
 143           though it is not a 64 bit architecture.
 144
 145           See Documentation/core-api/unaligned-memory-access.rst for
 146           more information on the topic of unaligned memory accesses.
 147
 148 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 149         bool
 150         help
 151           Some architectures are unable to perform unaligned accesses
 152           without the use of get_unaligned/put_unaligned. Others are
 153           unable to perform such accesses efficiently (e.g. trap on
 154           unaligned access and require fixing it up in the exception
 155           handler.)
 156
 157           This symbol should be selected by an architecture if it can
 158           perform unaligned accesses efficiently to allow different
 159           code paths to be selected for these cases. Some network
 160           drivers, for example, could opt to not fix up alignment
 161           problems with received packets if doing so would not help
 162           much.
 163
 164           See Documentation/core-api/unaligned-memory-access.rst for more
 165           information on the topic of unaligned memory accesses.
 166
 167 config ARCH_USE_BUILTIN_BSWAP
 168         bool
 169         help
 170           Modern versions of GCC (since 4.4) have builtin functions
 171           for handling byte-swapping. Using these, instead of the old
 172           inline assembler that the architecture code provides in the
 173           __arch_bswapXX() macros, allows the compiler to see what's
 174           happening and offers more opportunity for optimisation. In
 175           particular, the compiler will be able to combine the byteswap
 176           with a nearby load or store and use load-and-swap or
 177           store-and-swap instructions if the architecture has them. It
 178           should almost *never* result in code which is worse than the
 179           hand-coded assembler in <asm/swab.h>.  But just in case it
 180           does, the use of the builtins is optional.
 181
 182           Any architecture with load-and-swap or store-and-swap
 183           instructions should set this. And it shouldn't hurt to set it
 184           on architectures that don't have such instructions.
 185
 186 config KRETPROBES
 187         def_bool y
 188         depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
 189
 190 config KRETPROBE_ON_RETHOOK
 191         def_bool y
 192         depends on HAVE_RETHOOK
 193         depends on KRETPROBES
 194         select RETHOOK
 195
 196 config USER_RETURN_NOTIFIER
 197         bool
 198         depends on HAVE_USER_RETURN_NOTIFIER
 199         help
 200           Provide a kernel-internal notification when a cpu is about to
 201           switch to user mode.
 202
 203 config HAVE_IOREMAP_PROT
 204         bool
 205
 206 config HAVE_KPROBES
 207         bool
 208
 209 config HAVE_KRETPROBES
 210         bool
 211
 212 config HAVE_OPTPROBES
 213         bool
 214
 215 config HAVE_KPROBES_ON_FTRACE
 216         bool
 217
 218 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
 219         bool
 220         help
 221           Since kretprobes modifies return address on the stack, the
 222           stacktrace may see the kretprobe trampoline address instead
 223           of correct one. If the architecture stacktrace code and
 224           unwinder can adjust such entries, select this configuration.
 225
 226 config HAVE_FUNCTION_ERROR_INJECTION
 227         bool
 228
 229 config HAVE_NMI
 230         bool
 231
 232 config HAVE_FUNCTION_DESCRIPTORS
 233         bool
 234
 235 config TRACE_IRQFLAGS_SUPPORT
 236         bool
 237
 238 config TRACE_IRQFLAGS_NMI_SUPPORT
 239         bool
 240
 241 #
 242 # An arch should select this if it provides all these things:
 243 #
 244 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 245 #       arch_has_single_step()  if there is hardware single-step support
 246 #       arch_has_block_step()   if there is hardware block-step support
 247 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 248 #       linux/regset.h          user_regset interfaces
 249 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 250 #       TIF_SYSCALL_TRACE       calls ptrace_report_syscall_{entry,exit}
 251 #       TIF_NOTIFY_RESUME       calls resume_user_mode_work()
 252 #
 253 config HAVE_ARCH_TRACEHOOK
 254         bool
 255
 256 config HAVE_DMA_CONTIGUOUS
 257         bool
 258
 259 config GENERIC_SMP_IDLE_THREAD
 260         bool
 261
 262 config GENERIC_IDLE_POLL_SETUP
 263         bool
 264
 265 config ARCH_HAS_FORTIFY_SOURCE
 266         bool
 267         help
 268           An architecture should select this when it can successfully
 269           build and run with CONFIG_FORTIFY_SOURCE.
 270
 271 #
 272 # Select if the arch provides a historic keepinit alias for the retain_initrd
 273 # command line option
 274 #
 275 config ARCH_HAS_KEEPINITRD
 276         bool
 277
 278 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 279 config ARCH_HAS_SET_MEMORY
 280         bool
 281
 282 # Select if arch has all set_direct_map_invalid/default() functions
 283 config ARCH_HAS_SET_DIRECT_MAP
 284         bool
 285
 286 #
 287 # Select if the architecture provides the arch_dma_set_uncached symbol to
 288 # either provide an uncached segment alias for a DMA allocation, or
 289 # to remap the page tables in place.
 290 #
 291 config ARCH_HAS_DMA_SET_UNCACHED
 292         bool
 293
 294 #
 295 # Select if the architectures provides the arch_dma_clear_uncached symbol
 296 # to undo an in-place page table remap for uncached access.
 297 #
 298 config ARCH_HAS_DMA_CLEAR_UNCACHED
 299         bool
 300
 301 config ARCH_HAS_CPU_FINALIZE_INIT
 302         bool
 303
 304 # Select if arch init_task must go in the __init_task_data section
 305 config ARCH_TASK_STRUCT_ON_STACK
 306         bool
 307
 308 # Select if arch has its private alloc_task_struct() function
 309 config ARCH_TASK_STRUCT_ALLOCATOR
 310         bool
 311
 312 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 313         bool
 314         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 315         help
 316           An architecture should select this to provide hardened usercopy
 317           knowledge about what region of the thread_struct should be
 318           whitelisted for copying to userspace. Normally this is only the
 319           FPU registers. Specifically, arch_thread_struct_whitelist()
 320           should be implemented. Without this, the entire thread_struct
 321           field in task_struct will be left whitelisted.
 322
 323 # Select if arch has its private alloc_thread_stack() function
 324 config ARCH_THREAD_STACK_ALLOCATOR
 325         bool
 326
 327 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 328 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 329         bool
 330
 331 config ARCH_WANTS_NO_INSTR
 332         bool
 333         help
 334           An architecture should select this if the noinstr macro is being used on
 335           functions to denote that the toolchain should avoid instrumenting such
 336           functions and is required for correctness.
 337
 338 config ARCH_32BIT_OFF_T
 339         bool
 340         depends on !64BIT
 341         help
 342           All new 32-bit architectures should have 64-bit off_t type on
 343           userspace side which corresponds to the loff_t kernel type. This
 344           is the requirement for modern ABIs. Some existing architectures
 345           still support 32-bit off_t. This option is enabled for all such
 346           architectures explicitly.
 347
 348 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
 349 config ARCH_32BIT_USTAT_F_TINODE
 350         bool
 351
 352 config HAVE_ASM_MODVERSIONS
 353         bool
 354         help
 355           This symbol should be selected by an architecture if it provides
 356           <asm/asm-prototypes.h> to support the module versioning for symbols
 357           exported from assembly code.
 358
 359 config HAVE_REGS_AND_STACK_ACCESS_API
 360         bool
 361         help
 362           This symbol should be selected by an architecture if it supports
 363           the API needed to access registers and stack entries from pt_regs,
 364           declared in asm/ptrace.h
 365           For example the kprobes-based event tracer needs this API.
 366
 367 config HAVE_RSEQ
 368         bool
 369         depends on HAVE_REGS_AND_STACK_ACCESS_API
 370         help
 371           This symbol should be selected by an architecture if it
 372           supports an implementation of restartable sequences.
 373
 374 config HAVE_RUST
 375         bool
 376         help
 377           This symbol should be selected by an architecture if it
 378           supports Rust.
 379
 380 config HAVE_FUNCTION_ARG_ACCESS_API
 381         bool
 382         help
 383           This symbol should be selected by an architecture if it supports
 384           the API needed to access function arguments from pt_regs,
 385           declared in asm/ptrace.h
 386
 387 config HAVE_HW_BREAKPOINT
 388         bool
 389         depends on PERF_EVENTS
 390
 391 config HAVE_MIXED_BREAKPOINTS_REGS
 392         bool
 393         depends on HAVE_HW_BREAKPOINT
 394         help
 395           Depending on the arch implementation of hardware breakpoints,
 396           some of them have separate registers for data and instruction
 397           breakpoints addresses, others have mixed registers to store
 398           them but define the access type in a control register.
 399           Select this option if your arch implements breakpoints under the
 400           latter fashion.
 401
 402 config HAVE_USER_RETURN_NOTIFIER
 403         bool
 404
 405 config HAVE_PERF_EVENTS_NMI
 406         bool
 407         help
 408           System hardware can generate an NMI using the perf event
 409           subsystem.  Also has support for calculating CPU cycle events
 410           to determine how many clock cycles in a given period.
 411
 412 config HAVE_HARDLOCKUP_DETECTOR_PERF
 413         bool
 414         depends on HAVE_PERF_EVENTS_NMI
 415         help
 416           The arch chooses to use the generic perf-NMI-based hardlockup
 417           detector. Must define HAVE_PERF_EVENTS_NMI.
 418
 419 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 420         bool
 421         help
 422           The arch provides its own hardlockup detector implementation instead
 423           of the generic ones.
 424
 425           It uses the same command line parameters, and sysctl interface,
 426           as the generic hardlockup detectors.
 427
 428 config HAVE_PERF_REGS
 429         bool
 430         help
 431           Support selective register dumps for perf events. This includes
 432           bit-mapping of each registers and a unique architecture id.
 433
 434 config HAVE_PERF_USER_STACK_DUMP
 435         bool
 436         help
 437           Support user stack dumps for perf event samples. This needs
 438           access to the user stack pointer which is not unified across
 439           architectures.
 440
 441 config HAVE_ARCH_JUMP_LABEL
 442         bool
 443
 444 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 445         bool
 446
 447 config MMU_GATHER_TABLE_FREE
 448         bool
 449
 450 config MMU_GATHER_RCU_TABLE_FREE
 451         bool
 452         select MMU_GATHER_TABLE_FREE
 453
 454 config MMU_GATHER_PAGE_SIZE
 455         bool
 456
 457 config MMU_GATHER_NO_RANGE
 458         bool
 459         select MMU_GATHER_MERGE_VMAS
 460
 461 config MMU_GATHER_NO_FLUSH_CACHE
 462         bool
 463
 464 config MMU_GATHER_MERGE_VMAS
 465         bool
 466
 467 config MMU_GATHER_NO_GATHER
 468         bool
 469         depends on MMU_GATHER_TABLE_FREE
 470
 471 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 472         bool
 473         help
 474           Temporary select until all architectures can be converted to have
 475           irqs disabled over activate_mm. Architectures that do IPI based TLB
 476           shootdowns should enable this.
 477
 478 # Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
 479 # MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
 480 # to/from kernel threads when the same mm is running on a lot of CPUs (a large
 481 # multi-threaded application), by reducing contention on the mm refcount.
 482 #
 483 # This can be disabled if the architecture ensures no CPUs are using an mm as a
 484 # "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
 485 # or its kernel page tables). This could be arranged by arch_exit_mmap(), or
 486 # final exit(2) TLB flush, for example.
 487 #
 488 # To implement this, an arch *must*:
 489 # Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
 490 # the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
 491 # converted already).
 492 config MMU_LAZY_TLB_REFCOUNT
 493         def_bool y
 494         depends on !MMU_LAZY_TLB_SHOOTDOWN
 495
 496 # This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
 497 # mm as a lazy tlb beyond its last reference count, by shooting down these
 498 # users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
 499 # be using the mm as a lazy tlb, so that they may switch themselves to using
 500 # init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
 501 # may be using mm as a lazy tlb mm.
 502 #
 503 # To implement this, an arch *must*:
 504 # - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
 505 #   at least all possible CPUs in which the mm is lazy.
 506 # - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
 507 config MMU_LAZY_TLB_SHOOTDOWN
 508         bool
 509
 510 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 511         bool
 512
 513 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 514         bool
 515
 516 config HAVE_ALIGNED_STRUCT_PAGE
 517         bool
 518         help
 519           This makes sure that struct pages are double word aligned and that
 520           e.g. the SLUB allocator can perform double word atomic operations
 521           on a struct page for better performance. However selecting this
 522           might increase the size of a struct page by a word.
 523
 524 config HAVE_CMPXCHG_LOCAL
 525         bool
 526
 527 config HAVE_CMPXCHG_DOUBLE
 528         bool
 529
 530 config ARCH_WEAK_RELEASE_ACQUIRE
 531         bool
 532
 533 config ARCH_WANT_IPC_PARSE_VERSION
 534         bool
 535
 536 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 537         bool
 538
 539 config ARCH_WANT_OLD_COMPAT_IPC
 540         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 541         bool
 542
 543 config HAVE_ARCH_SECCOMP
 544         bool
 545         help
 546           An arch should select this symbol to support seccomp mode 1 (the fixed
 547           syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 548           and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 549           - __NR_seccomp_read_32
 550           - __NR_seccomp_write_32
 551           - __NR_seccomp_exit_32
 552           - __NR_seccomp_sigreturn_32
 553
 554 config HAVE_ARCH_SECCOMP_FILTER
 555         bool
 556         select HAVE_ARCH_SECCOMP
 557         help
 558           An arch should select this symbol if it provides all of these things:
 559           - all the requirements for HAVE_ARCH_SECCOMP
 560           - syscall_get_arch()
 561           - syscall_get_arguments()
 562           - syscall_rollback()
 563           - syscall_set_return_value()
 564           - SIGSYS siginfo_t support
 565           - secure_computing is called from a ptrace_event()-safe context
 566           - secure_computing return value is checked and a return value of -1
 567             results in the system call being skipped immediately.
 568           - seccomp syscall wired up
 569           - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
 570             SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
 571             COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
 572
 573 config SECCOMP
 574         prompt "Enable seccomp to safely execute untrusted bytecode"
 575         def_bool y
 576         depends on HAVE_ARCH_SECCOMP
 577         help
 578           This kernel feature is useful for number crunching applications
 579           that may need to handle untrusted bytecode during their
 580           execution. By using pipes or other transports made available
 581           to the process as file descriptors supporting the read/write
 582           syscalls, it's possible to isolate those applications in their
 583           own address space using seccomp. Once seccomp is enabled via
 584           prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 585           disabled and the task is only allowed to execute a few safe
 586           syscalls defined by each seccomp mode.
 587
 588           If unsure, say Y.
 589
 590 config SECCOMP_FILTER
 591         def_bool y
 592         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 593         help
 594           Enable tasks to build secure computing environments defined
 595           in terms of Berkeley Packet Filter programs which implement
 596           task-defined system call filtering polices.
 597
 598           See Documentation/userspace-api/seccomp_filter.rst for details.
 599
 600 config SECCOMP_CACHE_DEBUG
 601         bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
 602         depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
 603         depends on PROC_FS
 604         help
 605           This enables the /proc/pid/seccomp_cache interface to monitor
 606           seccomp cache data. The file format is subject to change. Reading
 607           the file requires CAP_SYS_ADMIN.
 608
 609           This option is for debugging only. Enabling presents the risk that
 610           an adversary may be able to infer the seccomp filter logic.
 611
 612           If unsure, say N.
 613
 614 config HAVE_ARCH_STACKLEAK
 615         bool
 616         help
 617           An architecture should select this if it has the code which
 618           fills the used part of the kernel stack with the STACKLEAK_POISON
 619           value before returning from system calls.
 620
 621 config HAVE_STACKPROTECTOR
 622         bool
 623         help
 624           An arch should select this symbol if:
 625           - it has implemented a stack canary (e.g. __stack_chk_guard)
 626
 627 config STACKPROTECTOR
 628         bool "Stack Protector buffer overflow detection"
 629         depends on HAVE_STACKPROTECTOR
 630         depends on $(cc-option,-fstack-protector)
 631         default y
 632         help
 633           This option turns on the "stack-protector" GCC feature. This
 634           feature puts, at the beginning of functions, a canary value on
 635           the stack just before the return address, and validates
 636           the value just before actually returning.  Stack based buffer
 637           overflows (that need to overwrite this return address) now also
 638           overwrite the canary, which gets detected and the attack is then
 639           neutralized via a kernel panic.
 640
 641           Functions will have the stack-protector canary logic added if they
 642           have an 8-byte or larger character array on the stack.
 643
 644           This feature requires gcc version 4.2 or above, or a distribution
 645           gcc with the feature backported ("-fstack-protector").
 646
 647           On an x86 "defconfig" build, this feature adds canary checks to
 648           about 3% of all kernel functions, which increases kernel code size
 649           by about 0.3%.
 650
 651 config STACKPROTECTOR_STRONG
 652         bool "Strong Stack Protector"
 653         depends on STACKPROTECTOR
 654         depends on $(cc-option,-fstack-protector-strong)
 655         default y
 656         help
 657           Functions will have the stack-protector canary logic added in any
 658           of the following conditions:
 659
 660           - local variable's address used as part of the right hand side of an
 661             assignment or function argument
 662           - local variable is an array (or union containing an array),
 663             regardless of array type or length
 664           - uses register local variables
 665
 666           This feature requires gcc version 4.9 or above, or a distribution
 667           gcc with the feature backported ("-fstack-protector-strong").
 668
 669           On an x86 "defconfig" build, this feature adds canary checks to
 670           about 20% of all kernel functions, which increases the kernel code
 671           size by about 2%.
 672
 673 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 674         bool
 675         help
 676           An architecture should select this if it supports the compiler's
 677           Shadow Call Stack and implements runtime support for shadow stack
 678           switching.
 679
 680 config SHADOW_CALL_STACK
 681         bool "Shadow Call Stack"
 682         depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
 683         depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 684         help
 685           This option enables the compiler's Shadow Call Stack, which
 686           uses a shadow stack to protect function return addresses from
 687           being overwritten by an attacker. More information can be found
 688           in the compiler's documentation:
 689
 690           - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
 691           - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
 692
 693           Note that security guarantees in the kernel differ from the
 694           ones documented for user space. The kernel must store addresses
 695           of shadow stacks in memory, which means an attacker capable of
 696           reading and writing arbitrary memory may be able to locate them
 697           and hijack control flow by modifying the stacks.
 698
 699 config DYNAMIC_SCS
 700         bool
 701         help
 702           Set by the arch code if it relies on code patching to insert the
 703           shadow call stack push and pop instructions rather than on the
 704           compiler.
 705
 706 config LTO
 707         bool
 708         help
 709           Selected if the kernel will be built using the compiler's LTO feature.
 710
 711 config LTO_CLANG
 712         bool
 713         select LTO
 714         help
 715           Selected if the kernel will be built using Clang's LTO feature.
 716
 717 config ARCH_SUPPORTS_LTO_CLANG
 718         bool
 719         help
 720           An architecture should select this option if it supports:
 721           - compiling with Clang,
 722           - compiling inline assembly with Clang's integrated assembler,
 723           - and linking with LLD.
 724
 725 config ARCH_SUPPORTS_LTO_CLANG_THIN
 726         bool
 727         help
 728           An architecture should select this option if it can support Clang's
 729           ThinLTO mode.
 730
 731 config HAS_LTO_CLANG
 732         def_bool y
 733         depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
 734         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 735         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 736         depends on ARCH_SUPPORTS_LTO_CLANG
 737         depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 738         # https://github.com/ClangBuiltLinux/linux/issues/1721
 739         depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
 740         depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
 741         depends on !GCOV_KERNEL
 742         help
 743           The compiler and Kconfig options support building with Clang's
 744           LTO.
 745
 746 choice
 747         prompt "Link Time Optimization (LTO)"
 748         default LTO_NONE
 749         help
 750           This option enables Link Time Optimization (LTO), which allows the
 751           compiler to optimize binaries globally.
 752
 753           If unsure, select LTO_NONE. Note that LTO is very resource-intensive
 754           so it's disabled by default.
 755
 756 config LTO_NONE
 757         bool "None"
 758         help
 759           Build the kernel normally, without Link Time Optimization (LTO).
 760
 761 config LTO_CLANG_FULL
 762         bool "Clang Full LTO (EXPERIMENTAL)"
 763         depends on HAS_LTO_CLANG
 764         depends on !COMPILE_TEST
 765         select LTO_CLANG
 766         help
 767           This option enables Clang's full Link Time Optimization (LTO), which
 768           allows the compiler to optimize the kernel globally. If you enable
 769           this option, the compiler generates LLVM bitcode instead of ELF
 770           object files, and the actual compilation from bitcode happens at
 771           the LTO link step, which may take several minutes depending on the
 772           kernel configuration. More information can be found from LLVM's
 773           documentation:
 774
 775             https://llvm.org/docs/LinkTimeOptimization.html
 776
 777           During link time, this option can use a large amount of RAM, and
 778           may take much longer than the ThinLTO option.
 779
 780 config LTO_CLANG_THIN
 781         bool "Clang ThinLTO (EXPERIMENTAL)"
 782         depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
 783         select LTO_CLANG
 784         help
 785           This option enables Clang's ThinLTO, which allows for parallel
 786           optimization and faster incremental compiles compared to the
 787           CONFIG_LTO_CLANG_FULL option. More information can be found
 788           from Clang's documentation:
 789
 790             https://clang.llvm.org/docs/ThinLTO.html
 791
 792           If unsure, say Y.
 793 endchoice
 794
 795 config ARCH_SUPPORTS_CFI_CLANG
 796         bool
 797         help
 798           An architecture should select this option if it can support Clang's
 799           Control-Flow Integrity (CFI) checking.
 800
 801 config ARCH_USES_CFI_TRAPS
 802         bool
 803
 804 config CFI_CLANG
 805         bool "Use Clang's Control Flow Integrity (CFI)"
 806         depends on ARCH_SUPPORTS_CFI_CLANG
 807         depends on $(cc-option,-fsanitize=kcfi)
 808         help
 809           This option enables Clang’s forward-edge Control Flow Integrity
 810           (CFI) checking, where the compiler injects a runtime check to each
 811           indirect function call to ensure the target is a valid function with
 812           the correct static type. This restricts possible call targets and
 813           makes it more difficult for an attacker to exploit bugs that allow
 814           the modification of stored function pointers. More information can be
 815           found from Clang's documentation:
 816
 817             https://clang.llvm.org/docs/ControlFlowIntegrity.html
 818
 819 config CFI_PERMISSIVE
 820         bool "Use CFI in permissive mode"
 821         depends on CFI_CLANG
 822         help
 823           When selected, Control Flow Integrity (CFI) violations result in a
 824           warning instead of a kernel panic. This option should only be used
 825           for finding indirect call type mismatches during development.
 826
 827           If unsure, say N.
 828
 829 config HAVE_ARCH_WITHIN_STACK_FRAMES
 830         bool
 831         help
 832           An architecture should select this if it can walk the kernel stack
 833           frames to determine if an object is part of either the arguments
 834           or local variables (i.e. that it excludes saved return addresses,
 835           and similar) by implementing an inline arch_within_stack_frames(),
 836           which is used by CONFIG_HARDENED_USERCOPY.
 837
 838 config HAVE_CONTEXT_TRACKING_USER
 839         bool
 840         help
 841           Provide kernel/user boundaries probes necessary for subsystems
 842           that need it, such as userspace RCU extended quiescent state.
 843           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 844           optimized behind static key or through the slow path using TIF_NOHZ
 845           flag. Exceptions handlers must be wrapped as well. Irqs are already
 846           protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
 847           handling on irq exit still need to be protected.
 848
 849 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 850         bool
 851         help
 852           Architecture neither relies on exception_enter()/exception_exit()
 853           nor on schedule_user(). Also preempt_schedule_notrace() and
 854           preempt_schedule_irq() can't be called in a preemptible section
 855           while context tracking is CONTEXT_USER. This feature reflects a sane
 856           entry implementation where the following requirements are met on
 857           critical entry code, ie: before user_exit() or after user_enter():
 858
 859           - Critical entry code isn't preemptible (or better yet:
 860             not interruptible).
 861           - No use of RCU read side critical sections, unless ct_nmi_enter()
 862             got called.
 863           - No use of instrumentation, unless instrumentation_begin() got
 864             called.
 865
 866 config HAVE_TIF_NOHZ
 867         bool
 868         help
 869           Arch relies on TIF_NOHZ and syscall slow path to implement context
 870           tracking calls to user_enter()/user_exit().
 871
 872 config HAVE_VIRT_CPU_ACCOUNTING
 873         bool
 874
 875 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
 876         bool
 877         help
 878           Architecture has its own way to account idle CPU time and therefore
 879           doesn't implement vtime_account_idle().
 880
 881 config ARCH_HAS_SCALED_CPUTIME
 882         bool
 883
 884 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 885         bool
 886         default y if 64BIT
 887         help
 888           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 889           Before enabling this option, arch code must be audited
 890           to ensure there are no races in concurrent read/write of
 891           cputime_t. For example, reading/writing 64-bit cputime_t on
 892           some 32-bit arches may require multiple accesses, so proper
 893           locking is needed to protect against concurrent accesses.
 894
 895 config HAVE_IRQ_TIME_ACCOUNTING
 896         bool
 897         help
 898           Archs need to ensure they use a high enough resolution clock to
 899           support irq time accounting and then call enable_sched_clock_irqtime().
 900
 901 config HAVE_MOVE_PUD
 902         bool
 903         help
 904           Architectures that select this are able to move page tables at the
 905           PUD level. If there are only 3 page table levels, the move effectively
 906           happens at the PGD level.
 907
 908 config HAVE_MOVE_PMD
 909         bool
 910         help
 911           Archs that select this are able to move page tables at the PMD level.
 912
 913 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 914         bool
 915
 916 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 917         bool
 918
 919 config HAVE_ARCH_HUGE_VMAP
 920         bool
 921
 922 #
 923 #  Archs that select this would be capable of PMD-sized vmaps (i.e.,
 924 #  arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
 925 #  must be used to enable allocations to use hugepages.
 926 #
 927 config HAVE_ARCH_HUGE_VMALLOC
 928         depends on HAVE_ARCH_HUGE_VMAP
 929         bool
 930
 931 config ARCH_WANT_HUGE_PMD_SHARE
 932         bool
 933
 934 # Archs that want to use pmd_mkwrite on kernel memory need it defined even
 935 # if there are no userspace memory management features that use it
 936 config ARCH_WANT_KERNEL_PMD_MKWRITE
 937         bool
 938
 939 config ARCH_WANT_PMD_MKWRITE
 940         def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
 941
 942 config HAVE_ARCH_SOFT_DIRTY
 943         bool
 944
 945 config HAVE_MOD_ARCH_SPECIFIC
 946         bool
 947         help
 948           The arch uses struct mod_arch_specific to store data.  Many arches
 949           just need a simple module loader without arch specific data - those
 950           should not enable this.
 951
 952 config MODULES_USE_ELF_RELA
 953         bool
 954         help
 955           Modules only use ELF RELA relocations.  Modules with ELF REL
 956           relocations will give an error.
 957
 958 config MODULES_USE_ELF_REL
 959         bool
 960         help
 961           Modules only use ELF REL relocations.  Modules with ELF RELA
 962           relocations will give an error.
 963
 964 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
 965         bool
 966         help
 967           For architectures like powerpc/32 which have constraints on module
 968           allocation and need to allocate module data outside of module area.
 969
 970 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 971         bool
 972         help
 973           Architecture doesn't only execute the irq handler on the irq stack
 974           but also irq_exit(). This way we can process softirqs on this irq
 975           stack instead of switching to a new one when we call __do_softirq()
 976           in the end of an hardirq.
 977           This spares a stack switch and improves cache usage on softirq
 978           processing.
 979
 980 config HAVE_SOFTIRQ_ON_OWN_STACK
 981         bool
 982         help
 983           Architecture provides a function to run __do_softirq() on a
 984           separate stack.
 985
 986 config SOFTIRQ_ON_OWN_STACK
 987         def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
 988
 989 config ALTERNATE_USER_ADDRESS_SPACE
 990         bool
 991         help
 992           Architectures set this when the CPU uses separate address
 993           spaces for kernel and user space pointers. In this case, the
 994           access_ok() check on a __user pointer is skipped.
 995
 996 config PGTABLE_LEVELS
 997         int
 998         default 2
 999
1000 config ARCH_HAS_ELF_RANDOMIZE
1001         bool
1002         help
1003           An architecture supports choosing randomized locations for
1004           stack, mmap, brk, and ET_DYN. Defined functions:
1005           - arch_mmap_rnd()
1006           - arch_randomize_brk()
1007
1008 config HAVE_ARCH_MMAP_RND_BITS
1009         bool
1010         help
1011           An arch should select this symbol if it supports setting a variable
1012           number of bits for use in establishing the base address for mmap
1013           allocations, has MMU enabled and provides values for both:
1014           - ARCH_MMAP_RND_BITS_MIN
1015           - ARCH_MMAP_RND_BITS_MAX
1016
1017 config HAVE_EXIT_THREAD
1018         bool
1019         help
1020           An architecture implements exit_thread.
1021
1022 config ARCH_MMAP_RND_BITS_MIN
1023         int
1024
1025 config ARCH_MMAP_RND_BITS_MAX
1026         int
1027
1028 config ARCH_MMAP_RND_BITS_DEFAULT
1029         int
1030
1031 config ARCH_MMAP_RND_BITS
1032         int "Number of bits to use for ASLR of mmap base address" if EXPERT
1033         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1034         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1035         default ARCH_MMAP_RND_BITS_MIN
1036         depends on HAVE_ARCH_MMAP_RND_BITS
1037         help
1038           This value can be used to select the number of bits to use to
1039           determine the random offset to the base address of vma regions
1040           resulting from mmap allocations. This value will be bounded
1041           by the architecture's minimum and maximum supported values.
1042
1043           This value can be changed after boot using the
1044           /proc/sys/vm/mmap_rnd_bits tunable
1045
1046 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1047         bool
1048         help
1049           An arch should select this symbol if it supports running applications
1050           in compatibility mode, supports setting a variable number of bits for
1051           use in establishing the base address for mmap allocations, has MMU
1052           enabled and provides values for both:
1053           - ARCH_MMAP_RND_COMPAT_BITS_MIN
1054           - ARCH_MMAP_RND_COMPAT_BITS_MAX
1055
1056 config ARCH_MMAP_RND_COMPAT_BITS_MIN
1057         int
1058
1059 config ARCH_MMAP_RND_COMPAT_BITS_MAX
1060         int
1061
1062 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1063         int
1064
1065 config ARCH_MMAP_RND_COMPAT_BITS
1066         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1067         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1068         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1069         default ARCH_MMAP_RND_COMPAT_BITS_MIN
1070         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1071         help
1072           This value can be used to select the number of bits to use to
1073           determine the random offset to the base address of vma regions
1074           resulting from mmap allocations for compatible applications This
1075           value will be bounded by the architecture's minimum and maximum
1076           supported values.
1077
1078           This value can be changed after boot using the
1079           /proc/sys/vm/mmap_rnd_compat_bits tunable
1080
1081 config HAVE_ARCH_COMPAT_MMAP_BASES
1082         bool
1083         help
1084           This allows 64bit applications to invoke 32-bit mmap() syscall
1085           and vice-versa 32-bit applications to call 64-bit mmap().
1086           Required for applications doing different bitness syscalls.
1087
1088 config PAGE_SIZE_LESS_THAN_64KB
1089         def_bool y
1090         depends on !ARM64_64K_PAGES
1091         depends on !IA64_PAGE_SIZE_64KB
1092         depends on !PAGE_SIZE_64KB
1093         depends on !PARISC_PAGE_SIZE_64KB
1094         depends on PAGE_SIZE_LESS_THAN_256KB
1095
1096 config PAGE_SIZE_LESS_THAN_256KB
1097         def_bool y
1098         depends on !PAGE_SIZE_256KB
1099
1100 # This allows to use a set of generic functions to determine mmap base
1101 # address by giving priority to top-down scheme only if the process
1102 # is not in legacy mode (compat task, unlimited stack size or
1103 # sysctl_legacy_va_layout).
1104 # Architecture that selects this option can provide its own version of:
1105 # - STACK_RND_MASK
1106 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1107         bool
1108         depends on MMU
1109         select ARCH_HAS_ELF_RANDOMIZE
1110
1111 config HAVE_OBJTOOL
1112         bool
1113
1114 config HAVE_JUMP_LABEL_HACK
1115         bool
1116
1117 config HAVE_NOINSTR_HACK
1118         bool
1119
1120 config HAVE_NOINSTR_VALIDATION
1121         bool
1122
1123 config HAVE_UACCESS_VALIDATION
1124         bool
1125         select OBJTOOL
1126
1127 config HAVE_STACK_VALIDATION
1128         bool
1129         help
1130           Architecture supports objtool compile-time frame pointer rule
1131           validation.
1132
1133 config HAVE_RELIABLE_STACKTRACE
1134         bool
1135         help
1136           Architecture has either save_stack_trace_tsk_reliable() or
1137           arch_stack_walk_reliable() function which only returns a stack trace
1138           if it can guarantee the trace is reliable.
1139
1140 config HAVE_ARCH_HASH
1141         bool
1142         default n
1143         help
1144           If this is set, the architecture provides an <asm/hash.h>
1145           file which provides platform-specific implementations of some
1146           functions in <linux/hash.h> or fs/namei.c.
1147
1148 config HAVE_ARCH_NVRAM_OPS
1149         bool
1150
1151 config ISA_BUS_API
1152         def_bool ISA
1153
1154 #
1155 # ABI hall of shame
1156 #
1157 config CLONE_BACKWARDS
1158         bool
1159         help
1160           Architecture has tls passed as the 4th argument of clone(2),
1161           not the 5th one.
1162
1163 config CLONE_BACKWARDS2
1164         bool
1165         help
1166           Architecture has the first two arguments of clone(2) swapped.
1167
1168 config CLONE_BACKWARDS3
1169         bool
1170         help
1171           Architecture has tls passed as the 3rd argument of clone(2),
1172           not the 5th one.
1173
1174 config ODD_RT_SIGACTION
1175         bool
1176         help
1177           Architecture has unusual rt_sigaction(2) arguments
1178
1179 config OLD_SIGSUSPEND
1180         bool
1181         help
1182           Architecture has old sigsuspend(2) syscall, of one-argument variety
1183
1184 config OLD_SIGSUSPEND3
1185         bool
1186         help
1187           Even weirder antique ABI - three-argument sigsuspend(2)
1188
1189 config OLD_SIGACTION
1190         bool
1191         help
1192           Architecture has old sigaction(2) syscall.  Nope, not the same
1193           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1194           but fairly different variant of sigaction(2), thanks to OSF/1
1195           compatibility...
1196
1197 config COMPAT_OLD_SIGACTION
1198         bool
1199
1200 config COMPAT_32BIT_TIME
1201         bool "Provide system calls for 32-bit time_t"
1202         default !64BIT || COMPAT
1203         help
1204           This enables 32 bit time_t support in addition to 64 bit time_t support.
1205           This is relevant on all 32-bit architectures, and 64-bit architectures
1206           as part of compat syscall handling.
1207
1208 config ARCH_NO_PREEMPT
1209         bool
1210
1211 config ARCH_SUPPORTS_RT
1212         bool
1213
1214 config CPU_NO_EFFICIENT_FFS
1215         def_bool n
1216
1217 config HAVE_ARCH_VMAP_STACK
1218         def_bool n
1219         help
1220           An arch should select this symbol if it can support kernel stacks
1221           in vmalloc space.  This means:
1222
1223           - vmalloc space must be large enough to hold many kernel stacks.
1224             This may rule out many 32-bit architectures.
1225
1226           - Stacks in vmalloc space need to work reliably.  For example, if
1227             vmap page tables are created on demand, either this mechanism
1228             needs to work while the stack points to a virtual address with
1229             unpopulated page tables or arch code (switch_to() and switch_mm(),
1230             most likely) needs to ensure that the stack's page table entries
1231             are populated before running on a possibly unpopulated stack.
1232
1233           - If the stack overflows into a guard page, something reasonable
1234             should happen.  The definition of "reasonable" is flexible, but
1235             instantly rebooting without logging anything would be unfriendly.
1236
1237 config VMAP_STACK
1238         default y
1239         bool "Use a virtually-mapped stack"
1240         depends on HAVE_ARCH_VMAP_STACK
1241         depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1242         help
1243           Enable this if you want the use virtually-mapped kernel stacks
1244           with guard pages.  This causes kernel stack overflows to be
1245           caught immediately rather than causing difficult-to-diagnose
1246           corruption.
1247
1248           To use this with software KASAN modes, the architecture must support
1249           backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1250           must be enabled.
1251
1252 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1253         def_bool n
1254         help
1255           An arch should select this symbol if it can support kernel stack
1256           offset randomization with calls to add_random_kstack_offset()
1257           during syscall entry and choose_random_kstack_offset() during
1258           syscall exit. Careful removal of -fstack-protector-strong and
1259           -fstack-protector should also be applied to the entry code and
1260           closely examined, as the artificial stack bump looks like an array
1261           to the compiler, so it will attempt to add canary checks regardless
1262           of the static branch state.
1263
1264 config RANDOMIZE_KSTACK_OFFSET
1265         bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1266         default y
1267         depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1268         depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1269         help
1270           The kernel stack offset can be randomized (after pt_regs) by
1271           roughly 5 bits of entropy, frustrating memory corruption
1272           attacks that depend on stack address determinism or
1273           cross-syscall address exposures.
1274
1275           The feature is controlled via the "randomize_kstack_offset=on/off"
1276           kernel boot param, and if turned off has zero overhead due to its use
1277           of static branches (see JUMP_LABEL).
1278
1279           If unsure, say Y.
1280
1281 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1282         bool "Default state of kernel stack offset randomization"
1283         depends on RANDOMIZE_KSTACK_OFFSET
1284         help
1285           Kernel stack offset randomization is controlled by kernel boot param
1286           "randomize_kstack_offset=on/off", and this config chooses the default
1287           boot state.
1288
1289 config ARCH_OPTIONAL_KERNEL_RWX
1290         def_bool n
1291
1292 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1293         def_bool n
1294
1295 config ARCH_HAS_STRICT_KERNEL_RWX
1296         def_bool n
1297
1298 config STRICT_KERNEL_RWX
1299         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1300         depends on ARCH_HAS_STRICT_KERNEL_RWX
1301         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1302         help
1303           If this is set, kernel text and rodata memory will be made read-only,
1304           and non-text memory will be made non-executable. This provides
1305           protection against certain security exploits (e.g. executing the heap
1306           or modifying text)
1307
1308           These features are considered standard security practice these days.
1309           You should say Y here in almost all cases.
1310
1311 config ARCH_HAS_STRICT_MODULE_RWX
1312         def_bool n
1313
1314 config STRICT_MODULE_RWX
1315         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1316         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1317         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1318         help
1319           If this is set, module text and rodata memory will be made read-only,
1320           and non-text memory will be made non-executable. This provides
1321           protection against certain security exploits (e.g. writing to text)
1322
1323 # select if the architecture provides an asm/dma-direct.h header
1324 config ARCH_HAS_PHYS_TO_DMA
1325         bool
1326
1327 config HAVE_ARCH_COMPILER_H
1328         bool
1329         help
1330           An architecture can select this if it provides an
1331           asm/compiler.h header that should be included after
1332           linux/compiler-*.h in order to override macro definitions that those
1333           headers generally provide.
1334
1335 config HAVE_ARCH_PREL32_RELOCATIONS
1336         bool
1337         help
1338           May be selected by an architecture if it supports place-relative
1339           32-bit relocations, both in the toolchain and in the module loader,
1340           in which case relative references can be used in special sections
1341           for PCI fixup, initcalls etc which are only half the size on 64 bit
1342           architectures, and don't require runtime relocation on relocatable
1343           kernels.
1344
1345 config ARCH_USE_MEMREMAP_PROT
1346         bool
1347
1348 config LOCK_EVENT_COUNTS
1349         bool "Locking event counts collection"
1350         depends on DEBUG_FS
1351         help
1352           Enable light-weight counting of various locking related events
1353           in the system with minimal performance impact. This reduces
1354           the chance of application behavior change because of timing
1355           differences. The counts are reported via debugfs.
1356
1357 # Select if the architecture has support for applying RELR relocations.
1358 config ARCH_HAS_RELR
1359         bool
1360
1361 config RELR
1362         bool "Use RELR relocation packing"
1363         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1364         default y
1365         help
1366           Store the kernel's dynamic relocations in the RELR relocation packing
1367           format. Requires a compatible linker (LLD supports this feature), as
1368           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1369           are compatible).
1370
1371 config ARCH_HAS_MEM_ENCRYPT
1372         bool
1373
1374 config ARCH_HAS_CC_PLATFORM
1375         bool
1376
1377 config HAVE_SPARSE_SYSCALL_NR
1378         bool
1379         help
1380           An architecture should select this if its syscall numbering is sparse
1381           to save space. For example, MIPS architecture has a syscall array with
1382           entries at 4000, 5000 and 6000 locations. This option turns on syscall
1383           related optimizations for a given architecture.
1384
1385 config ARCH_HAS_VDSO_DATA
1386         bool
1387
1388 config HAVE_STATIC_CALL
1389         bool
1390
1391 config HAVE_STATIC_CALL_INLINE
1392         bool
1393         depends on HAVE_STATIC_CALL
1394         select OBJTOOL
1395
1396 config HAVE_PREEMPT_DYNAMIC
1397         bool
1398
1399 config HAVE_PREEMPT_DYNAMIC_CALL
1400         bool
1401         depends on HAVE_STATIC_CALL
1402         select HAVE_PREEMPT_DYNAMIC
1403         help
1404           An architecture should select this if it can handle the preemption
1405           model being selected at boot time using static calls.
1406
1407           Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1408           preemption function will be patched directly.
1409
1410           Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1411           call to a preemption function will go through a trampoline, and the
1412           trampoline will be patched.
1413
1414           It is strongly advised to support inline static call to avoid any
1415           overhead.
1416
1417 config HAVE_PREEMPT_DYNAMIC_KEY
1418         bool
1419         depends on HAVE_ARCH_JUMP_LABEL
1420         select HAVE_PREEMPT_DYNAMIC
1421         help
1422           An architecture should select this if it can handle the preemption
1423           model being selected at boot time using static keys.
1424
1425           Each preemption function will be given an early return based on a
1426           static key. This should have slightly lower overhead than non-inline
1427           static calls, as this effectively inlines each trampoline into the
1428           start of its callee. This may avoid redundant work, and may
1429           integrate better with CFI schemes.
1430
1431           This will have greater overhead than using inline static calls as
1432           the call to the preemption function cannot be entirely elided.
1433
1434 config ARCH_WANT_LD_ORPHAN_WARN
1435         bool
1436         help
1437           An arch should select this symbol once all linker sections are explicitly
1438           included, size-asserted, or discarded in the linker scripts. This is
1439           important because we never want expected sections to be placed heuristically
1440           by the linker, since the locations of such sections can change between linker
1441           versions.
1442
1443 config HAVE_ARCH_PFN_VALID
1444         bool
1445
1446 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1447         bool
1448
1449 config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1450         bool
1451
1452 config ARCH_SPLIT_ARG64
1453         bool
1454         help
1455           If a 32-bit architecture requires 64-bit arguments to be split into
1456           pairs of 32-bit arguments, select this option.
1457
1458 config ARCH_HAS_ELFCORE_COMPAT
1459         bool
1460
1461 config ARCH_HAS_PARANOID_L1D_FLUSH
1462         bool
1463
1464 config ARCH_HAVE_TRACE_MMIO_ACCESS
1465         bool
1466
1467 config DYNAMIC_SIGFRAME
1468         bool
1469
1470 # Select, if arch has a named attribute group bound to NUMA device nodes.
1471 config HAVE_ARCH_NODE_DEV_GROUP
1472         bool
1473
1474 config ARCH_HAS_NONLEAF_PMD_YOUNG
1475         bool
1476         help
1477           Architectures that select this option are capable of setting the
1478           accessed bit in non-leaf PMD entries when using them as part of linear
1479           address translations. Page table walkers that clear the accessed bit
1480           may use this capability to reduce their search space.
1481
1482 source "kernel/gcov/Kconfig"
1483
1484 source "scripts/gcc-plugins/Kconfig"
1485
1486 config FUNCTION_ALIGNMENT_4B
1487         bool
1488
1489 config FUNCTION_ALIGNMENT_8B
1490         bool
1491
1492 config FUNCTION_ALIGNMENT_16B
1493         bool
1494
1495 config FUNCTION_ALIGNMENT_32B
1496         bool
1497
1498 config FUNCTION_ALIGNMENT_64B
1499         bool
1500
1501 config FUNCTION_ALIGNMENT
1502         int
1503         default 64 if FUNCTION_ALIGNMENT_64B
1504         default 32 if FUNCTION_ALIGNMENT_32B
1505         default 16 if FUNCTION_ALIGNMENT_16B
1506         default 8 if FUNCTION_ALIGNMENT_8B
1507         default 4 if FUNCTION_ALIGNMENT_4B
1508         default 0
1509
1510 endmenu