arch/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 #
   3 # General architecture dependent options
   4 #
   5
   6 #
   7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
   8 # override the default values in this file.
   9 #
  10 source "arch/$(SRCARCH)/Kconfig"
  11
  12 menu "General architecture-dependent options"
  13
  14 config CRASH_CORE
  15         bool
  16
  17 config KEXEC_CORE
  18         select CRASH_CORE
  19         bool
  20
  21 config HAVE_IMA_KEXEC
  22         bool
  23
  24 config HOTPLUG_SMT
  25         bool
  26
  27 config OPROFILE
  28         tristate "OProfile system profiling"
  29         depends on PROFILING
  30         depends on HAVE_OPROFILE
  31         select RING_BUFFER
  32         select RING_BUFFER_ALLOW_SWAP
  33         help
  34           OProfile is a profiling system capable of profiling the
  35           whole system, include the kernel, kernel modules, libraries,
  36           and applications.
  37
  38           If unsure, say N.
  39
  40 config OPROFILE_EVENT_MULTIPLEX
  41         bool "OProfile multiplexing support (EXPERIMENTAL)"
  42         default n
  43         depends on OPROFILE && X86
  44         help
  45           The number of hardware counters is limited. The multiplexing
  46           feature enables OProfile to gather more events than counters
  47           are provided by the hardware. This is realized by switching
  48           between events at a user specified time interval.
  49
  50           If unsure, say N.
  51
  52 config HAVE_OPROFILE
  53         bool
  54
  55 config OPROFILE_NMI_TIMER
  56         def_bool y
  57         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  58
  59 config KPROBES
  60         bool "Kprobes"
  61         depends on MODULES
  62         depends on HAVE_KPROBES
  63         select KALLSYMS
  64         help
  65           Kprobes allows you to trap at almost any kernel address and
  66           execute a callback function.  register_kprobe() establishes
  67           a probepoint and specifies the callback.  Kprobes is useful
  68           for kernel debugging, non-intrusive instrumentation and testing.
  69           If in doubt, say "N".
  70
  71 config JUMP_LABEL
  72        bool "Optimize very unlikely/likely branches"
  73        depends on HAVE_ARCH_JUMP_LABEL
  74        help
  75          This option enables a transparent branch optimization that
  76          makes certain almost-always-true or almost-always-false branch
  77          conditions even cheaper to execute within the kernel.
  78
  79          Certain performance-sensitive kernel code, such as trace points,
  80          scheduler functionality, networking code and KVM have such
  81          branches and include support for this optimization technique.
  82
  83          If it is detected that the compiler has support for "asm goto",
  84          the kernel will compile such branches with just a nop
  85          instruction. When the condition flag is toggled to true, the
  86          nop will be converted to a jump instruction to execute the
  87          conditional block of instructions.
  88
  89          This technique lowers overhead and stress on the branch prediction
  90          of the processor and generally makes the kernel faster. The update
  91          of the condition is slower, but those are always very rare.
  92
  93          ( On 32-bit x86, the necessary options added to the compiler
  94            flags may increase the size of the kernel slightly. )
  95
  96 config STATIC_KEYS_SELFTEST
  97         bool "Static key selftest"
  98         depends on JUMP_LABEL
  99         help
 100           Boot time self-test of the branch patching code.
 101
 102 config OPTPROBES
 103         def_bool y
 104         depends on KPROBES && HAVE_OPTPROBES
 105         select TASKS_RCU if PREEMPT
 106
 107 config KPROBES_ON_FTRACE
 108         def_bool y
 109         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 110         depends on DYNAMIC_FTRACE_WITH_REGS
 111         help
 112          If function tracer is enabled and the arch supports full
 113          passing of pt_regs to function tracing, then kprobes can
 114          optimize on top of function tracing.
 115
 116 config UPROBES
 117         def_bool n
 118         depends on ARCH_SUPPORTS_UPROBES
 119         help
 120           Uprobes is the user-space counterpart to kprobes: they
 121           enable instrumentation applications (such as 'perf probe')
 122           to establish unintrusive probes in user-space binaries and
 123           libraries, by executing handler functions when the probes
 124           are hit by user-space applications.
 125
 126           ( These probes come in the form of single-byte breakpoints,
 127             managed by the kernel and kept transparent to the probed
 128             application. )
 129
 130 config HAVE_64BIT_ALIGNED_ACCESS
 131         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 132         help
 133           Some architectures require 64 bit accesses to be 64 bit
 134           aligned, which also requires structs containing 64 bit values
 135           to be 64 bit aligned too. This includes some 32 bit
 136           architectures which can do 64 bit accesses, as well as 64 bit
 137           architectures without unaligned access.
 138
 139           This symbol should be selected by an architecture if 64 bit
 140           accesses are required to be 64 bit aligned in this way even
 141           though it is not a 64 bit architecture.
 142
 143           See Documentation/unaligned-memory-access.txt for more
 144           information on the topic of unaligned memory accesses.
 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/unaligned-memory-access.txt 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 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 248 config ARCH_HAS_SET_MEMORY
 249         bool
 250
 251 # Select if arch init_task must go in the __init_task_data section
 252 config ARCH_TASK_STRUCT_ON_STACK
 253        bool
 254
 255 # Select if arch has its private alloc_task_struct() function
 256 config ARCH_TASK_STRUCT_ALLOCATOR
 257         bool
 258
 259 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 260         bool
 261         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 262         help
 263           An architecture should select this to provide hardened usercopy
 264           knowledge about what region of the thread_struct should be
 265           whitelisted for copying to userspace. Normally this is only the
 266           FPU registers. Specifically, arch_thread_struct_whitelist()
 267           should be implemented. Without this, the entire thread_struct
 268           field in task_struct will be left whitelisted.
 269
 270 # Select if arch has its private alloc_thread_stack() function
 271 config ARCH_THREAD_STACK_ALLOCATOR
 272         bool
 273
 274 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 275 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 276         bool
 277
 278 config HAVE_REGS_AND_STACK_ACCESS_API
 279         bool
 280         help
 281           This symbol should be selected by an architecure if it supports
 282           the API needed to access registers and stack entries from pt_regs,
 283           declared in asm/ptrace.h
 284           For example the kprobes-based event tracer needs this API.
 285
 286 config HAVE_RSEQ
 287         bool
 288         depends on HAVE_REGS_AND_STACK_ACCESS_API
 289         help
 290           This symbol should be selected by an architecture if it
 291           supports an implementation of restartable sequences.
 292
 293 config HAVE_CLK
 294         bool
 295         help
 296           The <linux/clk.h> calls support software clock gating and
 297           thus are a key power management tool on many systems.
 298
 299 config HAVE_HW_BREAKPOINT
 300         bool
 301         depends on PERF_EVENTS
 302
 303 config HAVE_MIXED_BREAKPOINTS_REGS
 304         bool
 305         depends on HAVE_HW_BREAKPOINT
 306         help
 307           Depending on the arch implementation of hardware breakpoints,
 308           some of them have separate registers for data and instruction
 309           breakpoints addresses, others have mixed registers to store
 310           them but define the access type in a control register.
 311           Select this option if your arch implements breakpoints under the
 312           latter fashion.
 313
 314 config HAVE_USER_RETURN_NOTIFIER
 315         bool
 316
 317 config HAVE_PERF_EVENTS_NMI
 318         bool
 319         help
 320           System hardware can generate an NMI using the perf event
 321           subsystem.  Also has support for calculating CPU cycle events
 322           to determine how many clock cycles in a given period.
 323
 324 config HAVE_HARDLOCKUP_DETECTOR_PERF
 325         bool
 326         depends on HAVE_PERF_EVENTS_NMI
 327         help
 328           The arch chooses to use the generic perf-NMI-based hardlockup
 329           detector. Must define HAVE_PERF_EVENTS_NMI.
 330
 331 config HAVE_NMI_WATCHDOG
 332         depends on HAVE_NMI
 333         bool
 334         help
 335           The arch provides a low level NMI watchdog. It provides
 336           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 337
 338 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 339         bool
 340         select HAVE_NMI_WATCHDOG
 341         help
 342           The arch chooses to provide its own hardlockup detector, which is
 343           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 344           interfaces and parameters provided by hardlockup detector subsystem.
 345
 346 config HAVE_PERF_REGS
 347         bool
 348         help
 349           Support selective register dumps for perf events. This includes
 350           bit-mapping of each registers and a unique architecture id.
 351
 352 config HAVE_PERF_USER_STACK_DUMP
 353         bool
 354         help
 355           Support user stack dumps for perf event samples. This needs
 356           access to the user stack pointer which is not unified across
 357           architectures.
 358
 359 config HAVE_ARCH_JUMP_LABEL
 360         bool
 361
 362 config HAVE_RCU_TABLE_FREE
 363         bool
 364
 365 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 366         bool
 367
 368 config HAVE_ALIGNED_STRUCT_PAGE
 369         bool
 370         help
 371           This makes sure that struct pages are double word aligned and that
 372           e.g. the SLUB allocator can perform double word atomic operations
 373           on a struct page for better performance. However selecting this
 374           might increase the size of a struct page by a word.
 375
 376 config HAVE_CMPXCHG_LOCAL
 377         bool
 378
 379 config HAVE_CMPXCHG_DOUBLE
 380         bool
 381
 382 config ARCH_WEAK_RELEASE_ACQUIRE
 383         bool
 384
 385 config ARCH_WANT_IPC_PARSE_VERSION
 386         bool
 387
 388 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 389         bool
 390
 391 config ARCH_WANT_OLD_COMPAT_IPC
 392         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 393         bool
 394
 395 config HAVE_ARCH_SECCOMP_FILTER
 396         bool
 397         help
 398           An arch should select this symbol if it provides all of these things:
 399           - syscall_get_arch()
 400           - syscall_get_arguments()
 401           - syscall_rollback()
 402           - syscall_set_return_value()
 403           - SIGSYS siginfo_t support
 404           - secure_computing is called from a ptrace_event()-safe context
 405           - secure_computing return value is checked and a return value of -1
 406             results in the system call being skipped immediately.
 407           - seccomp syscall wired up
 408
 409 config SECCOMP_FILTER
 410         def_bool y
 411         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 412         help
 413           Enable tasks to build secure computing environments defined
 414           in terms of Berkeley Packet Filter programs which implement
 415           task-defined system call filtering polices.
 416
 417           See Documentation/userspace-api/seccomp_filter.rst for details.
 418
 419 config HAVE_STACKPROTECTOR
 420         bool
 421         help
 422           An arch should select this symbol if:
 423           - it has implemented a stack canary (e.g. __stack_chk_guard)
 424
 425 config CC_HAS_STACKPROTECTOR_NONE
 426         def_bool $(cc-option,-fno-stack-protector)
 427
 428 config STACKPROTECTOR
 429         bool "Stack Protector buffer overflow detection"
 430         depends on HAVE_STACKPROTECTOR
 431         depends on $(cc-option,-fstack-protector)
 432         default y
 433         help
 434           This option turns on the "stack-protector" GCC feature. This
 435           feature puts, at the beginning of functions, a canary value on
 436           the stack just before the return address, and validates
 437           the value just before actually returning.  Stack based buffer
 438           overflows (that need to overwrite this return address) now also
 439           overwrite the canary, which gets detected and the attack is then
 440           neutralized via a kernel panic.
 441
 442           Functions will have the stack-protector canary logic added if they
 443           have an 8-byte or larger character array on the stack.
 444
 445           This feature requires gcc version 4.2 or above, or a distribution
 446           gcc with the feature backported ("-fstack-protector").
 447
 448           On an x86 "defconfig" build, this feature adds canary checks to
 449           about 3% of all kernel functions, which increases kernel code size
 450           by about 0.3%.
 451
 452 config STACKPROTECTOR_STRONG
 453         bool "Strong Stack Protector"
 454         depends on STACKPROTECTOR
 455         depends on $(cc-option,-fstack-protector-strong)
 456         default y
 457         help
 458           Functions will have the stack-protector canary logic added in any
 459           of the following conditions:
 460
 461           - local variable's address used as part of the right hand side of an
 462             assignment or function argument
 463           - local variable is an array (or union containing an array),
 464             regardless of array type or length
 465           - uses register local variables
 466
 467           This feature requires gcc version 4.9 or above, or a distribution
 468           gcc with the feature backported ("-fstack-protector-strong").
 469
 470           On an x86 "defconfig" build, this feature adds canary checks to
 471           about 20% of all kernel functions, which increases the kernel code
 472           size by about 2%.
 473
 474 config HAVE_ARCH_WITHIN_STACK_FRAMES
 475         bool
 476         help
 477           An architecture should select this if it can walk the kernel stack
 478           frames to determine if an object is part of either the arguments
 479           or local variables (i.e. that it excludes saved return addresses,
 480           and similar) by implementing an inline arch_within_stack_frames(),
 481           which is used by CONFIG_HARDENED_USERCOPY.
 482
 483 config HAVE_CONTEXT_TRACKING
 484         bool
 485         help
 486           Provide kernel/user boundaries probes necessary for subsystems
 487           that need it, such as userspace RCU extended quiescent state.
 488           Syscalls need to be wrapped inside user_exit()-user_enter() through
 489           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 490           wrapped as well. Irqs are already protected inside
 491           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 492           irq exit still need to be protected.
 493
 494 config HAVE_VIRT_CPU_ACCOUNTING
 495         bool
 496
 497 config ARCH_HAS_SCALED_CPUTIME
 498         bool
 499
 500 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 501         bool
 502         default y if 64BIT
 503         help
 504           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 505           Before enabling this option, arch code must be audited
 506           to ensure there are no races in concurrent read/write of
 507           cputime_t. For example, reading/writing 64-bit cputime_t on
 508           some 32-bit arches may require multiple accesses, so proper
 509           locking is needed to protect against concurrent accesses.
 510
 511
 512 config HAVE_IRQ_TIME_ACCOUNTING
 513         bool
 514         help
 515           Archs need to ensure they use a high enough resolution clock to
 516           support irq time accounting and then call enable_sched_clock_irqtime().
 517
 518 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 519         bool
 520
 521 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 522         bool
 523
 524 config HAVE_ARCH_HUGE_VMAP
 525         bool
 526
 527 config HAVE_ARCH_SOFT_DIRTY
 528         bool
 529
 530 config HAVE_MOD_ARCH_SPECIFIC
 531         bool
 532         help
 533           The arch uses struct mod_arch_specific to store data.  Many arches
 534           just need a simple module loader without arch specific data - those
 535           should not enable this.
 536
 537 config MODULES_USE_ELF_RELA
 538         bool
 539         help
 540           Modules only use ELF RELA relocations.  Modules with ELF REL
 541           relocations will give an error.
 542
 543 config MODULES_USE_ELF_REL
 544         bool
 545         help
 546           Modules only use ELF REL relocations.  Modules with ELF RELA
 547           relocations will give an error.
 548
 549 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 550         bool
 551         help
 552           Architecture doesn't only execute the irq handler on the irq stack
 553           but also irq_exit(). This way we can process softirqs on this irq
 554           stack instead of switching to a new one when we call __do_softirq()
 555           in the end of an hardirq.
 556           This spares a stack switch and improves cache usage on softirq
 557           processing.
 558
 559 config PGTABLE_LEVELS
 560         int
 561         default 2
 562
 563 config ARCH_HAS_ELF_RANDOMIZE
 564         bool
 565         help
 566           An architecture supports choosing randomized locations for
 567           stack, mmap, brk, and ET_DYN. Defined functions:
 568           - arch_mmap_rnd()
 569           - arch_randomize_brk()
 570
 571 config HAVE_ARCH_MMAP_RND_BITS
 572         bool
 573         help
 574           An arch should select this symbol if it supports setting a variable
 575           number of bits for use in establishing the base address for mmap
 576           allocations, has MMU enabled and provides values for both:
 577           - ARCH_MMAP_RND_BITS_MIN
 578           - ARCH_MMAP_RND_BITS_MAX
 579
 580 config HAVE_EXIT_THREAD
 581         bool
 582         help
 583           An architecture implements exit_thread.
 584
 585 config ARCH_MMAP_RND_BITS_MIN
 586         int
 587
 588 config ARCH_MMAP_RND_BITS_MAX
 589         int
 590
 591 config ARCH_MMAP_RND_BITS_DEFAULT
 592         int
 593
 594 config ARCH_MMAP_RND_BITS
 595         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 596         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 597         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 598         default ARCH_MMAP_RND_BITS_MIN
 599         depends on HAVE_ARCH_MMAP_RND_BITS
 600         help
 601           This value can be used to select the number of bits to use to
 602           determine the random offset to the base address of vma regions
 603           resulting from mmap allocations. This value will be bounded
 604           by the architecture's minimum and maximum supported values.
 605
 606           This value can be changed after boot using the
 607           /proc/sys/vm/mmap_rnd_bits tunable
 608
 609 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 610         bool
 611         help
 612           An arch should select this symbol if it supports running applications
 613           in compatibility mode, supports setting a variable number of bits for
 614           use in establishing the base address for mmap allocations, has MMU
 615           enabled and provides values for both:
 616           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 617           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 618
 619 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 620         int
 621
 622 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 623         int
 624
 625 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 626         int
 627
 628 config ARCH_MMAP_RND_COMPAT_BITS
 629         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 630         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 631         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 632         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 633         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 634         help
 635           This value can be used to select the number of bits to use to
 636           determine the random offset to the base address of vma regions
 637           resulting from mmap allocations for compatible applications This
 638           value will be bounded by the architecture's minimum and maximum
 639           supported values.
 640
 641           This value can be changed after boot using the
 642           /proc/sys/vm/mmap_rnd_compat_bits tunable
 643
 644 config HAVE_ARCH_COMPAT_MMAP_BASES
 645         bool
 646         help
 647           This allows 64bit applications to invoke 32-bit mmap() syscall
 648           and vice-versa 32-bit applications to call 64-bit mmap().
 649           Required for applications doing different bitness syscalls.
 650
 651 config HAVE_COPY_THREAD_TLS
 652         bool
 653         help
 654           Architecture provides copy_thread_tls to accept tls argument via
 655           normal C parameter passing, rather than extracting the syscall
 656           argument from pt_regs.
 657
 658 config HAVE_STACK_VALIDATION
 659         bool
 660         help
 661           Architecture supports the 'objtool check' host tool command, which
 662           performs compile-time stack metadata validation.
 663
 664 config HAVE_RELIABLE_STACKTRACE
 665         bool
 666         help
 667           Architecture has a save_stack_trace_tsk_reliable() function which
 668           only returns a stack trace if it can guarantee the trace is reliable.
 669
 670 config HAVE_ARCH_HASH
 671         bool
 672         default n
 673         help
 674           If this is set, the architecture provides an <asm/hash.h>
 675           file which provides platform-specific implementations of some
 676           functions in <linux/hash.h> or fs/namei.c.
 677
 678 config ISA_BUS_API
 679         def_bool ISA
 680
 681 #
 682 # ABI hall of shame
 683 #
 684 config CLONE_BACKWARDS
 685         bool
 686         help
 687           Architecture has tls passed as the 4th argument of clone(2),
 688           not the 5th one.
 689
 690 config CLONE_BACKWARDS2
 691         bool
 692         help
 693           Architecture has the first two arguments of clone(2) swapped.
 694
 695 config CLONE_BACKWARDS3
 696         bool
 697         help
 698           Architecture has tls passed as the 3rd argument of clone(2),
 699           not the 5th one.
 700
 701 config ODD_RT_SIGACTION
 702         bool
 703         help
 704           Architecture has unusual rt_sigaction(2) arguments
 705
 706 config OLD_SIGSUSPEND
 707         bool
 708         help
 709           Architecture has old sigsuspend(2) syscall, of one-argument variety
 710
 711 config OLD_SIGSUSPEND3
 712         bool
 713         help
 714           Even weirder antique ABI - three-argument sigsuspend(2)
 715
 716 config OLD_SIGACTION
 717         bool
 718         help
 719           Architecture has old sigaction(2) syscall.  Nope, not the same
 720           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 721           but fairly different variant of sigaction(2), thanks to OSF/1
 722           compatibility...
 723
 724 config COMPAT_OLD_SIGACTION
 725         bool
 726
 727 config 64BIT_TIME
 728         def_bool ARCH_HAS_64BIT_TIME
 729         help
 730           This should be selected by all architectures that need to support
 731           new system calls with a 64-bit time_t. This is relevant on all 32-bit
 732           architectures, and 64-bit architectures as part of compat syscall
 733           handling.
 734
 735 config COMPAT_32BIT_TIME
 736         def_bool (!64BIT && 64BIT_TIME) || COMPAT
 737         help
 738           This enables 32 bit time_t support in addition to 64 bit time_t support.
 739           This is relevant on all 32-bit architectures, and 64-bit architectures
 740           as part of compat syscall handling.
 741
 742 config ARCH_NO_COHERENT_DMA_MMAP
 743         bool
 744
 745 config ARCH_NO_PREEMPT
 746         bool
 747
 748 config CPU_NO_EFFICIENT_FFS
 749         def_bool n
 750
 751 config HAVE_ARCH_VMAP_STACK
 752         def_bool n
 753         help
 754           An arch should select this symbol if it can support kernel stacks
 755           in vmalloc space.  This means:
 756
 757           - vmalloc space must be large enough to hold many kernel stacks.
 758             This may rule out many 32-bit architectures.
 759
 760           - Stacks in vmalloc space need to work reliably.  For example, if
 761             vmap page tables are created on demand, either this mechanism
 762             needs to work while the stack points to a virtual address with
 763             unpopulated page tables or arch code (switch_to() and switch_mm(),
 764             most likely) needs to ensure that the stack's page table entries
 765             are populated before running on a possibly unpopulated stack.
 766
 767           - If the stack overflows into a guard page, something reasonable
 768             should happen.  The definition of "reasonable" is flexible, but
 769             instantly rebooting without logging anything would be unfriendly.
 770
 771 config VMAP_STACK
 772         default y
 773         bool "Use a virtually-mapped stack"
 774         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 775         ---help---
 776           Enable this if you want the use virtually-mapped kernel stacks
 777           with guard pages.  This causes kernel stack overflows to be
 778           caught immediately rather than causing difficult-to-diagnose
 779           corruption.
 780
 781           This is presently incompatible with KASAN because KASAN expects
 782           the stack to map directly to the KASAN shadow map using a formula
 783           that is incorrect if the stack is in vmalloc space.
 784
 785 config ARCH_OPTIONAL_KERNEL_RWX
 786         def_bool n
 787
 788 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 789         def_bool n
 790
 791 config ARCH_HAS_STRICT_KERNEL_RWX
 792         def_bool n
 793
 794 config STRICT_KERNEL_RWX
 795         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 796         depends on ARCH_HAS_STRICT_KERNEL_RWX
 797         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 798         help
 799           If this is set, kernel text and rodata memory will be made read-only,
 800           and non-text memory will be made non-executable. This provides
 801           protection against certain security exploits (e.g. executing the heap
 802           or modifying text)
 803
 804           These features are considered standard security practice these days.
 805           You should say Y here in almost all cases.
 806
 807 config ARCH_HAS_STRICT_MODULE_RWX
 808         def_bool n
 809
 810 config STRICT_MODULE_RWX
 811         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 812         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 813         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 814         help
 815           If this is set, module text and rodata memory will be made read-only,
 816           and non-text memory will be made non-executable. This provides
 817           protection against certain security exploits (e.g. writing to text)
 818
 819 # select if the architecture provides an asm/dma-direct.h header
 820 config ARCH_HAS_PHYS_TO_DMA
 821         bool
 822
 823 config ARCH_HAS_REFCOUNT
 824         bool
 825         help
 826           An architecture selects this when it has implemented refcount_t
 827           using open coded assembly primitives that provide an optimized
 828           refcount_t implementation, possibly at the expense of some full
 829           refcount state checks of CONFIG_REFCOUNT_FULL=y.
 830
 831           The refcount overflow check behavior, however, must be retained.
 832           Catching overflows is the primary security concern for protecting
 833           against bugs in reference counts.
 834
 835 config REFCOUNT_FULL
 836         bool "Perform full reference count validation at the expense of speed"
 837         help
 838           Enabling this switches the refcounting infrastructure from a fast
 839           unchecked atomic_t implementation to a fully state checked
 840           implementation, which can be (slightly) slower but provides protections
 841           against various use-after-free conditions that can be used in
 842           security flaw exploits.
 843
 844 source "kernel/gcov/Kconfig"
 845
 846 source "scripts/gcc-plugins/Kconfig"
 847
 848 endmenu