arch/Kconfig

   1 #
   2 # General architecture dependent options
   3 #
   4
   5 config CRASH_CORE
   6         bool
   7
   8 config KEXEC_CORE
   9         select CRASH_CORE
  10         bool
  11
  12 config HAVE_IMA_KEXEC
  13         bool
  14
  15 config OPROFILE
  16         tristate "OProfile system profiling"
  17         depends on PROFILING
  18         depends on HAVE_OPROFILE
  19         select RING_BUFFER
  20         select RING_BUFFER_ALLOW_SWAP
  21         help
  22           OProfile is a profiling system capable of profiling the
  23           whole system, include the kernel, kernel modules, libraries,
  24           and applications.
  25
  26           If unsure, say N.
  27
  28 config OPROFILE_EVENT_MULTIPLEX
  29         bool "OProfile multiplexing support (EXPERIMENTAL)"
  30         default n
  31         depends on OPROFILE && X86
  32         help
  33           The number of hardware counters is limited. The multiplexing
  34           feature enables OProfile to gather more events than counters
  35           are provided by the hardware. This is realized by switching
  36           between events at a user specified time interval.
  37
  38           If unsure, say N.
  39
  40 config HAVE_OPROFILE
  41         bool
  42
  43 config OPROFILE_NMI_TIMER
  44         def_bool y
  45         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  46
  47 config KPROBES
  48         bool "Kprobes"
  49         depends on MODULES
  50         depends on HAVE_KPROBES
  51         select KALLSYMS
  52         help
  53           Kprobes allows you to trap at almost any kernel address and
  54           execute a callback function.  register_kprobe() establishes
  55           a probepoint and specifies the callback.  Kprobes is useful
  56           for kernel debugging, non-intrusive instrumentation and testing.
  57           If in doubt, say "N".
  58
  59 config JUMP_LABEL
  60        bool "Optimize very unlikely/likely branches"
  61        depends on HAVE_ARCH_JUMP_LABEL
  62        help
  63          This option enables a transparent branch optimization that
  64          makes certain almost-always-true or almost-always-false branch
  65          conditions even cheaper to execute within the kernel.
  66
  67          Certain performance-sensitive kernel code, such as trace points,
  68          scheduler functionality, networking code and KVM have such
  69          branches and include support for this optimization technique.
  70
  71          If it is detected that the compiler has support for "asm goto",
  72          the kernel will compile such branches with just a nop
  73          instruction. When the condition flag is toggled to true, the
  74          nop will be converted to a jump instruction to execute the
  75          conditional block of instructions.
  76
  77          This technique lowers overhead and stress on the branch prediction
  78          of the processor and generally makes the kernel faster. The update
  79          of the condition is slower, but those are always very rare.
  80
  81          ( On 32-bit x86, the necessary options added to the compiler
  82            flags may increase the size of the kernel slightly. )
  83
  84 config STATIC_KEYS_SELFTEST
  85         bool "Static key selftest"
  86         depends on JUMP_LABEL
  87         help
  88           Boot time self-test of the branch patching code.
  89
  90 config OPTPROBES
  91         def_bool y
  92         depends on KPROBES && HAVE_OPTPROBES
  93         depends on !PREEMPT
  94
  95 config KPROBES_ON_FTRACE
  96         def_bool y
  97         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
  98         depends on DYNAMIC_FTRACE_WITH_REGS
  99         help
 100          If function tracer is enabled and the arch supports full
 101          passing of pt_regs to function tracing, then kprobes can
 102          optimize on top of function tracing.
 103
 104 config UPROBES
 105         def_bool n
 106         depends on ARCH_SUPPORTS_UPROBES
 107         help
 108           Uprobes is the user-space counterpart to kprobes: they
 109           enable instrumentation applications (such as 'perf probe')
 110           to establish unintrusive probes in user-space binaries and
 111           libraries, by executing handler functions when the probes
 112           are hit by user-space applications.
 113
 114           ( These probes come in the form of single-byte breakpoints,
 115             managed by the kernel and kept transparent to the probed
 116             application. )
 117
 118 config HAVE_64BIT_ALIGNED_ACCESS
 119         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 120         help
 121           Some architectures require 64 bit accesses to be 64 bit
 122           aligned, which also requires structs containing 64 bit values
 123           to be 64 bit aligned too. This includes some 32 bit
 124           architectures which can do 64 bit accesses, as well as 64 bit
 125           architectures without unaligned access.
 126
 127           This symbol should be selected by an architecture if 64 bit
 128           accesses are required to be 64 bit aligned in this way even
 129           though it is not a 64 bit architecture.
 130
 131           See Documentation/unaligned-memory-access.txt for more
 132           information on the topic of unaligned memory accesses.
 133
 134 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 135         bool
 136         help
 137           Some architectures are unable to perform unaligned accesses
 138           without the use of get_unaligned/put_unaligned. Others are
 139           unable to perform such accesses efficiently (e.g. trap on
 140           unaligned access and require fixing it up in the exception
 141           handler.)
 142
 143           This symbol should be selected by an architecture if it can
 144           perform unaligned accesses efficiently to allow different
 145           code paths to be selected for these cases. Some network
 146           drivers, for example, could opt to not fix up alignment
 147           problems with received packets if doing so would not help
 148           much.
 149
 150           See Documentation/unaligned-memory-access.txt for more
 151           information on the topic of unaligned memory accesses.
 152
 153 config ARCH_USE_BUILTIN_BSWAP
 154        bool
 155        help
 156          Modern versions of GCC (since 4.4) have builtin functions
 157          for handling byte-swapping. Using these, instead of the old
 158          inline assembler that the architecture code provides in the
 159          __arch_bswapXX() macros, allows the compiler to see what's
 160          happening and offers more opportunity for optimisation. In
 161          particular, the compiler will be able to combine the byteswap
 162          with a nearby load or store and use load-and-swap or
 163          store-and-swap instructions if the architecture has them. It
 164          should almost *never* result in code which is worse than the
 165          hand-coded assembler in <asm/swab.h>.  But just in case it
 166          does, the use of the builtins is optional.
 167
 168          Any architecture with load-and-swap or store-and-swap
 169          instructions should set this. And it shouldn't hurt to set it
 170          on architectures that don't have such instructions.
 171
 172 config KRETPROBES
 173         def_bool y
 174         depends on KPROBES && HAVE_KRETPROBES
 175
 176 config USER_RETURN_NOTIFIER
 177         bool
 178         depends on HAVE_USER_RETURN_NOTIFIER
 179         help
 180           Provide a kernel-internal notification when a cpu is about to
 181           switch to user mode.
 182
 183 config HAVE_IOREMAP_PROT
 184         bool
 185
 186 config HAVE_KPROBES
 187         bool
 188
 189 config HAVE_KRETPROBES
 190         bool
 191
 192 config HAVE_OPTPROBES
 193         bool
 194
 195 config HAVE_KPROBES_ON_FTRACE
 196         bool
 197
 198 config HAVE_NMI
 199         bool
 200
 201 config HAVE_NMI_WATCHDOG
 202         depends on HAVE_NMI
 203         bool
 204 #
 205 # An arch should select this if it provides all these things:
 206 #
 207 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 208 #       arch_has_single_step()  if there is hardware single-step support
 209 #       arch_has_block_step()   if there is hardware block-step support
 210 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 211 #       linux/regset.h          user_regset interfaces
 212 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 213 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 214 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 215 #       signal delivery         calls tracehook_signal_handler()
 216 #
 217 config HAVE_ARCH_TRACEHOOK
 218         bool
 219
 220 config HAVE_DMA_CONTIGUOUS
 221         bool
 222
 223 config GENERIC_SMP_IDLE_THREAD
 224        bool
 225
 226 config GENERIC_IDLE_POLL_SETUP
 227        bool
 228
 229 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 230 config ARCH_HAS_SET_MEMORY
 231         bool
 232
 233 # Select if arch init_task initializer is different to init/init_task.c
 234 config ARCH_INIT_TASK
 235        bool
 236
 237 # Select if arch has its private alloc_task_struct() function
 238 config ARCH_TASK_STRUCT_ALLOCATOR
 239         bool
 240
 241 # Select if arch has its private alloc_thread_stack() function
 242 config ARCH_THREAD_STACK_ALLOCATOR
 243         bool
 244
 245 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 246 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 247         bool
 248
 249 config HAVE_REGS_AND_STACK_ACCESS_API
 250         bool
 251         help
 252           This symbol should be selected by an architecure if it supports
 253           the API needed to access registers and stack entries from pt_regs,
 254           declared in asm/ptrace.h
 255           For example the kprobes-based event tracer needs this API.
 256
 257 config HAVE_CLK
 258         bool
 259         help
 260           The <linux/clk.h> calls support software clock gating and
 261           thus are a key power management tool on many systems.
 262
 263 config HAVE_DMA_API_DEBUG
 264         bool
 265
 266 config HAVE_HW_BREAKPOINT
 267         bool
 268         depends on PERF_EVENTS
 269
 270 config HAVE_MIXED_BREAKPOINTS_REGS
 271         bool
 272         depends on HAVE_HW_BREAKPOINT
 273         help
 274           Depending on the arch implementation of hardware breakpoints,
 275           some of them have separate registers for data and instruction
 276           breakpoints addresses, others have mixed registers to store
 277           them but define the access type in a control register.
 278           Select this option if your arch implements breakpoints under the
 279           latter fashion.
 280
 281 config HAVE_USER_RETURN_NOTIFIER
 282         bool
 283
 284 config HAVE_PERF_EVENTS_NMI
 285         bool
 286         help
 287           System hardware can generate an NMI using the perf event
 288           subsystem.  Also has support for calculating CPU cycle events
 289           to determine how many clock cycles in a given period.
 290
 291 config HAVE_PERF_REGS
 292         bool
 293         help
 294           Support selective register dumps for perf events. This includes
 295           bit-mapping of each registers and a unique architecture id.
 296
 297 config HAVE_PERF_USER_STACK_DUMP
 298         bool
 299         help
 300           Support user stack dumps for perf event samples. This needs
 301           access to the user stack pointer which is not unified across
 302           architectures.
 303
 304 config HAVE_ARCH_JUMP_LABEL
 305         bool
 306
 307 config HAVE_RCU_TABLE_FREE
 308         bool
 309
 310 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 311         bool
 312
 313 config HAVE_ALIGNED_STRUCT_PAGE
 314         bool
 315         help
 316           This makes sure that struct pages are double word aligned and that
 317           e.g. the SLUB allocator can perform double word atomic operations
 318           on a struct page for better performance. However selecting this
 319           might increase the size of a struct page by a word.
 320
 321 config HAVE_CMPXCHG_LOCAL
 322         bool
 323
 324 config HAVE_CMPXCHG_DOUBLE
 325         bool
 326
 327 config ARCH_WANT_IPC_PARSE_VERSION
 328         bool
 329
 330 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 331         bool
 332
 333 config ARCH_WANT_OLD_COMPAT_IPC
 334         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 335         bool
 336
 337 config HAVE_ARCH_SECCOMP_FILTER
 338         bool
 339         help
 340           An arch should select this symbol if it provides all of these things:
 341           - syscall_get_arch()
 342           - syscall_get_arguments()
 343           - syscall_rollback()
 344           - syscall_set_return_value()
 345           - SIGSYS siginfo_t support
 346           - secure_computing is called from a ptrace_event()-safe context
 347           - secure_computing return value is checked and a return value of -1
 348             results in the system call being skipped immediately.
 349           - seccomp syscall wired up
 350
 351 config SECCOMP_FILTER
 352         def_bool y
 353         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 354         help
 355           Enable tasks to build secure computing environments defined
 356           in terms of Berkeley Packet Filter programs which implement
 357           task-defined system call filtering polices.
 358
 359           See Documentation/prctl/seccomp_filter.txt for details.
 360
 361 config HAVE_GCC_PLUGINS
 362         bool
 363         help
 364           An arch should select this symbol if it supports building with
 365           GCC plugins.
 366
 367 menuconfig GCC_PLUGINS
 368         bool "GCC plugins"
 369         depends on HAVE_GCC_PLUGINS
 370         depends on !COMPILE_TEST
 371         help
 372           GCC plugins are loadable modules that provide extra features to the
 373           compiler. They are useful for runtime instrumentation and static analysis.
 374
 375           See Documentation/gcc-plugins.txt for details.
 376
 377 config GCC_PLUGIN_CYC_COMPLEXITY
 378         bool "Compute the cyclomatic complexity of a function" if EXPERT
 379         depends on GCC_PLUGINS
 380         depends on !COMPILE_TEST
 381         help
 382           The complexity M of a function's control flow graph is defined as:
 383            M = E - N + 2P
 384           where
 385
 386           E = the number of edges
 387           N = the number of nodes
 388           P = the number of connected components (exit nodes).
 389
 390           Enabling this plugin reports the complexity to stderr during the
 391           build. It mainly serves as a simple example of how to create a
 392           gcc plugin for the kernel.
 393
 394 config GCC_PLUGIN_SANCOV
 395         bool
 396         depends on GCC_PLUGINS
 397         help
 398           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 399           basic blocks. It supports all gcc versions with plugin support (from
 400           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 401           by Dmitry Vyukov <dvyukov@google.com>.
 402
 403 config GCC_PLUGIN_LATENT_ENTROPY
 404         bool "Generate some entropy during boot and runtime"
 405         depends on GCC_PLUGINS
 406         help
 407           By saying Y here the kernel will instrument some kernel code to
 408           extract some entropy from both original and artificially created
 409           program state.  This will help especially embedded systems where
 410           there is little 'natural' source of entropy normally.  The cost
 411           is some slowdown of the boot process (about 0.5%) and fork and
 412           irq processing.
 413
 414           Note that entropy extracted this way is not cryptographically
 415           secure!
 416
 417           This plugin was ported from grsecurity/PaX. More information at:
 418            * https://grsecurity.net/
 419            * https://pax.grsecurity.net/
 420
 421 config GCC_PLUGIN_STRUCTLEAK
 422         bool "Force initialization of variables containing userspace addresses"
 423         depends on GCC_PLUGINS
 424         help
 425           This plugin zero-initializes any structures that containing a
 426           __user attribute. This can prevent some classes of information
 427           exposures.
 428
 429           This plugin was ported from grsecurity/PaX. More information at:
 430            * https://grsecurity.net/
 431            * https://pax.grsecurity.net/
 432
 433 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 434         bool "Report forcefully initialized variables"
 435         depends on GCC_PLUGIN_STRUCTLEAK
 436         depends on !COMPILE_TEST
 437         help
 438           This option will cause a warning to be printed each time the
 439           structleak plugin finds a variable it thinks needs to be
 440           initialized. Since not all existing initializers are detected
 441           by the plugin, this can produce false positive warnings.
 442
 443 config HAVE_CC_STACKPROTECTOR
 444         bool
 445         help
 446           An arch should select this symbol if:
 447           - its compiler supports the -fstack-protector option
 448           - it has implemented a stack canary (e.g. __stack_chk_guard)
 449
 450 config CC_STACKPROTECTOR
 451         def_bool n
 452         help
 453           Set when a stack-protector mode is enabled, so that the build
 454           can enable kernel-side support for the GCC feature.
 455
 456 choice
 457         prompt "Stack Protector buffer overflow detection"
 458         depends on HAVE_CC_STACKPROTECTOR
 459         default CC_STACKPROTECTOR_NONE
 460         help
 461           This option turns on the "stack-protector" GCC feature. This
 462           feature puts, at the beginning of functions, a canary value on
 463           the stack just before the return address, and validates
 464           the value just before actually returning.  Stack based buffer
 465           overflows (that need to overwrite this return address) now also
 466           overwrite the canary, which gets detected and the attack is then
 467           neutralized via a kernel panic.
 468
 469 config CC_STACKPROTECTOR_NONE
 470         bool "None"
 471         help
 472           Disable "stack-protector" GCC feature.
 473
 474 config CC_STACKPROTECTOR_REGULAR
 475         bool "Regular"
 476         select CC_STACKPROTECTOR
 477         help
 478           Functions will have the stack-protector canary logic added if they
 479           have an 8-byte or larger character array on the stack.
 480
 481           This feature requires gcc version 4.2 or above, or a distribution
 482           gcc with the feature backported ("-fstack-protector").
 483
 484           On an x86 "defconfig" build, this feature adds canary checks to
 485           about 3% of all kernel functions, which increases kernel code size
 486           by about 0.3%.
 487
 488 config CC_STACKPROTECTOR_STRONG
 489         bool "Strong"
 490         select CC_STACKPROTECTOR
 491         help
 492           Functions will have the stack-protector canary logic added in any
 493           of the following conditions:
 494
 495           - local variable's address used as part of the right hand side of an
 496             assignment or function argument
 497           - local variable is an array (or union containing an array),
 498             regardless of array type or length
 499           - uses register local variables
 500
 501           This feature requires gcc version 4.9 or above, or a distribution
 502           gcc with the feature backported ("-fstack-protector-strong").
 503
 504           On an x86 "defconfig" build, this feature adds canary checks to
 505           about 20% of all kernel functions, which increases the kernel code
 506           size by about 2%.
 507
 508 endchoice
 509
 510 config THIN_ARCHIVES
 511         bool
 512         help
 513           Select this if the architecture wants to use thin archives
 514           instead of ld -r to create the built-in.o files.
 515
 516 config LD_DEAD_CODE_DATA_ELIMINATION
 517         bool
 518         help
 519           Select this if the architecture wants to do dead code and
 520           data elimination with the linker by compiling with
 521           -ffunction-sections -fdata-sections and linking with
 522           --gc-sections.
 523
 524           This requires that the arch annotates or otherwise protects
 525           its external entry points from being discarded. Linker scripts
 526           must also merge .text.*, .data.*, and .bss.* correctly into
 527           output sections. Care must be taken not to pull in unrelated
 528           sections (e.g., '.text.init'). Typically '.' in section names
 529           is used to distinguish them from label names / C identifiers.
 530
 531 config HAVE_ARCH_WITHIN_STACK_FRAMES
 532         bool
 533         help
 534           An architecture should select this if it can walk the kernel stack
 535           frames to determine if an object is part of either the arguments
 536           or local variables (i.e. that it excludes saved return addresses,
 537           and similar) by implementing an inline arch_within_stack_frames(),
 538           which is used by CONFIG_HARDENED_USERCOPY.
 539
 540 config HAVE_CONTEXT_TRACKING
 541         bool
 542         help
 543           Provide kernel/user boundaries probes necessary for subsystems
 544           that need it, such as userspace RCU extended quiescent state.
 545           Syscalls need to be wrapped inside user_exit()-user_enter() through
 546           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 547           wrapped as well. Irqs are already protected inside
 548           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 549           irq exit still need to be protected.
 550
 551 config HAVE_VIRT_CPU_ACCOUNTING
 552         bool
 553
 554 config ARCH_HAS_SCALED_CPUTIME
 555         bool
 556
 557 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 558         bool
 559         default y if 64BIT
 560         help
 561           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 562           Before enabling this option, arch code must be audited
 563           to ensure there are no races in concurrent read/write of
 564           cputime_t. For example, reading/writing 64-bit cputime_t on
 565           some 32-bit arches may require multiple accesses, so proper
 566           locking is needed to protect against concurrent accesses.
 567
 568
 569 config HAVE_IRQ_TIME_ACCOUNTING
 570         bool
 571         help
 572           Archs need to ensure they use a high enough resolution clock to
 573           support irq time accounting and then call enable_sched_clock_irqtime().
 574
 575 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 576         bool
 577
 578 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 579         bool
 580
 581 config HAVE_ARCH_HUGE_VMAP
 582         bool
 583
 584 config HAVE_ARCH_SOFT_DIRTY
 585         bool
 586
 587 config HAVE_MOD_ARCH_SPECIFIC
 588         bool
 589         help
 590           The arch uses struct mod_arch_specific to store data.  Many arches
 591           just need a simple module loader without arch specific data - those
 592           should not enable this.
 593
 594 config MODULES_USE_ELF_RELA
 595         bool
 596         help
 597           Modules only use ELF RELA relocations.  Modules with ELF REL
 598           relocations will give an error.
 599
 600 config MODULES_USE_ELF_REL
 601         bool
 602         help
 603           Modules only use ELF REL relocations.  Modules with ELF RELA
 604           relocations will give an error.
 605
 606 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 607         bool
 608         help
 609           Some architectures generate an _ in front of C symbols; things like
 610           module loading and assembly files need to know about this.
 611
 612 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 613         bool
 614         help
 615           Architecture doesn't only execute the irq handler on the irq stack
 616           but also irq_exit(). This way we can process softirqs on this irq
 617           stack instead of switching to a new one when we call __do_softirq()
 618           in the end of an hardirq.
 619           This spares a stack switch and improves cache usage on softirq
 620           processing.
 621
 622 config PGTABLE_LEVELS
 623         int
 624         default 2
 625
 626 config ARCH_HAS_ELF_RANDOMIZE
 627         bool
 628         help
 629           An architecture supports choosing randomized locations for
 630           stack, mmap, brk, and ET_DYN. Defined functions:
 631           - arch_mmap_rnd()
 632           - arch_randomize_brk()
 633
 634 config HAVE_ARCH_MMAP_RND_BITS
 635         bool
 636         help
 637           An arch should select this symbol if it supports setting a variable
 638           number of bits for use in establishing the base address for mmap
 639           allocations, has MMU enabled and provides values for both:
 640           - ARCH_MMAP_RND_BITS_MIN
 641           - ARCH_MMAP_RND_BITS_MAX
 642
 643 config HAVE_EXIT_THREAD
 644         bool
 645         help
 646           An architecture implements exit_thread.
 647
 648 config ARCH_MMAP_RND_BITS_MIN
 649         int
 650
 651 config ARCH_MMAP_RND_BITS_MAX
 652         int
 653
 654 config ARCH_MMAP_RND_BITS_DEFAULT
 655         int
 656
 657 config ARCH_MMAP_RND_BITS
 658         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 659         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 660         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 661         default ARCH_MMAP_RND_BITS_MIN
 662         depends on HAVE_ARCH_MMAP_RND_BITS
 663         help
 664           This value can be used to select the number of bits to use to
 665           determine the random offset to the base address of vma regions
 666           resulting from mmap allocations. This value will be bounded
 667           by the architecture's minimum and maximum supported values.
 668
 669           This value can be changed after boot using the
 670           /proc/sys/vm/mmap_rnd_bits tunable
 671
 672 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 673         bool
 674         help
 675           An arch should select this symbol if it supports running applications
 676           in compatibility mode, supports setting a variable number of bits for
 677           use in establishing the base address for mmap allocations, has MMU
 678           enabled and provides values for both:
 679           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 680           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 681
 682 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 683         int
 684
 685 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 686         int
 687
 688 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 689         int
 690
 691 config ARCH_MMAP_RND_COMPAT_BITS
 692         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 693         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 694         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 695         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 696         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 697         help
 698           This value can be used to select the number of bits to use to
 699           determine the random offset to the base address of vma regions
 700           resulting from mmap allocations for compatible applications This
 701           value will be bounded by the architecture's minimum and maximum
 702           supported values.
 703
 704           This value can be changed after boot using the
 705           /proc/sys/vm/mmap_rnd_compat_bits tunable
 706
 707 config HAVE_ARCH_COMPAT_MMAP_BASES
 708         bool
 709         help
 710           This allows 64bit applications to invoke 32-bit mmap() syscall
 711           and vice-versa 32-bit applications to call 64-bit mmap().
 712           Required for applications doing different bitness syscalls.
 713
 714 config HAVE_COPY_THREAD_TLS
 715         bool
 716         help
 717           Architecture provides copy_thread_tls to accept tls argument via
 718           normal C parameter passing, rather than extracting the syscall
 719           argument from pt_regs.
 720
 721 config HAVE_STACK_VALIDATION
 722         bool
 723         help
 724           Architecture supports the 'objtool check' host tool command, which
 725           performs compile-time stack metadata validation.
 726
 727 config HAVE_RELIABLE_STACKTRACE
 728         bool
 729         help
 730           Architecture has a save_stack_trace_tsk_reliable() function which
 731           only returns a stack trace if it can guarantee the trace is reliable.
 732
 733 config HAVE_ARCH_HASH
 734         bool
 735         default n
 736         help
 737           If this is set, the architecture provides an <asm/hash.h>
 738           file which provides platform-specific implementations of some
 739           functions in <linux/hash.h> or fs/namei.c.
 740
 741 config ISA_BUS_API
 742         def_bool ISA
 743
 744 #
 745 # ABI hall of shame
 746 #
 747 config CLONE_BACKWARDS
 748         bool
 749         help
 750           Architecture has tls passed as the 4th argument of clone(2),
 751           not the 5th one.
 752
 753 config CLONE_BACKWARDS2
 754         bool
 755         help
 756           Architecture has the first two arguments of clone(2) swapped.
 757
 758 config CLONE_BACKWARDS3
 759         bool
 760         help
 761           Architecture has tls passed as the 3rd argument of clone(2),
 762           not the 5th one.
 763
 764 config ODD_RT_SIGACTION
 765         bool
 766         help
 767           Architecture has unusual rt_sigaction(2) arguments
 768
 769 config OLD_SIGSUSPEND
 770         bool
 771         help
 772           Architecture has old sigsuspend(2) syscall, of one-argument variety
 773
 774 config OLD_SIGSUSPEND3
 775         bool
 776         help
 777           Even weirder antique ABI - three-argument sigsuspend(2)
 778
 779 config OLD_SIGACTION
 780         bool
 781         help
 782           Architecture has old sigaction(2) syscall.  Nope, not the same
 783           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 784           but fairly different variant of sigaction(2), thanks to OSF/1
 785           compatibility...
 786
 787 config COMPAT_OLD_SIGACTION
 788         bool
 789
 790 config ARCH_NO_COHERENT_DMA_MMAP
 791         bool
 792
 793 config CPU_NO_EFFICIENT_FFS
 794         def_bool n
 795
 796 config HAVE_ARCH_VMAP_STACK
 797         def_bool n
 798         help
 799           An arch should select this symbol if it can support kernel stacks
 800           in vmalloc space.  This means:
 801
 802           - vmalloc space must be large enough to hold many kernel stacks.
 803             This may rule out many 32-bit architectures.
 804
 805           - Stacks in vmalloc space need to work reliably.  For example, if
 806             vmap page tables are created on demand, either this mechanism
 807             needs to work while the stack points to a virtual address with
 808             unpopulated page tables or arch code (switch_to() and switch_mm(),
 809             most likely) needs to ensure that the stack's page table entries
 810             are populated before running on a possibly unpopulated stack.
 811
 812           - If the stack overflows into a guard page, something reasonable
 813             should happen.  The definition of "reasonable" is flexible, but
 814             instantly rebooting without logging anything would be unfriendly.
 815
 816 config VMAP_STACK
 817         default y
 818         bool "Use a virtually-mapped stack"
 819         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 820         ---help---
 821           Enable this if you want the use virtually-mapped kernel stacks
 822           with guard pages.  This causes kernel stack overflows to be
 823           caught immediately rather than causing difficult-to-diagnose
 824           corruption.
 825
 826           This is presently incompatible with KASAN because KASAN expects
 827           the stack to map directly to the KASAN shadow map using a formula
 828           that is incorrect if the stack is in vmalloc space.
 829
 830 config ARCH_OPTIONAL_KERNEL_RWX
 831         def_bool n
 832
 833 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 834         def_bool n
 835
 836 config ARCH_HAS_STRICT_KERNEL_RWX
 837         def_bool n
 838
 839 config STRICT_KERNEL_RWX
 840         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 841         depends on ARCH_HAS_STRICT_KERNEL_RWX
 842         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 843         help
 844           If this is set, kernel text and rodata memory will be made read-only,
 845           and non-text memory will be made non-executable. This provides
 846           protection against certain security exploits (e.g. executing the heap
 847           or modifying text)
 848
 849           These features are considered standard security practice these days.
 850           You should say Y here in almost all cases.
 851
 852 config ARCH_HAS_STRICT_MODULE_RWX
 853         def_bool n
 854
 855 config STRICT_MODULE_RWX
 856         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 857         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 858         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 859         help
 860           If this is set, module text and rodata memory will be made read-only,
 861           and non-text memory will be made non-executable. This provides
 862           protection against certain security exploits (e.g. writing to text)
 863
 864 config ARCH_WANT_RELAX_ORDER
 865         bool
 866
 867 source "kernel/gcov/Kconfig"