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_WEAK_RELEASE_ACQUIRE
 328         bool
 329
 330 config ARCH_WANT_IPC_PARSE_VERSION
 331         bool
 332
 333 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 334         bool
 335
 336 config ARCH_WANT_OLD_COMPAT_IPC
 337         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 338         bool
 339
 340 config HAVE_ARCH_SECCOMP_FILTER
 341         bool
 342         help
 343           An arch should select this symbol if it provides all of these things:
 344           - syscall_get_arch()
 345           - syscall_get_arguments()
 346           - syscall_rollback()
 347           - syscall_set_return_value()
 348           - SIGSYS siginfo_t support
 349           - secure_computing is called from a ptrace_event()-safe context
 350           - secure_computing return value is checked and a return value of -1
 351             results in the system call being skipped immediately.
 352           - seccomp syscall wired up
 353
 354 config SECCOMP_FILTER
 355         def_bool y
 356         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 357         help
 358           Enable tasks to build secure computing environments defined
 359           in terms of Berkeley Packet Filter programs which implement
 360           task-defined system call filtering polices.
 361
 362           See Documentation/prctl/seccomp_filter.txt for details.
 363
 364 config HAVE_GCC_PLUGINS
 365         bool
 366         help
 367           An arch should select this symbol if it supports building with
 368           GCC plugins.
 369
 370 menuconfig GCC_PLUGINS
 371         bool "GCC plugins"
 372         depends on HAVE_GCC_PLUGINS
 373         depends on !COMPILE_TEST
 374         help
 375           GCC plugins are loadable modules that provide extra features to the
 376           compiler. They are useful for runtime instrumentation and static analysis.
 377
 378           See Documentation/gcc-plugins.txt for details.
 379
 380 config GCC_PLUGIN_CYC_COMPLEXITY
 381         bool "Compute the cyclomatic complexity of a function" if EXPERT
 382         depends on GCC_PLUGINS
 383         depends on !COMPILE_TEST
 384         help
 385           The complexity M of a function's control flow graph is defined as:
 386            M = E - N + 2P
 387           where
 388
 389           E = the number of edges
 390           N = the number of nodes
 391           P = the number of connected components (exit nodes).
 392
 393           Enabling this plugin reports the complexity to stderr during the
 394           build. It mainly serves as a simple example of how to create a
 395           gcc plugin for the kernel.
 396
 397 config GCC_PLUGIN_SANCOV
 398         bool
 399         depends on GCC_PLUGINS
 400         help
 401           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 402           basic blocks. It supports all gcc versions with plugin support (from
 403           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 404           by Dmitry Vyukov <dvyukov@google.com>.
 405
 406 config GCC_PLUGIN_LATENT_ENTROPY
 407         bool "Generate some entropy during boot and runtime"
 408         depends on GCC_PLUGINS
 409         help
 410           By saying Y here the kernel will instrument some kernel code to
 411           extract some entropy from both original and artificially created
 412           program state.  This will help especially embedded systems where
 413           there is little 'natural' source of entropy normally.  The cost
 414           is some slowdown of the boot process (about 0.5%) and fork and
 415           irq processing.
 416
 417           Note that entropy extracted this way is not cryptographically
 418           secure!
 419
 420           This plugin was ported from grsecurity/PaX. More information at:
 421            * https://grsecurity.net/
 422            * https://pax.grsecurity.net/
 423
 424 config GCC_PLUGIN_STRUCTLEAK
 425         bool "Force initialization of variables containing userspace addresses"
 426         depends on GCC_PLUGINS
 427         help
 428           This plugin zero-initializes any structures that containing a
 429           __user attribute. This can prevent some classes of information
 430           exposures.
 431
 432           This plugin was ported from grsecurity/PaX. More information at:
 433            * https://grsecurity.net/
 434            * https://pax.grsecurity.net/
 435
 436 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 437         bool "Report forcefully initialized variables"
 438         depends on GCC_PLUGIN_STRUCTLEAK
 439         depends on !COMPILE_TEST
 440         help
 441           This option will cause a warning to be printed each time the
 442           structleak plugin finds a variable it thinks needs to be
 443           initialized. Since not all existing initializers are detected
 444           by the plugin, this can produce false positive warnings.
 445
 446 config HAVE_CC_STACKPROTECTOR
 447         bool
 448         help
 449           An arch should select this symbol if:
 450           - its compiler supports the -fstack-protector option
 451           - it has implemented a stack canary (e.g. __stack_chk_guard)
 452
 453 config CC_STACKPROTECTOR
 454         def_bool n
 455         help
 456           Set when a stack-protector mode is enabled, so that the build
 457           can enable kernel-side support for the GCC feature.
 458
 459 choice
 460         prompt "Stack Protector buffer overflow detection"
 461         depends on HAVE_CC_STACKPROTECTOR
 462         default CC_STACKPROTECTOR_NONE
 463         help
 464           This option turns on the "stack-protector" GCC feature. This
 465           feature puts, at the beginning of functions, a canary value on
 466           the stack just before the return address, and validates
 467           the value just before actually returning.  Stack based buffer
 468           overflows (that need to overwrite this return address) now also
 469           overwrite the canary, which gets detected and the attack is then
 470           neutralized via a kernel panic.
 471
 472 config CC_STACKPROTECTOR_NONE
 473         bool "None"
 474         help
 475           Disable "stack-protector" GCC feature.
 476
 477 config CC_STACKPROTECTOR_REGULAR
 478         bool "Regular"
 479         select CC_STACKPROTECTOR
 480         help
 481           Functions will have the stack-protector canary logic added if they
 482           have an 8-byte or larger character array on the stack.
 483
 484           This feature requires gcc version 4.2 or above, or a distribution
 485           gcc with the feature backported ("-fstack-protector").
 486
 487           On an x86 "defconfig" build, this feature adds canary checks to
 488           about 3% of all kernel functions, which increases kernel code size
 489           by about 0.3%.
 490
 491 config CC_STACKPROTECTOR_STRONG
 492         bool "Strong"
 493         select CC_STACKPROTECTOR
 494         help
 495           Functions will have the stack-protector canary logic added in any
 496           of the following conditions:
 497
 498           - local variable's address used as part of the right hand side of an
 499             assignment or function argument
 500           - local variable is an array (or union containing an array),
 501             regardless of array type or length
 502           - uses register local variables
 503
 504           This feature requires gcc version 4.9 or above, or a distribution
 505           gcc with the feature backported ("-fstack-protector-strong").
 506
 507           On an x86 "defconfig" build, this feature adds canary checks to
 508           about 20% of all kernel functions, which increases the kernel code
 509           size by about 2%.
 510
 511 endchoice
 512
 513 config THIN_ARCHIVES
 514         bool
 515         help
 516           Select this if the architecture wants to use thin archives
 517           instead of ld -r to create the built-in.o files.
 518
 519 config LD_DEAD_CODE_DATA_ELIMINATION
 520         bool
 521         help
 522           Select this if the architecture wants to do dead code and
 523           data elimination with the linker by compiling with
 524           -ffunction-sections -fdata-sections and linking with
 525           --gc-sections.
 526
 527           This requires that the arch annotates or otherwise protects
 528           its external entry points from being discarded. Linker scripts
 529           must also merge .text.*, .data.*, and .bss.* correctly into
 530           output sections. Care must be taken not to pull in unrelated
 531           sections (e.g., '.text.init'). Typically '.' in section names
 532           is used to distinguish them from label names / C identifiers.
 533
 534 config HAVE_ARCH_WITHIN_STACK_FRAMES
 535         bool
 536         help
 537           An architecture should select this if it can walk the kernel stack
 538           frames to determine if an object is part of either the arguments
 539           or local variables (i.e. that it excludes saved return addresses,
 540           and similar) by implementing an inline arch_within_stack_frames(),
 541           which is used by CONFIG_HARDENED_USERCOPY.
 542
 543 config HAVE_CONTEXT_TRACKING
 544         bool
 545         help
 546           Provide kernel/user boundaries probes necessary for subsystems
 547           that need it, such as userspace RCU extended quiescent state.
 548           Syscalls need to be wrapped inside user_exit()-user_enter() through
 549           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 550           wrapped as well. Irqs are already protected inside
 551           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 552           irq exit still need to be protected.
 553
 554 config HAVE_VIRT_CPU_ACCOUNTING
 555         bool
 556
 557 config ARCH_HAS_SCALED_CPUTIME
 558         bool
 559
 560 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 561         bool
 562         default y if 64BIT
 563         help
 564           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 565           Before enabling this option, arch code must be audited
 566           to ensure there are no races in concurrent read/write of
 567           cputime_t. For example, reading/writing 64-bit cputime_t on
 568           some 32-bit arches may require multiple accesses, so proper
 569           locking is needed to protect against concurrent accesses.
 570
 571
 572 config HAVE_IRQ_TIME_ACCOUNTING
 573         bool
 574         help
 575           Archs need to ensure they use a high enough resolution clock to
 576           support irq time accounting and then call enable_sched_clock_irqtime().
 577
 578 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 579         bool
 580
 581 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 582         bool
 583
 584 config HAVE_ARCH_HUGE_VMAP
 585         bool
 586
 587 config HAVE_ARCH_SOFT_DIRTY
 588         bool
 589
 590 config HAVE_MOD_ARCH_SPECIFIC
 591         bool
 592         help
 593           The arch uses struct mod_arch_specific to store data.  Many arches
 594           just need a simple module loader without arch specific data - those
 595           should not enable this.
 596
 597 config MODULES_USE_ELF_RELA
 598         bool
 599         help
 600           Modules only use ELF RELA relocations.  Modules with ELF REL
 601           relocations will give an error.
 602
 603 config MODULES_USE_ELF_REL
 604         bool
 605         help
 606           Modules only use ELF REL relocations.  Modules with ELF RELA
 607           relocations will give an error.
 608
 609 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 610         bool
 611         help
 612           Some architectures generate an _ in front of C symbols; things like
 613           module loading and assembly files need to know about this.
 614
 615 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 616         bool
 617         help
 618           Architecture doesn't only execute the irq handler on the irq stack
 619           but also irq_exit(). This way we can process softirqs on this irq
 620           stack instead of switching to a new one when we call __do_softirq()
 621           in the end of an hardirq.
 622           This spares a stack switch and improves cache usage on softirq
 623           processing.
 624
 625 config PGTABLE_LEVELS
 626         int
 627         default 2
 628
 629 config ARCH_HAS_ELF_RANDOMIZE
 630         bool
 631         help
 632           An architecture supports choosing randomized locations for
 633           stack, mmap, brk, and ET_DYN. Defined functions:
 634           - arch_mmap_rnd()
 635           - arch_randomize_brk()
 636
 637 config HAVE_ARCH_MMAP_RND_BITS
 638         bool
 639         help
 640           An arch should select this symbol if it supports setting a variable
 641           number of bits for use in establishing the base address for mmap
 642           allocations, has MMU enabled and provides values for both:
 643           - ARCH_MMAP_RND_BITS_MIN
 644           - ARCH_MMAP_RND_BITS_MAX
 645
 646 config HAVE_EXIT_THREAD
 647         bool
 648         help
 649           An architecture implements exit_thread.
 650
 651 config ARCH_MMAP_RND_BITS_MIN
 652         int
 653
 654 config ARCH_MMAP_RND_BITS_MAX
 655         int
 656
 657 config ARCH_MMAP_RND_BITS_DEFAULT
 658         int
 659
 660 config ARCH_MMAP_RND_BITS
 661         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 662         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 663         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 664         default ARCH_MMAP_RND_BITS_MIN
 665         depends on HAVE_ARCH_MMAP_RND_BITS
 666         help
 667           This value can be used to select the number of bits to use to
 668           determine the random offset to the base address of vma regions
 669           resulting from mmap allocations. This value will be bounded
 670           by the architecture's minimum and maximum supported values.
 671
 672           This value can be changed after boot using the
 673           /proc/sys/vm/mmap_rnd_bits tunable
 674
 675 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 676         bool
 677         help
 678           An arch should select this symbol if it supports running applications
 679           in compatibility mode, supports setting a variable number of bits for
 680           use in establishing the base address for mmap allocations, has MMU
 681           enabled and provides values for both:
 682           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 683           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 684
 685 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 686         int
 687
 688 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 689         int
 690
 691 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 692         int
 693
 694 config ARCH_MMAP_RND_COMPAT_BITS
 695         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 696         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 697         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 698         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 699         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 700         help
 701           This value can be used to select the number of bits to use to
 702           determine the random offset to the base address of vma regions
 703           resulting from mmap allocations for compatible applications This
 704           value will be bounded by the architecture's minimum and maximum
 705           supported values.
 706
 707           This value can be changed after boot using the
 708           /proc/sys/vm/mmap_rnd_compat_bits tunable
 709
 710 config HAVE_ARCH_COMPAT_MMAP_BASES
 711         bool
 712         help
 713           This allows 64bit applications to invoke 32-bit mmap() syscall
 714           and vice-versa 32-bit applications to call 64-bit mmap().
 715           Required for applications doing different bitness syscalls.
 716
 717 config HAVE_COPY_THREAD_TLS
 718         bool
 719         help
 720           Architecture provides copy_thread_tls to accept tls argument via
 721           normal C parameter passing, rather than extracting the syscall
 722           argument from pt_regs.
 723
 724 config HAVE_STACK_VALIDATION
 725         bool
 726         help
 727           Architecture supports the 'objtool check' host tool command, which
 728           performs compile-time stack metadata validation.
 729
 730 config HAVE_RELIABLE_STACKTRACE
 731         bool
 732         help
 733           Architecture has a save_stack_trace_tsk_reliable() function which
 734           only returns a stack trace if it can guarantee the trace is reliable.
 735
 736 config HAVE_ARCH_HASH
 737         bool
 738         default n
 739         help
 740           If this is set, the architecture provides an <asm/hash.h>
 741           file which provides platform-specific implementations of some
 742           functions in <linux/hash.h> or fs/namei.c.
 743
 744 config ISA_BUS_API
 745         def_bool ISA
 746
 747 #
 748 # ABI hall of shame
 749 #
 750 config CLONE_BACKWARDS
 751         bool
 752         help
 753           Architecture has tls passed as the 4th argument of clone(2),
 754           not the 5th one.
 755
 756 config CLONE_BACKWARDS2
 757         bool
 758         help
 759           Architecture has the first two arguments of clone(2) swapped.
 760
 761 config CLONE_BACKWARDS3
 762         bool
 763         help
 764           Architecture has tls passed as the 3rd argument of clone(2),
 765           not the 5th one.
 766
 767 config ODD_RT_SIGACTION
 768         bool
 769         help
 770           Architecture has unusual rt_sigaction(2) arguments
 771
 772 config OLD_SIGSUSPEND
 773         bool
 774         help
 775           Architecture has old sigsuspend(2) syscall, of one-argument variety
 776
 777 config OLD_SIGSUSPEND3
 778         bool
 779         help
 780           Even weirder antique ABI - three-argument sigsuspend(2)
 781
 782 config OLD_SIGACTION
 783         bool
 784         help
 785           Architecture has old sigaction(2) syscall.  Nope, not the same
 786           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 787           but fairly different variant of sigaction(2), thanks to OSF/1
 788           compatibility...
 789
 790 config COMPAT_OLD_SIGACTION
 791         bool
 792
 793 config ARCH_NO_COHERENT_DMA_MMAP
 794         bool
 795
 796 config CPU_NO_EFFICIENT_FFS
 797         def_bool n
 798
 799 config HAVE_ARCH_VMAP_STACK
 800         def_bool n
 801         help
 802           An arch should select this symbol if it can support kernel stacks
 803           in vmalloc space.  This means:
 804
 805           - vmalloc space must be large enough to hold many kernel stacks.
 806             This may rule out many 32-bit architectures.
 807
 808           - Stacks in vmalloc space need to work reliably.  For example, if
 809             vmap page tables are created on demand, either this mechanism
 810             needs to work while the stack points to a virtual address with
 811             unpopulated page tables or arch code (switch_to() and switch_mm(),
 812             most likely) needs to ensure that the stack's page table entries
 813             are populated before running on a possibly unpopulated stack.
 814
 815           - If the stack overflows into a guard page, something reasonable
 816             should happen.  The definition of "reasonable" is flexible, but
 817             instantly rebooting without logging anything would be unfriendly.
 818
 819 config VMAP_STACK
 820         default y
 821         bool "Use a virtually-mapped stack"
 822         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 823         ---help---
 824           Enable this if you want the use virtually-mapped kernel stacks
 825           with guard pages.  This causes kernel stack overflows to be
 826           caught immediately rather than causing difficult-to-diagnose
 827           corruption.
 828
 829           This is presently incompatible with KASAN because KASAN expects
 830           the stack to map directly to the KASAN shadow map using a formula
 831           that is incorrect if the stack is in vmalloc space.
 832
 833 config ARCH_OPTIONAL_KERNEL_RWX
 834         def_bool n
 835
 836 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 837         def_bool n
 838
 839 config ARCH_HAS_STRICT_KERNEL_RWX
 840         def_bool n
 841
 842 config STRICT_KERNEL_RWX
 843         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 844         depends on ARCH_HAS_STRICT_KERNEL_RWX
 845         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 846         help
 847           If this is set, kernel text and rodata memory will be made read-only,
 848           and non-text memory will be made non-executable. This provides
 849           protection against certain security exploits (e.g. executing the heap
 850           or modifying text)
 851
 852           These features are considered standard security practice these days.
 853           You should say Y here in almost all cases.
 854
 855 config ARCH_HAS_STRICT_MODULE_RWX
 856         def_bool n
 857
 858 config STRICT_MODULE_RWX
 859         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 860         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 861         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 862         help
 863           If this is set, module text and rodata memory will be made read-only,
 864           and non-text memory will be made non-executable. This provides
 865           protection against certain security exploits (e.g. writing to text)
 866
 867 config ARCH_WANT_RELAX_ORDER
 868         bool
 869
 870 source "kernel/gcov/Kconfig"