arch/Kconfig

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