arch/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 #
   3 # General architecture dependent options
   4 #
   5
   6 config CRASH_CORE
   7         bool
   8
   9 config KEXEC_CORE
  10         select CRASH_CORE
  11         bool
  12
  13 config HAVE_IMA_KEXEC
  14         bool
  15
  16 config OPROFILE
  17         tristate "OProfile system profiling"
  18         depends on PROFILING
  19         depends on HAVE_OPROFILE
  20         select RING_BUFFER
  21         select RING_BUFFER_ALLOW_SWAP
  22         help
  23           OProfile is a profiling system capable of profiling the
  24           whole system, include the kernel, kernel modules, libraries,
  25           and applications.
  26
  27           If unsure, say N.
  28
  29 config OPROFILE_EVENT_MULTIPLEX
  30         bool "OProfile multiplexing support (EXPERIMENTAL)"
  31         default n
  32         depends on OPROFILE && X86
  33         help
  34           The number of hardware counters is limited. The multiplexing
  35           feature enables OProfile to gather more events than counters
  36           are provided by the hardware. This is realized by switching
  37           between events at a user specified time interval.
  38
  39           If unsure, say N.
  40
  41 config HAVE_OPROFILE
  42         bool
  43
  44 config OPROFILE_NMI_TIMER
  45         def_bool y
  46         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  47
  48 config KPROBES
  49         bool "Kprobes"
  50         depends on MODULES
  51         depends on HAVE_KPROBES
  52         select KALLSYMS
  53         help
  54           Kprobes allows you to trap at almost any kernel address and
  55           execute a callback function.  register_kprobe() establishes
  56           a probepoint and specifies the callback.  Kprobes is useful
  57           for kernel debugging, non-intrusive instrumentation and testing.
  58           If in doubt, say "N".
  59
  60 config JUMP_LABEL
  61        bool "Optimize very unlikely/likely branches"
  62        depends on HAVE_ARCH_JUMP_LABEL
  63        help
  64          This option enables a transparent branch optimization that
  65          makes certain almost-always-true or almost-always-false branch
  66          conditions even cheaper to execute within the kernel.
  67
  68          Certain performance-sensitive kernel code, such as trace points,
  69          scheduler functionality, networking code and KVM have such
  70          branches and include support for this optimization technique.
  71
  72          If it is detected that the compiler has support for "asm goto",
  73          the kernel will compile such branches with just a nop
  74          instruction. When the condition flag is toggled to true, the
  75          nop will be converted to a jump instruction to execute the
  76          conditional block of instructions.
  77
  78          This technique lowers overhead and stress on the branch prediction
  79          of the processor and generally makes the kernel faster. The update
  80          of the condition is slower, but those are always very rare.
  81
  82          ( On 32-bit x86, the necessary options added to the compiler
  83            flags may increase the size of the kernel slightly. )
  84
  85 config STATIC_KEYS_SELFTEST
  86         bool "Static key selftest"
  87         depends on JUMP_LABEL
  88         help
  89           Boot time self-test of the branch patching code.
  90
  91 config OPTPROBES
  92         def_bool y
  93         depends on KPROBES && HAVE_OPTPROBES
  94         select TASKS_RCU if PREEMPT
  95
  96 config KPROBES_ON_FTRACE
  97         def_bool y
  98         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
  99         depends on DYNAMIC_FTRACE_WITH_REGS
 100         help
 101          If function tracer is enabled and the arch supports full
 102          passing of pt_regs to function tracing, then kprobes can
 103          optimize on top of function tracing.
 104
 105 config UPROBES
 106         def_bool n
 107         depends on ARCH_SUPPORTS_UPROBES
 108         help
 109           Uprobes is the user-space counterpart to kprobes: they
 110           enable instrumentation applications (such as 'perf probe')
 111           to establish unintrusive probes in user-space binaries and
 112           libraries, by executing handler functions when the probes
 113           are hit by user-space applications.
 114
 115           ( These probes come in the form of single-byte breakpoints,
 116             managed by the kernel and kept transparent to the probed
 117             application. )
 118
 119 config HAVE_64BIT_ALIGNED_ACCESS
 120         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 121         help
 122           Some architectures require 64 bit accesses to be 64 bit
 123           aligned, which also requires structs containing 64 bit values
 124           to be 64 bit aligned too. This includes some 32 bit
 125           architectures which can do 64 bit accesses, as well as 64 bit
 126           architectures without unaligned access.
 127
 128           This symbol should be selected by an architecture if 64 bit
 129           accesses are required to be 64 bit aligned in this way even
 130           though it is not a 64 bit architecture.
 131
 132           See Documentation/unaligned-memory-access.txt for more
 133           information on the topic of unaligned memory accesses.
 134
 135 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 136         bool
 137         help
 138           Some architectures are unable to perform unaligned accesses
 139           without the use of get_unaligned/put_unaligned. Others are
 140           unable to perform such accesses efficiently (e.g. trap on
 141           unaligned access and require fixing it up in the exception
 142           handler.)
 143
 144           This symbol should be selected by an architecture if it can
 145           perform unaligned accesses efficiently to allow different
 146           code paths to be selected for these cases. Some network
 147           drivers, for example, could opt to not fix up alignment
 148           problems with received packets if doing so would not help
 149           much.
 150
 151           See Documentation/unaligned-memory-access.txt for more
 152           information on the topic of unaligned memory accesses.
 153
 154 config ARCH_USE_BUILTIN_BSWAP
 155        bool
 156        help
 157          Modern versions of GCC (since 4.4) have builtin functions
 158          for handling byte-swapping. Using these, instead of the old
 159          inline assembler that the architecture code provides in the
 160          __arch_bswapXX() macros, allows the compiler to see what's
 161          happening and offers more opportunity for optimisation. In
 162          particular, the compiler will be able to combine the byteswap
 163          with a nearby load or store and use load-and-swap or
 164          store-and-swap instructions if the architecture has them. It
 165          should almost *never* result in code which is worse than the
 166          hand-coded assembler in <asm/swab.h>.  But just in case it
 167          does, the use of the builtins is optional.
 168
 169          Any architecture with load-and-swap or store-and-swap
 170          instructions should set this. And it shouldn't hurt to set it
 171          on architectures that don't have such instructions.
 172
 173 config KRETPROBES
 174         def_bool y
 175         depends on KPROBES && HAVE_KRETPROBES
 176
 177 config USER_RETURN_NOTIFIER
 178         bool
 179         depends on HAVE_USER_RETURN_NOTIFIER
 180         help
 181           Provide a kernel-internal notification when a cpu is about to
 182           switch to user mode.
 183
 184 config HAVE_IOREMAP_PROT
 185         bool
 186
 187 config HAVE_KPROBES
 188         bool
 189
 190 config HAVE_KRETPROBES
 191         bool
 192
 193 config HAVE_OPTPROBES
 194         bool
 195
 196 config HAVE_KPROBES_ON_FTRACE
 197         bool
 198
 199 config HAVE_FUNCTION_ERROR_INJECTION
 200         bool
 201
 202 config HAVE_NMI
 203         bool
 204
 205 #
 206 # An arch should select this if it provides all these things:
 207 #
 208 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 209 #       arch_has_single_step()  if there is hardware single-step support
 210 #       arch_has_block_step()   if there is hardware block-step support
 211 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 212 #       linux/regset.h          user_regset interfaces
 213 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 214 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 215 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 216 #       signal delivery         calls tracehook_signal_handler()
 217 #
 218 config HAVE_ARCH_TRACEHOOK
 219         bool
 220
 221 config HAVE_DMA_CONTIGUOUS
 222         bool
 223
 224 config GENERIC_SMP_IDLE_THREAD
 225        bool
 226
 227 config GENERIC_IDLE_POLL_SETUP
 228        bool
 229
 230 config ARCH_HAS_FORTIFY_SOURCE
 231         bool
 232         help
 233           An architecture should select this when it can successfully
 234           build and run with CONFIG_FORTIFY_SOURCE.
 235
 236 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 237 config ARCH_HAS_SET_MEMORY
 238         bool
 239
 240 # Select if arch init_task must go in the __init_task_data section
 241 config ARCH_TASK_STRUCT_ON_STACK
 242        bool
 243
 244 # Select if arch has its private alloc_task_struct() function
 245 config ARCH_TASK_STRUCT_ALLOCATOR
 246         bool
 247
 248 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 249         bool
 250         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 251         help
 252           An architecture should select this to provide hardened usercopy
 253           knowledge about what region of the thread_struct should be
 254           whitelisted for copying to userspace. Normally this is only the
 255           FPU registers. Specifically, arch_thread_struct_whitelist()
 256           should be implemented. Without this, the entire thread_struct
 257           field in task_struct will be left whitelisted.
 258
 259 # Select if arch has its private alloc_thread_stack() function
 260 config ARCH_THREAD_STACK_ALLOCATOR
 261         bool
 262
 263 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 264 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 265         bool
 266
 267 config HAVE_REGS_AND_STACK_ACCESS_API
 268         bool
 269         help
 270           This symbol should be selected by an architecure if it supports
 271           the API needed to access registers and stack entries from pt_regs,
 272           declared in asm/ptrace.h
 273           For example the kprobes-based event tracer needs this API.
 274
 275 config HAVE_CLK
 276         bool
 277         help
 278           The <linux/clk.h> calls support software clock gating and
 279           thus are a key power management tool on many systems.
 280
 281 config HAVE_DMA_API_DEBUG
 282         bool
 283
 284 config HAVE_HW_BREAKPOINT
 285         bool
 286         depends on PERF_EVENTS
 287
 288 config HAVE_MIXED_BREAKPOINTS_REGS
 289         bool
 290         depends on HAVE_HW_BREAKPOINT
 291         help
 292           Depending on the arch implementation of hardware breakpoints,
 293           some of them have separate registers for data and instruction
 294           breakpoints addresses, others have mixed registers to store
 295           them but define the access type in a control register.
 296           Select this option if your arch implements breakpoints under the
 297           latter fashion.
 298
 299 config HAVE_USER_RETURN_NOTIFIER
 300         bool
 301
 302 config HAVE_PERF_EVENTS_NMI
 303         bool
 304         help
 305           System hardware can generate an NMI using the perf event
 306           subsystem.  Also has support for calculating CPU cycle events
 307           to determine how many clock cycles in a given period.
 308
 309 config HAVE_HARDLOCKUP_DETECTOR_PERF
 310         bool
 311         depends on HAVE_PERF_EVENTS_NMI
 312         help
 313           The arch chooses to use the generic perf-NMI-based hardlockup
 314           detector. Must define HAVE_PERF_EVENTS_NMI.
 315
 316 config HAVE_NMI_WATCHDOG
 317         depends on HAVE_NMI
 318         bool
 319         help
 320           The arch provides a low level NMI watchdog. It provides
 321           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 322
 323 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 324         bool
 325         select HAVE_NMI_WATCHDOG
 326         help
 327           The arch chooses to provide its own hardlockup detector, which is
 328           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 329           interfaces and parameters provided by hardlockup detector subsystem.
 330
 331 config HAVE_PERF_REGS
 332         bool
 333         help
 334           Support selective register dumps for perf events. This includes
 335           bit-mapping of each registers and a unique architecture id.
 336
 337 config HAVE_PERF_USER_STACK_DUMP
 338         bool
 339         help
 340           Support user stack dumps for perf event samples. This needs
 341           access to the user stack pointer which is not unified across
 342           architectures.
 343
 344 config HAVE_ARCH_JUMP_LABEL
 345         bool
 346
 347 config HAVE_RCU_TABLE_FREE
 348         bool
 349
 350 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 351         bool
 352
 353 config HAVE_ALIGNED_STRUCT_PAGE
 354         bool
 355         help
 356           This makes sure that struct pages are double word aligned and that
 357           e.g. the SLUB allocator can perform double word atomic operations
 358           on a struct page for better performance. However selecting this
 359           might increase the size of a struct page by a word.
 360
 361 config HAVE_CMPXCHG_LOCAL
 362         bool
 363
 364 config HAVE_CMPXCHG_DOUBLE
 365         bool
 366
 367 config ARCH_WEAK_RELEASE_ACQUIRE
 368         bool
 369
 370 config ARCH_WANT_IPC_PARSE_VERSION
 371         bool
 372
 373 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 374         bool
 375
 376 config ARCH_WANT_OLD_COMPAT_IPC
 377         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 378         bool
 379
 380 config HAVE_ARCH_SECCOMP_FILTER
 381         bool
 382         help
 383           An arch should select this symbol if it provides all of these things:
 384           - syscall_get_arch()
 385           - syscall_get_arguments()
 386           - syscall_rollback()
 387           - syscall_set_return_value()
 388           - SIGSYS siginfo_t support
 389           - secure_computing is called from a ptrace_event()-safe context
 390           - secure_computing return value is checked and a return value of -1
 391             results in the system call being skipped immediately.
 392           - seccomp syscall wired up
 393
 394 config SECCOMP_FILTER
 395         def_bool y
 396         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 397         help
 398           Enable tasks to build secure computing environments defined
 399           in terms of Berkeley Packet Filter programs which implement
 400           task-defined system call filtering polices.
 401
 402           See Documentation/prctl/seccomp_filter.txt for details.
 403
 404 config HAVE_GCC_PLUGINS
 405         bool
 406         help
 407           An arch should select this symbol if it supports building with
 408           GCC plugins.
 409
 410 menuconfig GCC_PLUGINS
 411         bool "GCC plugins"
 412         depends on HAVE_GCC_PLUGINS
 413         depends on !COMPILE_TEST
 414         help
 415           GCC plugins are loadable modules that provide extra features to the
 416           compiler. They are useful for runtime instrumentation and static analysis.
 417
 418           See Documentation/gcc-plugins.txt for details.
 419
 420 config GCC_PLUGIN_CYC_COMPLEXITY
 421         bool "Compute the cyclomatic complexity of a function" if EXPERT
 422         depends on GCC_PLUGINS
 423         depends on !COMPILE_TEST
 424         help
 425           The complexity M of a function's control flow graph is defined as:
 426            M = E - N + 2P
 427           where
 428
 429           E = the number of edges
 430           N = the number of nodes
 431           P = the number of connected components (exit nodes).
 432
 433           Enabling this plugin reports the complexity to stderr during the
 434           build. It mainly serves as a simple example of how to create a
 435           gcc plugin for the kernel.
 436
 437 config GCC_PLUGIN_SANCOV
 438         bool
 439         depends on GCC_PLUGINS
 440         help
 441           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 442           basic blocks. It supports all gcc versions with plugin support (from
 443           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 444           by Dmitry Vyukov <dvyukov@google.com>.
 445
 446 config GCC_PLUGIN_LATENT_ENTROPY
 447         bool "Generate some entropy during boot and runtime"
 448         depends on GCC_PLUGINS
 449         help
 450           By saying Y here the kernel will instrument some kernel code to
 451           extract some entropy from both original and artificially created
 452           program state.  This will help especially embedded systems where
 453           there is little 'natural' source of entropy normally.  The cost
 454           is some slowdown of the boot process (about 0.5%) and fork and
 455           irq processing.
 456
 457           Note that entropy extracted this way is not cryptographically
 458           secure!
 459
 460           This plugin was ported from grsecurity/PaX. More information at:
 461            * https://grsecurity.net/
 462            * https://pax.grsecurity.net/
 463
 464 config GCC_PLUGIN_STRUCTLEAK
 465         bool "Force initialization of variables containing userspace addresses"
 466         depends on GCC_PLUGINS
 467         help
 468           This plugin zero-initializes any structures containing a
 469           __user attribute. This can prevent some classes of information
 470           exposures.
 471
 472           This plugin was ported from grsecurity/PaX. More information at:
 473            * https://grsecurity.net/
 474            * https://pax.grsecurity.net/
 475
 476 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
 477         bool "Force initialize all struct type variables passed by reference"
 478         depends on GCC_PLUGIN_STRUCTLEAK
 479         help
 480           Zero initialize any struct type local variable that may be passed by
 481           reference without having been initialized.
 482
 483 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 484         bool "Report forcefully initialized variables"
 485         depends on GCC_PLUGIN_STRUCTLEAK
 486         depends on !COMPILE_TEST
 487         help
 488           This option will cause a warning to be printed each time the
 489           structleak plugin finds a variable it thinks needs to be
 490           initialized. Since not all existing initializers are detected
 491           by the plugin, this can produce false positive warnings.
 492
 493 config GCC_PLUGIN_RANDSTRUCT
 494         bool "Randomize layout of sensitive kernel structures"
 495         depends on GCC_PLUGINS
 496         select MODVERSIONS if MODULES
 497         help
 498           If you say Y here, the layouts of structures that are entirely
 499           function pointers (and have not been manually annotated with
 500           __no_randomize_layout), or structures that have been explicitly
 501           marked with __randomize_layout, will be randomized at compile-time.
 502           This can introduce the requirement of an additional information
 503           exposure vulnerability for exploits targeting these structure
 504           types.
 505
 506           Enabling this feature will introduce some performance impact,
 507           slightly increase memory usage, and prevent the use of forensic
 508           tools like Volatility against the system (unless the kernel
 509           source tree isn't cleaned after kernel installation).
 510
 511           The seed used for compilation is located at
 512           scripts/gcc-plgins/randomize_layout_seed.h.  It remains after
 513           a make clean to allow for external modules to be compiled with
 514           the existing seed and will be removed by a make mrproper or
 515           make distclean.
 516
 517           Note that the implementation requires gcc 4.7 or newer.
 518
 519           This plugin was ported from grsecurity/PaX. More information at:
 520            * https://grsecurity.net/
 521            * https://pax.grsecurity.net/
 522
 523 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
 524         bool "Use cacheline-aware structure randomization"
 525         depends on GCC_PLUGIN_RANDSTRUCT
 526         depends on !COMPILE_TEST
 527         help
 528           If you say Y here, the RANDSTRUCT randomization will make a
 529           best effort at restricting randomization to cacheline-sized
 530           groups of elements.  It will further not randomize bitfields
 531           in structures.  This reduces the performance hit of RANDSTRUCT
 532           at the cost of weakened randomization.
 533
 534 config HAVE_CC_STACKPROTECTOR
 535         bool
 536         help
 537           An arch should select this symbol if:
 538           - its compiler supports the -fstack-protector option
 539           - it has implemented a stack canary (e.g. __stack_chk_guard)
 540
 541 choice
 542         prompt "Stack Protector buffer overflow detection"
 543         depends on HAVE_CC_STACKPROTECTOR
 544         default CC_STACKPROTECTOR_AUTO
 545         help
 546           This option turns on the "stack-protector" GCC feature. This
 547           feature puts, at the beginning of functions, a canary value on
 548           the stack just before the return address, and validates
 549           the value just before actually returning.  Stack based buffer
 550           overflows (that need to overwrite this return address) now also
 551           overwrite the canary, which gets detected and the attack is then
 552           neutralized via a kernel panic.
 553
 554 config CC_STACKPROTECTOR_NONE
 555         bool "None"
 556         help
 557           Disable "stack-protector" GCC feature.
 558
 559 config CC_STACKPROTECTOR_REGULAR
 560         bool "Regular"
 561         help
 562           Functions will have the stack-protector canary logic added if they
 563           have an 8-byte or larger character array on the stack.
 564
 565           This feature requires gcc version 4.2 or above, or a distribution
 566           gcc with the feature backported ("-fstack-protector").
 567
 568           On an x86 "defconfig" build, this feature adds canary checks to
 569           about 3% of all kernel functions, which increases kernel code size
 570           by about 0.3%.
 571
 572 config CC_STACKPROTECTOR_STRONG
 573         bool "Strong"
 574         help
 575           Functions will have the stack-protector canary logic added in any
 576           of the following conditions:
 577
 578           - local variable's address used as part of the right hand side of an
 579             assignment or function argument
 580           - local variable is an array (or union containing an array),
 581             regardless of array type or length
 582           - uses register local variables
 583
 584           This feature requires gcc version 4.9 or above, or a distribution
 585           gcc with the feature backported ("-fstack-protector-strong").
 586
 587           On an x86 "defconfig" build, this feature adds canary checks to
 588           about 20% of all kernel functions, which increases the kernel code
 589           size by about 2%.
 590
 591 config CC_STACKPROTECTOR_AUTO
 592         bool "Automatic"
 593         help
 594           If the compiler supports it, the best available stack-protector
 595           option will be chosen.
 596
 597 endchoice
 598
 599 config LD_DEAD_CODE_DATA_ELIMINATION
 600         bool
 601         help
 602           Select this if the architecture wants to do dead code and
 603           data elimination with the linker by compiling with
 604           -ffunction-sections -fdata-sections and linking with
 605           --gc-sections.
 606
 607           This requires that the arch annotates or otherwise protects
 608           its external entry points from being discarded. Linker scripts
 609           must also merge .text.*, .data.*, and .bss.* correctly into
 610           output sections. Care must be taken not to pull in unrelated
 611           sections (e.g., '.text.init'). Typically '.' in section names
 612           is used to distinguish them from label names / C identifiers.
 613
 614 config HAVE_ARCH_WITHIN_STACK_FRAMES
 615         bool
 616         help
 617           An architecture should select this if it can walk the kernel stack
 618           frames to determine if an object is part of either the arguments
 619           or local variables (i.e. that it excludes saved return addresses,
 620           and similar) by implementing an inline arch_within_stack_frames(),
 621           which is used by CONFIG_HARDENED_USERCOPY.
 622
 623 config HAVE_CONTEXT_TRACKING
 624         bool
 625         help
 626           Provide kernel/user boundaries probes necessary for subsystems
 627           that need it, such as userspace RCU extended quiescent state.
 628           Syscalls need to be wrapped inside user_exit()-user_enter() through
 629           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 630           wrapped as well. Irqs are already protected inside
 631           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 632           irq exit still need to be protected.
 633
 634 config HAVE_VIRT_CPU_ACCOUNTING
 635         bool
 636
 637 config ARCH_HAS_SCALED_CPUTIME
 638         bool
 639
 640 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 641         bool
 642         default y if 64BIT
 643         help
 644           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 645           Before enabling this option, arch code must be audited
 646           to ensure there are no races in concurrent read/write of
 647           cputime_t. For example, reading/writing 64-bit cputime_t on
 648           some 32-bit arches may require multiple accesses, so proper
 649           locking is needed to protect against concurrent accesses.
 650
 651
 652 config HAVE_IRQ_TIME_ACCOUNTING
 653         bool
 654         help
 655           Archs need to ensure they use a high enough resolution clock to
 656           support irq time accounting and then call enable_sched_clock_irqtime().
 657
 658 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 659         bool
 660
 661 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 662         bool
 663
 664 config HAVE_ARCH_HUGE_VMAP
 665         bool
 666
 667 config HAVE_ARCH_SOFT_DIRTY
 668         bool
 669
 670 config HAVE_MOD_ARCH_SPECIFIC
 671         bool
 672         help
 673           The arch uses struct mod_arch_specific to store data.  Many arches
 674           just need a simple module loader without arch specific data - those
 675           should not enable this.
 676
 677 config MODULES_USE_ELF_RELA
 678         bool
 679         help
 680           Modules only use ELF RELA relocations.  Modules with ELF REL
 681           relocations will give an error.
 682
 683 config MODULES_USE_ELF_REL
 684         bool
 685         help
 686           Modules only use ELF REL relocations.  Modules with ELF RELA
 687           relocations will give an error.
 688
 689 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 690         bool
 691         help
 692           Some architectures generate an _ in front of C symbols; things like
 693           module loading and assembly files need to know about this.
 694
 695 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 696         bool
 697         help
 698           Architecture doesn't only execute the irq handler on the irq stack
 699           but also irq_exit(). This way we can process softirqs on this irq
 700           stack instead of switching to a new one when we call __do_softirq()
 701           in the end of an hardirq.
 702           This spares a stack switch and improves cache usage on softirq
 703           processing.
 704
 705 config PGTABLE_LEVELS
 706         int
 707         default 2
 708
 709 config ARCH_HAS_ELF_RANDOMIZE
 710         bool
 711         help
 712           An architecture supports choosing randomized locations for
 713           stack, mmap, brk, and ET_DYN. Defined functions:
 714           - arch_mmap_rnd()
 715           - arch_randomize_brk()
 716
 717 config HAVE_ARCH_MMAP_RND_BITS
 718         bool
 719         help
 720           An arch should select this symbol if it supports setting a variable
 721           number of bits for use in establishing the base address for mmap
 722           allocations, has MMU enabled and provides values for both:
 723           - ARCH_MMAP_RND_BITS_MIN
 724           - ARCH_MMAP_RND_BITS_MAX
 725
 726 config HAVE_EXIT_THREAD
 727         bool
 728         help
 729           An architecture implements exit_thread.
 730
 731 config ARCH_MMAP_RND_BITS_MIN
 732         int
 733
 734 config ARCH_MMAP_RND_BITS_MAX
 735         int
 736
 737 config ARCH_MMAP_RND_BITS_DEFAULT
 738         int
 739
 740 config ARCH_MMAP_RND_BITS
 741         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 742         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 743         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 744         default ARCH_MMAP_RND_BITS_MIN
 745         depends on HAVE_ARCH_MMAP_RND_BITS
 746         help
 747           This value can be used to select the number of bits to use to
 748           determine the random offset to the base address of vma regions
 749           resulting from mmap allocations. This value will be bounded
 750           by the architecture's minimum and maximum supported values.
 751
 752           This value can be changed after boot using the
 753           /proc/sys/vm/mmap_rnd_bits tunable
 754
 755 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 756         bool
 757         help
 758           An arch should select this symbol if it supports running applications
 759           in compatibility mode, supports setting a variable number of bits for
 760           use in establishing the base address for mmap allocations, has MMU
 761           enabled and provides values for both:
 762           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 763           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 764
 765 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 766         int
 767
 768 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 769         int
 770
 771 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 772         int
 773
 774 config ARCH_MMAP_RND_COMPAT_BITS
 775         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 776         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 777         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 778         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 779         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 780         help
 781           This value can be used to select the number of bits to use to
 782           determine the random offset to the base address of vma regions
 783           resulting from mmap allocations for compatible applications This
 784           value will be bounded by the architecture's minimum and maximum
 785           supported values.
 786
 787           This value can be changed after boot using the
 788           /proc/sys/vm/mmap_rnd_compat_bits tunable
 789
 790 config HAVE_ARCH_COMPAT_MMAP_BASES
 791         bool
 792         help
 793           This allows 64bit applications to invoke 32-bit mmap() syscall
 794           and vice-versa 32-bit applications to call 64-bit mmap().
 795           Required for applications doing different bitness syscalls.
 796
 797 config HAVE_COPY_THREAD_TLS
 798         bool
 799         help
 800           Architecture provides copy_thread_tls to accept tls argument via
 801           normal C parameter passing, rather than extracting the syscall
 802           argument from pt_regs.
 803
 804 config HAVE_STACK_VALIDATION
 805         bool
 806         help
 807           Architecture supports the 'objtool check' host tool command, which
 808           performs compile-time stack metadata validation.
 809
 810 config HAVE_RELIABLE_STACKTRACE
 811         bool
 812         help
 813           Architecture has a save_stack_trace_tsk_reliable() function which
 814           only returns a stack trace if it can guarantee the trace is reliable.
 815
 816 config HAVE_ARCH_HASH
 817         bool
 818         default n
 819         help
 820           If this is set, the architecture provides an <asm/hash.h>
 821           file which provides platform-specific implementations of some
 822           functions in <linux/hash.h> or fs/namei.c.
 823
 824 config ISA_BUS_API
 825         def_bool ISA
 826
 827 #
 828 # ABI hall of shame
 829 #
 830 config CLONE_BACKWARDS
 831         bool
 832         help
 833           Architecture has tls passed as the 4th argument of clone(2),
 834           not the 5th one.
 835
 836 config CLONE_BACKWARDS2
 837         bool
 838         help
 839           Architecture has the first two arguments of clone(2) swapped.
 840
 841 config CLONE_BACKWARDS3
 842         bool
 843         help
 844           Architecture has tls passed as the 3rd argument of clone(2),
 845           not the 5th one.
 846
 847 config ODD_RT_SIGACTION
 848         bool
 849         help
 850           Architecture has unusual rt_sigaction(2) arguments
 851
 852 config OLD_SIGSUSPEND
 853         bool
 854         help
 855           Architecture has old sigsuspend(2) syscall, of one-argument variety
 856
 857 config OLD_SIGSUSPEND3
 858         bool
 859         help
 860           Even weirder antique ABI - three-argument sigsuspend(2)
 861
 862 config OLD_SIGACTION
 863         bool
 864         help
 865           Architecture has old sigaction(2) syscall.  Nope, not the same
 866           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 867           but fairly different variant of sigaction(2), thanks to OSF/1
 868           compatibility...
 869
 870 config COMPAT_OLD_SIGACTION
 871         bool
 872
 873 config ARCH_NO_COHERENT_DMA_MMAP
 874         bool
 875
 876 config CPU_NO_EFFICIENT_FFS
 877         def_bool n
 878
 879 config HAVE_ARCH_VMAP_STACK
 880         def_bool n
 881         help
 882           An arch should select this symbol if it can support kernel stacks
 883           in vmalloc space.  This means:
 884
 885           - vmalloc space must be large enough to hold many kernel stacks.
 886             This may rule out many 32-bit architectures.
 887
 888           - Stacks in vmalloc space need to work reliably.  For example, if
 889             vmap page tables are created on demand, either this mechanism
 890             needs to work while the stack points to a virtual address with
 891             unpopulated page tables or arch code (switch_to() and switch_mm(),
 892             most likely) needs to ensure that the stack's page table entries
 893             are populated before running on a possibly unpopulated stack.
 894
 895           - If the stack overflows into a guard page, something reasonable
 896             should happen.  The definition of "reasonable" is flexible, but
 897             instantly rebooting without logging anything would be unfriendly.
 898
 899 config VMAP_STACK
 900         default y
 901         bool "Use a virtually-mapped stack"
 902         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 903         ---help---
 904           Enable this if you want the use virtually-mapped kernel stacks
 905           with guard pages.  This causes kernel stack overflows to be
 906           caught immediately rather than causing difficult-to-diagnose
 907           corruption.
 908
 909           This is presently incompatible with KASAN because KASAN expects
 910           the stack to map directly to the KASAN shadow map using a formula
 911           that is incorrect if the stack is in vmalloc space.
 912
 913 config ARCH_OPTIONAL_KERNEL_RWX
 914         def_bool n
 915
 916 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 917         def_bool n
 918
 919 config ARCH_HAS_STRICT_KERNEL_RWX
 920         def_bool n
 921
 922 config STRICT_KERNEL_RWX
 923         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 924         depends on ARCH_HAS_STRICT_KERNEL_RWX
 925         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 926         help
 927           If this is set, kernel text and rodata memory will be made read-only,
 928           and non-text memory will be made non-executable. This provides
 929           protection against certain security exploits (e.g. executing the heap
 930           or modifying text)
 931
 932           These features are considered standard security practice these days.
 933           You should say Y here in almost all cases.
 934
 935 config ARCH_HAS_STRICT_MODULE_RWX
 936         def_bool n
 937
 938 config STRICT_MODULE_RWX
 939         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 940         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 941         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 942         help
 943           If this is set, module text and rodata memory will be made read-only,
 944           and non-text memory will be made non-executable. This provides
 945           protection against certain security exploits (e.g. writing to text)
 946
 947 # select if the architecture provides an asm/dma-direct.h header
 948 config ARCH_HAS_PHYS_TO_DMA
 949         bool
 950
 951 config ARCH_HAS_REFCOUNT
 952         bool
 953         help
 954           An architecture selects this when it has implemented refcount_t
 955           using open coded assembly primitives that provide an optimized
 956           refcount_t implementation, possibly at the expense of some full
 957           refcount state checks of CONFIG_REFCOUNT_FULL=y.
 958
 959           The refcount overflow check behavior, however, must be retained.
 960           Catching overflows is the primary security concern for protecting
 961           against bugs in reference counts.
 962
 963 config REFCOUNT_FULL
 964         bool "Perform full reference count validation at the expense of speed"
 965         help
 966           Enabling this switches the refcounting infrastructure from a fast
 967           unchecked atomic_t implementation to a fully state checked
 968           implementation, which can be (slightly) slower but provides protections
 969           against various use-after-free conditions that can be used in
 970           security flaw exploits.
 971
 972 source "kernel/gcov/Kconfig"