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 HOTPLUG_SMT
  17         bool
  18
  19 config OPROFILE
  20         tristate "OProfile system profiling"
  21         depends on PROFILING
  22         depends on HAVE_OPROFILE
  23         select RING_BUFFER
  24         select RING_BUFFER_ALLOW_SWAP
  25         help
  26           OProfile is a profiling system capable of profiling the
  27           whole system, include the kernel, kernel modules, libraries,
  28           and applications.
  29
  30           If unsure, say N.
  31
  32 config OPROFILE_EVENT_MULTIPLEX
  33         bool "OProfile multiplexing support (EXPERIMENTAL)"
  34         default n
  35         depends on OPROFILE && X86
  36         help
  37           The number of hardware counters is limited. The multiplexing
  38           feature enables OProfile to gather more events than counters
  39           are provided by the hardware. This is realized by switching
  40           between events at a user specified time interval.
  41
  42           If unsure, say N.
  43
  44 config HAVE_OPROFILE
  45         bool
  46
  47 config OPROFILE_NMI_TIMER
  48         def_bool y
  49         depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
  50
  51 config KPROBES
  52         bool "Kprobes"
  53         depends on MODULES
  54         depends on HAVE_KPROBES
  55         select KALLSYMS
  56         help
  57           Kprobes allows you to trap at almost any kernel address and
  58           execute a callback function.  register_kprobe() establishes
  59           a probepoint and specifies the callback.  Kprobes is useful
  60           for kernel debugging, non-intrusive instrumentation and testing.
  61           If in doubt, say "N".
  62
  63 config JUMP_LABEL
  64        bool "Optimize very unlikely/likely branches"
  65        depends on HAVE_ARCH_JUMP_LABEL
  66        help
  67          This option enables a transparent branch optimization that
  68          makes certain almost-always-true or almost-always-false branch
  69          conditions even cheaper to execute within the kernel.
  70
  71          Certain performance-sensitive kernel code, such as trace points,
  72          scheduler functionality, networking code and KVM have such
  73          branches and include support for this optimization technique.
  74
  75          If it is detected that the compiler has support for "asm goto",
  76          the kernel will compile such branches with just a nop
  77          instruction. When the condition flag is toggled to true, the
  78          nop will be converted to a jump instruction to execute the
  79          conditional block of instructions.
  80
  81          This technique lowers overhead and stress on the branch prediction
  82          of the processor and generally makes the kernel faster. The update
  83          of the condition is slower, but those are always very rare.
  84
  85          ( On 32-bit x86, the necessary options added to the compiler
  86            flags may increase the size of the kernel slightly. )
  87
  88 config STATIC_KEYS_SELFTEST
  89         bool "Static key selftest"
  90         depends on JUMP_LABEL
  91         help
  92           Boot time self-test of the branch patching code.
  93
  94 config OPTPROBES
  95         def_bool y
  96         depends on KPROBES && HAVE_OPTPROBES
  97         select TASKS_RCU if PREEMPT
  98
  99 config KPROBES_ON_FTRACE
 100         def_bool y
 101         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
 102         depends on DYNAMIC_FTRACE_WITH_REGS
 103         help
 104          If function tracer is enabled and the arch supports full
 105          passing of pt_regs to function tracing, then kprobes can
 106          optimize on top of function tracing.
 107
 108 config UPROBES
 109         def_bool n
 110         depends on ARCH_SUPPORTS_UPROBES
 111         help
 112           Uprobes is the user-space counterpart to kprobes: they
 113           enable instrumentation applications (such as 'perf probe')
 114           to establish unintrusive probes in user-space binaries and
 115           libraries, by executing handler functions when the probes
 116           are hit by user-space applications.
 117
 118           ( These probes come in the form of single-byte breakpoints,
 119             managed by the kernel and kept transparent to the probed
 120             application. )
 121
 122 config HAVE_64BIT_ALIGNED_ACCESS
 123         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 124         help
 125           Some architectures require 64 bit accesses to be 64 bit
 126           aligned, which also requires structs containing 64 bit values
 127           to be 64 bit aligned too. This includes some 32 bit
 128           architectures which can do 64 bit accesses, as well as 64 bit
 129           architectures without unaligned access.
 130
 131           This symbol should be selected by an architecture if 64 bit
 132           accesses are required to be 64 bit aligned in this way even
 133           though it is not a 64 bit architecture.
 134
 135           See Documentation/unaligned-memory-access.txt for more
 136           information on the topic of unaligned memory accesses.
 137
 138 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 139         bool
 140         help
 141           Some architectures are unable to perform unaligned accesses
 142           without the use of get_unaligned/put_unaligned. Others are
 143           unable to perform such accesses efficiently (e.g. trap on
 144           unaligned access and require fixing it up in the exception
 145           handler.)
 146
 147           This symbol should be selected by an architecture if it can
 148           perform unaligned accesses efficiently to allow different
 149           code paths to be selected for these cases. Some network
 150           drivers, for example, could opt to not fix up alignment
 151           problems with received packets if doing so would not help
 152           much.
 153
 154           See Documentation/unaligned-memory-access.txt for more
 155           information on the topic of unaligned memory accesses.
 156
 157 config ARCH_USE_BUILTIN_BSWAP
 158        bool
 159        help
 160          Modern versions of GCC (since 4.4) have builtin functions
 161          for handling byte-swapping. Using these, instead of the old
 162          inline assembler that the architecture code provides in the
 163          __arch_bswapXX() macros, allows the compiler to see what's
 164          happening and offers more opportunity for optimisation. In
 165          particular, the compiler will be able to combine the byteswap
 166          with a nearby load or store and use load-and-swap or
 167          store-and-swap instructions if the architecture has them. It
 168          should almost *never* result in code which is worse than the
 169          hand-coded assembler in <asm/swab.h>.  But just in case it
 170          does, the use of the builtins is optional.
 171
 172          Any architecture with load-and-swap or store-and-swap
 173          instructions should set this. And it shouldn't hurt to set it
 174          on architectures that don't have such instructions.
 175
 176 config KRETPROBES
 177         def_bool y
 178         depends on KPROBES && HAVE_KRETPROBES
 179
 180 config USER_RETURN_NOTIFIER
 181         bool
 182         depends on HAVE_USER_RETURN_NOTIFIER
 183         help
 184           Provide a kernel-internal notification when a cpu is about to
 185           switch to user mode.
 186
 187 config HAVE_IOREMAP_PROT
 188         bool
 189
 190 config HAVE_KPROBES
 191         bool
 192
 193 config HAVE_KRETPROBES
 194         bool
 195
 196 config HAVE_OPTPROBES
 197         bool
 198
 199 config HAVE_KPROBES_ON_FTRACE
 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 initializer is different to init/init_task.c
 241 config ARCH_INIT_TASK
 242        bool
 243
 244 # Select if arch has its private alloc_task_struct() function
 245 config ARCH_TASK_STRUCT_ALLOCATOR
 246         bool
 247
 248 # Select if arch has its private alloc_thread_stack() function
 249 config ARCH_THREAD_STACK_ALLOCATOR
 250         bool
 251
 252 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 253 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 254         bool
 255
 256 config HAVE_REGS_AND_STACK_ACCESS_API
 257         bool
 258         help
 259           This symbol should be selected by an architecure if it supports
 260           the API needed to access registers and stack entries from pt_regs,
 261           declared in asm/ptrace.h
 262           For example the kprobes-based event tracer needs this API.
 263
 264 config HAVE_CLK
 265         bool
 266         help
 267           The <linux/clk.h> calls support software clock gating and
 268           thus are a key power management tool on many systems.
 269
 270 config HAVE_DMA_API_DEBUG
 271         bool
 272
 273 config HAVE_HW_BREAKPOINT
 274         bool
 275         depends on PERF_EVENTS
 276
 277 config HAVE_MIXED_BREAKPOINTS_REGS
 278         bool
 279         depends on HAVE_HW_BREAKPOINT
 280         help
 281           Depending on the arch implementation of hardware breakpoints,
 282           some of them have separate registers for data and instruction
 283           breakpoints addresses, others have mixed registers to store
 284           them but define the access type in a control register.
 285           Select this option if your arch implements breakpoints under the
 286           latter fashion.
 287
 288 config HAVE_USER_RETURN_NOTIFIER
 289         bool
 290
 291 config HAVE_PERF_EVENTS_NMI
 292         bool
 293         help
 294           System hardware can generate an NMI using the perf event
 295           subsystem.  Also has support for calculating CPU cycle events
 296           to determine how many clock cycles in a given period.
 297
 298 config HAVE_HARDLOCKUP_DETECTOR_PERF
 299         bool
 300         depends on HAVE_PERF_EVENTS_NMI
 301         help
 302           The arch chooses to use the generic perf-NMI-based hardlockup
 303           detector. Must define HAVE_PERF_EVENTS_NMI.
 304
 305 config HAVE_NMI_WATCHDOG
 306         depends on HAVE_NMI
 307         bool
 308         help
 309           The arch provides a low level NMI watchdog. It provides
 310           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 311
 312 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 313         bool
 314         select HAVE_NMI_WATCHDOG
 315         help
 316           The arch chooses to provide its own hardlockup detector, which is
 317           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 318           interfaces and parameters provided by hardlockup detector subsystem.
 319
 320 config HAVE_PERF_REGS
 321         bool
 322         help
 323           Support selective register dumps for perf events. This includes
 324           bit-mapping of each registers and a unique architecture id.
 325
 326 config HAVE_PERF_USER_STACK_DUMP
 327         bool
 328         help
 329           Support user stack dumps for perf event samples. This needs
 330           access to the user stack pointer which is not unified across
 331           architectures.
 332
 333 config HAVE_ARCH_JUMP_LABEL
 334         bool
 335
 336 config HAVE_RCU_TABLE_FREE
 337         bool
 338
 339 config HAVE_RCU_TABLE_INVALIDATE
 340         bool
 341
 342 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 343         bool
 344
 345 config HAVE_ALIGNED_STRUCT_PAGE
 346         bool
 347         help
 348           This makes sure that struct pages are double word aligned and that
 349           e.g. the SLUB allocator can perform double word atomic operations
 350           on a struct page for better performance. However selecting this
 351           might increase the size of a struct page by a word.
 352
 353 config HAVE_CMPXCHG_LOCAL
 354         bool
 355
 356 config HAVE_CMPXCHG_DOUBLE
 357         bool
 358
 359 config ARCH_WEAK_RELEASE_ACQUIRE
 360         bool
 361
 362 config ARCH_WANT_IPC_PARSE_VERSION
 363         bool
 364
 365 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 366         bool
 367
 368 config ARCH_WANT_OLD_COMPAT_IPC
 369         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 370         bool
 371
 372 config HAVE_ARCH_SECCOMP_FILTER
 373         bool
 374         help
 375           An arch should select this symbol if it provides all of these things:
 376           - syscall_get_arch()
 377           - syscall_get_arguments()
 378           - syscall_rollback()
 379           - syscall_set_return_value()
 380           - SIGSYS siginfo_t support
 381           - secure_computing is called from a ptrace_event()-safe context
 382           - secure_computing return value is checked and a return value of -1
 383             results in the system call being skipped immediately.
 384           - seccomp syscall wired up
 385
 386 config SECCOMP_FILTER
 387         def_bool y
 388         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 389         help
 390           Enable tasks to build secure computing environments defined
 391           in terms of Berkeley Packet Filter programs which implement
 392           task-defined system call filtering polices.
 393
 394           See Documentation/prctl/seccomp_filter.txt for details.
 395
 396 config HAVE_GCC_PLUGINS
 397         bool
 398         help
 399           An arch should select this symbol if it supports building with
 400           GCC plugins.
 401
 402 menuconfig GCC_PLUGINS
 403         bool "GCC plugins"
 404         depends on HAVE_GCC_PLUGINS
 405         depends on !COMPILE_TEST
 406         help
 407           GCC plugins are loadable modules that provide extra features to the
 408           compiler. They are useful for runtime instrumentation and static analysis.
 409
 410           See Documentation/gcc-plugins.txt for details.
 411
 412 config GCC_PLUGIN_CYC_COMPLEXITY
 413         bool "Compute the cyclomatic complexity of a function" if EXPERT
 414         depends on GCC_PLUGINS
 415         depends on !COMPILE_TEST
 416         help
 417           The complexity M of a function's control flow graph is defined as:
 418            M = E - N + 2P
 419           where
 420
 421           E = the number of edges
 422           N = the number of nodes
 423           P = the number of connected components (exit nodes).
 424
 425           Enabling this plugin reports the complexity to stderr during the
 426           build. It mainly serves as a simple example of how to create a
 427           gcc plugin for the kernel.
 428
 429 config GCC_PLUGIN_SANCOV
 430         bool
 431         depends on GCC_PLUGINS
 432         help
 433           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 434           basic blocks. It supports all gcc versions with plugin support (from
 435           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 436           by Dmitry Vyukov <dvyukov@google.com>.
 437
 438 config GCC_PLUGIN_LATENT_ENTROPY
 439         bool "Generate some entropy during boot and runtime"
 440         depends on GCC_PLUGINS
 441         help
 442           By saying Y here the kernel will instrument some kernel code to
 443           extract some entropy from both original and artificially created
 444           program state.  This will help especially embedded systems where
 445           there is little 'natural' source of entropy normally.  The cost
 446           is some slowdown of the boot process (about 0.5%) and fork and
 447           irq processing.
 448
 449           Note that entropy extracted this way is not cryptographically
 450           secure!
 451
 452           This plugin was ported from grsecurity/PaX. More information at:
 453            * https://grsecurity.net/
 454            * https://pax.grsecurity.net/
 455
 456 config GCC_PLUGIN_STRUCTLEAK
 457         bool "Force initialization of variables containing userspace addresses"
 458         depends on GCC_PLUGINS
 459         help
 460           This plugin zero-initializes any structures containing a
 461           __user attribute. This can prevent some classes of information
 462           exposures.
 463
 464           This plugin was ported from grsecurity/PaX. More information at:
 465            * https://grsecurity.net/
 466            * https://pax.grsecurity.net/
 467
 468 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
 469         bool "Force initialize all struct type variables passed by reference"
 470         depends on GCC_PLUGIN_STRUCTLEAK
 471         help
 472           Zero initialize any struct type local variable that may be passed by
 473           reference without having been initialized.
 474
 475 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 476         bool "Report forcefully initialized variables"
 477         depends on GCC_PLUGIN_STRUCTLEAK
 478         depends on !COMPILE_TEST
 479         help
 480           This option will cause a warning to be printed each time the
 481           structleak plugin finds a variable it thinks needs to be
 482           initialized. Since not all existing initializers are detected
 483           by the plugin, this can produce false positive warnings.
 484
 485 config GCC_PLUGIN_RANDSTRUCT
 486         bool "Randomize layout of sensitive kernel structures"
 487         depends on GCC_PLUGINS
 488         select MODVERSIONS if MODULES
 489         help
 490           If you say Y here, the layouts of structures that are entirely
 491           function pointers (and have not been manually annotated with
 492           __no_randomize_layout), or structures that have been explicitly
 493           marked with __randomize_layout, will be randomized at compile-time.
 494           This can introduce the requirement of an additional information
 495           exposure vulnerability for exploits targeting these structure
 496           types.
 497
 498           Enabling this feature will introduce some performance impact,
 499           slightly increase memory usage, and prevent the use of forensic
 500           tools like Volatility against the system (unless the kernel
 501           source tree isn't cleaned after kernel installation).
 502
 503           The seed used for compilation is located at
 504           scripts/gcc-plgins/randomize_layout_seed.h.  It remains after
 505           a make clean to allow for external modules to be compiled with
 506           the existing seed and will be removed by a make mrproper or
 507           make distclean.
 508
 509           Note that the implementation requires gcc 4.7 or newer.
 510
 511           This plugin was ported from grsecurity/PaX. More information at:
 512            * https://grsecurity.net/
 513            * https://pax.grsecurity.net/
 514
 515 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
 516         bool "Use cacheline-aware structure randomization"
 517         depends on GCC_PLUGIN_RANDSTRUCT
 518         depends on !COMPILE_TEST
 519         help
 520           If you say Y here, the RANDSTRUCT randomization will make a
 521           best effort at restricting randomization to cacheline-sized
 522           groups of elements.  It will further not randomize bitfields
 523           in structures.  This reduces the performance hit of RANDSTRUCT
 524           at the cost of weakened randomization.
 525
 526 config HAVE_CC_STACKPROTECTOR
 527         bool
 528         help
 529           An arch should select this symbol if:
 530           - its compiler supports the -fstack-protector option
 531           - it has implemented a stack canary (e.g. __stack_chk_guard)
 532
 533 config CC_STACKPROTECTOR
 534         def_bool n
 535         help
 536           Set when a stack-protector mode is enabled, so that the build
 537           can enable kernel-side support for the GCC feature.
 538
 539 choice
 540         prompt "Stack Protector buffer overflow detection"
 541         depends on HAVE_CC_STACKPROTECTOR
 542         default CC_STACKPROTECTOR_NONE
 543         help
 544           This option turns on the "stack-protector" GCC feature. This
 545           feature puts, at the beginning of functions, a canary value on
 546           the stack just before the return address, and validates
 547           the value just before actually returning.  Stack based buffer
 548           overflows (that need to overwrite this return address) now also
 549           overwrite the canary, which gets detected and the attack is then
 550           neutralized via a kernel panic.
 551
 552 config CC_STACKPROTECTOR_NONE
 553         bool "None"
 554         help
 555           Disable "stack-protector" GCC feature.
 556
 557 config CC_STACKPROTECTOR_REGULAR
 558         bool "Regular"
 559         select CC_STACKPROTECTOR
 560         help
 561           Functions will have the stack-protector canary logic added if they
 562           have an 8-byte or larger character array on the stack.
 563
 564           This feature requires gcc version 4.2 or above, or a distribution
 565           gcc with the feature backported ("-fstack-protector").
 566
 567           On an x86 "defconfig" build, this feature adds canary checks to
 568           about 3% of all kernel functions, which increases kernel code size
 569           by about 0.3%.
 570
 571 config CC_STACKPROTECTOR_STRONG
 572         bool "Strong"
 573         select CC_STACKPROTECTOR
 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 endchoice
 592
 593 config THIN_ARCHIVES
 594         def_bool y
 595         help
 596           Select this if the architecture wants to use thin archives
 597           instead of ld -r to create the built-in.o files.
 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 LTO
 615         def_bool n
 616
 617 config ARCH_SUPPORTS_LTO_CLANG
 618         bool
 619         help
 620           An architecture should select this option it supports:
 621           - compiling with clang,
 622           - compiling inline assembly with clang's integrated assembler,
 623           - and linking with either lld or GNU gold w/ LLVMgold.
 624
 625 choice
 626         prompt "Link-Time Optimization (LTO) (EXPERIMENTAL)"
 627         default LTO_NONE
 628         help
 629           This option turns on Link-Time Optimization (LTO).
 630
 631 config LTO_NONE
 632         bool "None"
 633
 634 config LTO_CLANG
 635         bool "Use clang Link Time Optimization (LTO) (EXPERIMENTAL)"
 636         depends on ARCH_SUPPORTS_LTO_CLANG
 637         depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT
 638         depends on !KASAN
 639         select LTO
 640         select THIN_ARCHIVES
 641         select LD_DEAD_CODE_DATA_ELIMINATION
 642         help
 643           This option enables clang's Link Time Optimization (LTO), which allows
 644           the compiler to optimize the kernel globally at link time. If you
 645           enable this option, the compiler generates LLVM IR instead of object
 646           files, and the actual compilation from IR occurs at the LTO link step,
 647           which may take several minutes.
 648
 649           If you select this option, you must compile the kernel with clang >=
 650           5.0 (make CC=clang) and GNU gold from binutils >= 2.27, and have the
 651           LLVMgold plug-in in LD_LIBRARY_PATH.
 652
 653 endchoice
 654
 655 config CFI
 656         bool
 657
 658 config CFI_PERMISSIVE
 659         bool "Use CFI in permissive mode"
 660         depends on CFI
 661         help
 662           When selected, Control Flow Integrity (CFI) violations result in a
 663           warning instead of a kernel panic. This option is useful for finding
 664           CFI violations in drivers during development.
 665
 666 config CFI_CLANG
 667         bool "Use clang Control Flow Integrity (CFI) (EXPERIMENTAL)"
 668         depends on LTO_CLANG
 669         depends on KALLSYMS
 670         select CFI
 671         help
 672           This option enables clang Control Flow Integrity (CFI), which adds
 673           runtime checking for indirect function calls.
 674
 675 config CFI_CLANG_SHADOW
 676         bool "Use CFI shadow to speed up cross-module checks"
 677         default y
 678         depends on CFI_CLANG
 679         help
 680           If you select this option, the kernel builds a fast look-up table of
 681           CFI check functions in loaded modules to reduce overhead.
 682
 683 config HAVE_ARCH_WITHIN_STACK_FRAMES
 684         bool
 685         help
 686           An architecture should select this if it can walk the kernel stack
 687           frames to determine if an object is part of either the arguments
 688           or local variables (i.e. that it excludes saved return addresses,
 689           and similar) by implementing an inline arch_within_stack_frames(),
 690           which is used by CONFIG_HARDENED_USERCOPY.
 691
 692 config HAVE_CONTEXT_TRACKING
 693         bool
 694         help
 695           Provide kernel/user boundaries probes necessary for subsystems
 696           that need it, such as userspace RCU extended quiescent state.
 697           Syscalls need to be wrapped inside user_exit()-user_enter() through
 698           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 699           wrapped as well. Irqs are already protected inside
 700           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 701           irq exit still need to be protected.
 702
 703 config HAVE_VIRT_CPU_ACCOUNTING
 704         bool
 705
 706 config ARCH_HAS_SCALED_CPUTIME
 707         bool
 708
 709 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 710         bool
 711         default y if 64BIT
 712         help
 713           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 714           Before enabling this option, arch code must be audited
 715           to ensure there are no races in concurrent read/write of
 716           cputime_t. For example, reading/writing 64-bit cputime_t on
 717           some 32-bit arches may require multiple accesses, so proper
 718           locking is needed to protect against concurrent accesses.
 719
 720
 721 config HAVE_IRQ_TIME_ACCOUNTING
 722         bool
 723         help
 724           Archs need to ensure they use a high enough resolution clock to
 725           support irq time accounting and then call enable_sched_clock_irqtime().
 726
 727 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 728         bool
 729
 730 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 731         bool
 732
 733 config HAVE_ARCH_HUGE_VMAP
 734         bool
 735
 736 config HAVE_ARCH_SOFT_DIRTY
 737         bool
 738
 739 config HAVE_MOD_ARCH_SPECIFIC
 740         bool
 741         help
 742           The arch uses struct mod_arch_specific to store data.  Many arches
 743           just need a simple module loader without arch specific data - those
 744           should not enable this.
 745
 746 config MODULES_USE_ELF_RELA
 747         bool
 748         help
 749           Modules only use ELF RELA relocations.  Modules with ELF REL
 750           relocations will give an error.
 751
 752 config MODULES_USE_ELF_REL
 753         bool
 754         help
 755           Modules only use ELF REL relocations.  Modules with ELF RELA
 756           relocations will give an error.
 757
 758 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 759         bool
 760         help
 761           Some architectures generate an _ in front of C symbols; things like
 762           module loading and assembly files need to know about this.
 763
 764 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 765         bool
 766         help
 767           Architecture doesn't only execute the irq handler on the irq stack
 768           but also irq_exit(). This way we can process softirqs on this irq
 769           stack instead of switching to a new one when we call __do_softirq()
 770           in the end of an hardirq.
 771           This spares a stack switch and improves cache usage on softirq
 772           processing.
 773
 774 config PGTABLE_LEVELS
 775         int
 776         default 2
 777
 778 config ARCH_HAS_ELF_RANDOMIZE
 779         bool
 780         help
 781           An architecture supports choosing randomized locations for
 782           stack, mmap, brk, and ET_DYN. Defined functions:
 783           - arch_mmap_rnd()
 784           - arch_randomize_brk()
 785
 786 config HAVE_ARCH_MMAP_RND_BITS
 787         bool
 788         help
 789           An arch should select this symbol if it supports setting a variable
 790           number of bits for use in establishing the base address for mmap
 791           allocations, has MMU enabled and provides values for both:
 792           - ARCH_MMAP_RND_BITS_MIN
 793           - ARCH_MMAP_RND_BITS_MAX
 794
 795 config HAVE_EXIT_THREAD
 796         bool
 797         help
 798           An architecture implements exit_thread.
 799
 800 config ARCH_MMAP_RND_BITS_MIN
 801         int
 802
 803 config ARCH_MMAP_RND_BITS_MAX
 804         int
 805
 806 config ARCH_MMAP_RND_BITS_DEFAULT
 807         int
 808
 809 config ARCH_MMAP_RND_BITS
 810         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 811         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 812         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 813         default ARCH_MMAP_RND_BITS_MIN
 814         depends on HAVE_ARCH_MMAP_RND_BITS
 815         help
 816           This value can be used to select the number of bits to use to
 817           determine the random offset to the base address of vma regions
 818           resulting from mmap allocations. This value will be bounded
 819           by the architecture's minimum and maximum supported values.
 820
 821           This value can be changed after boot using the
 822           /proc/sys/vm/mmap_rnd_bits tunable
 823
 824 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 825         bool
 826         help
 827           An arch should select this symbol if it supports running applications
 828           in compatibility mode, supports setting a variable number of bits for
 829           use in establishing the base address for mmap allocations, has MMU
 830           enabled and provides values for both:
 831           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 832           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 833
 834 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 835         int
 836
 837 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 838         int
 839
 840 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 841         int
 842
 843 config ARCH_MMAP_RND_COMPAT_BITS
 844         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 845         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 846         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 847         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 848         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 849         help
 850           This value can be used to select the number of bits to use to
 851           determine the random offset to the base address of vma regions
 852           resulting from mmap allocations for compatible applications This
 853           value will be bounded by the architecture's minimum and maximum
 854           supported values.
 855
 856           This value can be changed after boot using the
 857           /proc/sys/vm/mmap_rnd_compat_bits tunable
 858
 859 config HAVE_ARCH_COMPAT_MMAP_BASES
 860         bool
 861         help
 862           This allows 64bit applications to invoke 32-bit mmap() syscall
 863           and vice-versa 32-bit applications to call 64-bit mmap().
 864           Required for applications doing different bitness syscalls.
 865
 866 config HAVE_COPY_THREAD_TLS
 867         bool
 868         help
 869           Architecture provides copy_thread_tls to accept tls argument via
 870           normal C parameter passing, rather than extracting the syscall
 871           argument from pt_regs.
 872
 873 config HAVE_STACK_VALIDATION
 874         bool
 875         help
 876           Architecture supports the 'objtool check' host tool command, which
 877           performs compile-time stack metadata validation.
 878
 879 config HAVE_RELIABLE_STACKTRACE
 880         bool
 881         help
 882           Architecture has a save_stack_trace_tsk_reliable() function which
 883           only returns a stack trace if it can guarantee the trace is reliable.
 884
 885 config HAVE_ARCH_HASH
 886         bool
 887         default n
 888         help
 889           If this is set, the architecture provides an <asm/hash.h>
 890           file which provides platform-specific implementations of some
 891           functions in <linux/hash.h> or fs/namei.c.
 892
 893 config ISA_BUS_API
 894         def_bool ISA
 895
 896 #
 897 # ABI hall of shame
 898 #
 899 config CLONE_BACKWARDS
 900         bool
 901         help
 902           Architecture has tls passed as the 4th argument of clone(2),
 903           not the 5th one.
 904
 905 config CLONE_BACKWARDS2
 906         bool
 907         help
 908           Architecture has the first two arguments of clone(2) swapped.
 909
 910 config CLONE_BACKWARDS3
 911         bool
 912         help
 913           Architecture has tls passed as the 3rd argument of clone(2),
 914           not the 5th one.
 915
 916 config ODD_RT_SIGACTION
 917         bool
 918         help
 919           Architecture has unusual rt_sigaction(2) arguments
 920
 921 config OLD_SIGSUSPEND
 922         bool
 923         help
 924           Architecture has old sigsuspend(2) syscall, of one-argument variety
 925
 926 config OLD_SIGSUSPEND3
 927         bool
 928         help
 929           Even weirder antique ABI - three-argument sigsuspend(2)
 930
 931 config OLD_SIGACTION
 932         bool
 933         help
 934           Architecture has old sigaction(2) syscall.  Nope, not the same
 935           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 936           but fairly different variant of sigaction(2), thanks to OSF/1
 937           compatibility...
 938
 939 config COMPAT_OLD_SIGACTION
 940         bool
 941
 942 config ARCH_NO_COHERENT_DMA_MMAP
 943         bool
 944
 945 config CPU_NO_EFFICIENT_FFS
 946         def_bool n
 947
 948 config HAVE_ARCH_VMAP_STACK
 949         def_bool n
 950         help
 951           An arch should select this symbol if it can support kernel stacks
 952           in vmalloc space.  This means:
 953
 954           - vmalloc space must be large enough to hold many kernel stacks.
 955             This may rule out many 32-bit architectures.
 956
 957           - Stacks in vmalloc space need to work reliably.  For example, if
 958             vmap page tables are created on demand, either this mechanism
 959             needs to work while the stack points to a virtual address with
 960             unpopulated page tables or arch code (switch_to() and switch_mm(),
 961             most likely) needs to ensure that the stack's page table entries
 962             are populated before running on a possibly unpopulated stack.
 963
 964           - If the stack overflows into a guard page, something reasonable
 965             should happen.  The definition of "reasonable" is flexible, but
 966             instantly rebooting without logging anything would be unfriendly.
 967
 968 config VMAP_STACK
 969         default y
 970         bool "Use a virtually-mapped stack"
 971         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 972         ---help---
 973           Enable this if you want the use virtually-mapped kernel stacks
 974           with guard pages.  This causes kernel stack overflows to be
 975           caught immediately rather than causing difficult-to-diagnose
 976           corruption.
 977
 978           This is presently incompatible with KASAN because KASAN expects
 979           the stack to map directly to the KASAN shadow map using a formula
 980           that is incorrect if the stack is in vmalloc space.
 981
 982 config ARCH_OPTIONAL_KERNEL_RWX
 983         def_bool n
 984
 985 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 986         def_bool n
 987
 988 config ARCH_HAS_STRICT_KERNEL_RWX
 989         def_bool n
 990
 991 config STRICT_KERNEL_RWX
 992         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 993         depends on ARCH_HAS_STRICT_KERNEL_RWX
 994         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 995         help
 996           If this is set, kernel text and rodata memory will be made read-only,
 997           and non-text memory will be made non-executable. This provides
 998           protection against certain security exploits (e.g. executing the heap
 999           or modifying text)
1000
1001           These features are considered standard security practice these days.
1002           You should say Y here in almost all cases.
1003
1004 config ARCH_HAS_STRICT_MODULE_RWX
1005         def_bool n
1006
1007 config STRICT_MODULE_RWX
1008         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1009         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1010         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1011         help
1012           If this is set, module text and rodata memory will be made read-only,
1013           and non-text memory will be made non-executable. This provides
1014           protection against certain security exploits (e.g. writing to text)
1015
1016 config ARCH_HAS_REFCOUNT
1017         bool
1018         help
1019           An architecture selects this when it has implemented refcount_t
1020           using open coded assembly primitives that provide an optimized
1021           refcount_t implementation, possibly at the expense of some full
1022           refcount state checks of CONFIG_REFCOUNT_FULL=y.
1023
1024           The refcount overflow check behavior, however, must be retained.
1025           Catching overflows is the primary security concern for protecting
1026           against bugs in reference counts.
1027
1028 config REFCOUNT_FULL
1029         bool "Perform full reference count validation at the expense of speed"
1030         help
1031           Enabling this switches the refcounting infrastructure from a fast
1032           unchecked atomic_t implementation to a fully state checked
1033           implementation, which can be (slightly) slower but provides protections
1034           against various use-after-free conditions that can be used in
1035           security flaw exploits.
1036
1037 config HAVE_ARCH_COMPILER_H
1038         bool
1039         help
1040           An architecture can select this if it provides an
1041           asm/compiler.h header that should be included after
1042           linux/compiler-*.h in order to override macro definitions that those
1043           headers generally provide.
1044
1045 source "kernel/gcov/Kconfig"