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 ARCH_HAVE_NMI_SAFE_CMPXCHG
 340         bool
 341
 342 config HAVE_ALIGNED_STRUCT_PAGE
 343         bool
 344         help
 345           This makes sure that struct pages are double word aligned and that
 346           e.g. the SLUB allocator can perform double word atomic operations
 347           on a struct page for better performance. However selecting this
 348           might increase the size of a struct page by a word.
 349
 350 config HAVE_CMPXCHG_LOCAL
 351         bool
 352
 353 config HAVE_CMPXCHG_DOUBLE
 354         bool
 355
 356 config ARCH_WEAK_RELEASE_ACQUIRE
 357         bool
 358
 359 config ARCH_WANT_IPC_PARSE_VERSION
 360         bool
 361
 362 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 363         bool
 364
 365 config ARCH_WANT_OLD_COMPAT_IPC
 366         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 367         bool
 368
 369 config HAVE_ARCH_SECCOMP_FILTER
 370         bool
 371         help
 372           An arch should select this symbol if it provides all of these things:
 373           - syscall_get_arch()
 374           - syscall_get_arguments()
 375           - syscall_rollback()
 376           - syscall_set_return_value()
 377           - SIGSYS siginfo_t support
 378           - secure_computing is called from a ptrace_event()-safe context
 379           - secure_computing return value is checked and a return value of -1
 380             results in the system call being skipped immediately.
 381           - seccomp syscall wired up
 382
 383 config SECCOMP_FILTER
 384         def_bool y
 385         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 386         help
 387           Enable tasks to build secure computing environments defined
 388           in terms of Berkeley Packet Filter programs which implement
 389           task-defined system call filtering polices.
 390
 391           See Documentation/prctl/seccomp_filter.txt for details.
 392
 393 config HAVE_GCC_PLUGINS
 394         bool
 395         help
 396           An arch should select this symbol if it supports building with
 397           GCC plugins.
 398
 399 menuconfig GCC_PLUGINS
 400         bool "GCC plugins"
 401         depends on HAVE_GCC_PLUGINS
 402         depends on !COMPILE_TEST
 403         help
 404           GCC plugins are loadable modules that provide extra features to the
 405           compiler. They are useful for runtime instrumentation and static analysis.
 406
 407           See Documentation/gcc-plugins.txt for details.
 408
 409 config GCC_PLUGIN_CYC_COMPLEXITY
 410         bool "Compute the cyclomatic complexity of a function" if EXPERT
 411         depends on GCC_PLUGINS
 412         depends on !COMPILE_TEST
 413         help
 414           The complexity M of a function's control flow graph is defined as:
 415            M = E - N + 2P
 416           where
 417
 418           E = the number of edges
 419           N = the number of nodes
 420           P = the number of connected components (exit nodes).
 421
 422           Enabling this plugin reports the complexity to stderr during the
 423           build. It mainly serves as a simple example of how to create a
 424           gcc plugin for the kernel.
 425
 426 config GCC_PLUGIN_SANCOV
 427         bool
 428         depends on GCC_PLUGINS
 429         help
 430           This plugin inserts a __sanitizer_cov_trace_pc() call at the start of
 431           basic blocks. It supports all gcc versions with plugin support (from
 432           gcc-4.5 on). It is based on the commit "Add fuzzing coverage support"
 433           by Dmitry Vyukov <dvyukov@google.com>.
 434
 435 config GCC_PLUGIN_LATENT_ENTROPY
 436         bool "Generate some entropy during boot and runtime"
 437         depends on GCC_PLUGINS
 438         help
 439           By saying Y here the kernel will instrument some kernel code to
 440           extract some entropy from both original and artificially created
 441           program state.  This will help especially embedded systems where
 442           there is little 'natural' source of entropy normally.  The cost
 443           is some slowdown of the boot process (about 0.5%) and fork and
 444           irq processing.
 445
 446           Note that entropy extracted this way is not cryptographically
 447           secure!
 448
 449           This plugin was ported from grsecurity/PaX. More information at:
 450            * https://grsecurity.net/
 451            * https://pax.grsecurity.net/
 452
 453 config GCC_PLUGIN_STRUCTLEAK
 454         bool "Force initialization of variables containing userspace addresses"
 455         depends on GCC_PLUGINS
 456         help
 457           This plugin zero-initializes any structures containing a
 458           __user attribute. This can prevent some classes of information
 459           exposures.
 460
 461           This plugin was ported from grsecurity/PaX. More information at:
 462            * https://grsecurity.net/
 463            * https://pax.grsecurity.net/
 464
 465 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
 466         bool "Force initialize all struct type variables passed by reference"
 467         depends on GCC_PLUGIN_STRUCTLEAK
 468         help
 469           Zero initialize any struct type local variable that may be passed by
 470           reference without having been initialized.
 471
 472 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 473         bool "Report forcefully initialized variables"
 474         depends on GCC_PLUGIN_STRUCTLEAK
 475         depends on !COMPILE_TEST
 476         help
 477           This option will cause a warning to be printed each time the
 478           structleak plugin finds a variable it thinks needs to be
 479           initialized. Since not all existing initializers are detected
 480           by the plugin, this can produce false positive warnings.
 481
 482 config GCC_PLUGIN_RANDSTRUCT
 483         bool "Randomize layout of sensitive kernel structures"
 484         depends on GCC_PLUGINS
 485         select MODVERSIONS if MODULES
 486         help
 487           If you say Y here, the layouts of structures that are entirely
 488           function pointers (and have not been manually annotated with
 489           __no_randomize_layout), or structures that have been explicitly
 490           marked with __randomize_layout, will be randomized at compile-time.
 491           This can introduce the requirement of an additional information
 492           exposure vulnerability for exploits targeting these structure
 493           types.
 494
 495           Enabling this feature will introduce some performance impact,
 496           slightly increase memory usage, and prevent the use of forensic
 497           tools like Volatility against the system (unless the kernel
 498           source tree isn't cleaned after kernel installation).
 499
 500           The seed used for compilation is located at
 501           scripts/gcc-plgins/randomize_layout_seed.h.  It remains after
 502           a make clean to allow for external modules to be compiled with
 503           the existing seed and will be removed by a make mrproper or
 504           make distclean.
 505
 506           Note that the implementation requires gcc 4.7 or newer.
 507
 508           This plugin was ported from grsecurity/PaX. More information at:
 509            * https://grsecurity.net/
 510            * https://pax.grsecurity.net/
 511
 512 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
 513         bool "Use cacheline-aware structure randomization"
 514         depends on GCC_PLUGIN_RANDSTRUCT
 515         depends on !COMPILE_TEST
 516         help
 517           If you say Y here, the RANDSTRUCT randomization will make a
 518           best effort at restricting randomization to cacheline-sized
 519           groups of elements.  It will further not randomize bitfields
 520           in structures.  This reduces the performance hit of RANDSTRUCT
 521           at the cost of weakened randomization.
 522
 523 config HAVE_CC_STACKPROTECTOR
 524         bool
 525         help
 526           An arch should select this symbol if:
 527           - its compiler supports the -fstack-protector option
 528           - it has implemented a stack canary (e.g. __stack_chk_guard)
 529
 530 config CC_STACKPROTECTOR
 531         def_bool n
 532         help
 533           Set when a stack-protector mode is enabled, so that the build
 534           can enable kernel-side support for the GCC feature.
 535
 536 choice
 537         prompt "Stack Protector buffer overflow detection"
 538         depends on HAVE_CC_STACKPROTECTOR
 539         default CC_STACKPROTECTOR_NONE
 540         help
 541           This option turns on the "stack-protector" GCC feature. This
 542           feature puts, at the beginning of functions, a canary value on
 543           the stack just before the return address, and validates
 544           the value just before actually returning.  Stack based buffer
 545           overflows (that need to overwrite this return address) now also
 546           overwrite the canary, which gets detected and the attack is then
 547           neutralized via a kernel panic.
 548
 549 config CC_STACKPROTECTOR_NONE
 550         bool "None"
 551         help
 552           Disable "stack-protector" GCC feature.
 553
 554 config CC_STACKPROTECTOR_REGULAR
 555         bool "Regular"
 556         select CC_STACKPROTECTOR
 557         help
 558           Functions will have the stack-protector canary logic added if they
 559           have an 8-byte or larger character array on the stack.
 560
 561           This feature requires gcc version 4.2 or above, or a distribution
 562           gcc with the feature backported ("-fstack-protector").
 563
 564           On an x86 "defconfig" build, this feature adds canary checks to
 565           about 3% of all kernel functions, which increases kernel code size
 566           by about 0.3%.
 567
 568 config CC_STACKPROTECTOR_STRONG
 569         bool "Strong"
 570         select CC_STACKPROTECTOR
 571         help
 572           Functions will have the stack-protector canary logic added in any
 573           of the following conditions:
 574
 575           - local variable's address used as part of the right hand side of an
 576             assignment or function argument
 577           - local variable is an array (or union containing an array),
 578             regardless of array type or length
 579           - uses register local variables
 580
 581           This feature requires gcc version 4.9 or above, or a distribution
 582           gcc with the feature backported ("-fstack-protector-strong").
 583
 584           On an x86 "defconfig" build, this feature adds canary checks to
 585           about 20% of all kernel functions, which increases the kernel code
 586           size by about 2%.
 587
 588 endchoice
 589
 590 config THIN_ARCHIVES
 591         def_bool y
 592         help
 593           Select this if the architecture wants to use thin archives
 594           instead of ld -r to create the built-in.o files.
 595
 596 config LD_DEAD_CODE_DATA_ELIMINATION
 597         bool
 598         help
 599           Select this if the architecture wants to do dead code and
 600           data elimination with the linker by compiling with
 601           -ffunction-sections -fdata-sections and linking with
 602           --gc-sections.
 603
 604           This requires that the arch annotates or otherwise protects
 605           its external entry points from being discarded. Linker scripts
 606           must also merge .text.*, .data.*, and .bss.* correctly into
 607           output sections. Care must be taken not to pull in unrelated
 608           sections (e.g., '.text.init'). Typically '.' in section names
 609           is used to distinguish them from label names / C identifiers.
 610
 611 config HAVE_ARCH_WITHIN_STACK_FRAMES
 612         bool
 613         help
 614           An architecture should select this if it can walk the kernel stack
 615           frames to determine if an object is part of either the arguments
 616           or local variables (i.e. that it excludes saved return addresses,
 617           and similar) by implementing an inline arch_within_stack_frames(),
 618           which is used by CONFIG_HARDENED_USERCOPY.
 619
 620 config HAVE_CONTEXT_TRACKING
 621         bool
 622         help
 623           Provide kernel/user boundaries probes necessary for subsystems
 624           that need it, such as userspace RCU extended quiescent state.
 625           Syscalls need to be wrapped inside user_exit()-user_enter() through
 626           the slow path using TIF_NOHZ flag. Exceptions handlers must be
 627           wrapped as well. Irqs are already protected inside
 628           rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
 629           irq exit still need to be protected.
 630
 631 config HAVE_VIRT_CPU_ACCOUNTING
 632         bool
 633
 634 config ARCH_HAS_SCALED_CPUTIME
 635         bool
 636
 637 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 638         bool
 639         default y if 64BIT
 640         help
 641           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 642           Before enabling this option, arch code must be audited
 643           to ensure there are no races in concurrent read/write of
 644           cputime_t. For example, reading/writing 64-bit cputime_t on
 645           some 32-bit arches may require multiple accesses, so proper
 646           locking is needed to protect against concurrent accesses.
 647
 648
 649 config HAVE_IRQ_TIME_ACCOUNTING
 650         bool
 651         help
 652           Archs need to ensure they use a high enough resolution clock to
 653           support irq time accounting and then call enable_sched_clock_irqtime().
 654
 655 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 656         bool
 657
 658 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 659         bool
 660
 661 config HAVE_ARCH_HUGE_VMAP
 662         bool
 663
 664 config HAVE_ARCH_SOFT_DIRTY
 665         bool
 666
 667 config HAVE_MOD_ARCH_SPECIFIC
 668         bool
 669         help
 670           The arch uses struct mod_arch_specific to store data.  Many arches
 671           just need a simple module loader without arch specific data - those
 672           should not enable this.
 673
 674 config MODULES_USE_ELF_RELA
 675         bool
 676         help
 677           Modules only use ELF RELA relocations.  Modules with ELF REL
 678           relocations will give an error.
 679
 680 config MODULES_USE_ELF_REL
 681         bool
 682         help
 683           Modules only use ELF REL relocations.  Modules with ELF RELA
 684           relocations will give an error.
 685
 686 config HAVE_UNDERSCORE_SYMBOL_PREFIX
 687         bool
 688         help
 689           Some architectures generate an _ in front of C symbols; things like
 690           module loading and assembly files need to know about this.
 691
 692 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 693         bool
 694         help
 695           Architecture doesn't only execute the irq handler on the irq stack
 696           but also irq_exit(). This way we can process softirqs on this irq
 697           stack instead of switching to a new one when we call __do_softirq()
 698           in the end of an hardirq.
 699           This spares a stack switch and improves cache usage on softirq
 700           processing.
 701
 702 config PGTABLE_LEVELS
 703         int
 704         default 2
 705
 706 config ARCH_HAS_ELF_RANDOMIZE
 707         bool
 708         help
 709           An architecture supports choosing randomized locations for
 710           stack, mmap, brk, and ET_DYN. Defined functions:
 711           - arch_mmap_rnd()
 712           - arch_randomize_brk()
 713
 714 config HAVE_ARCH_MMAP_RND_BITS
 715         bool
 716         help
 717           An arch should select this symbol if it supports setting a variable
 718           number of bits for use in establishing the base address for mmap
 719           allocations, has MMU enabled and provides values for both:
 720           - ARCH_MMAP_RND_BITS_MIN
 721           - ARCH_MMAP_RND_BITS_MAX
 722
 723 config HAVE_EXIT_THREAD
 724         bool
 725         help
 726           An architecture implements exit_thread.
 727
 728 config ARCH_MMAP_RND_BITS_MIN
 729         int
 730
 731 config ARCH_MMAP_RND_BITS_MAX
 732         int
 733
 734 config ARCH_MMAP_RND_BITS_DEFAULT
 735         int
 736
 737 config ARCH_MMAP_RND_BITS
 738         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 739         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 740         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 741         default ARCH_MMAP_RND_BITS_MIN
 742         depends on HAVE_ARCH_MMAP_RND_BITS
 743         help
 744           This value can be used to select the number of bits to use to
 745           determine the random offset to the base address of vma regions
 746           resulting from mmap allocations. This value will be bounded
 747           by the architecture's minimum and maximum supported values.
 748
 749           This value can be changed after boot using the
 750           /proc/sys/vm/mmap_rnd_bits tunable
 751
 752 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 753         bool
 754         help
 755           An arch should select this symbol if it supports running applications
 756           in compatibility mode, supports setting a variable number of bits for
 757           use in establishing the base address for mmap allocations, has MMU
 758           enabled and provides values for both:
 759           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 760           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 761
 762 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 763         int
 764
 765 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 766         int
 767
 768 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 769         int
 770
 771 config ARCH_MMAP_RND_COMPAT_BITS
 772         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 773         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 774         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 775         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 776         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 777         help
 778           This value can be used to select the number of bits to use to
 779           determine the random offset to the base address of vma regions
 780           resulting from mmap allocations for compatible applications This
 781           value will be bounded by the architecture's minimum and maximum
 782           supported values.
 783
 784           This value can be changed after boot using the
 785           /proc/sys/vm/mmap_rnd_compat_bits tunable
 786
 787 config HAVE_ARCH_COMPAT_MMAP_BASES
 788         bool
 789         help
 790           This allows 64bit applications to invoke 32-bit mmap() syscall
 791           and vice-versa 32-bit applications to call 64-bit mmap().
 792           Required for applications doing different bitness syscalls.
 793
 794 config HAVE_COPY_THREAD_TLS
 795         bool
 796         help
 797           Architecture provides copy_thread_tls to accept tls argument via
 798           normal C parameter passing, rather than extracting the syscall
 799           argument from pt_regs.
 800
 801 config HAVE_STACK_VALIDATION
 802         bool
 803         help
 804           Architecture supports the 'objtool check' host tool command, which
 805           performs compile-time stack metadata validation.
 806
 807 config HAVE_RELIABLE_STACKTRACE
 808         bool
 809         help
 810           Architecture has a save_stack_trace_tsk_reliable() function which
 811           only returns a stack trace if it can guarantee the trace is reliable.
 812
 813 config HAVE_ARCH_HASH
 814         bool
 815         default n
 816         help
 817           If this is set, the architecture provides an <asm/hash.h>
 818           file which provides platform-specific implementations of some
 819           functions in <linux/hash.h> or fs/namei.c.
 820
 821 config ISA_BUS_API
 822         def_bool ISA
 823
 824 #
 825 # ABI hall of shame
 826 #
 827 config CLONE_BACKWARDS
 828         bool
 829         help
 830           Architecture has tls passed as the 4th argument of clone(2),
 831           not the 5th one.
 832
 833 config CLONE_BACKWARDS2
 834         bool
 835         help
 836           Architecture has the first two arguments of clone(2) swapped.
 837
 838 config CLONE_BACKWARDS3
 839         bool
 840         help
 841           Architecture has tls passed as the 3rd argument of clone(2),
 842           not the 5th one.
 843
 844 config ODD_RT_SIGACTION
 845         bool
 846         help
 847           Architecture has unusual rt_sigaction(2) arguments
 848
 849 config OLD_SIGSUSPEND
 850         bool
 851         help
 852           Architecture has old sigsuspend(2) syscall, of one-argument variety
 853
 854 config OLD_SIGSUSPEND3
 855         bool
 856         help
 857           Even weirder antique ABI - three-argument sigsuspend(2)
 858
 859 config OLD_SIGACTION
 860         bool
 861         help
 862           Architecture has old sigaction(2) syscall.  Nope, not the same
 863           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
 864           but fairly different variant of sigaction(2), thanks to OSF/1
 865           compatibility...
 866
 867 config COMPAT_OLD_SIGACTION
 868         bool
 869
 870 config ARCH_NO_COHERENT_DMA_MMAP
 871         bool
 872
 873 config CPU_NO_EFFICIENT_FFS
 874         def_bool n
 875
 876 config HAVE_ARCH_VMAP_STACK
 877         def_bool n
 878         help
 879           An arch should select this symbol if it can support kernel stacks
 880           in vmalloc space.  This means:
 881
 882           - vmalloc space must be large enough to hold many kernel stacks.
 883             This may rule out many 32-bit architectures.
 884
 885           - Stacks in vmalloc space need to work reliably.  For example, if
 886             vmap page tables are created on demand, either this mechanism
 887             needs to work while the stack points to a virtual address with
 888             unpopulated page tables or arch code (switch_to() and switch_mm(),
 889             most likely) needs to ensure that the stack's page table entries
 890             are populated before running on a possibly unpopulated stack.
 891
 892           - If the stack overflows into a guard page, something reasonable
 893             should happen.  The definition of "reasonable" is flexible, but
 894             instantly rebooting without logging anything would be unfriendly.
 895
 896 config VMAP_STACK
 897         default y
 898         bool "Use a virtually-mapped stack"
 899         depends on HAVE_ARCH_VMAP_STACK && !KASAN
 900         ---help---
 901           Enable this if you want the use virtually-mapped kernel stacks
 902           with guard pages.  This causes kernel stack overflows to be
 903           caught immediately rather than causing difficult-to-diagnose
 904           corruption.
 905
 906           This is presently incompatible with KASAN because KASAN expects
 907           the stack to map directly to the KASAN shadow map using a formula
 908           that is incorrect if the stack is in vmalloc space.
 909
 910 config ARCH_OPTIONAL_KERNEL_RWX
 911         def_bool n
 912
 913 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 914         def_bool n
 915
 916 config ARCH_HAS_STRICT_KERNEL_RWX
 917         def_bool n
 918
 919 config STRICT_KERNEL_RWX
 920         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
 921         depends on ARCH_HAS_STRICT_KERNEL_RWX
 922         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 923         help
 924           If this is set, kernel text and rodata memory will be made read-only,
 925           and non-text memory will be made non-executable. This provides
 926           protection against certain security exploits (e.g. executing the heap
 927           or modifying text)
 928
 929           These features are considered standard security practice these days.
 930           You should say Y here in almost all cases.
 931
 932 config ARCH_HAS_STRICT_MODULE_RWX
 933         def_bool n
 934
 935 config STRICT_MODULE_RWX
 936         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
 937         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
 938         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 939         help
 940           If this is set, module text and rodata memory will be made read-only,
 941           and non-text memory will be made non-executable. This provides
 942           protection against certain security exploits (e.g. writing to text)
 943
 944 config ARCH_HAS_REFCOUNT
 945         bool
 946         help
 947           An architecture selects this when it has implemented refcount_t
 948           using open coded assembly primitives that provide an optimized
 949           refcount_t implementation, possibly at the expense of some full
 950           refcount state checks of CONFIG_REFCOUNT_FULL=y.
 951
 952           The refcount overflow check behavior, however, must be retained.
 953           Catching overflows is the primary security concern for protecting
 954           against bugs in reference counts.
 955
 956 config REFCOUNT_FULL
 957         bool "Perform full reference count validation at the expense of speed"
 958         help
 959           Enabling this switches the refcounting infrastructure from a fast
 960           unchecked atomic_t implementation to a fully state checked
 961           implementation, which can be (slightly) slower but provides protections
 962           against various use-after-free conditions that can be used in
 963           security flaw exploits.
 964
 965 source "kernel/gcov/Kconfig"