arch/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 #
   3 # General architecture dependent options
   4 #
   5
   6 #
   7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
   8 # override the default values in this file.
   9 #
  10 source "arch/$(SRCARCH)/Kconfig"
  11
  12 menu "General architecture-dependent options"
  13
  14 config CRASH_CORE
  15         bool
  16
  17 config KEXEC_CORE
  18         select CRASH_CORE
  19         bool
  20
  21 config KEXEC_ELF
  22         bool
  23
  24 config HAVE_IMA_KEXEC
  25         bool
  26
  27 config SET_FS
  28         bool
  29
  30 config HOTPLUG_SMT
  31         bool
  32
  33 config GENERIC_ENTRY
  34        bool
  35
  36 config KPROBES
  37         bool "Kprobes"
  38         depends on MODULES
  39         depends on HAVE_KPROBES
  40         select KALLSYMS
  41         help
  42           Kprobes allows you to trap at almost any kernel address and
  43           execute a callback function.  register_kprobe() establishes
  44           a probepoint and specifies the callback.  Kprobes is useful
  45           for kernel debugging, non-intrusive instrumentation and testing.
  46           If in doubt, say "N".
  47
  48 config JUMP_LABEL
  49         bool "Optimize very unlikely/likely branches"
  50         depends on HAVE_ARCH_JUMP_LABEL
  51         depends on CC_HAS_ASM_GOTO
  52         help
  53          This option enables a transparent branch optimization that
  54          makes certain almost-always-true or almost-always-false branch
  55          conditions even cheaper to execute within the kernel.
  56
  57          Certain performance-sensitive kernel code, such as trace points,
  58          scheduler functionality, networking code and KVM have such
  59          branches and include support for this optimization technique.
  60
  61          If it is detected that the compiler has support for "asm goto",
  62          the kernel will compile such branches with just a nop
  63          instruction. When the condition flag is toggled to true, the
  64          nop will be converted to a jump instruction to execute the
  65          conditional block of instructions.
  66
  67          This technique lowers overhead and stress on the branch prediction
  68          of the processor and generally makes the kernel faster. The update
  69          of the condition is slower, but those are always very rare.
  70
  71          ( On 32-bit x86, the necessary options added to the compiler
  72            flags may increase the size of the kernel slightly. )
  73
  74 config STATIC_KEYS_SELFTEST
  75         bool "Static key selftest"
  76         depends on JUMP_LABEL
  77         help
  78           Boot time self-test of the branch patching code.
  79
  80 config STATIC_CALL_SELFTEST
  81         bool "Static call selftest"
  82         depends on HAVE_STATIC_CALL
  83         help
  84           Boot time self-test of the call patching code.
  85
  86 config OPTPROBES
  87         def_bool y
  88         depends on KPROBES && HAVE_OPTPROBES
  89         select TASKS_RCU if PREEMPTION
  90
  91 config KPROBES_ON_FTRACE
  92         def_bool y
  93         depends on KPROBES && HAVE_KPROBES_ON_FTRACE
  94         depends on DYNAMIC_FTRACE_WITH_REGS
  95         help
  96          If function tracer is enabled and the arch supports full
  97          passing of pt_regs to function tracing, then kprobes can
  98          optimize on top of function tracing.
  99
 100 config UPROBES
 101         def_bool n
 102         depends on ARCH_SUPPORTS_UPROBES
 103         help
 104           Uprobes is the user-space counterpart to kprobes: they
 105           enable instrumentation applications (such as 'perf probe')
 106           to establish unintrusive probes in user-space binaries and
 107           libraries, by executing handler functions when the probes
 108           are hit by user-space applications.
 109
 110           ( These probes come in the form of single-byte breakpoints,
 111             managed by the kernel and kept transparent to the probed
 112             application. )
 113
 114 config HAVE_64BIT_ALIGNED_ACCESS
 115         def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
 116         help
 117           Some architectures require 64 bit accesses to be 64 bit
 118           aligned, which also requires structs containing 64 bit values
 119           to be 64 bit aligned too. This includes some 32 bit
 120           architectures which can do 64 bit accesses, as well as 64 bit
 121           architectures without unaligned access.
 122
 123           This symbol should be selected by an architecture if 64 bit
 124           accesses are required to be 64 bit aligned in this way even
 125           though it is not a 64 bit architecture.
 126
 127           See Documentation/core-api/unaligned-memory-access.rst for
 128           more information on the topic of unaligned memory accesses.
 129
 130 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 131         bool
 132         help
 133           Some architectures are unable to perform unaligned accesses
 134           without the use of get_unaligned/put_unaligned. Others are
 135           unable to perform such accesses efficiently (e.g. trap on
 136           unaligned access and require fixing it up in the exception
 137           handler.)
 138
 139           This symbol should be selected by an architecture if it can
 140           perform unaligned accesses efficiently to allow different
 141           code paths to be selected for these cases. Some network
 142           drivers, for example, could opt to not fix up alignment
 143           problems with received packets if doing so would not help
 144           much.
 145
 146           See Documentation/core-api/unaligned-memory-access.rst for more
 147           information on the topic of unaligned memory accesses.
 148
 149 config ARCH_USE_BUILTIN_BSWAP
 150         bool
 151         help
 152          Modern versions of GCC (since 4.4) have builtin functions
 153          for handling byte-swapping. Using these, instead of the old
 154          inline assembler that the architecture code provides in the
 155          __arch_bswapXX() macros, allows the compiler to see what's
 156          happening and offers more opportunity for optimisation. In
 157          particular, the compiler will be able to combine the byteswap
 158          with a nearby load or store and use load-and-swap or
 159          store-and-swap instructions if the architecture has them. It
 160          should almost *never* result in code which is worse than the
 161          hand-coded assembler in <asm/swab.h>.  But just in case it
 162          does, the use of the builtins is optional.
 163
 164          Any architecture with load-and-swap or store-and-swap
 165          instructions should set this. And it shouldn't hurt to set it
 166          on architectures that don't have such instructions.
 167
 168 config KRETPROBES
 169         def_bool y
 170         depends on KPROBES && HAVE_KRETPROBES
 171
 172 config USER_RETURN_NOTIFIER
 173         bool
 174         depends on HAVE_USER_RETURN_NOTIFIER
 175         help
 176           Provide a kernel-internal notification when a cpu is about to
 177           switch to user mode.
 178
 179 config HAVE_IOREMAP_PROT
 180         bool
 181
 182 config HAVE_KPROBES
 183         bool
 184
 185 config HAVE_KRETPROBES
 186         bool
 187
 188 config HAVE_OPTPROBES
 189         bool
 190
 191 config HAVE_KPROBES_ON_FTRACE
 192         bool
 193
 194 config HAVE_FUNCTION_ERROR_INJECTION
 195         bool
 196
 197 config HAVE_NMI
 198         bool
 199
 200 config TRACE_IRQFLAGS_SUPPORT
 201         bool
 202
 203 #
 204 # An arch should select this if it provides all these things:
 205 #
 206 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 207 #       arch_has_single_step()  if there is hardware single-step support
 208 #       arch_has_block_step()   if there is hardware block-step support
 209 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 210 #       linux/regset.h          user_regset interfaces
 211 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 212 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 213 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 214 #       signal delivery         calls tracehook_signal_handler()
 215 #
 216 config HAVE_ARCH_TRACEHOOK
 217         bool
 218
 219 config HAVE_DMA_CONTIGUOUS
 220         bool
 221
 222 config GENERIC_SMP_IDLE_THREAD
 223         bool
 224
 225 config GENERIC_IDLE_POLL_SETUP
 226         bool
 227
 228 config ARCH_HAS_FORTIFY_SOURCE
 229         bool
 230         help
 231           An architecture should select this when it can successfully
 232           build and run with CONFIG_FORTIFY_SOURCE.
 233
 234 #
 235 # Select if the arch provides a historic keepinit alias for the retain_initrd
 236 # command line option
 237 #
 238 config ARCH_HAS_KEEPINITRD
 239         bool
 240
 241 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 242 config ARCH_HAS_SET_MEMORY
 243         bool
 244
 245 # Select if arch has all set_direct_map_invalid/default() functions
 246 config ARCH_HAS_SET_DIRECT_MAP
 247         bool
 248
 249 #
 250 # Select if the architecture provides the arch_dma_set_uncached symbol to
 251 # either provide an uncached segment alias for a DMA allocation, or
 252 # to remap the page tables in place.
 253 #
 254 config ARCH_HAS_DMA_SET_UNCACHED
 255         bool
 256
 257 #
 258 # Select if the architectures provides the arch_dma_clear_uncached symbol
 259 # to undo an in-place page table remap for uncached access.
 260 #
 261 config ARCH_HAS_DMA_CLEAR_UNCACHED
 262         bool
 263
 264 # Select if arch init_task must go in the __init_task_data section
 265 config ARCH_TASK_STRUCT_ON_STACK
 266         bool
 267
 268 # Select if arch has its private alloc_task_struct() function
 269 config ARCH_TASK_STRUCT_ALLOCATOR
 270         bool
 271
 272 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 273         bool
 274         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 275         help
 276           An architecture should select this to provide hardened usercopy
 277           knowledge about what region of the thread_struct should be
 278           whitelisted for copying to userspace. Normally this is only the
 279           FPU registers. Specifically, arch_thread_struct_whitelist()
 280           should be implemented. Without this, the entire thread_struct
 281           field in task_struct will be left whitelisted.
 282
 283 # Select if arch has its private alloc_thread_stack() function
 284 config ARCH_THREAD_STACK_ALLOCATOR
 285         bool
 286
 287 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 288 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 289         bool
 290
 291 config ARCH_WANTS_NO_INSTR
 292         bool
 293         help
 294           An architecture should select this if the noinstr macro is being used on
 295           functions to denote that the toolchain should avoid instrumenting such
 296           functions and is required for correctness.
 297
 298 config ARCH_32BIT_OFF_T
 299         bool
 300         depends on !64BIT
 301         help
 302           All new 32-bit architectures should have 64-bit off_t type on
 303           userspace side which corresponds to the loff_t kernel type. This
 304           is the requirement for modern ABIs. Some existing architectures
 305           still support 32-bit off_t. This option is enabled for all such
 306           architectures explicitly.
 307
 308 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
 309 config ARCH_32BIT_USTAT_F_TINODE
 310         bool
 311
 312 config HAVE_ASM_MODVERSIONS
 313         bool
 314         help
 315           This symbol should be selected by an architecture if it provides
 316           <asm/asm-prototypes.h> to support the module versioning for symbols
 317           exported from assembly code.
 318
 319 config HAVE_REGS_AND_STACK_ACCESS_API
 320         bool
 321         help
 322           This symbol should be selected by an architecture if it supports
 323           the API needed to access registers and stack entries from pt_regs,
 324           declared in asm/ptrace.h
 325           For example the kprobes-based event tracer needs this API.
 326
 327 config HAVE_RSEQ
 328         bool
 329         depends on HAVE_REGS_AND_STACK_ACCESS_API
 330         help
 331           This symbol should be selected by an architecture if it
 332           supports an implementation of restartable sequences.
 333
 334 config HAVE_FUNCTION_ARG_ACCESS_API
 335         bool
 336         help
 337           This symbol should be selected by an architecture if it supports
 338           the API needed to access function arguments from pt_regs,
 339           declared in asm/ptrace.h
 340
 341 config HAVE_HW_BREAKPOINT
 342         bool
 343         depends on PERF_EVENTS
 344
 345 config HAVE_MIXED_BREAKPOINTS_REGS
 346         bool
 347         depends on HAVE_HW_BREAKPOINT
 348         help
 349           Depending on the arch implementation of hardware breakpoints,
 350           some of them have separate registers for data and instruction
 351           breakpoints addresses, others have mixed registers to store
 352           them but define the access type in a control register.
 353           Select this option if your arch implements breakpoints under the
 354           latter fashion.
 355
 356 config HAVE_USER_RETURN_NOTIFIER
 357         bool
 358
 359 config HAVE_PERF_EVENTS_NMI
 360         bool
 361         help
 362           System hardware can generate an NMI using the perf event
 363           subsystem.  Also has support for calculating CPU cycle events
 364           to determine how many clock cycles in a given period.
 365
 366 config HAVE_HARDLOCKUP_DETECTOR_PERF
 367         bool
 368         depends on HAVE_PERF_EVENTS_NMI
 369         help
 370           The arch chooses to use the generic perf-NMI-based hardlockup
 371           detector. Must define HAVE_PERF_EVENTS_NMI.
 372
 373 config HAVE_NMI_WATCHDOG
 374         depends on HAVE_NMI
 375         bool
 376         help
 377           The arch provides a low level NMI watchdog. It provides
 378           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 379
 380 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 381         bool
 382         select HAVE_NMI_WATCHDOG
 383         help
 384           The arch chooses to provide its own hardlockup detector, which is
 385           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 386           interfaces and parameters provided by hardlockup detector subsystem.
 387
 388 config HAVE_PERF_REGS
 389         bool
 390         help
 391           Support selective register dumps for perf events. This includes
 392           bit-mapping of each registers and a unique architecture id.
 393
 394 config HAVE_PERF_USER_STACK_DUMP
 395         bool
 396         help
 397           Support user stack dumps for perf event samples. This needs
 398           access to the user stack pointer which is not unified across
 399           architectures.
 400
 401 config HAVE_ARCH_JUMP_LABEL
 402         bool
 403
 404 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 405         bool
 406
 407 config MMU_GATHER_TABLE_FREE
 408         bool
 409
 410 config MMU_GATHER_RCU_TABLE_FREE
 411         bool
 412         select MMU_GATHER_TABLE_FREE
 413
 414 config MMU_GATHER_PAGE_SIZE
 415         bool
 416
 417 config MMU_GATHER_NO_RANGE
 418         bool
 419
 420 config MMU_GATHER_NO_GATHER
 421         bool
 422         depends on MMU_GATHER_TABLE_FREE
 423
 424 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 425         bool
 426         help
 427           Temporary select until all architectures can be converted to have
 428           irqs disabled over activate_mm. Architectures that do IPI based TLB
 429           shootdowns should enable this.
 430
 431 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 432         bool
 433
 434 config HAVE_ALIGNED_STRUCT_PAGE
 435         bool
 436         help
 437           This makes sure that struct pages are double word aligned and that
 438           e.g. the SLUB allocator can perform double word atomic operations
 439           on a struct page for better performance. However selecting this
 440           might increase the size of a struct page by a word.
 441
 442 config HAVE_CMPXCHG_LOCAL
 443         bool
 444
 445 config HAVE_CMPXCHG_DOUBLE
 446         bool
 447
 448 config ARCH_WEAK_RELEASE_ACQUIRE
 449         bool
 450
 451 config ARCH_WANT_IPC_PARSE_VERSION
 452         bool
 453
 454 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 455         bool
 456
 457 config ARCH_WANT_OLD_COMPAT_IPC
 458         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 459         bool
 460
 461 config HAVE_ARCH_SECCOMP
 462         bool
 463         help
 464           An arch should select this symbol to support seccomp mode 1 (the fixed
 465           syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 466           and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 467           - __NR_seccomp_read_32
 468           - __NR_seccomp_write_32
 469           - __NR_seccomp_exit_32
 470           - __NR_seccomp_sigreturn_32
 471
 472 config HAVE_ARCH_SECCOMP_FILTER
 473         bool
 474         select HAVE_ARCH_SECCOMP
 475         help
 476           An arch should select this symbol if it provides all of these things:
 477           - all the requirements for HAVE_ARCH_SECCOMP
 478           - syscall_get_arch()
 479           - syscall_get_arguments()
 480           - syscall_rollback()
 481           - syscall_set_return_value()
 482           - SIGSYS siginfo_t support
 483           - secure_computing is called from a ptrace_event()-safe context
 484           - secure_computing return value is checked and a return value of -1
 485             results in the system call being skipped immediately.
 486           - seccomp syscall wired up
 487           - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
 488             SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
 489             COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
 490
 491 config SECCOMP
 492         prompt "Enable seccomp to safely execute untrusted bytecode"
 493         def_bool y
 494         depends on HAVE_ARCH_SECCOMP
 495         help
 496           This kernel feature is useful for number crunching applications
 497           that may need to handle untrusted bytecode during their
 498           execution. By using pipes or other transports made available
 499           to the process as file descriptors supporting the read/write
 500           syscalls, it's possible to isolate those applications in their
 501           own address space using seccomp. Once seccomp is enabled via
 502           prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 503           disabled and the task is only allowed to execute a few safe
 504           syscalls defined by each seccomp mode.
 505
 506           If unsure, say Y.
 507
 508 config SECCOMP_FILTER
 509         def_bool y
 510         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 511         help
 512           Enable tasks to build secure computing environments defined
 513           in terms of Berkeley Packet Filter programs which implement
 514           task-defined system call filtering polices.
 515
 516           See Documentation/userspace-api/seccomp_filter.rst for details.
 517
 518 config SECCOMP_CACHE_DEBUG
 519         bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
 520         depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
 521         depends on PROC_FS
 522         help
 523           This enables the /proc/pid/seccomp_cache interface to monitor
 524           seccomp cache data. The file format is subject to change. Reading
 525           the file requires CAP_SYS_ADMIN.
 526
 527           This option is for debugging only. Enabling presents the risk that
 528           an adversary may be able to infer the seccomp filter logic.
 529
 530           If unsure, say N.
 531
 532 config HAVE_ARCH_STACKLEAK
 533         bool
 534         help
 535           An architecture should select this if it has the code which
 536           fills the used part of the kernel stack with the STACKLEAK_POISON
 537           value before returning from system calls.
 538
 539 config HAVE_STACKPROTECTOR
 540         bool
 541         help
 542           An arch should select this symbol if:
 543           - it has implemented a stack canary (e.g. __stack_chk_guard)
 544
 545 config STACKPROTECTOR
 546         bool "Stack Protector buffer overflow detection"
 547         depends on HAVE_STACKPROTECTOR
 548         depends on $(cc-option,-fstack-protector)
 549         default y
 550         help
 551           This option turns on the "stack-protector" GCC feature. This
 552           feature puts, at the beginning of functions, a canary value on
 553           the stack just before the return address, and validates
 554           the value just before actually returning.  Stack based buffer
 555           overflows (that need to overwrite this return address) now also
 556           overwrite the canary, which gets detected and the attack is then
 557           neutralized via a kernel panic.
 558
 559           Functions will have the stack-protector canary logic added if they
 560           have an 8-byte or larger character array on the stack.
 561
 562           This feature requires gcc version 4.2 or above, or a distribution
 563           gcc with the feature backported ("-fstack-protector").
 564
 565           On an x86 "defconfig" build, this feature adds canary checks to
 566           about 3% of all kernel functions, which increases kernel code size
 567           by about 0.3%.
 568
 569 config STACKPROTECTOR_STRONG
 570         bool "Strong Stack Protector"
 571         depends on STACKPROTECTOR
 572         depends on $(cc-option,-fstack-protector-strong)
 573         default y
 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 ARCH_SUPPORTS_SHADOW_CALL_STACK
 592         bool
 593         help
 594           An architecture should select this if it supports Clang's Shadow
 595           Call Stack and implements runtime support for shadow stack
 596           switching.
 597
 598 config SHADOW_CALL_STACK
 599         bool "Clang Shadow Call Stack"
 600         depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
 601         depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 602         help
 603           This option enables Clang's Shadow Call Stack, which uses a
 604           shadow stack to protect function return addresses from being
 605           overwritten by an attacker. More information can be found in
 606           Clang's documentation:
 607
 608             https://clang.llvm.org/docs/ShadowCallStack.html
 609
 610           Note that security guarantees in the kernel differ from the
 611           ones documented for user space. The kernel must store addresses
 612           of shadow stacks in memory, which means an attacker capable of
 613           reading and writing arbitrary memory may be able to locate them
 614           and hijack control flow by modifying the stacks.
 615
 616 config LTO
 617         bool
 618         help
 619           Selected if the kernel will be built using the compiler's LTO feature.
 620
 621 config LTO_CLANG
 622         bool
 623         select LTO
 624         help
 625           Selected if the kernel will be built using Clang's LTO feature.
 626
 627 config ARCH_SUPPORTS_LTO_CLANG
 628         bool
 629         help
 630           An architecture should select this option if it supports:
 631           - compiling with Clang,
 632           - compiling inline assembly with Clang's integrated assembler,
 633           - and linking with LLD.
 634
 635 config ARCH_SUPPORTS_LTO_CLANG_THIN
 636         bool
 637         help
 638           An architecture should select this option if it can support Clang's
 639           ThinLTO mode.
 640
 641 config HAS_LTO_CLANG
 642         def_bool y
 643         # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
 644         depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
 645         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 646         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 647         depends on ARCH_SUPPORTS_LTO_CLANG
 648         depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 649         depends on !KASAN || KASAN_HW_TAGS
 650         depends on !GCOV_KERNEL
 651         help
 652           The compiler and Kconfig options support building with Clang's
 653           LTO.
 654
 655 choice
 656         prompt "Link Time Optimization (LTO)"
 657         default LTO_NONE
 658         help
 659           This option enables Link Time Optimization (LTO), which allows the
 660           compiler to optimize binaries globally.
 661
 662           If unsure, select LTO_NONE. Note that LTO is very resource-intensive
 663           so it's disabled by default.
 664
 665 config LTO_NONE
 666         bool "None"
 667         help
 668           Build the kernel normally, without Link Time Optimization (LTO).
 669
 670 config LTO_CLANG_FULL
 671         bool "Clang Full LTO (EXPERIMENTAL)"
 672         depends on HAS_LTO_CLANG
 673         depends on !COMPILE_TEST
 674         select LTO_CLANG
 675         help
 676           This option enables Clang's full Link Time Optimization (LTO), which
 677           allows the compiler to optimize the kernel globally. If you enable
 678           this option, the compiler generates LLVM bitcode instead of ELF
 679           object files, and the actual compilation from bitcode happens at
 680           the LTO link step, which may take several minutes depending on the
 681           kernel configuration. More information can be found from LLVM's
 682           documentation:
 683
 684             https://llvm.org/docs/LinkTimeOptimization.html
 685
 686           During link time, this option can use a large amount of RAM, and
 687           may take much longer than the ThinLTO option.
 688
 689 config LTO_CLANG_THIN
 690         bool "Clang ThinLTO (EXPERIMENTAL)"
 691         depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
 692         select LTO_CLANG
 693         help
 694           This option enables Clang's ThinLTO, which allows for parallel
 695           optimization and faster incremental compiles compared to the
 696           CONFIG_LTO_CLANG_FULL option. More information can be found
 697           from Clang's documentation:
 698
 699             https://clang.llvm.org/docs/ThinLTO.html
 700
 701           If unsure, say Y.
 702 endchoice
 703
 704 config ARCH_SUPPORTS_CFI_CLANG
 705         bool
 706         help
 707           An architecture should select this option if it can support Clang's
 708           Control-Flow Integrity (CFI) checking.
 709
 710 config CFI_CLANG
 711         bool "Use Clang's Control Flow Integrity (CFI)"
 712         depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG
 713         # Clang >= 12:
 714         # - https://bugs.llvm.org/show_bug.cgi?id=46258
 715         # - https://bugs.llvm.org/show_bug.cgi?id=47479
 716         depends on CLANG_VERSION >= 120000
 717         select KALLSYMS
 718         help
 719           This option enables Clang’s forward-edge Control Flow Integrity
 720           (CFI) checking, where the compiler injects a runtime check to each
 721           indirect function call to ensure the target is a valid function with
 722           the correct static type. This restricts possible call targets and
 723           makes it more difficult for an attacker to exploit bugs that allow
 724           the modification of stored function pointers. More information can be
 725           found from Clang's documentation:
 726
 727             https://clang.llvm.org/docs/ControlFlowIntegrity.html
 728
 729 config CFI_CLANG_SHADOW
 730         bool "Use CFI shadow to speed up cross-module checks"
 731         default y
 732         depends on CFI_CLANG && MODULES
 733         help
 734           If you select this option, the kernel builds a fast look-up table of
 735           CFI check functions in loaded modules to reduce performance overhead.
 736
 737           If unsure, say Y.
 738
 739 config CFI_PERMISSIVE
 740         bool "Use CFI in permissive mode"
 741         depends on CFI_CLANG
 742         help
 743           When selected, Control Flow Integrity (CFI) violations result in a
 744           warning instead of a kernel panic. This option should only be used
 745           for finding indirect call type mismatches during development.
 746
 747           If unsure, say N.
 748
 749 config HAVE_ARCH_WITHIN_STACK_FRAMES
 750         bool
 751         help
 752           An architecture should select this if it can walk the kernel stack
 753           frames to determine if an object is part of either the arguments
 754           or local variables (i.e. that it excludes saved return addresses,
 755           and similar) by implementing an inline arch_within_stack_frames(),
 756           which is used by CONFIG_HARDENED_USERCOPY.
 757
 758 config HAVE_CONTEXT_TRACKING
 759         bool
 760         help
 761           Provide kernel/user boundaries probes necessary for subsystems
 762           that need it, such as userspace RCU extended quiescent state.
 763           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 764           optimized behind static key or through the slow path using TIF_NOHZ
 765           flag. Exceptions handlers must be wrapped as well. Irqs are already
 766           protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
 767           handling on irq exit still need to be protected.
 768
 769 config HAVE_CONTEXT_TRACKING_OFFSTACK
 770         bool
 771         help
 772           Architecture neither relies on exception_enter()/exception_exit()
 773           nor on schedule_user(). Also preempt_schedule_notrace() and
 774           preempt_schedule_irq() can't be called in a preemptible section
 775           while context tracking is CONTEXT_USER. This feature reflects a sane
 776           entry implementation where the following requirements are met on
 777           critical entry code, ie: before user_exit() or after user_enter():
 778
 779           - Critical entry code isn't preemptible (or better yet:
 780             not interruptible).
 781           - No use of RCU read side critical sections, unless rcu_nmi_enter()
 782             got called.
 783           - No use of instrumentation, unless instrumentation_begin() got
 784             called.
 785
 786 config HAVE_TIF_NOHZ
 787         bool
 788         help
 789           Arch relies on TIF_NOHZ and syscall slow path to implement context
 790           tracking calls to user_enter()/user_exit().
 791
 792 config HAVE_VIRT_CPU_ACCOUNTING
 793         bool
 794
 795 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
 796         bool
 797         help
 798           Architecture has its own way to account idle CPU time and therefore
 799           doesn't implement vtime_account_idle().
 800
 801 config ARCH_HAS_SCALED_CPUTIME
 802         bool
 803
 804 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 805         bool
 806         default y if 64BIT
 807         help
 808           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 809           Before enabling this option, arch code must be audited
 810           to ensure there are no races in concurrent read/write of
 811           cputime_t. For example, reading/writing 64-bit cputime_t on
 812           some 32-bit arches may require multiple accesses, so proper
 813           locking is needed to protect against concurrent accesses.
 814
 815 config HAVE_IRQ_TIME_ACCOUNTING
 816         bool
 817         help
 818           Archs need to ensure they use a high enough resolution clock to
 819           support irq time accounting and then call enable_sched_clock_irqtime().
 820
 821 config HAVE_MOVE_PUD
 822         bool
 823         help
 824           Architectures that select this are able to move page tables at the
 825           PUD level. If there are only 3 page table levels, the move effectively
 826           happens at the PGD level.
 827
 828 config HAVE_MOVE_PMD
 829         bool
 830         help
 831           Archs that select this are able to move page tables at the PMD level.
 832
 833 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 834         bool
 835
 836 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 837         bool
 838
 839 config HAVE_ARCH_HUGE_VMAP
 840         bool
 841
 842 #
 843 #  Archs that select this would be capable of PMD-sized vmaps (i.e.,
 844 #  arch_vmap_pmd_supported() returns true), and they must make no assumptions
 845 #  that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag
 846 #  can be used to prohibit arch-specific allocations from using hugepages to
 847 #  help with this (e.g., modules may require it).
 848 #
 849 config HAVE_ARCH_HUGE_VMALLOC
 850         depends on HAVE_ARCH_HUGE_VMAP
 851         bool
 852
 853 config ARCH_WANT_HUGE_PMD_SHARE
 854         bool
 855
 856 config HAVE_ARCH_SOFT_DIRTY
 857         bool
 858
 859 config HAVE_MOD_ARCH_SPECIFIC
 860         bool
 861         help
 862           The arch uses struct mod_arch_specific to store data.  Many arches
 863           just need a simple module loader without arch specific data - those
 864           should not enable this.
 865
 866 config MODULES_USE_ELF_RELA
 867         bool
 868         help
 869           Modules only use ELF RELA relocations.  Modules with ELF REL
 870           relocations will give an error.
 871
 872 config MODULES_USE_ELF_REL
 873         bool
 874         help
 875           Modules only use ELF REL relocations.  Modules with ELF RELA
 876           relocations will give an error.
 877
 878 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 879         bool
 880         help
 881           Architecture doesn't only execute the irq handler on the irq stack
 882           but also irq_exit(). This way we can process softirqs on this irq
 883           stack instead of switching to a new one when we call __do_softirq()
 884           in the end of an hardirq.
 885           This spares a stack switch and improves cache usage on softirq
 886           processing.
 887
 888 config HAVE_SOFTIRQ_ON_OWN_STACK
 889         bool
 890         help
 891           Architecture provides a function to run __do_softirq() on a
 892           separate stack.
 893
 894 config PGTABLE_LEVELS
 895         int
 896         default 2
 897
 898 config ARCH_HAS_ELF_RANDOMIZE
 899         bool
 900         help
 901           An architecture supports choosing randomized locations for
 902           stack, mmap, brk, and ET_DYN. Defined functions:
 903           - arch_mmap_rnd()
 904           - arch_randomize_brk()
 905
 906 config HAVE_ARCH_MMAP_RND_BITS
 907         bool
 908         help
 909           An arch should select this symbol if it supports setting a variable
 910           number of bits for use in establishing the base address for mmap
 911           allocations, has MMU enabled and provides values for both:
 912           - ARCH_MMAP_RND_BITS_MIN
 913           - ARCH_MMAP_RND_BITS_MAX
 914
 915 config HAVE_EXIT_THREAD
 916         bool
 917         help
 918           An architecture implements exit_thread.
 919
 920 config ARCH_MMAP_RND_BITS_MIN
 921         int
 922
 923 config ARCH_MMAP_RND_BITS_MAX
 924         int
 925
 926 config ARCH_MMAP_RND_BITS_DEFAULT
 927         int
 928
 929 config ARCH_MMAP_RND_BITS
 930         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 931         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 932         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 933         default ARCH_MMAP_RND_BITS_MIN
 934         depends on HAVE_ARCH_MMAP_RND_BITS
 935         help
 936           This value can be used to select the number of bits to use to
 937           determine the random offset to the base address of vma regions
 938           resulting from mmap allocations. This value will be bounded
 939           by the architecture's minimum and maximum supported values.
 940
 941           This value can be changed after boot using the
 942           /proc/sys/vm/mmap_rnd_bits tunable
 943
 944 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 945         bool
 946         help
 947           An arch should select this symbol if it supports running applications
 948           in compatibility mode, supports setting a variable number of bits for
 949           use in establishing the base address for mmap allocations, has MMU
 950           enabled and provides values for both:
 951           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 952           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 953
 954 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 955         int
 956
 957 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 958         int
 959
 960 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 961         int
 962
 963 config ARCH_MMAP_RND_COMPAT_BITS
 964         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 965         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 966         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 967         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 968         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 969         help
 970           This value can be used to select the number of bits to use to
 971           determine the random offset to the base address of vma regions
 972           resulting from mmap allocations for compatible applications This
 973           value will be bounded by the architecture's minimum and maximum
 974           supported values.
 975
 976           This value can be changed after boot using the
 977           /proc/sys/vm/mmap_rnd_compat_bits tunable
 978
 979 config HAVE_ARCH_COMPAT_MMAP_BASES
 980         bool
 981         help
 982           This allows 64bit applications to invoke 32-bit mmap() syscall
 983           and vice-versa 32-bit applications to call 64-bit mmap().
 984           Required for applications doing different bitness syscalls.
 985
 986 # This allows to use a set of generic functions to determine mmap base
 987 # address by giving priority to top-down scheme only if the process
 988 # is not in legacy mode (compat task, unlimited stack size or
 989 # sysctl_legacy_va_layout).
 990 # Architecture that selects this option can provide its own version of:
 991 # - STACK_RND_MASK
 992 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 993         bool
 994         depends on MMU
 995         select ARCH_HAS_ELF_RANDOMIZE
 996
 997 config HAVE_STACK_VALIDATION
 998         bool
 999         help
1000           Architecture supports the 'objtool check' host tool command, which
1001           performs compile-time stack metadata validation.
1002
1003 config HAVE_RELIABLE_STACKTRACE
1004         bool
1005         help
1006           Architecture has either save_stack_trace_tsk_reliable() or
1007           arch_stack_walk_reliable() function which only returns a stack trace
1008           if it can guarantee the trace is reliable.
1009
1010 config HAVE_ARCH_HASH
1011         bool
1012         default n
1013         help
1014           If this is set, the architecture provides an <asm/hash.h>
1015           file which provides platform-specific implementations of some
1016           functions in <linux/hash.h> or fs/namei.c.
1017
1018 config HAVE_ARCH_NVRAM_OPS
1019         bool
1020
1021 config ISA_BUS_API
1022         def_bool ISA
1023
1024 #
1025 # ABI hall of shame
1026 #
1027 config CLONE_BACKWARDS
1028         bool
1029         help
1030           Architecture has tls passed as the 4th argument of clone(2),
1031           not the 5th one.
1032
1033 config CLONE_BACKWARDS2
1034         bool
1035         help
1036           Architecture has the first two arguments of clone(2) swapped.
1037
1038 config CLONE_BACKWARDS3
1039         bool
1040         help
1041           Architecture has tls passed as the 3rd argument of clone(2),
1042           not the 5th one.
1043
1044 config ODD_RT_SIGACTION
1045         bool
1046         help
1047           Architecture has unusual rt_sigaction(2) arguments
1048
1049 config OLD_SIGSUSPEND
1050         bool
1051         help
1052           Architecture has old sigsuspend(2) syscall, of one-argument variety
1053
1054 config OLD_SIGSUSPEND3
1055         bool
1056         help
1057           Even weirder antique ABI - three-argument sigsuspend(2)
1058
1059 config OLD_SIGACTION
1060         bool
1061         help
1062           Architecture has old sigaction(2) syscall.  Nope, not the same
1063           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1064           but fairly different variant of sigaction(2), thanks to OSF/1
1065           compatibility...
1066
1067 config COMPAT_OLD_SIGACTION
1068         bool
1069
1070 config COMPAT_32BIT_TIME
1071         bool "Provide system calls for 32-bit time_t"
1072         default !64BIT || COMPAT
1073         help
1074           This enables 32 bit time_t support in addition to 64 bit time_t support.
1075           This is relevant on all 32-bit architectures, and 64-bit architectures
1076           as part of compat syscall handling.
1077
1078 config ARCH_NO_PREEMPT
1079         bool
1080
1081 config ARCH_EPHEMERAL_INODES
1082         def_bool n
1083         help
1084           An arch should select this symbol if it doesn't keep track of inode
1085           instances on its own, but instead relies on something else (e.g. the
1086           host kernel for an UML kernel).
1087
1088 config ARCH_SUPPORTS_RT
1089         bool
1090
1091 config CPU_NO_EFFICIENT_FFS
1092         def_bool n
1093
1094 config HAVE_ARCH_VMAP_STACK
1095         def_bool n
1096         help
1097           An arch should select this symbol if it can support kernel stacks
1098           in vmalloc space.  This means:
1099
1100           - vmalloc space must be large enough to hold many kernel stacks.
1101             This may rule out many 32-bit architectures.
1102
1103           - Stacks in vmalloc space need to work reliably.  For example, if
1104             vmap page tables are created on demand, either this mechanism
1105             needs to work while the stack points to a virtual address with
1106             unpopulated page tables or arch code (switch_to() and switch_mm(),
1107             most likely) needs to ensure that the stack's page table entries
1108             are populated before running on a possibly unpopulated stack.
1109
1110           - If the stack overflows into a guard page, something reasonable
1111             should happen.  The definition of "reasonable" is flexible, but
1112             instantly rebooting without logging anything would be unfriendly.
1113
1114 config VMAP_STACK
1115         default y
1116         bool "Use a virtually-mapped stack"
1117         depends on HAVE_ARCH_VMAP_STACK
1118         depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1119         help
1120           Enable this if you want the use virtually-mapped kernel stacks
1121           with guard pages.  This causes kernel stack overflows to be
1122           caught immediately rather than causing difficult-to-diagnose
1123           corruption.
1124
1125           To use this with software KASAN modes, the architecture must support
1126           backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1127           must be enabled.
1128
1129 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1130         def_bool n
1131         help
1132           An arch should select this symbol if it can support kernel stack
1133           offset randomization with calls to add_random_kstack_offset()
1134           during syscall entry and choose_random_kstack_offset() during
1135           syscall exit. Careful removal of -fstack-protector-strong and
1136           -fstack-protector should also be applied to the entry code and
1137           closely examined, as the artificial stack bump looks like an array
1138           to the compiler, so it will attempt to add canary checks regardless
1139           of the static branch state.
1140
1141 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1142         bool "Randomize kernel stack offset on syscall entry"
1143         depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1144         depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1145         help
1146           The kernel stack offset can be randomized (after pt_regs) by
1147           roughly 5 bits of entropy, frustrating memory corruption
1148           attacks that depend on stack address determinism or
1149           cross-syscall address exposures. This feature is controlled
1150           by kernel boot param "randomize_kstack_offset=on/off", and this
1151           config chooses the default boot state.
1152
1153 config ARCH_OPTIONAL_KERNEL_RWX
1154         def_bool n
1155
1156 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1157         def_bool n
1158
1159 config ARCH_HAS_STRICT_KERNEL_RWX
1160         def_bool n
1161
1162 config STRICT_KERNEL_RWX
1163         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1164         depends on ARCH_HAS_STRICT_KERNEL_RWX
1165         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1166         help
1167           If this is set, kernel text and rodata memory will be made read-only,
1168           and non-text memory will be made non-executable. This provides
1169           protection against certain security exploits (e.g. executing the heap
1170           or modifying text)
1171
1172           These features are considered standard security practice these days.
1173           You should say Y here in almost all cases.
1174
1175 config ARCH_HAS_STRICT_MODULE_RWX
1176         def_bool n
1177
1178 config STRICT_MODULE_RWX
1179         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1180         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1181         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1182         help
1183           If this is set, module text and rodata memory will be made read-only,
1184           and non-text memory will be made non-executable. This provides
1185           protection against certain security exploits (e.g. writing to text)
1186
1187 # select if the architecture provides an asm/dma-direct.h header
1188 config ARCH_HAS_PHYS_TO_DMA
1189         bool
1190
1191 config HAVE_ARCH_COMPILER_H
1192         bool
1193         help
1194           An architecture can select this if it provides an
1195           asm/compiler.h header that should be included after
1196           linux/compiler-*.h in order to override macro definitions that those
1197           headers generally provide.
1198
1199 config HAVE_ARCH_PREL32_RELOCATIONS
1200         bool
1201         help
1202           May be selected by an architecture if it supports place-relative
1203           32-bit relocations, both in the toolchain and in the module loader,
1204           in which case relative references can be used in special sections
1205           for PCI fixup, initcalls etc which are only half the size on 64 bit
1206           architectures, and don't require runtime relocation on relocatable
1207           kernels.
1208
1209 config ARCH_USE_MEMREMAP_PROT
1210         bool
1211
1212 config LOCK_EVENT_COUNTS
1213         bool "Locking event counts collection"
1214         depends on DEBUG_FS
1215         help
1216           Enable light-weight counting of various locking related events
1217           in the system with minimal performance impact. This reduces
1218           the chance of application behavior change because of timing
1219           differences. The counts are reported via debugfs.
1220
1221 # Select if the architecture has support for applying RELR relocations.
1222 config ARCH_HAS_RELR
1223         bool
1224
1225 config RELR
1226         bool "Use RELR relocation packing"
1227         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1228         default y
1229         help
1230           Store the kernel's dynamic relocations in the RELR relocation packing
1231           format. Requires a compatible linker (LLD supports this feature), as
1232           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1233           are compatible).
1234
1235 config ARCH_HAS_MEM_ENCRYPT
1236         bool
1237
1238 config ARCH_HAS_CC_PLATFORM
1239         bool
1240
1241 config HAVE_SPARSE_SYSCALL_NR
1242        bool
1243        help
1244           An architecture should select this if its syscall numbering is sparse
1245           to save space. For example, MIPS architecture has a syscall array with
1246           entries at 4000, 5000 and 6000 locations. This option turns on syscall
1247           related optimizations for a given architecture.
1248
1249 config ARCH_HAS_VDSO_DATA
1250         bool
1251
1252 config HAVE_STATIC_CALL
1253         bool
1254
1255 config HAVE_STATIC_CALL_INLINE
1256         bool
1257         depends on HAVE_STATIC_CALL
1258
1259 config HAVE_PREEMPT_DYNAMIC
1260         bool
1261         depends on HAVE_STATIC_CALL
1262         depends on GENERIC_ENTRY
1263         help
1264            Select this if the architecture support boot time preempt setting
1265            on top of static calls. It is strongly advised to support inline
1266            static call to avoid any overhead.
1267
1268 config ARCH_WANT_LD_ORPHAN_WARN
1269         bool
1270         help
1271           An arch should select this symbol once all linker sections are explicitly
1272           included, size-asserted, or discarded in the linker scripts. This is
1273           important because we never want expected sections to be placed heuristically
1274           by the linker, since the locations of such sections can change between linker
1275           versions.
1276
1277 config HAVE_ARCH_PFN_VALID
1278         bool
1279
1280 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1281         bool
1282
1283 config ARCH_SPLIT_ARG64
1284         bool
1285         help
1286            If a 32-bit architecture requires 64-bit arguments to be split into
1287            pairs of 32-bit arguments, select this option.
1288
1289 config ARCH_HAS_ELFCORE_COMPAT
1290         bool
1291
1292 config ARCH_HAS_PARANOID_L1D_FLUSH
1293         bool
1294
1295 config DYNAMIC_SIGFRAME
1296         bool
1297
1298 source "kernel/gcov/Kconfig"
1299
1300 source "scripts/gcc-plugins/Kconfig"
1301
1302 endmenu