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 config TRACE_IRQFLAGS_NMI_SUPPORT
 204         bool
 205
 206 #
 207 # An arch should select this if it provides all these things:
 208 #
 209 #       task_pt_regs()          in asm/processor.h or asm/ptrace.h
 210 #       arch_has_single_step()  if there is hardware single-step support
 211 #       arch_has_block_step()   if there is hardware block-step support
 212 #       asm/syscall.h           supplying asm-generic/syscall.h interface
 213 #       linux/regset.h          user_regset interfaces
 214 #       CORE_DUMP_USE_REGSET    #define'd in linux/elf.h
 215 #       TIF_SYSCALL_TRACE       calls tracehook_report_syscall_{entry,exit}
 216 #       TIF_NOTIFY_RESUME       calls tracehook_notify_resume()
 217 #       signal delivery         calls tracehook_signal_handler()
 218 #
 219 config HAVE_ARCH_TRACEHOOK
 220         bool
 221
 222 config HAVE_DMA_CONTIGUOUS
 223         bool
 224
 225 config GENERIC_SMP_IDLE_THREAD
 226         bool
 227
 228 config GENERIC_IDLE_POLL_SETUP
 229         bool
 230
 231 config ARCH_HAS_FORTIFY_SOURCE
 232         bool
 233         help
 234           An architecture should select this when it can successfully
 235           build and run with CONFIG_FORTIFY_SOURCE.
 236
 237 #
 238 # Select if the arch provides a historic keepinit alias for the retain_initrd
 239 # command line option
 240 #
 241 config ARCH_HAS_KEEPINITRD
 242         bool
 243
 244 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
 245 config ARCH_HAS_SET_MEMORY
 246         bool
 247
 248 # Select if arch has all set_direct_map_invalid/default() functions
 249 config ARCH_HAS_SET_DIRECT_MAP
 250         bool
 251
 252 #
 253 # Select if the architecture provides the arch_dma_set_uncached symbol to
 254 # either provide an uncached segment alias for a DMA allocation, or
 255 # to remap the page tables in place.
 256 #
 257 config ARCH_HAS_DMA_SET_UNCACHED
 258         bool
 259
 260 #
 261 # Select if the architectures provides the arch_dma_clear_uncached symbol
 262 # to undo an in-place page table remap for uncached access.
 263 #
 264 config ARCH_HAS_DMA_CLEAR_UNCACHED
 265         bool
 266
 267 # Select if arch init_task must go in the __init_task_data section
 268 config ARCH_TASK_STRUCT_ON_STACK
 269         bool
 270
 271 # Select if arch has its private alloc_task_struct() function
 272 config ARCH_TASK_STRUCT_ALLOCATOR
 273         bool
 274
 275 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 276         bool
 277         depends on !ARCH_TASK_STRUCT_ALLOCATOR
 278         help
 279           An architecture should select this to provide hardened usercopy
 280           knowledge about what region of the thread_struct should be
 281           whitelisted for copying to userspace. Normally this is only the
 282           FPU registers. Specifically, arch_thread_struct_whitelist()
 283           should be implemented. Without this, the entire thread_struct
 284           field in task_struct will be left whitelisted.
 285
 286 # Select if arch has its private alloc_thread_stack() function
 287 config ARCH_THREAD_STACK_ALLOCATOR
 288         bool
 289
 290 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 291 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 292         bool
 293
 294 config ARCH_WANTS_NO_INSTR
 295         bool
 296         help
 297           An architecture should select this if the noinstr macro is being used on
 298           functions to denote that the toolchain should avoid instrumenting such
 299           functions and is required for correctness.
 300
 301 config ARCH_32BIT_OFF_T
 302         bool
 303         depends on !64BIT
 304         help
 305           All new 32-bit architectures should have 64-bit off_t type on
 306           userspace side which corresponds to the loff_t kernel type. This
 307           is the requirement for modern ABIs. Some existing architectures
 308           still support 32-bit off_t. This option is enabled for all such
 309           architectures explicitly.
 310
 311 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
 312 config ARCH_32BIT_USTAT_F_TINODE
 313         bool
 314
 315 config HAVE_ASM_MODVERSIONS
 316         bool
 317         help
 318           This symbol should be selected by an architecture if it provides
 319           <asm/asm-prototypes.h> to support the module versioning for symbols
 320           exported from assembly code.
 321
 322 config HAVE_REGS_AND_STACK_ACCESS_API
 323         bool
 324         help
 325           This symbol should be selected by an architecture if it supports
 326           the API needed to access registers and stack entries from pt_regs,
 327           declared in asm/ptrace.h
 328           For example the kprobes-based event tracer needs this API.
 329
 330 config HAVE_RSEQ
 331         bool
 332         depends on HAVE_REGS_AND_STACK_ACCESS_API
 333         help
 334           This symbol should be selected by an architecture if it
 335           supports an implementation of restartable sequences.
 336
 337 config HAVE_FUNCTION_ARG_ACCESS_API
 338         bool
 339         help
 340           This symbol should be selected by an architecture if it supports
 341           the API needed to access function arguments from pt_regs,
 342           declared in asm/ptrace.h
 343
 344 config HAVE_HW_BREAKPOINT
 345         bool
 346         depends on PERF_EVENTS
 347
 348 config HAVE_MIXED_BREAKPOINTS_REGS
 349         bool
 350         depends on HAVE_HW_BREAKPOINT
 351         help
 352           Depending on the arch implementation of hardware breakpoints,
 353           some of them have separate registers for data and instruction
 354           breakpoints addresses, others have mixed registers to store
 355           them but define the access type in a control register.
 356           Select this option if your arch implements breakpoints under the
 357           latter fashion.
 358
 359 config HAVE_USER_RETURN_NOTIFIER
 360         bool
 361
 362 config HAVE_PERF_EVENTS_NMI
 363         bool
 364         help
 365           System hardware can generate an NMI using the perf event
 366           subsystem.  Also has support for calculating CPU cycle events
 367           to determine how many clock cycles in a given period.
 368
 369 config HAVE_HARDLOCKUP_DETECTOR_PERF
 370         bool
 371         depends on HAVE_PERF_EVENTS_NMI
 372         help
 373           The arch chooses to use the generic perf-NMI-based hardlockup
 374           detector. Must define HAVE_PERF_EVENTS_NMI.
 375
 376 config HAVE_NMI_WATCHDOG
 377         depends on HAVE_NMI
 378         bool
 379         help
 380           The arch provides a low level NMI watchdog. It provides
 381           asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
 382
 383 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 384         bool
 385         select HAVE_NMI_WATCHDOG
 386         help
 387           The arch chooses to provide its own hardlockup detector, which is
 388           a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
 389           interfaces and parameters provided by hardlockup detector subsystem.
 390
 391 config HAVE_PERF_REGS
 392         bool
 393         help
 394           Support selective register dumps for perf events. This includes
 395           bit-mapping of each registers and a unique architecture id.
 396
 397 config HAVE_PERF_USER_STACK_DUMP
 398         bool
 399         help
 400           Support user stack dumps for perf event samples. This needs
 401           access to the user stack pointer which is not unified across
 402           architectures.
 403
 404 config HAVE_ARCH_JUMP_LABEL
 405         bool
 406
 407 config HAVE_ARCH_JUMP_LABEL_RELATIVE
 408         bool
 409
 410 config MMU_GATHER_TABLE_FREE
 411         bool
 412
 413 config MMU_GATHER_RCU_TABLE_FREE
 414         bool
 415         select MMU_GATHER_TABLE_FREE
 416
 417 config MMU_GATHER_PAGE_SIZE
 418         bool
 419
 420 config MMU_GATHER_NO_RANGE
 421         bool
 422
 423 config MMU_GATHER_NO_GATHER
 424         bool
 425         depends on MMU_GATHER_TABLE_FREE
 426
 427 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 428         bool
 429         help
 430           Temporary select until all architectures can be converted to have
 431           irqs disabled over activate_mm. Architectures that do IPI based TLB
 432           shootdowns should enable this.
 433
 434 config ARCH_HAVE_NMI_SAFE_CMPXCHG
 435         bool
 436
 437 config HAVE_ALIGNED_STRUCT_PAGE
 438         bool
 439         help
 440           This makes sure that struct pages are double word aligned and that
 441           e.g. the SLUB allocator can perform double word atomic operations
 442           on a struct page for better performance. However selecting this
 443           might increase the size of a struct page by a word.
 444
 445 config HAVE_CMPXCHG_LOCAL
 446         bool
 447
 448 config HAVE_CMPXCHG_DOUBLE
 449         bool
 450
 451 config ARCH_WEAK_RELEASE_ACQUIRE
 452         bool
 453
 454 config ARCH_WANT_IPC_PARSE_VERSION
 455         bool
 456
 457 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 458         bool
 459
 460 config ARCH_WANT_OLD_COMPAT_IPC
 461         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 462         bool
 463
 464 config HAVE_ARCH_SECCOMP
 465         bool
 466         help
 467           An arch should select this symbol to support seccomp mode 1 (the fixed
 468           syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
 469           and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
 470           - __NR_seccomp_read_32
 471           - __NR_seccomp_write_32
 472           - __NR_seccomp_exit_32
 473           - __NR_seccomp_sigreturn_32
 474
 475 config HAVE_ARCH_SECCOMP_FILTER
 476         bool
 477         select HAVE_ARCH_SECCOMP
 478         help
 479           An arch should select this symbol if it provides all of these things:
 480           - all the requirements for HAVE_ARCH_SECCOMP
 481           - syscall_get_arch()
 482           - syscall_get_arguments()
 483           - syscall_rollback()
 484           - syscall_set_return_value()
 485           - SIGSYS siginfo_t support
 486           - secure_computing is called from a ptrace_event()-safe context
 487           - secure_computing return value is checked and a return value of -1
 488             results in the system call being skipped immediately.
 489           - seccomp syscall wired up
 490           - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
 491             SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
 492             COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
 493
 494 config SECCOMP
 495         prompt "Enable seccomp to safely execute untrusted bytecode"
 496         def_bool y
 497         depends on HAVE_ARCH_SECCOMP
 498         help
 499           This kernel feature is useful for number crunching applications
 500           that may need to handle untrusted bytecode during their
 501           execution. By using pipes or other transports made available
 502           to the process as file descriptors supporting the read/write
 503           syscalls, it's possible to isolate those applications in their
 504           own address space using seccomp. Once seccomp is enabled via
 505           prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
 506           disabled and the task is only allowed to execute a few safe
 507           syscalls defined by each seccomp mode.
 508
 509           If unsure, say Y.
 510
 511 config SECCOMP_FILTER
 512         def_bool y
 513         depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
 514         help
 515           Enable tasks to build secure computing environments defined
 516           in terms of Berkeley Packet Filter programs which implement
 517           task-defined system call filtering polices.
 518
 519           See Documentation/userspace-api/seccomp_filter.rst for details.
 520
 521 config SECCOMP_CACHE_DEBUG
 522         bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
 523         depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
 524         depends on PROC_FS
 525         help
 526           This enables the /proc/pid/seccomp_cache interface to monitor
 527           seccomp cache data. The file format is subject to change. Reading
 528           the file requires CAP_SYS_ADMIN.
 529
 530           This option is for debugging only. Enabling presents the risk that
 531           an adversary may be able to infer the seccomp filter logic.
 532
 533           If unsure, say N.
 534
 535 config HAVE_ARCH_STACKLEAK
 536         bool
 537         help
 538           An architecture should select this if it has the code which
 539           fills the used part of the kernel stack with the STACKLEAK_POISON
 540           value before returning from system calls.
 541
 542 config HAVE_STACKPROTECTOR
 543         bool
 544         help
 545           An arch should select this symbol if:
 546           - it has implemented a stack canary (e.g. __stack_chk_guard)
 547
 548 config STACKPROTECTOR
 549         bool "Stack Protector buffer overflow detection"
 550         depends on HAVE_STACKPROTECTOR
 551         depends on $(cc-option,-fstack-protector)
 552         default y
 553         help
 554           This option turns on the "stack-protector" GCC feature. This
 555           feature puts, at the beginning of functions, a canary value on
 556           the stack just before the return address, and validates
 557           the value just before actually returning.  Stack based buffer
 558           overflows (that need to overwrite this return address) now also
 559           overwrite the canary, which gets detected and the attack is then
 560           neutralized via a kernel panic.
 561
 562           Functions will have the stack-protector canary logic added if they
 563           have an 8-byte or larger character array on the stack.
 564
 565           This feature requires gcc version 4.2 or above, or a distribution
 566           gcc with the feature backported ("-fstack-protector").
 567
 568           On an x86 "defconfig" build, this feature adds canary checks to
 569           about 3% of all kernel functions, which increases kernel code size
 570           by about 0.3%.
 571
 572 config STACKPROTECTOR_STRONG
 573         bool "Strong Stack Protector"
 574         depends on STACKPROTECTOR
 575         depends on $(cc-option,-fstack-protector-strong)
 576         default y
 577         help
 578           Functions will have the stack-protector canary logic added in any
 579           of the following conditions:
 580
 581           - local variable's address used as part of the right hand side of an
 582             assignment or function argument
 583           - local variable is an array (or union containing an array),
 584             regardless of array type or length
 585           - uses register local variables
 586
 587           This feature requires gcc version 4.9 or above, or a distribution
 588           gcc with the feature backported ("-fstack-protector-strong").
 589
 590           On an x86 "defconfig" build, this feature adds canary checks to
 591           about 20% of all kernel functions, which increases the kernel code
 592           size by about 2%.
 593
 594 config ARCH_SUPPORTS_SHADOW_CALL_STACK
 595         bool
 596         help
 597           An architecture should select this if it supports Clang's Shadow
 598           Call Stack and implements runtime support for shadow stack
 599           switching.
 600
 601 config SHADOW_CALL_STACK
 602         bool "Clang Shadow Call Stack"
 603         depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
 604         depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
 605         help
 606           This option enables Clang's Shadow Call Stack, which uses a
 607           shadow stack to protect function return addresses from being
 608           overwritten by an attacker. More information can be found in
 609           Clang's documentation:
 610
 611             https://clang.llvm.org/docs/ShadowCallStack.html
 612
 613           Note that security guarantees in the kernel differ from the
 614           ones documented for user space. The kernel must store addresses
 615           of shadow stacks in memory, which means an attacker capable of
 616           reading and writing arbitrary memory may be able to locate them
 617           and hijack control flow by modifying the stacks.
 618
 619 config LTO
 620         bool
 621         help
 622           Selected if the kernel will be built using the compiler's LTO feature.
 623
 624 config LTO_CLANG
 625         bool
 626         select LTO
 627         help
 628           Selected if the kernel will be built using Clang's LTO feature.
 629
 630 config ARCH_SUPPORTS_LTO_CLANG
 631         bool
 632         help
 633           An architecture should select this option if it supports:
 634           - compiling with Clang,
 635           - compiling inline assembly with Clang's integrated assembler,
 636           - and linking with LLD.
 637
 638 config ARCH_SUPPORTS_LTO_CLANG_THIN
 639         bool
 640         help
 641           An architecture should select this option if it can support Clang's
 642           ThinLTO mode.
 643
 644 config HAS_LTO_CLANG
 645         def_bool y
 646         # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
 647         depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
 648         depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 649         depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 650         depends on ARCH_SUPPORTS_LTO_CLANG
 651         depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
 652         depends on !KASAN || KASAN_HW_TAGS
 653         depends on !GCOV_KERNEL
 654         help
 655           The compiler and Kconfig options support building with Clang's
 656           LTO.
 657
 658 choice
 659         prompt "Link Time Optimization (LTO)"
 660         default LTO_NONE
 661         help
 662           This option enables Link Time Optimization (LTO), which allows the
 663           compiler to optimize binaries globally.
 664
 665           If unsure, select LTO_NONE. Note that LTO is very resource-intensive
 666           so it's disabled by default.
 667
 668 config LTO_NONE
 669         bool "None"
 670         help
 671           Build the kernel normally, without Link Time Optimization (LTO).
 672
 673 config LTO_CLANG_FULL
 674         bool "Clang Full LTO (EXPERIMENTAL)"
 675         depends on HAS_LTO_CLANG
 676         depends on !COMPILE_TEST
 677         select LTO_CLANG
 678         help
 679           This option enables Clang's full Link Time Optimization (LTO), which
 680           allows the compiler to optimize the kernel globally. If you enable
 681           this option, the compiler generates LLVM bitcode instead of ELF
 682           object files, and the actual compilation from bitcode happens at
 683           the LTO link step, which may take several minutes depending on the
 684           kernel configuration. More information can be found from LLVM's
 685           documentation:
 686
 687             https://llvm.org/docs/LinkTimeOptimization.html
 688
 689           During link time, this option can use a large amount of RAM, and
 690           may take much longer than the ThinLTO option.
 691
 692 config LTO_CLANG_THIN
 693         bool "Clang ThinLTO (EXPERIMENTAL)"
 694         depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
 695         select LTO_CLANG
 696         help
 697           This option enables Clang's ThinLTO, which allows for parallel
 698           optimization and faster incremental compiles compared to the
 699           CONFIG_LTO_CLANG_FULL option. More information can be found
 700           from Clang's documentation:
 701
 702             https://clang.llvm.org/docs/ThinLTO.html
 703
 704           If unsure, say Y.
 705 endchoice
 706
 707 config ARCH_SUPPORTS_CFI_CLANG
 708         bool
 709         help
 710           An architecture should select this option if it can support Clang's
 711           Control-Flow Integrity (CFI) checking.
 712
 713 config CFI_CLANG
 714         bool "Use Clang's Control Flow Integrity (CFI)"
 715         depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG
 716         # Clang >= 12:
 717         # - https://bugs.llvm.org/show_bug.cgi?id=46258
 718         # - https://bugs.llvm.org/show_bug.cgi?id=47479
 719         depends on CLANG_VERSION >= 120000
 720         select KALLSYMS
 721         help
 722           This option enables Clang’s forward-edge Control Flow Integrity
 723           (CFI) checking, where the compiler injects a runtime check to each
 724           indirect function call to ensure the target is a valid function with
 725           the correct static type. This restricts possible call targets and
 726           makes it more difficult for an attacker to exploit bugs that allow
 727           the modification of stored function pointers. More information can be
 728           found from Clang's documentation:
 729
 730             https://clang.llvm.org/docs/ControlFlowIntegrity.html
 731
 732 config CFI_CLANG_SHADOW
 733         bool "Use CFI shadow to speed up cross-module checks"
 734         default y
 735         depends on CFI_CLANG && MODULES
 736         help
 737           If you select this option, the kernel builds a fast look-up table of
 738           CFI check functions in loaded modules to reduce performance overhead.
 739
 740           If unsure, say Y.
 741
 742 config CFI_PERMISSIVE
 743         bool "Use CFI in permissive mode"
 744         depends on CFI_CLANG
 745         help
 746           When selected, Control Flow Integrity (CFI) violations result in a
 747           warning instead of a kernel panic. This option should only be used
 748           for finding indirect call type mismatches during development.
 749
 750           If unsure, say N.
 751
 752 config HAVE_ARCH_WITHIN_STACK_FRAMES
 753         bool
 754         help
 755           An architecture should select this if it can walk the kernel stack
 756           frames to determine if an object is part of either the arguments
 757           or local variables (i.e. that it excludes saved return addresses,
 758           and similar) by implementing an inline arch_within_stack_frames(),
 759           which is used by CONFIG_HARDENED_USERCOPY.
 760
 761 config HAVE_CONTEXT_TRACKING
 762         bool
 763         help
 764           Provide kernel/user boundaries probes necessary for subsystems
 765           that need it, such as userspace RCU extended quiescent state.
 766           Syscalls need to be wrapped inside user_exit()-user_enter(), either
 767           optimized behind static key or through the slow path using TIF_NOHZ
 768           flag. Exceptions handlers must be wrapped as well. Irqs are already
 769           protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
 770           handling on irq exit still need to be protected.
 771
 772 config HAVE_CONTEXT_TRACKING_OFFSTACK
 773         bool
 774         help
 775           Architecture neither relies on exception_enter()/exception_exit()
 776           nor on schedule_user(). Also preempt_schedule_notrace() and
 777           preempt_schedule_irq() can't be called in a preemptible section
 778           while context tracking is CONTEXT_USER. This feature reflects a sane
 779           entry implementation where the following requirements are met on
 780           critical entry code, ie: before user_exit() or after user_enter():
 781
 782           - Critical entry code isn't preemptible (or better yet:
 783             not interruptible).
 784           - No use of RCU read side critical sections, unless rcu_nmi_enter()
 785             got called.
 786           - No use of instrumentation, unless instrumentation_begin() got
 787             called.
 788
 789 config HAVE_TIF_NOHZ
 790         bool
 791         help
 792           Arch relies on TIF_NOHZ and syscall slow path to implement context
 793           tracking calls to user_enter()/user_exit().
 794
 795 config HAVE_VIRT_CPU_ACCOUNTING
 796         bool
 797
 798 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
 799         bool
 800         help
 801           Architecture has its own way to account idle CPU time and therefore
 802           doesn't implement vtime_account_idle().
 803
 804 config ARCH_HAS_SCALED_CPUTIME
 805         bool
 806
 807 config HAVE_VIRT_CPU_ACCOUNTING_GEN
 808         bool
 809         default y if 64BIT
 810         help
 811           With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
 812           Before enabling this option, arch code must be audited
 813           to ensure there are no races in concurrent read/write of
 814           cputime_t. For example, reading/writing 64-bit cputime_t on
 815           some 32-bit arches may require multiple accesses, so proper
 816           locking is needed to protect against concurrent accesses.
 817
 818 config HAVE_IRQ_TIME_ACCOUNTING
 819         bool
 820         help
 821           Archs need to ensure they use a high enough resolution clock to
 822           support irq time accounting and then call enable_sched_clock_irqtime().
 823
 824 config HAVE_MOVE_PUD
 825         bool
 826         help
 827           Architectures that select this are able to move page tables at the
 828           PUD level. If there are only 3 page table levels, the move effectively
 829           happens at the PGD level.
 830
 831 config HAVE_MOVE_PMD
 832         bool
 833         help
 834           Archs that select this are able to move page tables at the PMD level.
 835
 836 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
 837         bool
 838
 839 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 840         bool
 841
 842 config HAVE_ARCH_HUGE_VMAP
 843         bool
 844
 845 #
 846 #  Archs that select this would be capable of PMD-sized vmaps (i.e.,
 847 #  arch_vmap_pmd_supported() returns true), and they must make no assumptions
 848 #  that vmalloc memory is mapped with PAGE_SIZE ptes. The VM_NO_HUGE_VMAP flag
 849 #  can be used to prohibit arch-specific allocations from using hugepages to
 850 #  help with this (e.g., modules may require it).
 851 #
 852 config HAVE_ARCH_HUGE_VMALLOC
 853         depends on HAVE_ARCH_HUGE_VMAP
 854         bool
 855
 856 config ARCH_WANT_HUGE_PMD_SHARE
 857         bool
 858
 859 config HAVE_ARCH_SOFT_DIRTY
 860         bool
 861
 862 config HAVE_MOD_ARCH_SPECIFIC
 863         bool
 864         help
 865           The arch uses struct mod_arch_specific to store data.  Many arches
 866           just need a simple module loader without arch specific data - those
 867           should not enable this.
 868
 869 config MODULES_USE_ELF_RELA
 870         bool
 871         help
 872           Modules only use ELF RELA relocations.  Modules with ELF REL
 873           relocations will give an error.
 874
 875 config MODULES_USE_ELF_REL
 876         bool
 877         help
 878           Modules only use ELF REL relocations.  Modules with ELF RELA
 879           relocations will give an error.
 880
 881 config HAVE_IRQ_EXIT_ON_IRQ_STACK
 882         bool
 883         help
 884           Architecture doesn't only execute the irq handler on the irq stack
 885           but also irq_exit(). This way we can process softirqs on this irq
 886           stack instead of switching to a new one when we call __do_softirq()
 887           in the end of an hardirq.
 888           This spares a stack switch and improves cache usage on softirq
 889           processing.
 890
 891 config HAVE_SOFTIRQ_ON_OWN_STACK
 892         bool
 893         help
 894           Architecture provides a function to run __do_softirq() on a
 895           separate stack.
 896
 897 config PGTABLE_LEVELS
 898         int
 899         default 2
 900
 901 config ARCH_HAS_ELF_RANDOMIZE
 902         bool
 903         help
 904           An architecture supports choosing randomized locations for
 905           stack, mmap, brk, and ET_DYN. Defined functions:
 906           - arch_mmap_rnd()
 907           - arch_randomize_brk()
 908
 909 config HAVE_ARCH_MMAP_RND_BITS
 910         bool
 911         help
 912           An arch should select this symbol if it supports setting a variable
 913           number of bits for use in establishing the base address for mmap
 914           allocations, has MMU enabled and provides values for both:
 915           - ARCH_MMAP_RND_BITS_MIN
 916           - ARCH_MMAP_RND_BITS_MAX
 917
 918 config HAVE_EXIT_THREAD
 919         bool
 920         help
 921           An architecture implements exit_thread.
 922
 923 config ARCH_MMAP_RND_BITS_MIN
 924         int
 925
 926 config ARCH_MMAP_RND_BITS_MAX
 927         int
 928
 929 config ARCH_MMAP_RND_BITS_DEFAULT
 930         int
 931
 932 config ARCH_MMAP_RND_BITS
 933         int "Number of bits to use for ASLR of mmap base address" if EXPERT
 934         range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
 935         default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
 936         default ARCH_MMAP_RND_BITS_MIN
 937         depends on HAVE_ARCH_MMAP_RND_BITS
 938         help
 939           This value can be used to select the number of bits to use to
 940           determine the random offset to the base address of vma regions
 941           resulting from mmap allocations. This value will be bounded
 942           by the architecture's minimum and maximum supported values.
 943
 944           This value can be changed after boot using the
 945           /proc/sys/vm/mmap_rnd_bits tunable
 946
 947 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
 948         bool
 949         help
 950           An arch should select this symbol if it supports running applications
 951           in compatibility mode, supports setting a variable number of bits for
 952           use in establishing the base address for mmap allocations, has MMU
 953           enabled and provides values for both:
 954           - ARCH_MMAP_RND_COMPAT_BITS_MIN
 955           - ARCH_MMAP_RND_COMPAT_BITS_MAX
 956
 957 config ARCH_MMAP_RND_COMPAT_BITS_MIN
 958         int
 959
 960 config ARCH_MMAP_RND_COMPAT_BITS_MAX
 961         int
 962
 963 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 964         int
 965
 966 config ARCH_MMAP_RND_COMPAT_BITS
 967         int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
 968         range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
 969         default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
 970         default ARCH_MMAP_RND_COMPAT_BITS_MIN
 971         depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
 972         help
 973           This value can be used to select the number of bits to use to
 974           determine the random offset to the base address of vma regions
 975           resulting from mmap allocations for compatible applications This
 976           value will be bounded by the architecture's minimum and maximum
 977           supported values.
 978
 979           This value can be changed after boot using the
 980           /proc/sys/vm/mmap_rnd_compat_bits tunable
 981
 982 config HAVE_ARCH_COMPAT_MMAP_BASES
 983         bool
 984         help
 985           This allows 64bit applications to invoke 32-bit mmap() syscall
 986           and vice-versa 32-bit applications to call 64-bit mmap().
 987           Required for applications doing different bitness syscalls.
 988
 989 # This allows to use a set of generic functions to determine mmap base
 990 # address by giving priority to top-down scheme only if the process
 991 # is not in legacy mode (compat task, unlimited stack size or
 992 # sysctl_legacy_va_layout).
 993 # Architecture that selects this option can provide its own version of:
 994 # - STACK_RND_MASK
 995 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 996         bool
 997         depends on MMU
 998         select ARCH_HAS_ELF_RANDOMIZE
 999
1000 config HAVE_STACK_VALIDATION
1001         bool
1002         help
1003           Architecture supports the 'objtool check' host tool command, which
1004           performs compile-time stack metadata validation.
1005
1006 config HAVE_RELIABLE_STACKTRACE
1007         bool
1008         help
1009           Architecture has either save_stack_trace_tsk_reliable() or
1010           arch_stack_walk_reliable() function which only returns a stack trace
1011           if it can guarantee the trace is reliable.
1012
1013 config HAVE_ARCH_HASH
1014         bool
1015         default n
1016         help
1017           If this is set, the architecture provides an <asm/hash.h>
1018           file which provides platform-specific implementations of some
1019           functions in <linux/hash.h> or fs/namei.c.
1020
1021 config HAVE_ARCH_NVRAM_OPS
1022         bool
1023
1024 config ISA_BUS_API
1025         def_bool ISA
1026
1027 #
1028 # ABI hall of shame
1029 #
1030 config CLONE_BACKWARDS
1031         bool
1032         help
1033           Architecture has tls passed as the 4th argument of clone(2),
1034           not the 5th one.
1035
1036 config CLONE_BACKWARDS2
1037         bool
1038         help
1039           Architecture has the first two arguments of clone(2) swapped.
1040
1041 config CLONE_BACKWARDS3
1042         bool
1043         help
1044           Architecture has tls passed as the 3rd argument of clone(2),
1045           not the 5th one.
1046
1047 config ODD_RT_SIGACTION
1048         bool
1049         help
1050           Architecture has unusual rt_sigaction(2) arguments
1051
1052 config OLD_SIGSUSPEND
1053         bool
1054         help
1055           Architecture has old sigsuspend(2) syscall, of one-argument variety
1056
1057 config OLD_SIGSUSPEND3
1058         bool
1059         help
1060           Even weirder antique ABI - three-argument sigsuspend(2)
1061
1062 config OLD_SIGACTION
1063         bool
1064         help
1065           Architecture has old sigaction(2) syscall.  Nope, not the same
1066           as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1067           but fairly different variant of sigaction(2), thanks to OSF/1
1068           compatibility...
1069
1070 config COMPAT_OLD_SIGACTION
1071         bool
1072
1073 config COMPAT_32BIT_TIME
1074         bool "Provide system calls for 32-bit time_t"
1075         default !64BIT || COMPAT
1076         help
1077           This enables 32 bit time_t support in addition to 64 bit time_t support.
1078           This is relevant on all 32-bit architectures, and 64-bit architectures
1079           as part of compat syscall handling.
1080
1081 config ARCH_NO_PREEMPT
1082         bool
1083
1084 config ARCH_EPHEMERAL_INODES
1085         def_bool n
1086         help
1087           An arch should select this symbol if it doesn't keep track of inode
1088           instances on its own, but instead relies on something else (e.g. the
1089           host kernel for an UML kernel).
1090
1091 config ARCH_SUPPORTS_RT
1092         bool
1093
1094 config CPU_NO_EFFICIENT_FFS
1095         def_bool n
1096
1097 config HAVE_ARCH_VMAP_STACK
1098         def_bool n
1099         help
1100           An arch should select this symbol if it can support kernel stacks
1101           in vmalloc space.  This means:
1102
1103           - vmalloc space must be large enough to hold many kernel stacks.
1104             This may rule out many 32-bit architectures.
1105
1106           - Stacks in vmalloc space need to work reliably.  For example, if
1107             vmap page tables are created on demand, either this mechanism
1108             needs to work while the stack points to a virtual address with
1109             unpopulated page tables or arch code (switch_to() and switch_mm(),
1110             most likely) needs to ensure that the stack's page table entries
1111             are populated before running on a possibly unpopulated stack.
1112
1113           - If the stack overflows into a guard page, something reasonable
1114             should happen.  The definition of "reasonable" is flexible, but
1115             instantly rebooting without logging anything would be unfriendly.
1116
1117 config VMAP_STACK
1118         default y
1119         bool "Use a virtually-mapped stack"
1120         depends on HAVE_ARCH_VMAP_STACK
1121         depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1122         help
1123           Enable this if you want the use virtually-mapped kernel stacks
1124           with guard pages.  This causes kernel stack overflows to be
1125           caught immediately rather than causing difficult-to-diagnose
1126           corruption.
1127
1128           To use this with software KASAN modes, the architecture must support
1129           backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1130           must be enabled.
1131
1132 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1133         def_bool n
1134         help
1135           An arch should select this symbol if it can support kernel stack
1136           offset randomization with calls to add_random_kstack_offset()
1137           during syscall entry and choose_random_kstack_offset() during
1138           syscall exit. Careful removal of -fstack-protector-strong and
1139           -fstack-protector should also be applied to the entry code and
1140           closely examined, as the artificial stack bump looks like an array
1141           to the compiler, so it will attempt to add canary checks regardless
1142           of the static branch state.
1143
1144 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1145         bool "Randomize kernel stack offset on syscall entry"
1146         depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1147         depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1148         help
1149           The kernel stack offset can be randomized (after pt_regs) by
1150           roughly 5 bits of entropy, frustrating memory corruption
1151           attacks that depend on stack address determinism or
1152           cross-syscall address exposures. This feature is controlled
1153           by kernel boot param "randomize_kstack_offset=on/off", and this
1154           config chooses the default boot state.
1155
1156 config ARCH_OPTIONAL_KERNEL_RWX
1157         def_bool n
1158
1159 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1160         def_bool n
1161
1162 config ARCH_HAS_STRICT_KERNEL_RWX
1163         def_bool n
1164
1165 config STRICT_KERNEL_RWX
1166         bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1167         depends on ARCH_HAS_STRICT_KERNEL_RWX
1168         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1169         help
1170           If this is set, kernel text and rodata memory will be made read-only,
1171           and non-text memory will be made non-executable. This provides
1172           protection against certain security exploits (e.g. executing the heap
1173           or modifying text)
1174
1175           These features are considered standard security practice these days.
1176           You should say Y here in almost all cases.
1177
1178 config ARCH_HAS_STRICT_MODULE_RWX
1179         def_bool n
1180
1181 config STRICT_MODULE_RWX
1182         bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1183         depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1184         default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1185         help
1186           If this is set, module text and rodata memory will be made read-only,
1187           and non-text memory will be made non-executable. This provides
1188           protection against certain security exploits (e.g. writing to text)
1189
1190 # select if the architecture provides an asm/dma-direct.h header
1191 config ARCH_HAS_PHYS_TO_DMA
1192         bool
1193
1194 config HAVE_ARCH_COMPILER_H
1195         bool
1196         help
1197           An architecture can select this if it provides an
1198           asm/compiler.h header that should be included after
1199           linux/compiler-*.h in order to override macro definitions that those
1200           headers generally provide.
1201
1202 config HAVE_ARCH_PREL32_RELOCATIONS
1203         bool
1204         help
1205           May be selected by an architecture if it supports place-relative
1206           32-bit relocations, both in the toolchain and in the module loader,
1207           in which case relative references can be used in special sections
1208           for PCI fixup, initcalls etc which are only half the size on 64 bit
1209           architectures, and don't require runtime relocation on relocatable
1210           kernels.
1211
1212 config ARCH_USE_MEMREMAP_PROT
1213         bool
1214
1215 config LOCK_EVENT_COUNTS
1216         bool "Locking event counts collection"
1217         depends on DEBUG_FS
1218         help
1219           Enable light-weight counting of various locking related events
1220           in the system with minimal performance impact. This reduces
1221           the chance of application behavior change because of timing
1222           differences. The counts are reported via debugfs.
1223
1224 # Select if the architecture has support for applying RELR relocations.
1225 config ARCH_HAS_RELR
1226         bool
1227
1228 config RELR
1229         bool "Use RELR relocation packing"
1230         depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1231         default y
1232         help
1233           Store the kernel's dynamic relocations in the RELR relocation packing
1234           format. Requires a compatible linker (LLD supports this feature), as
1235           well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1236           are compatible).
1237
1238 config ARCH_HAS_MEM_ENCRYPT
1239         bool
1240
1241 config ARCH_HAS_CC_PLATFORM
1242         bool
1243
1244 config HAVE_SPARSE_SYSCALL_NR
1245        bool
1246        help
1247           An architecture should select this if its syscall numbering is sparse
1248           to save space. For example, MIPS architecture has a syscall array with
1249           entries at 4000, 5000 and 6000 locations. This option turns on syscall
1250           related optimizations for a given architecture.
1251
1252 config ARCH_HAS_VDSO_DATA
1253         bool
1254
1255 config HAVE_STATIC_CALL
1256         bool
1257
1258 config HAVE_STATIC_CALL_INLINE
1259         bool
1260         depends on HAVE_STATIC_CALL
1261
1262 config HAVE_PREEMPT_DYNAMIC
1263         bool
1264         depends on HAVE_STATIC_CALL
1265         depends on GENERIC_ENTRY
1266         help
1267            Select this if the architecture support boot time preempt setting
1268            on top of static calls. It is strongly advised to support inline
1269            static call to avoid any overhead.
1270
1271 config ARCH_WANT_LD_ORPHAN_WARN
1272         bool
1273         help
1274           An arch should select this symbol once all linker sections are explicitly
1275           included, size-asserted, or discarded in the linker scripts. This is
1276           important because we never want expected sections to be placed heuristically
1277           by the linker, since the locations of such sections can change between linker
1278           versions.
1279
1280 config HAVE_ARCH_PFN_VALID
1281         bool
1282
1283 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1284         bool
1285
1286 config ARCH_SPLIT_ARG64
1287         bool
1288         help
1289            If a 32-bit architecture requires 64-bit arguments to be split into
1290            pairs of 32-bit arguments, select this option.
1291
1292 config ARCH_HAS_ELFCORE_COMPAT
1293         bool
1294
1295 config ARCH_HAS_PARANOID_L1D_FLUSH
1296         bool
1297
1298 config DYNAMIC_SIGFRAME
1299         bool
1300
1301 source "kernel/gcov/Kconfig"
1302
1303 source "scripts/gcc-plugins/Kconfig"
1304
1305 endmenu