1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6# 7# Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can 8# override the default values in this file. 9# 10source "arch/$(SRCARCH)/Kconfig" 11 12menu "General architecture-dependent options" 13 14config CRASH_CORE 15 bool 16 17config KEXEC_CORE 18 select CRASH_CORE 19 bool 20 21config KEXEC_ELF 22 bool 23 24config HAVE_IMA_KEXEC 25 bool 26 27config SET_FS 28 bool 29 30config HOTPLUG_SMT 31 bool 32 33config GENERIC_ENTRY 34 bool 35 36config OPROFILE 37 tristate "OProfile system profiling" 38 depends on PROFILING 39 depends on HAVE_OPROFILE 40 select RING_BUFFER 41 select RING_BUFFER_ALLOW_SWAP 42 help 43 OProfile is a profiling system capable of profiling the 44 whole system, include the kernel, kernel modules, libraries, 45 and applications. 46 47 If unsure, say N. 48 49config OPROFILE_EVENT_MULTIPLEX 50 bool "OProfile multiplexing support (EXPERIMENTAL)" 51 default n 52 depends on OPROFILE && X86 53 help 54 The number of hardware counters is limited. The multiplexing 55 feature enables OProfile to gather more events than counters 56 are provided by the hardware. This is realized by switching 57 between events at a user specified time interval. 58 59 If unsure, say N. 60 61config HAVE_OPROFILE 62 bool 63 64config OPROFILE_NMI_TIMER 65 def_bool y 66 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 67 68config KPROBES 69 bool "Kprobes" 70 depends on MODULES 71 depends on HAVE_KPROBES 72 select KALLSYMS 73 help 74 Kprobes allows you to trap at almost any kernel address and 75 execute a callback function. register_kprobe() establishes 76 a probepoint and specifies the callback. Kprobes is useful 77 for kernel debugging, non-intrusive instrumentation and testing. 78 If in doubt, say "N". 79 80config JUMP_LABEL 81 bool "Optimize very unlikely/likely branches" 82 depends on HAVE_ARCH_JUMP_LABEL 83 depends on CC_HAS_ASM_GOTO 84 help 85 This option enables a transparent branch optimization that 86 makes certain almost-always-true or almost-always-false branch 87 conditions even cheaper to execute within the kernel. 88 89 Certain performance-sensitive kernel code, such as trace points, 90 scheduler functionality, networking code and KVM have such 91 branches and include support for this optimization technique. 92 93 If it is detected that the compiler has support for "asm goto", 94 the kernel will compile such branches with just a nop 95 instruction. When the condition flag is toggled to true, the 96 nop will be converted to a jump instruction to execute the 97 conditional block of instructions. 98 99 This technique lowers overhead and stress on the branch prediction 100 of the processor and generally makes the kernel faster. The update 101 of the condition is slower, but those are always very rare. 102 103 ( On 32-bit x86, the necessary options added to the compiler 104 flags may increase the size of the kernel slightly. ) 105 106config STATIC_KEYS_SELFTEST 107 bool "Static key selftest" 108 depends on JUMP_LABEL 109 help 110 Boot time self-test of the branch patching code. 111 112config STATIC_CALL_SELFTEST 113 bool "Static call selftest" 114 depends on HAVE_STATIC_CALL 115 help 116 Boot time self-test of the call patching code. 117 118config OPTPROBES 119 def_bool y 120 depends on KPROBES && HAVE_OPTPROBES 121 select TASKS_RCU if PREEMPTION 122 123config KPROBES_ON_FTRACE 124 def_bool y 125 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 126 depends on DYNAMIC_FTRACE_WITH_REGS 127 help 128 If function tracer is enabled and the arch supports full 129 passing of pt_regs to function tracing, then kprobes can 130 optimize on top of function tracing. 131 132config UPROBES 133 def_bool n 134 depends on ARCH_SUPPORTS_UPROBES 135 help 136 Uprobes is the user-space counterpart to kprobes: they 137 enable instrumentation applications (such as 'perf probe') 138 to establish unintrusive probes in user-space binaries and 139 libraries, by executing handler functions when the probes 140 are hit by user-space applications. 141 142 ( These probes come in the form of single-byte breakpoints, 143 managed by the kernel and kept transparent to the probed 144 application. ) 145 146config HAVE_64BIT_ALIGNED_ACCESS 147 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 148 help 149 Some architectures require 64 bit accesses to be 64 bit 150 aligned, which also requires structs containing 64 bit values 151 to be 64 bit aligned too. This includes some 32 bit 152 architectures which can do 64 bit accesses, as well as 64 bit 153 architectures without unaligned access. 154 155 This symbol should be selected by an architecture if 64 bit 156 accesses are required to be 64 bit aligned in this way even 157 though it is not a 64 bit architecture. 158 159 See Documentation/unaligned-memory-access.txt for more 160 information on the topic of unaligned memory accesses. 161 162config HAVE_EFFICIENT_UNALIGNED_ACCESS 163 bool 164 help 165 Some architectures are unable to perform unaligned accesses 166 without the use of get_unaligned/put_unaligned. Others are 167 unable to perform such accesses efficiently (e.g. trap on 168 unaligned access and require fixing it up in the exception 169 handler.) 170 171 This symbol should be selected by an architecture if it can 172 perform unaligned accesses efficiently to allow different 173 code paths to be selected for these cases. Some network 174 drivers, for example, could opt to not fix up alignment 175 problems with received packets if doing so would not help 176 much. 177 178 See Documentation/core-api/unaligned-memory-access.rst for more 179 information on the topic of unaligned memory accesses. 180 181config ARCH_USE_BUILTIN_BSWAP 182 bool 183 help 184 Modern versions of GCC (since 4.4) have builtin functions 185 for handling byte-swapping. Using these, instead of the old 186 inline assembler that the architecture code provides in the 187 __arch_bswapXX() macros, allows the compiler to see what's 188 happening and offers more opportunity for optimisation. In 189 particular, the compiler will be able to combine the byteswap 190 with a nearby load or store and use load-and-swap or 191 store-and-swap instructions if the architecture has them. It 192 should almost *never* result in code which is worse than the 193 hand-coded assembler in <asm/swab.h>. But just in case it 194 does, the use of the builtins is optional. 195 196 Any architecture with load-and-swap or store-and-swap 197 instructions should set this. And it shouldn't hurt to set it 198 on architectures that don't have such instructions. 199 200config KRETPROBES 201 def_bool y 202 depends on KPROBES && HAVE_KRETPROBES 203 204config USER_RETURN_NOTIFIER 205 bool 206 depends on HAVE_USER_RETURN_NOTIFIER 207 help 208 Provide a kernel-internal notification when a cpu is about to 209 switch to user mode. 210 211config HAVE_IOREMAP_PROT 212 bool 213 214config HAVE_KPROBES 215 bool 216 217config HAVE_KRETPROBES 218 bool 219 220config HAVE_OPTPROBES 221 bool 222 223config HAVE_KPROBES_ON_FTRACE 224 bool 225 226config HAVE_FUNCTION_ERROR_INJECTION 227 bool 228 229config HAVE_NMI 230 bool 231 232# 233# An arch should select this if it provides all these things: 234# 235# task_pt_regs() in asm/processor.h or asm/ptrace.h 236# arch_has_single_step() if there is hardware single-step support 237# arch_has_block_step() if there is hardware block-step support 238# asm/syscall.h supplying asm-generic/syscall.h interface 239# linux/regset.h user_regset interfaces 240# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 241# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 242# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 243# signal delivery calls tracehook_signal_handler() 244# 245config HAVE_ARCH_TRACEHOOK 246 bool 247 248config HAVE_DMA_CONTIGUOUS 249 bool 250 251config GENERIC_SMP_IDLE_THREAD 252 bool 253 254config GENERIC_IDLE_POLL_SETUP 255 bool 256 257config ARCH_HAS_FORTIFY_SOURCE 258 bool 259 help 260 An architecture should select this when it can successfully 261 build and run with CONFIG_FORTIFY_SOURCE. 262 263# 264# Select if the arch provides a historic keepinit alias for the retain_initrd 265# command line option 266# 267config ARCH_HAS_KEEPINITRD 268 bool 269 270# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 271config ARCH_HAS_SET_MEMORY 272 bool 273 274# Select if arch has all set_direct_map_invalid/default() functions 275config ARCH_HAS_SET_DIRECT_MAP 276 bool 277 278# 279# Select if the architecture provides the arch_dma_set_uncached symbol to 280# either provide an uncached segement alias for a DMA allocation, or 281# to remap the page tables in place. 282# 283config ARCH_HAS_DMA_SET_UNCACHED 284 bool 285 286# 287# Select if the architectures provides the arch_dma_clear_uncached symbol 288# to undo an in-place page table remap for uncached access. 289# 290config ARCH_HAS_DMA_CLEAR_UNCACHED 291 bool 292 293# Select if arch init_task must go in the __init_task_data section 294config ARCH_TASK_STRUCT_ON_STACK 295 bool 296 297# Select if arch has its private alloc_task_struct() function 298config ARCH_TASK_STRUCT_ALLOCATOR 299 bool 300 301config HAVE_ARCH_THREAD_STRUCT_WHITELIST 302 bool 303 depends on !ARCH_TASK_STRUCT_ALLOCATOR 304 help 305 An architecture should select this to provide hardened usercopy 306 knowledge about what region of the thread_struct should be 307 whitelisted for copying to userspace. Normally this is only the 308 FPU registers. Specifically, arch_thread_struct_whitelist() 309 should be implemented. Without this, the entire thread_struct 310 field in task_struct will be left whitelisted. 311 312# Select if arch has its private alloc_thread_stack() function 313config ARCH_THREAD_STACK_ALLOCATOR 314 bool 315 316# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 317config ARCH_WANTS_DYNAMIC_TASK_STRUCT 318 bool 319 320config ARCH_32BIT_OFF_T 321 bool 322 depends on !64BIT 323 help 324 All new 32-bit architectures should have 64-bit off_t type on 325 userspace side which corresponds to the loff_t kernel type. This 326 is the requirement for modern ABIs. Some existing architectures 327 still support 32-bit off_t. This option is enabled for all such 328 architectures explicitly. 329 330config HAVE_ASM_MODVERSIONS 331 bool 332 help 333 This symbol should be selected by an architecure if it provides 334 <asm/asm-prototypes.h> to support the module versioning for symbols 335 exported from assembly code. 336 337config HAVE_REGS_AND_STACK_ACCESS_API 338 bool 339 help 340 This symbol should be selected by an architecure if it supports 341 the API needed to access registers and stack entries from pt_regs, 342 declared in asm/ptrace.h 343 For example the kprobes-based event tracer needs this API. 344 345config HAVE_RSEQ 346 bool 347 depends on HAVE_REGS_AND_STACK_ACCESS_API 348 help 349 This symbol should be selected by an architecture if it 350 supports an implementation of restartable sequences. 351 352config HAVE_FUNCTION_ARG_ACCESS_API 353 bool 354 help 355 This symbol should be selected by an architecure if it supports 356 the API needed to access function arguments from pt_regs, 357 declared in asm/ptrace.h 358 359config HAVE_HW_BREAKPOINT 360 bool 361 depends on PERF_EVENTS 362 363config HAVE_MIXED_BREAKPOINTS_REGS 364 bool 365 depends on HAVE_HW_BREAKPOINT 366 help 367 Depending on the arch implementation of hardware breakpoints, 368 some of them have separate registers for data and instruction 369 breakpoints addresses, others have mixed registers to store 370 them but define the access type in a control register. 371 Select this option if your arch implements breakpoints under the 372 latter fashion. 373 374config HAVE_USER_RETURN_NOTIFIER 375 bool 376 377config HAVE_PERF_EVENTS_NMI 378 bool 379 help 380 System hardware can generate an NMI using the perf event 381 subsystem. Also has support for calculating CPU cycle events 382 to determine how many clock cycles in a given period. 383 384config HAVE_HARDLOCKUP_DETECTOR_PERF 385 bool 386 depends on HAVE_PERF_EVENTS_NMI 387 help 388 The arch chooses to use the generic perf-NMI-based hardlockup 389 detector. Must define HAVE_PERF_EVENTS_NMI. 390 391config HAVE_NMI_WATCHDOG 392 depends on HAVE_NMI 393 bool 394 help 395 The arch provides a low level NMI watchdog. It provides 396 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 397 398config HAVE_HARDLOCKUP_DETECTOR_ARCH 399 bool 400 select HAVE_NMI_WATCHDOG 401 help 402 The arch chooses to provide its own hardlockup detector, which is 403 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 404 interfaces and parameters provided by hardlockup detector subsystem. 405 406config HAVE_PERF_REGS 407 bool 408 help 409 Support selective register dumps for perf events. This includes 410 bit-mapping of each registers and a unique architecture id. 411 412config HAVE_PERF_USER_STACK_DUMP 413 bool 414 help 415 Support user stack dumps for perf event samples. This needs 416 access to the user stack pointer which is not unified across 417 architectures. 418 419config HAVE_ARCH_JUMP_LABEL 420 bool 421 422config HAVE_ARCH_JUMP_LABEL_RELATIVE 423 bool 424 425config MMU_GATHER_TABLE_FREE 426 bool 427 428config MMU_GATHER_RCU_TABLE_FREE 429 bool 430 select MMU_GATHER_TABLE_FREE 431 432config MMU_GATHER_PAGE_SIZE 433 bool 434 435config MMU_GATHER_NO_RANGE 436 bool 437 438config MMU_GATHER_NO_GATHER 439 bool 440 depends on MMU_GATHER_TABLE_FREE 441 442config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 443 bool 444 help 445 Temporary select until all architectures can be converted to have 446 irqs disabled over activate_mm. Architectures that do IPI based TLB 447 shootdowns should enable this. 448 449config ARCH_HAVE_NMI_SAFE_CMPXCHG 450 bool 451 452config HAVE_ALIGNED_STRUCT_PAGE 453 bool 454 help 455 This makes sure that struct pages are double word aligned and that 456 e.g. the SLUB allocator can perform double word atomic operations 457 on a struct page for better performance. However selecting this 458 might increase the size of a struct page by a word. 459 460config HAVE_CMPXCHG_LOCAL 461 bool 462 463config HAVE_CMPXCHG_DOUBLE 464 bool 465 466config ARCH_WEAK_RELEASE_ACQUIRE 467 bool 468 469config ARCH_WANT_IPC_PARSE_VERSION 470 bool 471 472config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 473 bool 474 475config ARCH_WANT_OLD_COMPAT_IPC 476 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 477 bool 478 479config HAVE_ARCH_SECCOMP 480 bool 481 help 482 An arch should select this symbol to support seccomp mode 1 (the fixed 483 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn, 484 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment: 485 - __NR_seccomp_read_32 486 - __NR_seccomp_write_32 487 - __NR_seccomp_exit_32 488 - __NR_seccomp_sigreturn_32 489 490config HAVE_ARCH_SECCOMP_FILTER 491 bool 492 select HAVE_ARCH_SECCOMP 493 help 494 An arch should select this symbol if it provides all of these things: 495 - all the requirements for HAVE_ARCH_SECCOMP 496 - syscall_get_arch() 497 - syscall_get_arguments() 498 - syscall_rollback() 499 - syscall_set_return_value() 500 - SIGSYS siginfo_t support 501 - secure_computing is called from a ptrace_event()-safe context 502 - secure_computing return value is checked and a return value of -1 503 results in the system call being skipped immediately. 504 - seccomp syscall wired up 505 506config SECCOMP 507 prompt "Enable seccomp to safely execute untrusted bytecode" 508 def_bool y 509 depends on HAVE_ARCH_SECCOMP 510 help 511 This kernel feature is useful for number crunching applications 512 that may need to handle untrusted bytecode during their 513 execution. By using pipes or other transports made available 514 to the process as file descriptors supporting the read/write 515 syscalls, it's possible to isolate those applications in their 516 own address space using seccomp. Once seccomp is enabled via 517 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be 518 disabled and the task is only allowed to execute a few safe 519 syscalls defined by each seccomp mode. 520 521 If unsure, say Y. 522 523config SECCOMP_FILTER 524 def_bool y 525 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 526 help 527 Enable tasks to build secure computing environments defined 528 in terms of Berkeley Packet Filter programs which implement 529 task-defined system call filtering polices. 530 531 See Documentation/userspace-api/seccomp_filter.rst for details. 532 533config HAVE_ARCH_STACKLEAK 534 bool 535 help 536 An architecture should select this if it has the code which 537 fills the used part of the kernel stack with the STACKLEAK_POISON 538 value before returning from system calls. 539 540config HAVE_STACKPROTECTOR 541 bool 542 help 543 An arch should select this symbol if: 544 - it has implemented a stack canary (e.g. __stack_chk_guard) 545 546config STACKPROTECTOR 547 bool "Stack Protector buffer overflow detection" 548 depends on HAVE_STACKPROTECTOR 549 depends on $(cc-option,-fstack-protector) 550 default y 551 help 552 This option turns on the "stack-protector" GCC feature. This 553 feature puts, at the beginning of functions, a canary value on 554 the stack just before the return address, and validates 555 the value just before actually returning. Stack based buffer 556 overflows (that need to overwrite this return address) now also 557 overwrite the canary, which gets detected and the attack is then 558 neutralized via a kernel panic. 559 560 Functions will have the stack-protector canary logic added if they 561 have an 8-byte or larger character array on the stack. 562 563 This feature requires gcc version 4.2 or above, or a distribution 564 gcc with the feature backported ("-fstack-protector"). 565 566 On an x86 "defconfig" build, this feature adds canary checks to 567 about 3% of all kernel functions, which increases kernel code size 568 by about 0.3%. 569 570config STACKPROTECTOR_STRONG 571 bool "Strong Stack Protector" 572 depends on STACKPROTECTOR 573 depends on $(cc-option,-fstack-protector-strong) 574 default y 575 help 576 Functions will have the stack-protector canary logic added in any 577 of the following conditions: 578 579 - local variable's address used as part of the right hand side of an 580 assignment or function argument 581 - local variable is an array (or union containing an array), 582 regardless of array type or length 583 - uses register local variables 584 585 This feature requires gcc version 4.9 or above, or a distribution 586 gcc with the feature backported ("-fstack-protector-strong"). 587 588 On an x86 "defconfig" build, this feature adds canary checks to 589 about 20% of all kernel functions, which increases the kernel code 590 size by about 2%. 591 592config ARCH_SUPPORTS_SHADOW_CALL_STACK 593 bool 594 help 595 An architecture should select this if it supports Clang's Shadow 596 Call Stack and implements runtime support for shadow stack 597 switching. 598 599config SHADOW_CALL_STACK 600 bool "Clang Shadow Call Stack" 601 depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK 602 depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER 603 help 604 This option enables Clang's Shadow Call Stack, which uses a 605 shadow stack to protect function return addresses from being 606 overwritten by an attacker. More information can be found in 607 Clang's documentation: 608 609 https://clang.llvm.org/docs/ShadowCallStack.html 610 611 Note that security guarantees in the kernel differ from the 612 ones documented for user space. The kernel must store addresses 613 of shadow stacks in memory, which means an attacker capable of 614 reading and writing arbitrary memory may be able to locate them 615 and hijack control flow by modifying the stacks. 616 617config HAVE_ARCH_WITHIN_STACK_FRAMES 618 bool 619 help 620 An architecture should select this if it can walk the kernel stack 621 frames to determine if an object is part of either the arguments 622 or local variables (i.e. that it excludes saved return addresses, 623 and similar) by implementing an inline arch_within_stack_frames(), 624 which is used by CONFIG_HARDENED_USERCOPY. 625 626config HAVE_CONTEXT_TRACKING 627 bool 628 help 629 Provide kernel/user boundaries probes necessary for subsystems 630 that need it, such as userspace RCU extended quiescent state. 631 Syscalls need to be wrapped inside user_exit()-user_enter(), either 632 optimized behind static key or through the slow path using TIF_NOHZ 633 flag. Exceptions handlers must be wrapped as well. Irqs are already 634 protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal 635 handling on irq exit still need to be protected. 636 637config HAVE_TIF_NOHZ 638 bool 639 help 640 Arch relies on TIF_NOHZ and syscall slow path to implement context 641 tracking calls to user_enter()/user_exit(). 642 643config HAVE_VIRT_CPU_ACCOUNTING 644 bool 645 646config ARCH_HAS_SCALED_CPUTIME 647 bool 648 649config HAVE_VIRT_CPU_ACCOUNTING_GEN 650 bool 651 default y if 64BIT 652 help 653 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 654 Before enabling this option, arch code must be audited 655 to ensure there are no races in concurrent read/write of 656 cputime_t. For example, reading/writing 64-bit cputime_t on 657 some 32-bit arches may require multiple accesses, so proper 658 locking is needed to protect against concurrent accesses. 659 660 661config HAVE_IRQ_TIME_ACCOUNTING 662 bool 663 help 664 Archs need to ensure they use a high enough resolution clock to 665 support irq time accounting and then call enable_sched_clock_irqtime(). 666 667config HAVE_MOVE_PMD 668 bool 669 help 670 Archs that select this are able to move page tables at the PMD level. 671 672config HAVE_ARCH_TRANSPARENT_HUGEPAGE 673 bool 674 675config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 676 bool 677 678config HAVE_ARCH_HUGE_VMAP 679 bool 680 681config ARCH_WANT_HUGE_PMD_SHARE 682 bool 683 684config HAVE_ARCH_SOFT_DIRTY 685 bool 686 687config HAVE_MOD_ARCH_SPECIFIC 688 bool 689 help 690 The arch uses struct mod_arch_specific to store data. Many arches 691 just need a simple module loader without arch specific data - those 692 should not enable this. 693 694config MODULES_USE_ELF_RELA 695 bool 696 help 697 Modules only use ELF RELA relocations. Modules with ELF REL 698 relocations will give an error. 699 700config MODULES_USE_ELF_REL 701 bool 702 help 703 Modules only use ELF REL relocations. Modules with ELF RELA 704 relocations will give an error. 705 706config HAVE_IRQ_EXIT_ON_IRQ_STACK 707 bool 708 help 709 Architecture doesn't only execute the irq handler on the irq stack 710 but also irq_exit(). This way we can process softirqs on this irq 711 stack instead of switching to a new one when we call __do_softirq() 712 in the end of an hardirq. 713 This spares a stack switch and improves cache usage on softirq 714 processing. 715 716config PGTABLE_LEVELS 717 int 718 default 2 719 720config ARCH_HAS_ELF_RANDOMIZE 721 bool 722 help 723 An architecture supports choosing randomized locations for 724 stack, mmap, brk, and ET_DYN. Defined functions: 725 - arch_mmap_rnd() 726 - arch_randomize_brk() 727 728config HAVE_ARCH_MMAP_RND_BITS 729 bool 730 help 731 An arch should select this symbol if it supports setting a variable 732 number of bits for use in establishing the base address for mmap 733 allocations, has MMU enabled and provides values for both: 734 - ARCH_MMAP_RND_BITS_MIN 735 - ARCH_MMAP_RND_BITS_MAX 736 737config HAVE_EXIT_THREAD 738 bool 739 help 740 An architecture implements exit_thread. 741 742config ARCH_MMAP_RND_BITS_MIN 743 int 744 745config ARCH_MMAP_RND_BITS_MAX 746 int 747 748config ARCH_MMAP_RND_BITS_DEFAULT 749 int 750 751config ARCH_MMAP_RND_BITS 752 int "Number of bits to use for ASLR of mmap base address" if EXPERT 753 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 754 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 755 default ARCH_MMAP_RND_BITS_MIN 756 depends on HAVE_ARCH_MMAP_RND_BITS 757 help 758 This value can be used to select the number of bits to use to 759 determine the random offset to the base address of vma regions 760 resulting from mmap allocations. This value will be bounded 761 by the architecture's minimum and maximum supported values. 762 763 This value can be changed after boot using the 764 /proc/sys/vm/mmap_rnd_bits tunable 765 766config HAVE_ARCH_MMAP_RND_COMPAT_BITS 767 bool 768 help 769 An arch should select this symbol if it supports running applications 770 in compatibility mode, supports setting a variable number of bits for 771 use in establishing the base address for mmap allocations, has MMU 772 enabled and provides values for both: 773 - ARCH_MMAP_RND_COMPAT_BITS_MIN 774 - ARCH_MMAP_RND_COMPAT_BITS_MAX 775 776config ARCH_MMAP_RND_COMPAT_BITS_MIN 777 int 778 779config ARCH_MMAP_RND_COMPAT_BITS_MAX 780 int 781 782config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 783 int 784 785config ARCH_MMAP_RND_COMPAT_BITS 786 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 787 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 788 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 789 default ARCH_MMAP_RND_COMPAT_BITS_MIN 790 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 791 help 792 This value can be used to select the number of bits to use to 793 determine the random offset to the base address of vma regions 794 resulting from mmap allocations for compatible applications This 795 value will be bounded by the architecture's minimum and maximum 796 supported values. 797 798 This value can be changed after boot using the 799 /proc/sys/vm/mmap_rnd_compat_bits tunable 800 801config HAVE_ARCH_COMPAT_MMAP_BASES 802 bool 803 help 804 This allows 64bit applications to invoke 32-bit mmap() syscall 805 and vice-versa 32-bit applications to call 64-bit mmap(). 806 Required for applications doing different bitness syscalls. 807 808# This allows to use a set of generic functions to determine mmap base 809# address by giving priority to top-down scheme only if the process 810# is not in legacy mode (compat task, unlimited stack size or 811# sysctl_legacy_va_layout). 812# Architecture that selects this option can provide its own version of: 813# - STACK_RND_MASK 814config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 815 bool 816 depends on MMU 817 select ARCH_HAS_ELF_RANDOMIZE 818 819config HAVE_STACK_VALIDATION 820 bool 821 help 822 Architecture supports the 'objtool check' host tool command, which 823 performs compile-time stack metadata validation. 824 825config HAVE_RELIABLE_STACKTRACE 826 bool 827 help 828 Architecture has either save_stack_trace_tsk_reliable() or 829 arch_stack_walk_reliable() function which only returns a stack trace 830 if it can guarantee the trace is reliable. 831 832config HAVE_ARCH_HASH 833 bool 834 default n 835 help 836 If this is set, the architecture provides an <asm/hash.h> 837 file which provides platform-specific implementations of some 838 functions in <linux/hash.h> or fs/namei.c. 839 840config HAVE_ARCH_NVRAM_OPS 841 bool 842 843config ISA_BUS_API 844 def_bool ISA 845 846# 847# ABI hall of shame 848# 849config CLONE_BACKWARDS 850 bool 851 help 852 Architecture has tls passed as the 4th argument of clone(2), 853 not the 5th one. 854 855config CLONE_BACKWARDS2 856 bool 857 help 858 Architecture has the first two arguments of clone(2) swapped. 859 860config CLONE_BACKWARDS3 861 bool 862 help 863 Architecture has tls passed as the 3rd argument of clone(2), 864 not the 5th one. 865 866config ODD_RT_SIGACTION 867 bool 868 help 869 Architecture has unusual rt_sigaction(2) arguments 870 871config OLD_SIGSUSPEND 872 bool 873 help 874 Architecture has old sigsuspend(2) syscall, of one-argument variety 875 876config OLD_SIGSUSPEND3 877 bool 878 help 879 Even weirder antique ABI - three-argument sigsuspend(2) 880 881config OLD_SIGACTION 882 bool 883 help 884 Architecture has old sigaction(2) syscall. Nope, not the same 885 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 886 but fairly different variant of sigaction(2), thanks to OSF/1 887 compatibility... 888 889config COMPAT_OLD_SIGACTION 890 bool 891 892config COMPAT_32BIT_TIME 893 bool "Provide system calls for 32-bit time_t" 894 default !64BIT || COMPAT 895 help 896 This enables 32 bit time_t support in addition to 64 bit time_t support. 897 This is relevant on all 32-bit architectures, and 64-bit architectures 898 as part of compat syscall handling. 899 900config ARCH_NO_PREEMPT 901 bool 902 903config ARCH_SUPPORTS_RT 904 bool 905 906config CPU_NO_EFFICIENT_FFS 907 def_bool n 908 909config HAVE_ARCH_VMAP_STACK 910 def_bool n 911 help 912 An arch should select this symbol if it can support kernel stacks 913 in vmalloc space. This means: 914 915 - vmalloc space must be large enough to hold many kernel stacks. 916 This may rule out many 32-bit architectures. 917 918 - Stacks in vmalloc space need to work reliably. For example, if 919 vmap page tables are created on demand, either this mechanism 920 needs to work while the stack points to a virtual address with 921 unpopulated page tables or arch code (switch_to() and switch_mm(), 922 most likely) needs to ensure that the stack's page table entries 923 are populated before running on a possibly unpopulated stack. 924 925 - If the stack overflows into a guard page, something reasonable 926 should happen. The definition of "reasonable" is flexible, but 927 instantly rebooting without logging anything would be unfriendly. 928 929config VMAP_STACK 930 default y 931 bool "Use a virtually-mapped stack" 932 depends on HAVE_ARCH_VMAP_STACK 933 depends on !KASAN || KASAN_VMALLOC 934 help 935 Enable this if you want the use virtually-mapped kernel stacks 936 with guard pages. This causes kernel stack overflows to be 937 caught immediately rather than causing difficult-to-diagnose 938 corruption. 939 940 To use this with KASAN, the architecture must support backing 941 virtual mappings with real shadow memory, and KASAN_VMALLOC must 942 be enabled. 943 944config ARCH_OPTIONAL_KERNEL_RWX 945 def_bool n 946 947config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 948 def_bool n 949 950config ARCH_HAS_STRICT_KERNEL_RWX 951 def_bool n 952 953config STRICT_KERNEL_RWX 954 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 955 depends on ARCH_HAS_STRICT_KERNEL_RWX 956 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 957 help 958 If this is set, kernel text and rodata memory will be made read-only, 959 and non-text memory will be made non-executable. This provides 960 protection against certain security exploits (e.g. executing the heap 961 or modifying text) 962 963 These features are considered standard security practice these days. 964 You should say Y here in almost all cases. 965 966config ARCH_HAS_STRICT_MODULE_RWX 967 def_bool n 968 969config STRICT_MODULE_RWX 970 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 971 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 972 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 973 help 974 If this is set, module text and rodata memory will be made read-only, 975 and non-text memory will be made non-executable. This provides 976 protection against certain security exploits (e.g. writing to text) 977 978# select if the architecture provides an asm/dma-direct.h header 979config ARCH_HAS_PHYS_TO_DMA 980 bool 981 982config HAVE_ARCH_COMPILER_H 983 bool 984 help 985 An architecture can select this if it provides an 986 asm/compiler.h header that should be included after 987 linux/compiler-*.h in order to override macro definitions that those 988 headers generally provide. 989 990config HAVE_ARCH_PREL32_RELOCATIONS 991 bool 992 help 993 May be selected by an architecture if it supports place-relative 994 32-bit relocations, both in the toolchain and in the module loader, 995 in which case relative references can be used in special sections 996 for PCI fixup, initcalls etc which are only half the size on 64 bit 997 architectures, and don't require runtime relocation on relocatable 998 kernels. 999 1000config ARCH_USE_MEMREMAP_PROT 1001 bool 1002 1003config LOCK_EVENT_COUNTS 1004 bool "Locking event counts collection" 1005 depends on DEBUG_FS 1006 help 1007 Enable light-weight counting of various locking related events 1008 in the system with minimal performance impact. This reduces 1009 the chance of application behavior change because of timing 1010 differences. The counts are reported via debugfs. 1011 1012# Select if the architecture has support for applying RELR relocations. 1013config ARCH_HAS_RELR 1014 bool 1015 1016config RELR 1017 bool "Use RELR relocation packing" 1018 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR 1019 default y 1020 help 1021 Store the kernel's dynamic relocations in the RELR relocation packing 1022 format. Requires a compatible linker (LLD supports this feature), as 1023 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy 1024 are compatible). 1025 1026config ARCH_HAS_MEM_ENCRYPT 1027 bool 1028 1029config HAVE_SPARSE_SYSCALL_NR 1030 bool 1031 help 1032 An architecture should select this if its syscall numbering is sparse 1033 to save space. For example, MIPS architecture has a syscall array with 1034 entries at 4000, 5000 and 6000 locations. This option turns on syscall 1035 related optimizations for a given architecture. 1036 1037config ARCH_HAS_VDSO_DATA 1038 bool 1039 1040config HAVE_STATIC_CALL 1041 bool 1042 1043config HAVE_STATIC_CALL_INLINE 1044 bool 1045 depends on HAVE_STATIC_CALL 1046 1047config ARCH_WANT_LD_ORPHAN_WARN 1048 bool 1049 help 1050 An arch should select this symbol once all linker sections are explicitly 1051 included, size-asserted, or discarded in the linker scripts. This is 1052 important because we never want expected sections to be placed heuristically 1053 by the linker, since the locations of such sections can change between linker 1054 versions. 1055 1056config ARCH_SPLIT_ARG64 1057 bool 1058 help 1059 If a 32-bit architecture requires 64-bit arguments to be split into 1060 pairs of 32-bit arguments, select this option. 1061 1062source "kernel/gcov/Kconfig" 1063 1064source "scripts/gcc-plugins/Kconfig" 1065 1066endmenu 1067