1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6config CRASH_CORE 7 bool 8 9config KEXEC_CORE 10 select CRASH_CORE 11 bool 12 13config HAVE_IMA_KEXEC 14 bool 15 16config OPROFILE 17 tristate "OProfile system profiling" 18 depends on PROFILING 19 depends on HAVE_OPROFILE 20 select RING_BUFFER 21 select RING_BUFFER_ALLOW_SWAP 22 help 23 OProfile is a profiling system capable of profiling the 24 whole system, include the kernel, kernel modules, libraries, 25 and applications. 26 27 If unsure, say N. 28 29config OPROFILE_EVENT_MULTIPLEX 30 bool "OProfile multiplexing support (EXPERIMENTAL)" 31 default n 32 depends on OPROFILE && X86 33 help 34 The number of hardware counters is limited. The multiplexing 35 feature enables OProfile to gather more events than counters 36 are provided by the hardware. This is realized by switching 37 between events at a user specified time interval. 38 39 If unsure, say N. 40 41config HAVE_OPROFILE 42 bool 43 44config OPROFILE_NMI_TIMER 45 def_bool y 46 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 47 48config KPROBES 49 bool "Kprobes" 50 depends on MODULES 51 depends on HAVE_KPROBES 52 select KALLSYMS 53 help 54 Kprobes allows you to trap at almost any kernel address and 55 execute a callback function. register_kprobe() establishes 56 a probepoint and specifies the callback. Kprobes is useful 57 for kernel debugging, non-intrusive instrumentation and testing. 58 If in doubt, say "N". 59 60config JUMP_LABEL 61 bool "Optimize very unlikely/likely branches" 62 depends on HAVE_ARCH_JUMP_LABEL 63 help 64 This option enables a transparent branch optimization that 65 makes certain almost-always-true or almost-always-false branch 66 conditions even cheaper to execute within the kernel. 67 68 Certain performance-sensitive kernel code, such as trace points, 69 scheduler functionality, networking code and KVM have such 70 branches and include support for this optimization technique. 71 72 If it is detected that the compiler has support for "asm goto", 73 the kernel will compile such branches with just a nop 74 instruction. When the condition flag is toggled to true, the 75 nop will be converted to a jump instruction to execute the 76 conditional block of instructions. 77 78 This technique lowers overhead and stress on the branch prediction 79 of the processor and generally makes the kernel faster. The update 80 of the condition is slower, but those are always very rare. 81 82 ( On 32-bit x86, the necessary options added to the compiler 83 flags may increase the size of the kernel slightly. ) 84 85config STATIC_KEYS_SELFTEST 86 bool "Static key selftest" 87 depends on JUMP_LABEL 88 help 89 Boot time self-test of the branch patching code. 90 91config OPTPROBES 92 def_bool y 93 depends on KPROBES && HAVE_OPTPROBES 94 select TASKS_RCU if PREEMPT 95 96config KPROBES_ON_FTRACE 97 def_bool y 98 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 99 depends on DYNAMIC_FTRACE_WITH_REGS 100 help 101 If function tracer is enabled and the arch supports full 102 passing of pt_regs to function tracing, then kprobes can 103 optimize on top of function tracing. 104 105config UPROBES 106 def_bool n 107 depends on ARCH_SUPPORTS_UPROBES 108 help 109 Uprobes is the user-space counterpart to kprobes: they 110 enable instrumentation applications (such as 'perf probe') 111 to establish unintrusive probes in user-space binaries and 112 libraries, by executing handler functions when the probes 113 are hit by user-space applications. 114 115 ( These probes come in the form of single-byte breakpoints, 116 managed by the kernel and kept transparent to the probed 117 application. ) 118 119config HAVE_64BIT_ALIGNED_ACCESS 120 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 121 help 122 Some architectures require 64 bit accesses to be 64 bit 123 aligned, which also requires structs containing 64 bit values 124 to be 64 bit aligned too. This includes some 32 bit 125 architectures which can do 64 bit accesses, as well as 64 bit 126 architectures without unaligned access. 127 128 This symbol should be selected by an architecture if 64 bit 129 accesses are required to be 64 bit aligned in this way even 130 though it is not a 64 bit architecture. 131 132 See Documentation/unaligned-memory-access.txt for more 133 information on the topic of unaligned memory accesses. 134 135config HAVE_EFFICIENT_UNALIGNED_ACCESS 136 bool 137 help 138 Some architectures are unable to perform unaligned accesses 139 without the use of get_unaligned/put_unaligned. Others are 140 unable to perform such accesses efficiently (e.g. trap on 141 unaligned access and require fixing it up in the exception 142 handler.) 143 144 This symbol should be selected by an architecture if it can 145 perform unaligned accesses efficiently to allow different 146 code paths to be selected for these cases. Some network 147 drivers, for example, could opt to not fix up alignment 148 problems with received packets if doing so would not help 149 much. 150 151 See Documentation/unaligned-memory-access.txt for more 152 information on the topic of unaligned memory accesses. 153 154config ARCH_USE_BUILTIN_BSWAP 155 bool 156 help 157 Modern versions of GCC (since 4.4) have builtin functions 158 for handling byte-swapping. Using these, instead of the old 159 inline assembler that the architecture code provides in the 160 __arch_bswapXX() macros, allows the compiler to see what's 161 happening and offers more opportunity for optimisation. In 162 particular, the compiler will be able to combine the byteswap 163 with a nearby load or store and use load-and-swap or 164 store-and-swap instructions if the architecture has them. It 165 should almost *never* result in code which is worse than the 166 hand-coded assembler in <asm/swab.h>. But just in case it 167 does, the use of the builtins is optional. 168 169 Any architecture with load-and-swap or store-and-swap 170 instructions should set this. And it shouldn't hurt to set it 171 on architectures that don't have such instructions. 172 173config KRETPROBES 174 def_bool y 175 depends on KPROBES && HAVE_KRETPROBES 176 177config USER_RETURN_NOTIFIER 178 bool 179 depends on HAVE_USER_RETURN_NOTIFIER 180 help 181 Provide a kernel-internal notification when a cpu is about to 182 switch to user mode. 183 184config HAVE_IOREMAP_PROT 185 bool 186 187config HAVE_KPROBES 188 bool 189 190config HAVE_KRETPROBES 191 bool 192 193config HAVE_OPTPROBES 194 bool 195 196config HAVE_KPROBES_ON_FTRACE 197 bool 198 199config HAVE_FUNCTION_ERROR_INJECTION 200 bool 201 202config HAVE_NMI 203 bool 204 205# 206# An arch should select this if it provides all these things: 207# 208# task_pt_regs() in asm/processor.h or asm/ptrace.h 209# arch_has_single_step() if there is hardware single-step support 210# arch_has_block_step() if there is hardware block-step support 211# asm/syscall.h supplying asm-generic/syscall.h interface 212# linux/regset.h user_regset interfaces 213# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 214# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 215# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 216# signal delivery calls tracehook_signal_handler() 217# 218config HAVE_ARCH_TRACEHOOK 219 bool 220 221config HAVE_DMA_CONTIGUOUS 222 bool 223 224config GENERIC_SMP_IDLE_THREAD 225 bool 226 227config GENERIC_IDLE_POLL_SETUP 228 bool 229 230config ARCH_HAS_FORTIFY_SOURCE 231 bool 232 help 233 An architecture should select this when it can successfully 234 build and run with CONFIG_FORTIFY_SOURCE. 235 236# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 237config ARCH_HAS_SET_MEMORY 238 bool 239 240# Select if arch init_task must go in the __init_task_data section 241config ARCH_TASK_STRUCT_ON_STACK 242 bool 243 244# Select if arch has its private alloc_task_struct() function 245config ARCH_TASK_STRUCT_ALLOCATOR 246 bool 247 248config HAVE_ARCH_THREAD_STRUCT_WHITELIST 249 bool 250 depends on !ARCH_TASK_STRUCT_ALLOCATOR 251 help 252 An architecture should select this to provide hardened usercopy 253 knowledge about what region of the thread_struct should be 254 whitelisted for copying to userspace. Normally this is only the 255 FPU registers. Specifically, arch_thread_struct_whitelist() 256 should be implemented. Without this, the entire thread_struct 257 field in task_struct will be left whitelisted. 258 259# Select if arch has its private alloc_thread_stack() function 260config ARCH_THREAD_STACK_ALLOCATOR 261 bool 262 263# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 264config ARCH_WANTS_DYNAMIC_TASK_STRUCT 265 bool 266 267config HAVE_REGS_AND_STACK_ACCESS_API 268 bool 269 help 270 This symbol should be selected by an architecure if it supports 271 the API needed to access registers and stack entries from pt_regs, 272 declared in asm/ptrace.h 273 For example the kprobes-based event tracer needs this API. 274 275config HAVE_RSEQ 276 bool 277 depends on HAVE_REGS_AND_STACK_ACCESS_API 278 help 279 This symbol should be selected by an architecture if it 280 supports an implementation of restartable sequences. 281 282config HAVE_CLK 283 bool 284 help 285 The <linux/clk.h> calls support software clock gating and 286 thus are a key power management tool on many systems. 287 288config HAVE_HW_BREAKPOINT 289 bool 290 depends on PERF_EVENTS 291 292config HAVE_MIXED_BREAKPOINTS_REGS 293 bool 294 depends on HAVE_HW_BREAKPOINT 295 help 296 Depending on the arch implementation of hardware breakpoints, 297 some of them have separate registers for data and instruction 298 breakpoints addresses, others have mixed registers to store 299 them but define the access type in a control register. 300 Select this option if your arch implements breakpoints under the 301 latter fashion. 302 303config HAVE_USER_RETURN_NOTIFIER 304 bool 305 306config HAVE_PERF_EVENTS_NMI 307 bool 308 help 309 System hardware can generate an NMI using the perf event 310 subsystem. Also has support for calculating CPU cycle events 311 to determine how many clock cycles in a given period. 312 313config HAVE_HARDLOCKUP_DETECTOR_PERF 314 bool 315 depends on HAVE_PERF_EVENTS_NMI 316 help 317 The arch chooses to use the generic perf-NMI-based hardlockup 318 detector. Must define HAVE_PERF_EVENTS_NMI. 319 320config HAVE_NMI_WATCHDOG 321 depends on HAVE_NMI 322 bool 323 help 324 The arch provides a low level NMI watchdog. It provides 325 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 326 327config HAVE_HARDLOCKUP_DETECTOR_ARCH 328 bool 329 select HAVE_NMI_WATCHDOG 330 help 331 The arch chooses to provide its own hardlockup detector, which is 332 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 333 interfaces and parameters provided by hardlockup detector subsystem. 334 335config HAVE_PERF_REGS 336 bool 337 help 338 Support selective register dumps for perf events. This includes 339 bit-mapping of each registers and a unique architecture id. 340 341config HAVE_PERF_USER_STACK_DUMP 342 bool 343 help 344 Support user stack dumps for perf event samples. This needs 345 access to the user stack pointer which is not unified across 346 architectures. 347 348config HAVE_ARCH_JUMP_LABEL 349 bool 350 351config HAVE_RCU_TABLE_FREE 352 bool 353 354config ARCH_HAVE_NMI_SAFE_CMPXCHG 355 bool 356 357config HAVE_ALIGNED_STRUCT_PAGE 358 bool 359 help 360 This makes sure that struct pages are double word aligned and that 361 e.g. the SLUB allocator can perform double word atomic operations 362 on a struct page for better performance. However selecting this 363 might increase the size of a struct page by a word. 364 365config HAVE_CMPXCHG_LOCAL 366 bool 367 368config HAVE_CMPXCHG_DOUBLE 369 bool 370 371config ARCH_WEAK_RELEASE_ACQUIRE 372 bool 373 374config ARCH_WANT_IPC_PARSE_VERSION 375 bool 376 377config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 378 bool 379 380config ARCH_WANT_OLD_COMPAT_IPC 381 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 382 bool 383 384config HAVE_ARCH_SECCOMP_FILTER 385 bool 386 help 387 An arch should select this symbol if it provides all of these things: 388 - syscall_get_arch() 389 - syscall_get_arguments() 390 - syscall_rollback() 391 - syscall_set_return_value() 392 - SIGSYS siginfo_t support 393 - secure_computing is called from a ptrace_event()-safe context 394 - secure_computing return value is checked and a return value of -1 395 results in the system call being skipped immediately. 396 - seccomp syscall wired up 397 398config SECCOMP_FILTER 399 def_bool y 400 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 401 help 402 Enable tasks to build secure computing environments defined 403 in terms of Berkeley Packet Filter programs which implement 404 task-defined system call filtering polices. 405 406 See Documentation/userspace-api/seccomp_filter.rst for details. 407 408preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC)) 409 410config PLUGIN_HOSTCC 411 string 412 default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" 413 help 414 Host compiler used to build GCC plugins. This can be $(HOSTCXX), 415 $(HOSTCC), or a null string if GCC plugin is unsupported. 416 417config HAVE_GCC_PLUGINS 418 bool 419 help 420 An arch should select this symbol if it supports building with 421 GCC plugins. 422 423menuconfig GCC_PLUGINS 424 bool "GCC plugins" 425 depends on HAVE_GCC_PLUGINS 426 depends on PLUGIN_HOSTCC != "" 427 help 428 GCC plugins are loadable modules that provide extra features to the 429 compiler. They are useful for runtime instrumentation and static analysis. 430 431 See Documentation/gcc-plugins.txt for details. 432 433config GCC_PLUGIN_CYC_COMPLEXITY 434 bool "Compute the cyclomatic complexity of a function" if EXPERT 435 depends on GCC_PLUGINS 436 depends on !COMPILE_TEST # too noisy 437 help 438 The complexity M of a function's control flow graph is defined as: 439 M = E - N + 2P 440 where 441 442 E = the number of edges 443 N = the number of nodes 444 P = the number of connected components (exit nodes). 445 446 Enabling this plugin reports the complexity to stderr during the 447 build. It mainly serves as a simple example of how to create a 448 gcc plugin for the kernel. 449 450config GCC_PLUGIN_SANCOV 451 bool 452 depends on GCC_PLUGINS 453 help 454 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 455 basic blocks. It supports all gcc versions with plugin support (from 456 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 457 by Dmitry Vyukov <dvyukov@google.com>. 458 459config GCC_PLUGIN_LATENT_ENTROPY 460 bool "Generate some entropy during boot and runtime" 461 depends on GCC_PLUGINS 462 help 463 By saying Y here the kernel will instrument some kernel code to 464 extract some entropy from both original and artificially created 465 program state. This will help especially embedded systems where 466 there is little 'natural' source of entropy normally. The cost 467 is some slowdown of the boot process (about 0.5%) and fork and 468 irq processing. 469 470 Note that entropy extracted this way is not cryptographically 471 secure! 472 473 This plugin was ported from grsecurity/PaX. More information at: 474 * https://grsecurity.net/ 475 * https://pax.grsecurity.net/ 476 477config GCC_PLUGIN_STRUCTLEAK 478 bool "Force initialization of variables containing userspace addresses" 479 depends on GCC_PLUGINS 480 # Currently STRUCTLEAK inserts initialization out of live scope of 481 # variables from KASAN point of view. This leads to KASAN false 482 # positive reports. Prohibit this combination for now. 483 depends on !KASAN_EXTRA 484 help 485 This plugin zero-initializes any structures containing a 486 __user attribute. This can prevent some classes of information 487 exposures. 488 489 This plugin was ported from grsecurity/PaX. More information at: 490 * https://grsecurity.net/ 491 * https://pax.grsecurity.net/ 492 493config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 494 bool "Force initialize all struct type variables passed by reference" 495 depends on GCC_PLUGIN_STRUCTLEAK 496 depends on !COMPILE_TEST 497 help 498 Zero initialize any struct type local variable that may be passed by 499 reference without having been initialized. 500 501config GCC_PLUGIN_STRUCTLEAK_VERBOSE 502 bool "Report forcefully initialized variables" 503 depends on GCC_PLUGIN_STRUCTLEAK 504 depends on !COMPILE_TEST # too noisy 505 help 506 This option will cause a warning to be printed each time the 507 structleak plugin finds a variable it thinks needs to be 508 initialized. Since not all existing initializers are detected 509 by the plugin, this can produce false positive warnings. 510 511config GCC_PLUGIN_RANDSTRUCT 512 bool "Randomize layout of sensitive kernel structures" 513 depends on GCC_PLUGINS 514 select MODVERSIONS if MODULES 515 help 516 If you say Y here, the layouts of structures that are entirely 517 function pointers (and have not been manually annotated with 518 __no_randomize_layout), or structures that have been explicitly 519 marked with __randomize_layout, will be randomized at compile-time. 520 This can introduce the requirement of an additional information 521 exposure vulnerability for exploits targeting these structure 522 types. 523 524 Enabling this feature will introduce some performance impact, 525 slightly increase memory usage, and prevent the use of forensic 526 tools like Volatility against the system (unless the kernel 527 source tree isn't cleaned after kernel installation). 528 529 The seed used for compilation is located at 530 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 531 a make clean to allow for external modules to be compiled with 532 the existing seed and will be removed by a make mrproper or 533 make distclean. 534 535 Note that the implementation requires gcc 4.7 or newer. 536 537 This plugin was ported from grsecurity/PaX. More information at: 538 * https://grsecurity.net/ 539 * https://pax.grsecurity.net/ 540 541config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 542 bool "Use cacheline-aware structure randomization" 543 depends on GCC_PLUGIN_RANDSTRUCT 544 depends on !COMPILE_TEST # do not reduce test coverage 545 help 546 If you say Y here, the RANDSTRUCT randomization will make a 547 best effort at restricting randomization to cacheline-sized 548 groups of elements. It will further not randomize bitfields 549 in structures. This reduces the performance hit of RANDSTRUCT 550 at the cost of weakened randomization. 551 552config HAVE_STACKPROTECTOR 553 bool 554 help 555 An arch should select this symbol if: 556 - it has implemented a stack canary (e.g. __stack_chk_guard) 557 558config CC_HAS_STACKPROTECTOR_NONE 559 def_bool $(cc-option,-fno-stack-protector) 560 561config STACKPROTECTOR 562 bool "Stack Protector buffer overflow detection" 563 depends on HAVE_STACKPROTECTOR 564 depends on $(cc-option,-fstack-protector) 565 default y 566 help 567 This option turns on the "stack-protector" GCC feature. This 568 feature puts, at the beginning of functions, a canary value on 569 the stack just before the return address, and validates 570 the value just before actually returning. Stack based buffer 571 overflows (that need to overwrite this return address) now also 572 overwrite the canary, which gets detected and the attack is then 573 neutralized via a kernel panic. 574 575 Functions will have the stack-protector canary logic added if they 576 have an 8-byte or larger character array on the stack. 577 578 This feature requires gcc version 4.2 or above, or a distribution 579 gcc with the feature backported ("-fstack-protector"). 580 581 On an x86 "defconfig" build, this feature adds canary checks to 582 about 3% of all kernel functions, which increases kernel code size 583 by about 0.3%. 584 585config STACKPROTECTOR_STRONG 586 bool "Strong Stack Protector" 587 depends on STACKPROTECTOR 588 depends on $(cc-option,-fstack-protector-strong) 589 default y 590 help 591 Functions will have the stack-protector canary logic added in any 592 of the following conditions: 593 594 - local variable's address used as part of the right hand side of an 595 assignment or function argument 596 - local variable is an array (or union containing an array), 597 regardless of array type or length 598 - uses register local variables 599 600 This feature requires gcc version 4.9 or above, or a distribution 601 gcc with the feature backported ("-fstack-protector-strong"). 602 603 On an x86 "defconfig" build, this feature adds canary checks to 604 about 20% of all kernel functions, which increases the kernel code 605 size by about 2%. 606 607config HAVE_ARCH_WITHIN_STACK_FRAMES 608 bool 609 help 610 An architecture should select this if it can walk the kernel stack 611 frames to determine if an object is part of either the arguments 612 or local variables (i.e. that it excludes saved return addresses, 613 and similar) by implementing an inline arch_within_stack_frames(), 614 which is used by CONFIG_HARDENED_USERCOPY. 615 616config HAVE_CONTEXT_TRACKING 617 bool 618 help 619 Provide kernel/user boundaries probes necessary for subsystems 620 that need it, such as userspace RCU extended quiescent state. 621 Syscalls need to be wrapped inside user_exit()-user_enter() through 622 the slow path using TIF_NOHZ flag. Exceptions handlers must be 623 wrapped as well. Irqs are already protected inside 624 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 625 irq exit still need to be protected. 626 627config HAVE_VIRT_CPU_ACCOUNTING 628 bool 629 630config ARCH_HAS_SCALED_CPUTIME 631 bool 632 633config HAVE_VIRT_CPU_ACCOUNTING_GEN 634 bool 635 default y if 64BIT 636 help 637 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 638 Before enabling this option, arch code must be audited 639 to ensure there are no races in concurrent read/write of 640 cputime_t. For example, reading/writing 64-bit cputime_t on 641 some 32-bit arches may require multiple accesses, so proper 642 locking is needed to protect against concurrent accesses. 643 644 645config HAVE_IRQ_TIME_ACCOUNTING 646 bool 647 help 648 Archs need to ensure they use a high enough resolution clock to 649 support irq time accounting and then call enable_sched_clock_irqtime(). 650 651config HAVE_ARCH_TRANSPARENT_HUGEPAGE 652 bool 653 654config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 655 bool 656 657config HAVE_ARCH_HUGE_VMAP 658 bool 659 660config HAVE_ARCH_SOFT_DIRTY 661 bool 662 663config HAVE_MOD_ARCH_SPECIFIC 664 bool 665 help 666 The arch uses struct mod_arch_specific to store data. Many arches 667 just need a simple module loader without arch specific data - those 668 should not enable this. 669 670config MODULES_USE_ELF_RELA 671 bool 672 help 673 Modules only use ELF RELA relocations. Modules with ELF REL 674 relocations will give an error. 675 676config MODULES_USE_ELF_REL 677 bool 678 help 679 Modules only use ELF REL relocations. Modules with ELF RELA 680 relocations will give an error. 681 682config HAVE_IRQ_EXIT_ON_IRQ_STACK 683 bool 684 help 685 Architecture doesn't only execute the irq handler on the irq stack 686 but also irq_exit(). This way we can process softirqs on this irq 687 stack instead of switching to a new one when we call __do_softirq() 688 in the end of an hardirq. 689 This spares a stack switch and improves cache usage on softirq 690 processing. 691 692config PGTABLE_LEVELS 693 int 694 default 2 695 696config ARCH_HAS_ELF_RANDOMIZE 697 bool 698 help 699 An architecture supports choosing randomized locations for 700 stack, mmap, brk, and ET_DYN. Defined functions: 701 - arch_mmap_rnd() 702 - arch_randomize_brk() 703 704config HAVE_ARCH_MMAP_RND_BITS 705 bool 706 help 707 An arch should select this symbol if it supports setting a variable 708 number of bits for use in establishing the base address for mmap 709 allocations, has MMU enabled and provides values for both: 710 - ARCH_MMAP_RND_BITS_MIN 711 - ARCH_MMAP_RND_BITS_MAX 712 713config HAVE_EXIT_THREAD 714 bool 715 help 716 An architecture implements exit_thread. 717 718config ARCH_MMAP_RND_BITS_MIN 719 int 720 721config ARCH_MMAP_RND_BITS_MAX 722 int 723 724config ARCH_MMAP_RND_BITS_DEFAULT 725 int 726 727config ARCH_MMAP_RND_BITS 728 int "Number of bits to use for ASLR of mmap base address" if EXPERT 729 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 730 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 731 default ARCH_MMAP_RND_BITS_MIN 732 depends on HAVE_ARCH_MMAP_RND_BITS 733 help 734 This value can be used to select the number of bits to use to 735 determine the random offset to the base address of vma regions 736 resulting from mmap allocations. This value will be bounded 737 by the architecture's minimum and maximum supported values. 738 739 This value can be changed after boot using the 740 /proc/sys/vm/mmap_rnd_bits tunable 741 742config HAVE_ARCH_MMAP_RND_COMPAT_BITS 743 bool 744 help 745 An arch should select this symbol if it supports running applications 746 in compatibility mode, supports setting a variable number of bits for 747 use in establishing the base address for mmap allocations, has MMU 748 enabled and provides values for both: 749 - ARCH_MMAP_RND_COMPAT_BITS_MIN 750 - ARCH_MMAP_RND_COMPAT_BITS_MAX 751 752config ARCH_MMAP_RND_COMPAT_BITS_MIN 753 int 754 755config ARCH_MMAP_RND_COMPAT_BITS_MAX 756 int 757 758config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 759 int 760 761config ARCH_MMAP_RND_COMPAT_BITS 762 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 763 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 764 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 765 default ARCH_MMAP_RND_COMPAT_BITS_MIN 766 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 767 help 768 This value can be used to select the number of bits to use to 769 determine the random offset to the base address of vma regions 770 resulting from mmap allocations for compatible applications This 771 value will be bounded by the architecture's minimum and maximum 772 supported values. 773 774 This value can be changed after boot using the 775 /proc/sys/vm/mmap_rnd_compat_bits tunable 776 777config HAVE_ARCH_COMPAT_MMAP_BASES 778 bool 779 help 780 This allows 64bit applications to invoke 32-bit mmap() syscall 781 and vice-versa 32-bit applications to call 64-bit mmap(). 782 Required for applications doing different bitness syscalls. 783 784config HAVE_COPY_THREAD_TLS 785 bool 786 help 787 Architecture provides copy_thread_tls to accept tls argument via 788 normal C parameter passing, rather than extracting the syscall 789 argument from pt_regs. 790 791config HAVE_STACK_VALIDATION 792 bool 793 help 794 Architecture supports the 'objtool check' host tool command, which 795 performs compile-time stack metadata validation. 796 797config HAVE_RELIABLE_STACKTRACE 798 bool 799 help 800 Architecture has a save_stack_trace_tsk_reliable() function which 801 only returns a stack trace if it can guarantee the trace is reliable. 802 803config HAVE_ARCH_HASH 804 bool 805 default n 806 help 807 If this is set, the architecture provides an <asm/hash.h> 808 file which provides platform-specific implementations of some 809 functions in <linux/hash.h> or fs/namei.c. 810 811config ISA_BUS_API 812 def_bool ISA 813 814# 815# ABI hall of shame 816# 817config CLONE_BACKWARDS 818 bool 819 help 820 Architecture has tls passed as the 4th argument of clone(2), 821 not the 5th one. 822 823config CLONE_BACKWARDS2 824 bool 825 help 826 Architecture has the first two arguments of clone(2) swapped. 827 828config CLONE_BACKWARDS3 829 bool 830 help 831 Architecture has tls passed as the 3rd argument of clone(2), 832 not the 5th one. 833 834config ODD_RT_SIGACTION 835 bool 836 help 837 Architecture has unusual rt_sigaction(2) arguments 838 839config OLD_SIGSUSPEND 840 bool 841 help 842 Architecture has old sigsuspend(2) syscall, of one-argument variety 843 844config OLD_SIGSUSPEND3 845 bool 846 help 847 Even weirder antique ABI - three-argument sigsuspend(2) 848 849config OLD_SIGACTION 850 bool 851 help 852 Architecture has old sigaction(2) syscall. Nope, not the same 853 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 854 but fairly different variant of sigaction(2), thanks to OSF/1 855 compatibility... 856 857config COMPAT_OLD_SIGACTION 858 bool 859 860config 64BIT_TIME 861 def_bool ARCH_HAS_64BIT_TIME 862 help 863 This should be selected by all architectures that need to support 864 new system calls with a 64-bit time_t. This is relevant on all 32-bit 865 architectures, and 64-bit architectures as part of compat syscall 866 handling. 867 868config COMPAT_32BIT_TIME 869 def_bool (!64BIT && 64BIT_TIME) || COMPAT 870 help 871 This enables 32 bit time_t support in addition to 64 bit time_t support. 872 This is relevant on all 32-bit architectures, and 64-bit architectures 873 as part of compat syscall handling. 874 875config ARCH_NO_COHERENT_DMA_MMAP 876 bool 877 878config CPU_NO_EFFICIENT_FFS 879 def_bool n 880 881config HAVE_ARCH_VMAP_STACK 882 def_bool n 883 help 884 An arch should select this symbol if it can support kernel stacks 885 in vmalloc space. This means: 886 887 - vmalloc space must be large enough to hold many kernel stacks. 888 This may rule out many 32-bit architectures. 889 890 - Stacks in vmalloc space need to work reliably. For example, if 891 vmap page tables are created on demand, either this mechanism 892 needs to work while the stack points to a virtual address with 893 unpopulated page tables or arch code (switch_to() and switch_mm(), 894 most likely) needs to ensure that the stack's page table entries 895 are populated before running on a possibly unpopulated stack. 896 897 - If the stack overflows into a guard page, something reasonable 898 should happen. The definition of "reasonable" is flexible, but 899 instantly rebooting without logging anything would be unfriendly. 900 901config VMAP_STACK 902 default y 903 bool "Use a virtually-mapped stack" 904 depends on HAVE_ARCH_VMAP_STACK && !KASAN 905 ---help--- 906 Enable this if you want the use virtually-mapped kernel stacks 907 with guard pages. This causes kernel stack overflows to be 908 caught immediately rather than causing difficult-to-diagnose 909 corruption. 910 911 This is presently incompatible with KASAN because KASAN expects 912 the stack to map directly to the KASAN shadow map using a formula 913 that is incorrect if the stack is in vmalloc space. 914 915config ARCH_OPTIONAL_KERNEL_RWX 916 def_bool n 917 918config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 919 def_bool n 920 921config ARCH_HAS_STRICT_KERNEL_RWX 922 def_bool n 923 924config STRICT_KERNEL_RWX 925 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 926 depends on ARCH_HAS_STRICT_KERNEL_RWX 927 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 928 help 929 If this is set, kernel text and rodata memory will be made read-only, 930 and non-text memory will be made non-executable. This provides 931 protection against certain security exploits (e.g. executing the heap 932 or modifying text) 933 934 These features are considered standard security practice these days. 935 You should say Y here in almost all cases. 936 937config ARCH_HAS_STRICT_MODULE_RWX 938 def_bool n 939 940config STRICT_MODULE_RWX 941 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 942 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 943 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 944 help 945 If this is set, module text and rodata memory will be made read-only, 946 and non-text memory will be made non-executable. This provides 947 protection against certain security exploits (e.g. writing to text) 948 949# select if the architecture provides an asm/dma-direct.h header 950config ARCH_HAS_PHYS_TO_DMA 951 bool 952 953config ARCH_HAS_REFCOUNT 954 bool 955 help 956 An architecture selects this when it has implemented refcount_t 957 using open coded assembly primitives that provide an optimized 958 refcount_t implementation, possibly at the expense of some full 959 refcount state checks of CONFIG_REFCOUNT_FULL=y. 960 961 The refcount overflow check behavior, however, must be retained. 962 Catching overflows is the primary security concern for protecting 963 against bugs in reference counts. 964 965config REFCOUNT_FULL 966 bool "Perform full reference count validation at the expense of speed" 967 help 968 Enabling this switches the refcounting infrastructure from a fast 969 unchecked atomic_t implementation to a fully state checked 970 implementation, which can be (slightly) slower but provides protections 971 against various use-after-free conditions that can be used in 972 security flaw exploits. 973 974source "kernel/gcov/Kconfig" 975