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 HOTPLUG_SMT 17 bool 18 19config OPROFILE 20 tristate "OProfile system profiling" 21 depends on PROFILING 22 depends on HAVE_OPROFILE 23 select RING_BUFFER 24 select RING_BUFFER_ALLOW_SWAP 25 help 26 OProfile is a profiling system capable of profiling the 27 whole system, include the kernel, kernel modules, libraries, 28 and applications. 29 30 If unsure, say N. 31 32config OPROFILE_EVENT_MULTIPLEX 33 bool "OProfile multiplexing support (EXPERIMENTAL)" 34 default n 35 depends on OPROFILE && X86 36 help 37 The number of hardware counters is limited. The multiplexing 38 feature enables OProfile to gather more events than counters 39 are provided by the hardware. This is realized by switching 40 between events at a user specified time interval. 41 42 If unsure, say N. 43 44config HAVE_OPROFILE 45 bool 46 47config OPROFILE_NMI_TIMER 48 def_bool y 49 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 50 51config KPROBES 52 bool "Kprobes" 53 depends on MODULES 54 depends on HAVE_KPROBES 55 select KALLSYMS 56 help 57 Kprobes allows you to trap at almost any kernel address and 58 execute a callback function. register_kprobe() establishes 59 a probepoint and specifies the callback. Kprobes is useful 60 for kernel debugging, non-intrusive instrumentation and testing. 61 If in doubt, say "N". 62 63config JUMP_LABEL 64 bool "Optimize very unlikely/likely branches" 65 depends on HAVE_ARCH_JUMP_LABEL 66 help 67 This option enables a transparent branch optimization that 68 makes certain almost-always-true or almost-always-false branch 69 conditions even cheaper to execute within the kernel. 70 71 Certain performance-sensitive kernel code, such as trace points, 72 scheduler functionality, networking code and KVM have such 73 branches and include support for this optimization technique. 74 75 If it is detected that the compiler has support for "asm goto", 76 the kernel will compile such branches with just a nop 77 instruction. When the condition flag is toggled to true, the 78 nop will be converted to a jump instruction to execute the 79 conditional block of instructions. 80 81 This technique lowers overhead and stress on the branch prediction 82 of the processor and generally makes the kernel faster. The update 83 of the condition is slower, but those are always very rare. 84 85 ( On 32-bit x86, the necessary options added to the compiler 86 flags may increase the size of the kernel slightly. ) 87 88config STATIC_KEYS_SELFTEST 89 bool "Static key selftest" 90 depends on JUMP_LABEL 91 help 92 Boot time self-test of the branch patching code. 93 94config OPTPROBES 95 def_bool y 96 depends on KPROBES && HAVE_OPTPROBES 97 select TASKS_RCU if PREEMPT 98 99config KPROBES_ON_FTRACE 100 def_bool y 101 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 102 depends on DYNAMIC_FTRACE_WITH_REGS 103 help 104 If function tracer is enabled and the arch supports full 105 passing of pt_regs to function tracing, then kprobes can 106 optimize on top of function tracing. 107 108config UPROBES 109 def_bool n 110 depends on ARCH_SUPPORTS_UPROBES 111 help 112 Uprobes is the user-space counterpart to kprobes: they 113 enable instrumentation applications (such as 'perf probe') 114 to establish unintrusive probes in user-space binaries and 115 libraries, by executing handler functions when the probes 116 are hit by user-space applications. 117 118 ( These probes come in the form of single-byte breakpoints, 119 managed by the kernel and kept transparent to the probed 120 application. ) 121 122config HAVE_64BIT_ALIGNED_ACCESS 123 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 124 help 125 Some architectures require 64 bit accesses to be 64 bit 126 aligned, which also requires structs containing 64 bit values 127 to be 64 bit aligned too. This includes some 32 bit 128 architectures which can do 64 bit accesses, as well as 64 bit 129 architectures without unaligned access. 130 131 This symbol should be selected by an architecture if 64 bit 132 accesses are required to be 64 bit aligned in this way even 133 though it is not a 64 bit architecture. 134 135 See Documentation/unaligned-memory-access.txt for more 136 information on the topic of unaligned memory accesses. 137 138config HAVE_EFFICIENT_UNALIGNED_ACCESS 139 bool 140 help 141 Some architectures are unable to perform unaligned accesses 142 without the use of get_unaligned/put_unaligned. Others are 143 unable to perform such accesses efficiently (e.g. trap on 144 unaligned access and require fixing it up in the exception 145 handler.) 146 147 This symbol should be selected by an architecture if it can 148 perform unaligned accesses efficiently to allow different 149 code paths to be selected for these cases. Some network 150 drivers, for example, could opt to not fix up alignment 151 problems with received packets if doing so would not help 152 much. 153 154 See Documentation/unaligned-memory-access.txt for more 155 information on the topic of unaligned memory accesses. 156 157config ARCH_USE_BUILTIN_BSWAP 158 bool 159 help 160 Modern versions of GCC (since 4.4) have builtin functions 161 for handling byte-swapping. Using these, instead of the old 162 inline assembler that the architecture code provides in the 163 __arch_bswapXX() macros, allows the compiler to see what's 164 happening and offers more opportunity for optimisation. In 165 particular, the compiler will be able to combine the byteswap 166 with a nearby load or store and use load-and-swap or 167 store-and-swap instructions if the architecture has them. It 168 should almost *never* result in code which is worse than the 169 hand-coded assembler in <asm/swab.h>. But just in case it 170 does, the use of the builtins is optional. 171 172 Any architecture with load-and-swap or store-and-swap 173 instructions should set this. And it shouldn't hurt to set it 174 on architectures that don't have such instructions. 175 176config KRETPROBES 177 def_bool y 178 depends on KPROBES && HAVE_KRETPROBES 179 180config USER_RETURN_NOTIFIER 181 bool 182 depends on HAVE_USER_RETURN_NOTIFIER 183 help 184 Provide a kernel-internal notification when a cpu is about to 185 switch to user mode. 186 187config HAVE_IOREMAP_PROT 188 bool 189 190config HAVE_KPROBES 191 bool 192 193config HAVE_KRETPROBES 194 bool 195 196config HAVE_OPTPROBES 197 bool 198 199config HAVE_KPROBES_ON_FTRACE 200 bool 201 202config HAVE_FUNCTION_ERROR_INJECTION 203 bool 204 205config HAVE_NMI 206 bool 207 208# 209# An arch should select this if it provides all these things: 210# 211# task_pt_regs() in asm/processor.h or asm/ptrace.h 212# arch_has_single_step() if there is hardware single-step support 213# arch_has_block_step() if there is hardware block-step support 214# asm/syscall.h supplying asm-generic/syscall.h interface 215# linux/regset.h user_regset interfaces 216# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 217# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 218# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 219# signal delivery calls tracehook_signal_handler() 220# 221config HAVE_ARCH_TRACEHOOK 222 bool 223 224config HAVE_DMA_CONTIGUOUS 225 bool 226 227config GENERIC_SMP_IDLE_THREAD 228 bool 229 230config GENERIC_IDLE_POLL_SETUP 231 bool 232 233config ARCH_HAS_FORTIFY_SOURCE 234 bool 235 help 236 An architecture should select this when it can successfully 237 build and run with CONFIG_FORTIFY_SOURCE. 238 239# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 240config ARCH_HAS_SET_MEMORY 241 bool 242 243# Select if arch init_task must go in the __init_task_data section 244config ARCH_TASK_STRUCT_ON_STACK 245 bool 246 247# Select if arch has its private alloc_task_struct() function 248config ARCH_TASK_STRUCT_ALLOCATOR 249 bool 250 251config HAVE_ARCH_THREAD_STRUCT_WHITELIST 252 bool 253 depends on !ARCH_TASK_STRUCT_ALLOCATOR 254 help 255 An architecture should select this to provide hardened usercopy 256 knowledge about what region of the thread_struct should be 257 whitelisted for copying to userspace. Normally this is only the 258 FPU registers. Specifically, arch_thread_struct_whitelist() 259 should be implemented. Without this, the entire thread_struct 260 field in task_struct will be left whitelisted. 261 262# Select if arch has its private alloc_thread_stack() function 263config ARCH_THREAD_STACK_ALLOCATOR 264 bool 265 266# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 267config ARCH_WANTS_DYNAMIC_TASK_STRUCT 268 bool 269 270config HAVE_REGS_AND_STACK_ACCESS_API 271 bool 272 help 273 This symbol should be selected by an architecure if it supports 274 the API needed to access registers and stack entries from pt_regs, 275 declared in asm/ptrace.h 276 For example the kprobes-based event tracer needs this API. 277 278config HAVE_RSEQ 279 bool 280 depends on HAVE_REGS_AND_STACK_ACCESS_API 281 help 282 This symbol should be selected by an architecture if it 283 supports an implementation of restartable sequences. 284 285config HAVE_CLK 286 bool 287 help 288 The <linux/clk.h> calls support software clock gating and 289 thus are a key power management tool on many systems. 290 291config HAVE_HW_BREAKPOINT 292 bool 293 depends on PERF_EVENTS 294 295config HAVE_MIXED_BREAKPOINTS_REGS 296 bool 297 depends on HAVE_HW_BREAKPOINT 298 help 299 Depending on the arch implementation of hardware breakpoints, 300 some of them have separate registers for data and instruction 301 breakpoints addresses, others have mixed registers to store 302 them but define the access type in a control register. 303 Select this option if your arch implements breakpoints under the 304 latter fashion. 305 306config HAVE_USER_RETURN_NOTIFIER 307 bool 308 309config HAVE_PERF_EVENTS_NMI 310 bool 311 help 312 System hardware can generate an NMI using the perf event 313 subsystem. Also has support for calculating CPU cycle events 314 to determine how many clock cycles in a given period. 315 316config HAVE_HARDLOCKUP_DETECTOR_PERF 317 bool 318 depends on HAVE_PERF_EVENTS_NMI 319 help 320 The arch chooses to use the generic perf-NMI-based hardlockup 321 detector. Must define HAVE_PERF_EVENTS_NMI. 322 323config HAVE_NMI_WATCHDOG 324 depends on HAVE_NMI 325 bool 326 help 327 The arch provides a low level NMI watchdog. It provides 328 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 329 330config HAVE_HARDLOCKUP_DETECTOR_ARCH 331 bool 332 select HAVE_NMI_WATCHDOG 333 help 334 The arch chooses to provide its own hardlockup detector, which is 335 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 336 interfaces and parameters provided by hardlockup detector subsystem. 337 338config HAVE_PERF_REGS 339 bool 340 help 341 Support selective register dumps for perf events. This includes 342 bit-mapping of each registers and a unique architecture id. 343 344config HAVE_PERF_USER_STACK_DUMP 345 bool 346 help 347 Support user stack dumps for perf event samples. This needs 348 access to the user stack pointer which is not unified across 349 architectures. 350 351config HAVE_ARCH_JUMP_LABEL 352 bool 353 354config HAVE_RCU_TABLE_FREE 355 bool 356 357config ARCH_HAVE_NMI_SAFE_CMPXCHG 358 bool 359 360config HAVE_ALIGNED_STRUCT_PAGE 361 bool 362 help 363 This makes sure that struct pages are double word aligned and that 364 e.g. the SLUB allocator can perform double word atomic operations 365 on a struct page for better performance. However selecting this 366 might increase the size of a struct page by a word. 367 368config HAVE_CMPXCHG_LOCAL 369 bool 370 371config HAVE_CMPXCHG_DOUBLE 372 bool 373 374config ARCH_WEAK_RELEASE_ACQUIRE 375 bool 376 377config ARCH_WANT_IPC_PARSE_VERSION 378 bool 379 380config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 381 bool 382 383config ARCH_WANT_OLD_COMPAT_IPC 384 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 385 bool 386 387config HAVE_ARCH_SECCOMP_FILTER 388 bool 389 help 390 An arch should select this symbol if it provides all of these things: 391 - syscall_get_arch() 392 - syscall_get_arguments() 393 - syscall_rollback() 394 - syscall_set_return_value() 395 - SIGSYS siginfo_t support 396 - secure_computing is called from a ptrace_event()-safe context 397 - secure_computing return value is checked and a return value of -1 398 results in the system call being skipped immediately. 399 - seccomp syscall wired up 400 401config SECCOMP_FILTER 402 def_bool y 403 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 404 help 405 Enable tasks to build secure computing environments defined 406 in terms of Berkeley Packet Filter programs which implement 407 task-defined system call filtering polices. 408 409 See Documentation/userspace-api/seccomp_filter.rst for details. 410 411preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC)) 412 413config PLUGIN_HOSTCC 414 string 415 default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" 416 help 417 Host compiler used to build GCC plugins. This can be $(HOSTCXX), 418 $(HOSTCC), or a null string if GCC plugin is unsupported. 419 420config HAVE_GCC_PLUGINS 421 bool 422 help 423 An arch should select this symbol if it supports building with 424 GCC plugins. 425 426menuconfig GCC_PLUGINS 427 bool "GCC plugins" 428 depends on HAVE_GCC_PLUGINS 429 depends on PLUGIN_HOSTCC != "" 430 help 431 GCC plugins are loadable modules that provide extra features to the 432 compiler. They are useful for runtime instrumentation and static analysis. 433 434 See Documentation/gcc-plugins.txt for details. 435 436config GCC_PLUGIN_CYC_COMPLEXITY 437 bool "Compute the cyclomatic complexity of a function" if EXPERT 438 depends on GCC_PLUGINS 439 depends on !COMPILE_TEST # too noisy 440 help 441 The complexity M of a function's control flow graph is defined as: 442 M = E - N + 2P 443 where 444 445 E = the number of edges 446 N = the number of nodes 447 P = the number of connected components (exit nodes). 448 449 Enabling this plugin reports the complexity to stderr during the 450 build. It mainly serves as a simple example of how to create a 451 gcc plugin for the kernel. 452 453config GCC_PLUGIN_SANCOV 454 bool 455 depends on GCC_PLUGINS 456 help 457 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 458 basic blocks. It supports all gcc versions with plugin support (from 459 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 460 by Dmitry Vyukov <dvyukov@google.com>. 461 462config GCC_PLUGIN_LATENT_ENTROPY 463 bool "Generate some entropy during boot and runtime" 464 depends on GCC_PLUGINS 465 help 466 By saying Y here the kernel will instrument some kernel code to 467 extract some entropy from both original and artificially created 468 program state. This will help especially embedded systems where 469 there is little 'natural' source of entropy normally. The cost 470 is some slowdown of the boot process (about 0.5%) and fork and 471 irq processing. 472 473 Note that entropy extracted this way is not cryptographically 474 secure! 475 476 This plugin was ported from grsecurity/PaX. More information at: 477 * https://grsecurity.net/ 478 * https://pax.grsecurity.net/ 479 480config GCC_PLUGIN_STRUCTLEAK 481 bool "Force initialization of variables containing userspace addresses" 482 depends on GCC_PLUGINS 483 # Currently STRUCTLEAK inserts initialization out of live scope of 484 # variables from KASAN point of view. This leads to KASAN false 485 # positive reports. Prohibit this combination for now. 486 depends on !KASAN_EXTRA 487 help 488 This plugin zero-initializes any structures containing a 489 __user attribute. This can prevent some classes of information 490 exposures. 491 492 This plugin was ported from grsecurity/PaX. More information at: 493 * https://grsecurity.net/ 494 * https://pax.grsecurity.net/ 495 496config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 497 bool "Force initialize all struct type variables passed by reference" 498 depends on GCC_PLUGIN_STRUCTLEAK 499 depends on !COMPILE_TEST 500 help 501 Zero initialize any struct type local variable that may be passed by 502 reference without having been initialized. 503 504config GCC_PLUGIN_STRUCTLEAK_VERBOSE 505 bool "Report forcefully initialized variables" 506 depends on GCC_PLUGIN_STRUCTLEAK 507 depends on !COMPILE_TEST # too noisy 508 help 509 This option will cause a warning to be printed each time the 510 structleak plugin finds a variable it thinks needs to be 511 initialized. Since not all existing initializers are detected 512 by the plugin, this can produce false positive warnings. 513 514config GCC_PLUGIN_RANDSTRUCT 515 bool "Randomize layout of sensitive kernel structures" 516 depends on GCC_PLUGINS 517 select MODVERSIONS if MODULES 518 help 519 If you say Y here, the layouts of structures that are entirely 520 function pointers (and have not been manually annotated with 521 __no_randomize_layout), or structures that have been explicitly 522 marked with __randomize_layout, will be randomized at compile-time. 523 This can introduce the requirement of an additional information 524 exposure vulnerability for exploits targeting these structure 525 types. 526 527 Enabling this feature will introduce some performance impact, 528 slightly increase memory usage, and prevent the use of forensic 529 tools like Volatility against the system (unless the kernel 530 source tree isn't cleaned after kernel installation). 531 532 The seed used for compilation is located at 533 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 534 a make clean to allow for external modules to be compiled with 535 the existing seed and will be removed by a make mrproper or 536 make distclean. 537 538 Note that the implementation requires gcc 4.7 or newer. 539 540 This plugin was ported from grsecurity/PaX. More information at: 541 * https://grsecurity.net/ 542 * https://pax.grsecurity.net/ 543 544config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 545 bool "Use cacheline-aware structure randomization" 546 depends on GCC_PLUGIN_RANDSTRUCT 547 depends on !COMPILE_TEST # do not reduce test coverage 548 help 549 If you say Y here, the RANDSTRUCT randomization will make a 550 best effort at restricting randomization to cacheline-sized 551 groups of elements. It will further not randomize bitfields 552 in structures. This reduces the performance hit of RANDSTRUCT 553 at the cost of weakened randomization. 554 555config HAVE_STACKPROTECTOR 556 bool 557 help 558 An arch should select this symbol if: 559 - it has implemented a stack canary (e.g. __stack_chk_guard) 560 561config CC_HAS_STACKPROTECTOR_NONE 562 def_bool $(cc-option,-fno-stack-protector) 563 564config STACKPROTECTOR 565 bool "Stack Protector buffer overflow detection" 566 depends on HAVE_STACKPROTECTOR 567 depends on $(cc-option,-fstack-protector) 568 default y 569 help 570 This option turns on the "stack-protector" GCC feature. This 571 feature puts, at the beginning of functions, a canary value on 572 the stack just before the return address, and validates 573 the value just before actually returning. Stack based buffer 574 overflows (that need to overwrite this return address) now also 575 overwrite the canary, which gets detected and the attack is then 576 neutralized via a kernel panic. 577 578 Functions will have the stack-protector canary logic added if they 579 have an 8-byte or larger character array on the stack. 580 581 This feature requires gcc version 4.2 or above, or a distribution 582 gcc with the feature backported ("-fstack-protector"). 583 584 On an x86 "defconfig" build, this feature adds canary checks to 585 about 3% of all kernel functions, which increases kernel code size 586 by about 0.3%. 587 588config STACKPROTECTOR_STRONG 589 bool "Strong Stack Protector" 590 depends on STACKPROTECTOR 591 depends on $(cc-option,-fstack-protector-strong) 592 default y 593 help 594 Functions will have the stack-protector canary logic added in any 595 of the following conditions: 596 597 - local variable's address used as part of the right hand side of an 598 assignment or function argument 599 - local variable is an array (or union containing an array), 600 regardless of array type or length 601 - uses register local variables 602 603 This feature requires gcc version 4.9 or above, or a distribution 604 gcc with the feature backported ("-fstack-protector-strong"). 605 606 On an x86 "defconfig" build, this feature adds canary checks to 607 about 20% of all kernel functions, which increases the kernel code 608 size by about 2%. 609 610config HAVE_ARCH_WITHIN_STACK_FRAMES 611 bool 612 help 613 An architecture should select this if it can walk the kernel stack 614 frames to determine if an object is part of either the arguments 615 or local variables (i.e. that it excludes saved return addresses, 616 and similar) by implementing an inline arch_within_stack_frames(), 617 which is used by CONFIG_HARDENED_USERCOPY. 618 619config HAVE_CONTEXT_TRACKING 620 bool 621 help 622 Provide kernel/user boundaries probes necessary for subsystems 623 that need it, such as userspace RCU extended quiescent state. 624 Syscalls need to be wrapped inside user_exit()-user_enter() through 625 the slow path using TIF_NOHZ flag. Exceptions handlers must be 626 wrapped as well. Irqs are already protected inside 627 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 628 irq exit still need to be protected. 629 630config HAVE_VIRT_CPU_ACCOUNTING 631 bool 632 633config ARCH_HAS_SCALED_CPUTIME 634 bool 635 636config HAVE_VIRT_CPU_ACCOUNTING_GEN 637 bool 638 default y if 64BIT 639 help 640 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 641 Before enabling this option, arch code must be audited 642 to ensure there are no races in concurrent read/write of 643 cputime_t. For example, reading/writing 64-bit cputime_t on 644 some 32-bit arches may require multiple accesses, so proper 645 locking is needed to protect against concurrent accesses. 646 647 648config HAVE_IRQ_TIME_ACCOUNTING 649 bool 650 help 651 Archs need to ensure they use a high enough resolution clock to 652 support irq time accounting and then call enable_sched_clock_irqtime(). 653 654config HAVE_ARCH_TRANSPARENT_HUGEPAGE 655 bool 656 657config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 658 bool 659 660config HAVE_ARCH_HUGE_VMAP 661 bool 662 663config HAVE_ARCH_SOFT_DIRTY 664 bool 665 666config HAVE_MOD_ARCH_SPECIFIC 667 bool 668 help 669 The arch uses struct mod_arch_specific to store data. Many arches 670 just need a simple module loader without arch specific data - those 671 should not enable this. 672 673config MODULES_USE_ELF_RELA 674 bool 675 help 676 Modules only use ELF RELA relocations. Modules with ELF REL 677 relocations will give an error. 678 679config MODULES_USE_ELF_REL 680 bool 681 help 682 Modules only use ELF REL relocations. Modules with ELF RELA 683 relocations will give an error. 684 685config HAVE_IRQ_EXIT_ON_IRQ_STACK 686 bool 687 help 688 Architecture doesn't only execute the irq handler on the irq stack 689 but also irq_exit(). This way we can process softirqs on this irq 690 stack instead of switching to a new one when we call __do_softirq() 691 in the end of an hardirq. 692 This spares a stack switch and improves cache usage on softirq 693 processing. 694 695config PGTABLE_LEVELS 696 int 697 default 2 698 699config ARCH_HAS_ELF_RANDOMIZE 700 bool 701 help 702 An architecture supports choosing randomized locations for 703 stack, mmap, brk, and ET_DYN. Defined functions: 704 - arch_mmap_rnd() 705 - arch_randomize_brk() 706 707config HAVE_ARCH_MMAP_RND_BITS 708 bool 709 help 710 An arch should select this symbol if it supports setting a variable 711 number of bits for use in establishing the base address for mmap 712 allocations, has MMU enabled and provides values for both: 713 - ARCH_MMAP_RND_BITS_MIN 714 - ARCH_MMAP_RND_BITS_MAX 715 716config HAVE_EXIT_THREAD 717 bool 718 help 719 An architecture implements exit_thread. 720 721config ARCH_MMAP_RND_BITS_MIN 722 int 723 724config ARCH_MMAP_RND_BITS_MAX 725 int 726 727config ARCH_MMAP_RND_BITS_DEFAULT 728 int 729 730config ARCH_MMAP_RND_BITS 731 int "Number of bits to use for ASLR of mmap base address" if EXPERT 732 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 733 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 734 default ARCH_MMAP_RND_BITS_MIN 735 depends on HAVE_ARCH_MMAP_RND_BITS 736 help 737 This value can be used to select the number of bits to use to 738 determine the random offset to the base address of vma regions 739 resulting from mmap allocations. This value will be bounded 740 by the architecture's minimum and maximum supported values. 741 742 This value can be changed after boot using the 743 /proc/sys/vm/mmap_rnd_bits tunable 744 745config HAVE_ARCH_MMAP_RND_COMPAT_BITS 746 bool 747 help 748 An arch should select this symbol if it supports running applications 749 in compatibility mode, supports setting a variable number of bits for 750 use in establishing the base address for mmap allocations, has MMU 751 enabled and provides values for both: 752 - ARCH_MMAP_RND_COMPAT_BITS_MIN 753 - ARCH_MMAP_RND_COMPAT_BITS_MAX 754 755config ARCH_MMAP_RND_COMPAT_BITS_MIN 756 int 757 758config ARCH_MMAP_RND_COMPAT_BITS_MAX 759 int 760 761config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 762 int 763 764config ARCH_MMAP_RND_COMPAT_BITS 765 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 766 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 767 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 768 default ARCH_MMAP_RND_COMPAT_BITS_MIN 769 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 770 help 771 This value can be used to select the number of bits to use to 772 determine the random offset to the base address of vma regions 773 resulting from mmap allocations for compatible applications This 774 value will be bounded by the architecture's minimum and maximum 775 supported values. 776 777 This value can be changed after boot using the 778 /proc/sys/vm/mmap_rnd_compat_bits tunable 779 780config HAVE_ARCH_COMPAT_MMAP_BASES 781 bool 782 help 783 This allows 64bit applications to invoke 32-bit mmap() syscall 784 and vice-versa 32-bit applications to call 64-bit mmap(). 785 Required for applications doing different bitness syscalls. 786 787config HAVE_COPY_THREAD_TLS 788 bool 789 help 790 Architecture provides copy_thread_tls to accept tls argument via 791 normal C parameter passing, rather than extracting the syscall 792 argument from pt_regs. 793 794config HAVE_STACK_VALIDATION 795 bool 796 help 797 Architecture supports the 'objtool check' host tool command, which 798 performs compile-time stack metadata validation. 799 800config HAVE_RELIABLE_STACKTRACE 801 bool 802 help 803 Architecture has a save_stack_trace_tsk_reliable() function which 804 only returns a stack trace if it can guarantee the trace is reliable. 805 806config HAVE_ARCH_HASH 807 bool 808 default n 809 help 810 If this is set, the architecture provides an <asm/hash.h> 811 file which provides platform-specific implementations of some 812 functions in <linux/hash.h> or fs/namei.c. 813 814config ISA_BUS_API 815 def_bool ISA 816 817# 818# ABI hall of shame 819# 820config CLONE_BACKWARDS 821 bool 822 help 823 Architecture has tls passed as the 4th argument of clone(2), 824 not the 5th one. 825 826config CLONE_BACKWARDS2 827 bool 828 help 829 Architecture has the first two arguments of clone(2) swapped. 830 831config CLONE_BACKWARDS3 832 bool 833 help 834 Architecture has tls passed as the 3rd argument of clone(2), 835 not the 5th one. 836 837config ODD_RT_SIGACTION 838 bool 839 help 840 Architecture has unusual rt_sigaction(2) arguments 841 842config OLD_SIGSUSPEND 843 bool 844 help 845 Architecture has old sigsuspend(2) syscall, of one-argument variety 846 847config OLD_SIGSUSPEND3 848 bool 849 help 850 Even weirder antique ABI - three-argument sigsuspend(2) 851 852config OLD_SIGACTION 853 bool 854 help 855 Architecture has old sigaction(2) syscall. Nope, not the same 856 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 857 but fairly different variant of sigaction(2), thanks to OSF/1 858 compatibility... 859 860config COMPAT_OLD_SIGACTION 861 bool 862 863config 64BIT_TIME 864 def_bool ARCH_HAS_64BIT_TIME 865 help 866 This should be selected by all architectures that need to support 867 new system calls with a 64-bit time_t. This is relevant on all 32-bit 868 architectures, and 64-bit architectures as part of compat syscall 869 handling. 870 871config COMPAT_32BIT_TIME 872 def_bool (!64BIT && 64BIT_TIME) || COMPAT 873 help 874 This enables 32 bit time_t support in addition to 64 bit time_t support. 875 This is relevant on all 32-bit architectures, and 64-bit architectures 876 as part of compat syscall handling. 877 878config ARCH_NO_COHERENT_DMA_MMAP 879 bool 880 881config CPU_NO_EFFICIENT_FFS 882 def_bool n 883 884config HAVE_ARCH_VMAP_STACK 885 def_bool n 886 help 887 An arch should select this symbol if it can support kernel stacks 888 in vmalloc space. This means: 889 890 - vmalloc space must be large enough to hold many kernel stacks. 891 This may rule out many 32-bit architectures. 892 893 - Stacks in vmalloc space need to work reliably. For example, if 894 vmap page tables are created on demand, either this mechanism 895 needs to work while the stack points to a virtual address with 896 unpopulated page tables or arch code (switch_to() and switch_mm(), 897 most likely) needs to ensure that the stack's page table entries 898 are populated before running on a possibly unpopulated stack. 899 900 - If the stack overflows into a guard page, something reasonable 901 should happen. The definition of "reasonable" is flexible, but 902 instantly rebooting without logging anything would be unfriendly. 903 904config VMAP_STACK 905 default y 906 bool "Use a virtually-mapped stack" 907 depends on HAVE_ARCH_VMAP_STACK && !KASAN 908 ---help--- 909 Enable this if you want the use virtually-mapped kernel stacks 910 with guard pages. This causes kernel stack overflows to be 911 caught immediately rather than causing difficult-to-diagnose 912 corruption. 913 914 This is presently incompatible with KASAN because KASAN expects 915 the stack to map directly to the KASAN shadow map using a formula 916 that is incorrect if the stack is in vmalloc space. 917 918config ARCH_OPTIONAL_KERNEL_RWX 919 def_bool n 920 921config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 922 def_bool n 923 924config ARCH_HAS_STRICT_KERNEL_RWX 925 def_bool n 926 927config STRICT_KERNEL_RWX 928 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 929 depends on ARCH_HAS_STRICT_KERNEL_RWX 930 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 931 help 932 If this is set, kernel text and rodata memory will be made read-only, 933 and non-text memory will be made non-executable. This provides 934 protection against certain security exploits (e.g. executing the heap 935 or modifying text) 936 937 These features are considered standard security practice these days. 938 You should say Y here in almost all cases. 939 940config ARCH_HAS_STRICT_MODULE_RWX 941 def_bool n 942 943config STRICT_MODULE_RWX 944 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 945 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 946 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 947 help 948 If this is set, module text and rodata memory will be made read-only, 949 and non-text memory will be made non-executable. This provides 950 protection against certain security exploits (e.g. writing to text) 951 952# select if the architecture provides an asm/dma-direct.h header 953config ARCH_HAS_PHYS_TO_DMA 954 bool 955 956config ARCH_HAS_REFCOUNT 957 bool 958 help 959 An architecture selects this when it has implemented refcount_t 960 using open coded assembly primitives that provide an optimized 961 refcount_t implementation, possibly at the expense of some full 962 refcount state checks of CONFIG_REFCOUNT_FULL=y. 963 964 The refcount overflow check behavior, however, must be retained. 965 Catching overflows is the primary security concern for protecting 966 against bugs in reference counts. 967 968config REFCOUNT_FULL 969 bool "Perform full reference count validation at the expense of speed" 970 help 971 Enabling this switches the refcounting infrastructure from a fast 972 unchecked atomic_t implementation to a fully state checked 973 implementation, which can be (slightly) slower but provides protections 974 against various use-after-free conditions that can be used in 975 security flaw exploits. 976 977source "kernel/gcov/Kconfig" 978