tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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kernel / arch / Kconfig
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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_CLK 276 bool 277 help 278 The <linux/clk.h> calls support software clock gating and 279 thus are a key power management tool on many systems. 280 281config HAVE_DMA_API_DEBUG 282 bool 283 284config HAVE_HW_BREAKPOINT 285 bool 286 depends on PERF_EVENTS 287 288config HAVE_MIXED_BREAKPOINTS_REGS 289 bool 290 depends on HAVE_HW_BREAKPOINT 291 help 292 Depending on the arch implementation of hardware breakpoints, 293 some of them have separate registers for data and instruction 294 breakpoints addresses, others have mixed registers to store 295 them but define the access type in a control register. 296 Select this option if your arch implements breakpoints under the 297 latter fashion. 298 299config HAVE_USER_RETURN_NOTIFIER 300 bool 301 302config HAVE_PERF_EVENTS_NMI 303 bool 304 help 305 System hardware can generate an NMI using the perf event 306 subsystem. Also has support for calculating CPU cycle events 307 to determine how many clock cycles in a given period. 308 309config HAVE_HARDLOCKUP_DETECTOR_PERF 310 bool 311 depends on HAVE_PERF_EVENTS_NMI 312 help 313 The arch chooses to use the generic perf-NMI-based hardlockup 314 detector. Must define HAVE_PERF_EVENTS_NMI. 315 316config HAVE_NMI_WATCHDOG 317 depends on HAVE_NMI 318 bool 319 help 320 The arch provides a low level NMI watchdog. It provides 321 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 322 323config HAVE_HARDLOCKUP_DETECTOR_ARCH 324 bool 325 select HAVE_NMI_WATCHDOG 326 help 327 The arch chooses to provide its own hardlockup detector, which is 328 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 329 interfaces and parameters provided by hardlockup detector subsystem. 330 331config HAVE_PERF_REGS 332 bool 333 help 334 Support selective register dumps for perf events. This includes 335 bit-mapping of each registers and a unique architecture id. 336 337config HAVE_PERF_USER_STACK_DUMP 338 bool 339 help 340 Support user stack dumps for perf event samples. This needs 341 access to the user stack pointer which is not unified across 342 architectures. 343 344config HAVE_ARCH_JUMP_LABEL 345 bool 346 347config HAVE_RCU_TABLE_FREE 348 bool 349 350config ARCH_HAVE_NMI_SAFE_CMPXCHG 351 bool 352 353config HAVE_ALIGNED_STRUCT_PAGE 354 bool 355 help 356 This makes sure that struct pages are double word aligned and that 357 e.g. the SLUB allocator can perform double word atomic operations 358 on a struct page for better performance. However selecting this 359 might increase the size of a struct page by a word. 360 361config HAVE_CMPXCHG_LOCAL 362 bool 363 364config HAVE_CMPXCHG_DOUBLE 365 bool 366 367config ARCH_WEAK_RELEASE_ACQUIRE 368 bool 369 370config ARCH_WANT_IPC_PARSE_VERSION 371 bool 372 373config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 374 bool 375 376config ARCH_WANT_OLD_COMPAT_IPC 377 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 378 bool 379 380config HAVE_ARCH_SECCOMP_FILTER 381 bool 382 help 383 An arch should select this symbol if it provides all of these things: 384 - syscall_get_arch() 385 - syscall_get_arguments() 386 - syscall_rollback() 387 - syscall_set_return_value() 388 - SIGSYS siginfo_t support 389 - secure_computing is called from a ptrace_event()-safe context 390 - secure_computing return value is checked and a return value of -1 391 results in the system call being skipped immediately. 392 - seccomp syscall wired up 393 394config SECCOMP_FILTER 395 def_bool y 396 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 397 help 398 Enable tasks to build secure computing environments defined 399 in terms of Berkeley Packet Filter programs which implement 400 task-defined system call filtering polices. 401 402 See Documentation/prctl/seccomp_filter.txt for details. 403 404config HAVE_GCC_PLUGINS 405 bool 406 help 407 An arch should select this symbol if it supports building with 408 GCC plugins. 409 410menuconfig GCC_PLUGINS 411 bool "GCC plugins" 412 depends on HAVE_GCC_PLUGINS 413 depends on !COMPILE_TEST 414 help 415 GCC plugins are loadable modules that provide extra features to the 416 compiler. They are useful for runtime instrumentation and static analysis. 417 418 See Documentation/gcc-plugins.txt for details. 419 420config GCC_PLUGIN_CYC_COMPLEXITY 421 bool "Compute the cyclomatic complexity of a function" if EXPERT 422 depends on GCC_PLUGINS 423 depends on !COMPILE_TEST 424 help 425 The complexity M of a function's control flow graph is defined as: 426 M = E - N + 2P 427 where 428 429 E = the number of edges 430 N = the number of nodes 431 P = the number of connected components (exit nodes). 432 433 Enabling this plugin reports the complexity to stderr during the 434 build. It mainly serves as a simple example of how to create a 435 gcc plugin for the kernel. 436 437config GCC_PLUGIN_SANCOV 438 bool 439 depends on GCC_PLUGINS 440 help 441 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 442 basic blocks. It supports all gcc versions with plugin support (from 443 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 444 by Dmitry Vyukov <dvyukov@google.com>. 445 446config GCC_PLUGIN_LATENT_ENTROPY 447 bool "Generate some entropy during boot and runtime" 448 depends on GCC_PLUGINS 449 help 450 By saying Y here the kernel will instrument some kernel code to 451 extract some entropy from both original and artificially created 452 program state. This will help especially embedded systems where 453 there is little 'natural' source of entropy normally. The cost 454 is some slowdown of the boot process (about 0.5%) and fork and 455 irq processing. 456 457 Note that entropy extracted this way is not cryptographically 458 secure! 459 460 This plugin was ported from grsecurity/PaX. More information at: 461 * https://grsecurity.net/ 462 * https://pax.grsecurity.net/ 463 464config GCC_PLUGIN_STRUCTLEAK 465 bool "Force initialization of variables containing userspace addresses" 466 depends on GCC_PLUGINS 467 help 468 This plugin zero-initializes any structures containing a 469 __user attribute. This can prevent some classes of information 470 exposures. 471 472 This plugin was ported from grsecurity/PaX. More information at: 473 * https://grsecurity.net/ 474 * https://pax.grsecurity.net/ 475 476config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 477 bool "Force initialize all struct type variables passed by reference" 478 depends on GCC_PLUGIN_STRUCTLEAK 479 help 480 Zero initialize any struct type local variable that may be passed by 481 reference without having been initialized. 482 483config GCC_PLUGIN_STRUCTLEAK_VERBOSE 484 bool "Report forcefully initialized variables" 485 depends on GCC_PLUGIN_STRUCTLEAK 486 depends on !COMPILE_TEST 487 help 488 This option will cause a warning to be printed each time the 489 structleak plugin finds a variable it thinks needs to be 490 initialized. Since not all existing initializers are detected 491 by the plugin, this can produce false positive warnings. 492 493config GCC_PLUGIN_RANDSTRUCT 494 bool "Randomize layout of sensitive kernel structures" 495 depends on GCC_PLUGINS 496 select MODVERSIONS if MODULES 497 help 498 If you say Y here, the layouts of structures that are entirely 499 function pointers (and have not been manually annotated with 500 __no_randomize_layout), or structures that have been explicitly 501 marked with __randomize_layout, will be randomized at compile-time. 502 This can introduce the requirement of an additional information 503 exposure vulnerability for exploits targeting these structure 504 types. 505 506 Enabling this feature will introduce some performance impact, 507 slightly increase memory usage, and prevent the use of forensic 508 tools like Volatility against the system (unless the kernel 509 source tree isn't cleaned after kernel installation). 510 511 The seed used for compilation is located at 512 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 513 a make clean to allow for external modules to be compiled with 514 the existing seed and will be removed by a make mrproper or 515 make distclean. 516 517 Note that the implementation requires gcc 4.7 or newer. 518 519 This plugin was ported from grsecurity/PaX. More information at: 520 * https://grsecurity.net/ 521 * https://pax.grsecurity.net/ 522 523config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 524 bool "Use cacheline-aware structure randomization" 525 depends on GCC_PLUGIN_RANDSTRUCT 526 depends on !COMPILE_TEST 527 help 528 If you say Y here, the RANDSTRUCT randomization will make a 529 best effort at restricting randomization to cacheline-sized 530 groups of elements. It will further not randomize bitfields 531 in structures. This reduces the performance hit of RANDSTRUCT 532 at the cost of weakened randomization. 533 534config HAVE_CC_STACKPROTECTOR 535 bool 536 help 537 An arch should select this symbol if: 538 - its compiler supports the -fstack-protector option 539 - it has implemented a stack canary (e.g. __stack_chk_guard) 540 541choice 542 prompt "Stack Protector buffer overflow detection" 543 depends on HAVE_CC_STACKPROTECTOR 544 default CC_STACKPROTECTOR_AUTO 545 help 546 This option turns on the "stack-protector" GCC feature. This 547 feature puts, at the beginning of functions, a canary value on 548 the stack just before the return address, and validates 549 the value just before actually returning. Stack based buffer 550 overflows (that need to overwrite this return address) now also 551 overwrite the canary, which gets detected and the attack is then 552 neutralized via a kernel panic. 553 554config CC_STACKPROTECTOR_NONE 555 bool "None" 556 help 557 Disable "stack-protector" GCC feature. 558 559config CC_STACKPROTECTOR_REGULAR 560 bool "Regular" 561 help 562 Functions will have the stack-protector canary logic added if they 563 have an 8-byte or larger character array on the stack. 564 565 This feature requires gcc version 4.2 or above, or a distribution 566 gcc with the feature backported ("-fstack-protector"). 567 568 On an x86 "defconfig" build, this feature adds canary checks to 569 about 3% of all kernel functions, which increases kernel code size 570 by about 0.3%. 571 572config CC_STACKPROTECTOR_STRONG 573 bool "Strong" 574 help 575 Functions will have the stack-protector canary logic added in any 576 of the following conditions: 577 578 - local variable's address used as part of the right hand side of an 579 assignment or function argument 580 - local variable is an array (or union containing an array), 581 regardless of array type or length 582 - uses register local variables 583 584 This feature requires gcc version 4.9 or above, or a distribution 585 gcc with the feature backported ("-fstack-protector-strong"). 586 587 On an x86 "defconfig" build, this feature adds canary checks to 588 about 20% of all kernel functions, which increases the kernel code 589 size by about 2%. 590 591config CC_STACKPROTECTOR_AUTO 592 bool "Automatic" 593 help 594 If the compiler supports it, the best available stack-protector 595 option will be chosen. 596 597endchoice 598 599config THIN_ARCHIVES 600 def_bool y 601 help 602 Select this if the architecture wants to use thin archives 603 instead of ld -r to create the built-in.o files. 604 605config LD_DEAD_CODE_DATA_ELIMINATION 606 bool 607 help 608 Select this if the architecture wants to do dead code and 609 data elimination with the linker by compiling with 610 -ffunction-sections -fdata-sections and linking with 611 --gc-sections. 612 613 This requires that the arch annotates or otherwise protects 614 its external entry points from being discarded. Linker scripts 615 must also merge .text.*, .data.*, and .bss.* correctly into 616 output sections. Care must be taken not to pull in unrelated 617 sections (e.g., '.text.init'). Typically '.' in section names 618 is used to distinguish them from label names / C identifiers. 619 620config HAVE_ARCH_WITHIN_STACK_FRAMES 621 bool 622 help 623 An architecture should select this if it can walk the kernel stack 624 frames to determine if an object is part of either the arguments 625 or local variables (i.e. that it excludes saved return addresses, 626 and similar) by implementing an inline arch_within_stack_frames(), 627 which is used by CONFIG_HARDENED_USERCOPY. 628 629config HAVE_CONTEXT_TRACKING 630 bool 631 help 632 Provide kernel/user boundaries probes necessary for subsystems 633 that need it, such as userspace RCU extended quiescent state. 634 Syscalls need to be wrapped inside user_exit()-user_enter() through 635 the slow path using TIF_NOHZ flag. Exceptions handlers must be 636 wrapped as well. Irqs are already protected inside 637 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 638 irq exit still need to be protected. 639 640config HAVE_VIRT_CPU_ACCOUNTING 641 bool 642 643config ARCH_HAS_SCALED_CPUTIME 644 bool 645 646config HAVE_VIRT_CPU_ACCOUNTING_GEN 647 bool 648 default y if 64BIT 649 help 650 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 651 Before enabling this option, arch code must be audited 652 to ensure there are no races in concurrent read/write of 653 cputime_t. For example, reading/writing 64-bit cputime_t on 654 some 32-bit arches may require multiple accesses, so proper 655 locking is needed to protect against concurrent accesses. 656 657 658config HAVE_IRQ_TIME_ACCOUNTING 659 bool 660 help 661 Archs need to ensure they use a high enough resolution clock to 662 support irq time accounting and then call enable_sched_clock_irqtime(). 663 664config HAVE_ARCH_TRANSPARENT_HUGEPAGE 665 bool 666 667config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 668 bool 669 670config HAVE_ARCH_HUGE_VMAP 671 bool 672 673config HAVE_ARCH_SOFT_DIRTY 674 bool 675 676config HAVE_MOD_ARCH_SPECIFIC 677 bool 678 help 679 The arch uses struct mod_arch_specific to store data. Many arches 680 just need a simple module loader without arch specific data - those 681 should not enable this. 682 683config MODULES_USE_ELF_RELA 684 bool 685 help 686 Modules only use ELF RELA relocations. Modules with ELF REL 687 relocations will give an error. 688 689config MODULES_USE_ELF_REL 690 bool 691 help 692 Modules only use ELF REL relocations. Modules with ELF RELA 693 relocations will give an error. 694 695config HAVE_UNDERSCORE_SYMBOL_PREFIX 696 bool 697 help 698 Some architectures generate an _ in front of C symbols; things like 699 module loading and assembly files need to know about this. 700 701config HAVE_IRQ_EXIT_ON_IRQ_STACK 702 bool 703 help 704 Architecture doesn't only execute the irq handler on the irq stack 705 but also irq_exit(). This way we can process softirqs on this irq 706 stack instead of switching to a new one when we call __do_softirq() 707 in the end of an hardirq. 708 This spares a stack switch and improves cache usage on softirq 709 processing. 710 711config PGTABLE_LEVELS 712 int 713 default 2 714 715config ARCH_HAS_ELF_RANDOMIZE 716 bool 717 help 718 An architecture supports choosing randomized locations for 719 stack, mmap, brk, and ET_DYN. Defined functions: 720 - arch_mmap_rnd() 721 - arch_randomize_brk() 722 723config HAVE_ARCH_MMAP_RND_BITS 724 bool 725 help 726 An arch should select this symbol if it supports setting a variable 727 number of bits for use in establishing the base address for mmap 728 allocations, has MMU enabled and provides values for both: 729 - ARCH_MMAP_RND_BITS_MIN 730 - ARCH_MMAP_RND_BITS_MAX 731 732config HAVE_EXIT_THREAD 733 bool 734 help 735 An architecture implements exit_thread. 736 737config ARCH_MMAP_RND_BITS_MIN 738 int 739 740config ARCH_MMAP_RND_BITS_MAX 741 int 742 743config ARCH_MMAP_RND_BITS_DEFAULT 744 int 745 746config ARCH_MMAP_RND_BITS 747 int "Number of bits to use for ASLR of mmap base address" if EXPERT 748 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 749 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 750 default ARCH_MMAP_RND_BITS_MIN 751 depends on HAVE_ARCH_MMAP_RND_BITS 752 help 753 This value can be used to select the number of bits to use to 754 determine the random offset to the base address of vma regions 755 resulting from mmap allocations. This value will be bounded 756 by the architecture's minimum and maximum supported values. 757 758 This value can be changed after boot using the 759 /proc/sys/vm/mmap_rnd_bits tunable 760 761config HAVE_ARCH_MMAP_RND_COMPAT_BITS 762 bool 763 help 764 An arch should select this symbol if it supports running applications 765 in compatibility mode, supports setting a variable number of bits for 766 use in establishing the base address for mmap allocations, has MMU 767 enabled and provides values for both: 768 - ARCH_MMAP_RND_COMPAT_BITS_MIN 769 - ARCH_MMAP_RND_COMPAT_BITS_MAX 770 771config ARCH_MMAP_RND_COMPAT_BITS_MIN 772 int 773 774config ARCH_MMAP_RND_COMPAT_BITS_MAX 775 int 776 777config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 778 int 779 780config ARCH_MMAP_RND_COMPAT_BITS 781 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 782 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 783 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 784 default ARCH_MMAP_RND_COMPAT_BITS_MIN 785 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 786 help 787 This value can be used to select the number of bits to use to 788 determine the random offset to the base address of vma regions 789 resulting from mmap allocations for compatible applications This 790 value will be bounded by the architecture's minimum and maximum 791 supported values. 792 793 This value can be changed after boot using the 794 /proc/sys/vm/mmap_rnd_compat_bits tunable 795 796config HAVE_ARCH_COMPAT_MMAP_BASES 797 bool 798 help 799 This allows 64bit applications to invoke 32-bit mmap() syscall 800 and vice-versa 32-bit applications to call 64-bit mmap(). 801 Required for applications doing different bitness syscalls. 802 803config HAVE_COPY_THREAD_TLS 804 bool 805 help 806 Architecture provides copy_thread_tls to accept tls argument via 807 normal C parameter passing, rather than extracting the syscall 808 argument from pt_regs. 809 810config HAVE_STACK_VALIDATION 811 bool 812 help 813 Architecture supports the 'objtool check' host tool command, which 814 performs compile-time stack metadata validation. 815 816config HAVE_RELIABLE_STACKTRACE 817 bool 818 help 819 Architecture has a save_stack_trace_tsk_reliable() function which 820 only returns a stack trace if it can guarantee the trace is reliable. 821 822config HAVE_ARCH_HASH 823 bool 824 default n 825 help 826 If this is set, the architecture provides an <asm/hash.h> 827 file which provides platform-specific implementations of some 828 functions in <linux/hash.h> or fs/namei.c. 829 830config ISA_BUS_API 831 def_bool ISA 832 833# 834# ABI hall of shame 835# 836config CLONE_BACKWARDS 837 bool 838 help 839 Architecture has tls passed as the 4th argument of clone(2), 840 not the 5th one. 841 842config CLONE_BACKWARDS2 843 bool 844 help 845 Architecture has the first two arguments of clone(2) swapped. 846 847config CLONE_BACKWARDS3 848 bool 849 help 850 Architecture has tls passed as the 3rd argument of clone(2), 851 not the 5th one. 852 853config ODD_RT_SIGACTION 854 bool 855 help 856 Architecture has unusual rt_sigaction(2) arguments 857 858config OLD_SIGSUSPEND 859 bool 860 help 861 Architecture has old sigsuspend(2) syscall, of one-argument variety 862 863config OLD_SIGSUSPEND3 864 bool 865 help 866 Even weirder antique ABI - three-argument sigsuspend(2) 867 868config OLD_SIGACTION 869 bool 870 help 871 Architecture has old sigaction(2) syscall. Nope, not the same 872 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 873 but fairly different variant of sigaction(2), thanks to OSF/1 874 compatibility... 875 876config COMPAT_OLD_SIGACTION 877 bool 878 879config ARCH_NO_COHERENT_DMA_MMAP 880 bool 881 882config CPU_NO_EFFICIENT_FFS 883 def_bool n 884 885config HAVE_ARCH_VMAP_STACK 886 def_bool n 887 help 888 An arch should select this symbol if it can support kernel stacks 889 in vmalloc space. This means: 890 891 - vmalloc space must be large enough to hold many kernel stacks. 892 This may rule out many 32-bit architectures. 893 894 - Stacks in vmalloc space need to work reliably. For example, if 895 vmap page tables are created on demand, either this mechanism 896 needs to work while the stack points to a virtual address with 897 unpopulated page tables or arch code (switch_to() and switch_mm(), 898 most likely) needs to ensure that the stack's page table entries 899 are populated before running on a possibly unpopulated stack. 900 901 - If the stack overflows into a guard page, something reasonable 902 should happen. The definition of "reasonable" is flexible, but 903 instantly rebooting without logging anything would be unfriendly. 904 905config VMAP_STACK 906 default y 907 bool "Use a virtually-mapped stack" 908 depends on HAVE_ARCH_VMAP_STACK && !KASAN 909 ---help--- 910 Enable this if you want the use virtually-mapped kernel stacks 911 with guard pages. This causes kernel stack overflows to be 912 caught immediately rather than causing difficult-to-diagnose 913 corruption. 914 915 This is presently incompatible with KASAN because KASAN expects 916 the stack to map directly to the KASAN shadow map using a formula 917 that is incorrect if the stack is in vmalloc space. 918 919config ARCH_OPTIONAL_KERNEL_RWX 920 def_bool n 921 922config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 923 def_bool n 924 925config ARCH_HAS_STRICT_KERNEL_RWX 926 def_bool n 927 928config STRICT_KERNEL_RWX 929 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 930 depends on ARCH_HAS_STRICT_KERNEL_RWX 931 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 932 help 933 If this is set, kernel text and rodata memory will be made read-only, 934 and non-text memory will be made non-executable. This provides 935 protection against certain security exploits (e.g. executing the heap 936 or modifying text) 937 938 These features are considered standard security practice these days. 939 You should say Y here in almost all cases. 940 941config ARCH_HAS_STRICT_MODULE_RWX 942 def_bool n 943 944config STRICT_MODULE_RWX 945 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 946 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 947 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 948 help 949 If this is set, module text and rodata memory will be made read-only, 950 and non-text memory will be made non-executable. This provides 951 protection against certain security exploits (e.g. writing to text) 952 953# select if the architecture provides an asm/dma-direct.h header 954config ARCH_HAS_PHYS_TO_DMA 955 bool 956 957config ARCH_HAS_REFCOUNT 958 bool 959 help 960 An architecture selects this when it has implemented refcount_t 961 using open coded assembly primitives that provide an optimized 962 refcount_t implementation, possibly at the expense of some full 963 refcount state checks of CONFIG_REFCOUNT_FULL=y. 964 965 The refcount overflow check behavior, however, must be retained. 966 Catching overflows is the primary security concern for protecting 967 against bugs in reference counts. 968 969config REFCOUNT_FULL 970 bool "Perform full reference count validation at the expense of speed" 971 help 972 Enabling this switches the refcounting infrastructure from a fast 973 unchecked atomic_t implementation to a fully state checked 974 implementation, which can be (slightly) slower but provides protections 975 against various use-after-free conditions that can be used in 976 security flaw exploits. 977 978source "kernel/gcov/Kconfig"