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/prctl/seccomp_filter.txt for details. 407 408config HAVE_GCC_PLUGINS 409 bool 410 help 411 An arch should select this symbol if it supports building with 412 GCC plugins. 413 414menuconfig GCC_PLUGINS 415 bool "GCC plugins" 416 depends on HAVE_GCC_PLUGINS 417 depends on !COMPILE_TEST 418 help 419 GCC plugins are loadable modules that provide extra features to the 420 compiler. They are useful for runtime instrumentation and static analysis. 421 422 See Documentation/gcc-plugins.txt for details. 423 424config GCC_PLUGIN_CYC_COMPLEXITY 425 bool "Compute the cyclomatic complexity of a function" if EXPERT 426 depends on GCC_PLUGINS 427 depends on !COMPILE_TEST 428 help 429 The complexity M of a function's control flow graph is defined as: 430 M = E - N + 2P 431 where 432 433 E = the number of edges 434 N = the number of nodes 435 P = the number of connected components (exit nodes). 436 437 Enabling this plugin reports the complexity to stderr during the 438 build. It mainly serves as a simple example of how to create a 439 gcc plugin for the kernel. 440 441config GCC_PLUGIN_SANCOV 442 bool 443 depends on GCC_PLUGINS 444 help 445 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 446 basic blocks. It supports all gcc versions with plugin support (from 447 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 448 by Dmitry Vyukov <dvyukov@google.com>. 449 450config GCC_PLUGIN_LATENT_ENTROPY 451 bool "Generate some entropy during boot and runtime" 452 depends on GCC_PLUGINS 453 help 454 By saying Y here the kernel will instrument some kernel code to 455 extract some entropy from both original and artificially created 456 program state. This will help especially embedded systems where 457 there is little 'natural' source of entropy normally. The cost 458 is some slowdown of the boot process (about 0.5%) and fork and 459 irq processing. 460 461 Note that entropy extracted this way is not cryptographically 462 secure! 463 464 This plugin was ported from grsecurity/PaX. More information at: 465 * https://grsecurity.net/ 466 * https://pax.grsecurity.net/ 467 468config GCC_PLUGIN_STRUCTLEAK 469 bool "Force initialization of variables containing userspace addresses" 470 depends on GCC_PLUGINS 471 # Currently STRUCTLEAK inserts initialization out of live scope of 472 # variables from KASAN point of view. This leads to KASAN false 473 # positive reports. Prohibit this combination for now. 474 depends on !KASAN_EXTRA 475 help 476 This plugin zero-initializes any structures containing a 477 __user attribute. This can prevent some classes of information 478 exposures. 479 480 This plugin was ported from grsecurity/PaX. More information at: 481 * https://grsecurity.net/ 482 * https://pax.grsecurity.net/ 483 484config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 485 bool "Force initialize all struct type variables passed by reference" 486 depends on GCC_PLUGIN_STRUCTLEAK 487 help 488 Zero initialize any struct type local variable that may be passed by 489 reference without having been initialized. 490 491config GCC_PLUGIN_STRUCTLEAK_VERBOSE 492 bool "Report forcefully initialized variables" 493 depends on GCC_PLUGIN_STRUCTLEAK 494 depends on !COMPILE_TEST 495 help 496 This option will cause a warning to be printed each time the 497 structleak plugin finds a variable it thinks needs to be 498 initialized. Since not all existing initializers are detected 499 by the plugin, this can produce false positive warnings. 500 501config GCC_PLUGIN_RANDSTRUCT 502 bool "Randomize layout of sensitive kernel structures" 503 depends on GCC_PLUGINS 504 select MODVERSIONS if MODULES 505 help 506 If you say Y here, the layouts of structures that are entirely 507 function pointers (and have not been manually annotated with 508 __no_randomize_layout), or structures that have been explicitly 509 marked with __randomize_layout, will be randomized at compile-time. 510 This can introduce the requirement of an additional information 511 exposure vulnerability for exploits targeting these structure 512 types. 513 514 Enabling this feature will introduce some performance impact, 515 slightly increase memory usage, and prevent the use of forensic 516 tools like Volatility against the system (unless the kernel 517 source tree isn't cleaned after kernel installation). 518 519 The seed used for compilation is located at 520 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 521 a make clean to allow for external modules to be compiled with 522 the existing seed and will be removed by a make mrproper or 523 make distclean. 524 525 Note that the implementation requires gcc 4.7 or newer. 526 527 This plugin was ported from grsecurity/PaX. More information at: 528 * https://grsecurity.net/ 529 * https://pax.grsecurity.net/ 530 531config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 532 bool "Use cacheline-aware structure randomization" 533 depends on GCC_PLUGIN_RANDSTRUCT 534 depends on !COMPILE_TEST 535 help 536 If you say Y here, the RANDSTRUCT randomization will make a 537 best effort at restricting randomization to cacheline-sized 538 groups of elements. It will further not randomize bitfields 539 in structures. This reduces the performance hit of RANDSTRUCT 540 at the cost of weakened randomization. 541 542config HAVE_CC_STACKPROTECTOR 543 bool 544 help 545 An arch should select this symbol if: 546 - its compiler supports the -fstack-protector option 547 - it has implemented a stack canary (e.g. __stack_chk_guard) 548 549choice 550 prompt "Stack Protector buffer overflow detection" 551 depends on HAVE_CC_STACKPROTECTOR 552 default CC_STACKPROTECTOR_AUTO 553 help 554 This option turns on the "stack-protector" GCC feature. This 555 feature puts, at the beginning of functions, a canary value on 556 the stack just before the return address, and validates 557 the value just before actually returning. Stack based buffer 558 overflows (that need to overwrite this return address) now also 559 overwrite the canary, which gets detected and the attack is then 560 neutralized via a kernel panic. 561 562config CC_STACKPROTECTOR_NONE 563 bool "None" 564 help 565 Disable "stack-protector" GCC feature. 566 567config CC_STACKPROTECTOR_REGULAR 568 bool "Regular" 569 help 570 Functions will have the stack-protector canary logic added if they 571 have an 8-byte or larger character array on the stack. 572 573 This feature requires gcc version 4.2 or above, or a distribution 574 gcc with the feature backported ("-fstack-protector"). 575 576 On an x86 "defconfig" build, this feature adds canary checks to 577 about 3% of all kernel functions, which increases kernel code size 578 by about 0.3%. 579 580config CC_STACKPROTECTOR_STRONG 581 bool "Strong" 582 help 583 Functions will have the stack-protector canary logic added in any 584 of the following conditions: 585 586 - local variable's address used as part of the right hand side of an 587 assignment or function argument 588 - local variable is an array (or union containing an array), 589 regardless of array type or length 590 - uses register local variables 591 592 This feature requires gcc version 4.9 or above, or a distribution 593 gcc with the feature backported ("-fstack-protector-strong"). 594 595 On an x86 "defconfig" build, this feature adds canary checks to 596 about 20% of all kernel functions, which increases the kernel code 597 size by about 2%. 598 599config CC_STACKPROTECTOR_AUTO 600 bool "Automatic" 601 help 602 If the compiler supports it, the best available stack-protector 603 option will be chosen. 604 605endchoice 606 607config LD_DEAD_CODE_DATA_ELIMINATION 608 bool 609 help 610 Select this if the architecture wants to do dead code and 611 data elimination with the linker by compiling with 612 -ffunction-sections -fdata-sections and linking with 613 --gc-sections. 614 615 This requires that the arch annotates or otherwise protects 616 its external entry points from being discarded. Linker scripts 617 must also merge .text.*, .data.*, and .bss.* correctly into 618 output sections. Care must be taken not to pull in unrelated 619 sections (e.g., '.text.init'). Typically '.' in section names 620 is used to distinguish them from label names / C identifiers. 621 622config HAVE_ARCH_WITHIN_STACK_FRAMES 623 bool 624 help 625 An architecture should select this if it can walk the kernel stack 626 frames to determine if an object is part of either the arguments 627 or local variables (i.e. that it excludes saved return addresses, 628 and similar) by implementing an inline arch_within_stack_frames(), 629 which is used by CONFIG_HARDENED_USERCOPY. 630 631config HAVE_CONTEXT_TRACKING 632 bool 633 help 634 Provide kernel/user boundaries probes necessary for subsystems 635 that need it, such as userspace RCU extended quiescent state. 636 Syscalls need to be wrapped inside user_exit()-user_enter() through 637 the slow path using TIF_NOHZ flag. Exceptions handlers must be 638 wrapped as well. Irqs are already protected inside 639 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 640 irq exit still need to be protected. 641 642config HAVE_VIRT_CPU_ACCOUNTING 643 bool 644 645config ARCH_HAS_SCALED_CPUTIME 646 bool 647 648config HAVE_VIRT_CPU_ACCOUNTING_GEN 649 bool 650 default y if 64BIT 651 help 652 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 653 Before enabling this option, arch code must be audited 654 to ensure there are no races in concurrent read/write of 655 cputime_t. For example, reading/writing 64-bit cputime_t on 656 some 32-bit arches may require multiple accesses, so proper 657 locking is needed to protect against concurrent accesses. 658 659 660config HAVE_IRQ_TIME_ACCOUNTING 661 bool 662 help 663 Archs need to ensure they use a high enough resolution clock to 664 support irq time accounting and then call enable_sched_clock_irqtime(). 665 666config HAVE_ARCH_TRANSPARENT_HUGEPAGE 667 bool 668 669config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 670 bool 671 672config HAVE_ARCH_HUGE_VMAP 673 bool 674 675config HAVE_ARCH_SOFT_DIRTY 676 bool 677 678config HAVE_MOD_ARCH_SPECIFIC 679 bool 680 help 681 The arch uses struct mod_arch_specific to store data. Many arches 682 just need a simple module loader without arch specific data - those 683 should not enable this. 684 685config MODULES_USE_ELF_RELA 686 bool 687 help 688 Modules only use ELF RELA relocations. Modules with ELF REL 689 relocations will give an error. 690 691config MODULES_USE_ELF_REL 692 bool 693 help 694 Modules only use ELF REL relocations. Modules with ELF RELA 695 relocations will give an error. 696 697config HAVE_UNDERSCORE_SYMBOL_PREFIX 698 bool 699 help 700 Some architectures generate an _ in front of C symbols; things like 701 module loading and assembly files need to know about this. 702 703config HAVE_IRQ_EXIT_ON_IRQ_STACK 704 bool 705 help 706 Architecture doesn't only execute the irq handler on the irq stack 707 but also irq_exit(). This way we can process softirqs on this irq 708 stack instead of switching to a new one when we call __do_softirq() 709 in the end of an hardirq. 710 This spares a stack switch and improves cache usage on softirq 711 processing. 712 713config PGTABLE_LEVELS 714 int 715 default 2 716 717config ARCH_HAS_ELF_RANDOMIZE 718 bool 719 help 720 An architecture supports choosing randomized locations for 721 stack, mmap, brk, and ET_DYN. Defined functions: 722 - arch_mmap_rnd() 723 - arch_randomize_brk() 724 725config HAVE_ARCH_MMAP_RND_BITS 726 bool 727 help 728 An arch should select this symbol if it supports setting a variable 729 number of bits for use in establishing the base address for mmap 730 allocations, has MMU enabled and provides values for both: 731 - ARCH_MMAP_RND_BITS_MIN 732 - ARCH_MMAP_RND_BITS_MAX 733 734config HAVE_EXIT_THREAD 735 bool 736 help 737 An architecture implements exit_thread. 738 739config ARCH_MMAP_RND_BITS_MIN 740 int 741 742config ARCH_MMAP_RND_BITS_MAX 743 int 744 745config ARCH_MMAP_RND_BITS_DEFAULT 746 int 747 748config ARCH_MMAP_RND_BITS 749 int "Number of bits to use for ASLR of mmap base address" if EXPERT 750 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 751 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 752 default ARCH_MMAP_RND_BITS_MIN 753 depends on HAVE_ARCH_MMAP_RND_BITS 754 help 755 This value can be used to select the number of bits to use to 756 determine the random offset to the base address of vma regions 757 resulting from mmap allocations. This value will be bounded 758 by the architecture's minimum and maximum supported values. 759 760 This value can be changed after boot using the 761 /proc/sys/vm/mmap_rnd_bits tunable 762 763config HAVE_ARCH_MMAP_RND_COMPAT_BITS 764 bool 765 help 766 An arch should select this symbol if it supports running applications 767 in compatibility mode, supports setting a variable number of bits for 768 use in establishing the base address for mmap allocations, has MMU 769 enabled and provides values for both: 770 - ARCH_MMAP_RND_COMPAT_BITS_MIN 771 - ARCH_MMAP_RND_COMPAT_BITS_MAX 772 773config ARCH_MMAP_RND_COMPAT_BITS_MIN 774 int 775 776config ARCH_MMAP_RND_COMPAT_BITS_MAX 777 int 778 779config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 780 int 781 782config ARCH_MMAP_RND_COMPAT_BITS 783 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 784 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 785 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 786 default ARCH_MMAP_RND_COMPAT_BITS_MIN 787 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 788 help 789 This value can be used to select the number of bits to use to 790 determine the random offset to the base address of vma regions 791 resulting from mmap allocations for compatible applications This 792 value will be bounded by the architecture's minimum and maximum 793 supported values. 794 795 This value can be changed after boot using the 796 /proc/sys/vm/mmap_rnd_compat_bits tunable 797 798config HAVE_ARCH_COMPAT_MMAP_BASES 799 bool 800 help 801 This allows 64bit applications to invoke 32-bit mmap() syscall 802 and vice-versa 32-bit applications to call 64-bit mmap(). 803 Required for applications doing different bitness syscalls. 804 805config HAVE_COPY_THREAD_TLS 806 bool 807 help 808 Architecture provides copy_thread_tls to accept tls argument via 809 normal C parameter passing, rather than extracting the syscall 810 argument from pt_regs. 811 812config HAVE_STACK_VALIDATION 813 bool 814 help 815 Architecture supports the 'objtool check' host tool command, which 816 performs compile-time stack metadata validation. 817 818config HAVE_RELIABLE_STACKTRACE 819 bool 820 help 821 Architecture has a save_stack_trace_tsk_reliable() function which 822 only returns a stack trace if it can guarantee the trace is reliable. 823 824config HAVE_ARCH_HASH 825 bool 826 default n 827 help 828 If this is set, the architecture provides an <asm/hash.h> 829 file which provides platform-specific implementations of some 830 functions in <linux/hash.h> or fs/namei.c. 831 832config ISA_BUS_API 833 def_bool ISA 834 835# 836# ABI hall of shame 837# 838config CLONE_BACKWARDS 839 bool 840 help 841 Architecture has tls passed as the 4th argument of clone(2), 842 not the 5th one. 843 844config CLONE_BACKWARDS2 845 bool 846 help 847 Architecture has the first two arguments of clone(2) swapped. 848 849config CLONE_BACKWARDS3 850 bool 851 help 852 Architecture has tls passed as the 3rd argument of clone(2), 853 not the 5th one. 854 855config ODD_RT_SIGACTION 856 bool 857 help 858 Architecture has unusual rt_sigaction(2) arguments 859 860config OLD_SIGSUSPEND 861 bool 862 help 863 Architecture has old sigsuspend(2) syscall, of one-argument variety 864 865config OLD_SIGSUSPEND3 866 bool 867 help 868 Even weirder antique ABI - three-argument sigsuspend(2) 869 870config OLD_SIGACTION 871 bool 872 help 873 Architecture has old sigaction(2) syscall. Nope, not the same 874 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 875 but fairly different variant of sigaction(2), thanks to OSF/1 876 compatibility... 877 878config COMPAT_OLD_SIGACTION 879 bool 880 881config 64BIT_TIME 882 def_bool ARCH_HAS_64BIT_TIME 883 help 884 This should be selected by all architectures that need to support 885 new system calls with a 64-bit time_t. This is relevant on all 32-bit 886 architectures, and 64-bit architectures as part of compat syscall 887 handling. 888 889config COMPAT_32BIT_TIME 890 def_bool (!64BIT && 64BIT_TIME) || COMPAT 891 help 892 This enables 32 bit time_t support in addition to 64 bit time_t support. 893 This is relevant on all 32-bit architectures, and 64-bit architectures 894 as part of compat syscall handling. 895 896config ARCH_NO_COHERENT_DMA_MMAP 897 bool 898 899config CPU_NO_EFFICIENT_FFS 900 def_bool n 901 902config HAVE_ARCH_VMAP_STACK 903 def_bool n 904 help 905 An arch should select this symbol if it can support kernel stacks 906 in vmalloc space. This means: 907 908 - vmalloc space must be large enough to hold many kernel stacks. 909 This may rule out many 32-bit architectures. 910 911 - Stacks in vmalloc space need to work reliably. For example, if 912 vmap page tables are created on demand, either this mechanism 913 needs to work while the stack points to a virtual address with 914 unpopulated page tables or arch code (switch_to() and switch_mm(), 915 most likely) needs to ensure that the stack's page table entries 916 are populated before running on a possibly unpopulated stack. 917 918 - If the stack overflows into a guard page, something reasonable 919 should happen. The definition of "reasonable" is flexible, but 920 instantly rebooting without logging anything would be unfriendly. 921 922config VMAP_STACK 923 default y 924 bool "Use a virtually-mapped stack" 925 depends on HAVE_ARCH_VMAP_STACK && !KASAN 926 ---help--- 927 Enable this if you want the use virtually-mapped kernel stacks 928 with guard pages. This causes kernel stack overflows to be 929 caught immediately rather than causing difficult-to-diagnose 930 corruption. 931 932 This is presently incompatible with KASAN because KASAN expects 933 the stack to map directly to the KASAN shadow map using a formula 934 that is incorrect if the stack is in vmalloc space. 935 936config ARCH_OPTIONAL_KERNEL_RWX 937 def_bool n 938 939config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 940 def_bool n 941 942config ARCH_HAS_STRICT_KERNEL_RWX 943 def_bool n 944 945config STRICT_KERNEL_RWX 946 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 947 depends on ARCH_HAS_STRICT_KERNEL_RWX 948 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 949 help 950 If this is set, kernel text and rodata memory will be made read-only, 951 and non-text memory will be made non-executable. This provides 952 protection against certain security exploits (e.g. executing the heap 953 or modifying text) 954 955 These features are considered standard security practice these days. 956 You should say Y here in almost all cases. 957 958config ARCH_HAS_STRICT_MODULE_RWX 959 def_bool n 960 961config STRICT_MODULE_RWX 962 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 963 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 964 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 965 help 966 If this is set, module text and rodata memory will be made read-only, 967 and non-text memory will be made non-executable. This provides 968 protection against certain security exploits (e.g. writing to text) 969 970# select if the architecture provides an asm/dma-direct.h header 971config ARCH_HAS_PHYS_TO_DMA 972 bool 973 974config ARCH_HAS_REFCOUNT 975 bool 976 help 977 An architecture selects this when it has implemented refcount_t 978 using open coded assembly primitives that provide an optimized 979 refcount_t implementation, possibly at the expense of some full 980 refcount state checks of CONFIG_REFCOUNT_FULL=y. 981 982 The refcount overflow check behavior, however, must be retained. 983 Catching overflows is the primary security concern for protecting 984 against bugs in reference counts. 985 986config REFCOUNT_FULL 987 bool "Perform full reference count validation at the expense of speed" 988 help 989 Enabling this switches the refcounting infrastructure from a fast 990 unchecked atomic_t implementation to a fully state checked 991 implementation, which can be (slightly) slower but provides protections 992 against various use-after-free conditions that can be used in 993 security flaw exploits. 994 995source "kernel/gcov/Kconfig" 996