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 HAVE_ARCH_WITHIN_STACK_FRAMES 600 bool 601 help 602 An architecture should select this if it can walk the kernel stack 603 frames to determine if an object is part of either the arguments 604 or local variables (i.e. that it excludes saved return addresses, 605 and similar) by implementing an inline arch_within_stack_frames(), 606 which is used by CONFIG_HARDENED_USERCOPY. 607 608config HAVE_CONTEXT_TRACKING 609 bool 610 help 611 Provide kernel/user boundaries probes necessary for subsystems 612 that need it, such as userspace RCU extended quiescent state. 613 Syscalls need to be wrapped inside user_exit()-user_enter() through 614 the slow path using TIF_NOHZ flag. Exceptions handlers must be 615 wrapped as well. Irqs are already protected inside 616 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 617 irq exit still need to be protected. 618 619config HAVE_VIRT_CPU_ACCOUNTING 620 bool 621 622config ARCH_HAS_SCALED_CPUTIME 623 bool 624 625config HAVE_VIRT_CPU_ACCOUNTING_GEN 626 bool 627 default y if 64BIT 628 help 629 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 630 Before enabling this option, arch code must be audited 631 to ensure there are no races in concurrent read/write of 632 cputime_t. For example, reading/writing 64-bit cputime_t on 633 some 32-bit arches may require multiple accesses, so proper 634 locking is needed to protect against concurrent accesses. 635 636 637config HAVE_IRQ_TIME_ACCOUNTING 638 bool 639 help 640 Archs need to ensure they use a high enough resolution clock to 641 support irq time accounting and then call enable_sched_clock_irqtime(). 642 643config HAVE_ARCH_TRANSPARENT_HUGEPAGE 644 bool 645 646config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 647 bool 648 649config HAVE_ARCH_HUGE_VMAP 650 bool 651 652config HAVE_ARCH_SOFT_DIRTY 653 bool 654 655config HAVE_MOD_ARCH_SPECIFIC 656 bool 657 help 658 The arch uses struct mod_arch_specific to store data. Many arches 659 just need a simple module loader without arch specific data - those 660 should not enable this. 661 662config MODULES_USE_ELF_RELA 663 bool 664 help 665 Modules only use ELF RELA relocations. Modules with ELF REL 666 relocations will give an error. 667 668config MODULES_USE_ELF_REL 669 bool 670 help 671 Modules only use ELF REL relocations. Modules with ELF RELA 672 relocations will give an error. 673 674config HAVE_IRQ_EXIT_ON_IRQ_STACK 675 bool 676 help 677 Architecture doesn't only execute the irq handler on the irq stack 678 but also irq_exit(). This way we can process softirqs on this irq 679 stack instead of switching to a new one when we call __do_softirq() 680 in the end of an hardirq. 681 This spares a stack switch and improves cache usage on softirq 682 processing. 683 684config PGTABLE_LEVELS 685 int 686 default 2 687 688config ARCH_HAS_ELF_RANDOMIZE 689 bool 690 help 691 An architecture supports choosing randomized locations for 692 stack, mmap, brk, and ET_DYN. Defined functions: 693 - arch_mmap_rnd() 694 - arch_randomize_brk() 695 696config HAVE_ARCH_MMAP_RND_BITS 697 bool 698 help 699 An arch should select this symbol if it supports setting a variable 700 number of bits for use in establishing the base address for mmap 701 allocations, has MMU enabled and provides values for both: 702 - ARCH_MMAP_RND_BITS_MIN 703 - ARCH_MMAP_RND_BITS_MAX 704 705config HAVE_EXIT_THREAD 706 bool 707 help 708 An architecture implements exit_thread. 709 710config ARCH_MMAP_RND_BITS_MIN 711 int 712 713config ARCH_MMAP_RND_BITS_MAX 714 int 715 716config ARCH_MMAP_RND_BITS_DEFAULT 717 int 718 719config ARCH_MMAP_RND_BITS 720 int "Number of bits to use for ASLR of mmap base address" if EXPERT 721 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 722 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 723 default ARCH_MMAP_RND_BITS_MIN 724 depends on HAVE_ARCH_MMAP_RND_BITS 725 help 726 This value can be used to select the number of bits to use to 727 determine the random offset to the base address of vma regions 728 resulting from mmap allocations. This value will be bounded 729 by the architecture's minimum and maximum supported values. 730 731 This value can be changed after boot using the 732 /proc/sys/vm/mmap_rnd_bits tunable 733 734config HAVE_ARCH_MMAP_RND_COMPAT_BITS 735 bool 736 help 737 An arch should select this symbol if it supports running applications 738 in compatibility mode, supports setting a variable number of bits for 739 use in establishing the base address for mmap allocations, has MMU 740 enabled and provides values for both: 741 - ARCH_MMAP_RND_COMPAT_BITS_MIN 742 - ARCH_MMAP_RND_COMPAT_BITS_MAX 743 744config ARCH_MMAP_RND_COMPAT_BITS_MIN 745 int 746 747config ARCH_MMAP_RND_COMPAT_BITS_MAX 748 int 749 750config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 751 int 752 753config ARCH_MMAP_RND_COMPAT_BITS 754 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 755 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 756 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 757 default ARCH_MMAP_RND_COMPAT_BITS_MIN 758 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 759 help 760 This value can be used to select the number of bits to use to 761 determine the random offset to the base address of vma regions 762 resulting from mmap allocations for compatible applications This 763 value will be bounded by the architecture's minimum and maximum 764 supported values. 765 766 This value can be changed after boot using the 767 /proc/sys/vm/mmap_rnd_compat_bits tunable 768 769config HAVE_ARCH_COMPAT_MMAP_BASES 770 bool 771 help 772 This allows 64bit applications to invoke 32-bit mmap() syscall 773 and vice-versa 32-bit applications to call 64-bit mmap(). 774 Required for applications doing different bitness syscalls. 775 776config HAVE_COPY_THREAD_TLS 777 bool 778 help 779 Architecture provides copy_thread_tls to accept tls argument via 780 normal C parameter passing, rather than extracting the syscall 781 argument from pt_regs. 782 783config HAVE_STACK_VALIDATION 784 bool 785 help 786 Architecture supports the 'objtool check' host tool command, which 787 performs compile-time stack metadata validation. 788 789config HAVE_RELIABLE_STACKTRACE 790 bool 791 help 792 Architecture has a save_stack_trace_tsk_reliable() function which 793 only returns a stack trace if it can guarantee the trace is reliable. 794 795config HAVE_ARCH_HASH 796 bool 797 default n 798 help 799 If this is set, the architecture provides an <asm/hash.h> 800 file which provides platform-specific implementations of some 801 functions in <linux/hash.h> or fs/namei.c. 802 803config ISA_BUS_API 804 def_bool ISA 805 806# 807# ABI hall of shame 808# 809config CLONE_BACKWARDS 810 bool 811 help 812 Architecture has tls passed as the 4th argument of clone(2), 813 not the 5th one. 814 815config CLONE_BACKWARDS2 816 bool 817 help 818 Architecture has the first two arguments of clone(2) swapped. 819 820config CLONE_BACKWARDS3 821 bool 822 help 823 Architecture has tls passed as the 3rd argument of clone(2), 824 not the 5th one. 825 826config ODD_RT_SIGACTION 827 bool 828 help 829 Architecture has unusual rt_sigaction(2) arguments 830 831config OLD_SIGSUSPEND 832 bool 833 help 834 Architecture has old sigsuspend(2) syscall, of one-argument variety 835 836config OLD_SIGSUSPEND3 837 bool 838 help 839 Even weirder antique ABI - three-argument sigsuspend(2) 840 841config OLD_SIGACTION 842 bool 843 help 844 Architecture has old sigaction(2) syscall. Nope, not the same 845 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 846 but fairly different variant of sigaction(2), thanks to OSF/1 847 compatibility... 848 849config COMPAT_OLD_SIGACTION 850 bool 851 852config ARCH_NO_COHERENT_DMA_MMAP 853 bool 854 855config CPU_NO_EFFICIENT_FFS 856 def_bool n 857 858config HAVE_ARCH_VMAP_STACK 859 def_bool n 860 help 861 An arch should select this symbol if it can support kernel stacks 862 in vmalloc space. This means: 863 864 - vmalloc space must be large enough to hold many kernel stacks. 865 This may rule out many 32-bit architectures. 866 867 - Stacks in vmalloc space need to work reliably. For example, if 868 vmap page tables are created on demand, either this mechanism 869 needs to work while the stack points to a virtual address with 870 unpopulated page tables or arch code (switch_to() and switch_mm(), 871 most likely) needs to ensure that the stack's page table entries 872 are populated before running on a possibly unpopulated stack. 873 874 - If the stack overflows into a guard page, something reasonable 875 should happen. The definition of "reasonable" is flexible, but 876 instantly rebooting without logging anything would be unfriendly. 877 878config VMAP_STACK 879 default y 880 bool "Use a virtually-mapped stack" 881 depends on HAVE_ARCH_VMAP_STACK && !KASAN 882 ---help--- 883 Enable this if you want the use virtually-mapped kernel stacks 884 with guard pages. This causes kernel stack overflows to be 885 caught immediately rather than causing difficult-to-diagnose 886 corruption. 887 888 This is presently incompatible with KASAN because KASAN expects 889 the stack to map directly to the KASAN shadow map using a formula 890 that is incorrect if the stack is in vmalloc space. 891 892config ARCH_OPTIONAL_KERNEL_RWX 893 def_bool n 894 895config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 896 def_bool n 897 898config ARCH_HAS_STRICT_KERNEL_RWX 899 def_bool n 900 901config STRICT_KERNEL_RWX 902 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 903 depends on ARCH_HAS_STRICT_KERNEL_RWX 904 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 905 help 906 If this is set, kernel text and rodata memory will be made read-only, 907 and non-text memory will be made non-executable. This provides 908 protection against certain security exploits (e.g. executing the heap 909 or modifying text) 910 911 These features are considered standard security practice these days. 912 You should say Y here in almost all cases. 913 914config ARCH_HAS_STRICT_MODULE_RWX 915 def_bool n 916 917config STRICT_MODULE_RWX 918 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 919 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 920 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 921 help 922 If this is set, module text and rodata memory will be made read-only, 923 and non-text memory will be made non-executable. This provides 924 protection against certain security exploits (e.g. writing to text) 925 926# select if the architecture provides an asm/dma-direct.h header 927config ARCH_HAS_PHYS_TO_DMA 928 bool 929 930config ARCH_HAS_REFCOUNT 931 bool 932 help 933 An architecture selects this when it has implemented refcount_t 934 using open coded assembly primitives that provide an optimized 935 refcount_t implementation, possibly at the expense of some full 936 refcount state checks of CONFIG_REFCOUNT_FULL=y. 937 938 The refcount overflow check behavior, however, must be retained. 939 Catching overflows is the primary security concern for protecting 940 against bugs in reference counts. 941 942config REFCOUNT_FULL 943 bool "Perform full reference count validation at the expense of speed" 944 help 945 Enabling this switches the refcounting infrastructure from a fast 946 unchecked atomic_t implementation to a fully state checked 947 implementation, which can be (slightly) slower but provides protections 948 against various use-after-free conditions that can be used in 949 security flaw exploits. 950 951source "kernel/gcov/Kconfig" 952