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_NMI 200 bool 201 202# 203# An arch should select this if it provides all these things: 204# 205# task_pt_regs() in asm/processor.h or asm/ptrace.h 206# arch_has_single_step() if there is hardware single-step support 207# arch_has_block_step() if there is hardware block-step support 208# asm/syscall.h supplying asm-generic/syscall.h interface 209# linux/regset.h user_regset interfaces 210# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 211# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 212# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 213# signal delivery calls tracehook_signal_handler() 214# 215config HAVE_ARCH_TRACEHOOK 216 bool 217 218config HAVE_DMA_CONTIGUOUS 219 bool 220 221config GENERIC_SMP_IDLE_THREAD 222 bool 223 224config GENERIC_IDLE_POLL_SETUP 225 bool 226 227config ARCH_HAS_FORTIFY_SOURCE 228 bool 229 help 230 An architecture should select this when it can successfully 231 build and run with CONFIG_FORTIFY_SOURCE. 232 233# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 234config ARCH_HAS_SET_MEMORY 235 bool 236 237# Select if arch init_task must go in the __init_task_data section 238config ARCH_TASK_STRUCT_ON_STACK 239 bool 240 241# Select if arch has its private alloc_task_struct() function 242config ARCH_TASK_STRUCT_ALLOCATOR 243 bool 244 245# Select if arch has its private alloc_thread_stack() function 246config ARCH_THREAD_STACK_ALLOCATOR 247 bool 248 249# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 250config ARCH_WANTS_DYNAMIC_TASK_STRUCT 251 bool 252 253config HAVE_REGS_AND_STACK_ACCESS_API 254 bool 255 help 256 This symbol should be selected by an architecure if it supports 257 the API needed to access registers and stack entries from pt_regs, 258 declared in asm/ptrace.h 259 For example the kprobes-based event tracer needs this API. 260 261config HAVE_CLK 262 bool 263 help 264 The <linux/clk.h> calls support software clock gating and 265 thus are a key power management tool on many systems. 266 267config HAVE_DMA_API_DEBUG 268 bool 269 270config HAVE_HW_BREAKPOINT 271 bool 272 depends on PERF_EVENTS 273 274config HAVE_MIXED_BREAKPOINTS_REGS 275 bool 276 depends on HAVE_HW_BREAKPOINT 277 help 278 Depending on the arch implementation of hardware breakpoints, 279 some of them have separate registers for data and instruction 280 breakpoints addresses, others have mixed registers to store 281 them but define the access type in a control register. 282 Select this option if your arch implements breakpoints under the 283 latter fashion. 284 285config HAVE_USER_RETURN_NOTIFIER 286 bool 287 288config HAVE_PERF_EVENTS_NMI 289 bool 290 help 291 System hardware can generate an NMI using the perf event 292 subsystem. Also has support for calculating CPU cycle events 293 to determine how many clock cycles in a given period. 294 295config HAVE_HARDLOCKUP_DETECTOR_PERF 296 bool 297 depends on HAVE_PERF_EVENTS_NMI 298 help 299 The arch chooses to use the generic perf-NMI-based hardlockup 300 detector. Must define HAVE_PERF_EVENTS_NMI. 301 302config HAVE_NMI_WATCHDOG 303 depends on HAVE_NMI 304 bool 305 help 306 The arch provides a low level NMI watchdog. It provides 307 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 308 309config HAVE_HARDLOCKUP_DETECTOR_ARCH 310 bool 311 select HAVE_NMI_WATCHDOG 312 help 313 The arch chooses to provide its own hardlockup detector, which is 314 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 315 interfaces and parameters provided by hardlockup detector subsystem. 316 317config HAVE_PERF_REGS 318 bool 319 help 320 Support selective register dumps for perf events. This includes 321 bit-mapping of each registers and a unique architecture id. 322 323config HAVE_PERF_USER_STACK_DUMP 324 bool 325 help 326 Support user stack dumps for perf event samples. This needs 327 access to the user stack pointer which is not unified across 328 architectures. 329 330config HAVE_ARCH_JUMP_LABEL 331 bool 332 333config HAVE_RCU_TABLE_FREE 334 bool 335 336config ARCH_HAVE_NMI_SAFE_CMPXCHG 337 bool 338 339config HAVE_ALIGNED_STRUCT_PAGE 340 bool 341 help 342 This makes sure that struct pages are double word aligned and that 343 e.g. the SLUB allocator can perform double word atomic operations 344 on a struct page for better performance. However selecting this 345 might increase the size of a struct page by a word. 346 347config HAVE_CMPXCHG_LOCAL 348 bool 349 350config HAVE_CMPXCHG_DOUBLE 351 bool 352 353config ARCH_WEAK_RELEASE_ACQUIRE 354 bool 355 356config ARCH_WANT_IPC_PARSE_VERSION 357 bool 358 359config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 360 bool 361 362config ARCH_WANT_OLD_COMPAT_IPC 363 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 364 bool 365 366config HAVE_ARCH_SECCOMP_FILTER 367 bool 368 help 369 An arch should select this symbol if it provides all of these things: 370 - syscall_get_arch() 371 - syscall_get_arguments() 372 - syscall_rollback() 373 - syscall_set_return_value() 374 - SIGSYS siginfo_t support 375 - secure_computing is called from a ptrace_event()-safe context 376 - secure_computing return value is checked and a return value of -1 377 results in the system call being skipped immediately. 378 - seccomp syscall wired up 379 380config SECCOMP_FILTER 381 def_bool y 382 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 383 help 384 Enable tasks to build secure computing environments defined 385 in terms of Berkeley Packet Filter programs which implement 386 task-defined system call filtering polices. 387 388 See Documentation/prctl/seccomp_filter.txt for details. 389 390config HAVE_GCC_PLUGINS 391 bool 392 help 393 An arch should select this symbol if it supports building with 394 GCC plugins. 395 396menuconfig GCC_PLUGINS 397 bool "GCC plugins" 398 depends on HAVE_GCC_PLUGINS 399 depends on !COMPILE_TEST 400 help 401 GCC plugins are loadable modules that provide extra features to the 402 compiler. They are useful for runtime instrumentation and static analysis. 403 404 See Documentation/gcc-plugins.txt for details. 405 406config GCC_PLUGIN_CYC_COMPLEXITY 407 bool "Compute the cyclomatic complexity of a function" if EXPERT 408 depends on GCC_PLUGINS 409 depends on !COMPILE_TEST 410 help 411 The complexity M of a function's control flow graph is defined as: 412 M = E - N + 2P 413 where 414 415 E = the number of edges 416 N = the number of nodes 417 P = the number of connected components (exit nodes). 418 419 Enabling this plugin reports the complexity to stderr during the 420 build. It mainly serves as a simple example of how to create a 421 gcc plugin for the kernel. 422 423config GCC_PLUGIN_SANCOV 424 bool 425 depends on GCC_PLUGINS 426 help 427 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 428 basic blocks. It supports all gcc versions with plugin support (from 429 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 430 by Dmitry Vyukov <dvyukov@google.com>. 431 432config GCC_PLUGIN_LATENT_ENTROPY 433 bool "Generate some entropy during boot and runtime" 434 depends on GCC_PLUGINS 435 help 436 By saying Y here the kernel will instrument some kernel code to 437 extract some entropy from both original and artificially created 438 program state. This will help especially embedded systems where 439 there is little 'natural' source of entropy normally. The cost 440 is some slowdown of the boot process (about 0.5%) and fork and 441 irq processing. 442 443 Note that entropy extracted this way is not cryptographically 444 secure! 445 446 This plugin was ported from grsecurity/PaX. More information at: 447 * https://grsecurity.net/ 448 * https://pax.grsecurity.net/ 449 450config GCC_PLUGIN_STRUCTLEAK 451 bool "Force initialization of variables containing userspace addresses" 452 depends on GCC_PLUGINS 453 help 454 This plugin zero-initializes any structures containing a 455 __user attribute. This can prevent some classes of information 456 exposures. 457 458 This plugin was ported from grsecurity/PaX. More information at: 459 * https://grsecurity.net/ 460 * https://pax.grsecurity.net/ 461 462config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 463 bool "Force initialize all struct type variables passed by reference" 464 depends on GCC_PLUGIN_STRUCTLEAK 465 help 466 Zero initialize any struct type local variable that may be passed by 467 reference without having been initialized. 468 469config GCC_PLUGIN_STRUCTLEAK_VERBOSE 470 bool "Report forcefully initialized variables" 471 depends on GCC_PLUGIN_STRUCTLEAK 472 depends on !COMPILE_TEST 473 help 474 This option will cause a warning to be printed each time the 475 structleak plugin finds a variable it thinks needs to be 476 initialized. Since not all existing initializers are detected 477 by the plugin, this can produce false positive warnings. 478 479config GCC_PLUGIN_RANDSTRUCT 480 bool "Randomize layout of sensitive kernel structures" 481 depends on GCC_PLUGINS 482 select MODVERSIONS if MODULES 483 help 484 If you say Y here, the layouts of structures that are entirely 485 function pointers (and have not been manually annotated with 486 __no_randomize_layout), or structures that have been explicitly 487 marked with __randomize_layout, will be randomized at compile-time. 488 This can introduce the requirement of an additional information 489 exposure vulnerability for exploits targeting these structure 490 types. 491 492 Enabling this feature will introduce some performance impact, 493 slightly increase memory usage, and prevent the use of forensic 494 tools like Volatility against the system (unless the kernel 495 source tree isn't cleaned after kernel installation). 496 497 The seed used for compilation is located at 498 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 499 a make clean to allow for external modules to be compiled with 500 the existing seed and will be removed by a make mrproper or 501 make distclean. 502 503 Note that the implementation requires gcc 4.7 or newer. 504 505 This plugin was ported from grsecurity/PaX. More information at: 506 * https://grsecurity.net/ 507 * https://pax.grsecurity.net/ 508 509config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 510 bool "Use cacheline-aware structure randomization" 511 depends on GCC_PLUGIN_RANDSTRUCT 512 depends on !COMPILE_TEST 513 help 514 If you say Y here, the RANDSTRUCT randomization will make a 515 best effort at restricting randomization to cacheline-sized 516 groups of elements. It will further not randomize bitfields 517 in structures. This reduces the performance hit of RANDSTRUCT 518 at the cost of weakened randomization. 519 520config HAVE_CC_STACKPROTECTOR 521 bool 522 help 523 An arch should select this symbol if: 524 - its compiler supports the -fstack-protector option 525 - it has implemented a stack canary (e.g. __stack_chk_guard) 526 527config CC_STACKPROTECTOR 528 def_bool n 529 help 530 Set when a stack-protector mode is enabled, so that the build 531 can enable kernel-side support for the GCC feature. 532 533choice 534 prompt "Stack Protector buffer overflow detection" 535 depends on HAVE_CC_STACKPROTECTOR 536 default CC_STACKPROTECTOR_NONE 537 help 538 This option turns on the "stack-protector" GCC feature. This 539 feature puts, at the beginning of functions, a canary value on 540 the stack just before the return address, and validates 541 the value just before actually returning. Stack based buffer 542 overflows (that need to overwrite this return address) now also 543 overwrite the canary, which gets detected and the attack is then 544 neutralized via a kernel panic. 545 546config CC_STACKPROTECTOR_NONE 547 bool "None" 548 help 549 Disable "stack-protector" GCC feature. 550 551config CC_STACKPROTECTOR_REGULAR 552 bool "Regular" 553 select CC_STACKPROTECTOR 554 help 555 Functions will have the stack-protector canary logic added if they 556 have an 8-byte or larger character array on the stack. 557 558 This feature requires gcc version 4.2 or above, or a distribution 559 gcc with the feature backported ("-fstack-protector"). 560 561 On an x86 "defconfig" build, this feature adds canary checks to 562 about 3% of all kernel functions, which increases kernel code size 563 by about 0.3%. 564 565config CC_STACKPROTECTOR_STRONG 566 bool "Strong" 567 select CC_STACKPROTECTOR 568 help 569 Functions will have the stack-protector canary logic added in any 570 of the following conditions: 571 572 - local variable's address used as part of the right hand side of an 573 assignment or function argument 574 - local variable is an array (or union containing an array), 575 regardless of array type or length 576 - uses register local variables 577 578 This feature requires gcc version 4.9 or above, or a distribution 579 gcc with the feature backported ("-fstack-protector-strong"). 580 581 On an x86 "defconfig" build, this feature adds canary checks to 582 about 20% of all kernel functions, which increases the kernel code 583 size by about 2%. 584 585endchoice 586 587config THIN_ARCHIVES 588 def_bool y 589 help 590 Select this if the architecture wants to use thin archives 591 instead of ld -r to create the built-in.o files. 592 593config LD_DEAD_CODE_DATA_ELIMINATION 594 bool 595 help 596 Select this if the architecture wants to do dead code and 597 data elimination with the linker by compiling with 598 -ffunction-sections -fdata-sections and linking with 599 --gc-sections. 600 601 This requires that the arch annotates or otherwise protects 602 its external entry points from being discarded. Linker scripts 603 must also merge .text.*, .data.*, and .bss.* correctly into 604 output sections. Care must be taken not to pull in unrelated 605 sections (e.g., '.text.init'). Typically '.' in section names 606 is used to distinguish them from label names / C identifiers. 607 608config HAVE_ARCH_WITHIN_STACK_FRAMES 609 bool 610 help 611 An architecture should select this if it can walk the kernel stack 612 frames to determine if an object is part of either the arguments 613 or local variables (i.e. that it excludes saved return addresses, 614 and similar) by implementing an inline arch_within_stack_frames(), 615 which is used by CONFIG_HARDENED_USERCOPY. 616 617config HAVE_CONTEXT_TRACKING 618 bool 619 help 620 Provide kernel/user boundaries probes necessary for subsystems 621 that need it, such as userspace RCU extended quiescent state. 622 Syscalls need to be wrapped inside user_exit()-user_enter() through 623 the slow path using TIF_NOHZ flag. Exceptions handlers must be 624 wrapped as well. Irqs are already protected inside 625 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 626 irq exit still need to be protected. 627 628config HAVE_VIRT_CPU_ACCOUNTING 629 bool 630 631config ARCH_HAS_SCALED_CPUTIME 632 bool 633 634config HAVE_VIRT_CPU_ACCOUNTING_GEN 635 bool 636 default y if 64BIT 637 help 638 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 639 Before enabling this option, arch code must be audited 640 to ensure there are no races in concurrent read/write of 641 cputime_t. For example, reading/writing 64-bit cputime_t on 642 some 32-bit arches may require multiple accesses, so proper 643 locking is needed to protect against concurrent accesses. 644 645 646config HAVE_IRQ_TIME_ACCOUNTING 647 bool 648 help 649 Archs need to ensure they use a high enough resolution clock to 650 support irq time accounting and then call enable_sched_clock_irqtime(). 651 652config HAVE_ARCH_TRANSPARENT_HUGEPAGE 653 bool 654 655config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 656 bool 657 658config HAVE_ARCH_HUGE_VMAP 659 bool 660 661config HAVE_ARCH_SOFT_DIRTY 662 bool 663 664config HAVE_MOD_ARCH_SPECIFIC 665 bool 666 help 667 The arch uses struct mod_arch_specific to store data. Many arches 668 just need a simple module loader without arch specific data - those 669 should not enable this. 670 671config MODULES_USE_ELF_RELA 672 bool 673 help 674 Modules only use ELF RELA relocations. Modules with ELF REL 675 relocations will give an error. 676 677config MODULES_USE_ELF_REL 678 bool 679 help 680 Modules only use ELF REL relocations. Modules with ELF RELA 681 relocations will give an error. 682 683config HAVE_UNDERSCORE_SYMBOL_PREFIX 684 bool 685 help 686 Some architectures generate an _ in front of C symbols; things like 687 module loading and assembly files need to know about this. 688 689config HAVE_IRQ_EXIT_ON_IRQ_STACK 690 bool 691 help 692 Architecture doesn't only execute the irq handler on the irq stack 693 but also irq_exit(). This way we can process softirqs on this irq 694 stack instead of switching to a new one when we call __do_softirq() 695 in the end of an hardirq. 696 This spares a stack switch and improves cache usage on softirq 697 processing. 698 699config PGTABLE_LEVELS 700 int 701 default 2 702 703config ARCH_HAS_ELF_RANDOMIZE 704 bool 705 help 706 An architecture supports choosing randomized locations for 707 stack, mmap, brk, and ET_DYN. Defined functions: 708 - arch_mmap_rnd() 709 - arch_randomize_brk() 710 711config HAVE_ARCH_MMAP_RND_BITS 712 bool 713 help 714 An arch should select this symbol if it supports setting a variable 715 number of bits for use in establishing the base address for mmap 716 allocations, has MMU enabled and provides values for both: 717 - ARCH_MMAP_RND_BITS_MIN 718 - ARCH_MMAP_RND_BITS_MAX 719 720config HAVE_EXIT_THREAD 721 bool 722 help 723 An architecture implements exit_thread. 724 725config ARCH_MMAP_RND_BITS_MIN 726 int 727 728config ARCH_MMAP_RND_BITS_MAX 729 int 730 731config ARCH_MMAP_RND_BITS_DEFAULT 732 int 733 734config ARCH_MMAP_RND_BITS 735 int "Number of bits to use for ASLR of mmap base address" if EXPERT 736 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 737 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 738 default ARCH_MMAP_RND_BITS_MIN 739 depends on HAVE_ARCH_MMAP_RND_BITS 740 help 741 This value can be used to select the number of bits to use to 742 determine the random offset to the base address of vma regions 743 resulting from mmap allocations. This value will be bounded 744 by the architecture's minimum and maximum supported values. 745 746 This value can be changed after boot using the 747 /proc/sys/vm/mmap_rnd_bits tunable 748 749config HAVE_ARCH_MMAP_RND_COMPAT_BITS 750 bool 751 help 752 An arch should select this symbol if it supports running applications 753 in compatibility mode, supports setting a variable number of bits for 754 use in establishing the base address for mmap allocations, has MMU 755 enabled and provides values for both: 756 - ARCH_MMAP_RND_COMPAT_BITS_MIN 757 - ARCH_MMAP_RND_COMPAT_BITS_MAX 758 759config ARCH_MMAP_RND_COMPAT_BITS_MIN 760 int 761 762config ARCH_MMAP_RND_COMPAT_BITS_MAX 763 int 764 765config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 766 int 767 768config ARCH_MMAP_RND_COMPAT_BITS 769 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 770 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 771 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 772 default ARCH_MMAP_RND_COMPAT_BITS_MIN 773 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 774 help 775 This value can be used to select the number of bits to use to 776 determine the random offset to the base address of vma regions 777 resulting from mmap allocations for compatible applications This 778 value will be bounded by the architecture's minimum and maximum 779 supported values. 780 781 This value can be changed after boot using the 782 /proc/sys/vm/mmap_rnd_compat_bits tunable 783 784config HAVE_ARCH_COMPAT_MMAP_BASES 785 bool 786 help 787 This allows 64bit applications to invoke 32-bit mmap() syscall 788 and vice-versa 32-bit applications to call 64-bit mmap(). 789 Required for applications doing different bitness syscalls. 790 791config HAVE_COPY_THREAD_TLS 792 bool 793 help 794 Architecture provides copy_thread_tls to accept tls argument via 795 normal C parameter passing, rather than extracting the syscall 796 argument from pt_regs. 797 798config HAVE_STACK_VALIDATION 799 bool 800 help 801 Architecture supports the 'objtool check' host tool command, which 802 performs compile-time stack metadata validation. 803 804config HAVE_RELIABLE_STACKTRACE 805 bool 806 help 807 Architecture has a save_stack_trace_tsk_reliable() function which 808 only returns a stack trace if it can guarantee the trace is reliable. 809 810config HAVE_ARCH_HASH 811 bool 812 default n 813 help 814 If this is set, the architecture provides an <asm/hash.h> 815 file which provides platform-specific implementations of some 816 functions in <linux/hash.h> or fs/namei.c. 817 818config ISA_BUS_API 819 def_bool ISA 820 821# 822# ABI hall of shame 823# 824config CLONE_BACKWARDS 825 bool 826 help 827 Architecture has tls passed as the 4th argument of clone(2), 828 not the 5th one. 829 830config CLONE_BACKWARDS2 831 bool 832 help 833 Architecture has the first two arguments of clone(2) swapped. 834 835config CLONE_BACKWARDS3 836 bool 837 help 838 Architecture has tls passed as the 3rd argument of clone(2), 839 not the 5th one. 840 841config ODD_RT_SIGACTION 842 bool 843 help 844 Architecture has unusual rt_sigaction(2) arguments 845 846config OLD_SIGSUSPEND 847 bool 848 help 849 Architecture has old sigsuspend(2) syscall, of one-argument variety 850 851config OLD_SIGSUSPEND3 852 bool 853 help 854 Even weirder antique ABI - three-argument sigsuspend(2) 855 856config OLD_SIGACTION 857 bool 858 help 859 Architecture has old sigaction(2) syscall. Nope, not the same 860 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 861 but fairly different variant of sigaction(2), thanks to OSF/1 862 compatibility... 863 864config COMPAT_OLD_SIGACTION 865 bool 866 867config ARCH_NO_COHERENT_DMA_MMAP 868 bool 869 870config CPU_NO_EFFICIENT_FFS 871 def_bool n 872 873config HAVE_ARCH_VMAP_STACK 874 def_bool n 875 help 876 An arch should select this symbol if it can support kernel stacks 877 in vmalloc space. This means: 878 879 - vmalloc space must be large enough to hold many kernel stacks. 880 This may rule out many 32-bit architectures. 881 882 - Stacks in vmalloc space need to work reliably. For example, if 883 vmap page tables are created on demand, either this mechanism 884 needs to work while the stack points to a virtual address with 885 unpopulated page tables or arch code (switch_to() and switch_mm(), 886 most likely) needs to ensure that the stack's page table entries 887 are populated before running on a possibly unpopulated stack. 888 889 - If the stack overflows into a guard page, something reasonable 890 should happen. The definition of "reasonable" is flexible, but 891 instantly rebooting without logging anything would be unfriendly. 892 893config VMAP_STACK 894 default y 895 bool "Use a virtually-mapped stack" 896 depends on HAVE_ARCH_VMAP_STACK && !KASAN 897 ---help--- 898 Enable this if you want the use virtually-mapped kernel stacks 899 with guard pages. This causes kernel stack overflows to be 900 caught immediately rather than causing difficult-to-diagnose 901 corruption. 902 903 This is presently incompatible with KASAN because KASAN expects 904 the stack to map directly to the KASAN shadow map using a formula 905 that is incorrect if the stack is in vmalloc space. 906 907config ARCH_OPTIONAL_KERNEL_RWX 908 def_bool n 909 910config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 911 def_bool n 912 913config ARCH_HAS_STRICT_KERNEL_RWX 914 def_bool n 915 916config STRICT_KERNEL_RWX 917 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 918 depends on ARCH_HAS_STRICT_KERNEL_RWX 919 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 920 help 921 If this is set, kernel text and rodata memory will be made read-only, 922 and non-text memory will be made non-executable. This provides 923 protection against certain security exploits (e.g. executing the heap 924 or modifying text) 925 926 These features are considered standard security practice these days. 927 You should say Y here in almost all cases. 928 929config ARCH_HAS_STRICT_MODULE_RWX 930 def_bool n 931 932config STRICT_MODULE_RWX 933 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 934 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 935 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 936 help 937 If this is set, module text and rodata memory will be made read-only, 938 and non-text memory will be made non-executable. This provides 939 protection against certain security exploits (e.g. writing to text) 940 941# select if the architecture provides an asm/dma-direct.h header 942config ARCH_HAS_PHYS_TO_DMA 943 bool 944 945config ARCH_HAS_REFCOUNT 946 bool 947 help 948 An architecture selects this when it has implemented refcount_t 949 using open coded assembly primitives that provide an optimized 950 refcount_t implementation, possibly at the expense of some full 951 refcount state checks of CONFIG_REFCOUNT_FULL=y. 952 953 The refcount overflow check behavior, however, must be retained. 954 Catching overflows is the primary security concern for protecting 955 against bugs in reference counts. 956 957config REFCOUNT_FULL 958 bool "Perform full reference count validation at the expense of speed" 959 help 960 Enabling this switches the refcounting infrastructure from a fast 961 unchecked atomic_t implementation to a fully state checked 962 implementation, which can be (slightly) slower but provides protections 963 against various use-after-free conditions that can be used in 964 security flaw exploits. 965 966source "kernel/gcov/Kconfig" 967