1# 2# General architecture dependent options 3# 4 5config CRASH_CORE 6 bool 7 8config KEXEC_CORE 9 select CRASH_CORE 10 bool 11 12config HAVE_IMA_KEXEC 13 bool 14 15config OPROFILE 16 tristate "OProfile system profiling" 17 depends on PROFILING 18 depends on HAVE_OPROFILE 19 select RING_BUFFER 20 select RING_BUFFER_ALLOW_SWAP 21 help 22 OProfile is a profiling system capable of profiling the 23 whole system, include the kernel, kernel modules, libraries, 24 and applications. 25 26 If unsure, say N. 27 28config OPROFILE_EVENT_MULTIPLEX 29 bool "OProfile multiplexing support (EXPERIMENTAL)" 30 default n 31 depends on OPROFILE && X86 32 help 33 The number of hardware counters is limited. The multiplexing 34 feature enables OProfile to gather more events than counters 35 are provided by the hardware. This is realized by switching 36 between events at a user specified time interval. 37 38 If unsure, say N. 39 40config HAVE_OPROFILE 41 bool 42 43config OPROFILE_NMI_TIMER 44 def_bool y 45 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 46 47config KPROBES 48 bool "Kprobes" 49 depends on MODULES 50 depends on HAVE_KPROBES 51 select KALLSYMS 52 help 53 Kprobes allows you to trap at almost any kernel address and 54 execute a callback function. register_kprobe() establishes 55 a probepoint and specifies the callback. Kprobes is useful 56 for kernel debugging, non-intrusive instrumentation and testing. 57 If in doubt, say "N". 58 59config JUMP_LABEL 60 bool "Optimize very unlikely/likely branches" 61 depends on HAVE_ARCH_JUMP_LABEL 62 help 63 This option enables a transparent branch optimization that 64 makes certain almost-always-true or almost-always-false branch 65 conditions even cheaper to execute within the kernel. 66 67 Certain performance-sensitive kernel code, such as trace points, 68 scheduler functionality, networking code and KVM have such 69 branches and include support for this optimization technique. 70 71 If it is detected that the compiler has support for "asm goto", 72 the kernel will compile such branches with just a nop 73 instruction. When the condition flag is toggled to true, the 74 nop will be converted to a jump instruction to execute the 75 conditional block of instructions. 76 77 This technique lowers overhead and stress on the branch prediction 78 of the processor and generally makes the kernel faster. The update 79 of the condition is slower, but those are always very rare. 80 81 ( On 32-bit x86, the necessary options added to the compiler 82 flags may increase the size of the kernel slightly. ) 83 84config STATIC_KEYS_SELFTEST 85 bool "Static key selftest" 86 depends on JUMP_LABEL 87 help 88 Boot time self-test of the branch patching code. 89 90config OPTPROBES 91 def_bool y 92 depends on KPROBES && HAVE_OPTPROBES 93 depends on !PREEMPT 94 95config KPROBES_ON_FTRACE 96 def_bool y 97 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 98 depends on DYNAMIC_FTRACE_WITH_REGS 99 help 100 If function tracer is enabled and the arch supports full 101 passing of pt_regs to function tracing, then kprobes can 102 optimize on top of function tracing. 103 104config UPROBES 105 def_bool n 106 depends on ARCH_SUPPORTS_UPROBES 107 help 108 Uprobes is the user-space counterpart to kprobes: they 109 enable instrumentation applications (such as 'perf probe') 110 to establish unintrusive probes in user-space binaries and 111 libraries, by executing handler functions when the probes 112 are hit by user-space applications. 113 114 ( These probes come in the form of single-byte breakpoints, 115 managed by the kernel and kept transparent to the probed 116 application. ) 117 118config HAVE_64BIT_ALIGNED_ACCESS 119 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 120 help 121 Some architectures require 64 bit accesses to be 64 bit 122 aligned, which also requires structs containing 64 bit values 123 to be 64 bit aligned too. This includes some 32 bit 124 architectures which can do 64 bit accesses, as well as 64 bit 125 architectures without unaligned access. 126 127 This symbol should be selected by an architecture if 64 bit 128 accesses are required to be 64 bit aligned in this way even 129 though it is not a 64 bit architecture. 130 131 See Documentation/unaligned-memory-access.txt for more 132 information on the topic of unaligned memory accesses. 133 134config HAVE_EFFICIENT_UNALIGNED_ACCESS 135 bool 136 help 137 Some architectures are unable to perform unaligned accesses 138 without the use of get_unaligned/put_unaligned. Others are 139 unable to perform such accesses efficiently (e.g. trap on 140 unaligned access and require fixing it up in the exception 141 handler.) 142 143 This symbol should be selected by an architecture if it can 144 perform unaligned accesses efficiently to allow different 145 code paths to be selected for these cases. Some network 146 drivers, for example, could opt to not fix up alignment 147 problems with received packets if doing so would not help 148 much. 149 150 See Documentation/unaligned-memory-access.txt for more 151 information on the topic of unaligned memory accesses. 152 153config ARCH_USE_BUILTIN_BSWAP 154 bool 155 help 156 Modern versions of GCC (since 4.4) have builtin functions 157 for handling byte-swapping. Using these, instead of the old 158 inline assembler that the architecture code provides in the 159 __arch_bswapXX() macros, allows the compiler to see what's 160 happening and offers more opportunity for optimisation. In 161 particular, the compiler will be able to combine the byteswap 162 with a nearby load or store and use load-and-swap or 163 store-and-swap instructions if the architecture has them. It 164 should almost *never* result in code which is worse than the 165 hand-coded assembler in <asm/swab.h>. But just in case it 166 does, the use of the builtins is optional. 167 168 Any architecture with load-and-swap or store-and-swap 169 instructions should set this. And it shouldn't hurt to set it 170 on architectures that don't have such instructions. 171 172config KRETPROBES 173 def_bool y 174 depends on KPROBES && HAVE_KRETPROBES 175 176config USER_RETURN_NOTIFIER 177 bool 178 depends on HAVE_USER_RETURN_NOTIFIER 179 help 180 Provide a kernel-internal notification when a cpu is about to 181 switch to user mode. 182 183config HAVE_IOREMAP_PROT 184 bool 185 186config HAVE_KPROBES 187 bool 188 189config HAVE_KRETPROBES 190 bool 191 192config HAVE_OPTPROBES 193 bool 194 195config HAVE_KPROBES_ON_FTRACE 196 bool 197 198config HAVE_NMI 199 bool 200 201# 202# An arch should select this if it provides all these things: 203# 204# task_pt_regs() in asm/processor.h or asm/ptrace.h 205# arch_has_single_step() if there is hardware single-step support 206# arch_has_block_step() if there is hardware block-step support 207# asm/syscall.h supplying asm-generic/syscall.h interface 208# linux/regset.h user_regset interfaces 209# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 210# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 211# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 212# signal delivery calls tracehook_signal_handler() 213# 214config HAVE_ARCH_TRACEHOOK 215 bool 216 217config HAVE_DMA_CONTIGUOUS 218 bool 219 220config GENERIC_SMP_IDLE_THREAD 221 bool 222 223config GENERIC_IDLE_POLL_SETUP 224 bool 225 226config ARCH_HAS_FORTIFY_SOURCE 227 bool 228 help 229 An architecture should select this when it can successfully 230 build and run with CONFIG_FORTIFY_SOURCE. 231 232# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 233config ARCH_HAS_SET_MEMORY 234 bool 235 236# Select if arch init_task initializer is different to init/init_task.c 237config ARCH_INIT_TASK 238 bool 239 240# Select if arch has its private alloc_task_struct() function 241config ARCH_TASK_STRUCT_ALLOCATOR 242 bool 243 244# Select if arch has its private alloc_thread_stack() function 245config ARCH_THREAD_STACK_ALLOCATOR 246 bool 247 248# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 249config ARCH_WANTS_DYNAMIC_TASK_STRUCT 250 bool 251 252config HAVE_REGS_AND_STACK_ACCESS_API 253 bool 254 help 255 This symbol should be selected by an architecure if it supports 256 the API needed to access registers and stack entries from pt_regs, 257 declared in asm/ptrace.h 258 For example the kprobes-based event tracer needs this API. 259 260config HAVE_CLK 261 bool 262 help 263 The <linux/clk.h> calls support software clock gating and 264 thus are a key power management tool on many systems. 265 266config HAVE_DMA_API_DEBUG 267 bool 268 269config HAVE_HW_BREAKPOINT 270 bool 271 depends on PERF_EVENTS 272 273config HAVE_MIXED_BREAKPOINTS_REGS 274 bool 275 depends on HAVE_HW_BREAKPOINT 276 help 277 Depending on the arch implementation of hardware breakpoints, 278 some of them have separate registers for data and instruction 279 breakpoints addresses, others have mixed registers to store 280 them but define the access type in a control register. 281 Select this option if your arch implements breakpoints under the 282 latter fashion. 283 284config HAVE_USER_RETURN_NOTIFIER 285 bool 286 287config HAVE_PERF_EVENTS_NMI 288 bool 289 help 290 System hardware can generate an NMI using the perf event 291 subsystem. Also has support for calculating CPU cycle events 292 to determine how many clock cycles in a given period. 293 294config HAVE_HARDLOCKUP_DETECTOR_PERF 295 bool 296 depends on HAVE_PERF_EVENTS_NMI 297 help 298 The arch chooses to use the generic perf-NMI-based hardlockup 299 detector. Must define HAVE_PERF_EVENTS_NMI. 300 301config HAVE_NMI_WATCHDOG 302 depends on HAVE_NMI 303 bool 304 help 305 The arch provides a low level NMI watchdog. It provides 306 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 307 308config HAVE_HARDLOCKUP_DETECTOR_ARCH 309 bool 310 select HAVE_NMI_WATCHDOG 311 help 312 The arch chooses to provide its own hardlockup detector, which is 313 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 314 interfaces and parameters provided by hardlockup detector subsystem. 315 316config HAVE_PERF_REGS 317 bool 318 help 319 Support selective register dumps for perf events. This includes 320 bit-mapping of each registers and a unique architecture id. 321 322config HAVE_PERF_USER_STACK_DUMP 323 bool 324 help 325 Support user stack dumps for perf event samples. This needs 326 access to the user stack pointer which is not unified across 327 architectures. 328 329config HAVE_ARCH_JUMP_LABEL 330 bool 331 332config HAVE_RCU_TABLE_FREE 333 bool 334 335config ARCH_HAVE_NMI_SAFE_CMPXCHG 336 bool 337 338config HAVE_ALIGNED_STRUCT_PAGE 339 bool 340 help 341 This makes sure that struct pages are double word aligned and that 342 e.g. the SLUB allocator can perform double word atomic operations 343 on a struct page for better performance. However selecting this 344 might increase the size of a struct page by a word. 345 346config HAVE_CMPXCHG_LOCAL 347 bool 348 349config HAVE_CMPXCHG_DOUBLE 350 bool 351 352config ARCH_WEAK_RELEASE_ACQUIRE 353 bool 354 355config ARCH_WANT_IPC_PARSE_VERSION 356 bool 357 358config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 359 bool 360 361config ARCH_WANT_OLD_COMPAT_IPC 362 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 363 bool 364 365config HAVE_ARCH_SECCOMP_FILTER 366 bool 367 help 368 An arch should select this symbol if it provides all of these things: 369 - syscall_get_arch() 370 - syscall_get_arguments() 371 - syscall_rollback() 372 - syscall_set_return_value() 373 - SIGSYS siginfo_t support 374 - secure_computing is called from a ptrace_event()-safe context 375 - secure_computing return value is checked and a return value of -1 376 results in the system call being skipped immediately. 377 - seccomp syscall wired up 378 379config SECCOMP_FILTER 380 def_bool y 381 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 382 help 383 Enable tasks to build secure computing environments defined 384 in terms of Berkeley Packet Filter programs which implement 385 task-defined system call filtering polices. 386 387 See Documentation/prctl/seccomp_filter.txt for details. 388 389config HAVE_GCC_PLUGINS 390 bool 391 help 392 An arch should select this symbol if it supports building with 393 GCC plugins. 394 395menuconfig GCC_PLUGINS 396 bool "GCC plugins" 397 depends on HAVE_GCC_PLUGINS 398 depends on !COMPILE_TEST 399 help 400 GCC plugins are loadable modules that provide extra features to the 401 compiler. They are useful for runtime instrumentation and static analysis. 402 403 See Documentation/gcc-plugins.txt for details. 404 405config GCC_PLUGIN_CYC_COMPLEXITY 406 bool "Compute the cyclomatic complexity of a function" if EXPERT 407 depends on GCC_PLUGINS 408 depends on !COMPILE_TEST 409 help 410 The complexity M of a function's control flow graph is defined as: 411 M = E - N + 2P 412 where 413 414 E = the number of edges 415 N = the number of nodes 416 P = the number of connected components (exit nodes). 417 418 Enabling this plugin reports the complexity to stderr during the 419 build. It mainly serves as a simple example of how to create a 420 gcc plugin for the kernel. 421 422config GCC_PLUGIN_SANCOV 423 bool 424 depends on GCC_PLUGINS 425 help 426 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 427 basic blocks. It supports all gcc versions with plugin support (from 428 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 429 by Dmitry Vyukov <dvyukov@google.com>. 430 431config GCC_PLUGIN_LATENT_ENTROPY 432 bool "Generate some entropy during boot and runtime" 433 depends on GCC_PLUGINS 434 help 435 By saying Y here the kernel will instrument some kernel code to 436 extract some entropy from both original and artificially created 437 program state. This will help especially embedded systems where 438 there is little 'natural' source of entropy normally. The cost 439 is some slowdown of the boot process (about 0.5%) and fork and 440 irq processing. 441 442 Note that entropy extracted this way is not cryptographically 443 secure! 444 445 This plugin was ported from grsecurity/PaX. More information at: 446 * https://grsecurity.net/ 447 * https://pax.grsecurity.net/ 448 449config GCC_PLUGIN_STRUCTLEAK 450 bool "Force initialization of variables containing userspace addresses" 451 depends on GCC_PLUGINS 452 help 453 This plugin zero-initializes any structures containing a 454 __user attribute. This can prevent some classes of information 455 exposures. 456 457 This plugin was ported from grsecurity/PaX. More information at: 458 * https://grsecurity.net/ 459 * https://pax.grsecurity.net/ 460 461config GCC_PLUGIN_STRUCTLEAK_VERBOSE 462 bool "Report forcefully initialized variables" 463 depends on GCC_PLUGIN_STRUCTLEAK 464 depends on !COMPILE_TEST 465 help 466 This option will cause a warning to be printed each time the 467 structleak plugin finds a variable it thinks needs to be 468 initialized. Since not all existing initializers are detected 469 by the plugin, this can produce false positive warnings. 470 471config GCC_PLUGIN_RANDSTRUCT 472 bool "Randomize layout of sensitive kernel structures" 473 depends on GCC_PLUGINS 474 select MODVERSIONS if MODULES 475 help 476 If you say Y here, the layouts of structures explicitly 477 marked by __randomize_layout will be randomized at 478 compile-time. This can introduce the requirement of an 479 additional information exposure vulnerability for exploits 480 targeting these structure types. 481 482 Enabling this feature will introduce some performance impact, 483 slightly increase memory usage, and prevent the use of forensic 484 tools like Volatility against the system (unless the kernel 485 source tree isn't cleaned after kernel installation). 486 487 The seed used for compilation is located at 488 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 489 a make clean to allow for external modules to be compiled with 490 the existing seed and will be removed by a make mrproper or 491 make distclean. 492 493 Note that the implementation requires gcc 4.7 or newer. 494 495 This plugin was ported from grsecurity/PaX. More information at: 496 * https://grsecurity.net/ 497 * https://pax.grsecurity.net/ 498 499config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 500 bool "Use cacheline-aware structure randomization" 501 depends on GCC_PLUGIN_RANDSTRUCT 502 depends on !COMPILE_TEST 503 help 504 If you say Y here, the RANDSTRUCT randomization will make a 505 best effort at restricting randomization to cacheline-sized 506 groups of elements. It will further not randomize bitfields 507 in structures. This reduces the performance hit of RANDSTRUCT 508 at the cost of weakened randomization. 509 510config HAVE_CC_STACKPROTECTOR 511 bool 512 help 513 An arch should select this symbol if: 514 - its compiler supports the -fstack-protector option 515 - it has implemented a stack canary (e.g. __stack_chk_guard) 516 517config CC_STACKPROTECTOR 518 def_bool n 519 help 520 Set when a stack-protector mode is enabled, so that the build 521 can enable kernel-side support for the GCC feature. 522 523choice 524 prompt "Stack Protector buffer overflow detection" 525 depends on HAVE_CC_STACKPROTECTOR 526 default CC_STACKPROTECTOR_NONE 527 help 528 This option turns on the "stack-protector" GCC feature. This 529 feature puts, at the beginning of functions, a canary value on 530 the stack just before the return address, and validates 531 the value just before actually returning. Stack based buffer 532 overflows (that need to overwrite this return address) now also 533 overwrite the canary, which gets detected and the attack is then 534 neutralized via a kernel panic. 535 536config CC_STACKPROTECTOR_NONE 537 bool "None" 538 help 539 Disable "stack-protector" GCC feature. 540 541config CC_STACKPROTECTOR_REGULAR 542 bool "Regular" 543 select CC_STACKPROTECTOR 544 help 545 Functions will have the stack-protector canary logic added if they 546 have an 8-byte or larger character array on the stack. 547 548 This feature requires gcc version 4.2 or above, or a distribution 549 gcc with the feature backported ("-fstack-protector"). 550 551 On an x86 "defconfig" build, this feature adds canary checks to 552 about 3% of all kernel functions, which increases kernel code size 553 by about 0.3%. 554 555config CC_STACKPROTECTOR_STRONG 556 bool "Strong" 557 select CC_STACKPROTECTOR 558 help 559 Functions will have the stack-protector canary logic added in any 560 of the following conditions: 561 562 - local variable's address used as part of the right hand side of an 563 assignment or function argument 564 - local variable is an array (or union containing an array), 565 regardless of array type or length 566 - uses register local variables 567 568 This feature requires gcc version 4.9 or above, or a distribution 569 gcc with the feature backported ("-fstack-protector-strong"). 570 571 On an x86 "defconfig" build, this feature adds canary checks to 572 about 20% of all kernel functions, which increases the kernel code 573 size by about 2%. 574 575endchoice 576 577config THIN_ARCHIVES 578 def_bool y 579 help 580 Select this if the architecture wants to use thin archives 581 instead of ld -r to create the built-in.o files. 582 583config LD_DEAD_CODE_DATA_ELIMINATION 584 bool 585 help 586 Select this if the architecture wants to do dead code and 587 data elimination with the linker by compiling with 588 -ffunction-sections -fdata-sections and linking with 589 --gc-sections. 590 591 This requires that the arch annotates or otherwise protects 592 its external entry points from being discarded. Linker scripts 593 must also merge .text.*, .data.*, and .bss.* correctly into 594 output sections. Care must be taken not to pull in unrelated 595 sections (e.g., '.text.init'). Typically '.' in section names 596 is used to distinguish them from label names / C identifiers. 597 598config HAVE_ARCH_WITHIN_STACK_FRAMES 599 bool 600 help 601 An architecture should select this if it can walk the kernel stack 602 frames to determine if an object is part of either the arguments 603 or local variables (i.e. that it excludes saved return addresses, 604 and similar) by implementing an inline arch_within_stack_frames(), 605 which is used by CONFIG_HARDENED_USERCOPY. 606 607config HAVE_CONTEXT_TRACKING 608 bool 609 help 610 Provide kernel/user boundaries probes necessary for subsystems 611 that need it, such as userspace RCU extended quiescent state. 612 Syscalls need to be wrapped inside user_exit()-user_enter() through 613 the slow path using TIF_NOHZ flag. Exceptions handlers must be 614 wrapped as well. Irqs are already protected inside 615 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 616 irq exit still need to be protected. 617 618config HAVE_VIRT_CPU_ACCOUNTING 619 bool 620 621config ARCH_HAS_SCALED_CPUTIME 622 bool 623 624config HAVE_VIRT_CPU_ACCOUNTING_GEN 625 bool 626 default y if 64BIT 627 help 628 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 629 Before enabling this option, arch code must be audited 630 to ensure there are no races in concurrent read/write of 631 cputime_t. For example, reading/writing 64-bit cputime_t on 632 some 32-bit arches may require multiple accesses, so proper 633 locking is needed to protect against concurrent accesses. 634 635 636config HAVE_IRQ_TIME_ACCOUNTING 637 bool 638 help 639 Archs need to ensure they use a high enough resolution clock to 640 support irq time accounting and then call enable_sched_clock_irqtime(). 641 642config HAVE_ARCH_TRANSPARENT_HUGEPAGE 643 bool 644 645config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 646 bool 647 648config HAVE_ARCH_HUGE_VMAP 649 bool 650 651config HAVE_ARCH_SOFT_DIRTY 652 bool 653 654config HAVE_MOD_ARCH_SPECIFIC 655 bool 656 help 657 The arch uses struct mod_arch_specific to store data. Many arches 658 just need a simple module loader without arch specific data - those 659 should not enable this. 660 661config MODULES_USE_ELF_RELA 662 bool 663 help 664 Modules only use ELF RELA relocations. Modules with ELF REL 665 relocations will give an error. 666 667config MODULES_USE_ELF_REL 668 bool 669 help 670 Modules only use ELF REL relocations. Modules with ELF RELA 671 relocations will give an error. 672 673config HAVE_UNDERSCORE_SYMBOL_PREFIX 674 bool 675 help 676 Some architectures generate an _ in front of C symbols; things like 677 module loading and assembly files need to know about this. 678 679config HAVE_IRQ_EXIT_ON_IRQ_STACK 680 bool 681 help 682 Architecture doesn't only execute the irq handler on the irq stack 683 but also irq_exit(). This way we can process softirqs on this irq 684 stack instead of switching to a new one when we call __do_softirq() 685 in the end of an hardirq. 686 This spares a stack switch and improves cache usage on softirq 687 processing. 688 689config PGTABLE_LEVELS 690 int 691 default 2 692 693config ARCH_HAS_ELF_RANDOMIZE 694 bool 695 help 696 An architecture supports choosing randomized locations for 697 stack, mmap, brk, and ET_DYN. Defined functions: 698 - arch_mmap_rnd() 699 - arch_randomize_brk() 700 701config HAVE_ARCH_MMAP_RND_BITS 702 bool 703 help 704 An arch should select this symbol if it supports setting a variable 705 number of bits for use in establishing the base address for mmap 706 allocations, has MMU enabled and provides values for both: 707 - ARCH_MMAP_RND_BITS_MIN 708 - ARCH_MMAP_RND_BITS_MAX 709 710config HAVE_EXIT_THREAD 711 bool 712 help 713 An architecture implements exit_thread. 714 715config ARCH_MMAP_RND_BITS_MIN 716 int 717 718config ARCH_MMAP_RND_BITS_MAX 719 int 720 721config ARCH_MMAP_RND_BITS_DEFAULT 722 int 723 724config ARCH_MMAP_RND_BITS 725 int "Number of bits to use for ASLR of mmap base address" if EXPERT 726 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 727 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 728 default ARCH_MMAP_RND_BITS_MIN 729 depends on HAVE_ARCH_MMAP_RND_BITS 730 help 731 This value can be used to select the number of bits to use to 732 determine the random offset to the base address of vma regions 733 resulting from mmap allocations. This value will be bounded 734 by the architecture's minimum and maximum supported values. 735 736 This value can be changed after boot using the 737 /proc/sys/vm/mmap_rnd_bits tunable 738 739config HAVE_ARCH_MMAP_RND_COMPAT_BITS 740 bool 741 help 742 An arch should select this symbol if it supports running applications 743 in compatibility mode, supports setting a variable number of bits for 744 use in establishing the base address for mmap allocations, has MMU 745 enabled and provides values for both: 746 - ARCH_MMAP_RND_COMPAT_BITS_MIN 747 - ARCH_MMAP_RND_COMPAT_BITS_MAX 748 749config ARCH_MMAP_RND_COMPAT_BITS_MIN 750 int 751 752config ARCH_MMAP_RND_COMPAT_BITS_MAX 753 int 754 755config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 756 int 757 758config ARCH_MMAP_RND_COMPAT_BITS 759 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 760 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 761 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 762 default ARCH_MMAP_RND_COMPAT_BITS_MIN 763 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 764 help 765 This value can be used to select the number of bits to use to 766 determine the random offset to the base address of vma regions 767 resulting from mmap allocations for compatible applications This 768 value will be bounded by the architecture's minimum and maximum 769 supported values. 770 771 This value can be changed after boot using the 772 /proc/sys/vm/mmap_rnd_compat_bits tunable 773 774config HAVE_ARCH_COMPAT_MMAP_BASES 775 bool 776 help 777 This allows 64bit applications to invoke 32-bit mmap() syscall 778 and vice-versa 32-bit applications to call 64-bit mmap(). 779 Required for applications doing different bitness syscalls. 780 781config HAVE_COPY_THREAD_TLS 782 bool 783 help 784 Architecture provides copy_thread_tls to accept tls argument via 785 normal C parameter passing, rather than extracting the syscall 786 argument from pt_regs. 787 788config HAVE_STACK_VALIDATION 789 bool 790 help 791 Architecture supports the 'objtool check' host tool command, which 792 performs compile-time stack metadata validation. 793 794config HAVE_RELIABLE_STACKTRACE 795 bool 796 help 797 Architecture has a save_stack_trace_tsk_reliable() function which 798 only returns a stack trace if it can guarantee the trace is reliable. 799 800config HAVE_ARCH_HASH 801 bool 802 default n 803 help 804 If this is set, the architecture provides an <asm/hash.h> 805 file which provides platform-specific implementations of some 806 functions in <linux/hash.h> or fs/namei.c. 807 808config ISA_BUS_API 809 def_bool ISA 810 811# 812# ABI hall of shame 813# 814config CLONE_BACKWARDS 815 bool 816 help 817 Architecture has tls passed as the 4th argument of clone(2), 818 not the 5th one. 819 820config CLONE_BACKWARDS2 821 bool 822 help 823 Architecture has the first two arguments of clone(2) swapped. 824 825config CLONE_BACKWARDS3 826 bool 827 help 828 Architecture has tls passed as the 3rd argument of clone(2), 829 not the 5th one. 830 831config ODD_RT_SIGACTION 832 bool 833 help 834 Architecture has unusual rt_sigaction(2) arguments 835 836config OLD_SIGSUSPEND 837 bool 838 help 839 Architecture has old sigsuspend(2) syscall, of one-argument variety 840 841config OLD_SIGSUSPEND3 842 bool 843 help 844 Even weirder antique ABI - three-argument sigsuspend(2) 845 846config OLD_SIGACTION 847 bool 848 help 849 Architecture has old sigaction(2) syscall. Nope, not the same 850 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 851 but fairly different variant of sigaction(2), thanks to OSF/1 852 compatibility... 853 854config COMPAT_OLD_SIGACTION 855 bool 856 857config ARCH_NO_COHERENT_DMA_MMAP 858 bool 859 860config CPU_NO_EFFICIENT_FFS 861 def_bool n 862 863config HAVE_ARCH_VMAP_STACK 864 def_bool n 865 help 866 An arch should select this symbol if it can support kernel stacks 867 in vmalloc space. This means: 868 869 - vmalloc space must be large enough to hold many kernel stacks. 870 This may rule out many 32-bit architectures. 871 872 - Stacks in vmalloc space need to work reliably. For example, if 873 vmap page tables are created on demand, either this mechanism 874 needs to work while the stack points to a virtual address with 875 unpopulated page tables or arch code (switch_to() and switch_mm(), 876 most likely) needs to ensure that the stack's page table entries 877 are populated before running on a possibly unpopulated stack. 878 879 - If the stack overflows into a guard page, something reasonable 880 should happen. The definition of "reasonable" is flexible, but 881 instantly rebooting without logging anything would be unfriendly. 882 883config VMAP_STACK 884 default y 885 bool "Use a virtually-mapped stack" 886 depends on HAVE_ARCH_VMAP_STACK && !KASAN 887 ---help--- 888 Enable this if you want the use virtually-mapped kernel stacks 889 with guard pages. This causes kernel stack overflows to be 890 caught immediately rather than causing difficult-to-diagnose 891 corruption. 892 893 This is presently incompatible with KASAN because KASAN expects 894 the stack to map directly to the KASAN shadow map using a formula 895 that is incorrect if the stack is in vmalloc space. 896 897config ARCH_OPTIONAL_KERNEL_RWX 898 def_bool n 899 900config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 901 def_bool n 902 903config ARCH_HAS_STRICT_KERNEL_RWX 904 def_bool n 905 906config STRICT_KERNEL_RWX 907 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 908 depends on ARCH_HAS_STRICT_KERNEL_RWX 909 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 910 help 911 If this is set, kernel text and rodata memory will be made read-only, 912 and non-text memory will be made non-executable. This provides 913 protection against certain security exploits (e.g. executing the heap 914 or modifying text) 915 916 These features are considered standard security practice these days. 917 You should say Y here in almost all cases. 918 919config ARCH_HAS_STRICT_MODULE_RWX 920 def_bool n 921 922config STRICT_MODULE_RWX 923 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 924 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 925 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 926 help 927 If this is set, module text and rodata memory will be made read-only, 928 and non-text memory will be made non-executable. This provides 929 protection against certain security exploits (e.g. writing to text) 930 931config ARCH_WANT_RELAX_ORDER 932 bool 933 934config REFCOUNT_FULL 935 bool "Perform full reference count validation at the expense of speed" 936 help 937 Enabling this switches the refcounting infrastructure from a fast 938 unchecked atomic_t implementation to a fully state checked 939 implementation, which can be (slightly) slower but provides protections 940 against various use-after-free conditions that can be used in 941 security flaw exploits. 942 943source "kernel/gcov/Kconfig" 944