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