1# SPDX-License-Identifier: GPL-2.0 2# 3# General architecture dependent options 4# 5 6config CRASH_CORE 7 bool 8 9config KEXEC_CORE 10 select CRASH_CORE 11 bool 12 13config HAVE_IMA_KEXEC 14 bool 15 16config OPROFILE 17 tristate "OProfile system profiling" 18 depends on PROFILING 19 depends on HAVE_OPROFILE 20 select RING_BUFFER 21 select RING_BUFFER_ALLOW_SWAP 22 help 23 OProfile is a profiling system capable of profiling the 24 whole system, include the kernel, kernel modules, libraries, 25 and applications. 26 27 If unsure, say N. 28 29config OPROFILE_EVENT_MULTIPLEX 30 bool "OProfile multiplexing support (EXPERIMENTAL)" 31 default n 32 depends on OPROFILE && X86 33 help 34 The number of hardware counters is limited. The multiplexing 35 feature enables OProfile to gather more events than counters 36 are provided by the hardware. This is realized by switching 37 between events at a user specified time interval. 38 39 If unsure, say N. 40 41config HAVE_OPROFILE 42 bool 43 44config OPROFILE_NMI_TIMER 45 def_bool y 46 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 47 48config KPROBES 49 bool "Kprobes" 50 depends on MODULES 51 depends on HAVE_KPROBES 52 select KALLSYMS 53 help 54 Kprobes allows you to trap at almost any kernel address and 55 execute a callback function. register_kprobe() establishes 56 a probepoint and specifies the callback. Kprobes is useful 57 for kernel debugging, non-intrusive instrumentation and testing. 58 If in doubt, say "N". 59 60config JUMP_LABEL 61 bool "Optimize very unlikely/likely branches" 62 depends on HAVE_ARCH_JUMP_LABEL 63 help 64 This option enables a transparent branch optimization that 65 makes certain almost-always-true or almost-always-false branch 66 conditions even cheaper to execute within the kernel. 67 68 Certain performance-sensitive kernel code, such as trace points, 69 scheduler functionality, networking code and KVM have such 70 branches and include support for this optimization technique. 71 72 If it is detected that the compiler has support for "asm goto", 73 the kernel will compile such branches with just a nop 74 instruction. When the condition flag is toggled to true, the 75 nop will be converted to a jump instruction to execute the 76 conditional block of instructions. 77 78 This technique lowers overhead and stress on the branch prediction 79 of the processor and generally makes the kernel faster. The update 80 of the condition is slower, but those are always very rare. 81 82 ( On 32-bit x86, the necessary options added to the compiler 83 flags may increase the size of the kernel slightly. ) 84 85config STATIC_KEYS_SELFTEST 86 bool "Static key selftest" 87 depends on JUMP_LABEL 88 help 89 Boot time self-test of the branch patching code. 90 91config OPTPROBES 92 def_bool y 93 depends on KPROBES && HAVE_OPTPROBES 94 select TASKS_RCU if PREEMPT 95 96config KPROBES_ON_FTRACE 97 def_bool y 98 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 99 depends on DYNAMIC_FTRACE_WITH_REGS 100 help 101 If function tracer is enabled and the arch supports full 102 passing of pt_regs to function tracing, then kprobes can 103 optimize on top of function tracing. 104 105config UPROBES 106 def_bool n 107 depends on ARCH_SUPPORTS_UPROBES 108 help 109 Uprobes is the user-space counterpart to kprobes: they 110 enable instrumentation applications (such as 'perf probe') 111 to establish unintrusive probes in user-space binaries and 112 libraries, by executing handler functions when the probes 113 are hit by user-space applications. 114 115 ( These probes come in the form of single-byte breakpoints, 116 managed by the kernel and kept transparent to the probed 117 application. ) 118 119config HAVE_64BIT_ALIGNED_ACCESS 120 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 121 help 122 Some architectures require 64 bit accesses to be 64 bit 123 aligned, which also requires structs containing 64 bit values 124 to be 64 bit aligned too. This includes some 32 bit 125 architectures which can do 64 bit accesses, as well as 64 bit 126 architectures without unaligned access. 127 128 This symbol should be selected by an architecture if 64 bit 129 accesses are required to be 64 bit aligned in this way even 130 though it is not a 64 bit architecture. 131 132 See Documentation/unaligned-memory-access.txt for more 133 information on the topic of unaligned memory accesses. 134 135config HAVE_EFFICIENT_UNALIGNED_ACCESS 136 bool 137 help 138 Some architectures are unable to perform unaligned accesses 139 without the use of get_unaligned/put_unaligned. Others are 140 unable to perform such accesses efficiently (e.g. trap on 141 unaligned access and require fixing it up in the exception 142 handler.) 143 144 This symbol should be selected by an architecture if it can 145 perform unaligned accesses efficiently to allow different 146 code paths to be selected for these cases. Some network 147 drivers, for example, could opt to not fix up alignment 148 problems with received packets if doing so would not help 149 much. 150 151 See Documentation/unaligned-memory-access.txt for more 152 information on the topic of unaligned memory accesses. 153 154config ARCH_USE_BUILTIN_BSWAP 155 bool 156 help 157 Modern versions of GCC (since 4.4) have builtin functions 158 for handling byte-swapping. Using these, instead of the old 159 inline assembler that the architecture code provides in the 160 __arch_bswapXX() macros, allows the compiler to see what's 161 happening and offers more opportunity for optimisation. In 162 particular, the compiler will be able to combine the byteswap 163 with a nearby load or store and use load-and-swap or 164 store-and-swap instructions if the architecture has them. It 165 should almost *never* result in code which is worse than the 166 hand-coded assembler in <asm/swab.h>. But just in case it 167 does, the use of the builtins is optional. 168 169 Any architecture with load-and-swap or store-and-swap 170 instructions should set this. And it shouldn't hurt to set it 171 on architectures that don't have such instructions. 172 173config KRETPROBES 174 def_bool y 175 depends on KPROBES && HAVE_KRETPROBES 176 177config USER_RETURN_NOTIFIER 178 bool 179 depends on HAVE_USER_RETURN_NOTIFIER 180 help 181 Provide a kernel-internal notification when a cpu is about to 182 switch to user mode. 183 184config HAVE_IOREMAP_PROT 185 bool 186 187config HAVE_KPROBES 188 bool 189 190config HAVE_KRETPROBES 191 bool 192 193config HAVE_OPTPROBES 194 bool 195 196config HAVE_KPROBES_ON_FTRACE 197 bool 198 199config HAVE_FUNCTION_ERROR_INJECTION 200 bool 201 202config HAVE_NMI 203 bool 204 205# 206# An arch should select this if it provides all these things: 207# 208# task_pt_regs() in asm/processor.h or asm/ptrace.h 209# arch_has_single_step() if there is hardware single-step support 210# arch_has_block_step() if there is hardware block-step support 211# asm/syscall.h supplying asm-generic/syscall.h interface 212# linux/regset.h user_regset interfaces 213# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 214# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 215# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 216# signal delivery calls tracehook_signal_handler() 217# 218config HAVE_ARCH_TRACEHOOK 219 bool 220 221config HAVE_DMA_CONTIGUOUS 222 bool 223 224config GENERIC_SMP_IDLE_THREAD 225 bool 226 227config GENERIC_IDLE_POLL_SETUP 228 bool 229 230config ARCH_HAS_FORTIFY_SOURCE 231 bool 232 help 233 An architecture should select this when it can successfully 234 build and run with CONFIG_FORTIFY_SOURCE. 235 236# Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h 237config ARCH_HAS_SET_MEMORY 238 bool 239 240# Select if arch init_task must go in the __init_task_data section 241config ARCH_TASK_STRUCT_ON_STACK 242 bool 243 244# Select if arch has its private alloc_task_struct() function 245config ARCH_TASK_STRUCT_ALLOCATOR 246 bool 247 248config HAVE_ARCH_THREAD_STRUCT_WHITELIST 249 bool 250 depends on !ARCH_TASK_STRUCT_ALLOCATOR 251 help 252 An architecture should select this to provide hardened usercopy 253 knowledge about what region of the thread_struct should be 254 whitelisted for copying to userspace. Normally this is only the 255 FPU registers. Specifically, arch_thread_struct_whitelist() 256 should be implemented. Without this, the entire thread_struct 257 field in task_struct will be left whitelisted. 258 259# Select if arch has its private alloc_thread_stack() function 260config ARCH_THREAD_STACK_ALLOCATOR 261 bool 262 263# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 264config ARCH_WANTS_DYNAMIC_TASK_STRUCT 265 bool 266 267config HAVE_REGS_AND_STACK_ACCESS_API 268 bool 269 help 270 This symbol should be selected by an architecure if it supports 271 the API needed to access registers and stack entries from pt_regs, 272 declared in asm/ptrace.h 273 For example the kprobes-based event tracer needs this API. 274 275config HAVE_CLK 276 bool 277 help 278 The <linux/clk.h> calls support software clock gating and 279 thus are a key power management tool on many systems. 280 281config HAVE_HW_BREAKPOINT 282 bool 283 depends on PERF_EVENTS 284 285config HAVE_MIXED_BREAKPOINTS_REGS 286 bool 287 depends on HAVE_HW_BREAKPOINT 288 help 289 Depending on the arch implementation of hardware breakpoints, 290 some of them have separate registers for data and instruction 291 breakpoints addresses, others have mixed registers to store 292 them but define the access type in a control register. 293 Select this option if your arch implements breakpoints under the 294 latter fashion. 295 296config HAVE_USER_RETURN_NOTIFIER 297 bool 298 299config HAVE_PERF_EVENTS_NMI 300 bool 301 help 302 System hardware can generate an NMI using the perf event 303 subsystem. Also has support for calculating CPU cycle events 304 to determine how many clock cycles in a given period. 305 306config HAVE_HARDLOCKUP_DETECTOR_PERF 307 bool 308 depends on HAVE_PERF_EVENTS_NMI 309 help 310 The arch chooses to use the generic perf-NMI-based hardlockup 311 detector. Must define HAVE_PERF_EVENTS_NMI. 312 313config HAVE_NMI_WATCHDOG 314 depends on HAVE_NMI 315 bool 316 help 317 The arch provides a low level NMI watchdog. It provides 318 asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). 319 320config HAVE_HARDLOCKUP_DETECTOR_ARCH 321 bool 322 select HAVE_NMI_WATCHDOG 323 help 324 The arch chooses to provide its own hardlockup detector, which is 325 a superset of the HAVE_NMI_WATCHDOG. It also conforms to config 326 interfaces and parameters provided by hardlockup detector subsystem. 327 328config HAVE_PERF_REGS 329 bool 330 help 331 Support selective register dumps for perf events. This includes 332 bit-mapping of each registers and a unique architecture id. 333 334config HAVE_PERF_USER_STACK_DUMP 335 bool 336 help 337 Support user stack dumps for perf event samples. This needs 338 access to the user stack pointer which is not unified across 339 architectures. 340 341config HAVE_ARCH_JUMP_LABEL 342 bool 343 344config HAVE_RCU_TABLE_FREE 345 bool 346 347config ARCH_HAVE_NMI_SAFE_CMPXCHG 348 bool 349 350config HAVE_ALIGNED_STRUCT_PAGE 351 bool 352 help 353 This makes sure that struct pages are double word aligned and that 354 e.g. the SLUB allocator can perform double word atomic operations 355 on a struct page for better performance. However selecting this 356 might increase the size of a struct page by a word. 357 358config HAVE_CMPXCHG_LOCAL 359 bool 360 361config HAVE_CMPXCHG_DOUBLE 362 bool 363 364config ARCH_WEAK_RELEASE_ACQUIRE 365 bool 366 367config ARCH_WANT_IPC_PARSE_VERSION 368 bool 369 370config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 371 bool 372 373config ARCH_WANT_OLD_COMPAT_IPC 374 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 375 bool 376 377config HAVE_ARCH_SECCOMP_FILTER 378 bool 379 help 380 An arch should select this symbol if it provides all of these things: 381 - syscall_get_arch() 382 - syscall_get_arguments() 383 - syscall_rollback() 384 - syscall_set_return_value() 385 - SIGSYS siginfo_t support 386 - secure_computing is called from a ptrace_event()-safe context 387 - secure_computing return value is checked and a return value of -1 388 results in the system call being skipped immediately. 389 - seccomp syscall wired up 390 391config SECCOMP_FILTER 392 def_bool y 393 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 394 help 395 Enable tasks to build secure computing environments defined 396 in terms of Berkeley Packet Filter programs which implement 397 task-defined system call filtering polices. 398 399 See Documentation/prctl/seccomp_filter.txt for details. 400 401config HAVE_GCC_PLUGINS 402 bool 403 help 404 An arch should select this symbol if it supports building with 405 GCC plugins. 406 407menuconfig GCC_PLUGINS 408 bool "GCC plugins" 409 depends on HAVE_GCC_PLUGINS 410 depends on !COMPILE_TEST 411 help 412 GCC plugins are loadable modules that provide extra features to the 413 compiler. They are useful for runtime instrumentation and static analysis. 414 415 See Documentation/gcc-plugins.txt for details. 416 417config GCC_PLUGIN_CYC_COMPLEXITY 418 bool "Compute the cyclomatic complexity of a function" if EXPERT 419 depends on GCC_PLUGINS 420 depends on !COMPILE_TEST 421 help 422 The complexity M of a function's control flow graph is defined as: 423 M = E - N + 2P 424 where 425 426 E = the number of edges 427 N = the number of nodes 428 P = the number of connected components (exit nodes). 429 430 Enabling this plugin reports the complexity to stderr during the 431 build. It mainly serves as a simple example of how to create a 432 gcc plugin for the kernel. 433 434config GCC_PLUGIN_SANCOV 435 bool 436 depends on GCC_PLUGINS 437 help 438 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 439 basic blocks. It supports all gcc versions with plugin support (from 440 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 441 by Dmitry Vyukov <dvyukov@google.com>. 442 443config GCC_PLUGIN_LATENT_ENTROPY 444 bool "Generate some entropy during boot and runtime" 445 depends on GCC_PLUGINS 446 help 447 By saying Y here the kernel will instrument some kernel code to 448 extract some entropy from both original and artificially created 449 program state. This will help especially embedded systems where 450 there is little 'natural' source of entropy normally. The cost 451 is some slowdown of the boot process (about 0.5%) and fork and 452 irq processing. 453 454 Note that entropy extracted this way is not cryptographically 455 secure! 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 462 bool "Force initialization of variables containing userspace addresses" 463 depends on GCC_PLUGINS 464 # Currently STRUCTLEAK inserts initialization out of live scope of 465 # variables from KASAN point of view. This leads to KASAN false 466 # positive reports. Prohibit this combination for now. 467 depends on !KASAN_EXTRA 468 help 469 This plugin zero-initializes any structures containing a 470 __user attribute. This can prevent some classes of information 471 exposures. 472 473 This plugin was ported from grsecurity/PaX. More information at: 474 * https://grsecurity.net/ 475 * https://pax.grsecurity.net/ 476 477config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL 478 bool "Force initialize all struct type variables passed by reference" 479 depends on GCC_PLUGIN_STRUCTLEAK 480 help 481 Zero initialize any struct type local variable that may be passed by 482 reference without having been initialized. 483 484config GCC_PLUGIN_STRUCTLEAK_VERBOSE 485 bool "Report forcefully initialized variables" 486 depends on GCC_PLUGIN_STRUCTLEAK 487 depends on !COMPILE_TEST 488 help 489 This option will cause a warning to be printed each time the 490 structleak plugin finds a variable it thinks needs to be 491 initialized. Since not all existing initializers are detected 492 by the plugin, this can produce false positive warnings. 493 494config GCC_PLUGIN_RANDSTRUCT 495 bool "Randomize layout of sensitive kernel structures" 496 depends on GCC_PLUGINS 497 select MODVERSIONS if MODULES 498 help 499 If you say Y here, the layouts of structures that are entirely 500 function pointers (and have not been manually annotated with 501 __no_randomize_layout), or structures that have been explicitly 502 marked with __randomize_layout, will be randomized at compile-time. 503 This can introduce the requirement of an additional information 504 exposure vulnerability for exploits targeting these structure 505 types. 506 507 Enabling this feature will introduce some performance impact, 508 slightly increase memory usage, and prevent the use of forensic 509 tools like Volatility against the system (unless the kernel 510 source tree isn't cleaned after kernel installation). 511 512 The seed used for compilation is located at 513 scripts/gcc-plgins/randomize_layout_seed.h. It remains after 514 a make clean to allow for external modules to be compiled with 515 the existing seed and will be removed by a make mrproper or 516 make distclean. 517 518 Note that the implementation requires gcc 4.7 or newer. 519 520 This plugin was ported from grsecurity/PaX. More information at: 521 * https://grsecurity.net/ 522 * https://pax.grsecurity.net/ 523 524config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE 525 bool "Use cacheline-aware structure randomization" 526 depends on GCC_PLUGIN_RANDSTRUCT 527 depends on !COMPILE_TEST 528 help 529 If you say Y here, the RANDSTRUCT randomization will make a 530 best effort at restricting randomization to cacheline-sized 531 groups of elements. It will further not randomize bitfields 532 in structures. This reduces the performance hit of RANDSTRUCT 533 at the cost of weakened randomization. 534 535config HAVE_CC_STACKPROTECTOR 536 bool 537 help 538 An arch should select this symbol if: 539 - its compiler supports the -fstack-protector option 540 - it has implemented a stack canary (e.g. __stack_chk_guard) 541 542choice 543 prompt "Stack Protector buffer overflow detection" 544 depends on HAVE_CC_STACKPROTECTOR 545 default CC_STACKPROTECTOR_AUTO 546 help 547 This option turns on the "stack-protector" GCC feature. This 548 feature puts, at the beginning of functions, a canary value on 549 the stack just before the return address, and validates 550 the value just before actually returning. Stack based buffer 551 overflows (that need to overwrite this return address) now also 552 overwrite the canary, which gets detected and the attack is then 553 neutralized via a kernel panic. 554 555config CC_STACKPROTECTOR_NONE 556 bool "None" 557 help 558 Disable "stack-protector" GCC feature. 559 560config CC_STACKPROTECTOR_REGULAR 561 bool "Regular" 562 help 563 Functions will have the stack-protector canary logic added if they 564 have an 8-byte or larger character array on the stack. 565 566 This feature requires gcc version 4.2 or above, or a distribution 567 gcc with the feature backported ("-fstack-protector"). 568 569 On an x86 "defconfig" build, this feature adds canary checks to 570 about 3% of all kernel functions, which increases kernel code size 571 by about 0.3%. 572 573config CC_STACKPROTECTOR_STRONG 574 bool "Strong" 575 help 576 Functions will have the stack-protector canary logic added in any 577 of the following conditions: 578 579 - local variable's address used as part of the right hand side of an 580 assignment or function argument 581 - local variable is an array (or union containing an array), 582 regardless of array type or length 583 - uses register local variables 584 585 This feature requires gcc version 4.9 or above, or a distribution 586 gcc with the feature backported ("-fstack-protector-strong"). 587 588 On an x86 "defconfig" build, this feature adds canary checks to 589 about 20% of all kernel functions, which increases the kernel code 590 size by about 2%. 591 592config CC_STACKPROTECTOR_AUTO 593 bool "Automatic" 594 help 595 If the compiler supports it, the best available stack-protector 596 option will be chosen. 597 598endchoice 599 600config LD_DEAD_CODE_DATA_ELIMINATION 601 bool 602 help 603 Select this if the architecture wants to do dead code and 604 data elimination with the linker by compiling with 605 -ffunction-sections -fdata-sections and linking with 606 --gc-sections. 607 608 This requires that the arch annotates or otherwise protects 609 its external entry points from being discarded. Linker scripts 610 must also merge .text.*, .data.*, and .bss.* correctly into 611 output sections. Care must be taken not to pull in unrelated 612 sections (e.g., '.text.init'). Typically '.' in section names 613 is used to distinguish them from label names / C identifiers. 614 615config HAVE_ARCH_WITHIN_STACK_FRAMES 616 bool 617 help 618 An architecture should select this if it can walk the kernel stack 619 frames to determine if an object is part of either the arguments 620 or local variables (i.e. that it excludes saved return addresses, 621 and similar) by implementing an inline arch_within_stack_frames(), 622 which is used by CONFIG_HARDENED_USERCOPY. 623 624config HAVE_CONTEXT_TRACKING 625 bool 626 help 627 Provide kernel/user boundaries probes necessary for subsystems 628 that need it, such as userspace RCU extended quiescent state. 629 Syscalls need to be wrapped inside user_exit()-user_enter() through 630 the slow path using TIF_NOHZ flag. Exceptions handlers must be 631 wrapped as well. Irqs are already protected inside 632 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 633 irq exit still need to be protected. 634 635config HAVE_VIRT_CPU_ACCOUNTING 636 bool 637 638config ARCH_HAS_SCALED_CPUTIME 639 bool 640 641config HAVE_VIRT_CPU_ACCOUNTING_GEN 642 bool 643 default y if 64BIT 644 help 645 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 646 Before enabling this option, arch code must be audited 647 to ensure there are no races in concurrent read/write of 648 cputime_t. For example, reading/writing 64-bit cputime_t on 649 some 32-bit arches may require multiple accesses, so proper 650 locking is needed to protect against concurrent accesses. 651 652 653config HAVE_IRQ_TIME_ACCOUNTING 654 bool 655 help 656 Archs need to ensure they use a high enough resolution clock to 657 support irq time accounting and then call enable_sched_clock_irqtime(). 658 659config HAVE_ARCH_TRANSPARENT_HUGEPAGE 660 bool 661 662config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 663 bool 664 665config HAVE_ARCH_HUGE_VMAP 666 bool 667 668config HAVE_ARCH_SOFT_DIRTY 669 bool 670 671config HAVE_MOD_ARCH_SPECIFIC 672 bool 673 help 674 The arch uses struct mod_arch_specific to store data. Many arches 675 just need a simple module loader without arch specific data - those 676 should not enable this. 677 678config MODULES_USE_ELF_RELA 679 bool 680 help 681 Modules only use ELF RELA relocations. Modules with ELF REL 682 relocations will give an error. 683 684config MODULES_USE_ELF_REL 685 bool 686 help 687 Modules only use ELF REL relocations. Modules with ELF RELA 688 relocations will give an error. 689 690config HAVE_UNDERSCORE_SYMBOL_PREFIX 691 bool 692 help 693 Some architectures generate an _ in front of C symbols; things like 694 module loading and assembly files need to know about this. 695 696config HAVE_IRQ_EXIT_ON_IRQ_STACK 697 bool 698 help 699 Architecture doesn't only execute the irq handler on the irq stack 700 but also irq_exit(). This way we can process softirqs on this irq 701 stack instead of switching to a new one when we call __do_softirq() 702 in the end of an hardirq. 703 This spares a stack switch and improves cache usage on softirq 704 processing. 705 706config PGTABLE_LEVELS 707 int 708 default 2 709 710config ARCH_HAS_ELF_RANDOMIZE 711 bool 712 help 713 An architecture supports choosing randomized locations for 714 stack, mmap, brk, and ET_DYN. Defined functions: 715 - arch_mmap_rnd() 716 - arch_randomize_brk() 717 718config HAVE_ARCH_MMAP_RND_BITS 719 bool 720 help 721 An arch should select this symbol if it supports setting a variable 722 number of bits for use in establishing the base address for mmap 723 allocations, has MMU enabled and provides values for both: 724 - ARCH_MMAP_RND_BITS_MIN 725 - ARCH_MMAP_RND_BITS_MAX 726 727config HAVE_EXIT_THREAD 728 bool 729 help 730 An architecture implements exit_thread. 731 732config ARCH_MMAP_RND_BITS_MIN 733 int 734 735config ARCH_MMAP_RND_BITS_MAX 736 int 737 738config ARCH_MMAP_RND_BITS_DEFAULT 739 int 740 741config ARCH_MMAP_RND_BITS 742 int "Number of bits to use for ASLR of mmap base address" if EXPERT 743 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 744 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 745 default ARCH_MMAP_RND_BITS_MIN 746 depends on HAVE_ARCH_MMAP_RND_BITS 747 help 748 This value can be used to select the number of bits to use to 749 determine the random offset to the base address of vma regions 750 resulting from mmap allocations. This value will be bounded 751 by the architecture's minimum and maximum supported values. 752 753 This value can be changed after boot using the 754 /proc/sys/vm/mmap_rnd_bits tunable 755 756config HAVE_ARCH_MMAP_RND_COMPAT_BITS 757 bool 758 help 759 An arch should select this symbol if it supports running applications 760 in compatibility mode, supports setting a variable number of bits for 761 use in establishing the base address for mmap allocations, has MMU 762 enabled and provides values for both: 763 - ARCH_MMAP_RND_COMPAT_BITS_MIN 764 - ARCH_MMAP_RND_COMPAT_BITS_MAX 765 766config ARCH_MMAP_RND_COMPAT_BITS_MIN 767 int 768 769config ARCH_MMAP_RND_COMPAT_BITS_MAX 770 int 771 772config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 773 int 774 775config ARCH_MMAP_RND_COMPAT_BITS 776 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 777 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 778 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 779 default ARCH_MMAP_RND_COMPAT_BITS_MIN 780 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 781 help 782 This value can be used to select the number of bits to use to 783 determine the random offset to the base address of vma regions 784 resulting from mmap allocations for compatible applications This 785 value will be bounded by the architecture's minimum and maximum 786 supported values. 787 788 This value can be changed after boot using the 789 /proc/sys/vm/mmap_rnd_compat_bits tunable 790 791config HAVE_ARCH_COMPAT_MMAP_BASES 792 bool 793 help 794 This allows 64bit applications to invoke 32-bit mmap() syscall 795 and vice-versa 32-bit applications to call 64-bit mmap(). 796 Required for applications doing different bitness syscalls. 797 798config HAVE_COPY_THREAD_TLS 799 bool 800 help 801 Architecture provides copy_thread_tls to accept tls argument via 802 normal C parameter passing, rather than extracting the syscall 803 argument from pt_regs. 804 805config HAVE_STACK_VALIDATION 806 bool 807 help 808 Architecture supports the 'objtool check' host tool command, which 809 performs compile-time stack metadata validation. 810 811config HAVE_RELIABLE_STACKTRACE 812 bool 813 help 814 Architecture has a save_stack_trace_tsk_reliable() function which 815 only returns a stack trace if it can guarantee the trace is reliable. 816 817config HAVE_ARCH_HASH 818 bool 819 default n 820 help 821 If this is set, the architecture provides an <asm/hash.h> 822 file which provides platform-specific implementations of some 823 functions in <linux/hash.h> or fs/namei.c. 824 825config ISA_BUS_API 826 def_bool ISA 827 828# 829# ABI hall of shame 830# 831config CLONE_BACKWARDS 832 bool 833 help 834 Architecture has tls passed as the 4th argument of clone(2), 835 not the 5th one. 836 837config CLONE_BACKWARDS2 838 bool 839 help 840 Architecture has the first two arguments of clone(2) swapped. 841 842config CLONE_BACKWARDS3 843 bool 844 help 845 Architecture has tls passed as the 3rd argument of clone(2), 846 not the 5th one. 847 848config ODD_RT_SIGACTION 849 bool 850 help 851 Architecture has unusual rt_sigaction(2) arguments 852 853config OLD_SIGSUSPEND 854 bool 855 help 856 Architecture has old sigsuspend(2) syscall, of one-argument variety 857 858config OLD_SIGSUSPEND3 859 bool 860 help 861 Even weirder antique ABI - three-argument sigsuspend(2) 862 863config OLD_SIGACTION 864 bool 865 help 866 Architecture has old sigaction(2) syscall. Nope, not the same 867 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 868 but fairly different variant of sigaction(2), thanks to OSF/1 869 compatibility... 870 871config COMPAT_OLD_SIGACTION 872 bool 873 874config ARCH_NO_COHERENT_DMA_MMAP 875 bool 876 877config CPU_NO_EFFICIENT_FFS 878 def_bool n 879 880config HAVE_ARCH_VMAP_STACK 881 def_bool n 882 help 883 An arch should select this symbol if it can support kernel stacks 884 in vmalloc space. This means: 885 886 - vmalloc space must be large enough to hold many kernel stacks. 887 This may rule out many 32-bit architectures. 888 889 - Stacks in vmalloc space need to work reliably. For example, if 890 vmap page tables are created on demand, either this mechanism 891 needs to work while the stack points to a virtual address with 892 unpopulated page tables or arch code (switch_to() and switch_mm(), 893 most likely) needs to ensure that the stack's page table entries 894 are populated before running on a possibly unpopulated stack. 895 896 - If the stack overflows into a guard page, something reasonable 897 should happen. The definition of "reasonable" is flexible, but 898 instantly rebooting without logging anything would be unfriendly. 899 900config VMAP_STACK 901 default y 902 bool "Use a virtually-mapped stack" 903 depends on HAVE_ARCH_VMAP_STACK && !KASAN 904 ---help--- 905 Enable this if you want the use virtually-mapped kernel stacks 906 with guard pages. This causes kernel stack overflows to be 907 caught immediately rather than causing difficult-to-diagnose 908 corruption. 909 910 This is presently incompatible with KASAN because KASAN expects 911 the stack to map directly to the KASAN shadow map using a formula 912 that is incorrect if the stack is in vmalloc space. 913 914config ARCH_OPTIONAL_KERNEL_RWX 915 def_bool n 916 917config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 918 def_bool n 919 920config ARCH_HAS_STRICT_KERNEL_RWX 921 def_bool n 922 923config STRICT_KERNEL_RWX 924 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX 925 depends on ARCH_HAS_STRICT_KERNEL_RWX 926 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 927 help 928 If this is set, kernel text and rodata memory will be made read-only, 929 and non-text memory will be made non-executable. This provides 930 protection against certain security exploits (e.g. executing the heap 931 or modifying text) 932 933 These features are considered standard security practice these days. 934 You should say Y here in almost all cases. 935 936config ARCH_HAS_STRICT_MODULE_RWX 937 def_bool n 938 939config STRICT_MODULE_RWX 940 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX 941 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES 942 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 943 help 944 If this is set, module text and rodata memory will be made read-only, 945 and non-text memory will be made non-executable. This provides 946 protection against certain security exploits (e.g. writing to text) 947 948# select if the architecture provides an asm/dma-direct.h header 949config ARCH_HAS_PHYS_TO_DMA 950 bool 951 952config ARCH_HAS_REFCOUNT 953 bool 954 help 955 An architecture selects this when it has implemented refcount_t 956 using open coded assembly primitives that provide an optimized 957 refcount_t implementation, possibly at the expense of some full 958 refcount state checks of CONFIG_REFCOUNT_FULL=y. 959 960 The refcount overflow check behavior, however, must be retained. 961 Catching overflows is the primary security concern for protecting 962 against bugs in reference counts. 963 964config REFCOUNT_FULL 965 bool "Perform full reference count validation at the expense of speed" 966 help 967 Enabling this switches the refcounting infrastructure from a fast 968 unchecked atomic_t implementation to a fully state checked 969 implementation, which can be (slightly) slower but provides protections 970 against various use-after-free conditions that can be used in 971 security flaw exploits. 972 973source "kernel/gcov/Kconfig" 974