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