1# 2# General architecture dependent options 3# 4 5config KEXEC_CORE 6 bool 7 8config OPROFILE 9 tristate "OProfile system profiling" 10 depends on PROFILING 11 depends on HAVE_OPROFILE 12 select RING_BUFFER 13 select RING_BUFFER_ALLOW_SWAP 14 help 15 OProfile is a profiling system capable of profiling the 16 whole system, include the kernel, kernel modules, libraries, 17 and applications. 18 19 If unsure, say N. 20 21config OPROFILE_EVENT_MULTIPLEX 22 bool "OProfile multiplexing support (EXPERIMENTAL)" 23 default n 24 depends on OPROFILE && X86 25 help 26 The number of hardware counters is limited. The multiplexing 27 feature enables OProfile to gather more events than counters 28 are provided by the hardware. This is realized by switching 29 between events at an user specified time interval. 30 31 If unsure, say N. 32 33config HAVE_OPROFILE 34 bool 35 36config OPROFILE_NMI_TIMER 37 def_bool y 38 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64 39 40config KPROBES 41 bool "Kprobes" 42 depends on MODULES 43 depends on HAVE_KPROBES 44 select KALLSYMS 45 help 46 Kprobes allows you to trap at almost any kernel address and 47 execute a callback function. register_kprobe() establishes 48 a probepoint and specifies the callback. Kprobes is useful 49 for kernel debugging, non-intrusive instrumentation and testing. 50 If in doubt, say "N". 51 52config JUMP_LABEL 53 bool "Optimize very unlikely/likely branches" 54 depends on HAVE_ARCH_JUMP_LABEL 55 help 56 This option enables a transparent branch optimization that 57 makes certain almost-always-true or almost-always-false branch 58 conditions even cheaper to execute within the kernel. 59 60 Certain performance-sensitive kernel code, such as trace points, 61 scheduler functionality, networking code and KVM have such 62 branches and include support for this optimization technique. 63 64 If it is detected that the compiler has support for "asm goto", 65 the kernel will compile such branches with just a nop 66 instruction. When the condition flag is toggled to true, the 67 nop will be converted to a jump instruction to execute the 68 conditional block of instructions. 69 70 This technique lowers overhead and stress on the branch prediction 71 of the processor and generally makes the kernel faster. The update 72 of the condition is slower, but those are always very rare. 73 74 ( On 32-bit x86, the necessary options added to the compiler 75 flags may increase the size of the kernel slightly. ) 76 77config STATIC_KEYS_SELFTEST 78 bool "Static key selftest" 79 depends on JUMP_LABEL 80 help 81 Boot time self-test of the branch patching code. 82 83config OPTPROBES 84 def_bool y 85 depends on KPROBES && HAVE_OPTPROBES 86 depends on !PREEMPT 87 88config KPROBES_ON_FTRACE 89 def_bool y 90 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 91 depends on DYNAMIC_FTRACE_WITH_REGS 92 help 93 If function tracer is enabled and the arch supports full 94 passing of pt_regs to function tracing, then kprobes can 95 optimize on top of function tracing. 96 97config UPROBES 98 def_bool n 99 help 100 Uprobes is the user-space counterpart to kprobes: they 101 enable instrumentation applications (such as 'perf probe') 102 to establish unintrusive probes in user-space binaries and 103 libraries, by executing handler functions when the probes 104 are hit by user-space applications. 105 106 ( These probes come in the form of single-byte breakpoints, 107 managed by the kernel and kept transparent to the probed 108 application. ) 109 110config HAVE_64BIT_ALIGNED_ACCESS 111 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 112 help 113 Some architectures require 64 bit accesses to be 64 bit 114 aligned, which also requires structs containing 64 bit values 115 to be 64 bit aligned too. This includes some 32 bit 116 architectures which can do 64 bit accesses, as well as 64 bit 117 architectures without unaligned access. 118 119 This symbol should be selected by an architecture if 64 bit 120 accesses are required to be 64 bit aligned in this way even 121 though it is not a 64 bit architecture. 122 123 See Documentation/unaligned-memory-access.txt for more 124 information on the topic of unaligned memory accesses. 125 126config HAVE_EFFICIENT_UNALIGNED_ACCESS 127 bool 128 help 129 Some architectures are unable to perform unaligned accesses 130 without the use of get_unaligned/put_unaligned. Others are 131 unable to perform such accesses efficiently (e.g. trap on 132 unaligned access and require fixing it up in the exception 133 handler.) 134 135 This symbol should be selected by an architecture if it can 136 perform unaligned accesses efficiently to allow different 137 code paths to be selected for these cases. Some network 138 drivers, for example, could opt to not fix up alignment 139 problems with received packets if doing so would not help 140 much. 141 142 See Documentation/unaligned-memory-access.txt for more 143 information on the topic of unaligned memory accesses. 144 145config ARCH_USE_BUILTIN_BSWAP 146 bool 147 help 148 Modern versions of GCC (since 4.4) have builtin functions 149 for handling byte-swapping. Using these, instead of the old 150 inline assembler that the architecture code provides in the 151 __arch_bswapXX() macros, allows the compiler to see what's 152 happening and offers more opportunity for optimisation. In 153 particular, the compiler will be able to combine the byteswap 154 with a nearby load or store and use load-and-swap or 155 store-and-swap instructions if the architecture has them. It 156 should almost *never* result in code which is worse than the 157 hand-coded assembler in <asm/swab.h>. But just in case it 158 does, the use of the builtins is optional. 159 160 Any architecture with load-and-swap or store-and-swap 161 instructions should set this. And it shouldn't hurt to set it 162 on architectures that don't have such instructions. 163 164config KRETPROBES 165 def_bool y 166 depends on KPROBES && HAVE_KRETPROBES 167 168config USER_RETURN_NOTIFIER 169 bool 170 depends on HAVE_USER_RETURN_NOTIFIER 171 help 172 Provide a kernel-internal notification when a cpu is about to 173 switch to user mode. 174 175config HAVE_IOREMAP_PROT 176 bool 177 178config HAVE_KPROBES 179 bool 180 181config HAVE_KRETPROBES 182 bool 183 184config HAVE_OPTPROBES 185 bool 186 187config HAVE_KPROBES_ON_FTRACE 188 bool 189 190config HAVE_NMI 191 bool 192 193config HAVE_NMI_WATCHDOG 194 depends on HAVE_NMI 195 bool 196# 197# An arch should select this if it provides all these things: 198# 199# task_pt_regs() in asm/processor.h or asm/ptrace.h 200# arch_has_single_step() if there is hardware single-step support 201# arch_has_block_step() if there is hardware block-step support 202# asm/syscall.h supplying asm-generic/syscall.h interface 203# linux/regset.h user_regset interfaces 204# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 205# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 206# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 207# signal delivery calls tracehook_signal_handler() 208# 209config HAVE_ARCH_TRACEHOOK 210 bool 211 212config HAVE_DMA_CONTIGUOUS 213 bool 214 215config GENERIC_SMP_IDLE_THREAD 216 bool 217 218config GENERIC_IDLE_POLL_SETUP 219 bool 220 221# Select if arch init_task initializer is different to init/init_task.c 222config ARCH_INIT_TASK 223 bool 224 225# Select if arch has its private alloc_task_struct() function 226config ARCH_TASK_STRUCT_ALLOCATOR 227 bool 228 229# Select if arch has its private alloc_thread_stack() function 230config ARCH_THREAD_STACK_ALLOCATOR 231 bool 232 233# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 234config ARCH_WANTS_DYNAMIC_TASK_STRUCT 235 bool 236 237config HAVE_REGS_AND_STACK_ACCESS_API 238 bool 239 help 240 This symbol should be selected by an architecure if it supports 241 the API needed to access registers and stack entries from pt_regs, 242 declared in asm/ptrace.h 243 For example the kprobes-based event tracer needs this API. 244 245config HAVE_CLK 246 bool 247 help 248 The <linux/clk.h> calls support software clock gating and 249 thus are a key power management tool on many systems. 250 251config HAVE_DMA_API_DEBUG 252 bool 253 254config HAVE_HW_BREAKPOINT 255 bool 256 depends on PERF_EVENTS 257 258config HAVE_MIXED_BREAKPOINTS_REGS 259 bool 260 depends on HAVE_HW_BREAKPOINT 261 help 262 Depending on the arch implementation of hardware breakpoints, 263 some of them have separate registers for data and instruction 264 breakpoints addresses, others have mixed registers to store 265 them but define the access type in a control register. 266 Select this option if your arch implements breakpoints under the 267 latter fashion. 268 269config HAVE_USER_RETURN_NOTIFIER 270 bool 271 272config HAVE_PERF_EVENTS_NMI 273 bool 274 help 275 System hardware can generate an NMI using the perf event 276 subsystem. Also has support for calculating CPU cycle events 277 to determine how many clock cycles in a given period. 278 279config HAVE_PERF_REGS 280 bool 281 help 282 Support selective register dumps for perf events. This includes 283 bit-mapping of each registers and a unique architecture id. 284 285config HAVE_PERF_USER_STACK_DUMP 286 bool 287 help 288 Support user stack dumps for perf event samples. This needs 289 access to the user stack pointer which is not unified across 290 architectures. 291 292config HAVE_ARCH_JUMP_LABEL 293 bool 294 295config HAVE_RCU_TABLE_FREE 296 bool 297 298config ARCH_HAVE_NMI_SAFE_CMPXCHG 299 bool 300 301config HAVE_ALIGNED_STRUCT_PAGE 302 bool 303 help 304 This makes sure that struct pages are double word aligned and that 305 e.g. the SLUB allocator can perform double word atomic operations 306 on a struct page for better performance. However selecting this 307 might increase the size of a struct page by a word. 308 309config HAVE_CMPXCHG_LOCAL 310 bool 311 312config HAVE_CMPXCHG_DOUBLE 313 bool 314 315config ARCH_WANT_IPC_PARSE_VERSION 316 bool 317 318config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 319 bool 320 321config ARCH_WANT_OLD_COMPAT_IPC 322 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 323 bool 324 325config HAVE_ARCH_SECCOMP_FILTER 326 bool 327 help 328 An arch should select this symbol if it provides all of these things: 329 - syscall_get_arch() 330 - syscall_get_arguments() 331 - syscall_rollback() 332 - syscall_set_return_value() 333 - SIGSYS siginfo_t support 334 - secure_computing is called from a ptrace_event()-safe context 335 - secure_computing return value is checked and a return value of -1 336 results in the system call being skipped immediately. 337 - seccomp syscall wired up 338 339config SECCOMP_FILTER 340 def_bool y 341 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 342 help 343 Enable tasks to build secure computing environments defined 344 in terms of Berkeley Packet Filter programs which implement 345 task-defined system call filtering polices. 346 347 See Documentation/prctl/seccomp_filter.txt for details. 348 349config HAVE_GCC_PLUGINS 350 bool 351 help 352 An arch should select this symbol if it supports building with 353 GCC plugins. 354 355menuconfig GCC_PLUGINS 356 bool "GCC plugins" 357 depends on HAVE_GCC_PLUGINS 358 depends on !COMPILE_TEST 359 help 360 GCC plugins are loadable modules that provide extra features to the 361 compiler. They are useful for runtime instrumentation and static analysis. 362 363 See Documentation/gcc-plugins.txt for details. 364 365config GCC_PLUGIN_CYC_COMPLEXITY 366 bool "Compute the cyclomatic complexity of a function" 367 depends on GCC_PLUGINS 368 help 369 The complexity M of a function's control flow graph is defined as: 370 M = E - N + 2P 371 where 372 373 E = the number of edges 374 N = the number of nodes 375 P = the number of connected components (exit nodes). 376 377config GCC_PLUGIN_SANCOV 378 bool 379 depends on GCC_PLUGINS 380 help 381 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 382 basic blocks. It supports all gcc versions with plugin support (from 383 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 384 by Dmitry Vyukov <dvyukov@google.com>. 385 386config HAVE_CC_STACKPROTECTOR 387 bool 388 help 389 An arch should select this symbol if: 390 - its compiler supports the -fstack-protector option 391 - it has implemented a stack canary (e.g. __stack_chk_guard) 392 393config CC_STACKPROTECTOR 394 def_bool n 395 help 396 Set when a stack-protector mode is enabled, so that the build 397 can enable kernel-side support for the GCC feature. 398 399choice 400 prompt "Stack Protector buffer overflow detection" 401 depends on HAVE_CC_STACKPROTECTOR 402 default CC_STACKPROTECTOR_NONE 403 help 404 This option turns on the "stack-protector" GCC feature. This 405 feature puts, at the beginning of functions, a canary value on 406 the stack just before the return address, and validates 407 the value just before actually returning. Stack based buffer 408 overflows (that need to overwrite this return address) now also 409 overwrite the canary, which gets detected and the attack is then 410 neutralized via a kernel panic. 411 412config CC_STACKPROTECTOR_NONE 413 bool "None" 414 help 415 Disable "stack-protector" GCC feature. 416 417config CC_STACKPROTECTOR_REGULAR 418 bool "Regular" 419 select CC_STACKPROTECTOR 420 help 421 Functions will have the stack-protector canary logic added if they 422 have an 8-byte or larger character array on the stack. 423 424 This feature requires gcc version 4.2 or above, or a distribution 425 gcc with the feature backported ("-fstack-protector"). 426 427 On an x86 "defconfig" build, this feature adds canary checks to 428 about 3% of all kernel functions, which increases kernel code size 429 by about 0.3%. 430 431config CC_STACKPROTECTOR_STRONG 432 bool "Strong" 433 select CC_STACKPROTECTOR 434 help 435 Functions will have the stack-protector canary logic added in any 436 of the following conditions: 437 438 - local variable's address used as part of the right hand side of an 439 assignment or function argument 440 - local variable is an array (or union containing an array), 441 regardless of array type or length 442 - uses register local variables 443 444 This feature requires gcc version 4.9 or above, or a distribution 445 gcc with the feature backported ("-fstack-protector-strong"). 446 447 On an x86 "defconfig" build, this feature adds canary checks to 448 about 20% of all kernel functions, which increases the kernel code 449 size by about 2%. 450 451endchoice 452 453config HAVE_ARCH_WITHIN_STACK_FRAMES 454 bool 455 help 456 An architecture should select this if it can walk the kernel stack 457 frames to determine if an object is part of either the arguments 458 or local variables (i.e. that it excludes saved return addresses, 459 and similar) by implementing an inline arch_within_stack_frames(), 460 which is used by CONFIG_HARDENED_USERCOPY. 461 462config HAVE_CONTEXT_TRACKING 463 bool 464 help 465 Provide kernel/user boundaries probes necessary for subsystems 466 that need it, such as userspace RCU extended quiescent state. 467 Syscalls need to be wrapped inside user_exit()-user_enter() through 468 the slow path using TIF_NOHZ flag. Exceptions handlers must be 469 wrapped as well. Irqs are already protected inside 470 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 471 irq exit still need to be protected. 472 473config HAVE_VIRT_CPU_ACCOUNTING 474 bool 475 476config HAVE_VIRT_CPU_ACCOUNTING_GEN 477 bool 478 default y if 64BIT 479 help 480 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 481 Before enabling this option, arch code must be audited 482 to ensure there are no races in concurrent read/write of 483 cputime_t. For example, reading/writing 64-bit cputime_t on 484 some 32-bit arches may require multiple accesses, so proper 485 locking is needed to protect against concurrent accesses. 486 487 488config HAVE_IRQ_TIME_ACCOUNTING 489 bool 490 help 491 Archs need to ensure they use a high enough resolution clock to 492 support irq time accounting and then call enable_sched_clock_irqtime(). 493 494config HAVE_ARCH_TRANSPARENT_HUGEPAGE 495 bool 496 497config HAVE_ARCH_HUGE_VMAP 498 bool 499 500config HAVE_ARCH_SOFT_DIRTY 501 bool 502 503config HAVE_MOD_ARCH_SPECIFIC 504 bool 505 help 506 The arch uses struct mod_arch_specific to store data. Many arches 507 just need a simple module loader without arch specific data - those 508 should not enable this. 509 510config MODULES_USE_ELF_RELA 511 bool 512 help 513 Modules only use ELF RELA relocations. Modules with ELF REL 514 relocations will give an error. 515 516config MODULES_USE_ELF_REL 517 bool 518 help 519 Modules only use ELF REL relocations. Modules with ELF RELA 520 relocations will give an error. 521 522config HAVE_UNDERSCORE_SYMBOL_PREFIX 523 bool 524 help 525 Some architectures generate an _ in front of C symbols; things like 526 module loading and assembly files need to know about this. 527 528config HAVE_IRQ_EXIT_ON_IRQ_STACK 529 bool 530 help 531 Architecture doesn't only execute the irq handler on the irq stack 532 but also irq_exit(). This way we can process softirqs on this irq 533 stack instead of switching to a new one when we call __do_softirq() 534 in the end of an hardirq. 535 This spares a stack switch and improves cache usage on softirq 536 processing. 537 538config PGTABLE_LEVELS 539 int 540 default 2 541 542config ARCH_HAS_ELF_RANDOMIZE 543 bool 544 help 545 An architecture supports choosing randomized locations for 546 stack, mmap, brk, and ET_DYN. Defined functions: 547 - arch_mmap_rnd() 548 - arch_randomize_brk() 549 550config HAVE_ARCH_MMAP_RND_BITS 551 bool 552 help 553 An arch should select this symbol if it supports setting a variable 554 number of bits for use in establishing the base address for mmap 555 allocations, has MMU enabled and provides values for both: 556 - ARCH_MMAP_RND_BITS_MIN 557 - ARCH_MMAP_RND_BITS_MAX 558 559config HAVE_EXIT_THREAD 560 bool 561 help 562 An architecture implements exit_thread. 563 564config ARCH_MMAP_RND_BITS_MIN 565 int 566 567config ARCH_MMAP_RND_BITS_MAX 568 int 569 570config ARCH_MMAP_RND_BITS_DEFAULT 571 int 572 573config ARCH_MMAP_RND_BITS 574 int "Number of bits to use for ASLR of mmap base address" if EXPERT 575 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 576 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 577 default ARCH_MMAP_RND_BITS_MIN 578 depends on HAVE_ARCH_MMAP_RND_BITS 579 help 580 This value can be used to select the number of bits to use to 581 determine the random offset to the base address of vma regions 582 resulting from mmap allocations. This value will be bounded 583 by the architecture's minimum and maximum supported values. 584 585 This value can be changed after boot using the 586 /proc/sys/vm/mmap_rnd_bits tunable 587 588config HAVE_ARCH_MMAP_RND_COMPAT_BITS 589 bool 590 help 591 An arch should select this symbol if it supports running applications 592 in compatibility mode, supports setting a variable number of bits for 593 use in establishing the base address for mmap allocations, has MMU 594 enabled and provides values for both: 595 - ARCH_MMAP_RND_COMPAT_BITS_MIN 596 - ARCH_MMAP_RND_COMPAT_BITS_MAX 597 598config ARCH_MMAP_RND_COMPAT_BITS_MIN 599 int 600 601config ARCH_MMAP_RND_COMPAT_BITS_MAX 602 int 603 604config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 605 int 606 607config ARCH_MMAP_RND_COMPAT_BITS 608 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 609 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 610 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 611 default ARCH_MMAP_RND_COMPAT_BITS_MIN 612 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 613 help 614 This value can be used to select the number of bits to use to 615 determine the random offset to the base address of vma regions 616 resulting from mmap allocations for compatible applications This 617 value will be bounded by the architecture's minimum and maximum 618 supported values. 619 620 This value can be changed after boot using the 621 /proc/sys/vm/mmap_rnd_compat_bits tunable 622 623config HAVE_COPY_THREAD_TLS 624 bool 625 help 626 Architecture provides copy_thread_tls to accept tls argument via 627 normal C parameter passing, rather than extracting the syscall 628 argument from pt_regs. 629 630config HAVE_STACK_VALIDATION 631 bool 632 help 633 Architecture supports the 'objtool check' host tool command, which 634 performs compile-time stack metadata validation. 635 636config HAVE_ARCH_HASH 637 bool 638 default n 639 help 640 If this is set, the architecture provides an <asm/hash.h> 641 file which provides platform-specific implementations of some 642 functions in <linux/hash.h> or fs/namei.c. 643 644config ISA_BUS_API 645 def_bool ISA 646 647# 648# ABI hall of shame 649# 650config CLONE_BACKWARDS 651 bool 652 help 653 Architecture has tls passed as the 4th argument of clone(2), 654 not the 5th one. 655 656config CLONE_BACKWARDS2 657 bool 658 help 659 Architecture has the first two arguments of clone(2) swapped. 660 661config CLONE_BACKWARDS3 662 bool 663 help 664 Architecture has tls passed as the 3rd argument of clone(2), 665 not the 5th one. 666 667config ODD_RT_SIGACTION 668 bool 669 help 670 Architecture has unusual rt_sigaction(2) arguments 671 672config OLD_SIGSUSPEND 673 bool 674 help 675 Architecture has old sigsuspend(2) syscall, of one-argument variety 676 677config OLD_SIGSUSPEND3 678 bool 679 help 680 Even weirder antique ABI - three-argument sigsuspend(2) 681 682config OLD_SIGACTION 683 bool 684 help 685 Architecture has old sigaction(2) syscall. Nope, not the same 686 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 687 but fairly different variant of sigaction(2), thanks to OSF/1 688 compatibility... 689 690config COMPAT_OLD_SIGACTION 691 bool 692 693config ARCH_NO_COHERENT_DMA_MMAP 694 bool 695 696config CPU_NO_EFFICIENT_FFS 697 def_bool n 698 699source "kernel/gcov/Kconfig" 700