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 338 339 For best performance, an arch should use seccomp_phase1 and 340 seccomp_phase2 directly. It should call seccomp_phase1 for all 341 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not 342 need to be called from a ptrace-safe context. It must then 343 call seccomp_phase2 if seccomp_phase1 returns anything other 344 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP. 345 346 As an additional optimization, an arch may provide seccomp_data 347 directly to seccomp_phase1; this avoids multiple calls 348 to the syscall_xyz helpers for every syscall. 349 350config SECCOMP_FILTER 351 def_bool y 352 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 353 help 354 Enable tasks to build secure computing environments defined 355 in terms of Berkeley Packet Filter programs which implement 356 task-defined system call filtering polices. 357 358 See Documentation/prctl/seccomp_filter.txt for details. 359 360config HAVE_GCC_PLUGINS 361 bool 362 help 363 An arch should select this symbol if it supports building with 364 GCC plugins. 365 366menuconfig GCC_PLUGINS 367 bool "GCC plugins" 368 depends on HAVE_GCC_PLUGINS 369 depends on !COMPILE_TEST 370 help 371 GCC plugins are loadable modules that provide extra features to the 372 compiler. They are useful for runtime instrumentation and static analysis. 373 374 See Documentation/gcc-plugins.txt for details. 375 376config GCC_PLUGIN_CYC_COMPLEXITY 377 bool "Compute the cyclomatic complexity of a function" 378 depends on GCC_PLUGINS 379 help 380 The complexity M of a function's control flow graph is defined as: 381 M = E - N + 2P 382 where 383 384 E = the number of edges 385 N = the number of nodes 386 P = the number of connected components (exit nodes). 387 388config GCC_PLUGIN_SANCOV 389 bool 390 depends on GCC_PLUGINS 391 help 392 This plugin inserts a __sanitizer_cov_trace_pc() call at the start of 393 basic blocks. It supports all gcc versions with plugin support (from 394 gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" 395 by Dmitry Vyukov <dvyukov@google.com>. 396 397config HAVE_CC_STACKPROTECTOR 398 bool 399 help 400 An arch should select this symbol if: 401 - its compiler supports the -fstack-protector option 402 - it has implemented a stack canary (e.g. __stack_chk_guard) 403 404config CC_STACKPROTECTOR 405 def_bool n 406 help 407 Set when a stack-protector mode is enabled, so that the build 408 can enable kernel-side support for the GCC feature. 409 410choice 411 prompt "Stack Protector buffer overflow detection" 412 depends on HAVE_CC_STACKPROTECTOR 413 default CC_STACKPROTECTOR_NONE 414 help 415 This option turns on the "stack-protector" GCC feature. This 416 feature puts, at the beginning of functions, a canary value on 417 the stack just before the return address, and validates 418 the value just before actually returning. Stack based buffer 419 overflows (that need to overwrite this return address) now also 420 overwrite the canary, which gets detected and the attack is then 421 neutralized via a kernel panic. 422 423config CC_STACKPROTECTOR_NONE 424 bool "None" 425 help 426 Disable "stack-protector" GCC feature. 427 428config CC_STACKPROTECTOR_REGULAR 429 bool "Regular" 430 select CC_STACKPROTECTOR 431 help 432 Functions will have the stack-protector canary logic added if they 433 have an 8-byte or larger character array on the stack. 434 435 This feature requires gcc version 4.2 or above, or a distribution 436 gcc with the feature backported ("-fstack-protector"). 437 438 On an x86 "defconfig" build, this feature adds canary checks to 439 about 3% of all kernel functions, which increases kernel code size 440 by about 0.3%. 441 442config CC_STACKPROTECTOR_STRONG 443 bool "Strong" 444 select CC_STACKPROTECTOR 445 help 446 Functions will have the stack-protector canary logic added in any 447 of the following conditions: 448 449 - local variable's address used as part of the right hand side of an 450 assignment or function argument 451 - local variable is an array (or union containing an array), 452 regardless of array type or length 453 - uses register local variables 454 455 This feature requires gcc version 4.9 or above, or a distribution 456 gcc with the feature backported ("-fstack-protector-strong"). 457 458 On an x86 "defconfig" build, this feature adds canary checks to 459 about 20% of all kernel functions, which increases the kernel code 460 size by about 2%. 461 462endchoice 463 464config HAVE_CONTEXT_TRACKING 465 bool 466 help 467 Provide kernel/user boundaries probes necessary for subsystems 468 that need it, such as userspace RCU extended quiescent state. 469 Syscalls need to be wrapped inside user_exit()-user_enter() through 470 the slow path using TIF_NOHZ flag. Exceptions handlers must be 471 wrapped as well. Irqs are already protected inside 472 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 473 irq exit still need to be protected. 474 475config HAVE_VIRT_CPU_ACCOUNTING 476 bool 477 478config HAVE_VIRT_CPU_ACCOUNTING_GEN 479 bool 480 default y if 64BIT 481 help 482 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 483 Before enabling this option, arch code must be audited 484 to ensure there are no races in concurrent read/write of 485 cputime_t. For example, reading/writing 64-bit cputime_t on 486 some 32-bit arches may require multiple accesses, so proper 487 locking is needed to protect against concurrent accesses. 488 489 490config HAVE_IRQ_TIME_ACCOUNTING 491 bool 492 help 493 Archs need to ensure they use a high enough resolution clock to 494 support irq time accounting and then call enable_sched_clock_irqtime(). 495 496config HAVE_ARCH_TRANSPARENT_HUGEPAGE 497 bool 498 499config HAVE_ARCH_HUGE_VMAP 500 bool 501 502config HAVE_ARCH_SOFT_DIRTY 503 bool 504 505config HAVE_MOD_ARCH_SPECIFIC 506 bool 507 help 508 The arch uses struct mod_arch_specific to store data. Many arches 509 just need a simple module loader without arch specific data - those 510 should not enable this. 511 512config MODULES_USE_ELF_RELA 513 bool 514 help 515 Modules only use ELF RELA relocations. Modules with ELF REL 516 relocations will give an error. 517 518config MODULES_USE_ELF_REL 519 bool 520 help 521 Modules only use ELF REL relocations. Modules with ELF RELA 522 relocations will give an error. 523 524config HAVE_UNDERSCORE_SYMBOL_PREFIX 525 bool 526 help 527 Some architectures generate an _ in front of C symbols; things like 528 module loading and assembly files need to know about this. 529 530config HAVE_IRQ_EXIT_ON_IRQ_STACK 531 bool 532 help 533 Architecture doesn't only execute the irq handler on the irq stack 534 but also irq_exit(). This way we can process softirqs on this irq 535 stack instead of switching to a new one when we call __do_softirq() 536 in the end of an hardirq. 537 This spares a stack switch and improves cache usage on softirq 538 processing. 539 540config PGTABLE_LEVELS 541 int 542 default 2 543 544config ARCH_HAS_ELF_RANDOMIZE 545 bool 546 help 547 An architecture supports choosing randomized locations for 548 stack, mmap, brk, and ET_DYN. Defined functions: 549 - arch_mmap_rnd() 550 - arch_randomize_brk() 551 552config HAVE_ARCH_MMAP_RND_BITS 553 bool 554 help 555 An arch should select this symbol if it supports setting a variable 556 number of bits for use in establishing the base address for mmap 557 allocations, has MMU enabled and provides values for both: 558 - ARCH_MMAP_RND_BITS_MIN 559 - ARCH_MMAP_RND_BITS_MAX 560 561config HAVE_EXIT_THREAD 562 bool 563 help 564 An architecture implements exit_thread. 565 566config ARCH_MMAP_RND_BITS_MIN 567 int 568 569config ARCH_MMAP_RND_BITS_MAX 570 int 571 572config ARCH_MMAP_RND_BITS_DEFAULT 573 int 574 575config ARCH_MMAP_RND_BITS 576 int "Number of bits to use for ASLR of mmap base address" if EXPERT 577 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 578 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 579 default ARCH_MMAP_RND_BITS_MIN 580 depends on HAVE_ARCH_MMAP_RND_BITS 581 help 582 This value can be used to select the number of bits to use to 583 determine the random offset to the base address of vma regions 584 resulting from mmap allocations. This value will be bounded 585 by the architecture's minimum and maximum supported values. 586 587 This value can be changed after boot using the 588 /proc/sys/vm/mmap_rnd_bits tunable 589 590config HAVE_ARCH_MMAP_RND_COMPAT_BITS 591 bool 592 help 593 An arch should select this symbol if it supports running applications 594 in compatibility mode, supports setting a variable number of bits for 595 use in establishing the base address for mmap allocations, has MMU 596 enabled and provides values for both: 597 - ARCH_MMAP_RND_COMPAT_BITS_MIN 598 - ARCH_MMAP_RND_COMPAT_BITS_MAX 599 600config ARCH_MMAP_RND_COMPAT_BITS_MIN 601 int 602 603config ARCH_MMAP_RND_COMPAT_BITS_MAX 604 int 605 606config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 607 int 608 609config ARCH_MMAP_RND_COMPAT_BITS 610 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 611 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 612 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 613 default ARCH_MMAP_RND_COMPAT_BITS_MIN 614 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 615 help 616 This value can be used to select the number of bits to use to 617 determine the random offset to the base address of vma regions 618 resulting from mmap allocations for compatible applications This 619 value will be bounded by the architecture's minimum and maximum 620 supported values. 621 622 This value can be changed after boot using the 623 /proc/sys/vm/mmap_rnd_compat_bits tunable 624 625config HAVE_COPY_THREAD_TLS 626 bool 627 help 628 Architecture provides copy_thread_tls to accept tls argument via 629 normal C parameter passing, rather than extracting the syscall 630 argument from pt_regs. 631 632config HAVE_STACK_VALIDATION 633 bool 634 help 635 Architecture supports the 'objtool check' host tool command, which 636 performs compile-time stack metadata validation. 637 638config HAVE_ARCH_HASH 639 bool 640 default n 641 help 642 If this is set, the architecture provides an <asm/hash.h> 643 file which provides platform-specific implementations of some 644 functions in <linux/hash.h> or fs/namei.c. 645 646config ISA_BUS_API 647 def_bool ISA 648 649# 650# ABI hall of shame 651# 652config CLONE_BACKWARDS 653 bool 654 help 655 Architecture has tls passed as the 4th argument of clone(2), 656 not the 5th one. 657 658config CLONE_BACKWARDS2 659 bool 660 help 661 Architecture has the first two arguments of clone(2) swapped. 662 663config CLONE_BACKWARDS3 664 bool 665 help 666 Architecture has tls passed as the 3rd argument of clone(2), 667 not the 5th one. 668 669config ODD_RT_SIGACTION 670 bool 671 help 672 Architecture has unusual rt_sigaction(2) arguments 673 674config OLD_SIGSUSPEND 675 bool 676 help 677 Architecture has old sigsuspend(2) syscall, of one-argument variety 678 679config OLD_SIGSUSPEND3 680 bool 681 help 682 Even weirder antique ABI - three-argument sigsuspend(2) 683 684config OLD_SIGACTION 685 bool 686 help 687 Architecture has old sigaction(2) syscall. Nope, not the same 688 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 689 but fairly different variant of sigaction(2), thanks to OSF/1 690 compatibility... 691 692config COMPAT_OLD_SIGACTION 693 bool 694 695config ARCH_NO_COHERENT_DMA_MMAP 696 bool 697 698config CPU_NO_EFFICIENT_FFS 699 def_bool n 700 701source "kernel/gcov/Kconfig" 702