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_info() function 230config ARCH_THREAD_INFO_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 help 370 GCC plugins are loadable modules that provide extra features to the 371 compiler. They are useful for runtime instrumentation and static analysis. 372 373 See Documentation/gcc-plugins.txt for details. 374 375config HAVE_CC_STACKPROTECTOR 376 bool 377 help 378 An arch should select this symbol if: 379 - its compiler supports the -fstack-protector option 380 - it has implemented a stack canary (e.g. __stack_chk_guard) 381 382config CC_STACKPROTECTOR 383 def_bool n 384 help 385 Set when a stack-protector mode is enabled, so that the build 386 can enable kernel-side support for the GCC feature. 387 388choice 389 prompt "Stack Protector buffer overflow detection" 390 depends on HAVE_CC_STACKPROTECTOR 391 default CC_STACKPROTECTOR_NONE 392 help 393 This option turns on the "stack-protector" GCC feature. This 394 feature puts, at the beginning of functions, a canary value on 395 the stack just before the return address, and validates 396 the value just before actually returning. Stack based buffer 397 overflows (that need to overwrite this return address) now also 398 overwrite the canary, which gets detected and the attack is then 399 neutralized via a kernel panic. 400 401config CC_STACKPROTECTOR_NONE 402 bool "None" 403 help 404 Disable "stack-protector" GCC feature. 405 406config CC_STACKPROTECTOR_REGULAR 407 bool "Regular" 408 select CC_STACKPROTECTOR 409 help 410 Functions will have the stack-protector canary logic added if they 411 have an 8-byte or larger character array on the stack. 412 413 This feature requires gcc version 4.2 or above, or a distribution 414 gcc with the feature backported ("-fstack-protector"). 415 416 On an x86 "defconfig" build, this feature adds canary checks to 417 about 3% of all kernel functions, which increases kernel code size 418 by about 0.3%. 419 420config CC_STACKPROTECTOR_STRONG 421 bool "Strong" 422 select CC_STACKPROTECTOR 423 help 424 Functions will have the stack-protector canary logic added in any 425 of the following conditions: 426 427 - local variable's address used as part of the right hand side of an 428 assignment or function argument 429 - local variable is an array (or union containing an array), 430 regardless of array type or length 431 - uses register local variables 432 433 This feature requires gcc version 4.9 or above, or a distribution 434 gcc with the feature backported ("-fstack-protector-strong"). 435 436 On an x86 "defconfig" build, this feature adds canary checks to 437 about 20% of all kernel functions, which increases the kernel code 438 size by about 2%. 439 440endchoice 441 442config HAVE_CONTEXT_TRACKING 443 bool 444 help 445 Provide kernel/user boundaries probes necessary for subsystems 446 that need it, such as userspace RCU extended quiescent state. 447 Syscalls need to be wrapped inside user_exit()-user_enter() through 448 the slow path using TIF_NOHZ flag. Exceptions handlers must be 449 wrapped as well. Irqs are already protected inside 450 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 451 irq exit still need to be protected. 452 453config HAVE_VIRT_CPU_ACCOUNTING 454 bool 455 456config HAVE_VIRT_CPU_ACCOUNTING_GEN 457 bool 458 default y if 64BIT 459 help 460 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 461 Before enabling this option, arch code must be audited 462 to ensure there are no races in concurrent read/write of 463 cputime_t. For example, reading/writing 64-bit cputime_t on 464 some 32-bit arches may require multiple accesses, so proper 465 locking is needed to protect against concurrent accesses. 466 467 468config HAVE_IRQ_TIME_ACCOUNTING 469 bool 470 help 471 Archs need to ensure they use a high enough resolution clock to 472 support irq time accounting and then call enable_sched_clock_irqtime(). 473 474config HAVE_ARCH_TRANSPARENT_HUGEPAGE 475 bool 476 477config HAVE_ARCH_HUGE_VMAP 478 bool 479 480config HAVE_ARCH_SOFT_DIRTY 481 bool 482 483config HAVE_MOD_ARCH_SPECIFIC 484 bool 485 help 486 The arch uses struct mod_arch_specific to store data. Many arches 487 just need a simple module loader without arch specific data - those 488 should not enable this. 489 490config MODULES_USE_ELF_RELA 491 bool 492 help 493 Modules only use ELF RELA relocations. Modules with ELF REL 494 relocations will give an error. 495 496config MODULES_USE_ELF_REL 497 bool 498 help 499 Modules only use ELF REL relocations. Modules with ELF RELA 500 relocations will give an error. 501 502config HAVE_UNDERSCORE_SYMBOL_PREFIX 503 bool 504 help 505 Some architectures generate an _ in front of C symbols; things like 506 module loading and assembly files need to know about this. 507 508config HAVE_IRQ_EXIT_ON_IRQ_STACK 509 bool 510 help 511 Architecture doesn't only execute the irq handler on the irq stack 512 but also irq_exit(). This way we can process softirqs on this irq 513 stack instead of switching to a new one when we call __do_softirq() 514 in the end of an hardirq. 515 This spares a stack switch and improves cache usage on softirq 516 processing. 517 518config PGTABLE_LEVELS 519 int 520 default 2 521 522config ARCH_HAS_ELF_RANDOMIZE 523 bool 524 help 525 An architecture supports choosing randomized locations for 526 stack, mmap, brk, and ET_DYN. Defined functions: 527 - arch_mmap_rnd() 528 - arch_randomize_brk() 529 530config HAVE_ARCH_MMAP_RND_BITS 531 bool 532 help 533 An arch should select this symbol if it supports setting a variable 534 number of bits for use in establishing the base address for mmap 535 allocations, has MMU enabled and provides values for both: 536 - ARCH_MMAP_RND_BITS_MIN 537 - ARCH_MMAP_RND_BITS_MAX 538 539config HAVE_EXIT_THREAD 540 bool 541 help 542 An architecture implements exit_thread. 543 544config ARCH_MMAP_RND_BITS_MIN 545 int 546 547config ARCH_MMAP_RND_BITS_MAX 548 int 549 550config ARCH_MMAP_RND_BITS_DEFAULT 551 int 552 553config ARCH_MMAP_RND_BITS 554 int "Number of bits to use for ASLR of mmap base address" if EXPERT 555 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 556 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 557 default ARCH_MMAP_RND_BITS_MIN 558 depends on HAVE_ARCH_MMAP_RND_BITS 559 help 560 This value can be used to select the number of bits to use to 561 determine the random offset to the base address of vma regions 562 resulting from mmap allocations. This value will be bounded 563 by the architecture's minimum and maximum supported values. 564 565 This value can be changed after boot using the 566 /proc/sys/vm/mmap_rnd_bits tunable 567 568config HAVE_ARCH_MMAP_RND_COMPAT_BITS 569 bool 570 help 571 An arch should select this symbol if it supports running applications 572 in compatibility mode, supports setting a variable number of bits for 573 use in establishing the base address for mmap allocations, has MMU 574 enabled and provides values for both: 575 - ARCH_MMAP_RND_COMPAT_BITS_MIN 576 - ARCH_MMAP_RND_COMPAT_BITS_MAX 577 578config ARCH_MMAP_RND_COMPAT_BITS_MIN 579 int 580 581config ARCH_MMAP_RND_COMPAT_BITS_MAX 582 int 583 584config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 585 int 586 587config ARCH_MMAP_RND_COMPAT_BITS 588 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 589 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 590 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 591 default ARCH_MMAP_RND_COMPAT_BITS_MIN 592 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 593 help 594 This value can be used to select the number of bits to use to 595 determine the random offset to the base address of vma regions 596 resulting from mmap allocations for compatible applications This 597 value will be bounded by the architecture's minimum and maximum 598 supported values. 599 600 This value can be changed after boot using the 601 /proc/sys/vm/mmap_rnd_compat_bits tunable 602 603config HAVE_COPY_THREAD_TLS 604 bool 605 help 606 Architecture provides copy_thread_tls to accept tls argument via 607 normal C parameter passing, rather than extracting the syscall 608 argument from pt_regs. 609 610config HAVE_STACK_VALIDATION 611 bool 612 help 613 Architecture supports the 'objtool check' host tool command, which 614 performs compile-time stack metadata validation. 615 616config HAVE_ARCH_HASH 617 bool 618 default n 619 help 620 If this is set, the architecture provides an <asm/hash.h> 621 file which provides platform-specific implementations of some 622 functions in <linux/hash.h> or fs/namei.c. 623 624# 625# ABI hall of shame 626# 627config CLONE_BACKWARDS 628 bool 629 help 630 Architecture has tls passed as the 4th argument of clone(2), 631 not the 5th one. 632 633config CLONE_BACKWARDS2 634 bool 635 help 636 Architecture has the first two arguments of clone(2) swapped. 637 638config CLONE_BACKWARDS3 639 bool 640 help 641 Architecture has tls passed as the 3rd argument of clone(2), 642 not the 5th one. 643 644config ODD_RT_SIGACTION 645 bool 646 help 647 Architecture has unusual rt_sigaction(2) arguments 648 649config OLD_SIGSUSPEND 650 bool 651 help 652 Architecture has old sigsuspend(2) syscall, of one-argument variety 653 654config OLD_SIGSUSPEND3 655 bool 656 help 657 Even weirder antique ABI - three-argument sigsuspend(2) 658 659config OLD_SIGACTION 660 bool 661 help 662 Architecture has old sigaction(2) syscall. Nope, not the same 663 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 664 but fairly different variant of sigaction(2), thanks to OSF/1 665 compatibility... 666 667config COMPAT_OLD_SIGACTION 668 bool 669 670config ARCH_NO_COHERENT_DMA_MMAP 671 bool 672 673config CPU_NO_EFFICIENT_FFS 674 def_bool n 675 676source "kernel/gcov/Kconfig" 677