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