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