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_WATCHDOG 191 bool 192# 193# An arch should select this if it provides all these things: 194# 195# task_pt_regs() in asm/processor.h or asm/ptrace.h 196# arch_has_single_step() if there is hardware single-step support 197# arch_has_block_step() if there is hardware block-step support 198# asm/syscall.h supplying asm-generic/syscall.h interface 199# linux/regset.h user_regset interfaces 200# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 201# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 202# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 203# signal delivery calls tracehook_signal_handler() 204# 205config HAVE_ARCH_TRACEHOOK 206 bool 207 208config HAVE_DMA_ATTRS 209 bool 210 211config HAVE_DMA_CONTIGUOUS 212 bool 213 214config GENERIC_SMP_IDLE_THREAD 215 bool 216 217config GENERIC_IDLE_POLL_SETUP 218 bool 219 220# Select if arch init_task initializer is different to init/init_task.c 221config ARCH_INIT_TASK 222 bool 223 224# Select if arch has its private alloc_task_struct() function 225config ARCH_TASK_STRUCT_ALLOCATOR 226 bool 227 228# Select if arch has its private alloc_thread_info() function 229config ARCH_THREAD_INFO_ALLOCATOR 230 bool 231 232# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 233config ARCH_WANTS_DYNAMIC_TASK_STRUCT 234 bool 235 236config HAVE_REGS_AND_STACK_ACCESS_API 237 bool 238 help 239 This symbol should be selected by an architecure if it supports 240 the API needed to access registers and stack entries from pt_regs, 241 declared in asm/ptrace.h 242 For example the kprobes-based event tracer needs this API. 243 244config HAVE_CLK 245 bool 246 help 247 The <linux/clk.h> calls support software clock gating and 248 thus are a key power management tool on many systems. 249 250config HAVE_DMA_API_DEBUG 251 bool 252 253config HAVE_HW_BREAKPOINT 254 bool 255 depends on PERF_EVENTS 256 257config HAVE_MIXED_BREAKPOINTS_REGS 258 bool 259 depends on HAVE_HW_BREAKPOINT 260 help 261 Depending on the arch implementation of hardware breakpoints, 262 some of them have separate registers for data and instruction 263 breakpoints addresses, others have mixed registers to store 264 them but define the access type in a control register. 265 Select this option if your arch implements breakpoints under the 266 latter fashion. 267 268config HAVE_USER_RETURN_NOTIFIER 269 bool 270 271config HAVE_PERF_EVENTS_NMI 272 bool 273 help 274 System hardware can generate an NMI using the perf event 275 subsystem. Also has support for calculating CPU cycle events 276 to determine how many clock cycles in a given period. 277 278config HAVE_PERF_REGS 279 bool 280 help 281 Support selective register dumps for perf events. This includes 282 bit-mapping of each registers and a unique architecture id. 283 284config HAVE_PERF_USER_STACK_DUMP 285 bool 286 help 287 Support user stack dumps for perf event samples. This needs 288 access to the user stack pointer which is not unified across 289 architectures. 290 291config HAVE_ARCH_JUMP_LABEL 292 bool 293 294config HAVE_RCU_TABLE_FREE 295 bool 296 297config ARCH_HAVE_NMI_SAFE_CMPXCHG 298 bool 299 300config HAVE_ALIGNED_STRUCT_PAGE 301 bool 302 help 303 This makes sure that struct pages are double word aligned and that 304 e.g. the SLUB allocator can perform double word atomic operations 305 on a struct page for better performance. However selecting this 306 might increase the size of a struct page by a word. 307 308config HAVE_CMPXCHG_LOCAL 309 bool 310 311config HAVE_CMPXCHG_DOUBLE 312 bool 313 314config ARCH_WANT_IPC_PARSE_VERSION 315 bool 316 317config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 318 bool 319 320config ARCH_WANT_OLD_COMPAT_IPC 321 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 322 bool 323 324config HAVE_ARCH_SECCOMP_FILTER 325 bool 326 help 327 An arch should select this symbol if it provides all of these things: 328 - syscall_get_arch() 329 - syscall_get_arguments() 330 - syscall_rollback() 331 - syscall_set_return_value() 332 - SIGSYS siginfo_t support 333 - secure_computing is called from a ptrace_event()-safe context 334 - secure_computing return value is checked and a return value of -1 335 results in the system call being skipped immediately. 336 - seccomp syscall wired up 337 338 For best performance, an arch should use seccomp_phase1 and 339 seccomp_phase2 directly. It should call seccomp_phase1 for all 340 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not 341 need to be called from a ptrace-safe context. It must then 342 call seccomp_phase2 if seccomp_phase1 returns anything other 343 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP. 344 345 As an additional optimization, an arch may provide seccomp_data 346 directly to seccomp_phase1; this avoids multiple calls 347 to the syscall_xyz helpers for every syscall. 348 349config SECCOMP_FILTER 350 def_bool y 351 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 352 help 353 Enable tasks to build secure computing environments defined 354 in terms of Berkeley Packet Filter programs which implement 355 task-defined system call filtering polices. 356 357 See Documentation/prctl/seccomp_filter.txt for details. 358 359config HAVE_CC_STACKPROTECTOR 360 bool 361 help 362 An arch should select this symbol if: 363 - its compiler supports the -fstack-protector option 364 - it has implemented a stack canary (e.g. __stack_chk_guard) 365 366config CC_STACKPROTECTOR 367 def_bool n 368 help 369 Set when a stack-protector mode is enabled, so that the build 370 can enable kernel-side support for the GCC feature. 371 372choice 373 prompt "Stack Protector buffer overflow detection" 374 depends on HAVE_CC_STACKPROTECTOR 375 default CC_STACKPROTECTOR_NONE 376 help 377 This option turns on the "stack-protector" GCC feature. This 378 feature puts, at the beginning of functions, a canary value on 379 the stack just before the return address, and validates 380 the value just before actually returning. Stack based buffer 381 overflows (that need to overwrite this return address) now also 382 overwrite the canary, which gets detected and the attack is then 383 neutralized via a kernel panic. 384 385config CC_STACKPROTECTOR_NONE 386 bool "None" 387 help 388 Disable "stack-protector" GCC feature. 389 390config CC_STACKPROTECTOR_REGULAR 391 bool "Regular" 392 select CC_STACKPROTECTOR 393 help 394 Functions will have the stack-protector canary logic added if they 395 have an 8-byte or larger character array on the stack. 396 397 This feature requires gcc version 4.2 or above, or a distribution 398 gcc with the feature backported ("-fstack-protector"). 399 400 On an x86 "defconfig" build, this feature adds canary checks to 401 about 3% of all kernel functions, which increases kernel code size 402 by about 0.3%. 403 404config CC_STACKPROTECTOR_STRONG 405 bool "Strong" 406 select CC_STACKPROTECTOR 407 help 408 Functions will have the stack-protector canary logic added in any 409 of the following conditions: 410 411 - local variable's address used as part of the right hand side of an 412 assignment or function argument 413 - local variable is an array (or union containing an array), 414 regardless of array type or length 415 - uses register local variables 416 417 This feature requires gcc version 4.9 or above, or a distribution 418 gcc with the feature backported ("-fstack-protector-strong"). 419 420 On an x86 "defconfig" build, this feature adds canary checks to 421 about 20% of all kernel functions, which increases the kernel code 422 size by about 2%. 423 424endchoice 425 426config HAVE_CONTEXT_TRACKING 427 bool 428 help 429 Provide kernel/user boundaries probes necessary for subsystems 430 that need it, such as userspace RCU extended quiescent state. 431 Syscalls need to be wrapped inside user_exit()-user_enter() through 432 the slow path using TIF_NOHZ flag. Exceptions handlers must be 433 wrapped as well. Irqs are already protected inside 434 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 435 irq exit still need to be protected. 436 437config HAVE_VIRT_CPU_ACCOUNTING 438 bool 439 440config HAVE_VIRT_CPU_ACCOUNTING_GEN 441 bool 442 default y if 64BIT 443 help 444 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 445 Before enabling this option, arch code must be audited 446 to ensure there are no races in concurrent read/write of 447 cputime_t. For example, reading/writing 64-bit cputime_t on 448 some 32-bit arches may require multiple accesses, so proper 449 locking is needed to protect against concurrent accesses. 450 451 452config HAVE_IRQ_TIME_ACCOUNTING 453 bool 454 help 455 Archs need to ensure they use a high enough resolution clock to 456 support irq time accounting and then call enable_sched_clock_irqtime(). 457 458config HAVE_ARCH_TRANSPARENT_HUGEPAGE 459 bool 460 461config HAVE_ARCH_HUGE_VMAP 462 bool 463 464config HAVE_ARCH_SOFT_DIRTY 465 bool 466 467config HAVE_MOD_ARCH_SPECIFIC 468 bool 469 help 470 The arch uses struct mod_arch_specific to store data. Many arches 471 just need a simple module loader without arch specific data - those 472 should not enable this. 473 474config MODULES_USE_ELF_RELA 475 bool 476 help 477 Modules only use ELF RELA relocations. Modules with ELF REL 478 relocations will give an error. 479 480config MODULES_USE_ELF_REL 481 bool 482 help 483 Modules only use ELF REL relocations. Modules with ELF RELA 484 relocations will give an error. 485 486config HAVE_UNDERSCORE_SYMBOL_PREFIX 487 bool 488 help 489 Some architectures generate an _ in front of C symbols; things like 490 module loading and assembly files need to know about this. 491 492config HAVE_IRQ_EXIT_ON_IRQ_STACK 493 bool 494 help 495 Architecture doesn't only execute the irq handler on the irq stack 496 but also irq_exit(). This way we can process softirqs on this irq 497 stack instead of switching to a new one when we call __do_softirq() 498 in the end of an hardirq. 499 This spares a stack switch and improves cache usage on softirq 500 processing. 501 502config PGTABLE_LEVELS 503 int 504 default 2 505 506config ARCH_HAS_ELF_RANDOMIZE 507 bool 508 help 509 An architecture supports choosing randomized locations for 510 stack, mmap, brk, and ET_DYN. Defined functions: 511 - arch_mmap_rnd() 512 - arch_randomize_brk() 513 514config HAVE_COPY_THREAD_TLS 515 bool 516 help 517 Architecture provides copy_thread_tls to accept tls argument via 518 normal C parameter passing, rather than extracting the syscall 519 argument from pt_regs. 520 521# 522# ABI hall of shame 523# 524config CLONE_BACKWARDS 525 bool 526 help 527 Architecture has tls passed as the 4th argument of clone(2), 528 not the 5th one. 529 530config CLONE_BACKWARDS2 531 bool 532 help 533 Architecture has the first two arguments of clone(2) swapped. 534 535config CLONE_BACKWARDS3 536 bool 537 help 538 Architecture has tls passed as the 3rd argument of clone(2), 539 not the 5th one. 540 541config ODD_RT_SIGACTION 542 bool 543 help 544 Architecture has unusual rt_sigaction(2) arguments 545 546config OLD_SIGSUSPEND 547 bool 548 help 549 Architecture has old sigsuspend(2) syscall, of one-argument variety 550 551config OLD_SIGSUSPEND3 552 bool 553 help 554 Even weirder antique ABI - three-argument sigsuspend(2) 555 556config OLD_SIGACTION 557 bool 558 help 559 Architecture has old sigaction(2) syscall. Nope, not the same 560 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 561 but fairly different variant of sigaction(2), thanks to OSF/1 562 compatibility... 563 564config COMPAT_OLD_SIGACTION 565 bool 566 567source "kernel/gcov/Kconfig" 568