1# 2# General architecture dependent options 3# 4 5config OPROFILE 6 tristate "OProfile system profiling" 7 depends on PROFILING 8 depends on HAVE_OPROFILE 9 select RING_BUFFER 10 select RING_BUFFER_ALLOW_SWAP 11 help 12 OProfile is a profiling system capable of profiling the 13 whole system, include the kernel, kernel modules, libraries, 14 and applications. 15 16 If unsure, say N. 17 18config OPROFILE_EVENT_MULTIPLEX 19 bool "OProfile multiplexing support (EXPERIMENTAL)" 20 default n 21 depends on OPROFILE && X86 22 help 23 The number of hardware counters is limited. The multiplexing 24 feature enables OProfile to gather more events than counters 25 are provided by the hardware. This is realized by switching 26 between events at an user specified time interval. 27 28 If unsure, say N. 29 30config HAVE_OPROFILE 31 bool 32 33config OPROFILE_NMI_TIMER 34 def_bool y 35 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 36 37config KPROBES 38 bool "Kprobes" 39 depends on MODULES 40 depends on HAVE_KPROBES 41 select KALLSYMS 42 help 43 Kprobes allows you to trap at almost any kernel address and 44 execute a callback function. register_kprobe() establishes 45 a probepoint and specifies the callback. Kprobes is useful 46 for kernel debugging, non-intrusive instrumentation and testing. 47 If in doubt, say "N". 48 49config JUMP_LABEL 50 bool "Optimize very unlikely/likely branches" 51 depends on HAVE_ARCH_JUMP_LABEL 52 help 53 This option enables a transparent branch optimization that 54 makes certain almost-always-true or almost-always-false branch 55 conditions even cheaper to execute within the kernel. 56 57 Certain performance-sensitive kernel code, such as trace points, 58 scheduler functionality, networking code and KVM have such 59 branches and include support for this optimization technique. 60 61 If it is detected that the compiler has support for "asm goto", 62 the kernel will compile such branches with just a nop 63 instruction. When the condition flag is toggled to true, the 64 nop will be converted to a jump instruction to execute the 65 conditional block of instructions. 66 67 This technique lowers overhead and stress on the branch prediction 68 of the processor and generally makes the kernel faster. The update 69 of the condition is slower, but those are always very rare. 70 71 ( On 32-bit x86, the necessary options added to the compiler 72 flags may increase the size of the kernel slightly. ) 73 74config OPTPROBES 75 def_bool y 76 depends on KPROBES && HAVE_OPTPROBES 77 depends on !PREEMPT 78 79config KPROBES_ON_FTRACE 80 def_bool y 81 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 82 depends on DYNAMIC_FTRACE_WITH_REGS 83 help 84 If function tracer is enabled and the arch supports full 85 passing of pt_regs to function tracing, then kprobes can 86 optimize on top of function tracing. 87 88config UPROBES 89 bool "Transparent user-space probes (EXPERIMENTAL)" 90 depends on UPROBE_EVENT && PERF_EVENTS 91 default n 92 select PERCPU_RWSEM 93 help 94 Uprobes is the user-space counterpart to kprobes: they 95 enable instrumentation applications (such as 'perf probe') 96 to establish unintrusive probes in user-space binaries and 97 libraries, by executing handler functions when the probes 98 are hit by user-space applications. 99 100 ( These probes come in the form of single-byte breakpoints, 101 managed by the kernel and kept transparent to the probed 102 application. ) 103 104 If in doubt, say "N". 105 106config HAVE_64BIT_ALIGNED_ACCESS 107 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 108 help 109 Some architectures require 64 bit accesses to be 64 bit 110 aligned, which also requires structs containing 64 bit values 111 to be 64 bit aligned too. This includes some 32 bit 112 architectures which can do 64 bit accesses, as well as 64 bit 113 architectures without unaligned access. 114 115 This symbol should be selected by an architecture if 64 bit 116 accesses are required to be 64 bit aligned in this way even 117 though it is not a 64 bit architecture. 118 119 See Documentation/unaligned-memory-access.txt for more 120 information on the topic of unaligned memory accesses. 121 122config HAVE_EFFICIENT_UNALIGNED_ACCESS 123 bool 124 help 125 Some architectures are unable to perform unaligned accesses 126 without the use of get_unaligned/put_unaligned. Others are 127 unable to perform such accesses efficiently (e.g. trap on 128 unaligned access and require fixing it up in the exception 129 handler.) 130 131 This symbol should be selected by an architecture if it can 132 perform unaligned accesses efficiently to allow different 133 code paths to be selected for these cases. Some network 134 drivers, for example, could opt to not fix up alignment 135 problems with received packets if doing so would not help 136 much. 137 138 See Documentation/unaligned-memory-access.txt for more 139 information on the topic of unaligned memory accesses. 140 141config ARCH_USE_BUILTIN_BSWAP 142 bool 143 help 144 Modern versions of GCC (since 4.4) have builtin functions 145 for handling byte-swapping. Using these, instead of the old 146 inline assembler that the architecture code provides in the 147 __arch_bswapXX() macros, allows the compiler to see what's 148 happening and offers more opportunity for optimisation. In 149 particular, the compiler will be able to combine the byteswap 150 with a nearby load or store and use load-and-swap or 151 store-and-swap instructions if the architecture has them. It 152 should almost *never* result in code which is worse than the 153 hand-coded assembler in <asm/swab.h>. But just in case it 154 does, the use of the builtins is optional. 155 156 Any architecture with load-and-swap or store-and-swap 157 instructions should set this. And it shouldn't hurt to set it 158 on architectures that don't have such instructions. 159 160config KRETPROBES 161 def_bool y 162 depends on KPROBES && HAVE_KRETPROBES 163 164config USER_RETURN_NOTIFIER 165 bool 166 depends on HAVE_USER_RETURN_NOTIFIER 167 help 168 Provide a kernel-internal notification when a cpu is about to 169 switch to user mode. 170 171config HAVE_IOREMAP_PROT 172 bool 173 174config HAVE_KPROBES 175 bool 176 177config HAVE_KRETPROBES 178 bool 179 180config HAVE_OPTPROBES 181 bool 182 183config HAVE_KPROBES_ON_FTRACE 184 bool 185 186config HAVE_NMI_WATCHDOG 187 bool 188# 189# An arch should select this if it provides all these things: 190# 191# task_pt_regs() in asm/processor.h or asm/ptrace.h 192# arch_has_single_step() if there is hardware single-step support 193# arch_has_block_step() if there is hardware block-step support 194# asm/syscall.h supplying asm-generic/syscall.h interface 195# linux/regset.h user_regset interfaces 196# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 197# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 198# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 199# signal delivery calls tracehook_signal_handler() 200# 201config HAVE_ARCH_TRACEHOOK 202 bool 203 204config HAVE_DMA_ATTRS 205 bool 206 207config HAVE_DMA_CONTIGUOUS 208 bool 209 210config GENERIC_SMP_IDLE_THREAD 211 bool 212 213config GENERIC_IDLE_POLL_SETUP 214 bool 215 216# Select if arch init_task initializer is different to init/init_task.c 217config ARCH_INIT_TASK 218 bool 219 220# Select if arch has its private alloc_task_struct() function 221config ARCH_TASK_STRUCT_ALLOCATOR 222 bool 223 224# Select if arch has its private alloc_thread_info() function 225config ARCH_THREAD_INFO_ALLOCATOR 226 bool 227 228config HAVE_REGS_AND_STACK_ACCESS_API 229 bool 230 help 231 This symbol should be selected by an architecure if it supports 232 the API needed to access registers and stack entries from pt_regs, 233 declared in asm/ptrace.h 234 For example the kprobes-based event tracer needs this API. 235 236config HAVE_CLK 237 bool 238 help 239 The <linux/clk.h> calls support software clock gating and 240 thus are a key power management tool on many systems. 241 242config HAVE_DMA_API_DEBUG 243 bool 244 245config HAVE_HW_BREAKPOINT 246 bool 247 depends on PERF_EVENTS 248 249config HAVE_MIXED_BREAKPOINTS_REGS 250 bool 251 depends on HAVE_HW_BREAKPOINT 252 help 253 Depending on the arch implementation of hardware breakpoints, 254 some of them have separate registers for data and instruction 255 breakpoints addresses, others have mixed registers to store 256 them but define the access type in a control register. 257 Select this option if your arch implements breakpoints under the 258 latter fashion. 259 260config HAVE_USER_RETURN_NOTIFIER 261 bool 262 263config HAVE_PERF_EVENTS_NMI 264 bool 265 help 266 System hardware can generate an NMI using the perf event 267 subsystem. Also has support for calculating CPU cycle events 268 to determine how many clock cycles in a given period. 269 270config HAVE_PERF_REGS 271 bool 272 help 273 Support selective register dumps for perf events. This includes 274 bit-mapping of each registers and a unique architecture id. 275 276config HAVE_PERF_USER_STACK_DUMP 277 bool 278 help 279 Support user stack dumps for perf event samples. This needs 280 access to the user stack pointer which is not unified across 281 architectures. 282 283config HAVE_ARCH_JUMP_LABEL 284 bool 285 286config HAVE_RCU_TABLE_FREE 287 bool 288 289config ARCH_HAVE_NMI_SAFE_CMPXCHG 290 bool 291 292config HAVE_ALIGNED_STRUCT_PAGE 293 bool 294 help 295 This makes sure that struct pages are double word aligned and that 296 e.g. the SLUB allocator can perform double word atomic operations 297 on a struct page for better performance. However selecting this 298 might increase the size of a struct page by a word. 299 300config HAVE_CMPXCHG_LOCAL 301 bool 302 303config HAVE_CMPXCHG_DOUBLE 304 bool 305 306config ARCH_WANT_IPC_PARSE_VERSION 307 bool 308 309config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 310 bool 311 312config ARCH_WANT_OLD_COMPAT_IPC 313 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 314 bool 315 316config HAVE_ARCH_SECCOMP_FILTER 317 bool 318 help 319 An arch should select this symbol if it provides all of these things: 320 - syscall_get_arch() 321 - syscall_get_arguments() 322 - syscall_rollback() 323 - syscall_set_return_value() 324 - SIGSYS siginfo_t support 325 - secure_computing is called from a ptrace_event()-safe context 326 - secure_computing return value is checked and a return value of -1 327 results in the system call being skipped immediately. 328 329config SECCOMP_FILTER 330 def_bool y 331 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 332 help 333 Enable tasks to build secure computing environments defined 334 in terms of Berkeley Packet Filter programs which implement 335 task-defined system call filtering polices. 336 337 See Documentation/prctl/seccomp_filter.txt for details. 338 339config HAVE_CC_STACKPROTECTOR 340 bool 341 help 342 An arch should select this symbol if: 343 - its compiler supports the -fstack-protector option 344 - it has implemented a stack canary (e.g. __stack_chk_guard) 345 346config CC_STACKPROTECTOR 347 def_bool n 348 help 349 Set when a stack-protector mode is enabled, so that the build 350 can enable kernel-side support for the GCC feature. 351 352choice 353 prompt "Stack Protector buffer overflow detection" 354 depends on HAVE_CC_STACKPROTECTOR 355 default CC_STACKPROTECTOR_NONE 356 help 357 This option turns on the "stack-protector" GCC feature. This 358 feature puts, at the beginning of functions, a canary value on 359 the stack just before the return address, and validates 360 the value just before actually returning. Stack based buffer 361 overflows (that need to overwrite this return address) now also 362 overwrite the canary, which gets detected and the attack is then 363 neutralized via a kernel panic. 364 365config CC_STACKPROTECTOR_NONE 366 bool "None" 367 help 368 Disable "stack-protector" GCC feature. 369 370config CC_STACKPROTECTOR_REGULAR 371 bool "Regular" 372 select CC_STACKPROTECTOR 373 help 374 Functions will have the stack-protector canary logic added if they 375 have an 8-byte or larger character array on the stack. 376 377 This feature requires gcc version 4.2 or above, or a distribution 378 gcc with the feature backported ("-fstack-protector"). 379 380 On an x86 "defconfig" build, this feature adds canary checks to 381 about 3% of all kernel functions, which increases kernel code size 382 by about 0.3%. 383 384config CC_STACKPROTECTOR_STRONG 385 bool "Strong" 386 select CC_STACKPROTECTOR 387 help 388 Functions will have the stack-protector canary logic added in any 389 of the following conditions: 390 391 - local variable's address used as part of the right hand side of an 392 assignment or function argument 393 - local variable is an array (or union containing an array), 394 regardless of array type or length 395 - uses register local variables 396 397 This feature requires gcc version 4.9 or above, or a distribution 398 gcc with the feature backported ("-fstack-protector-strong"). 399 400 On an x86 "defconfig" build, this feature adds canary checks to 401 about 20% of all kernel functions, which increases the kernel code 402 size by about 2%. 403 404endchoice 405 406config HAVE_CONTEXT_TRACKING 407 bool 408 help 409 Provide kernel/user boundaries probes necessary for subsystems 410 that need it, such as userspace RCU extended quiescent state. 411 Syscalls need to be wrapped inside user_exit()-user_enter() through 412 the slow path using TIF_NOHZ flag. Exceptions handlers must be 413 wrapped as well. Irqs are already protected inside 414 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 415 irq exit still need to be protected. 416 417config HAVE_VIRT_CPU_ACCOUNTING 418 bool 419 420config HAVE_VIRT_CPU_ACCOUNTING_GEN 421 bool 422 default y if 64BIT 423 help 424 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 425 Before enabling this option, arch code must be audited 426 to ensure there are no races in concurrent read/write of 427 cputime_t. For example, reading/writing 64-bit cputime_t on 428 some 32-bit arches may require multiple accesses, so proper 429 locking is needed to protect against concurrent accesses. 430 431 432config HAVE_IRQ_TIME_ACCOUNTING 433 bool 434 help 435 Archs need to ensure they use a high enough resolution clock to 436 support irq time accounting and then call enable_sched_clock_irqtime(). 437 438config HAVE_ARCH_TRANSPARENT_HUGEPAGE 439 bool 440 441config HAVE_ARCH_SOFT_DIRTY 442 bool 443 444config HAVE_MOD_ARCH_SPECIFIC 445 bool 446 help 447 The arch uses struct mod_arch_specific to store data. Many arches 448 just need a simple module loader without arch specific data - those 449 should not enable this. 450 451config MODULES_USE_ELF_RELA 452 bool 453 help 454 Modules only use ELF RELA relocations. Modules with ELF REL 455 relocations will give an error. 456 457config MODULES_USE_ELF_REL 458 bool 459 help 460 Modules only use ELF REL relocations. Modules with ELF RELA 461 relocations will give an error. 462 463config HAVE_UNDERSCORE_SYMBOL_PREFIX 464 bool 465 help 466 Some architectures generate an _ in front of C symbols; things like 467 module loading and assembly files need to know about this. 468 469config HAVE_IRQ_EXIT_ON_IRQ_STACK 470 bool 471 help 472 Architecture doesn't only execute the irq handler on the irq stack 473 but also irq_exit(). This way we can process softirqs on this irq 474 stack instead of switching to a new one when we call __do_softirq() 475 in the end of an hardirq. 476 This spares a stack switch and improves cache usage on softirq 477 processing. 478 479# 480# ABI hall of shame 481# 482config CLONE_BACKWARDS 483 bool 484 help 485 Architecture has tls passed as the 4th argument of clone(2), 486 not the 5th one. 487 488config CLONE_BACKWARDS2 489 bool 490 help 491 Architecture has the first two arguments of clone(2) swapped. 492 493config CLONE_BACKWARDS3 494 bool 495 help 496 Architecture has tls passed as the 3rd argument of clone(2), 497 not the 5th one. 498 499config ODD_RT_SIGACTION 500 bool 501 help 502 Architecture has unusual rt_sigaction(2) arguments 503 504config OLD_SIGSUSPEND 505 bool 506 help 507 Architecture has old sigsuspend(2) syscall, of one-argument variety 508 509config OLD_SIGSUSPEND3 510 bool 511 help 512 Even weirder antique ABI - three-argument sigsuspend(2) 513 514config OLD_SIGACTION 515 bool 516 help 517 Architecture has old sigaction(2) syscall. Nope, not the same 518 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 519 but fairly different variant of sigaction(2), thanks to OSF/1 520 compatibility... 521 522config COMPAT_OLD_SIGACTION 523 bool 524 525source "kernel/gcov/Kconfig" 526