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