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 && !PPC64 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 223 224# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 225config ARCH_WANTS_DYNAMIC_TASK_STRUCT 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 - seccomp syscall wired up 329 330 For best performance, an arch should use seccomp_phase1 and 331 seccomp_phase2 directly. It should call seccomp_phase1 for all 332 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not 333 need to be called from a ptrace-safe context. It must then 334 call seccomp_phase2 if seccomp_phase1 returns anything other 335 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP. 336 337 As an additional optimization, an arch may provide seccomp_data 338 directly to seccomp_phase1; this avoids multiple calls 339 to the syscall_xyz helpers for every syscall. 340 341config SECCOMP_FILTER 342 def_bool y 343 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 344 help 345 Enable tasks to build secure computing environments defined 346 in terms of Berkeley Packet Filter programs which implement 347 task-defined system call filtering polices. 348 349 See Documentation/prctl/seccomp_filter.txt for details. 350 351config HAVE_CC_STACKPROTECTOR 352 bool 353 help 354 An arch should select this symbol if: 355 - its compiler supports the -fstack-protector option 356 - it has implemented a stack canary (e.g. __stack_chk_guard) 357 358config CC_STACKPROTECTOR 359 def_bool n 360 help 361 Set when a stack-protector mode is enabled, so that the build 362 can enable kernel-side support for the GCC feature. 363 364choice 365 prompt "Stack Protector buffer overflow detection" 366 depends on HAVE_CC_STACKPROTECTOR 367 default CC_STACKPROTECTOR_NONE 368 help 369 This option turns on the "stack-protector" GCC feature. This 370 feature puts, at the beginning of functions, a canary value on 371 the stack just before the return address, and validates 372 the value just before actually returning. Stack based buffer 373 overflows (that need to overwrite this return address) now also 374 overwrite the canary, which gets detected and the attack is then 375 neutralized via a kernel panic. 376 377config CC_STACKPROTECTOR_NONE 378 bool "None" 379 help 380 Disable "stack-protector" GCC feature. 381 382config CC_STACKPROTECTOR_REGULAR 383 bool "Regular" 384 select CC_STACKPROTECTOR 385 help 386 Functions will have the stack-protector canary logic added if they 387 have an 8-byte or larger character array on the stack. 388 389 This feature requires gcc version 4.2 or above, or a distribution 390 gcc with the feature backported ("-fstack-protector"). 391 392 On an x86 "defconfig" build, this feature adds canary checks to 393 about 3% of all kernel functions, which increases kernel code size 394 by about 0.3%. 395 396config CC_STACKPROTECTOR_STRONG 397 bool "Strong" 398 select CC_STACKPROTECTOR 399 help 400 Functions will have the stack-protector canary logic added in any 401 of the following conditions: 402 403 - local variable's address used as part of the right hand side of an 404 assignment or function argument 405 - local variable is an array (or union containing an array), 406 regardless of array type or length 407 - uses register local variables 408 409 This feature requires gcc version 4.9 or above, or a distribution 410 gcc with the feature backported ("-fstack-protector-strong"). 411 412 On an x86 "defconfig" build, this feature adds canary checks to 413 about 20% of all kernel functions, which increases the kernel code 414 size by about 2%. 415 416endchoice 417 418config HAVE_CONTEXT_TRACKING 419 bool 420 help 421 Provide kernel/user boundaries probes necessary for subsystems 422 that need it, such as userspace RCU extended quiescent state. 423 Syscalls need to be wrapped inside user_exit()-user_enter() through 424 the slow path using TIF_NOHZ flag. Exceptions handlers must be 425 wrapped as well. Irqs are already protected inside 426 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 427 irq exit still need to be protected. 428 429config HAVE_VIRT_CPU_ACCOUNTING 430 bool 431 432config HAVE_VIRT_CPU_ACCOUNTING_GEN 433 bool 434 default y if 64BIT 435 help 436 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 437 Before enabling this option, arch code must be audited 438 to ensure there are no races in concurrent read/write of 439 cputime_t. For example, reading/writing 64-bit cputime_t on 440 some 32-bit arches may require multiple accesses, so proper 441 locking is needed to protect against concurrent accesses. 442 443 444config HAVE_IRQ_TIME_ACCOUNTING 445 bool 446 help 447 Archs need to ensure they use a high enough resolution clock to 448 support irq time accounting and then call enable_sched_clock_irqtime(). 449 450config HAVE_ARCH_TRANSPARENT_HUGEPAGE 451 bool 452 453config HAVE_ARCH_HUGE_VMAP 454 bool 455 456config HAVE_ARCH_SOFT_DIRTY 457 bool 458 459config HAVE_MOD_ARCH_SPECIFIC 460 bool 461 help 462 The arch uses struct mod_arch_specific to store data. Many arches 463 just need a simple module loader without arch specific data - those 464 should not enable this. 465 466config MODULES_USE_ELF_RELA 467 bool 468 help 469 Modules only use ELF RELA relocations. Modules with ELF REL 470 relocations will give an error. 471 472config MODULES_USE_ELF_REL 473 bool 474 help 475 Modules only use ELF REL relocations. Modules with ELF RELA 476 relocations will give an error. 477 478config HAVE_UNDERSCORE_SYMBOL_PREFIX 479 bool 480 help 481 Some architectures generate an _ in front of C symbols; things like 482 module loading and assembly files need to know about this. 483 484config HAVE_IRQ_EXIT_ON_IRQ_STACK 485 bool 486 help 487 Architecture doesn't only execute the irq handler on the irq stack 488 but also irq_exit(). This way we can process softirqs on this irq 489 stack instead of switching to a new one when we call __do_softirq() 490 in the end of an hardirq. 491 This spares a stack switch and improves cache usage on softirq 492 processing. 493 494config PGTABLE_LEVELS 495 int 496 default 2 497 498config ARCH_HAS_ELF_RANDOMIZE 499 bool 500 help 501 An architecture supports choosing randomized locations for 502 stack, mmap, brk, and ET_DYN. Defined functions: 503 - arch_mmap_rnd() 504 - arch_randomize_brk() 505 506config HAVE_COPY_THREAD_TLS 507 bool 508 help 509 Architecture provides copy_thread_tls to accept tls argument via 510 normal C parameter passing, rather than extracting the syscall 511 argument from pt_regs. 512 513# 514# ABI hall of shame 515# 516config CLONE_BACKWARDS 517 bool 518 help 519 Architecture has tls passed as the 4th argument of clone(2), 520 not the 5th one. 521 522config CLONE_BACKWARDS2 523 bool 524 help 525 Architecture has the first two arguments of clone(2) swapped. 526 527config CLONE_BACKWARDS3 528 bool 529 help 530 Architecture has tls passed as the 3rd argument of clone(2), 531 not the 5th one. 532 533config ODD_RT_SIGACTION 534 bool 535 help 536 Architecture has unusual rt_sigaction(2) arguments 537 538config OLD_SIGSUSPEND 539 bool 540 help 541 Architecture has old sigsuspend(2) syscall, of one-argument variety 542 543config OLD_SIGSUSPEND3 544 bool 545 help 546 Even weirder antique ABI - three-argument sigsuspend(2) 547 548config OLD_SIGACTION 549 bool 550 help 551 Architecture has old sigaction(2) syscall. Nope, not the same 552 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 553 but fairly different variant of sigaction(2), thanks to OSF/1 554 compatibility... 555 556config COMPAT_OLD_SIGACTION 557 bool 558 559source "kernel/gcov/Kconfig" 560