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 STATIC_KEYS_SELFTEST 75 bool "Static key selftest" 76 depends on JUMP_LABEL 77 help 78 Boot time self-test of the branch patching code. 79 80config OPTPROBES 81 def_bool y 82 depends on KPROBES && HAVE_OPTPROBES 83 depends on !PREEMPT 84 85config KPROBES_ON_FTRACE 86 def_bool y 87 depends on KPROBES && HAVE_KPROBES_ON_FTRACE 88 depends on DYNAMIC_FTRACE_WITH_REGS 89 help 90 If function tracer is enabled and the arch supports full 91 passing of pt_regs to function tracing, then kprobes can 92 optimize on top of function tracing. 93 94config UPROBES 95 def_bool n 96 select PERCPU_RWSEM 97 help 98 Uprobes is the user-space counterpart to kprobes: they 99 enable instrumentation applications (such as 'perf probe') 100 to establish unintrusive probes in user-space binaries and 101 libraries, by executing handler functions when the probes 102 are hit by user-space applications. 103 104 ( These probes come in the form of single-byte breakpoints, 105 managed by the kernel and kept transparent to the probed 106 application. ) 107 108config HAVE_64BIT_ALIGNED_ACCESS 109 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS 110 help 111 Some architectures require 64 bit accesses to be 64 bit 112 aligned, which also requires structs containing 64 bit values 113 to be 64 bit aligned too. This includes some 32 bit 114 architectures which can do 64 bit accesses, as well as 64 bit 115 architectures without unaligned access. 116 117 This symbol should be selected by an architecture if 64 bit 118 accesses are required to be 64 bit aligned in this way even 119 though it is not a 64 bit architecture. 120 121 See Documentation/unaligned-memory-access.txt for more 122 information on the topic of unaligned memory accesses. 123 124config HAVE_EFFICIENT_UNALIGNED_ACCESS 125 bool 126 help 127 Some architectures are unable to perform unaligned accesses 128 without the use of get_unaligned/put_unaligned. Others are 129 unable to perform such accesses efficiently (e.g. trap on 130 unaligned access and require fixing it up in the exception 131 handler.) 132 133 This symbol should be selected by an architecture if it can 134 perform unaligned accesses efficiently to allow different 135 code paths to be selected for these cases. Some network 136 drivers, for example, could opt to not fix up alignment 137 problems with received packets if doing so would not help 138 much. 139 140 See Documentation/unaligned-memory-access.txt for more 141 information on the topic of unaligned memory accesses. 142 143config ARCH_USE_BUILTIN_BSWAP 144 bool 145 help 146 Modern versions of GCC (since 4.4) have builtin functions 147 for handling byte-swapping. Using these, instead of the old 148 inline assembler that the architecture code provides in the 149 __arch_bswapXX() macros, allows the compiler to see what's 150 happening and offers more opportunity for optimisation. In 151 particular, the compiler will be able to combine the byteswap 152 with a nearby load or store and use load-and-swap or 153 store-and-swap instructions if the architecture has them. It 154 should almost *never* result in code which is worse than the 155 hand-coded assembler in <asm/swab.h>. But just in case it 156 does, the use of the builtins is optional. 157 158 Any architecture with load-and-swap or store-and-swap 159 instructions should set this. And it shouldn't hurt to set it 160 on architectures that don't have such instructions. 161 162config KRETPROBES 163 def_bool y 164 depends on KPROBES && HAVE_KRETPROBES 165 166config USER_RETURN_NOTIFIER 167 bool 168 depends on HAVE_USER_RETURN_NOTIFIER 169 help 170 Provide a kernel-internal notification when a cpu is about to 171 switch to user mode. 172 173config HAVE_IOREMAP_PROT 174 bool 175 176config HAVE_KPROBES 177 bool 178 179config HAVE_KRETPROBES 180 bool 181 182config HAVE_OPTPROBES 183 bool 184 185config HAVE_KPROBES_ON_FTRACE 186 bool 187 188config HAVE_NMI_WATCHDOG 189 bool 190# 191# An arch should select this if it provides all these things: 192# 193# task_pt_regs() in asm/processor.h or asm/ptrace.h 194# arch_has_single_step() if there is hardware single-step support 195# arch_has_block_step() if there is hardware block-step support 196# asm/syscall.h supplying asm-generic/syscall.h interface 197# linux/regset.h user_regset interfaces 198# CORE_DUMP_USE_REGSET #define'd in linux/elf.h 199# TIF_SYSCALL_TRACE calls tracehook_report_syscall_{entry,exit} 200# TIF_NOTIFY_RESUME calls tracehook_notify_resume() 201# signal delivery calls tracehook_signal_handler() 202# 203config HAVE_ARCH_TRACEHOOK 204 bool 205 206config HAVE_DMA_ATTRS 207 bool 208 209config HAVE_DMA_CONTIGUOUS 210 bool 211 212config GENERIC_SMP_IDLE_THREAD 213 bool 214 215config GENERIC_IDLE_POLL_SETUP 216 bool 217 218# Select if arch init_task initializer is different to init/init_task.c 219config ARCH_INIT_TASK 220 bool 221 222# Select if arch has its private alloc_task_struct() function 223config ARCH_TASK_STRUCT_ALLOCATOR 224 bool 225 226# Select if arch has its private alloc_thread_info() function 227config ARCH_THREAD_INFO_ALLOCATOR 228 bool 229 230# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 231config ARCH_WANTS_DYNAMIC_TASK_STRUCT 232 bool 233 234config HAVE_REGS_AND_STACK_ACCESS_API 235 bool 236 help 237 This symbol should be selected by an architecure if it supports 238 the API needed to access registers and stack entries from pt_regs, 239 declared in asm/ptrace.h 240 For example the kprobes-based event tracer needs this API. 241 242config HAVE_CLK 243 bool 244 help 245 The <linux/clk.h> calls support software clock gating and 246 thus are a key power management tool on many systems. 247 248config HAVE_DMA_API_DEBUG 249 bool 250 251config HAVE_HW_BREAKPOINT 252 bool 253 depends on PERF_EVENTS 254 255config HAVE_MIXED_BREAKPOINTS_REGS 256 bool 257 depends on HAVE_HW_BREAKPOINT 258 help 259 Depending on the arch implementation of hardware breakpoints, 260 some of them have separate registers for data and instruction 261 breakpoints addresses, others have mixed registers to store 262 them but define the access type in a control register. 263 Select this option if your arch implements breakpoints under the 264 latter fashion. 265 266config HAVE_USER_RETURN_NOTIFIER 267 bool 268 269config HAVE_PERF_EVENTS_NMI 270 bool 271 help 272 System hardware can generate an NMI using the perf event 273 subsystem. Also has support for calculating CPU cycle events 274 to determine how many clock cycles in a given period. 275 276config HAVE_PERF_REGS 277 bool 278 help 279 Support selective register dumps for perf events. This includes 280 bit-mapping of each registers and a unique architecture id. 281 282config HAVE_PERF_USER_STACK_DUMP 283 bool 284 help 285 Support user stack dumps for perf event samples. This needs 286 access to the user stack pointer which is not unified across 287 architectures. 288 289config HAVE_ARCH_JUMP_LABEL 290 bool 291 292config HAVE_RCU_TABLE_FREE 293 bool 294 295config ARCH_HAVE_NMI_SAFE_CMPXCHG 296 bool 297 298config HAVE_ALIGNED_STRUCT_PAGE 299 bool 300 help 301 This makes sure that struct pages are double word aligned and that 302 e.g. the SLUB allocator can perform double word atomic operations 303 on a struct page for better performance. However selecting this 304 might increase the size of a struct page by a word. 305 306config HAVE_CMPXCHG_LOCAL 307 bool 308 309config HAVE_CMPXCHG_DOUBLE 310 bool 311 312config ARCH_WANT_IPC_PARSE_VERSION 313 bool 314 315config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 316 bool 317 318config ARCH_WANT_OLD_COMPAT_IPC 319 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 320 bool 321 322config HAVE_ARCH_SECCOMP_FILTER 323 bool 324 help 325 An arch should select this symbol if it provides all of these things: 326 - syscall_get_arch() 327 - syscall_get_arguments() 328 - syscall_rollback() 329 - syscall_set_return_value() 330 - SIGSYS siginfo_t support 331 - secure_computing is called from a ptrace_event()-safe context 332 - secure_computing return value is checked and a return value of -1 333 results in the system call being skipped immediately. 334 - seccomp syscall wired up 335 336 For best performance, an arch should use seccomp_phase1 and 337 seccomp_phase2 directly. It should call seccomp_phase1 for all 338 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not 339 need to be called from a ptrace-safe context. It must then 340 call seccomp_phase2 if seccomp_phase1 returns anything other 341 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP. 342 343 As an additional optimization, an arch may provide seccomp_data 344 directly to seccomp_phase1; this avoids multiple calls 345 to the syscall_xyz helpers for every syscall. 346 347config SECCOMP_FILTER 348 def_bool y 349 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 350 help 351 Enable tasks to build secure computing environments defined 352 in terms of Berkeley Packet Filter programs which implement 353 task-defined system call filtering polices. 354 355 See Documentation/prctl/seccomp_filter.txt for details. 356 357config HAVE_CC_STACKPROTECTOR 358 bool 359 help 360 An arch should select this symbol if: 361 - its compiler supports the -fstack-protector option 362 - it has implemented a stack canary (e.g. __stack_chk_guard) 363 364config CC_STACKPROTECTOR 365 def_bool n 366 help 367 Set when a stack-protector mode is enabled, so that the build 368 can enable kernel-side support for the GCC feature. 369 370choice 371 prompt "Stack Protector buffer overflow detection" 372 depends on HAVE_CC_STACKPROTECTOR 373 default CC_STACKPROTECTOR_NONE 374 help 375 This option turns on the "stack-protector" GCC feature. This 376 feature puts, at the beginning of functions, a canary value on 377 the stack just before the return address, and validates 378 the value just before actually returning. Stack based buffer 379 overflows (that need to overwrite this return address) now also 380 overwrite the canary, which gets detected and the attack is then 381 neutralized via a kernel panic. 382 383config CC_STACKPROTECTOR_NONE 384 bool "None" 385 help 386 Disable "stack-protector" GCC feature. 387 388config CC_STACKPROTECTOR_REGULAR 389 bool "Regular" 390 select CC_STACKPROTECTOR 391 help 392 Functions will have the stack-protector canary logic added if they 393 have an 8-byte or larger character array on the stack. 394 395 This feature requires gcc version 4.2 or above, or a distribution 396 gcc with the feature backported ("-fstack-protector"). 397 398 On an x86 "defconfig" build, this feature adds canary checks to 399 about 3% of all kernel functions, which increases kernel code size 400 by about 0.3%. 401 402config CC_STACKPROTECTOR_STRONG 403 bool "Strong" 404 select CC_STACKPROTECTOR 405 help 406 Functions will have the stack-protector canary logic added in any 407 of the following conditions: 408 409 - local variable's address used as part of the right hand side of an 410 assignment or function argument 411 - local variable is an array (or union containing an array), 412 regardless of array type or length 413 - uses register local variables 414 415 This feature requires gcc version 4.9 or above, or a distribution 416 gcc with the feature backported ("-fstack-protector-strong"). 417 418 On an x86 "defconfig" build, this feature adds canary checks to 419 about 20% of all kernel functions, which increases the kernel code 420 size by about 2%. 421 422endchoice 423 424config HAVE_CONTEXT_TRACKING 425 bool 426 help 427 Provide kernel/user boundaries probes necessary for subsystems 428 that need it, such as userspace RCU extended quiescent state. 429 Syscalls need to be wrapped inside user_exit()-user_enter() through 430 the slow path using TIF_NOHZ flag. Exceptions handlers must be 431 wrapped as well. Irqs are already protected inside 432 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 433 irq exit still need to be protected. 434 435config HAVE_VIRT_CPU_ACCOUNTING 436 bool 437 438config HAVE_VIRT_CPU_ACCOUNTING_GEN 439 bool 440 default y if 64BIT 441 help 442 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 443 Before enabling this option, arch code must be audited 444 to ensure there are no races in concurrent read/write of 445 cputime_t. For example, reading/writing 64-bit cputime_t on 446 some 32-bit arches may require multiple accesses, so proper 447 locking is needed to protect against concurrent accesses. 448 449 450config HAVE_IRQ_TIME_ACCOUNTING 451 bool 452 help 453 Archs need to ensure they use a high enough resolution clock to 454 support irq time accounting and then call enable_sched_clock_irqtime(). 455 456config HAVE_ARCH_TRANSPARENT_HUGEPAGE 457 bool 458 459config HAVE_ARCH_HUGE_VMAP 460 bool 461 462config HAVE_ARCH_SOFT_DIRTY 463 bool 464 465config HAVE_MOD_ARCH_SPECIFIC 466 bool 467 help 468 The arch uses struct mod_arch_specific to store data. Many arches 469 just need a simple module loader without arch specific data - those 470 should not enable this. 471 472config MODULES_USE_ELF_RELA 473 bool 474 help 475 Modules only use ELF RELA relocations. Modules with ELF REL 476 relocations will give an error. 477 478config MODULES_USE_ELF_REL 479 bool 480 help 481 Modules only use ELF REL relocations. Modules with ELF RELA 482 relocations will give an error. 483 484config HAVE_UNDERSCORE_SYMBOL_PREFIX 485 bool 486 help 487 Some architectures generate an _ in front of C symbols; things like 488 module loading and assembly files need to know about this. 489 490config HAVE_IRQ_EXIT_ON_IRQ_STACK 491 bool 492 help 493 Architecture doesn't only execute the irq handler on the irq stack 494 but also irq_exit(). This way we can process softirqs on this irq 495 stack instead of switching to a new one when we call __do_softirq() 496 in the end of an hardirq. 497 This spares a stack switch and improves cache usage on softirq 498 processing. 499 500config PGTABLE_LEVELS 501 int 502 default 2 503 504config ARCH_HAS_ELF_RANDOMIZE 505 bool 506 help 507 An architecture supports choosing randomized locations for 508 stack, mmap, brk, and ET_DYN. Defined functions: 509 - arch_mmap_rnd() 510 - arch_randomize_brk() 511 512config HAVE_COPY_THREAD_TLS 513 bool 514 help 515 Architecture provides copy_thread_tls to accept tls argument via 516 normal C parameter passing, rather than extracting the syscall 517 argument from pt_regs. 518 519# 520# ABI hall of shame 521# 522config CLONE_BACKWARDS 523 bool 524 help 525 Architecture has tls passed as the 4th argument of clone(2), 526 not the 5th one. 527 528config CLONE_BACKWARDS2 529 bool 530 help 531 Architecture has the first two arguments of clone(2) swapped. 532 533config CLONE_BACKWARDS3 534 bool 535 help 536 Architecture has tls passed as the 3rd argument of clone(2), 537 not the 5th one. 538 539config ODD_RT_SIGACTION 540 bool 541 help 542 Architecture has unusual rt_sigaction(2) arguments 543 544config OLD_SIGSUSPEND 545 bool 546 help 547 Architecture has old sigsuspend(2) syscall, of one-argument variety 548 549config OLD_SIGSUSPEND3 550 bool 551 help 552 Even weirder antique ABI - three-argument sigsuspend(2) 553 554config OLD_SIGACTION 555 bool 556 help 557 Architecture has old sigaction(2) syscall. Nope, not the same 558 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 559 but fairly different variant of sigaction(2), thanks to OSF/1 560 compatibility... 561 562config COMPAT_OLD_SIGACTION 563 bool 564 565source "kernel/gcov/Kconfig" 566