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_CONTIGUOUS 209 bool 210 211config GENERIC_SMP_IDLE_THREAD 212 bool 213 214config GENERIC_IDLE_POLL_SETUP 215 bool 216 217# Select if arch init_task initializer is different to init/init_task.c 218config ARCH_INIT_TASK 219 bool 220 221# Select if arch has its private alloc_task_struct() function 222config ARCH_TASK_STRUCT_ALLOCATOR 223 bool 224 225# Select if arch has its private alloc_thread_info() function 226config ARCH_THREAD_INFO_ALLOCATOR 227 bool 228 229# Select if arch wants to size task_struct dynamically via arch_task_struct_size: 230config ARCH_WANTS_DYNAMIC_TASK_STRUCT 231 bool 232 233config HAVE_REGS_AND_STACK_ACCESS_API 234 bool 235 help 236 This symbol should be selected by an architecure if it supports 237 the API needed to access registers and stack entries from pt_regs, 238 declared in asm/ptrace.h 239 For example the kprobes-based event tracer needs this API. 240 241config HAVE_CLK 242 bool 243 help 244 The <linux/clk.h> calls support software clock gating and 245 thus are a key power management tool on many systems. 246 247config HAVE_DMA_API_DEBUG 248 bool 249 250config HAVE_HW_BREAKPOINT 251 bool 252 depends on PERF_EVENTS 253 254config HAVE_MIXED_BREAKPOINTS_REGS 255 bool 256 depends on HAVE_HW_BREAKPOINT 257 help 258 Depending on the arch implementation of hardware breakpoints, 259 some of them have separate registers for data and instruction 260 breakpoints addresses, others have mixed registers to store 261 them but define the access type in a control register. 262 Select this option if your arch implements breakpoints under the 263 latter fashion. 264 265config HAVE_USER_RETURN_NOTIFIER 266 bool 267 268config HAVE_PERF_EVENTS_NMI 269 bool 270 help 271 System hardware can generate an NMI using the perf event 272 subsystem. Also has support for calculating CPU cycle events 273 to determine how many clock cycles in a given period. 274 275config HAVE_PERF_REGS 276 bool 277 help 278 Support selective register dumps for perf events. This includes 279 bit-mapping of each registers and a unique architecture id. 280 281config HAVE_PERF_USER_STACK_DUMP 282 bool 283 help 284 Support user stack dumps for perf event samples. This needs 285 access to the user stack pointer which is not unified across 286 architectures. 287 288config HAVE_ARCH_JUMP_LABEL 289 bool 290 291config HAVE_RCU_TABLE_FREE 292 bool 293 294config ARCH_HAVE_NMI_SAFE_CMPXCHG 295 bool 296 297config HAVE_ALIGNED_STRUCT_PAGE 298 bool 299 help 300 This makes sure that struct pages are double word aligned and that 301 e.g. the SLUB allocator can perform double word atomic operations 302 on a struct page for better performance. However selecting this 303 might increase the size of a struct page by a word. 304 305config HAVE_CMPXCHG_LOCAL 306 bool 307 308config HAVE_CMPXCHG_DOUBLE 309 bool 310 311config ARCH_WANT_IPC_PARSE_VERSION 312 bool 313 314config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 315 bool 316 317config ARCH_WANT_OLD_COMPAT_IPC 318 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION 319 bool 320 321config HAVE_ARCH_SECCOMP_FILTER 322 bool 323 help 324 An arch should select this symbol if it provides all of these things: 325 - syscall_get_arch() 326 - syscall_get_arguments() 327 - syscall_rollback() 328 - syscall_set_return_value() 329 - SIGSYS siginfo_t support 330 - secure_computing is called from a ptrace_event()-safe context 331 - secure_computing return value is checked and a return value of -1 332 results in the system call being skipped immediately. 333 - seccomp syscall wired up 334 335 For best performance, an arch should use seccomp_phase1 and 336 seccomp_phase2 directly. It should call seccomp_phase1 for all 337 syscalls if TIF_SECCOMP is set, but seccomp_phase1 does not 338 need to be called from a ptrace-safe context. It must then 339 call seccomp_phase2 if seccomp_phase1 returns anything other 340 than SECCOMP_PHASE1_OK or SECCOMP_PHASE1_SKIP. 341 342 As an additional optimization, an arch may provide seccomp_data 343 directly to seccomp_phase1; this avoids multiple calls 344 to the syscall_xyz helpers for every syscall. 345 346config SECCOMP_FILTER 347 def_bool y 348 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET 349 help 350 Enable tasks to build secure computing environments defined 351 in terms of Berkeley Packet Filter programs which implement 352 task-defined system call filtering polices. 353 354 See Documentation/prctl/seccomp_filter.txt for details. 355 356config HAVE_CC_STACKPROTECTOR 357 bool 358 help 359 An arch should select this symbol if: 360 - its compiler supports the -fstack-protector option 361 - it has implemented a stack canary (e.g. __stack_chk_guard) 362 363config CC_STACKPROTECTOR 364 def_bool n 365 help 366 Set when a stack-protector mode is enabled, so that the build 367 can enable kernel-side support for the GCC feature. 368 369choice 370 prompt "Stack Protector buffer overflow detection" 371 depends on HAVE_CC_STACKPROTECTOR 372 default CC_STACKPROTECTOR_NONE 373 help 374 This option turns on the "stack-protector" GCC feature. This 375 feature puts, at the beginning of functions, a canary value on 376 the stack just before the return address, and validates 377 the value just before actually returning. Stack based buffer 378 overflows (that need to overwrite this return address) now also 379 overwrite the canary, which gets detected and the attack is then 380 neutralized via a kernel panic. 381 382config CC_STACKPROTECTOR_NONE 383 bool "None" 384 help 385 Disable "stack-protector" GCC feature. 386 387config CC_STACKPROTECTOR_REGULAR 388 bool "Regular" 389 select CC_STACKPROTECTOR 390 help 391 Functions will have the stack-protector canary logic added if they 392 have an 8-byte or larger character array on the stack. 393 394 This feature requires gcc version 4.2 or above, or a distribution 395 gcc with the feature backported ("-fstack-protector"). 396 397 On an x86 "defconfig" build, this feature adds canary checks to 398 about 3% of all kernel functions, which increases kernel code size 399 by about 0.3%. 400 401config CC_STACKPROTECTOR_STRONG 402 bool "Strong" 403 select CC_STACKPROTECTOR 404 help 405 Functions will have the stack-protector canary logic added in any 406 of the following conditions: 407 408 - local variable's address used as part of the right hand side of an 409 assignment or function argument 410 - local variable is an array (or union containing an array), 411 regardless of array type or length 412 - uses register local variables 413 414 This feature requires gcc version 4.9 or above, or a distribution 415 gcc with the feature backported ("-fstack-protector-strong"). 416 417 On an x86 "defconfig" build, this feature adds canary checks to 418 about 20% of all kernel functions, which increases the kernel code 419 size by about 2%. 420 421endchoice 422 423config HAVE_CONTEXT_TRACKING 424 bool 425 help 426 Provide kernel/user boundaries probes necessary for subsystems 427 that need it, such as userspace RCU extended quiescent state. 428 Syscalls need to be wrapped inside user_exit()-user_enter() through 429 the slow path using TIF_NOHZ flag. Exceptions handlers must be 430 wrapped as well. Irqs are already protected inside 431 rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on 432 irq exit still need to be protected. 433 434config HAVE_VIRT_CPU_ACCOUNTING 435 bool 436 437config HAVE_VIRT_CPU_ACCOUNTING_GEN 438 bool 439 default y if 64BIT 440 help 441 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. 442 Before enabling this option, arch code must be audited 443 to ensure there are no races in concurrent read/write of 444 cputime_t. For example, reading/writing 64-bit cputime_t on 445 some 32-bit arches may require multiple accesses, so proper 446 locking is needed to protect against concurrent accesses. 447 448 449config HAVE_IRQ_TIME_ACCOUNTING 450 bool 451 help 452 Archs need to ensure they use a high enough resolution clock to 453 support irq time accounting and then call enable_sched_clock_irqtime(). 454 455config HAVE_ARCH_TRANSPARENT_HUGEPAGE 456 bool 457 458config HAVE_ARCH_HUGE_VMAP 459 bool 460 461config HAVE_ARCH_SOFT_DIRTY 462 bool 463 464config HAVE_MOD_ARCH_SPECIFIC 465 bool 466 help 467 The arch uses struct mod_arch_specific to store data. Many arches 468 just need a simple module loader without arch specific data - those 469 should not enable this. 470 471config MODULES_USE_ELF_RELA 472 bool 473 help 474 Modules only use ELF RELA relocations. Modules with ELF REL 475 relocations will give an error. 476 477config MODULES_USE_ELF_REL 478 bool 479 help 480 Modules only use ELF REL relocations. Modules with ELF RELA 481 relocations will give an error. 482 483config HAVE_UNDERSCORE_SYMBOL_PREFIX 484 bool 485 help 486 Some architectures generate an _ in front of C symbols; things like 487 module loading and assembly files need to know about this. 488 489config HAVE_IRQ_EXIT_ON_IRQ_STACK 490 bool 491 help 492 Architecture doesn't only execute the irq handler on the irq stack 493 but also irq_exit(). This way we can process softirqs on this irq 494 stack instead of switching to a new one when we call __do_softirq() 495 in the end of an hardirq. 496 This spares a stack switch and improves cache usage on softirq 497 processing. 498 499config PGTABLE_LEVELS 500 int 501 default 2 502 503config ARCH_HAS_ELF_RANDOMIZE 504 bool 505 help 506 An architecture supports choosing randomized locations for 507 stack, mmap, brk, and ET_DYN. Defined functions: 508 - arch_mmap_rnd() 509 - arch_randomize_brk() 510 511config HAVE_ARCH_MMAP_RND_BITS 512 bool 513 help 514 An arch should select this symbol if it supports setting a variable 515 number of bits for use in establishing the base address for mmap 516 allocations, has MMU enabled and provides values for both: 517 - ARCH_MMAP_RND_BITS_MIN 518 - ARCH_MMAP_RND_BITS_MAX 519 520config HAVE_EXIT_THREAD 521 bool 522 help 523 An architecture implements exit_thread. 524 525config ARCH_MMAP_RND_BITS_MIN 526 int 527 528config ARCH_MMAP_RND_BITS_MAX 529 int 530 531config ARCH_MMAP_RND_BITS_DEFAULT 532 int 533 534config ARCH_MMAP_RND_BITS 535 int "Number of bits to use for ASLR of mmap base address" if EXPERT 536 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX 537 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT 538 default ARCH_MMAP_RND_BITS_MIN 539 depends on HAVE_ARCH_MMAP_RND_BITS 540 help 541 This value can be used to select the number of bits to use to 542 determine the random offset to the base address of vma regions 543 resulting from mmap allocations. This value will be bounded 544 by the architecture's minimum and maximum supported values. 545 546 This value can be changed after boot using the 547 /proc/sys/vm/mmap_rnd_bits tunable 548 549config HAVE_ARCH_MMAP_RND_COMPAT_BITS 550 bool 551 help 552 An arch should select this symbol if it supports running applications 553 in compatibility mode, supports setting a variable number of bits for 554 use in establishing the base address for mmap allocations, has MMU 555 enabled and provides values for both: 556 - ARCH_MMAP_RND_COMPAT_BITS_MIN 557 - ARCH_MMAP_RND_COMPAT_BITS_MAX 558 559config ARCH_MMAP_RND_COMPAT_BITS_MIN 560 int 561 562config ARCH_MMAP_RND_COMPAT_BITS_MAX 563 int 564 565config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 566 int 567 568config ARCH_MMAP_RND_COMPAT_BITS 569 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT 570 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX 571 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 572 default ARCH_MMAP_RND_COMPAT_BITS_MIN 573 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS 574 help 575 This value can be used to select the number of bits to use to 576 determine the random offset to the base address of vma regions 577 resulting from mmap allocations for compatible applications This 578 value will be bounded by the architecture's minimum and maximum 579 supported values. 580 581 This value can be changed after boot using the 582 /proc/sys/vm/mmap_rnd_compat_bits tunable 583 584config HAVE_COPY_THREAD_TLS 585 bool 586 help 587 Architecture provides copy_thread_tls to accept tls argument via 588 normal C parameter passing, rather than extracting the syscall 589 argument from pt_regs. 590 591config HAVE_STACK_VALIDATION 592 bool 593 help 594 Architecture supports the 'objtool check' host tool command, which 595 performs compile-time stack metadata validation. 596 597# 598# ABI hall of shame 599# 600config CLONE_BACKWARDS 601 bool 602 help 603 Architecture has tls passed as the 4th argument of clone(2), 604 not the 5th one. 605 606config CLONE_BACKWARDS2 607 bool 608 help 609 Architecture has the first two arguments of clone(2) swapped. 610 611config CLONE_BACKWARDS3 612 bool 613 help 614 Architecture has tls passed as the 3rd argument of clone(2), 615 not the 5th one. 616 617config ODD_RT_SIGACTION 618 bool 619 help 620 Architecture has unusual rt_sigaction(2) arguments 621 622config OLD_SIGSUSPEND 623 bool 624 help 625 Architecture has old sigsuspend(2) syscall, of one-argument variety 626 627config OLD_SIGSUSPEND3 628 bool 629 help 630 Even weirder antique ABI - three-argument sigsuspend(2) 631 632config OLD_SIGACTION 633 bool 634 help 635 Architecture has old sigaction(2) syscall. Nope, not the same 636 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2), 637 but fairly different variant of sigaction(2), thanks to OSF/1 638 compatibility... 639 640config COMPAT_OLD_SIGACTION 641 bool 642 643config ARCH_NO_COHERENT_DMA_MMAP 644 bool 645 646source "kernel/gcov/Kconfig" 647