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config ARCH string option env="ARCH" config KERNELVERSION string option env="KERNELVERSION" config DEFCONFIG_LIST string depends on !UML option defconfig_list default "/lib/modules/$UNAME_RELEASE/.config" default "/etc/kernel-config" default "/boot/config-$UNAME_RELEASE" default "$ARCH_DEFCONFIG" default "arch/$ARCH/defconfig" menu "General setup" config EXPERIMENTAL bool "Prompt for development and/or incomplete code/drivers" ---help--- Some of the various things that Linux supports (such as network drivers, file systems, network protocols, etc.) can be in a state of development where the functionality, stability, or the level of testing is not yet high enough for general use. This is usually known as the "alpha-test" phase among developers. If a feature is currently in alpha-test, then the developers usually discourage uninformed widespread use of this feature by the general public to avoid "Why doesn't this work?" type mail messages. However, active testing and use of these systems is welcomed. Just be aware that it may not meet the normal level of reliability or it may fail to work in some special cases. Detailed bug reports from people familiar with the kernel internals are usually welcomed by the developers (before submitting bug reports, please read the documents <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, <file:Documentation/BUG-HUNTING>, and <file:Documentation/oops-tracing.txt> in the kernel source). This option will also make obsoleted drivers available. These are drivers that have been replaced by something else, and/or are scheduled to be removed in a future kernel release. Unless you intend to help test and develop a feature or driver that falls into this category, or you have a situation that requires using these features, you should probably say N here, which will cause the configurator to present you with fewer choices. If you say Y here, you will be offered the choice of using features or drivers that are currently considered to be in the alpha-test phase. config BROKEN bool config BROKEN_ON_SMP bool depends on BROKEN || !SMP default y config LOCK_KERNEL bool depends on SMP || PREEMPT default y config INIT_ENV_ARG_LIMIT int default 32 if !UML default 128 if UML help Maximum of each of the number of arguments and environment variables passed to init from the kernel command line. config LOCALVERSION string "Local version - append to kernel release" help Append an extra string to the end of your kernel version. This will show up when you type uname, for example. The string you set here will be appended after the contents of any files with a filename matching localversion* in your object and source tree, in that order. Your total string can be a maximum of 64 characters. config LOCALVERSION_AUTO bool "Automatically append version information to the version string" default y help This will try to automatically determine if the current tree is a release tree by looking for git tags that belong to the current top of tree revision. A string of the format -gxxxxxxxx will be added to the localversion if a git-based tree is found. The string generated by this will be appended after any matching localversion* files, and after the value set in CONFIG_LOCALVERSION. (The actual string used here is the first eight characters produced by running the command: $ git rev-parse --verify HEAD which is done within the script "scripts/setlocalversion".) config VERSION_SIGNATURE string "Arbitrary version signature" help This string will be created in a file, /proc/version_signature. It is useful in determining arbitrary data about your kernel. For instance, if you have several kernels of the same version, but need to keep track of a revision of the same kernel, but not affect it's ability to load compatible modules, this is the easiest way to do that. config SWAP bool "Support for paging of anonymous memory (swap)" depends on MMU && BLOCK default y help This option allows you to choose whether you want to have support for so called swap devices or swap files in your kernel that are used to provide more virtual memory than the actual RAM present in your computer. If unsure say Y. config SYSVIPC bool "System V IPC" ---help--- Inter Process Communication is a suite of library functions and system calls which let processes (running programs) synchronize and exchange information. It is generally considered to be a good thing, and some programs won't run unless you say Y here. In particular, if you want to run the DOS emulator dosemu under Linux (read the DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), you'll need to say Y here. You can find documentation about IPC with "info ipc" and also in section 6.4 of the Linux Programmer's Guide, available from <http://www.tldp.org/guides.html>. config SYSVIPC_SYSCTL bool depends on SYSVIPC depends on SYSCTL default y config POSIX_MQUEUE bool "POSIX Message Queues" depends on NET && EXPERIMENTAL ---help--- POSIX variant of message queues is a part of IPC. In POSIX message queues every message has a priority which decides about succession of receiving it by a process. If you want to compile and run programs written e.g. for Solaris with use of its POSIX message queues (functions mq_*) say Y here. POSIX message queues are visible as a filesystem called 'mqueue' and can be mounted somewhere if you want to do filesystem operations on message queues. If unsure, say Y. config BSD_PROCESS_ACCT bool "BSD Process Accounting" help If you say Y here, a user level program will be able to instruct the kernel (via a special system call) to write process accounting information to a file: whenever a process exits, information about that process will be appended to the file by the kernel. The information includes things such as creation time, owning user, command name, memory usage, controlling terminal etc. (the complete list is in the struct acct in <file:include/linux/acct.h>). It is up to the user level program to do useful things with this information. This is generally a good idea, so say Y. config BSD_PROCESS_ACCT_V3 bool "BSD Process Accounting version 3 file format" depends on BSD_PROCESS_ACCT default n help If you say Y here, the process accounting information is written in a new file format that also logs the process IDs of each process and it's parent. Note that this file format is incompatible with previous v0/v1/v2 file formats, so you will need updated tools for processing it. A preliminary version of these tools is available at <http://www.gnu.org/software/acct/>. config TASKSTATS bool "Export task/process statistics through netlink (EXPERIMENTAL)" depends on NET default n help Export selected statistics for tasks/processes through the generic netlink interface. Unlike BSD process accounting, the statistics are available during the lifetime of tasks/processes as responses to commands. Like BSD accounting, they are sent to user space on task exit. Say N if unsure. config TASK_DELAY_ACCT bool "Enable per-task delay accounting (EXPERIMENTAL)" depends on TASKSTATS help Collect information on time spent by a task waiting for system resources like cpu, synchronous block I/O completion and swapping in pages. Such statistics can help in setting a task's priorities relative to other tasks for cpu, io, rss limits etc. Say N if unsure. config TASK_XACCT bool "Enable extended accounting over taskstats (EXPERIMENTAL)" depends on TASKSTATS help Collect extended task accounting data and send the data to userland for processing over the taskstats interface. Say N if unsure. config TASK_IO_ACCOUNTING bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" depends on TASK_XACCT help Collect information on the number of bytes of storage I/O which this task has caused. Say N if unsure. config AUDIT bool "Auditing support" depends on NET help Enable auditing infrastructure that can be used with another kernel subsystem, such as SELinux (which requires this for logging of avc messages output). Does not do system-call auditing without CONFIG_AUDITSYSCALL. config AUDITSYSCALL bool "Enable system-call auditing support" depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH) default y if SECURITY_SELINUX help Enable low-overhead system-call auditing infrastructure that can be used independently or with another kernel subsystem, such as SELinux. To use audit's filesystem watch feature, please ensure that INOTIFY is configured. config AUDIT_TREE def_bool y depends on AUDITSYSCALL && INOTIFY config IKCONFIG tristate "Kernel .config support" ---help--- This option enables the complete Linux kernel ".config" file contents to be saved in the kernel. It provides documentation of which kernel options are used in a running kernel or in an on-disk kernel. This information can be extracted from the kernel image file with the script scripts/extract-ikconfig and used as input to rebuild the current kernel or to build another kernel. It can also be extracted from a running kernel by reading /proc/config.gz if enabled (below). config IKCONFIG_PROC bool "Enable access to .config through /proc/config.gz" depends on IKCONFIG && PROC_FS ---help--- This option enables access to the kernel configuration file through /proc/config.gz. config LOG_BUF_SHIFT int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" range 12 21 default 17 help Select kernel log buffer size as a power of 2. Examples: 17 => 128 KB 16 => 64 KB 15 => 32 KB 14 => 16 KB 13 => 8 KB 12 => 4 KB config CGROUPS bool "Control Group support" help This option will let you use process cgroup subsystems such as Cpusets Say N if unsure. config CGROUP_DEBUG bool "Example debug cgroup subsystem" depends on CGROUPS default n help This option enables a simple cgroup subsystem that exports useful debugging information about the cgroups framework Say N if unsure config CGROUP_NS bool "Namespace cgroup subsystem" depends on CGROUPS help Provides a simple namespace cgroup subsystem to provide hierarchical naming of sets of namespaces, for instance virtual servers and checkpoint/restart jobs. config CGROUP_DEVICE bool "Device controller for cgroups" depends on CGROUPS && EXPERIMENTAL help Provides a cgroup implementing whitelists for devices which a process in the cgroup can mknod or open. config CPUSETS bool "Cpuset support" depends on SMP && CGROUPS help This option will let you create and manage CPUSETs which allow dynamically partitioning a system into sets of CPUs and Memory Nodes and assigning tasks to run only within those sets. This is primarily useful on large SMP or NUMA systems. Say N if unsure. # # Architectures with an unreliable sched_clock() should select this: # config HAVE_UNSTABLE_SCHED_CLOCK bool config GROUP_SCHED bool "Group CPU scheduler" depends on EXPERIMENTAL default n help This feature lets CPU scheduler recognize task groups and control CPU bandwidth allocation to such task groups. config FAIR_GROUP_SCHED bool "Group scheduling for SCHED_OTHER" depends on GROUP_SCHED default GROUP_SCHED config RT_GROUP_SCHED bool "Group scheduling for SCHED_RR/FIFO" depends on EXPERIMENTAL depends on GROUP_SCHED default n help This feature lets you explicitly allocate real CPU bandwidth to users or control groups (depending on the "Basis for grouping tasks" setting below. If enabled, it will also make it impossible to schedule realtime tasks for non-root users until you allocate realtime bandwidth for them. See Documentation/sched-rt-group.txt for more information. choice depends on GROUP_SCHED prompt "Basis for grouping tasks" default USER_SCHED config USER_SCHED bool "user id" help This option will choose userid as the basis for grouping tasks, thus providing equal CPU bandwidth to each user. config CGROUP_SCHED bool "Control groups" depends on CGROUPS help This option allows you to create arbitrary task groups using the "cgroup" pseudo filesystem and control the cpu bandwidth allocated to each such task group. Refer to Documentation/cgroups.txt for more information on "cgroup" pseudo filesystem. endchoice config CGROUP_CPUACCT bool "Simple CPU accounting cgroup subsystem" depends on CGROUPS help Provides a simple Resource Controller for monitoring the total CPU consumed by the tasks in a cgroup config RESOURCE_COUNTERS bool "Resource counters" help This option enables controller independent resource accounting infrastructure that works with cgroups depends on CGROUPS config MM_OWNER bool config CGROUP_MEM_RES_CTLR bool "Memory Resource Controller for Control Groups" depends on CGROUPS && RESOURCE_COUNTERS select MM_OWNER help Provides a memory resource controller that manages both page cache and RSS memory. Note that setting this option increases fixed memory overhead associated with each page of memory in the system by 4/8 bytes and also increases cache misses because struct page on many 64bit systems will not fit into a single cache line anymore. Only enable when you're ok with these trade offs and really sure you need the memory resource controller. This config option also selects MM_OWNER config option, which could in turn add some fork/exit overhead. config SYSFS_DEPRECATED bool config SYSFS_DEPRECATED_V2 bool "Create deprecated sysfs files" depends on SYSFS default y select SYSFS_DEPRECATED help This option creates deprecated symlinks such as the "device"-link, the <subsystem>:<name>-link, and the "bus"-link. It may also add deprecated key in the uevent environment. None of these features or values should be used today, as they export driver core implementation details to userspace or export properties which can't be kept stable across kernel releases. If enabled, this option will also move any device structures that belong to a class, back into the /sys/class hierarchy, in order to support older versions of udev and some userspace programs. If you are using a distro with the most recent userspace packages, it should be safe to say N here. config PROC_PID_CPUSET bool "Include legacy /proc/<pid>/cpuset file" depends on CPUSETS default y config RELAY bool "Kernel->user space relay support (formerly relayfs)" help This option enables support for relay interface support in certain file systems (such as debugfs). It is designed to provide an efficient mechanism for tools and facilities to relay large amounts of data from kernel space to user space. If unsure, say N. config NAMESPACES bool "Namespaces support" if EMBEDDED default !EMBEDDED help Provides the way to make tasks work with different objects using the same id. For example same IPC id may refer to different objects or same user id or pid may refer to different tasks when used in different namespaces. config UTS_NS bool "UTS namespace" depends on NAMESPACES help In this namespace tasks see different info provided with the uname() system call config IPC_NS bool "IPC namespace" depends on NAMESPACES && SYSVIPC help In this namespace tasks work with IPC ids which correspond to different IPC objects in different namespaces config USER_NS bool "User namespace (EXPERIMENTAL)" depends on NAMESPACES && EXPERIMENTAL help This allows containers, i.e. vservers, to use user namespaces to provide different user info for different servers. If unsure, say N. config PID_NS bool "PID Namespaces (EXPERIMENTAL)" default n depends on NAMESPACES && EXPERIMENTAL help Support process id namespaces. This allows having multiple process with the same pid as long as they are in different pid namespaces. This is a building block of containers. Unless you want to work with an experimental feature say N here. config BLK_DEV_INITRD bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" depends on BROKEN || !FRV help The initial RAM filesystem is a ramfs which is loaded by the boot loader (loadlin or lilo) and that is mounted as root before the normal boot procedure. It is typically used to load modules needed to mount the "real" root file system, etc. See <file:Documentation/initrd.txt> for details. If RAM disk support (BLK_DEV_RAM) is also included, this also enables initial RAM disk (initrd) support and adds 15 Kbytes (more on some other architectures) to the kernel size. If unsure say Y. if BLK_DEV_INITRD source "usr/Kconfig" endif config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size" default y help Enabling this option will pass "-Os" instead of "-O2" to gcc resulting in a smaller kernel. If unsure, say Y. config SYSCTL bool menuconfig EMBEDDED bool "Configure standard kernel features (for small systems)" help This option allows certain base kernel options and settings to be disabled or tweaked. This is for specialized environments which can tolerate a "non-standard" kernel. Only use this if you really know what you are doing. config UID16 bool "Enable 16-bit UID system calls" if EMBEDDED depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) default y help This enables the legacy 16-bit UID syscall wrappers. config SYSCTL_SYSCALL bool "Sysctl syscall support" if EMBEDDED default y select SYSCTL ---help--- sys_sysctl uses binary paths that have been found challenging to properly maintain and use. The interface in /proc/sys using paths with ascii names is now the primary path to this information. Almost nothing using the binary sysctl interface so if you are trying to save some space it is probably safe to disable this, making your kernel marginally smaller. If unsure say Y here. config KALLSYMS bool "Load all symbols for debugging/ksymoops" if EMBEDDED default y help Say Y here to let the kernel print out symbolic crash information and symbolic stack backtraces. This increases the size of the kernel somewhat, as all symbols have to be loaded into the kernel image. config KALLSYMS_ALL bool "Include all symbols in kallsyms" depends on DEBUG_KERNEL && KALLSYMS help Normally kallsyms only contains the symbols of functions, for nicer OOPS messages. Some debuggers can use kallsyms for other symbols too: say Y here to include all symbols, if you need them and you don't care about adding 300k to the size of your kernel. Say N. config KALLSYMS_EXTRA_PASS bool "Do an extra kallsyms pass" depends on KALLSYMS help If kallsyms is not working correctly, the build will fail with inconsistent kallsyms data. If that occurs, log a bug report and turn on KALLSYMS_EXTRA_PASS which should result in a stable build. Always say N here unless you find a bug in kallsyms, which must be reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while you wait for kallsyms to be fixed. config HOTPLUG bool "Support for hot-pluggable devices" if EMBEDDED default y help This option is provided for the case where no hotplug or uevent capabilities is wanted by the kernel. You should only consider disabling this option for embedded systems that do not use modules, a dynamic /dev tree, or dynamic device discovery. Just say Y. config PRINTK default y bool "Enable support for printk" if EMBEDDED help This option enables normal printk support. Removing it eliminates most of the message strings from the kernel image and makes the kernel more or less silent. As this makes it very difficult to diagnose system problems, saying N here is strongly discouraged. config BUG bool "BUG() support" if EMBEDDED default y help Disabling this option eliminates support for BUG and WARN, reducing the size of your kernel image and potentially quietly ignoring numerous fatal conditions. You should only consider disabling this option for embedded systems with no facilities for reporting errors. Just say Y. config ELF_CORE default y bool "Enable ELF core dumps" if EMBEDDED help Enable support for generating core dumps. Disabling saves about 4k. config PCSPKR_PLATFORM bool "Enable PC-Speaker support" if EMBEDDED depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES default y help This option allows to disable the internal PC-Speaker support, saving some memory. config COMPAT_BRK bool "Disable heap randomization" default y help Randomizing heap placement makes heap exploits harder, but it also breaks ancient binaries (including anything libc5 based). This option changes the bootup default to heap randomization disabled, and can be overriden runtime by setting /proc/sys/kernel/randomize_va_space to 2. On non-ancient distros (post-2000 ones) N is usually a safe choice. config BASE_FULL default y bool "Enable full-sized data structures for core" if EMBEDDED help Disabling this option reduces the size of miscellaneous core kernel data structures. This saves memory on small machines, but may reduce performance. config FUTEX bool "Enable futex support" if EMBEDDED default y select RT_MUTEXES help Disabling this option will cause the kernel to be built without support for "fast userspace mutexes". The resulting kernel may not run glibc-based applications correctly. config ANON_INODES bool config EPOLL bool "Enable eventpoll support" if EMBEDDED default y select ANON_INODES help Disabling this option will cause the kernel to be built without support for epoll family of system calls. config SIGNALFD bool "Enable signalfd() system call" if EMBEDDED select ANON_INODES default y help Enable the signalfd() system call that allows to receive signals on a file descriptor. If unsure, say Y. config TIMERFD bool "Enable timerfd() system call" if EMBEDDED select ANON_INODES default y help Enable the timerfd() system call that allows to receive timer events on a file descriptor. If unsure, say Y. config EVENTFD bool "Enable eventfd() system call" if EMBEDDED select ANON_INODES default y help Enable the eventfd() system call that allows to receive both kernel notification (ie. KAIO) or userspace notifications. If unsure, say Y. config SHMEM bool "Use full shmem filesystem" if EMBEDDED default y depends on MMU help The shmem is an internal filesystem used to manage shared memory. It is backed by swap and manages resource limits. It is also exported to userspace as tmpfs if TMPFS is enabled. Disabling this option replaces shmem and tmpfs with the much simpler ramfs code, which may be appropriate on small systems without swap. config VM_EVENT_COUNTERS default y bool "Enable VM event counters for /proc/vmstat" if EMBEDDED help VM event counters are needed for event counts to be shown. This option allows the disabling of the VM event counters on EMBEDDED systems. /proc/vmstat will only show page counts if VM event counters are disabled. config SLUB_DEBUG default y bool "Enable SLUB debugging support" if EMBEDDED depends on SLUB && SYSFS help SLUB has extensive debug support features. Disabling these can result in significant savings in code size. This also disables SLUB sysfs support. /sys/slab will not exist and there will be no support for cache validation etc. choice prompt "Choose SLAB allocator" default SLUB help This option allows to select a slab allocator. config SLAB bool "SLAB" help The regular slab allocator that is established and known to work well in all environments. It organizes cache hot objects in per cpu and per node queues. SLAB is the default choice for a slab allocator. config SLUB bool "SLUB (Unqueued Allocator)" help SLUB is a slab allocator that minimizes cache line usage instead of managing queues of cached objects (SLAB approach). Per cpu caching is realized using slabs of objects instead of queues of objects. SLUB can use memory efficiently and has enhanced diagnostics. config SLOB depends on EMBEDDED bool "SLOB (Simple Allocator)" help SLOB replaces the stock allocator with a drastically simpler allocator. SLOB is generally more space efficient but does not perform as well on large systems. endchoice config PROFILING bool "Profiling support (EXPERIMENTAL)" help Say Y here to enable the extended profiling support mechanisms used by profilers such as OProfile. config MARKERS bool "Activate markers" help Place an empty function call at each marker site. Can be dynamically changed for a probe function. source "arch/Kconfig" config PROC_PAGE_MONITOR default y depends on PROC_FS && MMU bool "Enable /proc page monitoring" if EMBEDDED help Various /proc files exist to monitor process memory utilization: /proc/pid/smaps, /proc/pid/clear_refs, /proc/pid/pagemap, /proc/kpagecount, and /proc/kpageflags. Disabling these interfaces will reduce the size of the kernel by approximately 4kb. endmenu # General setup config HAVE_GENERIC_DMA_COHERENT bool default n config SLABINFO bool depends on PROC_FS depends on SLAB || SLUB_DEBUG default y config RT_MUTEXES boolean select PLIST config TINY_SHMEM default !SHMEM bool config BASE_SMALL int default 0 if BASE_FULL default 1 if !BASE_FULL menuconfig MODULES bool "Enable loadable module support" help Kernel modules are small pieces of compiled code which can be inserted in the running kernel, rather than being permanently built into the kernel. You use the "modprobe" tool to add (and sometimes remove) them. If you say Y here, many parts of the kernel can be built as modules (by answering M instead of Y where indicated): this is most useful for infrequently used options which are not required for booting. For more information, see the man pages for modprobe, lsmod, modinfo, insmod and rmmod. If you say Y here, you will need to run "make modules_install" to put the modules under /lib/modules/ where modprobe can find them (you may need to be root to do this). If unsure, say Y. if MODULES config MODULE_FORCE_LOAD bool "Forced module loading" default n help Allow loading of modules without version information (ie. modprobe --force). Forced module loading sets the 'F' (forced) taint flag and is usually a really bad idea. config MODULE_UNLOAD bool "Module unloading" help Without this option you will not be able to unload any modules (note that some modules may not be unloadable anyway), which makes your kernel smaller, faster and simpler. If unsure, say Y. config MODULE_FORCE_UNLOAD bool "Forced module unloading" depends on MODULE_UNLOAD && EXPERIMENTAL help This option allows you to force a module to unload, even if the kernel believes it is unsafe: the kernel will remove the module without waiting for anyone to stop using it (using the -f option to rmmod). This is mainly for kernel developers and desperate users. If unsure, say N. config MODVERSIONS bool "Module versioning support" help Usually, you have to use modules compiled with your kernel. Saying Y here makes it sometimes possible to use modules compiled for different kernels, by adding enough information to the modules to (hopefully) spot any changes which would make them incompatible with the kernel you are running. If unsure, say N. config MODULE_SRCVERSION_ALL bool "Source checksum for all modules" help Modules which contain a MODULE_VERSION get an extra "srcversion" field inserted into their modinfo section, which contains a sum of the source files which made it. This helps maintainers see exactly which source was used to build a module (since others sometimes change the module source without updating the version). With this option, such a "srcversion" field will be created for all modules. If unsure, say N. config KMOD def_bool y help This is being removed soon. These days, CONFIG_MODULES implies CONFIG_KMOD, so use that instead. endif # MODULES config STOP_MACHINE bool default y depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU help Need stop_machine() primitive. source "block/Kconfig" config PREEMPT_NOTIFIERS bool config CLASSIC_RCU def_bool !PREEMPT_RCU help This option selects the classic RCU implementation that is designed for best read-side performance on non-realtime systems. Classic RCU is the default. Note that the PREEMPT_RCU symbol is used to select/deselect this option.