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config PRINTK_TIME bool "Show timing information on printks" depends on PRINTK help Selecting this option causes timing information to be included in printk output. This allows you to measure the interval between kernel operations, including bootup operations. This is useful for identifying long delays in kernel startup. config ENABLE_WARN_DEPRECATED bool "Enable __deprecated logic" default y help Enable the __deprecated logic in the kernel build. Disable this to suppress the "warning: 'foo' is deprecated (declared at kernel/power/somefile.c:1234)" messages. config ENABLE_MUST_CHECK bool "Enable __must_check logic" default y help Enable the __must_check logic in the kernel build. Disable this to suppress the "warning: ignoring return value of 'foo', declared with attribute warn_unused_result" messages. config FRAME_WARN int "Warn for stack frames larger than (needs gcc 4.4)" range 0 8192 default 1024 if !64BIT default 2048 if 64BIT help Tell gcc to warn at build time for stack frames larger than this. Setting this too low will cause a lot of warnings. Setting it to 0 disables the warning. Requires gcc 4.4 config MAGIC_SYSRQ bool "Magic SysRq key" depends on !UML help If you say Y here, you will have some control over the system even if the system crashes for example during kernel debugging (e.g., you will be able to flush the buffer cache to disk, reboot the system immediately or dump some status information). This is accomplished by pressing various keys while holding SysRq (Alt+PrintScreen). It also works on a serial console (on PC hardware at least), if you send a BREAK and then within 5 seconds a command keypress. The keys are documented in <file:Documentation/sysrq.txt>. Don't say Y unless you really know what this hack does. config UNUSED_SYMBOLS bool "Enable unused/obsolete exported symbols" default y if X86 help Unused but exported symbols make the kernel needlessly bigger. For that reason most of these unused exports will soon be removed. This option is provided temporarily to provide a transition period in case some external kernel module needs one of these symbols anyway. If you encounter such a case in your module, consider if you are actually using the right API. (rationale: since nobody in the kernel is using this in a module, there is a pretty good chance it's actually the wrong interface to use). If you really need the symbol, please send a mail to the linux kernel mailing list mentioning the symbol and why you really need it, and what the merge plan to the mainline kernel for your module is. config DEBUG_FS bool "Debug Filesystem" depends on SYSFS help debugfs is a virtual file system that kernel developers use to put debugging files into. Enable this option to be able to read and write to these files. For detailed documentation on the debugfs API, see Documentation/DocBook/filesystems. If unsure, say N. config HEADERS_CHECK bool "Run 'make headers_check' when building vmlinux" depends on !UML help This option will extract the user-visible kernel headers whenever building the kernel, and will run basic sanity checks on them to ensure that exported files do not attempt to include files which were not exported, etc. If you're making modifications to header files which are relevant for userspace, say 'Y', and check the headers exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in your build tree), to make sure they're suitable. config DEBUG_SECTION_MISMATCH bool "Enable full Section mismatch analysis" depends on UNDEFINED # This option is on purpose disabled for now. # It will be enabled when we are down to a resonable number # of section mismatch warnings (< 10 for an allyesconfig build) help The section mismatch analysis checks if there are illegal references from one section to another section. Linux will during link or during runtime drop some sections and any use of code/data previously in these sections will most likely result in an oops. In the code functions and variables are annotated with __init, __devinit etc. (see full list in include/linux/init.h) which results in the code/data being placed in specific sections. The section mismatch analysis is always done after a full kernel build but enabling this option will in addition do the following: - Add the option -fno-inline-functions-called-once to gcc When inlining a function annotated __init in a non-init function we would lose the section information and thus the analysis would not catch the illegal reference. This option tells gcc to inline less but will also result in a larger kernel. - Run the section mismatch analysis for each module/built-in.o When we run the section mismatch analysis on vmlinux.o we lose valueble information about where the mismatch was introduced. Running the analysis for each module/built-in.o file will tell where the mismatch happens much closer to the source. The drawback is that we will report the same mismatch at least twice. - Enable verbose reporting from modpost to help solving the section mismatches reported. config DEBUG_KERNEL bool "Kernel debugging" help Say Y here if you are developing drivers or trying to debug and identify kernel problems. config DEBUG_SHIRQ bool "Debug shared IRQ handlers" depends on DEBUG_KERNEL && GENERIC_HARDIRQS help Enable this to generate a spurious interrupt as soon as a shared interrupt handler is registered, and just before one is deregistered. Drivers ought to be able to handle interrupts coming in at those points; some don't and need to be caught. config DETECT_SOFTLOCKUP bool "Detect Soft Lockups" depends on DEBUG_KERNEL && !S390 default y help Say Y here to enable the kernel to detect "soft lockups", which are bugs that cause the kernel to loop in kernel mode for more than 60 seconds, without giving other tasks a chance to run. When a soft-lockup is detected, the kernel will print the current stack trace (which you should report), but the system will stay locked up. This feature has negligible overhead. (Note that "hard lockups" are separate type of bugs that can be detected via the NMI-watchdog, on platforms that support it.) config BOOTPARAM_SOFTLOCKUP_PANIC bool "Panic (Reboot) On Soft Lockups" depends on DETECT_SOFTLOCKUP help Say Y here to enable the kernel to panic on "soft lockups", which are bugs that cause the kernel to loop in kernel mode for more than 60 seconds, without giving other tasks a chance to run. The panic can be used in combination with panic_timeout, to cause the system to reboot automatically after a lockup has been detected. This feature is useful for high-availability systems that have uptime guarantees and where a lockup must be resolved ASAP. Say N if unsure. config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE int depends on DETECT_SOFTLOCKUP range 0 1 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC default 1 if BOOTPARAM_SOFTLOCKUP_PANIC config SCHED_DEBUG bool "Collect scheduler debugging info" depends on DEBUG_KERNEL && PROC_FS default y help If you say Y here, the /proc/sched_debug file will be provided that can help debug the scheduler. The runtime overhead of this option is minimal. config SCHEDSTATS bool "Collect scheduler statistics" depends on DEBUG_KERNEL && PROC_FS help If you say Y here, additional code will be inserted into the scheduler and related routines to collect statistics about scheduler behavior and provide them in /proc/schedstat. These stats may be useful for both tuning and debugging the scheduler If you aren't debugging the scheduler or trying to tune a specific application, you can say N to avoid the very slight overhead this adds. config TIMER_STATS bool "Collect kernel timers statistics" depends on DEBUG_KERNEL && PROC_FS help If you say Y here, additional code will be inserted into the timer routines to collect statistics about kernel timers being reprogrammed. The statistics can be read from /proc/timer_stats. The statistics collection is started by writing 1 to /proc/timer_stats, writing 0 stops it. This feature is useful to collect information about timer usage patterns in kernel and userspace. This feature is lightweight if enabled in the kernel config but not activated (it defaults to deactivated on bootup and will only be activated if some application like powertop activates it explicitly). config DEBUG_OBJECTS bool "Debug object operations" depends on DEBUG_KERNEL help If you say Y here, additional code will be inserted into the kernel to track the life time of various objects and validate the operations on those objects. config DEBUG_OBJECTS_SELFTEST bool "Debug objects selftest" depends on DEBUG_OBJECTS help This enables the selftest of the object debug code. config DEBUG_OBJECTS_FREE bool "Debug objects in freed memory" depends on DEBUG_OBJECTS help This enables checks whether a k/v free operation frees an area which contains an object which has not been deactivated properly. This can make kmalloc/kfree-intensive workloads much slower. config DEBUG_OBJECTS_TIMERS bool "Debug timer objects" depends on DEBUG_OBJECTS help If you say Y here, additional code will be inserted into the timer routines to track the life time of timer objects and validate the timer operations. config DEBUG_SLAB bool "Debug slab memory allocations" depends on DEBUG_KERNEL && SLAB help Say Y here to have the kernel do limited verification on memory allocation as well as poisoning memory on free to catch use of freed memory. This can make kmalloc/kfree-intensive workloads much slower. config DEBUG_SLAB_LEAK bool "Memory leak debugging" depends on DEBUG_SLAB config SLUB_DEBUG_ON bool "SLUB debugging on by default" depends on SLUB && SLUB_DEBUG default n help Boot with debugging on by default. SLUB boots by default with the runtime debug capabilities switched off. Enabling this is equivalent to specifying the "slub_debug" parameter on boot. There is no support for more fine grained debug control like possible with slub_debug=xxx. SLUB debugging may be switched off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying "slub_debug=-". config SLUB_STATS default n bool "Enable SLUB performance statistics" depends on SLUB && SLUB_DEBUG && SYSFS help SLUB statistics are useful to debug SLUBs allocation behavior in order find ways to optimize the allocator. This should never be enabled for production use since keeping statistics slows down the allocator by a few percentage points. The slabinfo command supports the determination of the most active slabs to figure out which slabs are relevant to a particular load. Try running: slabinfo -DA config DEBUG_PREEMPT bool "Debug preemptible kernel" depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) default y help If you say Y here then the kernel will use a debug variant of the commonly used smp_processor_id() function and will print warnings if kernel code uses it in a preemption-unsafe way. Also, the kernel will detect preemption count underflows. config DEBUG_RT_MUTEXES bool "RT Mutex debugging, deadlock detection" depends on DEBUG_KERNEL && RT_MUTEXES help This allows rt mutex semantics violations and rt mutex related deadlocks (lockups) to be detected and reported automatically. config DEBUG_PI_LIST bool default y depends on DEBUG_RT_MUTEXES config RT_MUTEX_TESTER bool "Built-in scriptable tester for rt-mutexes" depends on DEBUG_KERNEL && RT_MUTEXES help This option enables a rt-mutex tester. config DEBUG_SPINLOCK bool "Spinlock and rw-lock debugging: basic checks" depends on DEBUG_KERNEL help Say Y here and build SMP to catch missing spinlock initialization and certain other kinds of spinlock errors commonly made. This is best used in conjunction with the NMI watchdog so that spinlock deadlocks are also debuggable. config DEBUG_MUTEXES bool "Mutex debugging: basic checks" depends on DEBUG_KERNEL help This feature allows mutex semantics violations to be detected and reported. config DEBUG_LOCK_ALLOC bool "Lock debugging: detect incorrect freeing of live locks" depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select DEBUG_SPINLOCK select DEBUG_MUTEXES select LOCKDEP help This feature will check whether any held lock (spinlock, rwlock, mutex or rwsem) is incorrectly freed by the kernel, via any of the memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), vfree(), etc.), whether a live lock is incorrectly reinitialized via spin_lock_init()/mutex_init()/etc., or whether there is any lock held during task exit. config PROVE_LOCKING bool "Lock debugging: prove locking correctness" depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select LOCKDEP select DEBUG_SPINLOCK select DEBUG_MUTEXES select DEBUG_LOCK_ALLOC default n help This feature enables the kernel to prove that all locking that occurs in the kernel runtime is mathematically correct: that under no circumstance could an arbitrary (and not yet triggered) combination of observed locking sequences (on an arbitrary number of CPUs, running an arbitrary number of tasks and interrupt contexts) cause a deadlock. In short, this feature enables the kernel to report locking related deadlocks before they actually occur. The proof does not depend on how hard and complex a deadlock scenario would be to trigger: how many participant CPUs, tasks and irq-contexts would be needed for it to trigger. The proof also does not depend on timing: if a race and a resulting deadlock is possible theoretically (no matter how unlikely the race scenario is), it will be proven so and will immediately be reported by the kernel (once the event is observed that makes the deadlock theoretically possible). If a deadlock is impossible (i.e. the locking rules, as observed by the kernel, are mathematically correct), the kernel reports nothing. NOTE: this feature can also be enabled for rwlocks, mutexes and rwsems - in which case all dependencies between these different locking variants are observed and mapped too, and the proof of observed correctness is also maintained for an arbitrary combination of these separate locking variants. For more details, see Documentation/lockdep-design.txt. config LOCKDEP bool depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select STACKTRACE select FRAME_POINTER if !X86 && !MIPS && !PPC select KALLSYMS select KALLSYMS_ALL config LOCK_STAT bool "Lock usage statistics" depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select LOCKDEP select DEBUG_SPINLOCK select DEBUG_MUTEXES select DEBUG_LOCK_ALLOC default n help This feature enables tracking lock contention points For more details, see Documentation/lockstat.txt config DEBUG_LOCKDEP bool "Lock dependency engine debugging" depends on DEBUG_KERNEL && LOCKDEP help If you say Y here, the lock dependency engine will do additional runtime checks to debug itself, at the price of more runtime overhead. config TRACE_IRQFLAGS depends on DEBUG_KERNEL bool default y depends on TRACE_IRQFLAGS_SUPPORT depends on PROVE_LOCKING config DEBUG_SPINLOCK_SLEEP bool "Spinlock debugging: sleep-inside-spinlock checking" depends on DEBUG_KERNEL help If you say Y here, various routines which may sleep will become very noisy if they are called with a spinlock held. config DEBUG_LOCKING_API_SELFTESTS bool "Locking API boot-time self-tests" depends on DEBUG_KERNEL help Say Y here if you want the kernel to run a short self-test during bootup. The self-test checks whether common types of locking bugs are detected by debugging mechanisms or not. (if you disable lock debugging then those bugs wont be detected of course.) The following locking APIs are covered: spinlocks, rwlocks, mutexes and rwsems. config STACKTRACE bool depends on STACKTRACE_SUPPORT config DEBUG_KOBJECT bool "kobject debugging" depends on DEBUG_KERNEL help If you say Y here, some extra kobject debugging messages will be sent to the syslog. config DEBUG_HIGHMEM bool "Highmem debugging" depends on DEBUG_KERNEL && HIGHMEM help This options enables addition error checking for high memory systems. Disable for production systems. config DEBUG_BUGVERBOSE bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED depends on BUG depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 default !EMBEDDED help Say Y here to make BUG() panics output the file name and line number of the BUG call as well as the EIP and oops trace. This aids debugging but costs about 70-100K of memory. config DEBUG_INFO bool "Compile the kernel with debug info" depends on DEBUG_KERNEL help If you say Y here the resulting kernel image will include debugging info resulting in a larger kernel image. This adds debug symbols to the kernel and modules (gcc -g), and is needed if you intend to use kernel crashdump or binary object tools like crash, kgdb, LKCD, gdb, etc on the kernel. Say Y here only if you plan to debug the kernel. If unsure, say N. config DEBUG_VM bool "Debug VM" depends on DEBUG_KERNEL help Enable this to turn on extended checks in the virtual-memory system that may impact performance. If unsure, say N. config DEBUG_WRITECOUNT bool "Debug filesystem writers count" depends on DEBUG_KERNEL help Enable this to catch wrong use of the writers count in struct vfsmount. This will increase the size of each file struct by 32 bits. If unsure, say N. config DEBUG_MEMORY_INIT bool "Debug memory initialisation" if EMBEDDED default !EMBEDDED help Enable this for additional checks during memory initialisation. The sanity checks verify aspects of the VM such as the memory model and other information provided by the architecture. Verbose information will be printed at KERN_DEBUG loglevel depending on the mminit_loglevel= command-line option. If unsure, say Y config DEBUG_LIST bool "Debug linked list manipulation" depends on DEBUG_KERNEL help Enable this to turn on extended checks in the linked-list walking routines. If unsure, say N. config DEBUG_SG bool "Debug SG table operations" depends on DEBUG_KERNEL help Enable this to turn on checks on scatter-gather tables. This can help find problems with drivers that do not properly initialize their sg tables. If unsure, say N. config FRAME_POINTER bool "Compile the kernel with frame pointers" depends on DEBUG_KERNEL && \ (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \ AVR32 || SUPERH || BLACKFIN || MN10300) default y if DEBUG_INFO && UML help If you say Y here the resulting kernel image will be slightly larger and slower, but it might give very useful debugging information on some architectures or if you use external debuggers. If you don't debug the kernel, you can say N. config BOOT_PRINTK_DELAY bool "Delay each boot printk message by N milliseconds" depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY help This build option allows you to read kernel boot messages by inserting a short delay after each one. The delay is specified in milliseconds on the kernel command line, using "boot_delay=N". It is likely that you would also need to use "lpj=M" to preset the "loops per jiffie" value. See a previous boot log for the "lpj" value to use for your system, and then set "lpj=M" before setting "boot_delay=N". NOTE: Using this option may adversely affect SMP systems. I.e., processors other than the first one may not boot up. BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect what it believes to be lockup conditions. config RCU_TORTURE_TEST tristate "torture tests for RCU" depends on DEBUG_KERNEL default n help This option provides a kernel module that runs torture tests on the RCU infrastructure. The kernel module may be built after the fact on the running kernel to be tested, if desired. Say Y here if you want RCU torture tests to be built into the kernel. Say M if you want the RCU torture tests to build as a module. Say N if you are unsure. config RCU_TORTURE_TEST_RUNNABLE bool "torture tests for RCU runnable by default" depends on RCU_TORTURE_TEST = y default n help This option provides a way to build the RCU torture tests directly into the kernel without them starting up at boot time. You can use /proc/sys/kernel/rcutorture_runnable to manually override this setting. This /proc file is available only when the RCU torture tests have been built into the kernel. Say Y here if you want the RCU torture tests to start during boot (you probably don't). Say N here if you want the RCU torture tests to start only after being manually enabled via /proc. config KPROBES_SANITY_TEST bool "Kprobes sanity tests" depends on DEBUG_KERNEL depends on KPROBES default n help This option provides for testing basic kprobes functionality on boot. A sample kprobe, jprobe and kretprobe are inserted and verified for functionality. Say N if you are unsure. config BACKTRACE_SELF_TEST tristate "Self test for the backtrace code" depends on DEBUG_KERNEL default n help This option provides a kernel module that can be used to test the kernel stack backtrace code. This option is not useful for distributions or general kernels, but only for kernel developers working on architecture code. Note that if you want to also test saved backtraces, you will have to enable STACKTRACE as well. Say N if you are unsure. config LKDTM tristate "Linux Kernel Dump Test Tool Module" depends on DEBUG_KERNEL depends on KPROBES depends on BLOCK default n help This module enables testing of the different dumping mechanisms by inducing system failures at predefined crash points. If you don't need it: say N Choose M here to compile this code as a module. The module will be called lkdtm. Documentation on how to use the module can be found in drivers/misc/lkdtm.c config FAULT_INJECTION bool "Fault-injection framework" depends on DEBUG_KERNEL help Provide fault-injection framework. For more details, see Documentation/fault-injection/. config FAILSLAB bool "Fault-injection capability for kmalloc" depends on FAULT_INJECTION help Provide fault-injection capability for kmalloc. config FAIL_PAGE_ALLOC bool "Fault-injection capabilitiy for alloc_pages()" depends on FAULT_INJECTION help Provide fault-injection capability for alloc_pages(). config FAIL_MAKE_REQUEST bool "Fault-injection capability for disk IO" depends on FAULT_INJECTION help Provide fault-injection capability for disk IO. config FAULT_INJECTION_DEBUG_FS bool "Debugfs entries for fault-injection capabilities" depends on FAULT_INJECTION && SYSFS && DEBUG_FS help Enable configuration of fault-injection capabilities via debugfs. config FAULT_INJECTION_STACKTRACE_FILTER bool "stacktrace filter for fault-injection capabilities" depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT depends on !X86_64 select STACKTRACE select FRAME_POINTER if !PPC help Provide stacktrace filter for fault-injection capabilities config LATENCYTOP bool "Latency measuring infrastructure" select FRAME_POINTER if !MIPS && !PPC select KALLSYMS select KALLSYMS_ALL select STACKTRACE select SCHEDSTATS select SCHED_DEBUG depends on HAVE_LATENCYTOP_SUPPORT help Enable this option if you want to use the LatencyTOP tool to find out which userspace is blocking on what kernel operations. config SYSCTL_SYSCALL_CHECK bool "Sysctl checks" depends on SYSCTL_SYSCALL ---help--- sys_sysctl uses binary paths that have been found challenging to properly maintain and use. This enables checks that help you to keep things correct. source kernel/trace/Kconfig config PROVIDE_OHCI1394_DMA_INIT bool "Remote debugging over FireWire early on boot" depends on PCI && X86 help If you want to debug problems which hang or crash the kernel early on boot and the crashing machine has a FireWire port, you can use this feature to remotely access the memory of the crashed machine over FireWire. This employs remote DMA as part of the OHCI1394 specification which is now the standard for FireWire controllers. With remote DMA, you can monitor the printk buffer remotely using firescope and access all memory below 4GB using fireproxy from gdb. Even controlling a kernel debugger is possible using remote DMA. Usage: If ohci1394_dma=early is used as boot parameter, it will initialize all OHCI1394 controllers which are found in the PCI config space. As all changes to the FireWire bus such as enabling and disabling devices cause a bus reset and thereby disable remote DMA for all devices, be sure to have the cable plugged and FireWire enabled on the debugging host before booting the debug target for debugging. This code (~1k) is freed after boot. By then, the firewire stack in charge of the OHCI-1394 controllers should be used instead. See Documentation/debugging-via-ohci1394.txt for more information. config FIREWIRE_OHCI_REMOTE_DMA bool "Remote debugging over FireWire with firewire-ohci" depends on FIREWIRE_OHCI help This option lets you use the FireWire bus for remote debugging with help of the firewire-ohci driver. It enables unfiltered remote DMA in firewire-ohci. See Documentation/debugging-via-ohci1394.txt for more information. If unsure, say N. menuconfig BUILD_DOCSRC bool "Build targets in Documentation/ tree" depends on HEADERS_CHECK help This option attempts to build objects from the source files in the kernel Documentation/ tree. Say N if you are unsure. source "samples/Kconfig" source "lib/Kconfig.kgdb"