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menu "printk and dmesg options" config PRINTK_TIME bool "Show timing information on printks" depends on PRINTK help Selecting this option causes time stamps of the printk() messages to be added to the output of the syslog() system call and at the console. The timestamp is always recorded internally, and exported to /dev/kmsg. This flag just specifies if the timestamp should be included, not that the timestamp is recorded. The behavior is also controlled by the kernel command line parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst config CONSOLE_LOGLEVEL_DEFAULT int "Default console loglevel (1-15)" range 1 15 default "7" help Default loglevel to determine what will be printed on the console. Setting a default here is equivalent to passing in loglevel=<x> in the kernel bootargs. loglevel=<x> continues to override whatever value is specified here as well. Note: This does not affect the log level of un-prefixed printk() usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT option. config MESSAGE_LOGLEVEL_DEFAULT int "Default message log level (1-7)" range 1 7 default "4" help Default log level for printk statements with no specified priority. This was hard-coded to KERN_WARNING since at least 2.6.10 but folks that are auditing their logs closely may want to set it to a lower priority. Note: This does not affect what message level gets printed on the console by default. To change that, use loglevel=<x> in the kernel bootargs, or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value. 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 LOCKUP_DETECTOR to detect what it believes to be lockup conditions. config DYNAMIC_DEBUG bool "Enable dynamic printk() support" default n depends on PRINTK depends on DEBUG_FS help Compiles debug level messages into the kernel, which would not otherwise be available at runtime. These messages can then be enabled/disabled based on various levels of scope - per source file, function, module, format string, and line number. This mechanism implicitly compiles in all pr_debug() and dev_dbg() calls, which enlarges the kernel text size by about 2%. If a source file is compiled with DEBUG flag set, any pr_debug() calls in it are enabled by default, but can be disabled at runtime as below. Note that DEBUG flag is turned on by many CONFIG_*DEBUG* options. Usage: Dynamic debugging is controlled via the 'dynamic_debug/control' file, which is contained in the 'debugfs' filesystem. Thus, the debugfs filesystem must first be mounted before making use of this feature. We refer the control file as: <debugfs>/dynamic_debug/control. This file contains a list of the debug statements that can be enabled. The format for each line of the file is: filename:lineno [module]function flags format filename : source file of the debug statement lineno : line number of the debug statement module : module that contains the debug statement function : function that contains the debug statement flags : '=p' means the line is turned 'on' for printing format : the format used for the debug statement From a live system: nullarbor:~ # cat <debugfs>/dynamic_debug/control # filename:lineno [module]function flags format fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" Example usage: // enable the message at line 1603 of file svcsock.c nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > <debugfs>/dynamic_debug/control // enable all the messages in file svcsock.c nullarbor:~ # echo -n 'file svcsock.c +p' > <debugfs>/dynamic_debug/control // enable all the messages in the NFS server module nullarbor:~ # echo -n 'module nfsd +p' > <debugfs>/dynamic_debug/control // enable all 12 messages in the function svc_process() nullarbor:~ # echo -n 'func svc_process +p' > <debugfs>/dynamic_debug/control // disable all 12 messages in the function svc_process() nullarbor:~ # echo -n 'func svc_process -p' > <debugfs>/dynamic_debug/control See Documentation/admin-guide/dynamic-debug-howto.rst for additional information. endmenu # "printk and dmesg options" menu "Compile-time checks and compiler options" config DEBUG_INFO bool "Compile the kernel with debug info" depends on DEBUG_KERNEL && !COMPILE_TEST 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_INFO_REDUCED bool "Reduce debugging information" depends on DEBUG_INFO help If you say Y here gcc is instructed to generate less debugging information for structure types. This means that tools that need full debugging information (like kgdb or systemtap) won't be happy. But if you merely need debugging information to resolve line numbers there is no loss. Advantage is that build directory object sizes shrink dramatically over a full DEBUG_INFO build and compile times are reduced too. Only works with newer gcc versions. config DEBUG_INFO_SPLIT bool "Produce split debuginfo in .dwo files" depends on DEBUG_INFO && !FRV help Generate debug info into separate .dwo files. This significantly reduces the build directory size for builds with DEBUG_INFO, because it stores the information only once on disk in .dwo files instead of multiple times in object files and executables. In addition the debug information is also compressed. Requires recent gcc (4.7+) and recent gdb/binutils. Any tool that packages or reads debug information would need to know about the .dwo files and include them. Incompatible with older versions of ccache. config DEBUG_INFO_DWARF4 bool "Generate dwarf4 debuginfo" depends on DEBUG_INFO help Generate dwarf4 debug info. This requires recent versions of gcc and gdb. It makes the debug information larger. But it significantly improves the success of resolving variables in gdb on optimized code. config GDB_SCRIPTS bool "Provide GDB scripts for kernel debugging" depends on DEBUG_INFO help This creates the required links to GDB helper scripts in the build directory. If you load vmlinux into gdb, the helper scripts will be automatically imported by gdb as well, and additional functions are available to analyze a Linux kernel instance. See Documentation/dev-tools/gdb-kernel-debugging.rst for further details. 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 3072 if KASAN_EXTRA default 2048 if GCC_PLUGIN_LATENT_ENTROPY default 1280 if (!64BIT && PARISC) default 1024 if (!64BIT && !PARISC) 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 STRIP_ASM_SYMS bool "Strip assembler-generated symbols during link" default n help Strip internal assembler-generated symbols during a link (symbols that look like '.Lxxx') so they don't pollute the output of get_wchan() and suchlike. config READABLE_ASM bool "Generate readable assembler code" depends on DEBUG_KERNEL help Disable some compiler optimizations that tend to generate human unreadable assembler output. This may make the kernel slightly slower, but it helps to keep kernel developers who have to stare a lot at assembler listings sane. 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 PAGE_OWNER bool "Track page owner" depends on DEBUG_KERNEL && STACKTRACE_SUPPORT select DEBUG_FS select STACKTRACE select STACKDEPOT select PAGE_EXTENSION help This keeps track of what call chain is the owner of a page, may help to find bare alloc_page(s) leaks. Even if you include this feature on your build, it is disabled in default. You should pass "page_owner=on" to boot parameter in order to enable it. Eats a fair amount of memory if enabled. See tools/vm/page_owner_sort.c for user-space helper. If unsure, say N. config DEBUG_FS bool "Debug Filesystem" 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/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" help The section mismatch analysis checks if there are illegal references from one section to another section. During linktime or runtime, some sections are dropped; any use of code/data previously in these sections would most likely result in an oops. In the code, functions and variables are annotated with __init,, etc. (see the full list in include/linux/init.h), which results in the code/data being placed in specific sections. The section mismatch analysis is always performed after a full kernel build, and enabling this option causes the following additional steps to occur: - Add the option -fno-inline-functions-called-once to gcc commands. When inlining a function annotated with __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 it does result in a larger kernel). - Run the section mismatch analysis for each module/built-in.o file. When we run the section mismatch analysis on vmlinux.o, we lose valuable information about where the mismatch was introduced. Running the analysis for each module/built-in.o file tells where the mismatch happens much closer to the source. The drawback is that the same mismatch is reported at least twice. - Enable verbose reporting from modpost in order to help resolve the section mismatches that are reported. config SECTION_MISMATCH_WARN_ONLY bool "Make section mismatch errors non-fatal" default y help If you say N here, the build process will fail if there are any section mismatch, instead of just throwing warnings. If unsure, say Y. # # Select this config option from the architecture Kconfig, if it # is preferred to always offer frame pointers as a config # option on the architecture (regardless of KERNEL_DEBUG): # config ARCH_WANT_FRAME_POINTERS bool help config FRAME_POINTER bool "Compile the kernel with frame pointers" depends on DEBUG_KERNEL && \ (CRIS || M68K || FRV || UML || \ SUPERH || BLACKFIN || MN10300 || METAG) || \ ARCH_WANT_FRAME_POINTERS default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS help If you say Y here the resulting kernel image will be slightly larger and slower, but it gives very useful debugging information in case of kernel bugs. (precise oopses/stacktraces/warnings) config STACK_VALIDATION bool "Compile-time stack metadata validation" depends on HAVE_STACK_VALIDATION default n help Add compile-time checks to validate stack metadata, including frame pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure that runtime stack traces are more reliable. This is also a prerequisite for generation of ORC unwind data, which is needed for CONFIG_UNWINDER_ORC. For more information, see tools/objtool/Documentation/stack-validation.txt. config DEBUG_FORCE_WEAK_PER_CPU bool "Force weak per-cpu definitions" depends on DEBUG_KERNEL help s390 and alpha require percpu variables in modules to be defined weak to work around addressing range issue which puts the following two restrictions on percpu variable definitions. 1. percpu symbols must be unique whether static or not 2. percpu variables can't be defined inside a function To ensure that generic code follows the above rules, this option forces all percpu variables to be defined as weak. endmenu # "Compiler options" 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/admin-guide/sysrq.rst>. Don't say Y unless you really know what this hack does. config MAGIC_SYSRQ_DEFAULT_ENABLE hex "Enable magic SysRq key functions by default" depends on MAGIC_SYSRQ default 0x1 help Specifies which SysRq key functions are enabled by default. This may be set to 1 or 0 to enable or disable them all, or to a bitmask as described in Documentation/admin-guide/sysrq.rst. config MAGIC_SYSRQ_SERIAL bool "Enable magic SysRq key over serial" depends on MAGIC_SYSRQ default y help Many embedded boards have a disconnected TTL level serial which can generate some garbage that can lead to spurious false sysrq detects. This option allows you to decide whether you want to enable the magic SysRq key. config DEBUG_KERNEL bool "Kernel debugging" help Say Y here if you are developing drivers or trying to debug and identify kernel problems. menu "Memory Debugging" source mm/Kconfig.debug 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_OBJECTS_WORK bool "Debug work objects" depends on DEBUG_OBJECTS help If you say Y here, additional code will be inserted into the work queue routines to track the life time of work objects and validate the work operations. config DEBUG_OBJECTS_RCU_HEAD bool "Debug RCU callbacks objects" depends on DEBUG_OBJECTS help Enable this to turn on debugging of RCU list heads (call_rcu() usage). config DEBUG_OBJECTS_PERCPU_COUNTER bool "Debug percpu counter objects" depends on DEBUG_OBJECTS help If you say Y here, additional code will be inserted into the percpu counter routines to track the life time of percpu counter objects and validate the percpu counter operations. config DEBUG_OBJECTS_ENABLE_DEFAULT int "debug_objects bootup default value (0-1)" range 0 1 default "1" depends on DEBUG_OBJECTS help Debug objects boot parameter default value 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 && 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 HAVE_DEBUG_KMEMLEAK bool config DEBUG_KMEMLEAK bool "Kernel memory leak detector" depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK select DEBUG_FS select STACKTRACE if STACKTRACE_SUPPORT select KALLSYMS select CRC32 help Say Y here if you want to enable the memory leak detector. The memory allocation/freeing is traced in a way similar to the Boehm's conservative garbage collector, the difference being that the orphan objects are not freed but only shown in /sys/kernel/debug/kmemleak. Enabling this feature will introduce an overhead to memory allocations. See Documentation/dev-tools/kmemleak.rst for more details. Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances of finding leaks due to the slab objects poisoning. In order to access the kmemleak file, debugfs needs to be mounted (usually at /sys/kernel/debug). config DEBUG_KMEMLEAK_EARLY_LOG_SIZE int "Maximum kmemleak early log entries" depends on DEBUG_KMEMLEAK range 200 40000 default 16000 help Kmemleak must track all the memory allocations to avoid reporting false positives. Since memory may be allocated or freed before kmemleak is initialised, an early log buffer is used to store these actions. If kmemleak reports "early log buffer exceeded", please increase this value. config DEBUG_KMEMLEAK_TEST tristate "Simple test for the kernel memory leak detector" depends on DEBUG_KMEMLEAK && m help This option enables a module that explicitly leaks memory. If unsure, say N. config DEBUG_KMEMLEAK_DEFAULT_OFF bool "Default kmemleak to off" depends on DEBUG_KMEMLEAK help Say Y here to disable kmemleak by default. It can then be enabled on the command line via kmemleak=on. config DEBUG_STACK_USAGE bool "Stack utilization instrumentation" depends on DEBUG_KERNEL && !IA64 help Enables the display of the minimum amount of free stack which each task has ever had available in the sysrq-T and sysrq-P debug output. This option will slow down process creation somewhat. 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_VM_VMACACHE bool "Debug VMA caching" depends on DEBUG_VM help Enable this to turn on VMA caching debug information. Doing so can cause significant overhead, so only enable it in non-production environments. If unsure, say N. config DEBUG_VM_RB bool "Debug VM red-black trees" depends on DEBUG_VM help Enable VM red-black tree debugging information and extra validations. If unsure, say N. config DEBUG_VM_PGFLAGS bool "Debug page-flags operations" depends on DEBUG_VM help Enables extra validation on page flags operations. If unsure, say N. config ARCH_HAS_DEBUG_VIRTUAL bool config DEBUG_VIRTUAL bool "Debug VM translations" depends on DEBUG_KERNEL && ARCH_HAS_DEBUG_VIRTUAL help Enable some costly sanity checks in virtual to page code. This can catch mistakes with virt_to_page() and friends. If unsure, say N. config DEBUG_NOMMU_REGIONS bool "Debug the global anon/private NOMMU mapping region tree" depends on DEBUG_KERNEL && !MMU help This option causes the global tree of anonymous and private mapping regions to be regularly checked for invalid topology. config DEBUG_MEMORY_INIT bool "Debug memory initialisation" if EXPERT default !EXPERT 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 MEMORY_NOTIFIER_ERROR_INJECT tristate "Memory hotplug notifier error injection module" depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION help This option provides the ability to inject artificial errors to memory hotplug notifier chain callbacks. It is controlled through debugfs interface under /sys/kernel/debug/notifier-error-inject/memory If the notifier call chain should be failed with some events notified, write the error code to "actions/<notifier event>/error". Example: Inject memory hotplug offline error (-12 == -ENOMEM) # cd /sys/kernel/debug/notifier-error-inject/memory # echo -12 > actions/MEM_GOING_OFFLINE/error # echo offline > /sys/devices/system/memory/memoryXXX/state bash: echo: write error: Cannot allocate memory To compile this code as a module, choose M here: the module will be called memory-notifier-error-inject. If unsure, say N. config DEBUG_PER_CPU_MAPS bool "Debug access to per_cpu maps" depends on DEBUG_KERNEL depends on SMP help Say Y to verify that the per_cpu map being accessed has been set up. This adds a fair amount of code to kernel memory and decreases performance. Say N if unsure. config DEBUG_HIGHMEM bool "Highmem debugging" depends on DEBUG_KERNEL && HIGHMEM help This option enables additional error checking for high memory systems. Disable for production systems. config HAVE_DEBUG_STACKOVERFLOW bool config DEBUG_STACKOVERFLOW bool "Check for stack overflows" depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW ---help--- Say Y here if you want to check for overflows of kernel, IRQ and exception stacks (if your architecture uses them). This option will show detailed messages if free stack space drops below a certain limit. These kinds of bugs usually occur when call-chains in the kernel get too deep, especially when interrupts are involved. Use this in cases where you see apparently random memory corruption, especially if it appears in 'struct thread_info' If in doubt, say "N". source "lib/Kconfig.kasan" endmenu # "Memory Debugging" config ARCH_HAS_KCOV bool help KCOV does not have any arch-specific code, but currently it is enabled only for x86_64. KCOV requires testing on other archs, and most likely disabling of instrumentation for some early boot code. config KCOV bool "Code coverage for fuzzing" depends on ARCH_HAS_KCOV select DEBUG_FS select GCC_PLUGINS if !COMPILE_TEST select GCC_PLUGIN_SANCOV if !COMPILE_TEST help KCOV exposes kernel code coverage information in a form suitable for coverage-guided fuzzing (randomized testing). If RANDOMIZE_BASE is enabled, PC values will not be stable across different machines and across reboots. If you need stable PC values, disable RANDOMIZE_BASE. For more details, see Documentation/dev-tools/kcov.rst. config KCOV_ENABLE_COMPARISONS bool "Enable comparison operands collection by KCOV" depends on KCOV default n help KCOV also exposes operands of every comparison in the instrumented code along with operand sizes and PCs of the comparison instructions. These operands can be used by fuzzing engines to improve the quality of fuzzing coverage. config KCOV_INSTRUMENT_ALL bool "Instrument all code by default" depends on KCOV default y if KCOV help If you are doing generic system call fuzzing (like e.g. syzkaller), then you will want to instrument the whole kernel and you should say y here. If you are doing more targeted fuzzing (like e.g. filesystem fuzzing with AFL) then you will want to enable coverage for more specific subsets of files, and should say n here. config DEBUG_SHIRQ bool "Debug shared IRQ handlers" depends on DEBUG_KERNEL 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. menu "Debug Lockups and Hangs" config LOCKUP_DETECTOR bool config SOFTLOCKUP_DETECTOR bool "Detect Soft Lockups" depends on DEBUG_KERNEL && !S390 select LOCKUP_DETECTOR help Say Y here to enable the kernel to act as a watchdog to detect soft lockups. Softlockups are bugs that cause the kernel to loop in kernel mode for more than 20 seconds, without giving other tasks a chance to run. The current stack trace is displayed upon detection and the system will stay locked up. config HARDLOCKUP_DETECTOR_PERF bool select SOFTLOCKUP_DETECTOR # # Enables a timestamp based low pass filter to compensate for perf based # hard lockup detection which runs too fast due to turbo modes. # config HARDLOCKUP_CHECK_TIMESTAMP bool # # arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard # lockup detector rather than the perf based detector. # config HARDLOCKUP_DETECTOR bool "Detect Hard Lockups" depends on DEBUG_KERNEL && !S390 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_ARCH select LOCKUP_DETECTOR select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF select HARDLOCKUP_DETECTOR_ARCH if HAVE_HARDLOCKUP_DETECTOR_ARCH help Say Y here to enable the kernel to act as a watchdog to detect hard lockups. Hardlockups are bugs that cause the CPU to loop in kernel mode for more than 10 seconds, without letting other interrupts have a chance to run. The current stack trace is displayed upon detection and the system will stay locked up. config BOOTPARAM_HARDLOCKUP_PANIC bool "Panic (Reboot) On Hard Lockups" depends on HARDLOCKUP_DETECTOR help Say Y here to enable the kernel to panic on "hard lockups", which are bugs that cause the kernel to loop in kernel mode with interrupts disabled for more than 10 seconds (configurable using the watchdog_thresh sysctl). Say N if unsure. config BOOTPARAM_HARDLOCKUP_PANIC_VALUE int depends on HARDLOCKUP_DETECTOR range 0 1 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC default 1 if BOOTPARAM_HARDLOCKUP_PANIC config BOOTPARAM_SOFTLOCKUP_PANIC bool "Panic (Reboot) On Soft Lockups" depends on SOFTLOCKUP_DETECTOR 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 20 seconds (configurable using the watchdog_thresh sysctl), 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 SOFTLOCKUP_DETECTOR range 0 1 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC default 1 if BOOTPARAM_SOFTLOCKUP_PANIC config DETECT_HUNG_TASK bool "Detect Hung Tasks" depends on DEBUG_KERNEL default SOFTLOCKUP_DETECTOR help Say Y here to enable the kernel to detect "hung tasks", which are bugs that cause the task to be stuck in uninterruptible "D" state indefinitely. When a hung task is detected, the kernel will print the current stack trace (which you should report), but the task will stay in uninterruptible state. If lockdep is enabled then all held locks will also be reported. This feature has negligible overhead. config DEFAULT_HUNG_TASK_TIMEOUT int "Default timeout for hung task detection (in seconds)" depends on DETECT_HUNG_TASK default 120 help This option controls the default timeout (in seconds) used to determine when a task has become non-responsive and should be considered hung. It can be adjusted at runtime via the kernel.hung_task_timeout_secs sysctl or by writing a value to /proc/sys/kernel/hung_task_timeout_secs. A timeout of 0 disables the check. The default is two minutes. Keeping the default should be fine in most cases. config BOOTPARAM_HUNG_TASK_PANIC bool "Panic (Reboot) On Hung Tasks" depends on DETECT_HUNG_TASK help Say Y here to enable the kernel to panic on "hung tasks", which are bugs that cause the kernel to leave a task stuck in uninterruptible "D" state. The panic can be used in combination with panic_timeout, to cause the system to reboot automatically after a hung task has been detected. This feature is useful for high-availability systems that have uptime guarantees and where a hung tasks must be resolved ASAP. Say N if unsure. config BOOTPARAM_HUNG_TASK_PANIC_VALUE int depends on DETECT_HUNG_TASK range 0 1 default 0 if !BOOTPARAM_HUNG_TASK_PANIC default 1 if BOOTPARAM_HUNG_TASK_PANIC config WQ_WATCHDOG bool "Detect Workqueue Stalls" depends on DEBUG_KERNEL help Say Y here to enable stall detection on workqueues. If a worker pool doesn't make forward progress on a pending work item for over a given amount of time, 30s by default, a warning message is printed along with dump of workqueue state. This can be configured through kernel parameter "workqueue.watchdog_thresh" and its sysfs counterpart. endmenu # "Debug lockups and hangs" config PANIC_ON_OOPS bool "Panic on Oops" help Say Y here to enable the kernel to panic when it oopses. This has the same effect as setting oops=panic on the kernel command line. This feature is useful to ensure that the kernel does not do anything erroneous after an oops which could result in data corruption or other issues. Say N if unsure. config PANIC_ON_OOPS_VALUE int range 0 1 default 0 if !PANIC_ON_OOPS default 1 if PANIC_ON_OOPS config PANIC_TIMEOUT int "panic timeout" default 0 help Set the timeout value (in seconds) until a reboot occurs when the the kernel panics. If n = 0, then we wait forever. A timeout value n > 0 will wait n seconds before rebooting, while a timeout value n < 0 will reboot immediately. 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 SCHED_INFO bool default n config SCHEDSTATS bool "Collect scheduler statistics" depends on DEBUG_KERNEL && PROC_FS select SCHED_INFO 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 SCHED_STACK_END_CHECK bool "Detect stack corruption on calls to schedule()" depends on DEBUG_KERNEL default n help This option checks for a stack overrun on calls to schedule(). If the stack end location is found to be over written always panic as the content of the corrupted region can no longer be trusted. This is to ensure no erroneous behaviour occurs which could result in data corruption or a sporadic crash at a later stage once the region is examined. The runtime overhead introduced is minimal. config DEBUG_TIMEKEEPING bool "Enable extra timekeeping sanity checking" help This option will enable additional timekeeping sanity checks which may be helpful when diagnosing issues where timekeeping problems are suspected. This may include checks in the timekeeping hotpaths, so this option may have a (very small) performance impact to some workloads. If unsure, say N. config DEBUG_PREEMPT bool "Debug preemptible kernel" depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 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. menu "Lock Debugging (spinlocks, mutexes, etc...)" 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_SPINLOCK bool "Spinlock and rw-lock debugging: basic checks" depends on DEBUG_KERNEL select UNINLINE_SPIN_UNLOCK 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_WW_MUTEX_SLOWPATH bool "Wait/wound mutex debugging: Slowpath testing" depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select DEBUG_LOCK_ALLOC select DEBUG_SPINLOCK select DEBUG_MUTEXES help This feature enables slowpath testing for w/w mutex users by injecting additional -EDEADLK wound/backoff cases. Together with the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this will test all possible w/w mutex interface abuse with the exception of simply not acquiring all the required locks. Note that this feature can introduce significant overhead, so it really should not be enabled in a production or distro kernel, even a debug kernel. If you are a driver writer, enable it. If you are a distro, do not. 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 DEBUG_RT_MUTEXES if RT_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_RT_MUTEXES if RT_MUTEXES select DEBUG_LOCK_ALLOC select TRACE_IRQFLAGS 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/locking/lockdep-design.txt. config LOCKDEP bool depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT select STACKTRACE select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86 select KALLSYMS select KALLSYMS_ALL config LOCKDEP_SMALL bool 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_RT_MUTEXES if RT_MUTEXES select DEBUG_LOCK_ALLOC default n help This feature enables tracking lock contention points For more details, see Documentation/locking/lockstat.txt This also enables lock events required by "perf lock", subcommand of perf. If you want to use "perf lock", you also need to turn on CONFIG_EVENT_TRACING. CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. (CONFIG_LOCKDEP defines "acquire" and "release" events.) 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 DEBUG_ATOMIC_SLEEP bool "Sleep inside atomic section checking" select PREEMPT_COUNT depends on DEBUG_KERNEL help If you say Y here, various routines which may sleep will become very noisy if they are called inside atomic sections: when a spinlock is held, inside an rcu read side critical section, inside preempt disabled sections, inside an interrupt, etc... 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 LOCK_TORTURE_TEST tristate "torture tests for locking" depends on DEBUG_KERNEL select TORTURE_TEST default n help This option provides a kernel module that runs torture tests on kernel locking primitives. The kernel module may be built after the fact on the running kernel to be tested, if desired. Say Y here if you want kernel locking-primitive torture tests to be built into the kernel. Say M if you want these torture tests to build as a module. Say N if you are unsure. config WW_MUTEX_SELFTEST tristate "Wait/wound mutex selftests" help This option provides a kernel module that runs tests on the on the struct ww_mutex locking API. It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction with this test harness. Say M if you want these self tests to build as a module. Say N if you are unsure. endmenu # lock debugging config TRACE_IRQFLAGS bool help Enables hooks to interrupt enabling and disabling for either tracing or lock debugging. config STACKTRACE bool "Stack backtrace support" depends on STACKTRACE_SUPPORT help This option causes the kernel to create a /proc/pid/stack for every process, showing its current stack trace. It is also used by various kernel debugging features that require stack trace generation. config WARN_ALL_UNSEEDED_RANDOM bool "Warn for all uses of unseeded randomness" default n help Some parts of the kernel contain bugs relating to their use of cryptographically secure random numbers before it's actually possible to generate those numbers securely. This setting ensures that these flaws don't go unnoticed, by enabling a message, should this ever occur. This will allow people with obscure setups to know when things are going wrong, so that they might contact developers about fixing it. Unfortunately, on some models of some architectures getting a fully seeded CRNG is extremely difficult, and so this can result in dmesg getting spammed for a surprisingly long time. This is really bad from a security perspective, and so architecture maintainers really need to do what they can to get the CRNG seeded sooner after the system is booted. However, since users can not do anything actionble to address this, by default the kernel will issue only a single warning for the first use of unseeded randomness. Say Y here if you want to receive warnings for all uses of unseeded randomness. This will be of use primarily for those developers interersted in improving the security of Linux kernels running on their architecture (or subarchitecture). 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_KOBJECT_RELEASE bool "kobject release debugging" depends on DEBUG_OBJECTS_TIMERS help kobjects are reference counted objects. This means that their last reference count put is not predictable, and the kobject can live on past the point at which a driver decides to drop it's initial reference to the kobject gained on allocation. An example of this would be a struct device which has just been unregistered. However, some buggy drivers assume that after such an operation, the memory backing the kobject can be immediately freed. This goes completely against the principles of a refcounted object. If you say Y here, the kernel will delay the release of kobjects on the last reference count to improve the visibility of this kind of kobject release bug. config HAVE_DEBUG_BUGVERBOSE bool config DEBUG_BUGVERBOSE bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) default y 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_LIST bool "Debug linked list manipulation" depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION help Enable this to turn on extended checks in the linked-list walking routines. If unsure, say N. config DEBUG_PI_LIST bool "Debug priority linked list manipulation" depends on DEBUG_KERNEL help Enable this to turn on extended checks in the priority-ordered linked-list (plist) walking routines. This checks the entire list multiple times during each manipulation. 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 DEBUG_NOTIFIERS bool "Debug notifier call chains" depends on DEBUG_KERNEL help Enable this to turn on sanity checking for notifier call chains. This is most useful for kernel developers to make sure that modules properly unregister themselves from notifier chains. This is a relatively cheap check but if you care about maximum performance, say N. config DEBUG_CREDENTIALS bool "Debug credential management" depends on DEBUG_KERNEL help Enable this to turn on some debug checking for credential management. The additional code keeps track of the number of pointers from task_structs to any given cred struct, and checks to see that this number never exceeds the usage count of the cred struct. Furthermore, if SELinux is enabled, this also checks that the security pointer in the cred struct is never seen to be invalid. If unsure, say N. source "kernel/rcu/Kconfig.debug" config DEBUG_WQ_FORCE_RR_CPU bool "Force round-robin CPU selection for unbound work items" depends on DEBUG_KERNEL default n help Workqueue used to implicitly guarantee that work items queued without explicit CPU specified are put on the local CPU. This guarantee is no longer true and while local CPU is still preferred work items may be put on foreign CPUs. Kernel parameter "workqueue.debug_force_rr_cpu" is added to force round-robin CPU selection to flush out usages which depend on the now broken guarantee. This config option enables the debug feature by default. When enabled, memory and cache locality will be impacted. config DEBUG_BLOCK_EXT_DEVT bool "Force extended block device numbers and spread them" depends on DEBUG_KERNEL depends on BLOCK default n help BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT YOU ARE DOING. Distros, please enable this and fix whatever is broken. Conventionally, block device numbers are allocated from predetermined contiguous area. However, extended block area may introduce non-contiguous block device numbers. This option forces most block device numbers to be allocated from the extended space and spreads them to discover kernel or userland code paths which assume predetermined contiguous device number allocation. Note that turning on this debug option shuffles all the device numbers for all IDE and SCSI devices including libata ones, so root partition specified using device number directly (via rdev or root=MAJ:MIN) won't work anymore. Textual device names (root=/dev/sdXn) will continue to work. Say N if you are unsure. config CPU_HOTPLUG_STATE_CONTROL bool "Enable CPU hotplug state control" depends on DEBUG_KERNEL depends on HOTPLUG_CPU default n help Allows to write steps between "offline" and "online" to the CPUs sysfs target file so states can be stepped granular. This is a debug option for now as the hotplug machinery cannot be stopped and restarted at arbitrary points yet. Say N if your are unsure. config NOTIFIER_ERROR_INJECTION tristate "Notifier error injection" depends on DEBUG_KERNEL select DEBUG_FS help This option provides the ability to inject artificial errors to specified notifier chain callbacks. It is useful to test the error handling of notifier call chain failures. Say N if unsure. config PM_NOTIFIER_ERROR_INJECT tristate "PM notifier error injection module" depends on PM && NOTIFIER_ERROR_INJECTION default m if PM_DEBUG help This option provides the ability to inject artificial errors to PM notifier chain callbacks. It is controlled through debugfs interface /sys/kernel/debug/notifier-error-inject/pm If the notifier call chain should be failed with some events notified, write the error code to "actions/<notifier event>/error". Example: Inject PM suspend error (-12 = -ENOMEM) # cd /sys/kernel/debug/notifier-error-inject/pm/ # echo -12 > actions/PM_SUSPEND_PREPARE/error # echo mem > /sys/power/state bash: echo: write error: Cannot allocate memory To compile this code as a module, choose M here: the module will be called pm-notifier-error-inject. If unsure, say N. config OF_RECONFIG_NOTIFIER_ERROR_INJECT tristate "OF reconfig notifier error injection module" depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION help This option provides the ability to inject artificial errors to OF reconfig notifier chain callbacks. It is controlled through debugfs interface under /sys/kernel/debug/notifier-error-inject/OF-reconfig/ If the notifier call chain should be failed with some events notified, write the error code to "actions/<notifier event>/error". To compile this code as a module, choose M here: the module will be called of-reconfig-notifier-error-inject. If unsure, say N. config NETDEV_NOTIFIER_ERROR_INJECT tristate "Netdev notifier error injection module" depends on NET && NOTIFIER_ERROR_INJECTION help This option provides the ability to inject artificial errors to netdevice notifier chain callbacks. It is controlled through debugfs interface /sys/kernel/debug/notifier-error-inject/netdev If the notifier call chain should be failed with some events notified, write the error code to "actions/<notifier event>/error". Example: Inject netdevice mtu change error (-22 = -EINVAL) # cd /sys/kernel/debug/notifier-error-inject/netdev # echo -22 > actions/NETDEV_CHANGEMTU/error # ip link set eth0 mtu 1024 RTNETLINK answers: Invalid argument To compile this code as a module, choose M here: the module will be called netdev-notifier-error-inject. If unsure, say N. 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 depends on SLAB || SLUB 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 && BLOCK help Provide fault-injection capability for disk IO. config FAIL_IO_TIMEOUT bool "Fault-injection capability for faking disk interrupts" depends on FAULT_INJECTION && BLOCK help Provide fault-injection capability on end IO handling. This will make the block layer "forget" an interrupt as configured, thus exercising the error handling. Only works with drivers that use the generic timeout handling, for others it wont do anything. config FAIL_MMC_REQUEST bool "Fault-injection capability for MMC IO" depends on FAULT_INJECTION_DEBUG_FS && MMC help Provide fault-injection capability for MMC IO. This will make the mmc core return data errors. This is useful to test the error handling in the mmc block device and to test how the mmc host driver handles retries from the block device. config FAIL_FUTEX bool "Fault-injection capability for futexes" select DEBUG_FS depends on FAULT_INJECTION && FUTEX help Provide fault-injection capability for futexes. 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 !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE && !X86 help Provide stacktrace filter for fault-injection capabilities config LATENCYTOP bool "Latency measuring infrastructure" depends on DEBUG_KERNEL depends on STACKTRACE_SUPPORT depends on PROC_FS select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86 select KALLSYMS select KALLSYMS_ALL select STACKTRACE select SCHEDSTATS select SCHED_DEBUG help Enable this option if you want to use the LatencyTOP tool to find out which userspace is blocking on what kernel operations. 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 DMA_API_DEBUG bool "Enable debugging of DMA-API usage" depends on HAVE_DMA_API_DEBUG help Enable this option to debug the use of the DMA API by device drivers. With this option you will be able to detect common bugs in device drivers like double-freeing of DMA mappings or freeing mappings that were never allocated. This also attempts to catch cases where a page owned by DMA is accessed by the cpu in a way that could cause data corruption. For example, this enables cow_user_page() to check that the source page is not undergoing DMA. This option causes a performance degradation. Use only if you want to debug device drivers and dma interactions. If unsure, say N. menu "Runtime Testing" config LKDTM tristate "Linux Kernel Dump Test Tool Module" depends on DEBUG_FS 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 Documentation/fault-injection/provoke-crashes.txt config TEST_LIST_SORT tristate "Linked list sorting test" depends on DEBUG_KERNEL || m help Enable this to turn on 'list_sort()' function test. This test is executed only once during system boot (so affects only boot time), or at module load time. If unsure, say N. config TEST_SORT tristate "Array-based sort test" depends on DEBUG_KERNEL || m help This option enables the self-test function of 'sort()' at boot, or at module load time. If unsure, say N. 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 RBTREE_TEST tristate "Red-Black tree test" depends on DEBUG_KERNEL help A benchmark measuring the performance of the rbtree library. Also includes rbtree invariant checks. config INTERVAL_TREE_TEST tristate "Interval tree test" depends on DEBUG_KERNEL select INTERVAL_TREE help A benchmark measuring the performance of the interval tree library config PERCPU_TEST tristate "Per cpu operations test" depends on m && DEBUG_KERNEL help Enable this option to build test module which validates per-cpu operations. If unsure, say N. config ATOMIC64_SELFTEST tristate "Perform an atomic64_t self-test" help Enable this option to test the atomic64_t functions at boot or at module load time. If unsure, say N. config ASYNC_RAID6_TEST tristate "Self test for hardware accelerated raid6 recovery" depends on ASYNC_RAID6_RECOV select ASYNC_MEMCPY ---help--- This is a one-shot self test that permutes through the recovery of all the possible two disk failure scenarios for a N-disk array. Recovery is performed with the asynchronous raid6 recovery routines, and will optionally use an offload engine if one is available. If unsure, say N. config TEST_HEXDUMP tristate "Test functions located in the hexdump module at runtime" config TEST_STRING_HELPERS tristate "Test functions located in the string_helpers module at runtime" config TEST_KSTRTOX tristate "Test kstrto*() family of functions at runtime" config TEST_PRINTF tristate "Test printf() family of functions at runtime" config TEST_BITMAP tristate "Test bitmap_*() family of functions at runtime" default n help Enable this option to test the bitmap functions at boot. If unsure, say N. config TEST_UUID tristate "Test functions located in the uuid module at runtime" config TEST_RHASHTABLE tristate "Perform selftest on resizable hash table" default n help Enable this option to test the rhashtable functions at boot. If unsure, say N. config TEST_HASH tristate "Perform selftest on hash functions" default n help Enable this option to test the kernel's integer (<linux/hash.h>), string (<linux/stringhash.h>), and siphash (<linux/siphash.h>) hash functions on boot (or module load). This is intended to help people writing architecture-specific optimized versions. If unsure, say N. config TEST_PARMAN tristate "Perform selftest on priority array manager" default n depends on PARMAN help Enable this option to test priority array manager on boot (or module load). If unsure, say N. config TEST_LKM tristate "Test module loading with 'hello world' module" default n depends on m help This builds the "test_module" module that emits "Hello, world" on printk when loaded. It is designed to be used for basic evaluation of the module loading subsystem (for example when validating module verification). It lacks any extra dependencies, and will not normally be loaded by the system unless explicitly requested by name. If unsure, say N. config TEST_USER_COPY tristate "Test user/kernel boundary protections" default n depends on m help This builds the "test_user_copy" module that runs sanity checks on the copy_to/from_user infrastructure, making sure basic user/kernel boundary testing is working. If it fails to load, a regression has been detected in the user/kernel memory boundary protections. If unsure, say N. config TEST_BPF tristate "Test BPF filter functionality" default n depends on m && NET help This builds the "test_bpf" module that runs various test vectors against the BPF interpreter or BPF JIT compiler depending on the current setting. This is in particular useful for BPF JIT compiler development, but also to run regression tests against changes in the interpreter code. It also enables test stubs for eBPF maps and verifier used by user space verifier testsuite. If unsure, say N. config TEST_FIND_BIT tristate "Test find_bit functions" default n help This builds the "test_find_bit" module that measure find_*_bit() functions performance. If unsure, say N. config TEST_FIRMWARE tristate "Test firmware loading via userspace interface" default n depends on FW_LOADER help This builds the "test_firmware" module that creates a userspace interface for testing firmware loading. This can be used to control the triggering of firmware loading without needing an actual firmware-using device. The contents can be rechecked by userspace. If unsure, say N. config TEST_SYSCTL tristate "sysctl test driver" default n depends on PROC_SYSCTL help This builds the "test_sysctl" module. This driver enables to test the proc sysctl interfaces available to drivers safely without affecting production knobs which might alter system functionality. If unsure, say N. config TEST_UDELAY tristate "udelay test driver" default n help This builds the "udelay_test" module that helps to make sure that udelay() is working properly. If unsure, say N. config TEST_STATIC_KEYS tristate "Test static keys" default n depends on m help Test the static key interfaces. If unsure, say N. config TEST_KMOD tristate "kmod stress tester" default n depends on m depends on BLOCK && (64BIT || LBDAF) # for XFS, BTRFS depends on NETDEVICES && NET_CORE && INET # for TUN depends on BLOCK select TEST_LKM select XFS_FS select TUN select BTRFS_FS help Test the kernel's module loading mechanism: kmod. kmod implements support to load modules using the Linux kernel's usermode helper. This test provides a series of tests against kmod. Although technically you can either build test_kmod as a module or into the kernel we disallow building it into the kernel since it stress tests request_module() and this will very likely cause some issues by taking over precious threads available from other module load requests, ultimately this could be fatal. To run tests run: tools/testing/selftests/kmod/kmod.sh --help If unsure, say N. config TEST_DEBUG_VIRTUAL tristate "Test CONFIG_DEBUG_VIRTUAL feature" depends on DEBUG_VIRTUAL help Test the kernel's ability to detect incorrect calls to virt_to_phys() done against the non-linear part of the kernel's virtual address map. If unsure, say N. endmenu # runtime tests config MEMTEST bool "Memtest" depends on HAVE_MEMBLOCK ---help--- This option adds a kernel parameter 'memtest', which allows memtest to be set. memtest=0, mean disabled; -- default memtest=1, mean do 1 test pattern; ... memtest=17, mean do 17 test patterns. If you are unsure how to answer this question, answer N. config BUG_ON_DATA_CORRUPTION bool "Trigger a BUG when data corruption is detected" select DEBUG_LIST help Select this option if the kernel should BUG when it encounters data corruption in kernel memory structures when they get checked for validity. If unsure, say N. source "samples/Kconfig" source "lib/Kconfig.kgdb" source "lib/Kconfig.ubsan" config ARCH_HAS_DEVMEM_IS_ALLOWED bool config STRICT_DEVMEM bool "Filter access to /dev/mem" depends on MMU && DEVMEM depends on ARCH_HAS_DEVMEM_IS_ALLOWED default y if TILE || PPC ---help--- If this option is disabled, you allow userspace (root) access to all of memory, including kernel and userspace memory. Accidental access to this is obviously disastrous, but specific access can be used by people debugging the kernel. Note that with PAT support enabled, even in this case there are restrictions on /dev/mem use due to the cache aliasing requirements. If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem file only allows userspace access to PCI space and the BIOS code and data regions. This is sufficient for dosemu and X and all common users of /dev/mem. If in doubt, say Y. config IO_STRICT_DEVMEM bool "Filter I/O access to /dev/mem" depends on STRICT_DEVMEM ---help--- If this option is disabled, you allow userspace (root) access to all io-memory regardless of whether a driver is actively using that range. Accidental access to this is obviously disastrous, but specific access can be used by people debugging kernel drivers. If this option is switched on, the /dev/mem file only allows userspace access to *idle* io-memory ranges (see /proc/iomem) This may break traditional users of /dev/mem (dosemu, legacy X, etc...) if the driver using a given range cannot be disabled. If in doubt, say Y.
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