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# SPDX-License-Identifier: GPL-2.0-only menu "Kernel hacking" 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 PRINTK_CALLER bool "Show caller information on printks" depends on PRINTK help Selecting this option causes printk() to add a caller "thread id" (if in task context) or a caller "processor id" (if not in task context) to every message. This option is intended for environments where multiple threads concurrently call printk() for many times, for it is difficult to interpret without knowing where these lines (or sometimes individual line which was divided into multiple lines due to race) came from. Since toggling after boot makes the code racy, currently there is no option to enable/disable at the kernel command line parameter or sysfs interface. config STACKTRACE_BUILD_ID bool "Show build ID information in stacktraces" depends on PRINTK help Selecting this option adds build ID information for symbols in stacktraces printed with the printk format '%p[SR]b'. This option is intended for distros where debuginfo is not easily accessible but can be downloaded given the build ID of the vmlinux or kernel module where the function is located. 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 CONSOLE_LOGLEVEL_QUIET int "quiet console loglevel (1-15)" range 1 15 default "4" help loglevel to use when "quiet" is passed on the kernel commandline. When "quiet" is passed on the kernel commandline this loglevel will be used as the loglevel. IOW passing "quiet" will be the equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>" 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 || PROC_FS) select DYNAMIC_DEBUG_CORE 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 or procfs. Thus, the debugfs or procfs 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. config DYNAMIC_DEBUG_CORE bool "Enable core function of dynamic debug support" depends on PRINTK depends on (DEBUG_FS || PROC_FS) help Enable core functional support of dynamic debug. It is useful when you want to tie dynamic debug to your kernel modules with DYNAMIC_DEBUG_MODULE defined for each of them, especially for the case of embedded system where the kernel image size is sensitive for people. config SYMBOLIC_ERRNAME bool "Support symbolic error names in printf" default y if PRINTK help If you say Y here, the kernel's printf implementation will be able to print symbolic error names such as ENOSPC instead of the number 28. It makes the kernel image slightly larger (about 3KB), but can make the kernel logs easier to read. 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. endmenu # "printk and dmesg options" 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_MISC bool "Miscellaneous debug code" default DEBUG_KERNEL depends on DEBUG_KERNEL help Say Y here if you need to enable miscellaneous debug code that should be under a more specific debug option but isn't. menu "Compile-time checks and compiler options" config DEBUG_INFO bool help A kernel debug info option other than "None" has been selected in the "Debug information" choice below, indicating that debug information will be generated for build targets. # Clang generates .uleb128 with label differences for DWARF v5, a feature that # older binutils ports do not support when utilizing RISC-V style linker # relaxation: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 config AS_HAS_NON_CONST_ULEB128 def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) choice prompt "Debug information" depends on DEBUG_KERNEL help Selecting something other than "None" results in a kernel image that 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. Choose which version of DWARF debug info to emit. If unsure, select "Toolchain default". config DEBUG_INFO_NONE bool "Disable debug information" help Do not build the kernel with debugging information, which will result in a faster and smaller build. config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT bool "Rely on the toolchain's implicit default DWARF version" select DEBUG_INFO depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_ULEB128) help The implicit default version of DWARF debug info produced by a toolchain changes over time. This can break consumers of the debug info that haven't upgraded to support newer revisions, and prevent testing newer versions, but those should be less common scenarios. config DEBUG_INFO_DWARF4 bool "Generate DWARF Version 4 debuginfo" select DEBUG_INFO depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) help Generate DWARF v4 debug info. This requires gcc 4.5+, binutils 2.35.2 if using clang without clang's integrated assembler, and gdb 7.0+. If you have consumers of DWARF debug info that are not ready for newer revisions of DWARF, you may wish to choose this or have your config select this. config DEBUG_INFO_DWARF5 bool "Generate DWARF Version 5 debuginfo" select DEBUG_INFO depends on !ARCH_HAS_BROKEN_DWARF5 depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_ULEB128) help Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc 5.0+ accepts the -gdwarf-5 flag but only had partial support for some draft features until 7.0), and gdb 8.0+. Changes to the structure of debug info in Version 5 allow for around 15-18% savings in resulting image and debug info section sizes as compared to DWARF Version 4. DWARF Version 5 standardizes previous extensions such as accelerators for symbol indexing and the format for fission (.dwo/.dwp) files. Users may not want to select this config if they rely on tooling that has not yet been updated to support DWARF Version 5. endchoice # "Debug information" if DEBUG_INFO config DEBUG_INFO_REDUCED bool "Reduce debugging information" 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. choice prompt "Compressed Debug information" help Compress the resulting debug info. Results in smaller debug info sections, but requires that consumers are able to decompress the results. If unsure, choose DEBUG_INFO_COMPRESSED_NONE. config DEBUG_INFO_COMPRESSED_NONE bool "Don't compress debug information" help Don't compress debug info sections. config DEBUG_INFO_COMPRESSED_ZLIB bool "Compress debugging information with zlib" depends on $(cc-option,-gz=zlib) depends on $(ld-option,--compress-debug-sections=zlib) help Compress the debug information using zlib. Requires GCC 5.0+ or Clang 5.0+, binutils 2.26+, and zlib. Users of dpkg-deb via scripts/package/builddeb may find an increase in size of their debug .deb packages with this config set, due to the debug info being compressed with zlib, then the object files being recompressed with a different compression scheme. But this is still preferable to setting $KDEB_COMPRESS to "none" which would be even larger. config DEBUG_INFO_COMPRESSED_ZSTD bool "Compress debugging information with zstd" depends on $(cc-option,-gz=zstd) depends on $(ld-option,--compress-debug-sections=zstd) help Compress the debug information using zstd. This may provide better compression than zlib, for about the same time costs, but requires newer toolchain support. Requires GCC 13.0+ or Clang 16.0+, binutils 2.40+, and zstd. endchoice # "Compressed Debug information" config DEBUG_INFO_SPLIT bool "Produce split debuginfo in .dwo files" depends on $(cc-option,-gsplit-dwarf) # RISC-V linker relaxation + -gsplit-dwarf has issues with LLVM and GCC # prior to 12.x: # https://github.com/llvm/llvm-project/issues/56642 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99090 depends on !RISCV || GCC_VERSION >= 120000 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_BTF bool "Generate BTF type information" depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST depends on BPF_SYSCALL depends on !DEBUG_INFO_DWARF5 || PAHOLE_VERSION >= 121 # pahole uses elfutils, which does not have support for Hexagon relocations depends on !HEXAGON help Generate deduplicated BTF type information from DWARF debug info. Turning this on expects presence of pahole tool, which will convert DWARF type info into equivalent deduplicated BTF type info. config PAHOLE_HAS_SPLIT_BTF def_bool PAHOLE_VERSION >= 119 config PAHOLE_HAS_BTF_TAG def_bool PAHOLE_VERSION >= 123 depends on CC_IS_CLANG help Decide whether pahole emits btf_tag attributes (btf_type_tag and btf_decl_tag) or not. Currently only clang compiler implements these attributes, so make the config depend on CC_IS_CLANG. config PAHOLE_HAS_LANG_EXCLUDE def_bool PAHOLE_VERSION >= 124 help Support for the --lang_exclude flag which makes pahole exclude compilation units from the supplied language. Used in Kbuild to omit Rust CUs which are not supported in version 1.24 of pahole, otherwise it would emit malformed kernel and module binaries when using DEBUG_INFO_BTF_MODULES. config DEBUG_INFO_BTF_MODULES bool "Generate BTF type information for kernel modules" default y depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF help Generate compact split BTF type information for kernel modules. config MODULE_ALLOW_BTF_MISMATCH bool "Allow loading modules with non-matching BTF type info" depends on DEBUG_INFO_BTF_MODULES help For modules whose split BTF does not match vmlinux, load without BTF rather than refusing to load. The default behavior with module BTF enabled is to reject modules with such mismatches; this option will still load module BTF where possible but ignore it when a mismatch is found. config GDB_SCRIPTS bool "Provide GDB scripts for kernel debugging" 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. endif # DEBUG_INFO config FRAME_WARN int "Warn for stack frames larger than" range 0 8192 default 0 if KMSAN default 2048 if GCC_PLUGIN_LATENT_ENTROPY default 2048 if PARISC default 1536 if (!64BIT && XTENSA) default 1280 if KASAN && !64BIT default 1024 if !64BIT default 2048 if 64BIT help Tell the compiler 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. 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 depends on CC_IS_GCC 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 HEADERS_INSTALL bool "Install uapi headers to usr/include" depends on !UML help This option will install uapi headers (headers exported to user-space) into the usr/include directory for use during the kernel build. This is unneeded for building the kernel itself, but needed for some user-space program samples. It is also needed by some features such as uapi header sanity checks. config DEBUG_SECTION_MISMATCH bool "Enable full Section mismatch analysis" depends on CC_IS_GCC 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 step 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). 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. config DEBUG_FORCE_FUNCTION_ALIGN_64B bool "Force all function address 64B aligned" depends on EXPERT && (X86_64 || ARM64 || PPC32 || PPC64 || ARC || RISCV || S390) select FUNCTION_ALIGNMENT_64B help There are cases that a commit from one domain changes the function address alignment of other domains, and cause magic performance bump (regression or improvement). Enable this option will help to verify if the bump is caused by function alignment changes, while it will slightly increase the kernel size and affect icache usage. It is mainly for debug and performance tuning use. # # 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 config FRAME_POINTER bool "Compile the kernel with frame pointers" depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || 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 OBJTOOL bool config STACK_VALIDATION bool "Compile-time stack metadata validation" depends on HAVE_STACK_VALIDATION && UNWINDER_FRAME_POINTER select OBJTOOL default n help Validate frame pointer rules at compile-time. This helps ensure that runtime stack traces are more reliable. For more information, see tools/objtool/Documentation/objtool.txt. config NOINSTR_VALIDATION bool depends on HAVE_NOINSTR_VALIDATION && DEBUG_ENTRY select OBJTOOL default y config VMLINUX_MAP bool "Generate vmlinux.map file when linking" depends on EXPERT help Selecting this option will pass "-Map=vmlinux.map" to ld when linking vmlinux. That file can be useful for verifying and debugging magic section games, and for seeing which pieces of code get eliminated with CONFIG_LD_DEAD_CODE_DATA_ELIMINATION. 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" menu "Generic Kernel Debugging Instruments" 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 MAGIC_SYSRQ_SERIAL_SEQUENCE string "Char sequence that enables magic SysRq over serial" depends on MAGIC_SYSRQ_SERIAL default "" help Specifies a sequence of characters that can follow BREAK to enable SysRq on a serial console. If unsure, leave an empty string and the option will not be enabled. 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. choice prompt "Debugfs default access" depends on DEBUG_FS default DEBUG_FS_ALLOW_ALL help This selects the default access restrictions for debugfs. It can be overridden with kernel command line option debugfs=[on,no-mount,off]. The restrictions apply for API access and filesystem registration. config DEBUG_FS_ALLOW_ALL bool "Access normal" help No restrictions apply. Both API and filesystem registration is on. This is the normal default operation. config DEBUG_FS_DISALLOW_MOUNT bool "Do not register debugfs as filesystem" help The API is open but filesystem is not loaded. Clients can still do their work and read with debug tools that do not need debugfs filesystem. config DEBUG_FS_ALLOW_NONE bool "No access" help Access is off. Clients get -PERM when trying to create nodes in debugfs tree and debugfs is not registered as a filesystem. Client can then back-off or continue without debugfs access. endchoice source "lib/Kconfig.kgdb" source "lib/Kconfig.ubsan" source "lib/Kconfig.kcsan" endmenu menu "Networking Debugging" source "net/Kconfig.debug" endmenu # "Networking Debugging" 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 SHRINKER_DEBUG bool "Enable shrinker debugging support" depends on DEBUG_FS help Say Y to enable the shrinker debugfs interface which provides visibility into the kernel memory shrinkers subsystem. Disable it to avoid an extra memory footprint. config DEBUG_STACK_USAGE bool "Stack utilization instrumentation" depends on DEBUG_KERNEL 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. Also emits a message to dmesg when a process exits if that process used more stack space than previously exiting processes. This option will slow down process creation somewhat. 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 ARCH_HAS_DEBUG_VM_PGTABLE bool help An architecture should select this when it can successfully build and run DEBUG_VM_PGTABLE. config DEBUG_VM_IRQSOFF def_bool DEBUG_VM && !PREEMPT_RT 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_SHOOT_LAZIES bool "Debug MMU_LAZY_TLB_SHOOTDOWN implementation" depends on DEBUG_VM depends on MMU_LAZY_TLB_SHOOTDOWN help Enable additional IPIs that ensure lazy tlb mm references are removed before the mm is freed. If unsure, say N. config DEBUG_VM_MAPLE_TREE bool "Debug VM maple trees" depends on DEBUG_VM select DEBUG_MAPLE_TREE help Enable VM maple tree debugging information and extra validations. 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 DEBUG_VM_PGTABLE bool "Debug arch page table for semantics compliance" depends on MMU depends on ARCH_HAS_DEBUG_VM_PGTABLE default y if DEBUG_VM help This option provides a debug method which can be used to test architecture page table helper functions on various platforms in verifying if they comply with expected generic MM semantics. This will help architecture code in making sure that any changes or new additions of these helpers still conform to expected semantics of the generic MM. Platforms will have to opt in for this through ARCH_HAS_DEBUG_VM_PGTABLE. 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 && 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_KMAP_LOCAL bool "Debug kmap_local temporary mappings" depends on DEBUG_KERNEL && KMAP_LOCAL help This option enables additional error checking for the kmap_local infrastructure. Disable for production use. config ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP bool config DEBUG_KMAP_LOCAL_FORCE_MAP bool "Enforce kmap_local temporary mappings" depends on DEBUG_KERNEL && ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP select KMAP_LOCAL select DEBUG_KMAP_LOCAL help This option enforces temporary mappings through the kmap_local mechanism for non-highmem pages and on non-highmem systems. Disable this for production systems! config DEBUG_HIGHMEM bool "Highmem debugging" depends on DEBUG_KERNEL && HIGHMEM select DEBUG_KMAP_LOCAL_FORCE_MAP if ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP select DEBUG_KMAP_LOCAL 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" source "lib/Kconfig.kfence" source "lib/Kconfig.kmsan" endmenu # "Memory Debugging" config DEBUG_SHIRQ bool "Debug shared IRQ handlers" depends on DEBUG_KERNEL help Enable this to generate a spurious interrupt just before a shared interrupt handler is deregistered (generating one when registering is currently disabled). Drivers need to handle this correctly. Some don't and need to be caught. menu "Debug Oops, 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 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 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 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 HAVE_HARDLOCKUP_DETECTOR_BUDDY bool depends on SMP default y # # Global switch whether to build a hardlockup detector at all. It is available # only when the architecture supports at least one implementation. There are # two exceptions. The hardlockup detector is never enabled on: # # s390: it reported many false positives there # # sparc64: has a custom implementation which is not using the common # hardlockup command line options and sysctl interface. # config HARDLOCKUP_DETECTOR bool "Detect Hard Lockups" depends on DEBUG_KERNEL && !S390 && !HARDLOCKUP_DETECTOR_SPARC64 depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_BUDDY || HAVE_HARDLOCKUP_DETECTOR_ARCH imply HARDLOCKUP_DETECTOR_PERF imply HARDLOCKUP_DETECTOR_BUDDY imply HARDLOCKUP_DETECTOR_ARCH select LOCKUP_DETECTOR 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. # # Note that arch-specific variants are always preferred. # config HARDLOCKUP_DETECTOR_PREFER_BUDDY bool "Prefer the buddy CPU hardlockup detector" depends on HARDLOCKUP_DETECTOR depends on HAVE_HARDLOCKUP_DETECTOR_PERF && HAVE_HARDLOCKUP_DETECTOR_BUDDY depends on !HAVE_HARDLOCKUP_DETECTOR_ARCH help Say Y here to prefer the buddy hardlockup detector over the perf one. With the buddy detector, each CPU uses its softlockup hrtimer to check that the next CPU is processing hrtimer interrupts by verifying that a counter is increasing. This hardlockup detector is useful on systems that don't have an arch-specific hardlockup detector or if resources needed for the hardlockup detector are better used for other things. config HARDLOCKUP_DETECTOR_PERF bool depends on HARDLOCKUP_DETECTOR depends on HAVE_HARDLOCKUP_DETECTOR_PERF && !HARDLOCKUP_DETECTOR_PREFER_BUDDY depends on !HAVE_HARDLOCKUP_DETECTOR_ARCH select HARDLOCKUP_DETECTOR_COUNTS_HRTIMER config HARDLOCKUP_DETECTOR_BUDDY bool depends on HARDLOCKUP_DETECTOR depends on HAVE_HARDLOCKUP_DETECTOR_BUDDY depends on !HAVE_HARDLOCKUP_DETECTOR_PERF || HARDLOCKUP_DETECTOR_PREFER_BUDDY depends on !HAVE_HARDLOCKUP_DETECTOR_ARCH select HARDLOCKUP_DETECTOR_COUNTS_HRTIMER config HARDLOCKUP_DETECTOR_ARCH bool depends on HARDLOCKUP_DETECTOR depends on HAVE_HARDLOCKUP_DETECTOR_ARCH help The arch-specific implementation of the hardlockup detector will be used. # # Both the "perf" and "buddy" hardlockup detectors count hrtimer # interrupts. This config enables functions managing this common code. # config HARDLOCKUP_DETECTOR_COUNTS_HRTIMER 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 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 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 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. config WQ_CPU_INTENSIVE_REPORT bool "Report per-cpu work items which hog CPU for too long" depends on DEBUG_KERNEL help Say Y here to enable reporting of concurrency-managed per-cpu work items that hog CPUs for longer than workqueue.cpu_intensive_thresh_us. Workqueue automatically detects and excludes them from concurrency management to prevent them from stalling other per-cpu work items. Occassional triggering may not necessarily indicate a problem. Repeated triggering likely indicates that the work item should be switched to use an unbound workqueue. config TEST_LOCKUP tristate "Test module to generate lockups" depends on m help This builds the "test_lockup" module that helps to make sure that watchdogs and lockup detectors are working properly. Depending on module parameters it could emulate soft or hard lockup, "hung task", or locking arbitrary lock for a long time. Also it could generate series of lockups with cooling-down periods. If unsure, say N. endmenu # "Debug lockups and hangs" menu "Scheduler Debugging" config SCHED_DEBUG bool "Collect scheduler debugging info" depends on DEBUG_KERNEL && DEBUG_FS default y help If you say Y here, the /sys/kernel/debug/sched 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. endmenu 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 && PREEMPTION && TRACE_IRQFLAGS_SUPPORT 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. This option has potential to introduce high runtime overhead, depending on workload as it triggers debugging routines for each this_cpu operation. It should only be used for debugging purposes. menu "Lock Debugging (spinlocks, mutexes, etc...)" config LOCK_DEBUGGING_SUPPORT bool depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT default y config PROVE_LOCKING bool "Lock debugging: prove locking correctness" depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT select LOCKDEP select DEBUG_SPINLOCK select DEBUG_MUTEXES if !PREEMPT_RT select DEBUG_RT_MUTEXES if RT_MUTEXES select DEBUG_RWSEMS select DEBUG_WW_MUTEX_SLOWPATH select DEBUG_LOCK_ALLOC select PREEMPT_COUNT if !ARCH_NO_PREEMPT 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.rst. config PROVE_RAW_LOCK_NESTING bool "Enable raw_spinlock - spinlock nesting checks" depends on PROVE_LOCKING default n help Enable the raw_spinlock vs. spinlock nesting checks which ensure that the lock nesting rules for PREEMPT_RT enabled kernels are not violated. NOTE: There are known nesting problems. So if you enable this option expect lockdep splats until these problems have been fully addressed which is work in progress. This config switch allows to identify and analyze these problems. It will be removed and the check permanently enabled once the main issues have been fixed. If unsure, select N. config LOCK_STAT bool "Lock usage statistics" depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT select LOCKDEP select DEBUG_SPINLOCK select DEBUG_MUTEXES if !PREEMPT_RT 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.rst 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_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 && !PREEMPT_RT 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 && LOCK_DEBUGGING_SUPPORT select DEBUG_LOCK_ALLOC select DEBUG_SPINLOCK select DEBUG_MUTEXES if !PREEMPT_RT select DEBUG_RT_MUTEXES if PREEMPT_RT 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_RWSEMS bool "RW Semaphore debugging: basic checks" depends on DEBUG_KERNEL help This debugging feature allows mismatched rw semaphore locks and unlocks to be detected and reported. config DEBUG_LOCK_ALLOC bool "Lock debugging: detect incorrect freeing of live locks" depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT select DEBUG_SPINLOCK select DEBUG_MUTEXES if !PREEMPT_RT 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 LOCKDEP bool depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT select STACKTRACE select KALLSYMS select KALLSYMS_ALL config LOCKDEP_SMALL bool config LOCKDEP_BITS int "Bitsize for MAX_LOCKDEP_ENTRIES" depends on LOCKDEP && !LOCKDEP_SMALL range 10 24 default 15 help Try increasing this value if you hit "BUG: MAX_LOCKDEP_ENTRIES too low!" message. config LOCKDEP_CHAINS_BITS int "Bitsize for MAX_LOCKDEP_CHAINS" depends on LOCKDEP && !LOCKDEP_SMALL range 10 30 default 16 help Try increasing this value if you hit "BUG: MAX_LOCKDEP_CHAINS too low!" message. config LOCKDEP_STACK_TRACE_BITS int "Bitsize for MAX_STACK_TRACE_ENTRIES" depends on LOCKDEP && !LOCKDEP_SMALL range 10 26 default 19 help Try increasing this value if you hit "BUG: MAX_STACK_TRACE_ENTRIES too low!" message. config LOCKDEP_STACK_TRACE_HASH_BITS int "Bitsize for STACK_TRACE_HASH_SIZE" depends on LOCKDEP && !LOCKDEP_SMALL range 10 26 default 14 help Try increasing this value if you need large STACK_TRACE_HASH_SIZE. config LOCKDEP_CIRCULAR_QUEUE_BITS int "Bitsize for elements in circular_queue struct" depends on LOCKDEP range 10 26 default 12 help Try increasing this value if you hit "lockdep bfs error:-1" warning due to __cq_enqueue() failure. config DEBUG_LOCKDEP bool "Lock dependency engine debugging" depends on DEBUG_KERNEL && LOCKDEP select DEBUG_IRQFLAGS 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 depends on !ARCH_NO_PREEMPT 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 won't 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 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. config SCF_TORTURE_TEST tristate "torture tests for smp_call_function*()" depends on DEBUG_KERNEL select TORTURE_TEST help This option provides a kernel module that runs torture tests on the smp_call_function() family of primitives. The kernel module may be built after the fact on the running kernel to be tested, if desired. config CSD_LOCK_WAIT_DEBUG bool "Debugging for csd_lock_wait(), called from smp_call_function*()" depends on DEBUG_KERNEL depends on 64BIT default n help This option enables debug prints when CPUs are slow to respond to the smp_call_function*() IPI wrappers. These debug prints include the IPI handler function currently executing (if any) and relevant stack traces. config CSD_LOCK_WAIT_DEBUG_DEFAULT bool "Default csd_lock_wait() debugging on at boot time" depends on CSD_LOCK_WAIT_DEBUG depends on 64BIT default n help This option causes the csdlock_debug= kernel boot parameter to default to 1 (basic debugging) instead of 0 (no debugging). endmenu # lock debugging config TRACE_IRQFLAGS depends on TRACE_IRQFLAGS_SUPPORT bool help Enables hooks to interrupt enabling and disabling for either tracing or lock debugging. config TRACE_IRQFLAGS_NMI def_bool y depends on TRACE_IRQFLAGS depends on TRACE_IRQFLAGS_NMI_SUPPORT config NMI_CHECK_CPU bool "Debugging for CPUs failing to respond to backtrace requests" depends on DEBUG_KERNEL depends on X86 default n help Enables debug prints when a CPU fails to respond to a given backtrace NMI. These prints provide some reasons why a CPU might legitimately be failing to respond, for example, if it is offline of if ignore_nmis is set. config DEBUG_IRQFLAGS bool "Debug IRQ flag manipulation" help Enables checks for potentially unsafe enabling or disabling of interrupts, such as calling raw_local_irq_restore() when interrupts are enabled. 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 cannot do anything actionable to address this, by default this option is disabled. Say Y here if you want to receive warnings for all uses of unseeded randomness. This will be of use primarily for those developers interested 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 its 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 menu "Debug kernel data structures" config DEBUG_LIST bool "Debug linked list manipulation" depends on DEBUG_KERNEL select LIST_HARDENED help Enable this to turn on extended checks in the linked-list walking routines. This option trades better quality error reports for performance, and is more suitable for kernel debugging. If you care about performance, you should only enable CONFIG_LIST_HARDENED instead. If unsure, say N. config DEBUG_PLIST 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_CLOSURES bool "Debug closures (bcache async widgits)" depends on CLOSURES select DEBUG_FS help Keeps all active closures in a linked list and provides a debugfs interface to list them, which makes it possible to see asynchronous operations that get stuck. config DEBUG_MAPLE_TREE bool "Debug maple trees" depends on DEBUG_KERNEL help Enable maple tree debugging information and extra validations. If unsure, say N. endmenu 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 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 LATENCYTOP bool "Latency measuring infrastructure" depends on DEBUG_KERNEL depends on STACKTRACE_SUPPORT depends on PROC_FS depends on FRAME_POINTER || MIPS || PPC || S390 || MICROBLAZE || ARM || ARC || X86 select KALLSYMS select KALLSYMS_ALL select STACKTRACE select SCHEDSTATS help Enable this option if you want to use the LatencyTOP tool to find out which userspace is blocking on what kernel operations. config DEBUG_CGROUP_REF bool "Disable inlining of cgroup css reference count functions" depends on DEBUG_KERNEL depends on CGROUPS depends on KPROBES default n help Force cgroup css reference count functions to not be inlined so that they can be kprobed for debugging. 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/core-api/debugging-via-ohci1394.rst for more information. source "samples/Kconfig" 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 || GENERIC_LIB_DEVMEM_IS_ALLOWED default y if PPC || X86 || ARM64 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. menu "$(SRCARCH) Debugging" source "arch/$(SRCARCH)/Kconfig.debug" endmenu menu "Kernel Testing and Coverage" source "lib/kunit/Kconfig" 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 FUNCTION_ERROR_INJECTION bool "Fault-injections of functions" depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES help Add fault injections into various functions that are annotated with ALLOW_ERROR_INJECTION() in the kernel. BPF may also modify the return value of these functions. This is useful to test error paths of code. 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 help Provide fault-injection capability for kmalloc. config FAIL_PAGE_ALLOC bool "Fault-injection capability for alloc_pages()" depends on FAULT_INJECTION help Provide fault-injection capability for alloc_pages(). config FAULT_INJECTION_USERCOPY bool "Fault injection capability for usercopy functions" depends on FAULT_INJECTION help Provides fault-injection capability to inject failures in usercopy functions (copy_from_user(), get_user(), ...). 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 won't do anything. 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 FAIL_FUNCTION bool "Fault-injection capability for functions" depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION help Provide function-based fault-injection capability. This will allow you to override a specific function with a return with given return value. As a result, function caller will see an error value and have to handle it. This is useful to test the error handling in various subsystems. 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_SUNRPC bool "Fault-injection capability for SunRPC" depends on FAULT_INJECTION_DEBUG_FS && SUNRPC_DEBUG help Provide fault-injection capability for SunRPC and its consumers. config FAULT_INJECTION_CONFIGFS bool "Configfs interface for fault-injection capabilities" depends on FAULT_INJECTION select CONFIGFS_FS help This option allows configfs-based drivers to dynamically configure fault-injection via configfs. Each parameter for driver-specific fault-injection can be made visible as a configfs attribute in a configfs group. config FAULT_INJECTION_STACKTRACE_FILTER bool "stacktrace filter for fault-injection capabilities" depends on FAULT_INJECTION depends on (FAULT_INJECTION_DEBUG_FS || FAULT_INJECTION_CONFIGFS) && STACKTRACE_SUPPORT select STACKTRACE depends on FRAME_POINTER || MIPS || PPC || S390 || MICROBLAZE || ARM || ARC || X86 help Provide stacktrace filter for fault-injection capabilities config ARCH_HAS_KCOV bool help An architecture should select this when it can successfully build and run with CONFIG_KCOV. This typically requires disabling instrumentation for some early boot code. config CC_HAS_SANCOV_TRACE_PC def_bool $(cc-option,-fsanitize-coverage=trace-pc) config KCOV bool "Code coverage for fuzzing" depends on ARCH_HAS_KCOV depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS depends on !ARCH_WANTS_NO_INSTR || HAVE_NOINSTR_HACK || \ GCC_VERSION >= 120000 || CLANG_VERSION >= 130000 select DEBUG_FS select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC select OBJTOOL if HAVE_NOINSTR_HACK help KCOV exposes kernel code coverage information in a form suitable for coverage-guided fuzzing (randomized testing). For more details, see Documentation/dev-tools/kcov.rst. config KCOV_ENABLE_COMPARISONS bool "Enable comparison operands collection by KCOV" depends on KCOV depends on $(cc-option,-fsanitize-coverage=trace-cmp) 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 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 KCOV_IRQ_AREA_SIZE hex "Size of interrupt coverage collection area in words" depends on KCOV default 0x40000 help KCOV uses preallocated per-cpu areas to collect coverage from soft interrupts. This specifies the size of those areas in the number of unsigned long words. menuconfig RUNTIME_TESTING_MENU bool "Runtime Testing" def_bool y if RUNTIME_TESTING_MENU config TEST_DHRY tristate "Dhrystone benchmark test" help Enable this to include the Dhrystone 2.1 benchmark. This test calculates the number of Dhrystones per second, and the number of DMIPS (Dhrystone MIPS) obtained when the Dhrystone score is divided by 1757 (the number of Dhrystones per second obtained on the VAX 11/780, nominally a 1 MIPS machine). To run the benchmark, it needs to be enabled explicitly, either from the kernel command line (when built-in), or from userspace (when built-in or modular. Run once during kernel boot: test_dhry.run Set number of iterations from kernel command line: test_dhry.iterations=<n> Set number of iterations from userspace: echo <n> > /sys/module/test_dhry/parameters/iterations Trigger manual run from userspace: echo y > /sys/module/test_dhry/parameters/run If the number of iterations is <= 0, the test will devise a suitable number of iterations (test runs for at least 2s) automatically. This process takes ca. 4s. If unsure, say N. config LKDTM tristate "Linux Kernel Dump Test Tool Module" depends on DEBUG_FS 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.rst config CPUMASK_KUNIT_TEST tristate "KUnit test for cpumask" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Enable to turn on cpumask tests, running at boot or module load time. For more information on KUnit and unit tests in general, please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config TEST_LIST_SORT tristate "Linked list sorting test" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS 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_MIN_HEAP tristate "Min heap test" depends on DEBUG_KERNEL || m help Enable this to turn on min heap function tests. 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" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This option enables the self-test function of 'sort()' at boot, or at module load time. If unsure, say N. config TEST_DIV64 tristate "64bit/32bit division and modulo test" depends on DEBUG_KERNEL || m help Enable this to turn on 'do_div()' 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_IOV_ITER tristate "Test iov_iter operation" if !KUNIT_ALL_TESTS depends on KUNIT depends on MMU default KUNIT_ALL_TESTS help Enable this to turn on testing of the operation of the I/O iterator (iov_iter). This test is executed only once during system boot (so affects only boot time), or at module load time. If unsure, say N. config KPROBES_SANITY_TEST tristate "Kprobes sanity tests" if !KUNIT_ALL_TESTS depends on DEBUG_KERNEL depends on KPROBES depends on KUNIT select STACKTRACE if ARCH_CORRECT_STACKTRACE_ON_KRETPROBE default KUNIT_ALL_TESTS help This option provides for testing basic kprobes functionality on boot. Samples of kprobe and kretprobe are inserted and verified for functionality. Say N if you are unsure. config FPROBE_SANITY_TEST bool "Self test for fprobe" depends on DEBUG_KERNEL depends on FPROBE depends on KUNIT=y help This option will enable testing the fprobe when the system boot. A series of tests are made to verify that the fprobe is functioning properly. Say N if you are unsure. config BACKTRACE_SELF_TEST tristate "Self test for the backtrace code" depends on DEBUG_KERNEL 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 TEST_REF_TRACKER tristate "Self test for reference tracker" depends on DEBUG_KERNEL && STACKTRACE_SUPPORT select REF_TRACKER help This option provides a kernel module performing tests using reference tracker infrastructure. 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 REED_SOLOMON_TEST tristate "Reed-Solomon library test" depends on DEBUG_KERNEL || m select REED_SOLOMON select REED_SOLOMON_ENC16 select REED_SOLOMON_DEC16 help This option enables the self-test function of rslib at boot, or at module load time. If unsure, say N. 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 STRING_SELFTEST tristate "Test string functions 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_SCANF tristate "Test scanf() family of functions at runtime" config TEST_BITMAP tristate "Test bitmap_*() family of functions at runtime" 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_XARRAY tristate "Test the XArray code at runtime" config TEST_MAPLE_TREE tristate "Test the Maple Tree code at runtime or module load" help Enable this option to test the maple tree code functions at boot, or when the module is loaded. Enable "Debug Maple Trees" will enable more verbose output on failures. If unsure, say N. config TEST_RHASHTABLE tristate "Perform selftest on resizable hash table" help Enable this option to test the rhashtable functions at boot. If unsure, say N. config TEST_IDA tristate "Perform selftest on IDA functions" config TEST_PARMAN tristate "Perform selftest on priority array manager" depends on PARMAN help Enable this option to test priority array manager on boot (or module load). If unsure, say N. config TEST_IRQ_TIMINGS bool "IRQ timings selftest" depends on IRQ_TIMINGS help Enable this option to test the irq timings code on boot. If unsure, say N. config TEST_LKM tristate "Test module loading with 'hello world' module" 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_BITOPS tristate "Test module for compilation of bitops operations" depends on m help This builds the "test_bitops" module that is much like the TEST_LKM module except that it does a basic exercise of the set/clear_bit macros and get_count_order/long to make sure there are no compiler warnings from C=1 sparse checker or -Wextra compilations. It has no dependencies and doesn't run or load unless explicitly requested by name. for example: modprobe test_bitops. If unsure, say N. config TEST_VMALLOC tristate "Test module for stress/performance analysis of vmalloc allocator" default n depends on MMU depends on m help This builds the "test_vmalloc" module that should be used for stress and performance analysis. So, any new change for vmalloc subsystem can be evaluated from performance and stability point of view. If unsure, say N. config TEST_USER_COPY tristate "Test user/kernel boundary protections" 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" 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_BLACKHOLE_DEV tristate "Test blackhole netdev functionality" depends on m && NET help This builds the "test_blackhole_dev" module that validates the data path through this blackhole netdev. If unsure, say N. config FIND_BIT_BENCHMARK tristate "Test find_bit functions" 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" 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" 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 BITFIELD_KUNIT tristate "KUnit test bitfield functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Enable this option to test the bitfield functions at boot. KUnit tests run during boot and output the results to the debug log in TAP format (http://testanything.org/). Only useful for kernel devs running the KUnit test harness, and not intended for inclusion into a production build. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config CHECKSUM_KUNIT tristate "KUnit test checksum functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Enable this option to test the checksum functions at boot. KUnit tests run during boot and output the results to the debug log in TAP format (http://testanything.org/). Only useful for kernel devs running the KUnit test harness, and not intended for inclusion into a production build. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config HASH_KUNIT_TEST tristate "KUnit Test for integer hash functions" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Enable this option to test the kernel's string (<linux/stringhash.h>), and integer (<linux/hash.h>) hash functions on boot. KUnit tests run during boot and output the results to the debug log in TAP format (https://testanything.org/). Only useful for kernel devs running the KUnit test harness, and not intended for inclusion into a production build. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. This is intended to help people writing architecture-specific optimized versions. If unsure, say N. config RESOURCE_KUNIT_TEST tristate "KUnit test for resource API" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This builds the resource API unit test. Tests the logic of API provided by resource.c and ioport.h. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config SYSCTL_KUNIT_TEST tristate "KUnit test for sysctl" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This builds the proc sysctl unit test, which runs on boot. Tests the API contract and implementation correctness of sysctl. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config LIST_KUNIT_TEST tristate "KUnit Test for Kernel Linked-list structures" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This builds the linked list KUnit test suite. It tests that the API and basic functionality of the list_head type and associated macros. KUnit tests run during boot and output the results to the debug log in TAP format (https://testanything.org/). Only useful for kernel devs running the KUnit test harness, and not intended for inclusion into a production build. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config HASHTABLE_KUNIT_TEST tristate "KUnit Test for Kernel Hashtable structures" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This builds the hashtable KUnit test suite. It tests the basic functionality of the API defined in include/linux/hashtable.h. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config LINEAR_RANGES_TEST tristate "KUnit test for linear_ranges" depends on KUNIT select LINEAR_RANGES help This builds the linear_ranges unit test, which runs on boot. Tests the linear_ranges logic correctness. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config CMDLINE_KUNIT_TEST tristate "KUnit test for cmdline API" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This builds the cmdline API unit test. Tests the logic of API provided by cmdline.c. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config BITS_TEST tristate "KUnit test for bits.h" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help This builds the bits unit test. Tests the logic of macros defined in bits.h. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config SLUB_KUNIT_TEST tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS depends on SLUB_DEBUG && KUNIT default KUNIT_ALL_TESTS help This builds SLUB allocator unit test. Tests SLUB cache debugging functionality. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config RATIONAL_KUNIT_TEST tristate "KUnit test for rational.c" if !KUNIT_ALL_TESTS depends on KUNIT && RATIONAL default KUNIT_ALL_TESTS help This builds the rational math unit test. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config MEMCPY_KUNIT_TEST tristate "Test memcpy(), memmove(), and memset() functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Builds unit tests for memcpy(), memmove(), and memset() functions. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config MEMCPY_SLOW_KUNIT_TEST bool "Include exhaustive memcpy tests" depends on MEMCPY_KUNIT_TEST default y help Some memcpy tests are quite exhaustive in checking for overlaps and bit ranges. These can be very slow, so they are split out as a separate config, in case they need to be disabled. Note this config option will be replaced by the use of KUnit test attributes. config IS_SIGNED_TYPE_KUNIT_TEST tristate "Test is_signed_type() macro" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Builds unit tests for the is_signed_type() macro. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config OVERFLOW_KUNIT_TEST tristate "Test check_*_overflow() functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Builds unit tests for the check_*_overflow(), size_*(), allocation, and related functions. For more information on KUnit and unit tests in general please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. config STACKINIT_KUNIT_TEST tristate "Test level of stack variable initialization" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Test if the kernel is zero-initializing stack variables and padding. Coverage is controlled by compiler flags, CONFIG_INIT_STACK_ALL_PATTERN, CONFIG_INIT_STACK_ALL_ZERO, CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF, or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL. config FORTIFY_KUNIT_TEST tristate "Test fortified str*() and mem*() function internals at runtime" if !KUNIT_ALL_TESTS depends on KUNIT && FORTIFY_SOURCE default KUNIT_ALL_TESTS help Builds unit tests for checking internals of FORTIFY_SOURCE as used by the str*() and mem*() family of functions. For testing runtime traps of FORTIFY_SOURCE, see LKDTM's "FORTIFY_*" tests. config HW_BREAKPOINT_KUNIT_TEST bool "Test hw_breakpoint constraints accounting" if !KUNIT_ALL_TESTS depends on HAVE_HW_BREAKPOINT depends on KUNIT=y default KUNIT_ALL_TESTS help Tests for hw_breakpoint constraints accounting. If unsure, say N. config STRCAT_KUNIT_TEST tristate "Test strcat() family of functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS config STRSCPY_KUNIT_TEST tristate "Test strscpy*() family of functions at runtime" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS config SIPHASH_KUNIT_TEST tristate "Perform selftest on siphash functions" if !KUNIT_ALL_TESTS depends on KUNIT default KUNIT_ALL_TESTS help Enable this option to test the kernel's 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_UDELAY tristate "udelay test driver" 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" depends on m help Test the static key interfaces. If unsure, say N. config TEST_DYNAMIC_DEBUG tristate "Test DYNAMIC_DEBUG" depends on DYNAMIC_DEBUG help This module registers a tracer callback to count enabled pr_debugs in a 'do_debugging' function, then alters their enablements, calls the function, and compares counts. If unsure, say N. config TEST_KMOD tristate "kmod stress tester" depends on m depends on NETDEVICES && NET_CORE && INET # for TUN depends on BLOCK depends on PAGE_SIZE_LESS_THAN_256KB # for BTRFS 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. config TEST_MEMCAT_P tristate "Test memcat_p() helper function" help Test the memcat_p() helper for correctly merging two pointer arrays together. If unsure, say N. config TEST_LIVEPATCH tristate "Test livepatching" default n depends on DYNAMIC_DEBUG depends on LIVEPATCH depends on m help Test kernel livepatching features for correctness. The tests will load test modules that will be livepatched in various scenarios. To run all the livepatching tests: make -C tools/testing/selftests TARGETS=livepatch run_tests Alternatively, individual tests may be invoked: tools/testing/selftests/livepatch/test-callbacks.sh tools/testing/selftests/livepatch/test-livepatch.sh tools/testing/selftests/livepatch/test-shadow-vars.sh If unsure, say N. config TEST_OBJAGG tristate "Perform selftest on object aggreration manager" default n depends on OBJAGG help Enable this option to test object aggregation manager on boot (or module load). config TEST_MEMINIT tristate "Test heap/page initialization" help Test if the kernel is zero-initializing heap and page allocations. This can be useful to test init_on_alloc and init_on_free features. If unsure, say N. config TEST_HMM tristate "Test HMM (Heterogeneous Memory Management)" depends on TRANSPARENT_HUGEPAGE depends on DEVICE_PRIVATE select HMM_MIRROR select MMU_NOTIFIER help This is a pseudo device driver solely for testing HMM. Say M here if you want to build the HMM test module. Doing so will allow you to run tools/testing/selftest/vm/hmm-tests. If unsure, say N. config TEST_FREE_PAGES tristate "Test freeing pages" help Test that a memory leak does not occur due to a race between freeing a block of pages and a speculative page reference. Loading this module is safe if your kernel has the bug fixed. If the bug is not fixed, it will leak gigabytes of memory and probably OOM your system. config TEST_FPU tristate "Test floating point operations in kernel space" depends on X86 && !KCOV_INSTRUMENT_ALL help Enable this option to add /sys/kernel/debug/selftest_helpers/test_fpu which will trigger a sequence of floating point operations. This is used for self-testing floating point control register setting in kernel_fpu_begin(). If unsure, say N. config TEST_CLOCKSOURCE_WATCHDOG tristate "Test clocksource watchdog in kernel space" depends on CLOCKSOURCE_WATCHDOG help Enable this option to create a kernel module that will trigger a test of the clocksource watchdog. This module may be loaded via modprobe or insmod in which case it will run upon being loaded, or it may be built in, in which case it will run shortly after boot. If unsure, say N. config TEST_OBJPOOL tristate "Test module for correctness and stress of objpool" default n depends on m && DEBUG_KERNEL help This builds the "test_objpool" module that should be used for correctness verification and concurrent testings of objects allocation and reclamation. If unsure, say N. endif # RUNTIME_TESTING_MENU config ARCH_USE_MEMTEST bool help An architecture should select this when it uses early_memtest() during boot process. config MEMTEST bool "Memtest" depends on ARCH_USE_MEMTEST help This option adds a kernel parameter 'memtest', which allows memtest to be set and executed. 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 HYPERV_TESTING bool "Microsoft Hyper-V driver testing" default n depends on HYPERV && DEBUG_FS help Select this option to enable Hyper-V vmbus testing. endmenu # "Kernel Testing and Coverage" menu "Rust hacking" config RUST_DEBUG_ASSERTIONS bool "Debug assertions" depends on RUST help Enables rustc's `-Cdebug-assertions` codegen option. This flag lets you turn `cfg(debug_assertions)` conditional compilation on or off. This can be used to enable extra debugging code in development but not in production. For example, it controls the behavior of the standard library's `debug_assert!` macro. Note that this will apply to all Rust code, including `core`. If unsure, say N. config RUST_OVERFLOW_CHECKS bool "Overflow checks" default y depends on RUST help Enables rustc's `-Coverflow-checks` codegen option. This flag allows you to control the behavior of runtime integer overflow. When overflow-checks are enabled, a Rust panic will occur on overflow. Note that this will apply to all Rust code, including `core`. If unsure, say Y. config RUST_BUILD_ASSERT_ALLOW bool "Allow unoptimized build-time assertions" depends on RUST help Controls how `build_error!` and `build_assert!` are handled during the build. If calls to them exist in the binary, it may indicate a violated invariant or that the optimizer failed to verify the invariant during compilation. This should not happen, thus by default the build is aborted. However, as an escape hatch, you can choose Y here to ignore them during build and let the check be carried at runtime (with `panic!` being called if the check fails). If unsure, say N. config RUST_KERNEL_DOCTESTS bool "Doctests for the `kernel` crate" if !KUNIT_ALL_TESTS depends on RUST && KUNIT=y default KUNIT_ALL_TESTS help This builds the documentation tests of the `kernel` crate as KUnit tests. For more information on KUnit and unit tests in general, please refer to the KUnit documentation in Documentation/dev-tools/kunit/. If unsure, say N. endmenu # "Rust" endmenu # Kernel hacking