# SPDX-License-Identifier: GPL-2.0-onlymenu "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 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" menu "Compile-time checks and compiler options" config DEBUG_INFO bool "Compile the kernel with debug info" depends on DEBUG_KERNEL && !COMPILE_TEST help If you say Y here the resulting kernel image will include debugging info resulting in a larger kernel image. This adds debug symbols to the kernel and modules (gcc -g), and is needed if you intend to use kernel crashdump or binary object tools like crash, kgdb, LKCD, gdb, etc on the kernel. Say Y here only if you plan to debug the kernel. If unsure, say N. 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. config DEBUG_INFO_COMPRESSED bool "Compressed debugging information" 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_SPLIT bool "Produce split debuginfo in .dwo files" depends on $(cc-option,-gsplit-dwarf) help Generate debug info into separate .dwo files. This significantly reduces the build directory size for builds with DEBUG_INFO, because it stores the information only once on disk in .dwo files instead of multiple times in object files and executables. In addition the debug information is also compressed. Requires recent gcc (4.7+) and recent gdb/binutils. Any tool that packages or reads debug information would need to know about the .dwo files and include them. Incompatible with older versions of ccache. config DEBUG_INFO_DWARF4 bool "Generate dwarf4 debuginfo" depends on $(cc-option,-gdwarf-4) help Generate dwarf4 debug info. This requires recent versions of gcc and gdb. It makes the debug information larger. But it significantly improves the success of resolving variables in gdb on optimized code. config DEBUG_INFO_BTF bool "Generate BTF typeinfo" depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST 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 $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119") config DEBUG_INFO_BTF_MODULES def_bool y depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF help Generate compact split BTF type information for kernel modules. 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 2048 if GCC_PLUGIN_LATENT_ENTROPY default 1280 if (!64BIT && PARISC) default 1024 if (!64BIT && !PARISC) default 2048 if 64BIT help Tell gcc to warn at build time for stack frames larger than this. Setting this too low will cause a lot of warnings. Setting it to 0 disables the warning. config STRIP_ASM_SYMS bool "Strip assembler-generated symbols during link" default n help Strip internal assembler-generated symbols during a link (symbols that look like '.Lxxx') so they don't pollute the output of get_wchan() and suchlike. config READABLE_ASM bool "Generate readable assembler code" depends on DEBUG_KERNEL help Disable some compiler optimizations that tend to generate human unreadable assembler output. This may make the kernel slightly slower, but it helps to keep kernel developers who have to stare a lot at assembler listings sane. config 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" 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_32B bool "Force all function address 32B aligned" if EXPERT 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 STACK_VALIDATION bool "Compile-time stack metadata validation" depends on HAVE_STACK_VALIDATION default n help Add compile-time checks to validate stack metadata, including frame pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure that runtime stack traces are more reliable. This is also a prerequisite for generation of ORC unwind data, which is needed for CONFIG_UNWINDER_ORC. For more information, see tools/objtool/Documentation/stack-validation.txt. config VMLINUX_VALIDATION bool depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT default y 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"Lines 1–500 of 2496. Load more
# 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 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" menu "Compile-time checks and compiler options" config DEBUG_INFO bool "Compile the kernel with debug info" depends on DEBUG_KERNEL && !COMPILE_TEST help If you say Y here the resulting kernel image will include debugging info resulting in a larger kernel image. This adds debug symbols to the kernel and modules (gcc -g), and is needed if you intend to use kernel crashdump or binary object tools like crash, kgdb, LKCD, gdb, etc on the kernel. Say Y here only if you plan to debug the kernel. If unsure, say N. 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. config DEBUG_INFO_COMPRESSED bool "Compressed debugging information" 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_SPLIT bool "Produce split debuginfo in .dwo files" depends on $(cc-option,-gsplit-dwarf) help Generate debug info into separate .dwo files. This significantly reduces the build directory size for builds with DEBUG_INFO, because it stores the information only once on disk in .dwo files instead of multiple times in object files and executables. In addition the debug information is also compressed. Requires recent gcc (4.7+) and recent gdb/binutils. Any tool that packages or reads debug information would need to know about the .dwo files and include them. Incompatible with older versions of ccache. config DEBUG_INFO_DWARF4 bool "Generate dwarf4 debuginfo" depends on $(cc-option,-gdwarf-4) help Generate dwarf4 debug info. This requires recent versions of gcc and gdb. It makes the debug information larger. But it significantly improves the success of resolving variables in gdb on optimized code. config DEBUG_INFO_BTF bool "Generate BTF typeinfo" depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST 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 $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119") config DEBUG_INFO_BTF_MODULES def_bool y depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF help Generate compact split BTF type information for kernel modules. 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 2048 if GCC_PLUGIN_LATENT_ENTROPY default 1280 if (!64BIT && PARISC) default 1024 if (!64BIT && !PARISC) default 2048 if 64BIT help Tell gcc to warn at build time for stack frames larger than this. Setting this too low will cause a lot of warnings. Setting it to 0 disables the warning. config STRIP_ASM_SYMS bool "Strip assembler-generated symbols during link" default n help Strip internal assembler-generated symbols during a link (symbols that look like '.Lxxx') so they don't pollute the output of get_wchan() and suchlike. config READABLE_ASM bool "Generate readable assembler code" depends on DEBUG_KERNEL help Disable some compiler optimizations that tend to generate human unreadable assembler output. This may make the kernel slightly slower, but it helps to keep kernel developers who have to stare a lot at assembler listings sane. config 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" 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_32B bool "Force all function address 32B aligned" if EXPERT 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 STACK_VALIDATION bool "Compile-time stack metadata validation" depends on HAVE_STACK_VALIDATION default n help Add compile-time checks to validate stack metadata, including frame pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure that runtime stack traces are more reliable. This is also a prerequisite for generation of ORC unwind data, which is needed for CONFIG_UNWINDER_ORC. For more information, see tools/objtool/Documentation/stack-validation.txt. config VMLINUX_VALIDATION bool depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT default y 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"