# 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 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 jiffy" 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=27215config 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 || (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 debian/rules 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 or DPKG_DEB_COMPRESSOR_TYPE 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 PAHOLE_VERSION >= 116 depends on DEBUG_INFO_DWARF4 || 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 requires pahole v1.16 or later (v1.21 or later to support DWARF 5), 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/process/debugging/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 !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" 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.Lines 1–500 of 3431. 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 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 jiffy" 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 || (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 debian/rules 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 or DPKG_DEB_COMPRESSOR_TYPE 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 PAHOLE_VERSION >= 116 depends on DEBUG_INFO_DWARF4 || 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 requires pahole v1.16 or later (v1.21 or later to support DWARF 5), 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/process/debugging/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 !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" 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.