kernel/linux.git/Documentation/kbuild, branch v6.19.11

kbuild: doc: improve KBUILD_BUILD_TIMESTAMP documentation

2025-11-08T11:17:58+00:00

This patch adds an example of how to set KBUILD_BUILD_TIMESTAMP to a specific date. Also, note that the provided timestamp is used for initramfs mtime fields, which are 32-bit and thus limited to dates between the Unix epoch and 2106-02-07 06:28:15 UTC. Dates outside this range will cause errors. Suggested-by: David Disseldorp Signed-off-by: Gang Yan Reviewed-by: David Disseldorp Reviewed-by: Nicolas Schier Link: https://patch.msgid.link/20251017021209.6586-1-gang.yan@linux.dev Signed-off-by: Nicolas Schier

Merge tag 'kbuild-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux

2025-10-02T03:58:51+00:00

Pull Kbuild updates from Nathan Chancellor: - Extend modules.builtin.modinfo to include module aliases from MODULE_DEVICE_TABLE for builtin modules so that userspace tools (such as kmod) can verify that a particular module alias will be handled by a builtin module - Bump the minimum version of LLVM for building the kernel to 15.0.0 - Upgrade several userspace API checks in headers_check.pl to errors - Unify and consolidate CONFIG_WERROR / W=e handling - Turn assembler and linker warnings into errors with CONFIG_WERROR / W=e - Respect CONFIG_WERROR / W=e when building userspace programs (userprogs) - Enable -Werror unconditionally when building host programs (hostprogs) - Support copy_file_range() and data segment alignment in gen_init_cpio to improve performance on filesystems that support reflinks such as btrfs and XFS - Miscellaneous small changes to scripts and configuration files * tag 'kbuild-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux: (47 commits) modpost: Initialize builtin_modname to stop SIGSEGVs Documentation: kbuild: note CONFIG_DEBUG_EFI in reproducible builds kbuild: vmlinux.unstripped should always depend on .vmlinux.export.o modpost: Create modalias for builtin modules modpost: Add modname to mod_device_table alias scsi: Always define blogic_pci_tbl structure kbuild: extract modules.builtin.modinfo from vmlinux.unstripped kbuild: keep .modinfo section in vmlinux.unstripped kbuild: always create intermediate vmlinux.unstripped s390: vmlinux.lds.S: Reorder sections KMSAN: Remove tautological checks objtool: Drop noinstr hack for KCSAN_WEAK_MEMORY lib/Kconfig.debug: Drop CLANG_VERSION check from DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT riscv: Remove ld.lld version checks from many TOOLCHAIN_HAS configs riscv: Unconditionally use linker relaxation riscv: Remove version check for LTO_CLANG selects powerpc: Drop unnecessary initializations in __copy_inst_from_kernel_nofault() mips: Unconditionally select ARCH_HAS_CURRENT_STACK_POINTER arm64: Remove tautological LLVM Kconfig conditions ARM: Clean up definition of ARM_HAS_GROUP_RELOCS ...

Documentation: kbuild: note CONFIG_DEBUG_EFI in reproducible builds

2025-09-25T11:41:48+00:00

CONFIG_EFI_DEBUG embeds absolute file paths into object files, which makes the resulting vmlinux specific to the build environment. Add a note about this in reproducible-builds.rst Signed-off-by: Masahiro Yamada Signed-off-by: Nicolas Schier Reviewed-by: Randy Dunlap Tested-by: Randy Dunlap Link: https://patch.msgid.link/20250924-kbuild-doc-config-debug-efi-in-reproducible-builds-v2-1-d2d6b9dcdb7d@kernel.org Signed-off-by: Nathan Chancellor

kconfig: Add transitional symbol attribute for migration support

2025-09-24T21:23:35+00:00

During kernel option migrations (e.g. CONFIG_CFI_CLANG to CONFIG_CFI), existing .config files need to maintain backward compatibility while preventing deprecated options from appearing in newly generated configurations. This is challenging with existing Kconfig mechanisms because: 1. Simply removing old options breaks existing .config files. 2. Manually listing an option as "deprecated" leaves it needlessly visible and still writes them to new .config files. 3. Using any method to remove visibility (.e.g no 'prompt', 'if n', etc) prevents the option from being processed at all. Add a "transitional" attribute that creates symbols which are: - Processed during configuration (can influence other symbols' defaults) - Hidden from user menus (no prompts appear) - Omitted from newly written .config files (gets migrated) - Restricted to only having help sections (no defaults, selects, etc) making it truly just a "prior value pass-through" option. The transitional syntax requires a type argument and prevents type redefinition: config NEW_OPTION bool "New option" default OLD_OPTION config OLD_OPTION bool transitional help Transitional config for OLD_OPTION migration. This allows seamless migration: olddefconfig processes existing CONFIG_OLD_OPTION=y settings to enable CONFIG_NEW_OPTION=y, while CONFIG_OLD_OPTION is omitted from newly generated .config files. Added positive and negative testing via "testconfig" make target. Co-developed-by: Vegard Nossum Signed-off-by: Vegard Nossum Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/20250923213422.1105654-2-kees@kernel.org Signed-off-by: Kees Cook

docs: kconfig: add alldefconfig to the all*configs

2025-07-26T06:31:29+00:00

Add "alldefconfig" to the explanation of the KCONFIG_ALLCONFIG environment variable usage so that all targets that use KCONFIG_ALLCONFIG are listed. Signed-off-by: Randy Dunlap Signed-off-by: Masahiro Yamada

Merge tag 'kbuild-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2025-06-07T17:05:35+00:00

Pull Kbuild updates from Masahiro Yamada: - Add support for the EXPORT_SYMBOL_GPL_FOR_MODULES() macro, which exports a symbol only to specified modules - Improve ABI handling in gendwarfksyms - Forcibly link lib-y objects to vmlinux even if CONFIG_MODULES=n - Add checkers for redundant or missing inclusion - Deprecate the extra-y syntax - Fix a genksyms bug when including enum constants from *.symref files * tag 'kbuild-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (28 commits) genksyms: Fix enum consts from a reference affecting new values arch: use always-$(KBUILD_BUILTIN) for vmlinux.lds kbuild: set y instead of 1 to KBUILD_{BUILTIN,MODULES} efi/libstub: use 'targets' instead of extra-y in Makefile module: make __mod_device_table__* symbols static scripts/misc-check: check unnecessary #include when W=1 scripts/misc-check: check missing #include when W=1 scripts/misc-check: add double-quotes to satisfy shellcheck kbuild: move W=1 check for scripts/misc-check to top-level Makefile scripts/tags.sh: allow to use alternative ctags implementation kconfig: introduce menu type enum docs: symbol-namespaces: fix reST warning with literal block kbuild: link lib-y objects to vmlinux forcibly even when CONFIG_MODULES=n tinyconfig: enable CONFIG_LD_DEAD_CODE_DATA_ELIMINATION docs/core-api/symbol-namespaces: drop table of contents and section numbering modpost: check forbidden MODULE_IMPORT_NS("module:") at compile time kbuild: move kbuild syntax processing to scripts/Makefile.build Makefile: remove dependency on archscripts for header installation Documentation/kbuild: Add new gendwarfksyms kABI rules Documentation/kbuild: Drop section numbers ...

kbuild: set y instead of 1 to KBUILD_{BUILTIN,MODULES}

2025-06-07T05:37:50+00:00

KBUILD_BUILTIN is set to 1 unless you are building only modules. KBUILD_MODULES is set to 1 when you are building only modules (a typical use case is "make modules"). It is more useful to set them to 'y' instead, so we can do something like: always-$(KBUILD_BUILTIN) += vmlinux.lds This works equivalently to: extra-y += vmlinux.lds This allows us to deprecate extra-y. extra-y and always-y are quite similar, and we do not need both. Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Reviewed-by: Nicolas Schier

Merge tag 'gcc-minimum-version-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2025-05-31T15:16:52+00:00

Pull compiler version requirement update from Arnd Bergmann: "Require gcc-8 and binutils-2.30 x86 already uses gcc-8 as the minimum version, this changes all other architectures to the same version. gcc-8 is used is Debian 10 and Red Hat Enterprise Linux 8, both of which are still supported, and binutils 2.30 is the oldest corresponding version on those. Ubuntu Pro 18.04 and SUSE Linux Enterprise Server 15 both use gcc-7 as the system compiler but additionally include toolchains that remain supported. With the new minimum toolchain versions, a number of workarounds for older versions can be dropped, in particular on x86_64 and arm64. Importantly, the updated compiler version allows removing two of the five remaining gcc plugins, as support for sancov and structeak features is already included in modern compiler versions. I tried collecting the known changes that are possible based on the new toolchain version, but expect that more cleanups will be possible. Since this touches multiple architectures, I merged the patches through the asm-generic tree." * tag 'gcc-minimum-version-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: Makefile.kcov: apply needed compiler option unconditionally in CFLAGS_KCOV Documentation: update binutils-2.30 version reference gcc-plugins: remove SANCOV gcc plugin Kbuild: remove structleak gcc plugin arm64: drop binutils version checks raid6: skip avx512 checks kbuild: require gcc-8 and binutils-2.30

Documentation/kbuild: Add new gendwarfksyms kABI rules

2025-05-25T09:12:23+00:00

Document the "byte_size" and "type_string" kABI stability rules. Signed-off-by: Sami Tolvanen Signed-off-by: Masahiro Yamada

Documentation/kbuild: Drop section numbers

2025-05-25T09:12:23+00:00

Change the gendwarfksyms documentation to use proper chapter, section, and subsection adornments instead of fragile section numbers. Suggested-by: Masahiro Yamada Signed-off-by: Sami Tolvanen Signed-off-by: Masahiro Yamada