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2025-06-07Merge tag 'kbuild-v6.16' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild 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 <linux/export.h> 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-$(KBUILD_BUILTIN) for vmlinux.lds kbuild: set y instead of 1 to KBUILD_{BUILTIN,MODULES} efi/libstub: use 'targets' instead of extra-y in Makefile module: make __mod_device_table__* symbols static scripts/misc-check: check unnecessary #include <linux/export.h> when W=1 scripts/misc-check: check missing #include <linux/export.h> when W=1 scripts/misc-check: add double-quotes to satisfy shellcheck kbuild: move W=1 check for scripts/misc-check to top-level Makefile scripts/tags.sh: allow to use alternative ctags implementation kconfig: introduce menu type enum docs: symbol-namespaces: fix reST warning with literal block kbuild: link lib-y objects to vmlinux forcibly even when CONFIG_MODULES=n tinyconfig: enable CONFIG_LD_DEAD_CODE_DATA_ELIMINATION docs/core-api/symbol-namespaces: drop table of contents and section numbering modpost: check forbidden MODULE_IMPORT_NS("module:") at compile time kbuild: move kbuild syntax processing to scripts/Makefile.build Makefile: remove dependency on archscripts for header installation Documentation/kbuild: Add new gendwarfksyms kABI rules Documentation/kbuild: Drop section numbers ...
2025-06-07kbuild: set y instead of 1 to KBUILD_{BUILTIN,MODULES}Masahiro Yamada
KBUILD_BUILTIN is set to 1 unless you are building only modules. KBUILD_MODULES is set to 1 when you are building only modules (a typical use case is "make modules"). It is more useful to set them to 'y' instead, so we can do something like: always-$(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 <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2025-05-31Merge tag 'gcc-minimum-version-6.16' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic 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
2025-05-25Documentation/kbuild: Add new gendwarfksyms kABI rulesSami Tolvanen
Document the "byte_size" and "type_string" kABI stability rules. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-05-25Documentation/kbuild: Drop section numbersSami Tolvanen
Change the gendwarfksyms documentation to use proper chapter, section, and subsection adornments instead of fragile section numbers. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-05-12Revert "kbuild: make all file references relative to source root"Thomas Weißschuh
This reverts commit cacd22ce69585a91c386243cd662ada962431e63. -ffile-prefix-map breaks the ability of debuggers to find the source file corresponding to object files. As there is no simple or uniform way to specify the source directory explicitly, this breaks developers workflows. Revert the unconditional usage of -ffile-prefix-map. Reported-by: Matthieu Baerts <matttbe@kernel.org> Closes: https://lore.kernel.org/lkml/edc50aa7-0740-4942-8c15-96f12f2acc7e@kernel.org/ Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Closes: https://lore.kernel.org/lkml/aBEttQH4kimHFScx@intel.com/ Fixes: cacd22ce6958 ("kbuild: make all file references relative to source root") Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-04-30kbuild: require gcc-8 and binutils-2.30Arnd Bergmann
Commit a3e8fe814ad1 ("x86/build: Raise the minimum GCC version to 8.1") raised the minimum compiler version as enforced by Kbuild to gcc-8.1 and clang-15 for x86. This is actually the same gcc version that has been discussed as the minimum for all architectures several times in the past, with little objection. A previous concern was the kernel for SLE15-SP7 needing to be built with gcc-7. As this ended up still using linux-6.4 and there is no plan for an SP8, this is no longer a problem. Change it for all architectures and adjust the documentation accordingly. A few version checks can be removed in the process. The binutils version 2.30 is the lowest version used in combination with gcc-8 on common distros, so use that as the corresponding minimum. Link: https://lore.kernel.org/lkml/20240925150059.3955569-32-ardb+git@google.com/ Link: https://lore.kernel.org/lkml/871q7yxrgv.wl-tiwai@suse.de/ Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2025-03-22kbuild: make all file references relative to source rootThomas Weißschuh
-fmacro-prefix-map only affects __FILE__ and __BASE_FILE__. Other references, for example in debug information, are not affected. This makes handling of file references in the compiler outputs harder to use and creates problems for reproducible builds. Switch to -ffile-prefix map which affects all references. Also drop the documentation section advising manual specification of -fdebug-prefix-map for reproducible builds, as it is not necessary anymore. Suggested-by: Ben Hutchings <ben@decadent.org.uk> Link: https://lore.kernel.org/lkml/c49cc967294f9a3a4a34f69b6a8727a6d3959ed8.camel@decadent.org.uk/ Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-03-17Documentation/kbuild: Fix indentation in modules.rst exampleKefan Liu
Correct the indentation in an example within the `modules.rst` file to improve readability. Signed-off-by: Kefan Liu <liukefan24s@ict.ac.cn> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-03-15kbuild: add Kbuild bash completionMasahiro Yamada
Kernel build commands can sometimes be long, particularly when cross-compiling, making them tedious to type and prone to mistypes. This commit introduces bash completion support for common variables and targets in Kbuild. For installation instructions, please refer to the documentation in Documentation/kbuild/bash-completion.rst. The following examples demonstrate how this saves typing. [Example 1] a long command line for cross-compiling $ make A<TAB> -> completes 'A' to 'ARCH=' $ make ARCH=<TAB> -> displays all supported architectures $ make ARCH=arm64 CR<TAB> -> completes 'CR' to 'CROSS_COMPILE=' $ make ARCH=arm64 CROSS_COMPILE=<TAB> -> displays installed toolchains $ make ARCH=arm64 CROSS_COMPILE=aa<TAB> -> completes 'CROSS_COMPILE=aa' to 'CROSS_COMPILE=aarch64-linux-gnu-' $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- def<TAB> -> completes 'def' to 'defconfig' [Example 2] a single build target $ make f<TAB> -> completes 'f' to 'fs/' $ make fs/<TAB> -> displays objects and sub-directories in fs/ $ make fs/xf<TAB> -> completes 'fs/xf' to 'fs/xfs/' $ make fs/xfs/l<TAB> -> completes 'fs/xfs/l' to 'fs/xfs/libxfs/xfs_' $ make fs/xfs/libxfs/xfs_g<TAB> -> completes 'fs/xfs/libxfs/xfs_g' to 'fs/xfs/libxfs/xfs_group.o' This does not aim to provide a complete list of variables and targets, as there are too many. However, it covers variables and targets used in common scenarios, and I hope this is useful enough. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de> Tested-by: Nicolas Schier <n.schier@avm.de>
2025-03-15docs: kconfig: Mention IS_REACHABLE as way for optional dependencyKrzysztof Kozlowski
Several drivers express optional Kconfig dependency with FOO || !FOO, but for many choices this is not suitable: lack of stubs for !FOO like in HWMON. Describe the second, less favorable way of optional dependency with IS_REACHABLE by moving the code from "imply" chapter to "Optional dependencies". Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-03-15kbuild: rust: add rustc-min-version support functionMiguel Ojeda
Introduce `rustc-min-version` support function that mimics `{gcc,clang}-min-version` ones, following commit 88b61e3bff93 ("Makefile.compiler: replace cc-ifversion with compiler-specific macros"). In addition, use it in the first use case we have in the kernel (which was done independently to minimize the changes needed for the fix). Signed-off-by: Miguel Ojeda <ojeda@kernel.org> Reviewed-by: Fiona Behrens <me@Kloenk.dev> Reviewed-by: Nicolas Schier <n.schier@avm.de> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-03-15kbuild: remove EXTRA_*FLAGS supportMasahiro Yamada
Commit f77bf01425b1 ("kbuild: introduce ccflags-y, asflags-y and ldflags-y") deprecated these in 2007. The migration should have been completed by now. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <kees@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
2025-01-31Merge tag 'kbuild-v6.14' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Support multiple hook locations for maint scripts of Debian package - Remove 'cpio' from the build tool requirement - Introduce gendwarfksyms tool, which computes CRCs for export symbols based on the DWARF information - Support CONFIG_MODVERSIONS for Rust - Resolve all conflicts in the genksyms parser - Fix several syntax errors in genksyms * tag 'kbuild-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (64 commits) kbuild: fix Clang LTO with CONFIG_OBJTOOL=n kbuild: Strip runtime const RELA sections correctly kconfig: fix memory leak in sym_warn_unmet_dep() kconfig: fix file name in warnings when loading KCONFIG_DEFCONFIG_LIST genksyms: fix syntax error for attribute before init-declarator genksyms: fix syntax error for builtin (u)int*x*_t types genksyms: fix syntax error for attribute after 'union' genksyms: fix syntax error for attribute after 'struct' genksyms: fix syntax error for attribute after abstact_declarator genksyms: fix syntax error for attribute before nested_declarator genksyms: fix syntax error for attribute before abstract_declarator genksyms: decouple ATTRIBUTE_PHRASE from type-qualifier genksyms: record attributes consistently for init-declarator genksyms: restrict direct-declarator to take one parameter-type-list genksyms: restrict direct-abstract-declarator to take one parameter-type-list genksyms: remove Makefile hack genksyms: fix last 3 shift/reduce conflicts genksyms: fix 6 shift/reduce conflicts and 5 reduce/reduce conflicts genksyms: reduce type_qualifier directly to decl_specifier genksyms: rename cvar_qualifier to type_qualifier ...
2025-01-15kbuild: rust: add PROCMACROLDFLAGSHONG Yifan
These are flags to be passed when linking proc macros for the Rust toolchain. If unset, it defaults to $(KBUILD_HOSTLDFLAGS). This is needed because the list of flags to link hostprogs is not necessarily the same as the list of flags used to link libmacros.so. When we build proc macros, we need the latter, not the former (e.g. when using a Rust compiler binary linked to a different C library than host programs). To distinguish between the two, introduce this new variable to stand out from KBUILD_HOSTLDFLAGS used to link other host progs. Signed-off-by: HONG Yifan <elsk@google.com> Link: https://lore.kernel.org/r/20241017210430.2401398-2-elsk@google.com [ v3: - `export`ed the variable. Otherwise it would not be visible in `rust/Makefile`. - Removed "additional" from the documentation and commit message, since this actually replaces the other flags, unlike other cases. - Added example of use case to documentation and commit message. Thanks Alice for the details on what Google needs! - Instead of `HOSTLDFLAGS`, used `KBUILD_HOSTLDFLAGS` as the fallback to preserve the previous behavior as much as possible, as discussed with Alice/Yifan. Thus moved the variable down too (currently we do not modify `KBUILD_HOSTLDFLAGS` elsewhere) and avoided mentioning `HOSTLDFLAGS` directly in the documentation. - Fixed documentation header formatting. - Reworded slightly. - Miguel ] Tested-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: HONG Yifan <elsk@google.com> Acked-by: Masahiro Yamada <masahiroy@kernel.org> Link: https://lore.kernel.org/r/20241112184455.855133-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2025-01-11Documentation/kbuild: Document storage of symbol informationMatthew Maurer
Document where exported and imported symbols are kept, format options, and limitations. Signed-off-by: Matthew Maurer <mmaurer@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2025-01-11Documentation/kbuild: Add DWARF module versioningSami Tolvanen
Add documentation for gendwarfksyms changes, and the kABI stability features that can be useful for distributions even though they're not used in mainline kernels. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-11-30Merge tag 'kbuild-v6.13' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Add generic support for built-in boot DTB files - Enable TAB cycling for dialog buttons in nconfig - Fix issues in streamline_config.pl - Refactor Kconfig - Add support for Clang's AutoFDO (Automatic Feedback-Directed Optimization) - Add support for Clang's Propeller, a profile-guided optimization. - Change the working directory to the external module directory for M= builds - Support building external modules in a separate output directory - Enable objtool for *.mod.o and additional kernel objects - Use lz4 instead of deprecated lz4c - Work around a performance issue with "git describe" - Refactor modpost * tag 'kbuild-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (85 commits) kbuild: rename .tmp_vmlinux.kallsyms0.syms to .tmp_vmlinux0.syms gitignore: Don't ignore 'tags' directory kbuild: add dependency from vmlinux to resolve_btfids modpost: replace tdb_hash() with hash_str() kbuild: deb-pkg: add python3:native to build dependency genksyms: reduce indentation in export_symbol() modpost: improve error messages in device_id_check() modpost: rename alias symbol for MODULE_DEVICE_TABLE() modpost: rename variables in handle_moddevtable() modpost: move strstarts() to modpost.h modpost: convert do_usb_table() to a generic handler modpost: convert do_of_table() to a generic handler modpost: convert do_pnp_device_entry() to a generic handler modpost: convert do_pnp_card_entries() to a generic handler modpost: call module_alias_printf() from all do_*_entry() functions modpost: pass (struct module *) to do_*_entry() functions modpost: remove DEF_FIELD_ADDR_VAR() macro modpost: deduplicate MODULE_ALIAS() for all drivers modpost: introduce module_alias_printf() helper modpost: remove unnecessary check in do_acpi_entry() ...
2024-11-28kbuild: allow to start building external modules in any directoryMasahiro Yamada
Unless an explicit O= option is provided, external module builds must start from the kernel directory. This can be achieved by using the -C option: $ make -C /path/to/kernel M=/path/to/external/module This commit allows starting external module builds from any directory, so you can also do the following: $ make -f /path/to/kernel/Makefile M=/path/to/external/module The key difference is that the -C option changes the working directory and parses the Makefile located there, while the -f option only specifies the Makefile to use. As shown in the examples in Documentation/kbuild/modules.rst, external modules usually have a wrapper Makefile that allows you to build them without specifying any make arguments. The Makefile typically contains a rule as follows: KDIR ?= /path/to/kernel default: $(MAKE) -C $(KDIR) M=$(CURDIR) $(MAKECMDGOALS) The log will appear as follows: $ make make -C /path/to/kernel M=/path/to/external/module make[1]: Entering directory '/path/to/kernel' make[2]: Entering directory '/path/to/external/module' CC [M] helloworld.o MODPOST Module.symvers CC [M] helloworld.mod.o CC [M] .module-common.o LD [M] helloworld.ko make[2]: Leaving directory '/path/to/external/module' make[1]: Leaving directory '/path/to/kernel' This changes the working directory twice because the -C option first switches to the kernel directory, and then Kbuild internally recurses back to the external module directory. With this commit, the wrapper Makefile can directly include the kernel Makefile: KDIR ?= /path/to/kernel export KBUILD_EXTMOD := $(realpath $(dir $(lastword $(MAKEFILE_LIST)))) include $(KDIR)/Makefile This avoids unnecessary sub-make invocations: $ make CC [M] helloworld.o MODPOST Module.symvers CC [M] helloworld.mod.o CC [M] .module-common.o LD [M] helloworld.ko Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2024-11-28kbuild: support building external modules in a separate build directoryMasahiro Yamada
There has been a long-standing request to support building external modules in a separate build directory. This commit introduces a new environment variable, KBUILD_EXTMOD_OUTPUT, and its shorthand Make variable, MO. A simple usage: $ make -C <kernel-dir> M=<module-src-dir> MO=<module-build-dir> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2024-11-28kbuild: change working directory to external module directory with M=Masahiro Yamada
Currently, Kbuild always operates in the output directory of the kernel, even when building external modules. This increases the risk of external module Makefiles attempting to write to the kernel directory. This commit switches the working directory to the external module directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from some build artifacts. The command for building external modules maintains backward compatibility, but Makefiles that rely on working in the kernel directory may break. In such cases, $(objtree) and $(srctree) should be used to refer to the output and source directories of the kernel. The appearance of the build log will change as follows: [Before] $ make -C /path/to/my/linux M=/path/to/my/externel/module make: Entering directory '/path/to/my/linux' CC [M] /path/to/my/externel/module/helloworld.o MODPOST /path/to/my/externel/module/Module.symvers CC [M] /path/to/my/externel/module/helloworld.mod.o CC [M] /path/to/my/externel/module/.module-common.o LD [M] /path/to/my/externel/module/helloworld.ko make: Leaving directory '/path/to/my/linux' [After] $ make -C /path/to/my/linux M=/path/to/my/externel/module make: Entering directory '/path/to/my/linux' make[1]: Entering directory '/path/to/my/externel/module' CC [M] helloworld.o MODPOST Module.symvers CC [M] helloworld.mod.o CC [M] .module-common.o LD [M] helloworld.ko make[1]: Leaving directory '/path/to/my/externel/module' make: Leaving directory '/path/to/my/linux' Printing "Entering directory" twice is cumbersome. This will be addressed later. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-11-16sparc/build: Add SPARC target flags for compiling with clangKoakuma
clang only supports building 64-bit kernel, so we use the sparc64-linux-gnu target. See also: https://lore.kernel.org/lkml/e26PTXUXEz8OYXmaeKn4Mpuejr4IOlFfFwdB5vpsluXlYiqDdlyQTYcDtdAny_o4gO4SfPeQCCN2qpyT6e0nog5EaP3xk2SeUPTrF54p1gM=@protonmail.com/T/#m068e010dcf8b99d3510a90d7532bcdb70e2e2c6b Signed-off-by: Koakuma <koachan@protonmail.com> Acked-by: Masahiro Yamada <masahiroy@kernel.org> Acked-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Andreas Larsson <andreas@gaisler.com> Link: https://lore.kernel.org/r/20241029-sparc-cflags-v3-2-b28745a6bd71@protonmail.com Signed-off-by: Andreas Larsson <andreas@gaisler.com>
2024-11-04kconfig: remove support for "bool" prompt for choice entriesMasahiro Yamada
Since commit fde192511bdb ("kconfig: remove tristate choice support"), all choice blocks are now boolean. There is no longer a need to specify the choice type explicitly. All "bool" prompts in choice entries have been converted to "prompt". This commit removes support for the "bool" syntax in choice entries. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-09-24kbuild: doc: replace "gcc" in external module descriptionMasahiro Yamada
Avoid "gcc" since it is not the only compiler supported by Kbuild. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-09-24kbuild: doc: describe the -C option precisely for external module buildsMasahiro Yamada
Building external modules is typically done using this command: $ make -C <KERNEL_DIR> M=<EXTMOD_DIR> Here, <KERNEL_DIR> refers to the output directory where the kernel was built, not the kernel source directory. When the kernel is built in the source tree, there is no ambiguity, as the output directory and the source directory are the same. If the kernel was built in a separate build directory, <KERNEL_DIR> should be the kernel output directory. Otherwise, Kbuild cannot locate necessary build artifacts. This has been the method for building external modules against a pre-built kernel in a separate directory for over 20 years. [1] If you pass the kernel source directory to the -C option, you must also specify the kernel build directory using the O= option. This approach works as well, though it results in a slightly longer command: $ make -C <KERNEL_SOURCE_DIR> O=<KERNEL_BUILD_DIR> M=<EXTMOD_DIR> Some people mistakenly believe that O= should specify a build directory for external modules when used together with M=. This commit adds more clarification to Documentation/kbuild/kbuild.rst. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=e321b2ec2eb2993b3d0116e5163c78ad923e3c54 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-09-24kbuild: doc: remove the description about shipped filesMasahiro Yamada
The use of shipped files is discouraged in the upstream kernel these days. [1] Downstream Makefiles have the freedom to use shipped files or other options to handle binaries, but this should not be advertised in the upstream document. [1]: https://lore.kernel.org/all/CAHk-=wgSEi_ZrHdqr=20xv+d6dr5G895CbOAi8ok+7-CQUN=fQ@mail.gmail.com/ Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-09-24kbuild: doc: drop section numbering, use references in modules.rstMasahiro Yamada
Do similar to commit 1a4c1c9df72e ("docs/kbuild/makefiles: drop section numbering, use references"). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-09-24kbuild: doc: throw out the local table of contents in modules.rstMasahiro Yamada
Do similar to commit 5e8f0ba38a4d ("docs/kbuild/makefiles: throw out the local table of contents"). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-09-24kbuild: doc: remove outdated description of the limitation on -I usageMasahiro Yamada
Kbuild used to manipulate header search paths, enforcing the odd limitation of "no space after -I". Commit cdd750bfb1f7 ("kbuild: remove 'addtree' and 'flags' magic for header search paths") stopped doing that. This limitation no longer exists. Instead, you need to accurately specify the header search path. (In this case, $(src)/include) Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-09-24kbuild: doc: remove description about grepping CONFIG optionsMasahiro Yamada
This description was added 20 years ago [1]. It does not convey any useful information except for a feeling of nostalgia. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=65e433436b5794ae056d22ddba60fe9194bba007 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-09-24kbuild: doc: update the description about Kbuild/Makefile splitMasahiro Yamada
The phrase "In newer versions of the kernel" was added 14 years ago, by commit efdf02cf0651 ("Documentation/kbuild: major edit of modules.txt sections 1-4"). This feature is no longer new, so remove it and update the paragraph. Example 3 was written 20 years ago [1]. There is no need to note about backward compatibility with such an old build system. Remove Example 3 entirely. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=65e433436b5794ae056d22ddba60fe9194bba007 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-09-20kbuild: generate offset range data for builtin modulesKris Van Hees
Create file module.builtin.ranges that can be used to find where built-in modules are located by their addresses. This will be useful for tracing tools to find what functions are for various built-in modules. The offset range data for builtin modules is generated using: - modules.builtin: associates object files with module names - vmlinux.map: provides load order of sections and offset of first member per section - vmlinux.o.map: provides offset of object file content per section - .*.cmd: build cmd file with KBUILD_MODFILE The generated data will look like: .text 00000000-00000000 = _text .text 0000baf0-0000cb10 amd_uncore .text 0009bd10-0009c8e0 iosf_mbi ... .text 00b9f080-00ba011a intel_skl_int3472_discrete .text 00ba0120-00ba03c0 intel_skl_int3472_discrete intel_skl_int3472_tps68470 .text 00ba03c0-00ba08d6 intel_skl_int3472_tps68470 ... .data 00000000-00000000 = _sdata .data 0000f020-0000f680 amd_uncore For each ELF section, it lists the offset of the first symbol. This can be used to determine the base address of the section at runtime. Next, it lists (in strict ascending order) offset ranges in that section that cover the symbols of one or more builtin modules. Multiple ranges can apply to a single module, and ranges can be shared between modules. The CONFIG_BUILTIN_MODULE_RANGES option controls whether offset range data is generated for kernel modules that are built into the kernel image. How it works: 1. The modules.builtin file is parsed to obtain a list of built-in module names and their associated object names (the .ko file that the module would be in if it were a loadable module, hereafter referred to as <kmodfile>). This object name can be used to identify objects in the kernel compile because any C or assembler code that ends up into a built-in module will have the option -DKBUILD_MODFILE=<kmodfile> present in its build command, and those can be found in the .<obj>.cmd file in the kernel build tree. If an object is part of multiple modules, they will all be listed in the KBUILD_MODFILE option argument. This allows us to conclusively determine whether an object in the kernel build belong to any modules, and which. 2. The vmlinux.map is parsed next to determine the base address of each top level section so that all addresses into the section can be turned into offsets. This makes it possible to handle sections getting loaded at different addresses at system boot. We also determine an 'anchor' symbol at the beginning of each section to make it possible to calculate the true base address of a section at runtime (i.e. symbol address - symbol offset). We collect start addresses of sections that are included in the top level section. This is used when vmlinux is linked using vmlinux.o, because in that case, we need to look at the vmlinux.o linker map to know what object a symbol is found in. And finally, we process each symbol that is listed in vmlinux.map (or vmlinux.o.map) based on the following structure: vmlinux linked from vmlinux.a: vmlinux.map: <top level section> <included section> -- might be same as top level section) <object> -- built-in association known <symbol> -- belongs to module(s) object belongs to ... vmlinux linked from vmlinux.o: vmlinux.map: <top level section> <included section> -- might be same as top level section) vmlinux.o -- need to use vmlinux.o.map <symbol> -- ignored ... vmlinux.o.map: <section> <object> -- built-in association known <symbol> -- belongs to module(s) object belongs to ... 3. As sections, objects, and symbols are processed, offset ranges are constructed in a straight-forward way: - If the symbol belongs to one or more built-in modules: - If we were working on the same module(s), extend the range to include this object - If we were working on another module(s), close that range, and start the new one - If the symbol does not belong to any built-in modules: - If we were working on a module(s) range, close that range Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com> Reviewed-by: Nick Alcock <nick.alcock@oracle.com> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Tested-by: Sam James <sam@gentoo.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-09-07Documentation: kconfig: explicitly document missing promptStephen Brennan
There are a few lines in the kbuild-language.rst document which obliquely reference the behavior of config options without prompts. But there is nothing in the obvious location that explicitly calls out that users cannot edit config options unless they have a prompt. Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-08-16Documentation/llvm: turn make command for ccache into code blockJavier Carrasco
The command provided to use ccache with clang is not a literal code block. Once built, the documentation displays the '' symbols as a " character, which is wrong, and the command can not be applied as provided. Turn the command into a literal code block. Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-07-24kbuild: doc: gcc to CC changeIvan Davydov
In this part of the documentation, $(CC) is meant, but gcc is written. Signed-off-by: Ivan Davydov <davydoff33@yandex.ru> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-07-16kconfig: remove tristate choice supportMasahiro Yamada
I previously submitted a fix for a bug in the choice feature [1], where I mentioned, "Another (much cleaner) approach would be to remove the tristate choice support entirely". There are more issues in the tristate choice feature. For example, you can observe a couple of bugs in the following test code. [Test Code] config MODULES def_bool y modules choice prompt "tristate choice" default A config A tristate "A" config B tristate "B" endchoice Bug 1: the 'default' property is not correctly processed 'make alldefconfig' produces: CONFIG_MODULES=y # CONFIG_A is not set # CONFIG_B is not set However, the correct output should be: CONFIG_MODULES=y CONFIG_A=y # CONFIG_B is not set The unit test file, scripts/kconfig/tests/choice/alldef_expected_config, is wrong as well. Bug 2: choice members never get 'y' with randconfig For the test code above, the following combinations are possible: A B (1) y n (2) n y (3) m m (4) m n (5) n m (6) n n 'make randconfig' never produces (1) or (2). These bugs are fixable, but a more critical problem is the lack of a sensible syntax to specify the default for the tristate choice. The default for the choice must be one of the choice members, which cannot specify any of the patterns (3) through (6) above. In addition, I have never seen it being used in a useful way. The following commits removed unnecessary use of tristate choices: - df8df5e4bc37 ("usb: get rid of 'choice' for legacy gadget drivers") - bfb57ef0544a ("rapidio: remove choice for enumeration") This commit removes the tristate choice support entirely, which allows me to delete a lot of code, making further refactoring easier. Note: This includes the revert of commit fa64e5f6a35e ("kconfig/symbol.c: handle choice_values that depend on 'm' symbols"). It was suspicious because it did not address the root cause but introduced inconsistency in visibility between choice members and other symbols. [1]: https://lore.kernel.org/linux-kbuild/20240427104231.2728905-1-masahiroy@kernel.org/T/#m0a1bb6992581462ceca861b409bb33cb8fd7dbae Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2024-06-26kbuild: doc: Update default INSTALL_MOD_DIR from extra to updatesMark-PK Tsai
The default INSTALL_MOD_DIR was changed from 'extra' to 'updates' in commit b74d7bb7ca24 ("kbuild: Modify default INSTALL_MOD_DIR from extra to updates"). This commit updates the documentation to align with the latest kernel. Fixes: b74d7bb7ca24 ("kbuild: Modify default INSTALL_MOD_DIR from extra to updates") Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-06-06kconfig: doc: document behavior of 'select' and 'imply' followed by 'if'Masahiro Yamada
Documentation/kbuild/kconfig-language.rst explains the behavior of 'select' as follows: reverse dependencies can be used to force a lower limit of another symbol. The value of the current menu symbol is used as the minimal value <symbol> can be set to. This is not true when the 'select' property is followed by 'if'. [Test Code] config MODULES def_bool y modules config A def_tristate y select C if B config B def_tristate m config C tristate [Result] CONFIG_MODULES=y CONFIG_A=y CONFIG_B=m CONFIG_C=m If "the value of A is used as the minimal value C can be set to", C must be 'y'. The actual behavior is "C is selected by (A && B)". The lower limit of C is downgraded due to B being 'm'. This behavior is kind of weird, and this has arisen several times in the mailing list. I do not know whether it is a bug or intended behavior. Anyway, it is not feasible to change it now because many Kconfig files are written based on this behavior. The same applies to 'imply'. Document this (but reserve the possibility for a future change). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
2024-06-06kconfig: doc: fix a typo in the note about 'imply'Masahiro Yamada
This sentence does not make sense due to a typo. Fix it. Fixes: def2fbffe62c ("kconfig: allow symbols implied by y to become m") Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
2024-05-10kbuild: use $(src) instead of $(srctree)/$(src) for source directoryMasahiro Yamada
Kbuild conventionally uses $(obj)/ for generated files, and $(src)/ for checked-in source files. It is merely a convention without any functional difference. In fact, $(obj) and $(src) are exactly the same, as defined in scripts/Makefile.build: src := $(obj) When the kernel is built in a separate output directory, $(src) does not accurately reflect the source directory location. While Kbuild resolves this discrepancy by specifying VPATH=$(srctree) to search for source files, it does not cover all cases. For example, when adding a header search path for local headers, -I$(srctree)/$(src) is typically passed to the compiler. This introduces inconsistency between upstream and downstream Makefiles because $(src) is used instead of $(srctree)/$(src) for the latter. To address this inconsistency, this commit changes the semantics of $(src) so that it always points to the directory in the source tree. Going forward, the variables used in Makefiles will have the following meanings: $(obj) - directory in the object tree $(src) - directory in the source tree (changed by this commit) $(objtree) - the top of the kernel object tree $(srctree) - the top of the kernel source tree Consequently, $(srctree)/$(src) in upstream Makefiles need to be replaced with $(src). Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2024-05-02kconfig: remove 'optional' property supportMasahiro Yamada
The 'choice' statement is primarily used to exclusively select one option, but the 'optional' property allows all entries to be disabled. In the following example, both A and B can be disabled simultaneously: choice prompt "choose A, B, or nothing" optional config A bool "A" config B bool "B" endchoice You can achieve the equivalent outcome by other means. A common solution is to add another option to guard the choice block. In the following example, you can set ENABLE_A_B_CHOICE=n to disable the entire choice block: choice prompt "choose A or B" depends on ENABLE_A_B_CHOICE config A bool "A" config B bool "B" endchoice Another approach is to insert one more entry: choice prompt "choose A, B, or disable both" config A bool "A" config B bool "B" config DISABLE_A_AND_B bool "choose this to disable both A and B" endchoice Some real examples are DEBUG_INFO_NONE, INITRAMFS_COMPRESSION_NONE, LTO_NONE, etc. The 'optional' property is even more unnecessary for a tristate choice. Without the 'optional' property, you can disable A and B; you can set 'm' in the choice prompt, and disable A and B individually: choice prompt "choose one built-in or make them modular" config A tristate "A" config B tristate "B" endchoice In conclusion, the 'optional' property was unneeded. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <n.schier@avm.de>
2024-03-31Documentation/llvm: Note s390 LLVM=1 support with LLVM 18.1.0 and newerNathan Chancellor
As of the first s390 pull request during the 6.9 merge window, commit 691632f0e869 ("Merge tag 's390-6.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux"), s390 can be built with LLVM=1 when using LLVM 18.1.0, which is the first version that has SystemZ support implemented in ld.lld and llvm-objcopy. Update the supported architectures table in the Kbuild LLVM documentation to note this explicitly to make it more discoverable by users and other developers. Additionally, this brings s390 in line with the rest of the architectures in the table, which all support LLVM=1. Signed-off-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-03-10kconfig: remove named choice supportMasahiro Yamada
Commit 5a1aa8a1aff6 ("kconfig: add named choice group") did not provide enough explanation regarding its benefits. A use case was found in another project [1] sometime later, this feature has never been used in the kernel. [1]: https://lore.kernel.org/all/201012150034.01356.yann.morin.1998@anciens.enib.fr/ Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2024-02-19docs: kbuild/kconfig: reformat/cleanupVegard Nossum
This document was using headings in an odd way, causing the sidebar to be quite messy. I've adding new headings and turned some of the old headings into description lists. The indentation was a mix of spaces and tabs; I've turned them all into 4 spaces so it always reads correctly regardless of tab settings. Also use ``...`` instead of `...`; the difference is that `` is meant for "inline literals" (and renders in a monospace font) while ` is for "interpreted text" (and renders with italics). Also changed the title of the document to be more descriptive. Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2024-02-15docs: kconfig: Fix grammar and formattingThorsten Blum
- Remove unnecessary spaces - Fix grammar s/to solution/solution/ Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-11-04Merge tag 'kbuild-v6.7' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild Pull Kbuild updates from Masahiro Yamada: - Implement the binary search in modpost for faster symbol lookup - Respect HOSTCC when linking host programs written in Rust - Change the binrpm-pkg target to generate kernel-devel RPM package - Fix endianness issues for tee and ishtp MODULE_DEVICE_TABLE - Unify vdso_install rules - Remove unused __memexit* annotations - Eliminate stale whitelisting for __devinit/__devexit from modpost - Enable dummy-tools to handle the -fpatchable-function-entry flag - Add 'userldlibs' syntax * tag 'kbuild-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (30 commits) kbuild: support 'userldlibs' syntax kbuild: dummy-tools: pretend we understand -fpatchable-function-entry kbuild: Correct missing architecture-specific hyphens modpost: squash ALL_{INIT,EXIT}_TEXT_SECTIONS to ALL_TEXT_SECTIONS modpost: merge sectioncheck table entries regarding init/exit sections modpost: use ALL_INIT_SECTIONS for the section check from DATA_SECTIONS modpost: disallow the combination of EXPORT_SYMBOL and __meminit* modpost: remove EXIT_SECTIONS macro modpost: remove MEM_INIT_SECTIONS macro modpost: remove more symbol patterns from the section check whitelist modpost: disallow *driver to reference .meminit* sections linux/init: remove __memexit* annotations modpost: remove ALL_EXIT_DATA_SECTIONS macro kbuild: simplify cmd_ld_multi_m kbuild: avoid too many execution of scripts/pahole-flags.sh kbuild: remove ARCH_POSTLINK from module builds kbuild: unify no-compiler-targets and no-sync-config-targets kbuild: unify vdso_install rules docs: kbuild: add INSTALL_DTBS_PATH UML: remove unused cmd_vdso_install ...
2023-11-01Merge tag 'asm-generic-6.7' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic Pull ia64 removal and asm-generic updates from Arnd Bergmann: - The ia64 architecture gets its well-earned retirement as planned, now that there is one last (mostly) working release that will be maintained as an LTS kernel. - The architecture specific system call tables are updated for the added map_shadow_stack() syscall and to remove references to the long-gone sys_lookup_dcookie() syscall. * tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic: hexagon: Remove unusable symbols from the ptrace.h uapi asm-generic: Fix spelling of architecture arch: Reserve map_shadow_stack() syscall number for all architectures syscalls: Cleanup references to sys_lookup_dcookie() Documentation: Drop or replace remaining mentions of IA64 lib/raid6: Drop IA64 support Documentation: Drop IA64 from feature descriptions kernel: Drop IA64 support from sig_fault handlers arch: Remove Itanium (IA-64) architecture
2023-11-01kbuild: support 'userldlibs' syntaxMasahiro Yamada
This syntax is useful to specify libraries linked to all userspace programs in the Makefile. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-10-18docs: kbuild: add INSTALL_DTBS_PATHRicardo B. Marliere
The documentation for kbuild and makefiles is missing an explanation of a variable important for some architectures. Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-09-25Documentation: kbuild: explain handling optional dependenciesArnd Bergmann
This problem frequently comes up in randconfig testing, with drivers failing to link because of a dependency on an optional feature. The Kconfig language for this is very confusing, so try to document it in "Kconfig hints" section. Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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