kernel/linux.git/Documentation/kbuild/modules.rst, branch linux-7.1.y

documentation: remove references to *_gpl sections

2026-03-31T23:42:52+00:00

*_gpl sections are no longer present in the kernel binary. Signed-off-by: Siddharth Nayyar Reviewed-by: Petr Pavlu Signed-off-by: Sami Tolvanen

Documentation/kbuild: Fix indentation in modules.rst example

2025-03-16T15:29:51+00:00

Correct the indentation in an example within the `modules.rst` file to improve readability. Signed-off-by: Kefan Liu Signed-off-by: Masahiro Yamada

Documentation/kbuild: Document storage of symbol information

2025-01-10T17:36:36+00:00

Document where exported and imported symbols are kept, format options, and limitations. Signed-off-by: Matthew Maurer Signed-off-by: Masahiro Yamada

kbuild: allow to start building external modules in any directory

2024-11-27T23:11:55+00:00

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 Reviewed-by: Nicolas Schier

kbuild: support building external modules in a separate build directory

2024-11-27T23:11:55+00:00

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 M= MO= Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

kbuild: doc: replace "gcc" in external module description

2024-09-23T18:07:21+00:00

Avoid "gcc" since it is not the only compiler supported by Kbuild. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

kbuild: doc: describe the -C option precisely for external module builds

2024-09-23T18:07:21+00:00

Building external modules is typically done using this command: $ make -C M= Here, 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, 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 O= M= 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 Reviewed-by: Nicolas Schier

kbuild: doc: remove the description about shipped files

2024-09-23T18:07:21+00:00

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 Reviewed-by: Nicolas Schier

kbuild: doc: drop section numbering, use references in modules.rst

2024-09-23T18:07:21+00:00

Do similar to commit 1a4c1c9df72e ("docs/kbuild/makefiles: drop section numbering, use references"). Signed-off-by: Masahiro Yamada

kbuild: doc: throw out the local table of contents in modules.rst

2024-09-23T18:07:21+00:00

Do similar to commit 5e8f0ba38a4d ("docs/kbuild/makefiles: throw out the local table of contents"). Signed-off-by: Masahiro Yamada