Date: Fri, 26 Jun 2026 00:46:20 +0000 From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: d946a88e0ce3 - main - build.7: explain how to build KBI-compatible standalone module Message-ID: <6a3dcbdc.3dd8f.2ca4a8c@gitrepo.freebsd.org>
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The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=d946a88e0ce347a9a6fdbfdae0b23ef192b9bddc commit d946a88e0ce347a9a6fdbfdae0b23ef192b9bddc Author: Konstantin Belousov <kib@FreeBSD.org> AuthorDate: 2026-06-26 00:21:36 +0000 Commit: Konstantin Belousov <kib@FreeBSD.org> CommitDate: 2026-06-26 00:44:46 +0000 build.7: explain how to build KBI-compatible standalone module Reviewed by: imp, kevans Sponsored by: The FreeBSD Foundation MFC after: 3 days Differential revision: https://reviews.freebsd.org/D57859 --- share/man/man7/build.7 | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/share/man/man7/build.7 b/share/man/man7/build.7 index 9db04f12c15a..0ec12cf33cbc 100644 --- a/share/man/man7/build.7 +++ b/share/man/man7/build.7 @@ -1116,6 +1116,46 @@ Rebuild and reinstall a single loadable kernel module, in this case cd /usr/src/sys/modules/sound make all install clean cleandepend KMODDIR=/boot/kernel .Ed +.Pp +Important detail is that the kernel binary interface is affected +by its configuration. +Modules build outside of the regular kernel build procedure still +must be built against the target kernel configuration, which is +defined by the set of the +.Pa opt_*.h +headers generated by +.Xr config 8 . +Use the +.Va KERNBUILDDIR +variable to point the module build to the configured kernel. +There is no need to actually build the configured kernel in +that directory, module build only consumes the headers from it. +.Pp +Additionally, the +.Va SYSDIR +environment variable may be useful to point to specific kernel source +tree used to build the target kernel, since the kernel headers +define the binary interface for modules. +.Pp +Assuming that the +.Fx +sources are located in the +.Pa /home/user/src +directory, the used kernel config is named +.Vd MY_KERNEL +and that the module sources are in +.Pa my-module +directory, the following sequence of the commands would populate +.Pa /home/user/my-kernel-builddir +directory with the +.Pa opt_*.h +headers and then build the module compatible with +.Vd MY_KERNEL . +.Bd -literal -offset -indent +config -d /home/user/my-kernel-builddir -s /home/user/src/sys/amd64/conf MY-KERNEL +cd my-module +make all KERNBUILDDIR=/home/user/my-kernel-builddir SYSDIR +.Ed .Ss Example 5: Quickly rebuild a kernel in place Quickly rebuild and reinstall the kernel, only recompiling the files changed since last build; note that this will only work if the fullhome | help
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