On Wed, 4 Jan 2023 16:58:38 -0800 "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote: > The BOOT_CONFIG family of Kconfig options allows a bootconfig file > containing kernel boot parameters to be embedded into an initrd or into > the kernel itself. This can be extremely useful when deploying kernels > in cases where some of the boot parameters depend on the kernel version > rather than on the server hardware, firmware, or workload. > > Unfortunately, the "bootconfig" kernel parameter must be specified in > order to cause the kernel to look for the embedded bootconfig file, > and it clearly does not help to embed this "bootconfig" kernel parameter > into that file. > > Therefore, provide a new BOOT_CONFIG_FORCE Kconfig option that causes the > kernel to act as if the "bootconfig" kernel parameter had been specified. > In other words, kernels built with CONFIG_BOOT_CONFIG_FORCE=y will look > for the embedded bootconfig file even when the "bootconfig" kernel > parameter is omitted. This permits kernel-version-dependent kernel > boot parameters to be embedded into the kernel image without the need to > (for example) update large numbers of boot loaders. > I like this because this is a simple solution. We have another option to specify "bootconfig" in CONFIG_CMDLINE, but it can be overwritten by bootloader. Thus, it is better to have this option so that user can always enable bootconfig. Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> BTW, maybe CONFIG_BOOT_CONFIG_EMBED is better to select this. (or at least recommend to enable this) Thank you! > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Cc: Jonathan Corbet <corbet@xxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Cc: Vlastimil Babka <vbabka@xxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: <linux-doc@xxxxxxxxxxxxxxx> > > diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst > index 9355c525fbe0a..91339efdcb541 100644 > --- a/Documentation/admin-guide/bootconfig.rst > +++ b/Documentation/admin-guide/bootconfig.rst > @@ -201,6 +201,8 @@ To remove the config from the image, you can use -d option as below:: > > Then add "bootconfig" on the normal kernel command line to tell the > kernel to look for the bootconfig at the end of the initrd file. > +Alternatively, build your kernel with the ``CONFIG_BOOT_CONFIG_FORCE`` > +Kconfig option selected. > > Embedding a Boot Config into Kernel > ----------------------------------- > @@ -217,7 +219,9 @@ path to the bootconfig file from source tree or object tree. > The kernel will embed it as the default bootconfig. > > Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` > -option on the kernel command line to enable the embedded bootconfig. > +option on the kernel command line to enable the embedded bootconfig, or, > +alternatively, build your kernel with the ``CONFIG_BOOT_CONFIG_FORCE`` > +Kconfig option selected. > > Note that even if you set this option, you can override the embedded > bootconfig by another bootconfig which attached to the initrd. > diff --git a/init/Kconfig b/init/Kconfig > index 7e5c3ddc341de..f894fb004bad4 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1376,6 +1376,18 @@ config BOOT_CONFIG > > If unsure, say Y. > > +config BOOT_CONFIG_FORCE > + bool "Force unconditional bootconfig processing" > + depends on BOOT_CONFIG > + help > + With this Kconfig option set, BOOT_CONFIG processing is carried > + out even when the "bootconfig" kernel-boot parameter is omitted. > + In fact, with this Kconfig option set, there is no way to > + make the kernel ignore the BOOT_CONFIG-supplied kernel-boot > + parameters. > + > + If unsure, say N. > + > config BOOT_CONFIG_EMBED > bool "Embed bootconfig file in the kernel" > depends on BOOT_CONFIG > diff --git a/init/main.c b/init/main.c > index e1c3911d7c707..669cb892e6c17 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -156,7 +156,7 @@ static char *extra_init_args; > > #ifdef CONFIG_BOOT_CONFIG > /* Is bootconfig on command line? */ > -static bool bootconfig_found; > +static bool bootconfig_found = IS_ENABLED(CONFIG_BOOT_CONFIG_FORCE); > static size_t initargs_offs; > #else > # define bootconfig_found false -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
