On Thu, 31 Mar 2022 15:27:56 +0900
Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
> On Thu, Mar 31, 2022 at 2:56 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> >
> > This allows kernel developer to embed a default bootconfig file in
> > the kernel instead of embedding it in the initrd. This will be good
> > for who are using the kernel without initrd, or who needs a default
> > bootconfigs.
> > This needs to set two kconfigs: CONFIG_EMBED_BOOT_CONFIG=y and set
> > the file path to CONFIG_EMBED_BOOT_CONFIG_FILE.
> >
> > Note that you still need 'bootconfig' command line option to load the
> > embedded bootconfig. Also if you boot using an initrd with a different
> > bootconfig, the kernel will use the bootconfig in the initrd, instead
> > of the default bootconfig.
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > ---
> > Changes in v6:
> > - Split out the .incbin asm part as bootconfig-data.S according to
> > Masahiro's comment.
> > Changes in v5:
> > - Fix .gitignore to be sorted alphabetically.
> > - Make default.bconf is cleaned up correctly.
> > - Allow user to specify relative path to CONFIG_EMBED_BOOT_CONFIG_FILE.
> > (Thanks Masahiro!)
> > Changes in v4:
> > - Avoid updating the default.bconf if the file is not changed.
> > ---
> > MAINTAINERS | 1 +
> > include/linux/bootconfig.h | 10 ++++++++++
> > init/Kconfig | 21 +++++++++++++++++++++
> > init/main.c | 13 ++++++++-----
> > lib/.gitignore | 1 +
> > lib/Makefile | 8 ++++++++
> > lib/bootconfig-data.S | 11 +++++++++++
> > lib/bootconfig.c | 13 +++++++++++++
> > 8 files changed, 73 insertions(+), 5 deletions(-)
> > create mode 100644 lib/bootconfig-data.S
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index b555a5e8704f..9b4910685412 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -7350,6 +7350,7 @@ S: Maintained
> > F: Documentation/admin-guide/bootconfig.rst
> > F: fs/proc/bootconfig.c
> > F: include/linux/bootconfig.h
> > +F: lib/bootconfig-data.S
> > F: lib/bootconfig.c
> > F: tools/bootconfig/*
> > F: tools/bootconfig/scripts/*
> > diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
> > index a4665c7ab07c..5dbda5e3e9bb 100644
> > --- a/include/linux/bootconfig.h
> > +++ b/include/linux/bootconfig.h
> > @@ -289,4 +289,14 @@ int __init xbc_get_info(int *node_size, size_t *data_size);
> > /* XBC cleanup data structures */
> > void __init xbc_exit(void);
> >
> > +/* XBC embedded bootconfig data in kernel */
> > +#ifdef CONFIG_EMBED_BOOT_CONFIG
> > +char * __init xbc_get_embedded_bootconfig(size_t *size);
> > +#else
> > +static inline char *xbc_get_embedded_bootconfig(size_t *size)
> > +{
> > + return NULL;
> > +}
> > +#endif
> > +
> > #endif
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 97463a33baa7..f5d14a78cfce 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1361,6 +1361,27 @@ config BOOT_CONFIG
> >
> > If unsure, say Y.
> >
> > +config EMBED_BOOT_CONFIG
> > + bool "Embed bootconfig file in the kernel"
> > + depends on BOOT_CONFIG
> > + default n
> > + help
> > + Embed a bootconfig file given by EMBED_BOOT_CONFIG_FILE in the
> > + kernel. Usually, the bootconfig file is loaded with the initrd
> > + image. But if the system doesn't support initrd, this option will
> > + help you by embedding a bootconfig file while building the kernel.
> > +
> > + If unsure, say N.
> > +
> > +config EMBED_BOOT_CONFIG_FILE
> > + string "Embedded bootconfig file path"
> > + default ""
> > + depends on EMBED_BOOT_CONFIG
> > + help
> > + Specify a bootconfig file which will be embedded to the kernel.
> > + This bootconfig will be used if there is no initrd or no other
> > + bootconfig in the initrd.
> > +
> > choice
> > prompt "Compiler optimization level"
> > default CC_OPTIMIZE_FOR_PERFORMANCE
> > diff --git a/init/main.c b/init/main.c
> > index 266d61bc67b0..a5db3e36b809 100644
> > --- a/init/main.c
> > +++ b/init/main.c
> > @@ -266,7 +266,7 @@ static int __init loglevel(char *str)
> > early_param("loglevel", loglevel);
> >
> > #ifdef CONFIG_BLK_DEV_INITRD
> > -static void * __init get_boot_config_from_initrd(u32 *_size)
> > +static void * __init get_boot_config_from_initrd(size_t *_size)
> > {
> > u32 size, csum;
> > char *data;
> > @@ -412,12 +412,15 @@ static void __init setup_boot_config(void)
> > static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
> > const char *msg;
> > int pos;
> > - u32 size;
> > + size_t size;
> > char *data, *err;
> > int ret;
> >
> > /* Cut out the bootconfig data even if we have no bootconfig option */
> > data = get_boot_config_from_initrd(&size);
> > + /* If there is no bootconfig in initrd, try embedded one. */
> > + if (!data)
> > + data = xbc_get_embedded_bootconfig(&size);
> >
> > strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
> > err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
> > @@ -436,8 +439,8 @@ static void __init setup_boot_config(void)
> > }
> >
> > if (size >= XBC_DATA_MAX) {
> > - pr_err("bootconfig size %d greater than max size %d\n",
> > - size, XBC_DATA_MAX);
> > + pr_err("bootconfig size %ld greater than max size %d\n",
> > + (long)size, XBC_DATA_MAX);
> > return;
> > }
> >
> > @@ -450,7 +453,7 @@ static void __init setup_boot_config(void)
> > msg, pos);
> > } else {
> > xbc_get_info(&ret, NULL);
> > - pr_info("Load bootconfig: %d bytes %d nodes\n", size, ret);
> > + pr_info("Load bootconfig: %ld bytes %d nodes\n", (long)size, ret);
> > /* keys starting with "kernel." are passed via cmdline */
> > extra_command_line = xbc_make_cmdline("kernel");
> > /* Also, "init." keys are init arguments */
> > diff --git a/lib/.gitignore b/lib/.gitignore
> > index e5e217b8307b..54596b634ecb 100644
> > --- a/lib/.gitignore
> > +++ b/lib/.gitignore
> > @@ -1,6 +1,7 @@
> > # SPDX-License-Identifier: GPL-2.0-only
> > /crc32table.h
> > /crc64table.h
> > +/default.bconf
> > /gen_crc32table
> > /gen_crc64table
> > /oid_registry_data.c
> > diff --git a/lib/Makefile b/lib/Makefile
> > index 08053df16c7c..2a82cc324f91 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -280,6 +280,14 @@ $(foreach file, $(libfdt_files), \
> > lib-$(CONFIG_LIBFDT) += $(libfdt_files)
> >
> > obj-$(CONFIG_BOOT_CONFIG) += bootconfig.o
> > +obj-$(CONFIG_EMBED_BOOT_CONFIG) += bootconfig-data.o
> > +
> > +$(obj)/bootconfig-data.o: $(obj)/default.bconf
> > +
> > +targets += default.bconf
> > +filechk_defbconf = cat $(or $(real-prereqs), /dev/null)
> > +$(obj)/default.bconf: $(CONFIG_EMBED_BOOT_CONFIG_FILE) FORCE
> > + $(call filechk,defbconf)
> >
> > obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
> > obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
> > diff --git a/lib/bootconfig-data.S b/lib/bootconfig-data.S
> > new file mode 100644
> > index 000000000000..df674ea7d8be
> > --- /dev/null
> > +++ b/lib/bootconfig-data.S
> > @@ -0,0 +1,11 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Embed default bootconfig in the kernel.
> > + */
> > + .pushsection .init.data, "aw"
> > + .global embedded_bootconfig_data
> > +embedded_bootconfig_data:
> > + .incbin "lib/default.bconf"
> > + .global embedded_bootconfig_data_end
> > +embedded_bootconfig_data_end:
> > + .popsection
>
>
>
> You used .pushsection / .popsection because it was
> previously located in bootconfig.c, where there are
> functions, which should go to the ".text" section.
Oops, yes. I have made a dumb copy from the inline asm...
> Now that you split this into a separate compilation unit,
> there is only one ".init.data" section in the file.
>
>
> .section .init.data, "aw"
>
> should be enough.
OK.
> BTW, is it reasonable/possible to make it explicitly read-only?
>
> I have not tested this patch at all. Nor do I have enough insight.
>
> .section .init.rodata, "a"
>
> I am not sure whether this is possible or not.
Yes, it can be. The data is passed via 'const char *'.
>
>
>
> Some more nits:
>
> default n
>
> default ""
>
> are the redundant defaults in Kconfig.
Thanks for that information. Let me remove those lines. :)
>
>
>
>
> Personally, I prefer seeing the common prefix
> for options that belong to the same group,
> for example,
>
> CONFIG_BOOT_CONFIG
> CONFIG_BOOT_CONFIG_EMBED
> CONFIG_BOOT_CONFIG_EMBEDDED_FILE
>
>
> But, this is something like "up to you" things.
Good comment. OK, I'll change it next version.
Thank you!
>
>
>
>
>
>
>
> > diff --git a/lib/bootconfig.c b/lib/bootconfig.c
> > index 74f3201ab8e5..6d30aee85ebe 100644
> > --- a/lib/bootconfig.c
> > +++ b/lib/bootconfig.c
> > @@ -12,6 +12,19 @@
> > #include <linux/kernel.h>
> > #include <linux/memblock.h>
> > #include <linux/string.h>
> > +
> > +#ifdef CONFIG_EMBED_BOOT_CONFIG
> > +/* embedded_bootconfig_data is defined in bootconfig-data.S */
> > +extern __visible char embedded_bootconfig_data[];
> > +extern __visible char embedded_bootconfig_data_end[];
> > +
> > +char * __init xbc_get_embedded_bootconfig(size_t *size)
> > +{
> > + *size = embedded_bootconfig_data_end - embedded_bootconfig_data;
> > + return (*size) ? embedded_bootconfig_data : NULL;
> > +}
> > +#endif
> > +
> > #else /* !__KERNEL__ */
> > /*
> > * NOTE: This is only for tools/bootconfig, because tools/bootconfig will
> >
>
>
> --
> Best Regards
> Masahiro Yamada
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
