Re: [PATCH v2 2/3] bootconfig: Support embedding a bootconfig file in kernel

Padmanabha Srinivasaiah
2022-03-16T19:16:55Z

Hello Masami Hiramatsu,

On Mon, Mar 14, 2022 at 06:08:41PM +0900, Masami Hiramatsu 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@kernel.org>
> ---
> include/linux/bootconfig.h | 10 ++++++++++
> init/Kconfig | 21 +++++++++++++++++++++
> init/main.c | 13 ++++++++-----
> lib/.gitignore | 1 +
> lib/Makefile | 12 ++++++++++++
> lib/bootconfig.c | 23 +++++++++++++++++++++++
> 6 files changed, 75 insertions(+), 5 deletions(-)
>
> 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 e9119bf54b1f..70440804874d 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1357,6 +1357,27 @@ 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 421050be5039..3803bf2e22ea 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -265,7 +265,7 @@ 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;
> @@ -411,12 +411,15 @@ 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,
> @@ -435,8 +438,8 @@ 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;
> }
>
> @@ -449,7 +452,7 @@ 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..30a2a5db7033 100644
> --- a/lib/.gitignore
> +++ b/lib/.gitignore
> @@ -6,3 +6,4 @@
> /oid_registry_data.c
> /test_fortify.log
> /test_fortify/*.log
> +/default.bconf
> diff --git a/lib/Makefile b/lib/Makefile
> index 300f569c626b..8183785ee99d 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -279,6 +279,18 @@ $(foreach file, $(libfdt_files), \
> $(eval CFLAGS_$(file) = -I $(srctree)/scripts/dtc/libfdt))
> lib-$(CONFIG_LIBFDT) += $(libfdt_files)
>
> +ifeq ($(CONFIG_EMBED_BOOT_CONFIG),y)
> +# Since the specified bootconfig file can be switched, we forcibly update the
> +# default.bconf file always.
> +$(obj)/default.bconf: FORCE
> + $(call cmd,defbconf)
> +
> +quiet_cmd_defbconf = GEN $@
> + cmd_defbconf = cat < /dev/null $(CONFIG_EMBED_BOOT_CONFIG_FILE) > $@
> +clean-files += default.bconf
> +$(obj)/bootconfig.o: $(obj)/default.bconf
> +endif
> +
> lib-$(CONFIG_BOOT_CONFIG) += bootconfig.o
>
> obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
> diff --git a/lib/bootconfig.c b/lib/bootconfig.c
> index 74f3201ab8e5..3a3bf3a208e3 100644
> --- a/lib/bootconfig.c
> +++ b/lib/bootconfig.c
> @@ -12,6 +12,29 @@
> #include <linux/kernel.h>
> #include <linux/memblock.h>
> #include <linux/string.h>
> +
> +#ifdef CONFIG_EMBED_BOOT_CONFIG
> +asm (
> +" .pushsection .init.data, \"aw\" \n"
> +" .global embedded_bootconfig_data \n"
> +"embedded_bootconfig_data: \n"
> +" .incbin \"lib/default.bconf\" \n"
> +" .global embedded_bootconfig_data_end \n"
> +"embedded_bootconfig_data_end: \n"
> +" .popsection \n"
> +);
> +
> +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
>

Thanks tested the implemation, it works as expected.

Also noted that a change in default.bconf requries a clean build, is it
expected behaviour?

Thanks and Regards,
Padmanabha.S