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Date: Wed, 13 Apr 2022 15:34:50 +0200
From: Padmanabha Srinivasaiah <treasure4paddy@...il.com>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
LKML <linux-kernel@...r.kernel.org>,
Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
Randy Dunlap <rdunlap@...radead.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev,
Masahiro Yamada <masahiroy@...nel.org>,
Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v8 3/4] bootconfig: Support embedding a bootconfig file
in kernel
Hello Masami Hiramatsu,
On Wed, Apr 06, 2022 at 11:31:19AM +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_BOOT_CONFIG_EMBED=y and set
> the file path to CONFIG_BOOT_CONFIG_EMBED_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@...nel.org>
> ---
> Changes in v8:
> - Fix a build error in CONFIG_BLK_DEV_INITRD=n case.
> Changes in v7:
> - Change kconfig option name to share the common prefix so that
> we can search it easier.
> - Make embedded_bootconfig_data readonly.
> - Select CONFIG_BLK_DEV_INITRD only if CONFIG_BOOT_CONFIG_EMBED=n
> - Remove redundant default settings for new Kconfig options.
> 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 | 22 ++++++++++++----------
> lib/.gitignore | 1 +
> lib/Makefile | 8 ++++++++
> lib/bootconfig-data.S | 10 ++++++++++
> lib/bootconfig.c | 13 +++++++++++++
> 8 files changed, 75 insertions(+), 11 deletions(-)
> create mode 100644 lib/bootconfig-data.S
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c10fbd13080a..88c9d62acd90 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7318,6 +7318,7 @@ 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..1611f9db878e 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_BOOT_CONFIG_EMBED
> +const char * __init xbc_get_embedded_bootconfig(size_t *size);
> +#else
> +static inline const char *xbc_get_embedded_bootconfig(size_t *size)
> +{
> + return NULL;
> +}
> +#endif
> +
> #endif
> diff --git a/init/Kconfig b/init/Kconfig
> index beb5b866c318..e7c75fb7d244 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1347,7 +1347,7 @@ endif
>
> config BOOT_CONFIG
> bool "Boot config support"
> - select BLK_DEV_INITRD
> + select BLK_DEV_INITRD if !BOOT_CONFIG_EMBED
> help
> Extra boot config allows system admin to pass a config file as
> complemental extension of kernel cmdline when booting.
> @@ -1357,6 +1357,25 @@ config BOOT_CONFIG
>
> If unsure, say Y.
>
> +config BOOT_CONFIG_EMBED
> + bool "Embed bootconfig file in the kernel"
> + depends on BOOT_CONFIG
> + help
> + Embed a bootconfig file given by BOOT_CONFIG_EMBED_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 BOOT_CONFIG_EMBED_FILE
> + string "Embedded bootconfig file path"
> + depends on BOOT_CONFIG_EMBED
> + 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 4f3ba3b84e34..d00c6f77d0e0 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;
> @@ -312,7 +312,7 @@ static void * __init get_boot_config_from_initrd(u32 *_size)
> return data;
> }
> #else
> -static void * __init get_boot_config_from_initrd(u32 *_size)
> +static void * __init get_boot_config_from_initrd(size_t *_size)
> {
> return NULL;
> }
> @@ -409,14 +409,16 @@ static int __init warn_bootconfig(char *str)
> static void __init setup_boot_config(void)
> {
> static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
> - const char *msg;
> - int pos;
> - u32 size;
> - char *data, *err;
> - int ret;
> + const char *msg, *data;
> + int pos, ret;
> + size_t size;
> + char *err;
>
> /* 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 +437,8 @@ 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 +451,7 @@ 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 4fc48543dc8f..62a103aaabd4 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -277,6 +277,14 @@ $(foreach file, $(libfdt_files), \
> lib-$(CONFIG_LIBFDT) += $(libfdt_files)
>
> obj-$(CONFIG_BOOT_CONFIG) += bootconfig.o
> +obj-$(CONFIG_BOOT_CONFIG_EMBED) += bootconfig-data.o
> +
> +$(obj)/bootconfig-data.o: $(obj)/default.bconf
> +
> +targets += default.bconf
> +filechk_defbconf = cat $(or $(real-prereqs), /dev/null)
> +$(obj)/default.bconf: $(CONFIG_BOOT_CONFIG_EMBED_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..ef85ba1a82f4
> --- /dev/null
> +++ b/lib/bootconfig-data.S
> @@ -0,0 +1,10 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Embed default bootconfig in the kernel.
> + */
> + .section .init.rodata, "aw"
> + .global embedded_bootconfig_data
> +embedded_bootconfig_data:
> + .incbin "lib/default.bconf"
> + .global embedded_bootconfig_data_end
> +embedded_bootconfig_data_end:
> diff --git a/lib/bootconfig.c b/lib/bootconfig.c
> index 74f3201ab8e5..c59d26068a64 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_BOOT_CONFIG_EMBED
> +/* embedded_bootconfig_data is defined in bootconfig-data.S */
> +extern __visible const char embedded_bootconfig_data[];
> +extern __visible const char embedded_bootconfig_data_end[];
> +
> +const 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
>
Tested using llvm 15.0.0 [p1] with FULL and THIN LTO as suggested here [p2],
with full and incremental builds results are as expected and no issues
observed.
[p1] https://download.01.org/0day-ci/cross-package/clang-latest/clang-latest/clang.tar.xz
[p2] https://lore.kernel.org/lkml/20220327115526.cc4b0ff55fc53c97683c3e4d@kernel.org/
Thanks and Regards,
Padmanabha.S
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