[PATCH v7 0/4] bootconfig: Support embedding a bootconfig in kernel for non initrd boot

[PATCH v7 0/4] bootconfig: Support embedding a bootconfig in kernel for non initrd boot

[Masami Hiramatsu]

Hi,

Here are the 7th version of the patchset to enable kernel embedded bootconfig
for non-initrd kernel boot environment. This version renames the Kconfig
options, make the embedded data readonly, fixes some issues.
Here is the previous version [1].

[1] https://lore.kernel.org/all/164870615889.127053.9055569952366814752.stgit@devnote2/T/#u

You can embed a bootconfig file into the kernel as a default bootconfig,
which will be used if there is no initrd or no bootconfig is attached to initrd. 

This needs 2 options: CONFIG_BOOT_CONFIG_EMBED=y and set the file
path to CONFIG_BOOT_CONFIG_EMBED_FILE. Even if you embed the bootconfig file
to the kernel, it will not be enabled unless you pass "bootconfig" kernel
command line option at boot. Moreover, since this is just a "default"
bootconfig, you can override it with a new bootconfig if you attach another
bootconfig to the initrd (if possible).
The CONFIG_BOOT_CONFIG_EMBED_FILE can take both absolute and relative path.

This is requested by Padmanabha at the below thread[2];

[2] https://lore.kernel.org/all/20220307184011.GA2570@pswork/T/#u

This had an issue about incremental build and LTO THIN mode issue because
of using '.incbin' directive in inline asm. Now it is solved by separating
it as an asm file.

Thank you,

---

Masami Hiramatsu (4):
      bootconfig: Make the bootconfig.o as a normal object file
      bootconfig: Check the checksum before removing the bootconfig from initrd
      bootconfig: Support embedding a bootconfig file in kernel
      docs: bootconfig: Add how to embed the bootconfig into kernel


 Documentation/admin-guide/bootconfig.rst |   31 ++++++++++++++++++++++--
 MAINTAINERS                              |    1 +
 include/linux/bootconfig.h               |   10 ++++++++
 init/Kconfig                             |   21 ++++++++++++++++-
 init/main.c                              |   38 +++++++++++++++---------------
 lib/.gitignore                           |    1 +
 lib/Makefile                             |   10 +++++++-
 lib/bootconfig-data.S                    |   10 ++++++++
 lib/bootconfig.c                         |   13 ++++++++++
 9 files changed, 111 insertions(+), 24 deletions(-)
 create mode 100644 lib/bootconfig-data.S

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>

[PATCH v7 1/4] bootconfig: Make the bootconfig.o as a normal object file

[Masami Hiramatsu]

Since the APIs defined in the bootconfig.o are not individually used,
it is meaningless to build it as library by lib-y. Use obj-y for that.

Reported-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v6:
  - Newly added.
---
 lib/Makefile |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/Makefile b/lib/Makefile
index 6b9ffc1bd1ee..08053df16c7c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -279,7 +279,7 @@ $(foreach file, $(libfdt_files), \
 	$(eval CFLAGS_$(file) = -I $(srctree)/scripts/dtc/libfdt))
 lib-$(CONFIG_LIBFDT) += $(libfdt_files)
 
-lib-$(CONFIG_BOOT_CONFIG) += bootconfig.o
+obj-$(CONFIG_BOOT_CONFIG) += bootconfig.o
 
 obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
 obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o

[PATCH v7 2/4] bootconfig: Check the checksum before removing the bootconfig from initrd

[Masami Hiramatsu]

Check the bootconfig's checksum before removing the bootcinfig data
from initrd to avoid modifying initrd by mistake.
This will also simplifies the get_boot_config_from_initrd() interface.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 init/main.c |   22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/init/main.c b/init/main.c
index 98182c3c2c4b..266d61bc67b0 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, u32 *_csum)
+static void * __init get_boot_config_from_initrd(u32 *_size)
 {
 	u32 size, csum;
 	char *data;
@@ -300,17 +300,20 @@ static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
 		return NULL;
 	}
 
+	if (xbc_calc_checksum(data, size) != csum) {
+		pr_err("bootconfig checksum failed\n");
+		return NULL;
+	}
+
 	/* Remove bootconfig from initramfs/initrd */
 	initrd_end = (unsigned long)data;
 	if (_size)
 		*_size = size;
-	if (_csum)
-		*_csum = csum;
 
 	return data;
 }
 #else
-static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
+static void * __init get_boot_config_from_initrd(u32 *_size)
 {
 	return NULL;
 }
@@ -409,12 +412,12 @@ static void __init setup_boot_config(void)
 	static char tmp_cmdline[COMMAND_LINE_SIZE] __initdata;
 	const char *msg;
 	int pos;
-	u32 size, csum;
+	u32 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, &csum);
+	data = get_boot_config_from_initrd(&size);
 
 	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
 	err = parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
@@ -438,11 +441,6 @@ static void __init setup_boot_config(void)
 		return;
 	}
 
-	if (xbc_calc_checksum(data, size) != csum) {
-		pr_err("bootconfig checksum failed\n");
-		return;
-	}
-
 	ret = xbc_init(data, size, &msg, &pos);
 	if (ret < 0) {
 		if (pos < 0)
@@ -471,7 +469,7 @@ static void __init exit_boot_config(void)
 static void __init setup_boot_config(void)
 {
 	/* Remove bootconfig data from initrd */
-	get_boot_config_from_initrd(NULL, NULL);
+	get_boot_config_from_initrd(NULL);
 }
 
 static int __init warn_bootconfig(char *str)

[PATCH v7 3/4] bootconfig: Support embedding a bootconfig file in kernel

[Masami Hiramatsu]

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@kernel.org>
---
 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                |   20 +++++++++++---------
 lib/.gitignore             |    1 +
 lib/Makefile               |    8 ++++++++
 lib/bootconfig-data.S      |   10 ++++++++++
 lib/bootconfig.c           |   13 +++++++++++++
 8 files changed, 74 insertions(+), 10 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..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 97463a33baa7..756872d17fe1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1351,7 +1351,7 @@ 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.
@@ -1361,6 +1361,25 @@ 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 266d61bc67b0..62dddc4206b4 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;
@@ -410,14 +410,16 @@ 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,
@@ -436,8 +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;
 	}
 
@@ -450,7 +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..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..95268d6c75b7 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_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

Re: [PATCH v7 3/4] bootconfig: Support embedding a bootconfig file in kernel

[Masami Hiramatsu]

Hi Steve,

Have you already picked this series?

Actually, kernel test robot reported an issue in this patch today.
Here is the patch. Should I send v8 including this?

Thank you,

diff --git a/init/main.c b/init/main.c
index 62dddc4206b4..f7fe7cbb1df8 100644
--- a/init/main.c
+++ b/init/main.c
@@ -313,7 +313,7 @@ static void * __init get_boot_config_from_initrd(size_t *_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;
 }

On Thu, 31 Mar 2022 17:24:51 +0900
Masami Hiramatsu <mhiramat@kernel.org> 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@kernel.org>
> ---
>  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                |   20 +++++++++++---------
>  lib/.gitignore             |    1 +
>  lib/Makefile               |    8 ++++++++
>  lib/bootconfig-data.S      |   10 ++++++++++
>  lib/bootconfig.c           |   13 +++++++++++++
>  8 files changed, 74 insertions(+), 10 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..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 97463a33baa7..756872d17fe1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1351,7 +1351,7 @@ 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.
> @@ -1361,6 +1361,25 @@ 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 266d61bc67b0..62dddc4206b4 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;
> @@ -410,14 +410,16 @@ 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,
> @@ -436,8 +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;
>  	}
>  
> @@ -450,7 +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..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..95268d6c75b7 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-$(CONFIG_BOOT_CONFIG_EMBED) += bootconfig-data.o
> +
> +$(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
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH v7 3/4] bootconfig: Support embedding a bootconfig file in kernel

[Steven Rostedt]

On Tue, 5 Apr 2022 23:55:48 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Have you already picked this series?

No I haven't. I do not add any patches until after the merge window, which
just ended Sunday.

> 
> Actually, kernel test robot reported an issue in this patch today.
> Here is the patch. Should I send v8 including this?

Yes, please send a v8.

Thanks!

-- Steve

Re: [PATCH v7 3/4] bootconfig: Support embedding a bootconfig file in kernel

[Masami Hiramatsu]

On Tue, 5 Apr 2022 11:02:43 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 5 Apr 2022 23:55:48 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > Have you already picked this series?
> 
> No I haven't. I do not add any patches until after the merge window, which
> just ended Sunday.
> 
> > 
> > Actually, kernel test robot reported an issue in this patch today.
> > Here is the patch. Should I send v8 including this?
> 
> Yes, please send a v8.

OK, thanks for the confirmation!
Let me send v8.

Thanks!

> 
> Thanks!
> 
> -- Steve


-- 
Masami Hiramatsu <mhiramat@kernel.org>

[PATCH v7 4/4] docs: bootconfig: Add how to embed the bootconfig into kernel

[Masami Hiramatsu]

Add a description how to embed the bootconfig file into kernel.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Changes in v7:
  - Rename CONFIG_EMBED_BOOT_CONFIG* to CONFIG_BOOT_CONFIG_EMBED*.
 Changes in v5:
  - Update CONFIG_EMBED_BOOT_CONFIG_FILE which can accept relative path.
 Changes in v3:
  - Fix typos.
 Changes in v2:
  - Corrected the text accoding to Randy's suggestion.
  - Do not reccomend to use relative path for CONFIG_EMBED_BOOT_CONFIG_FILE.
---
 Documentation/admin-guide/bootconfig.rst |   31 +++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index a1860fc0ca88..d99994345d41 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -158,9 +158,15 @@ Each key-value pair is shown in each line with following style::
 Boot Kernel With a Boot Config
 ==============================
 
-Since the boot configuration file is loaded with initrd, it will be added
-to the end of the initrd (initramfs) image file with padding, size,
-checksum and 12-byte magic word as below.
+There are two options to boot the kernel with bootconfig: attaching the
+bootconfig to the initrd image or embedding it in the kernel itself.
+
+Attaching a Boot Config to Initrd
+---------------------------------
+
+Since the boot configuration file is loaded with initrd by default,
+it will be added to the end of the initrd (initramfs) image file with
+padding, size, checksum and 12-byte magic word as below.
 
 [initrd][bootconfig][padding][size(le32)][checksum(le32)][#BOOTCONFIG\n]
 
@@ -196,6 +202,25 @@ 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.
 
+Embedding a Boot Config into Kernel
+-----------------------------------
+
+If you can not use initrd, you can also embed the bootconfig file in the
+kernel by Kconfig options. In this case, you need to recompile the kernel
+with the following configs::
+
+ CONFIG_BOOT_CONFIG_EMBED=y
+ CONFIG_BOOT_CONFIG_EMBED_FILE="/PATH/TO/BOOTCONFIG/FILE"
+
+``CONFIG_BOOT_CONFIG_EMBED_FILE`` requires an absolute path or a relative
+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.
+
+Note that even if you set this option, you can override the embedded
+bootconfig by another bootconfig which attached to the initrd.
 
 Kernel parameters via Boot Config
 =================================