[PATCH 0/3] bootconfig: Support embedding a bootconfig in kernel for non initrd boot

[PATCH 0/3] bootconfig: Support embedding a bootconfig in kernel for non initrd boot

[Masami Hiramatsu]

Hi,

Here are the patchset to enable kernel embedded bootconfig for non-initrd
kernel boot environment. 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_EMBED_BOOT_CONFIG=y and set the file
path to CONFIG_EMBED_BOOT_CONFIG_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).

This is requested by Padmanabha at the below thread;

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

Thank you,

---

Masami Hiramatsu (3):
      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 +++++++++++++++++++++++++++---
 include/linux/bootconfig.h               |   10 ++++++++++
 init/Kconfig                             |   21 ++++++++++++++++++++
 init/main.c                              |   31 +++++++++++++++---------------
 lib/.gitignore                           |    1 +
 lib/Makefile                             |   12 ++++++++++++
 lib/bootconfig.c                         |   23 ++++++++++++++++++++++
 7 files changed, 111 insertions(+), 18 deletions(-)

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

[PATCH 1/3] 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 65fa2e41a9c0..421050be5039 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, u32 *_csum)
+static void * __init get_boot_config_from_initrd(u32 *_size)
 {
 	u32 size, csum;
 	char *data;
@@ -299,17 +299,20 @@ 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;
 }
@@ -408,12 +411,12 @@ 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,
@@ -437,11 +440,6 @@ 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)
@@ -470,7 +468,7 @@ 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 2/3] 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 2 options: 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. And if you boot with the initrd which has another
bootconfig, the kernel will use the bootconfig in the initrd, instead
of embedding one.

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

[PATCH 3/3] 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>
---
 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..a172c669997a 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 2 options to boot the kernel with bootconfig, one is attaching
+bootconfig to initrd image, and embedding 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 to the
+kernel by Kconfig options. In This case, you need to recompile the kernel
+with the following configs::
+
+ COFNIG_EMBED_BOOT_CONFIG=y
+ CONFIG_EMBED_BOOT_CONFIG_FILE="/PATH/TO/BOOTCONFIG/FILE"
+
+You need to set the correct path (relative path from kernel build directory
+or absolute path) to the ``CONFIG_EMBED_BOOT_CONFIG_FILE`` option.
+Then the kernel will embed the bootconfig file as a default bootconfig.
+
+As same as attaching to initrd, you need ``bootconfig`` option to 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
 =================================

Re: [PATCH 3/3] docs: bootconfig: Add how to embed the bootconfig into kernel

[Randy Dunlap]

Hi--

On 3/13/22 06:56, Masami Hiramatsu wrote:
> Add a description how to embed the bootconfig file into kernel.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  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..a172c669997a 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 2 options to boot the kernel with bootconfig, one is attaching
> +bootconfig to initrd image, and embedding the kernel itself.

  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 to the

                                                                     in the

> +kernel by Kconfig options. In This case, you need to recompile the kernel

                                 this

> +with the following configs::
> +
> + COFNIG_EMBED_BOOT_CONFIG=y
> + CONFIG_EMBED_BOOT_CONFIG_FILE="/PATH/TO/BOOTCONFIG/FILE"
> +
> +You need to set the correct path (relative path from kernel build directory
> +or absolute path) to the ``CONFIG_EMBED_BOOT_CONFIG_FILE`` option.
> +Then the kernel will embed the bootconfig file as a default bootconfig.
> +
> +As same as attaching to initrd, you need ``bootconfig`` option to the

  Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` option to 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
>  =================================
> 

HTH.

-- 
~Randy

Re: [PATCH 3/3] docs: bootconfig: Add how to embed the bootconfig into kernel

[Masami Hiramatsu]

Hi Randy,

Thanks for the review and fix! 
I also found that CONFIG_EMBED_BOOT_CONFIG_FILE should be an absolute path
(for example, if the kernel is built with O=DIR option, the relative path will
 be interpreted from the build directory (DIR/lib) but that is too complicated.)
So I'll update this document.

Thank you!

On Sun, 13 Mar 2022 10:52:35 -0700
Randy Dunlap <rdunlap@infradead.org> wrote:

> Hi--
> 
> On 3/13/22 06:56, Masami Hiramatsu wrote:
> > Add a description how to embed the bootconfig file into kernel.
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> >  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..a172c669997a 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 2 options to boot the kernel with bootconfig, one is attaching
> > +bootconfig to initrd image, and embedding the kernel itself.
> 
>   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 to the
> 
>                                                                      in the
> 
> > +kernel by Kconfig options. In This case, you need to recompile the kernel
> 
>                                  this
> 
> > +with the following configs::
> > +
> > + COFNIG_EMBED_BOOT_CONFIG=y
> > + CONFIG_EMBED_BOOT_CONFIG_FILE="/PATH/TO/BOOTCONFIG/FILE"
> > +
> > +You need to set the correct path (relative path from kernel build directory
> > +or absolute path) to the ``CONFIG_EMBED_BOOT_CONFIG_FILE`` option.
> > +Then the kernel will embed the bootconfig file as a default bootconfig.
> > +
> > +As same as attaching to initrd, you need ``bootconfig`` option to the
> 
>   Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` option to 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
> >  =================================
> > 
> 
> HTH.
> 
> -- 
> ~Randy


-- 
Masami Hiramatsu <mhiramat@kernel.org>