[PATCH 0/2] tools/bootconfig: Align the bootconfig applied initrd

[PATCH 0/2] tools/bootconfig: Align the bootconfig applied initrd

[Masami Hiramatsu]

Hi,

This updates bootconfig tool to align the total size of initrd + 
bootconfig to 4. To adjust the file size, the bootconfig tool
adds padding null characters in between the boot configuration
data and the footer.

This series include Documentation update. The changing points are
- The bootconfig applied initrd image size is aligned to 4.
- To insert the padding null ('\0') bytes, the size in the footer
  can be bigger than the actual bootconfig file size.
- But the max size of the boot configuration file is same, because
  the max size doesn't include the last null characters.

For this version I decided to keep 4 bytes aligned rather than
longer size. It will be easy to expand it to e.g. 32 bytes (in this
series, we just need to update 3 locations of the code), but I
couldn't find any reason to expand it. Only I could found was
that the grub can align the filesize to 4, and U-Boot/EDK2 will
not change it. So I couldn't say what is the best size.

Anyway, I updated the documentation too, which clearly says that
the above changing points, and if the bootloader pass the wrong
size, kernel will not find bootconfig from the initrd.

Thank you,

---

Masami Hiramatsu (2):
      tools/bootconfig: Align the bootconfig applied initrd image size to 4
      Documentation: bootconfig: Update file format on initrd image


 Documentation/admin-guide/bootconfig.rst |   18 ++++++++++++----
 include/linux/bootconfig.h               |    1 +
 tools/bootconfig/main.c                  |   33 +++++++++++++++++++++++++-----
 tools/bootconfig/test-bootconfig.sh      |    6 +++++
 4 files changed, 47 insertions(+), 11 deletions(-)

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

[PATCH 1/2] tools/bootconfig: Align the bootconfig applied initrd image size to 4

[Masami Hiramatsu]

Align the bootconfig applied initrd image size to 4. To pad the data,
bootconfig will use space (0x20) in front of the bootconfig data,
and expands its size and update checksum.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 include/linux/bootconfig.h          |    1 +
 tools/bootconfig/main.c             |   33 ++++++++++++++++++++++++++++-----
 tools/bootconfig/test-bootconfig.sh |    6 +++++-
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
index 9903088891fa..461f621047f3 100644
--- a/include/linux/bootconfig.h
+++ b/include/linux/bootconfig.h
@@ -12,6 +12,7 @@
 
 #define BOOTCONFIG_MAGIC	"#BOOTCONFIG\n"
 #define BOOTCONFIG_MAGIC_LEN	12
+#define BOOTCONFIG_ALIGN	4
 
 /* XBC tree node */
 struct xbc_node {
diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c
index eb92027817a7..4b48e6a5ad1b 100644
--- a/tools/bootconfig/main.c
+++ b/tools/bootconfig/main.c
@@ -332,11 +332,13 @@ static int delete_xbc(const char *path)
 
 static int apply_xbc(const char *path, const char *xbc_path)
 {
+	const char padbuf[BOOTCONFIG_ALIGN] = { 0 };
 	u32 size, csum;
 	char *buf, *data;
 	int ret, fd;
 	const char *msg;
-	int pos;
+	struct stat st;
+	int pos, pad;
 
 	ret = load_xbc_file(xbc_path, &buf);
 	if (ret < 0) {
@@ -347,12 +349,10 @@ static int apply_xbc(const char *path, const char *xbc_path)
 	csum = checksum((unsigned char *)buf, size);
 
 	/* Prepare xbc_path data */
-	data = malloc(size + 8);
+	data = malloc(size);
 	if (!data)
 		return -ENOMEM;
 	strcpy(data, buf);
-	*(u32 *)(data + size) = size;
-	*(u32 *)(data + size + 4) = csum;
 
 	/* Check the data format */
 	ret = xbc_init(buf, &msg, &pos);
@@ -387,12 +387,35 @@ static int apply_xbc(const char *path, const char *xbc_path)
 		free(data);
 		return fd;
 	}
+
+	/* To algin up the total size to BOOTCONFIG_ALIGN, get padding size */
+	ret = fstat(fd, &st);
+	if (ret < 0) {
+		pr_err("Failed to get the stat of %s\n", path);
+		free(data);
+		return ret;
+	}
+	pad = BOOTCONFIG_ALIGN - (st.st_size + size) % BOOTCONFIG_ALIGN;
+
 	/* TODO: Ensure the @path is initramfs/initrd image */
-	ret = write(fd, data, size + 8);
+	ret = write(fd, data, size);
 	if (ret < 0) {
 		pr_err("Failed to apply a boot config: %d\n", ret);
 		goto out;
 	}
+
+	if (pad != BOOTCONFIG_ALIGN) {
+		/* Write padding null characters */
+		ret = write(fd, padbuf, pad);
+		if (ret < 0) {
+			pr_err("Failed to write padding: %d\n", ret);
+			goto out;
+		}
+		size += pad;
+	}
+	ret = write(fd, &size, sizeof(u32));
+	ret = write(fd, &csum, sizeof(u32));
+
 	/* Write a magic word of the bootconfig */
 	ret = write(fd, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN);
 	if (ret < 0) {
diff --git a/tools/bootconfig/test-bootconfig.sh b/tools/bootconfig/test-bootconfig.sh
index d295e406a756..baed891d0ba4 100755
--- a/tools/bootconfig/test-bootconfig.sh
+++ b/tools/bootconfig/test-bootconfig.sh
@@ -9,6 +9,7 @@ else
   TESTDIR=.
 fi
 BOOTCONF=${TESTDIR}/bootconfig
+ALIGN=4
 
 INITRD=`mktemp ${TESTDIR}/initrd-XXXX`
 TEMPCONF=`mktemp ${TESTDIR}/temp-XXXX.bconf`
@@ -59,7 +60,10 @@ echo "Show command test"
 xpass $BOOTCONF $INITRD
 
 echo "File size check"
-xpass test $new_size -eq $(expr $bconf_size + $initrd_size + 9 + 12)
+total_size=$(expr $bconf_size + $initrd_size + 9 + 12 + $ALIGN - 1 )
+total_size=$(expr $total_size / $ALIGN)
+total_size=$(expr $total_size \* $ALIGN)
+xpass test $new_size -eq $total_size
 
 echo "Apply command repeat test"
 xpass $BOOTCONF -a $TEMPCONF $INITRD

[PATCH 2/2] Documentation: bootconfig: Update file format on initrd image

[Masami Hiramatsu]

To align the total file size, add padding null character when appending
the bootconfig to initrd image.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 Documentation/admin-guide/bootconfig.rst |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index a22024f9175e..363599683784 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -137,15 +137,22 @@ 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 size, checksum and
-12-byte magic word as below.
+to the end of the initrd (initramfs) image file with padding, size,
+checksum and 12-byte magic word as below.
 
-[initrd][bootconfig][size(u32)][checksum(u32)][#BOOTCONFIG\n]
+[initrd][bootconfig][padding][size(u32)][checksum(u32)][#BOOTCONFIG\n]
+
+When the boot configuration is added to the initrd image, the total
+file size is aligned to 4 bytes. To fill the gap, null characters
+(``\0``) will be added. Thus the ``size`` is the length of the bootconfig
+file + padding bytes.
 
 The Linux kernel decodes the last part of the initrd image in memory to
 get the boot configuration data.
 Because of this "piggyback" method, there is no need to change or
-update the boot loader and the kernel image itself.
+update the boot loader and the kernel image itself as long as the boot
+loader passes the correct initrd file size. If by any chance, the boot
+loader passes a longer size, the kernel feils to find the bootconfig data.
 
 To do this operation, Linux kernel provides "bootconfig" command under
 tools/bootconfig, which allows admin to apply or delete the config file
@@ -176,7 +183,8 @@ up to 512 key-value pairs. If keys contains 3 words in average, it can
 contain 256 key-value pairs. In most cases, the number of config items
 will be under 100 entries and smaller than 8KB, so it would be enough.
 If the node number exceeds 1024, parser returns an error even if the file
-size is smaller than 32KB.
+size is smaller than 32KB. (Note that this maximum size is not including
+the padding null characters.)
 Anyway, since bootconfig command verifies it when appending a boot config
 to initrd image, user can notice it before boot.
 

Re: [PATCH 1/2] tools/bootconfig: Align the bootconfig applied initrd image size to 4

[Masami Hiramatsu]

On Tue, 17 Nov 2020 00:05:53 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Align the bootconfig applied initrd image size to 4. To pad the data,
> bootconfig will use space (0x20) in front of the bootconfig data,
> and expands its size and update checksum.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  include/linux/bootconfig.h          |    1 +
>  tools/bootconfig/main.c             |   33 ++++++++++++++++++++++++++++-----
>  tools/bootconfig/test-bootconfig.sh |    6 +++++-
>  3 files changed, 34 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
> index 9903088891fa..461f621047f3 100644
> --- a/include/linux/bootconfig.h
> +++ b/include/linux/bootconfig.h
> @@ -12,6 +12,7 @@
>  
>  #define BOOTCONFIG_MAGIC	"#BOOTCONFIG\n"
>  #define BOOTCONFIG_MAGIC_LEN	12
> +#define BOOTCONFIG_ALIGN	4
>  
>  /* XBC tree node */
>  struct xbc_node {
> diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c
> index eb92027817a7..4b48e6a5ad1b 100644
> --- a/tools/bootconfig/main.c
> +++ b/tools/bootconfig/main.c
> @@ -332,11 +332,13 @@ static int delete_xbc(const char *path)
>  
>  static int apply_xbc(const char *path, const char *xbc_path)
>  {
> +	const char padbuf[BOOTCONFIG_ALIGN] = { 0 };
>  	u32 size, csum;
>  	char *buf, *data;
>  	int ret, fd;
>  	const char *msg;
> -	int pos;
> +	struct stat st;
> +	int pos, pad;
>  
>  	ret = load_xbc_file(xbc_path, &buf);
>  	if (ret < 0) {
> @@ -347,12 +349,10 @@ static int apply_xbc(const char *path, const char *xbc_path)
>  	csum = checksum((unsigned char *)buf, size);
>  
>  	/* Prepare xbc_path data */
> -	data = malloc(size + 8);
> +	data = malloc(size);
>  	if (!data)
>  		return -ENOMEM;
>  	strcpy(data, buf);
> -	*(u32 *)(data + size) = size;
> -	*(u32 *)(data + size + 4) = csum;
>  
>  	/* Check the data format */
>  	ret = xbc_init(buf, &msg, &pos);
> @@ -387,12 +387,35 @@ static int apply_xbc(const char *path, const char *xbc_path)
>  		free(data);
>  		return fd;
>  	}
> +
> +	/* To algin up the total size to BOOTCONFIG_ALIGN, get padding size */
> +	ret = fstat(fd, &st);
> +	if (ret < 0) {
> +		pr_err("Failed to get the stat of %s\n", path);
> +		free(data);
> +		return ret;
> +	}
> +	pad = BOOTCONFIG_ALIGN - (st.st_size + size) % BOOTCONFIG_ALIGN;

Oops, I forgot to add the footer size. This will work for 4 byte alignment,
but doesn't work 8 bytes or larger.
I'll send v2 soon.

Thank you,


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH 1/2] tools/bootconfig: Align the bootconfig applied initrd image size to 4

[Woody Suwalski]

Masami Hiramatsu wrote:
> Align the bootconfig applied initrd image size to 4. To pad the data,
> bootconfig will use space (0x20) in front of the bootconfig data,
> and expands its size and update checksum.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>   include/linux/bootconfig.h          |    1 +
>   tools/bootconfig/main.c             |   33 ++++++++++++++++++++++++++++-----
>   tools/bootconfig/test-bootconfig.sh |    6 +++++-
>   3 files changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h
> index 9903088891fa..461f621047f3 100644
> --- a/include/linux/bootconfig.h
> +++ b/include/linux/bootconfig.h
> @@ -12,6 +12,7 @@
>   
>   #define BOOTCONFIG_MAGIC	"#BOOTCONFIG\n"
>   #define BOOTCONFIG_MAGIC_LEN	12
> +#define BOOTCONFIG_ALIGN	4
>   
>   /* XBC tree node */
>   struct xbc_node {
> diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c
> index eb92027817a7..4b48e6a5ad1b 100644
> --- a/tools/bootconfig/main.c
> +++ b/tools/bootconfig/main.c
> @@ -332,11 +332,13 @@ static int delete_xbc(const char *path)
>   
>   static int apply_xbc(const char *path, const char *xbc_path)
>   {
> +	const char padbuf[BOOTCONFIG_ALIGN] = { 0 };
>   	u32 size, csum;
>   	char *buf, *data;
>   	int ret, fd;
>   	const char *msg;
> -	int pos;
> +	struct stat st;
> +	int pos, pad;
>   
>   	ret = load_xbc_file(xbc_path, &buf);
>   	if (ret < 0) {
> @@ -347,12 +349,10 @@ static int apply_xbc(const char *path, const char *xbc_path)
>   	csum = checksum((unsigned char *)buf, size);
>   
>   	/* Prepare xbc_path data */
> -	data = malloc(size + 8);
> +	data = malloc(size);
>   	if (!data)
>   		return -ENOMEM;
>   	strcpy(data, buf);
> -	*(u32 *)(data + size) = size;
> -	*(u32 *)(data + size + 4) = csum;
>   
>   	/* Check the data format */
>   	ret = xbc_init(buf, &msg, &pos);
> @@ -387,12 +387,35 @@ static int apply_xbc(const char *path, const char *xbc_path)
>   		free(data);
>   		return fd;
>   	}
> +
> +	/* To algin up the total size to BOOTCONFIG_ALIGN, get padding size */
> +	ret = fstat(fd, &st);
> +	if (ret < 0) {
> +		pr_err("Failed to get the stat of %s\n", path);
> +		free(data);
> +		return ret;
> +	}
> +	pad = BOOTCONFIG_ALIGN - (st.st_size + size) % BOOTCONFIG_ALIGN;
> +
>   	/* TODO: Ensure the @path is initramfs/initrd image */
> -	ret = write(fd, data, size + 8);
> +	ret = write(fd, data, size);
>   	if (ret < 0) {
>   		pr_err("Failed to apply a boot config: %d\n", ret);
>   		goto out;
>   	}
> +
> +	if (pad != BOOTCONFIG_ALIGN) {
> +		/* Write padding null characters */
> +		ret = write(fd, padbuf, pad);
> +		if (ret < 0) {
> +			pr_err("Failed to write padding: %d\n", ret);
> +			goto out;
> +		}
> +		size += pad;
> +	}
> +	ret = write(fd, &size, sizeof(u32));
> +	ret = write(fd, &csum, sizeof(u32));
> +
>   	/* Write a magic word of the bootconfig */
>   	ret = write(fd, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN);
>   	if (ret < 0) {
> diff --git a/tools/bootconfig/test-bootconfig.sh b/tools/bootconfig/test-bootconfig.sh
> index d295e406a756..baed891d0ba4 100755
> --- a/tools/bootconfig/test-bootconfig.sh
> +++ b/tools/bootconfig/test-bootconfig.sh
> @@ -9,6 +9,7 @@ else
>     TESTDIR=.
>   fi
>   BOOTCONF=${TESTDIR}/bootconfig
> +ALIGN=4
>   
>   INITRD=`mktemp ${TESTDIR}/initrd-XXXX`
>   TEMPCONF=`mktemp ${TESTDIR}/temp-XXXX.bconf`
> @@ -59,7 +60,10 @@ echo "Show command test"
>   xpass $BOOTCONF $INITRD
>   
>   echo "File size check"
> -xpass test $new_size -eq $(expr $bconf_size + $initrd_size + 9 + 12)
> +total_size=$(expr $bconf_size + $initrd_size + 9 + 12 + $ALIGN - 1 )
> +total_size=$(expr $total_size / $ALIGN)
> +total_size=$(expr $total_size \* $ALIGN)
> +xpass test $new_size -eq $total_size
>   
>   echo "Apply command repeat test"
>   xpass $BOOTCONF -a $TEMPCONF $INITRD
>
Typo in the comment line 391: algin

Woody