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

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Date:   Tue, 17 Nov 2020 00:51:39 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Chen Yu <yu.c.chen@...el.com>,
        Chen Yu <yu.chen.surf@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 1/2] tools/bootconfig: Align the bootconfig applied
 initrd image size to 4

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