linux-kernel - [RFC PATCH 1/3] bootconfig: Use hexadecimal ASCII string for size and checksum

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Date:   Thu, 19 Nov 2020 23:31:42 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Chen Yu <yu.c.chen@...el.com>, Chen Yu <yu.chen.surf@...il.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org
Subject: [RFC PATCH 1/3] bootconfig: Use hexadecimal ASCII string for size and checksum

To make the bootconfig format more platform independent, use
8-bytes hexadecimal ASCII string for size and checksum field
in the footer. This will allow us to apply bootconfig to the
cross build initrd without caring the endianness.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 init/main.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/init/main.c b/init/main.c
index 20baced721ad..b82f23cff709 100644
--- a/init/main.c
+++ b/init/main.c
@@ -267,8 +267,8 @@ early_param("loglevel", loglevel);
 static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
 {
 	u32 size, csum;
+	char buf[9];
 	char *data;
-	u32 *hdr;
 	int i;
 
 	if (!initrd_end)
@@ -287,11 +287,21 @@ static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
 	return NULL;
 
 found:
-	hdr = (u32 *)(data - 8);
-	size = hdr[0];
-	csum = hdr[1];
+	buf[8] = '\0';
+	data -= 8;
+	memcpy(buf, data, 8);
+	if (kstrtou32(buf, 16, &csum) != 0) {
+		pr_err("bootconfig checksum field is invalid\n");
+		return NULL;
+	}
+	data -= 8;
+	memcpy(buf, data, 8);
+	if (kstrtou32(buf, 16, &size) != 0) {
+		pr_err("bootconfig size field is invalid\n");
+		return NULL;
+	}
+	data -= size;
 
-	data = ((void *)hdr) - size;
 	if ((unsigned long)data < initrd_start) {
 		pr_err("bootconfig size %d is greater than initrd size %ld\n",
 			size, initrd_end - initrd_start);