tools/bootconfig: Align the bootconfig applied initrd image size to 4

Align the bootconfig applied initrd image size to 4. To fill the gap,
the bootconfig command uses null characters in between the bootconfig
data and the footer. This will expands the footer size but don't change
the checksum.
Thus the block image of the initrd file with bootconfig is as follows.

[initrd][bootconfig][(pad)][size][csum]["#BOOTCONFIG\n"]

Link: https://lkml.kernel.org/r/160576522046.320071.8550680670010950634.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 34 insertions, 23 deletions

diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c
index a0733cbb3c49..4a445b6304bb 100644
--- a/tools/bootconfig/main.c
+++ b/tools/bootconfig/main.c
@@ -337,12 +337,13 @@ static int delete_xbc(const char *path)
 
 static int apply_xbc(const char *path, const char *xbc_path)
 {
+	char *buf, *data, *p;
+	size_t total_size;
 	struct stat stat;
+	const char *msg;
 	u32 size, csum;
-	char *buf, *data;
+	int pos, pad;
 	int ret, fd;
-	const char *msg;
-	int pos;
 
 	ret = load_xbc_file(xbc_path, &buf);
 	if (ret < 0) {
@@ -352,13 +353,12 @@ static int apply_xbc(const char *path, const char *xbc_path)
 	size = strlen(buf) + 1;
 	csum = checksum((unsigned char *)buf, size);
 
-	/* Prepare xbc_path data */
-	data = malloc(size + 8);
+	/* Backup the bootconfig data */
+	data = calloc(size + BOOTCONFIG_ALIGN +
+		      sizeof(u32) + sizeof(u32) + BOOTCONFIG_MAGIC_LEN, 1);
 	if (!data)
 		return -ENOMEM;
-	strcpy(data, buf);
-	*(u32 *)(data + size) = size;
-	*(u32 *)(data + size + 4) = csum;
+	memcpy(data, buf, size);
 
 	/* Check the data format */
 	ret = xbc_init(buf, &msg, &pos);
@@ -399,24 +399,35 @@ static int apply_xbc(const char *path, const char *xbc_path)
 		pr_err("Failed to get the size of %s\n", path);
 		goto out;
 	}
-	ret = write(fd, data, size + 8);
-	if (ret < size + 8) {
+
+	/* To align up the total size to BOOTCONFIG_ALIGN, get padding size */
+	total_size = stat.st_size + size + sizeof(u32) * 2 + BOOTCONFIG_MAGIC_LEN;
+	pad = ((total_size + BOOTCONFIG_ALIGN - 1) & (~BOOTCONFIG_ALIGN_MASK)) - total_size;
+	size += pad;
+
+	/* Add a footer */
+	p = data + size;
+	*(u32 *)p = size;
+	p += sizeof(u32);
+
+	*(u32 *)p = csum;
+	p += sizeof(u32);
+
+	memcpy(p, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN);
+	p += BOOTCONFIG_MAGIC_LEN;
+
+	total_size = p - data;
+
+	ret = write(fd, data, total_size);
+	if (ret < total_size) {
 		if (ret < 0)
 			ret = -errno;
 		pr_err("Failed to apply a boot config: %d\n", ret);
-		if (ret < 0)
-			goto out;
-		goto out_rollback;
-	}
-	/* Write a magic word of the bootconfig */
-	ret = write(fd, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN);
-	if (ret < BOOTCONFIG_MAGIC_LEN) {
-		if (ret < 0)
-			ret = -errno;
-		pr_err("Failed to apply a boot config magic: %d\n", ret);
-		goto out_rollback;
-	}
-	ret = 0;
+		if (ret >= 0)
+			goto out_rollback;
+	} else
+		ret = 0;
+
 out:
 	close(fd);
 	free(data);