bootconfig: Share the checksum function with tools

Move the checksum calculation function into the header for sharing it
with tools/bootconfig.

Link: https://lkml.kernel.org/r/162262197470.264090.16325743685807878807.stgit@devnote2

Signed-off-by: Masami Hiramatsu <[e-mail]>
Signed-off-by: Steven Rostedt (VMware) <[e-mail]>

include/linux/bootconfig.h

···
 #define BOOTCONFIG_ALIGN	(1 << BOOTCONFIG_ALIGN_SHIFT)
 #define BOOTCONFIG_ALIGN_MASK	(BOOTCONFIG_ALIGN - 1)
 
+/**
+ * xbc_calc_checksum() - Calculate checksum of bootconfig
+ * @data: Bootconfig data.
+ * @size: The size of the bootconfig data.
+ *
+ * Calculate the checksum value of the bootconfig data.
+ * The checksum will be used with the BOOTCONFIG_MAGIC and the size for
+ * embedding the bootconfig in the initrd image.
+ */
+static inline __init u32 xbc_calc_checksum(void *data, u32 size)
+{
+	unsigned char *p = data;
+	u32 ret = 0;
+
+	while (size--)
+		ret += *p++;
+
+	return ret;
+}
+
 /* XBC tree node */
 struct xbc_node {
 	u16 next;

init/main.c

···
 	return new_cmdline;
 }
 
-static u32 boot_config_checksum(unsigned char *p, u32 size)
-{
-	u32 ret = 0;
-
-	while (size--)
-		ret += *p++;
-
-	return ret;
-}
-
 static int __init bootconfig_params(char *param, char *val,
 				    const char *unused, void *arg)
 {
···
 		return;
 	}
 
-	if (boot_config_checksum((unsigned char *)data, size) != csum) {
+	if (xbc_calc_checksum(data, size) != csum) {
 		pr_err("bootconfig checksum failed\n");
 		return;
 	}

tools/bootconfig/main.c

···
 	}
 }
 
-/* Simple real checksum */
-static int checksum(unsigned char *buf, int len)
-{
-	int i, sum = 0;
-
-	for (i = 0; i < len; i++)
-		sum += buf[i];
-
-	return sum;
-}
-
 #define PAGE_SIZE	4096
 
 static int load_xbc_fd(int fd, char **buf, int size)
···
 		return ret;
 
 	/* Wrong Checksum */
-	rcsum = checksum((unsigned char *)*buf, size);
+	rcsum = xbc_calc_checksum(*buf, size);
 	if (csum != rcsum) {
 		pr_err("checksum error: %d != %d\n", csum, rcsum);
 		return -EINVAL;
···
 		return ret;
 	}
 	size = strlen(buf) + 1;
-	csum = checksum((unsigned char *)buf, size);
+	csum = xbc_calc_checksum(buf, size);
 
 	/* Backup the bootconfig data */
 	data = calloc(size + BOOTCONFIG_ALIGN +