bootconfig: init: Allow admin to use bootconfig for kernel command line

Since the current kernel command line is too short to describe
many options which supported by kernel, allow user to use boot
config to setup (add) the command line options.

All kernel parameters under "kernel." keywords will be used
for setting up extra kernel command line.

For example,

kernel {
	audit = on
	audit_backlog_limit = 256
}

Note that you can not specify some early parameters
(like console etc.) by this method, since it is
loaded after early parameters parsed.

Link: http://lkml.kernel.org/r/157867228333.17873.11962796367032622466.stgit@devnote2Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

init/main.c

@@ -137,6 +137,8 @@ char __initdata boot_command_line[COMMAND_LINE_SIZE];
 char *saved_command_line;
 /* Command line for parameter parsing */
 static char *static_command_line;
+/* Untouched extra command line */
+static char *extra_command_line;
 
 static char *execute_command;
 static char *ramdisk_execute_command;
@@ -245,6 +247,83 @@ static int __init loglevel(char *str)
 early_param("loglevel", loglevel);
 
 #ifdef CONFIG_BOOT_CONFIG
+
+char xbc_namebuf[XBC_KEYLEN_MAX] __initdata;
+
+#define rest(dst, end) ((end) > (dst) ? (end) - (dst) : 0)
+
+static int __init xbc_snprint_cmdline(char *buf, size_t size,
+				      struct xbc_node *root)
+{
+	struct xbc_node *knode, *vnode;
+	char *end = buf + size;
+	char c = '\"';
+	const char *val;
+	int ret;
+
+	xbc_node_for_each_key_value(root, knode, val) {
+		ret = xbc_node_compose_key_after(root, knode,
+					xbc_namebuf, XBC_KEYLEN_MAX);
+		if (ret < 0)
+			return ret;
+
+		vnode = xbc_node_get_child(knode);
+		ret = snprintf(buf, rest(buf, end), "%s%c", xbc_namebuf,
+				vnode ? '=' : ' ');
+		if (ret < 0)
+			return ret;
+		buf += ret;
+		if (!vnode)
+			continue;
+
+		c = '\"';
+		xbc_array_for_each_value(vnode, val) {
+			ret = snprintf(buf, rest(buf, end), "%c%s", c, val);
+			if (ret < 0)
+				return ret;
+			buf += ret;
+			c = ',';
+		}
+		if (rest(buf, end) > 2)
+			strcpy(buf, "\" ");
+		buf += 2;
+	}
+
+	return buf - (end - size);
+}
+#undef rest
+
+/* Make an extra command line under given key word */
+static char * __init xbc_make_cmdline(const char *key)
+{
+	struct xbc_node *root;
+	char *new_cmdline;
+	int ret, len = 0;
+
+	root = xbc_find_node(key);
+	if (!root)
+		return NULL;
+
+	/* Count required buffer size */
+	len = xbc_snprint_cmdline(NULL, 0, root);
+	if (len <= 0)
+		return NULL;
+
+	new_cmdline = memblock_alloc(len + 1, SMP_CACHE_BYTES);
+	if (!new_cmdline) {
+		pr_err("Failed to allocate memory for extra kernel cmdline.\n");
+		return NULL;
+	}
+
+	ret = xbc_snprint_cmdline(new_cmdline, len + 1, root);
+	if (ret < 0 || ret > len) {
+		pr_err("Failed to print extra kernel cmdline.\n");
+		return NULL;
+	}
+
+	return new_cmdline;
+}
+
 u32 boot_config_checksum(unsigned char *p, u32 size)
 {
 	u32 ret = 0;
@@ -289,8 +368,11 @@ static void __init setup_boot_config(void)
 
 	if (xbc_init(copy) < 0)
 		pr_err("Failed to parse boot config\n");
-	else
+	else {
 		pr_info("Load boot config: %d bytes\n", size);
+		/* keys starting with "kernel." are passed via cmdline */
+		extra_command_line = xbc_make_cmdline("kernel");
+	}
 }
 #else
 #define setup_boot_config()	do { } while (0)
@@ -425,7 +507,12 @@ static inline void smp_prepare_cpus(unsigned int maxcpus) { }
  */
 static void __init setup_command_line(char *command_line)
 {
-	size_t len = strlen(boot_command_line) + 1;
+	size_t len, xlen = 0;
+
+	if (extra_command_line)
+		xlen = strlen(extra_command_line);
+
+	len = xlen + strlen(boot_command_line) + 1;
 
 	saved_command_line = memblock_alloc(len, SMP_CACHE_BYTES);
 	if (!saved_command_line)
@@ -435,8 +522,17 @@ static void __init setup_command_line(char *command_line)
 	if (!static_command_line)
 		panic("%s: Failed to allocate %zu bytes\n", __func__, len);
 
-	strcpy(saved_command_line, boot_command_line);
-	strcpy(static_command_line, command_line);
+	if (xlen) {
+		/*
+		 * We have to put extra_command_line before boot command
+		 * lines because there could be dashes (separator of init
+		 * command line) in the command lines.
+		 */
+		strcpy(saved_command_line, extra_command_line);
+		strcpy(static_command_line, extra_command_line);
+	}
+	strcpy(saved_command_line + xlen, boot_command_line);
+	strcpy(static_command_line + xlen, command_line);
 }
 
 /*
@@ -652,7 +748,7 @@ asmlinkage __visible void __init start_kernel(void)
 	build_all_zonelists(NULL);
 	page_alloc_init();
 
-	pr_notice("Kernel command line: %s\n", boot_command_line);
+	pr_notice("Kernel command line: %s\n", saved_command_line);
 	/* parameters may set static keys */
 	jump_label_init();
 	parse_early_param();