[RFC PATCH v3 01/19] skc: Add supplemental kernel cmdline support

[Masami Hiramatsu <mhiramat@kernel.org>]

Supplemental kernel command line (SKC) allows admin to pass a
tree-structured supplemental kernel commandline file (SKC file)
when boot up kernel. This expands the kernel command line in
efficient way.

SKC file will contain some key-value commands, e.g.

key.word = value1;
another.key.word = value2;

It can fold same keys with braces, also you can write array
data. For example,

key {
   word1 {
      setting1 = data;
      setting2;
   }
   word2.array = "val1", "val2";
}

User can access these key-value pair and tree structure via
SKC APIs.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 MAINTAINERS         |    6 
 arch/Kconfig        |    9 +
 include/linux/skc.h |  205 +++++++++++++++
 lib/Kconfig         |    3 
 lib/Makefile        |    2 
 lib/skc.c           |  694 +++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 919 insertions(+)
 create mode 100644 include/linux/skc.h
 create mode 100644 lib/skc.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 035ffc1e16a3..67590c0e37c5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15362,6 +15362,12 @@ W:	http://www.stlinux.com
 S:	Supported
 F:	drivers/net/ethernet/stmicro/stmmac/
 
+SUPPLEMENTAL KERNEL CMDLINE
+M:	Masami Hiramatsu <mhiramat@kernel.org>
+S:	Maintained
+F:	lib/skc.c
+F:	include/linux/skc.h
+
 SUN3/3X
 M:	Sam Creasey <sammy@sammy.net>
 W:	http://sammy.net/sun3/
diff --git a/arch/Kconfig b/arch/Kconfig
index a7b57dd42c26..14d709ef0396 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -24,6 +24,15 @@ config HAVE_IMA_KEXEC
 config HOTPLUG_SMT
 	bool
 
+config SKC
+	bool "Supplemental kernel cmdline"
+	select LIBSKC
+	default y
+	help
+	 Supplemental kernel command line allows system admin to pass a
+	 text file as complemental extension of kernel cmdline when boot.
+	 The bootloader needs to support loading the SKC file.
+
 config OPROFILE
 	tristate "OProfile system profiling"
 	depends on PROFILING
diff --git a/include/linux/skc.h b/include/linux/skc.h
new file mode 100644
index 000000000000..71e485ce947f
--- /dev/null
+++ b/include/linux/skc.h
@@ -0,0 +1,205 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_SKC_H
+#define _LINUX_SKC_H
+/*
+ * Supplemental Kernel Command Line
+ * Copyright (C) 2019 Linaro Ltd.
+ * Author: Masami Hiramatsu <mhiramat@kernel.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+/* SKC tree node */
+struct skc_node {
+	u16 next;
+	u16 child;
+	u16 parent;
+	u16 data;
+} __attribute__ ((__packed__));
+
+#define SKC_KEY		0
+#define SKC_VALUE	(1 << 15)
+/* Maximum size of supplemental kernel cmdline is 32KB - 1 */
+#define SKC_DATA_MAX	(SKC_VALUE - 1)
+
+#define SKC_NODE_MAX	512
+#define SKC_KEYLEN_MAX	256
+#define SKC_DEPTH_MAX	16
+
+/* Node tree access raw APIs */
+struct skc_node * __init skc_root_node(void);
+int __init skc_node_index(struct skc_node *node);
+struct skc_node * __init skc_node_get_parent(struct skc_node *node);
+struct skc_node * __init skc_node_get_child(struct skc_node *node);
+struct skc_node * __init skc_node_get_next(struct skc_node *node);
+const char * __init skc_node_get_data(struct skc_node *node);
+
+/**
+ * skc_node_is_value() - Test the node is a value node
+ * @node: An SKC node.
+ *
+ * Test the @node is a value node and return true if a value node, false if not.
+ */
+static inline __init bool skc_node_is_value(struct skc_node *node)
+{
+	return !!(node->data & SKC_VALUE);
+}
+
+/**
+ * skc_node_is_key() - Test the node is a key node
+ * @node: An SKC node.
+ *
+ * Test the @node is a key node and return true if a key node, false if not.
+ */
+static inline __init bool skc_node_is_key(struct skc_node *node)
+{
+	return !(node->data & SKC_VALUE);
+}
+
+/**
+ * skc_node_is_array() - Test the node is an arraied value node
+ * @node: An SKC node.
+ *
+ * Test the @node is an arraied value node.
+ */
+static inline __init bool skc_node_is_array(struct skc_node *node)
+{
+	return skc_node_is_value(node) && node->next != 0;
+}
+
+/**
+ * skc_node_is_leaf() - Test the node is a leaf key node
+ * @node: An SKC node.
+ *
+ * Test the @node is a leaf key node which is a key node and has a value node
+ * or no child. Returns true if it is a leaf node, or false if not.
+ */
+static inline __init bool skc_node_is_leaf(struct skc_node *node)
+{
+	return skc_node_is_key(node) &&
+		(!node->child || skc_node_is_value(skc_node_get_child(node)));
+}
+
+/* Tree-based key-value access APIs */
+struct skc_node * __init skc_node_find_child(struct skc_node *parent,
+					     const char *key);
+
+const char * __init skc_node_find_value(struct skc_node *parent,
+					const char *key,
+					struct skc_node **vnode);
+
+struct skc_node * __init skc_node_find_next_leaf(struct skc_node *root,
+						 struct skc_node *leaf);
+
+const char * __init skc_node_find_next_key_value(struct skc_node *root,
+						 struct skc_node **leaf);
+
+/**
+ * skc_find_value() - Find a value which matches the key
+ * @key: Search key
+ * @vnode: A container pointer of SKC value node.
+ *
+ * Search a value whose key matches @key from whole of SKC tree and return
+ * the value if found. Found value node is stored in *@vnode.
+ * Note that this can return 0-length string and store NULL in *@vnode for
+ * key-only (non-value) entry.
+ */
+static inline const char * __init
+skc_find_value(const char *key, struct skc_node **vnode)
+{
+	return skc_node_find_value(NULL, key, vnode);
+}
+
+/**
+ * skc_find_node() - Find a node which matches the key
+ * @key: Search key
+ * @value: A container pointer of SKC value node.
+ *
+ * Search a (key) node whose key matches @key from whole of SKC tree and
+ * return the node if found. If not found, returns NULL.
+ */
+static inline struct skc_node * __init skc_find_node(const char *key)
+{
+	return skc_node_find_child(NULL, key);
+}
+
+/**
+ * skc_array_for_each_value() - Iterate value nodes on an array
+ * @anode: An SKC arraied value node
+ * @value: A value
+ *
+ * Iterate array value nodes and values starts from @anode. This is expected to
+ * be used with skc_find_value() and skc_node_find_value(), so that user can
+ * process each array entry node.
+ */
+#define skc_array_for_each_value(anode, value)				\
+	for (value = skc_node_get_data(anode); anode != NULL ;		\
+	     anode = skc_node_get_next(anode),				\
+	     value = anode ? skc_node_get_data(anode) : NULL)
+
+/**
+ * skc_node_for_each_child() - Iterate child nodes
+ * @parent: An SKC node.
+ * @child: Iterated SKC node.
+ *
+ * Iterate child nodes of @parent. Each child nodes are stored to @child.
+ */
+#define skc_node_for_each_child(parent, child)				\
+	for (child = skc_node_get_child(parent); child != NULL ;	\
+	     child = skc_node_get_next(child))
+
+/**
+ * skc_node_for_each_array_value() - Iterate array entries of geven key
+ * @node: An SKC node.
+ * @key: A key string searched under @node
+ * @anode: Iterated SKC node of array entry.
+ * @value: Iterated value of array entry.
+ *
+ * Iterate array entries of given @key under @node. Each array entry node
+ * is stroed to @anode and @value. If the @node doesn't have @key node,
+ * it does nothing.
+ * Note that even if the found key node has only one value (not array)
+ * this executes block once. Hoever, if the found key node has no value
+ * (key-only node), this does nothing. So don't use this for testing the
+ * key-value pair existence.
+ */
+#define skc_node_for_each_array_value(node, key, anode, value)		\
+	for (value = skc_node_find_value(node, key, &anode); value != NULL; \
+	     anode = skc_node_get_next(anode),				\
+	     value = anode ? skc_node_get_data(anode) : NULL)
+
+/**
+ * skc_node_for_each_key_value() - Iterate key-value pairs under a node
+ * @node: An SKC node.
+ * @knode: Iterated key node
+ * @value: Iterated value string
+ *
+ * Iterate key-value pairs under @node. Each key node and value string are
+ * stored in @knode and @value respectively.
+ */
+#define skc_node_for_each_key_value(node, knode, value)			\
+	for (knode = NULL, value = skc_node_find_next_key_value(node, &knode);\
+	     knode != NULL; value = skc_node_find_next_key_value(node, &knode))
+
+/**
+ * skc_for_each_key_value() - Iterate key-value pairs
+ * @knode: Iterated key node
+ * @value: Iterated value string
+ *
+ * Iterate key-value pairs in whole SKC tree. Each key node and value string
+ * are stored in @knode and @value respectively.
+ */
+#define skc_for_each_key_value(knode, value)				\
+	skc_node_for_each_key_value(NULL, knode, value)
+
+/* Compose complete key */
+int __init skc_node_compose_key(struct skc_node *node, char *buf, size_t size);
+
+/* SKC node initializer */
+int __init skc_init(char *buf);
+
+/* Debug dump functions */
+void __init skc_debug_dump(void);
+
+#endif
diff --git a/lib/Kconfig b/lib/Kconfig
index f33d66fc0e86..97a53f400a7c 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -568,6 +568,9 @@ config DIMLIB
 config LIBFDT
 	bool
 
+config LIBSKC
+	bool
+
 config OID_REGISTRY
 	tristate
 	help
diff --git a/lib/Makefile b/lib/Makefile
index 29c02a924973..52132d0d8ff2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -229,6 +229,8 @@ $(foreach file, $(libfdt_files), \
 	$(eval CFLAGS_$(file) = -I $(srctree)/scripts/dtc/libfdt))
 lib-$(CONFIG_LIBFDT) += $(libfdt_files)
 
+lib-$(CONFIG_LIBSKC) += skc.o
+
 obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
 obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o
 
diff --git a/lib/skc.c b/lib/skc.c
new file mode 100644
index 000000000000..bbcc81724ec4
--- /dev/null
+++ b/lib/skc.c
@@ -0,0 +1,694 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Supplemental Kernel Commandline
+ * Masami Hiramatsu <mhiramat@kernel.org>
+ */
+
+#define pr_fmt(fmt)    "skc: " fmt
+
+#include <linux/bug.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/skc.h>
+#include <linux/string.h>
+
+/*
+ * Supplemental Kernel Commandline (SKC) is given as tree-structured ascii
+ * text of key-value pairs on memory.
+ * skc_parse() parses the text to build a simple tree. Each tree node is
+ * simply a key word or a value. A key node may have a next key node or/and
+ * a child node (both key and value). A value node may have a next value
+ * node (for array).
+ */
+
+static struct skc_node skc_nodes[SKC_NODE_MAX] __initdata;
+static int skc_node_num __initdata;
+static char *skc_data __initdata;
+static size_t skc_data_size __initdata;
+static struct skc_node *last_parent __initdata;
+
+static int __init skc_parse_error(const char *msg, const char *p)
+{
+	int line = 0, col = 0;
+	int i, pos = p - skc_data;
+
+	for (i = 0; i < pos; i++) {
+		if (skc_data[i] == '\n') {
+			line++;
+			col = pos - i;
+		}
+	}
+	pr_err("Parse error at line %d, col %d: %s\n", line + 1, col + 1, msg);
+	return -EINVAL;
+}
+
+/**
+ * skc_root_node() - Get the root node of supplemental kernel cmdline
+ *
+ * Return the address of root node of supplemental kernel cmdline. If the
+ * supplemental kernel cmdline is not initiized, return NULL.
+ */
+struct skc_node * __init skc_root_node(void)
+{
+	if (unlikely(!skc_data))
+		return NULL;
+
+	return skc_nodes;
+}
+
+/**
+ * skc_node_index() - Get the index of SKC node
+ * @node: A target node of getting index.
+ *
+ * Return the index number of @node in SKC node list.
+ */
+int __init skc_node_index(struct skc_node *node)
+{
+	return node - &skc_nodes[0];
+}
+
+/**
+ * skc_node_get_parent() - Get the parent SKC node
+ * @node: An SKC node.
+ *
+ * Return the parent node of @node. If the node is top node of the tree,
+ * return NULL.
+ */
+struct skc_node * __init skc_node_get_parent(struct skc_node *node)
+{
+	return node->parent == SKC_NODE_MAX ? NULL : &skc_nodes[node->parent];
+}
+
+/**
+ * skc_node_get_child() - Get the child SKC node
+ * @node: An SKC node.
+ *
+ * Return the first child node of @node. If the node has no child, return
+ * NULL.
+ */
+struct skc_node * __init skc_node_get_child(struct skc_node *node)
+{
+	return node->child ? &skc_nodes[node->child] : NULL;
+}
+
+/**
+ * skc_node_get_next() - Get the next sibling SKC node
+ * @node: An SKC node.
+ *
+ * Return the NEXT sibling node of @node. If the node has no next sibling,
+ * return NULL. Note that even if this returns NULL, it doesn't mean @node
+ * has no siblings. (You also has to check whether the parent's child node
+ * is @node or not.)
+ */
+struct skc_node * __init skc_node_get_next(struct skc_node *node)
+{
+	return node->next ? &skc_nodes[node->next] : NULL;
+}
+
+/**
+ * skc_node_get_data() - Get the data of SKC node
+ * @node: An SKC node.
+ *
+ * Return the data (which is always a null terminated string) of @node.
+ * If the node has invalid data, warn and return NULL.
+ */
+const char * __init skc_node_get_data(struct skc_node *node)
+{
+	int offset = node->data & ~SKC_VALUE;
+
+	if (WARN_ON(offset >= skc_data_size))
+		return NULL;
+
+	return skc_data + offset;
+}
+
+static bool __init
+skc_node_match_prefix(struct skc_node *node, const char **prefix)
+{
+	const char *p = skc_node_get_data(node);
+	int len = strlen(p);
+
+	if (strncmp(*prefix, p, len))
+		return false;
+
+	p = *prefix + len;
+	if (*p == '.')
+		p++;
+	else if (*p != '\0')
+		return false;
+	*prefix = p;
+
+	return true;
+}
+
+/**
+ * skc_node_find_child() - Find a child node which matches given key
+ * @parent: An SKC node.
+ * @key: A key string.
+ *
+ * Search a node under @parent which matches @key. The @key can contain
+ * several words jointed with '.'. If @parent is NULL, this searches the
+ * node from whole tree. Return NULL if no node is matched.
+ */
+struct skc_node * __init
+skc_node_find_child(struct skc_node *parent, const char *key)
+{
+	struct skc_node *node;
+
+	if (parent)
+		node = skc_node_get_child(parent);
+	else
+		node = skc_root_node();
+
+	while (node && skc_node_is_key(node)) {
+		if (!skc_node_match_prefix(node, &key))
+			node = skc_node_get_next(node);
+		else if (*key != '\0')
+			node = skc_node_get_child(node);
+		else
+			break;
+	}
+
+	return node;
+}
+
+/**
+ * skc_node_find_value() - Find a value node which matches given key
+ * @parent: An SKC node.
+ * @key: A key string.
+ * @vnode: A container pointer of found SKC node.
+ *
+ * Search a value node under @parent whose (parent) key node matches @key,
+ * store it in *@vnode, and returns the value string.
+ * The @key can contain several words jointed with '.'. If @parent is NULL,
+ * this searches the node from whole tree. Return the value string if a
+ * matched key found, return NULL if no node is matched.
+ * Note that this returns 0-length string and stores NULL in *@vnode if the
+ * key has no value. And also it will return the value of the first entry if
+ * the value is an array.
+ */
+const char * __init
+skc_node_find_value(struct skc_node *parent, const char *key,
+		    struct skc_node **vnode)
+{
+	struct skc_node *node = skc_node_find_child(parent, key);
+
+	if (!node || !skc_node_is_key(node))
+		return NULL;
+
+	node = skc_node_get_child(node);
+	if (node && !skc_node_is_value(node))
+		return NULL;
+
+	if (vnode)
+		*vnode = node;
+
+	return node ? skc_node_get_data(node) : "";
+}
+
+/**
+ * skc_node_compose_key() - Compose key string of the SKC node
+ * @node: An SKC node.
+ * @buf: A buffer to store the key.
+ * @size: The size of the @buf.
+ *
+ * Compose the full-length key of the @node into @buf. Returns the total
+ * length of the key stored in @buf. Or returns -EINVAL if @node is NULL,
+ * and -ERANGE if the key depth is deeper than max depth.
+ */
+int __init skc_node_compose_key(struct skc_node *node, char *buf, size_t size)
+{
+	u16 keys[SKC_DEPTH_MAX];
+	int depth = 0, ret = 0, total = 0;
+
+	if (!node)
+		return -EINVAL;
+
+	if (skc_node_is_value(node))
+		node = skc_node_get_parent(node);
+
+	while (node) {
+		keys[depth++] = skc_node_index(node);
+		if (depth == SKC_DEPTH_MAX)
+			return -ERANGE;
+		node = skc_node_get_parent(node);
+	}
+
+	while (--depth >= 0) {
+		node = skc_nodes + keys[depth];
+		ret = snprintf(buf, size, "%s%s", skc_node_get_data(node),
+			       depth ? "." : "");
+		if (ret < 0)
+			return ret;
+		if (ret > size) {
+			size = 0;
+		} else {
+			size -= ret;
+			buf += ret;
+		}
+		total += ret;
+	}
+
+	return total;
+}
+
+/**
+ * skc_node_find_next_leaf() - Find the next leaf node under given node
+ * @root: An SKC root node
+ * @node: An SKC node which starts from.
+ *
+ * Search the next leaf node (which means the terminal key node) of @node
+ * under @root node (including @root node itself).
+ * Return the next node or NULL if next leaf node is not found.
+ */
+struct skc_node * __init skc_node_find_next_leaf(struct skc_node *root,
+						 struct skc_node *node)
+{
+	if (unlikely(!skc_data))
+		return NULL;
+
+	if (!node) {	/* First try */
+		node = root;
+		if (!node)
+			node = skc_nodes;
+	} else {
+		if (node == root)	/* @root was a leaf, no child node. */
+			return NULL;
+
+		while (!node->next) {
+			node = skc_node_get_parent(node);
+			if (node == root)
+				return NULL;
+			/* User passed a node which is not uder parent */
+			if (WARN_ON(!node))
+				return NULL;
+		}
+		node = skc_node_get_next(node);
+	}
+
+	while (node && !skc_node_is_leaf(node))
+		node = skc_node_get_child(node);
+
+	return node;
+}
+
+/**
+ * skc_node_find_next_key_value() - Find the next key-value pair nodes
+ * @root: An SKC root node
+ * @leaf: A container pointer of SKC node which starts from.
+ *
+ * Search the next leaf node (which means the terminal key node) of *@leaf
+ * under @root node. Returns the value and update *@leaf if next leaf node
+ * is found, or NULL if no next leaf node is found.
+ * Note that this returns 0-length string if the key has no value, or
+ * the value of the first entry if the value is an array.
+ */
+const char * __init skc_node_find_next_key_value(struct skc_node *root,
+						 struct skc_node **leaf)
+{
+	/* tip must be passed */
+	if (WARN_ON(!leaf))
+		return NULL;
+
+	*leaf = skc_node_find_next_leaf(root, *leaf);
+	if (!*leaf)
+		return NULL;
+	if ((*leaf)->child)
+		return skc_node_get_data(skc_node_get_child(*leaf));
+	else
+		return "";	/* No value key */
+}
+
+/* SKC parse and tree build */
+
+static struct skc_node * __init skc_add_node(char *data, u32 flag)
+{
+	struct skc_node *node;
+	unsigned long offset;
+
+	if (skc_node_num == SKC_NODE_MAX)
+		return NULL;
+
+	node = &skc_nodes[skc_node_num++];
+	offset = data - skc_data;
+	node->data = (u16)offset;
+	if (WARN_ON(offset >= SKC_DATA_MAX))
+		return NULL;
+	node->data |= flag;
+	node->child = 0;
+	node->next = 0;
+
+	return node;
+}
+
+static inline __init struct skc_node *skc_last_sibling(struct skc_node *node)
+{
+	while (node->next)
+		node = skc_node_get_next(node);
+
+	return node;
+}
+
+static struct skc_node * __init skc_add_sibling(char *data, u32 flag)
+{
+	struct skc_node *sib, *node = skc_add_node(data, flag);
+
+	if (node) {
+		if (!last_parent) {
+			node->parent = SKC_NODE_MAX;
+			sib = skc_last_sibling(skc_nodes);
+			sib->next = skc_node_index(node);
+		} else {
+			node->parent = skc_node_index(last_parent);
+			if (!last_parent->child) {
+				last_parent->child = skc_node_index(node);
+			} else {
+				sib = skc_node_get_child(last_parent);
+				sib = skc_last_sibling(sib);
+				sib->next = skc_node_index(node);
+			}
+		}
+	}
+
+	return node;
+}
+
+static inline __init struct skc_node *skc_add_child(char *data, u32 flag)
+{
+	struct skc_node *node = skc_add_sibling(data, flag);
+
+	if (node)
+		last_parent = node;
+
+	return node;
+}
+
+static inline __init bool skc_valid_keyword(char *key)
+{
+	if (key[0] == '\0')
+		return false;
+
+	while (isalnum(*key) || *key == '-' || *key == '_')
+		key++;
+
+	return *key == '\0';
+}
+
+static inline __init char *find_ending_quote(char *p)
+{
+	do {
+		p = strchr(p + 1, '"');
+		if (!p)
+			break;
+	} while (*(p - 1) == '\\');
+
+	return p;
+}
+
+/* Return delimiter or error, no node added */
+static int __init __skc_parse_value(char **__v, char **__n)
+{
+	char *p, *v = *__v;
+	int c;
+
+	v = skip_spaces(v);
+	if (*v == '"') {
+		v++;
+		p = find_ending_quote(v);
+		if (!p)
+			return skc_parse_error("No closing quotation", v);
+		*p++ = '\0';
+		p = skip_spaces(p);
+		if (*p != ',' && *p != ';')
+			return skc_parse_error("No delimiter for value", v);
+		c = *p;
+		*p++ = '\0';
+	} else {
+		p = strpbrk(v, ",;");
+		if (!p)
+			return skc_parse_error("No delimiter for value", v);
+		c = *p;
+		*p++ = '\0';
+		v = strim(v);
+	}
+	*__v = v;
+	*__n = p;
+
+	return c;
+}
+
+static int __init skc_parse_array(char **__v)
+{
+	struct skc_node *node;
+	char *next;
+	int c = 0;
+
+	do {
+		c = __skc_parse_value(__v, &next);
+		if (c < 0)
+			return c;
+
+		node = skc_add_sibling(*__v, SKC_VALUE);
+		if (!node)
+			return -ENOMEM;
+		*__v = next;
+	} while (c != ';');
+	node->next = 0;
+
+	return 0;
+}
+
+static inline __init
+struct skc_node *find_match_node(struct skc_node *node, char *k)
+{
+	while (node) {
+		if (!strcmp(skc_node_get_data(node), k))
+			break;
+		node = skc_node_get_next(node);
+	}
+	return node;
+}
+
+static int __init __skc_add_key(char *k)
+{
+	struct skc_node *node;
+
+	if (!skc_valid_keyword(k))
+		return skc_parse_error("Invalid keyword", k);
+
+	if (unlikely(skc_node_num == 0))
+		goto add_node;
+
+	if (!last_parent)	/* the first level */
+		node = find_match_node(skc_nodes, k);
+	else
+		node = find_match_node(skc_node_get_child(last_parent), k);
+
+	if (node)
+		last_parent = node;
+	else {
+add_node:
+		node = skc_add_child(k, SKC_KEY);
+		if (!node)
+			return -ENOMEM;
+	}
+	return 0;
+}
+
+static int __init __skc_parse_keys(char *k)
+{
+	char *p;
+	int ret;
+
+	k = strim(k);
+	while ((p = strchr(k, '.'))) {
+		*p++ = '\0';
+		ret = __skc_add_key(k);
+		if (ret)
+			return ret;
+		k = p;
+	}
+
+	return __skc_add_key(k);
+}
+
+static int __init skc_parse_kv(char **k, char *v)
+{
+	struct skc_node *prev_parent = last_parent;
+	struct skc_node *node;
+	char *next;
+	int c, ret;
+
+	ret = __skc_parse_keys(*k);
+	if (ret)
+		return ret;
+
+	c = __skc_parse_value(&v, &next);
+	if (c < 0)
+		return c;
+
+	node = skc_add_sibling(v, SKC_VALUE);
+	if (!node)
+		return -ENOMEM;
+
+	if (c == ',') {	/* Array */
+		ret = skc_parse_array(&next);
+		if (ret < 0)
+			return ret;
+	}
+
+	last_parent = prev_parent;
+
+	*k = next;
+
+	return 0;
+}
+
+static int __init skc_parse_key(char **k, char *n)
+{
+	struct skc_node *prev_parent = last_parent;
+	int ret;
+
+	*k = strim(*k);
+	if (**k != '\0') {
+		ret = __skc_parse_keys(*k);
+		if (ret)
+			return ret;
+		last_parent = prev_parent;
+	}
+
+	*k = n;
+
+	return 0;
+}
+
+static int __init skc_open_brace(char **k, char *n)
+{
+	int ret;
+
+	ret = __skc_parse_keys(*k);
+	if (ret)
+		return ret;
+
+	/* Mark the last key as open brace */
+	last_parent->next = SKC_NODE_MAX;
+
+	*k = n;
+
+	return 0;
+}
+
+static int __init skc_close_brace(char **k, char *n)
+{
+	struct skc_node *node;
+
+	*k = strim(*k);
+	if (**k != '\0')
+		return skc_parse_error("Unexpected key, maybe forgot ;?", *k);
+
+	if (!last_parent || last_parent->next != SKC_NODE_MAX)
+		return skc_parse_error("Unexpected closing brace", *k);
+
+	node = last_parent;
+	node->next = 0;
+	do {
+		node = skc_node_get_parent(node);
+	} while (node && node->next != SKC_NODE_MAX);
+	last_parent = node;
+
+	*k = n;
+
+	return 0;
+}
+
+static int __init skc_verify_tree(void)
+{
+	int i;
+
+	for (i = 0; i < skc_node_num; i++) {
+		if (skc_nodes[i].next > skc_node_num) {
+			return skc_parse_error("No closing brace",
+				skc_node_get_data(skc_nodes + i));
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * skc_init() - Parse given SKC file and build SKC internal tree
+ * @buf: Supplemental kernel cmdline text
+ *
+ * This parses the supplemental kernel cmdline text in @buf. @buf must be a
+ * null terminated string and smaller than SKC_DATA_MAX.
+ * Return 0 if succeeded, or -errno if there is any error.
+ */
+int __init skc_init(char *buf)
+{
+	char *p, *q;
+	int ret, c;
+
+	if (skc_data)
+		return -EBUSY;
+
+	ret = strlen(buf);
+	if (ret > SKC_DATA_MAX - 1 || ret == 0)
+		return -ERANGE;
+
+	skc_data = buf;
+	skc_data_size = ret + 1;
+
+	p = buf;
+	do {
+		q = strpbrk(p, "{}=;");
+		if (!q)
+			break;
+		c = *q;
+		*q++ = '\0';
+		switch (c) {
+		case '=':
+			ret = skc_parse_kv(&p, q);
+			break;
+		case '{':
+			ret = skc_open_brace(&p, q);
+			break;
+		case ';':
+			ret = skc_parse_key(&p, q);
+			break;
+		case '}':
+			ret = skc_close_brace(&p, q);
+			break;
+		}
+	} while (ret == 0);
+
+	if (ret < 0)
+		return ret;
+
+	if (!q) {
+		p = skip_spaces(p);
+		if (*p != '\0')
+			return skc_parse_error("No delimiter", p);
+	}
+
+	return skc_verify_tree();
+}
+
+/**
+ * skc_debug_dump() - Dump current SKC node list
+ *
+ * Dump the current SKC node list on printk buffer for debug.
+ */
+void __init skc_debug_dump(void)
+{
+	int i;
+
+	for (i = 0; i < skc_node_num; i++) {
+		pr_debug("[%d] %s (%s) .next=%d, .child=%d .parent=%d\n", i,
+			skc_node_get_data(skc_nodes + i),
+			skc_node_is_value(skc_nodes + i) ? "value" : "key",
+			skc_nodes[i].next, skc_nodes[i].child,
+			skc_nodes[i].parent);
+	}
+}