1 files changed, 187 insertions, 8 deletions

diff --git a/include/linux/list.h b/include/linux/list.h
index dd6c2041d09c..00ea8e5fb88b 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -20,8 +20,16 @@
  * using the generic single-entry routines.
  */
 
+/**
+ * LIST_HEAD_INIT - initialize a &struct list_head's links to point to itself
+ * @name: name of the list_head
+ */
 #define LIST_HEAD_INIT(name) { &(name), &(name) }
 
+/**
+ * LIST_HEAD - definition of a &struct list_head with initialization values
+ * @name: name of the list_head
+ */
 #define LIST_HEAD(name) \
 	struct list_head name = LIST_HEAD_INIT(name)
 
@@ -35,14 +43,95 @@
 static inline void INIT_LIST_HEAD(struct list_head *list)
 {
 	WRITE_ONCE(list->next, list);
-	list->prev = list;
+	WRITE_ONCE(list->prev, list);
 }
 
+#ifdef CONFIG_LIST_HARDENED
+
 #ifdef CONFIG_DEBUG_LIST
-extern bool __list_add_valid(struct list_head *new,
-			      struct list_head *prev,
-			      struct list_head *next);
-extern bool __list_del_entry_valid(struct list_head *entry);
+# define __list_valid_slowpath
+#else
+# define __list_valid_slowpath __cold __preserve_most
+#endif
+
+/*
+ * Performs the full set of list corruption checks before __list_add().
+ * On list corruption reports a warning, and returns false.
+ */
+bool __list_valid_slowpath __list_add_valid_or_report(struct list_head *new,
+						      struct list_head *prev,
+						      struct list_head *next);
+
+/*
+ * Performs list corruption checks before __list_add(). Returns false if a
+ * corruption is detected, true otherwise.
+ *
+ * With CONFIG_LIST_HARDENED only, performs minimal list integrity checking
+ * inline to catch non-faulting corruptions, and only if a corruption is
+ * detected calls the reporting function __list_add_valid_or_report().
+ */
+static __always_inline bool __list_add_valid(struct list_head *new,
+					     struct list_head *prev,
+					     struct list_head *next)
+{
+	bool ret = true;
+
+	if (!IS_ENABLED(CONFIG_DEBUG_LIST)) {
+		/*
+		 * With the hardening version, elide checking if next and prev
+		 * are NULL, since the immediate dereference of them below would
+		 * result in a fault if NULL.
+		 *
+		 * With the reduced set of checks, we can afford to inline the
+		 * checks, which also gives the compiler a chance to elide some
+		 * of them completely if they can be proven at compile-time. If
+		 * one of the pre-conditions does not hold, the slow-path will
+		 * show a report which pre-condition failed.
+		 */
+		if (likely(next->prev == prev && prev->next == next && new != prev && new != next))
+			return true;
+		ret = false;
+	}
+
+	ret &= __list_add_valid_or_report(new, prev, next);
+	return ret;
+}
+
+/*
+ * Performs the full set of list corruption checks before __list_del_entry().
+ * On list corruption reports a warning, and returns false.
+ */
+bool __list_valid_slowpath __list_del_entry_valid_or_report(struct list_head *entry);
+
+/*
+ * Performs list corruption checks before __list_del_entry(). Returns false if a
+ * corruption is detected, true otherwise.
+ *
+ * With CONFIG_LIST_HARDENED only, performs minimal list integrity checking
+ * inline to catch non-faulting corruptions, and only if a corruption is
+ * detected calls the reporting function __list_del_entry_valid_or_report().
+ */
+static __always_inline bool __list_del_entry_valid(struct list_head *entry)
+{
+	bool ret = true;
+
+	if (!IS_ENABLED(CONFIG_DEBUG_LIST)) {
+		struct list_head *prev = entry->prev;
+		struct list_head *next = entry->next;
+
+		/*
+		 * With the hardening version, elide checking if next and prev
+		 * are NULL, LIST_POISON1 or LIST_POISON2, since the immediate
+		 * dereference of them below would result in a fault.
+		 */
+		if (likely(prev->next == entry && next->prev == entry))
+			return true;
+		ret = false;
+	}
+
+	ret &= __list_del_entry_valid_or_report(entry);
+	return ret;
+}
 #else
 static inline bool __list_add_valid(struct list_head *new,
 				struct list_head *prev,
@@ -306,7 +395,7 @@ static inline int list_empty(const struct list_head *head)
 static inline void list_del_init_careful(struct list_head *entry)
 {
 	__list_del_entry(entry);
-	entry->prev = entry;
+	WRITE_ONCE(entry->prev, entry);
 	smp_store_release(&entry->next, entry);
 }
 
@@ -326,7 +415,7 @@ static inline void list_del_init_careful(struct list_head *entry)
 static inline int list_empty_careful(const struct list_head *head)
 {
 	struct list_head *next = smp_load_acquire(&head->next);
-	return list_is_head(next, head) && (next == head->prev);
+	return list_is_head(next, head) && (next == READ_ONCE(head->prev));
 }
 
 /**
@@ -556,6 +645,20 @@ static inline void list_splice_tail_init(struct list_head *list,
 })
 
 /**
+ * list_last_entry_or_null - get the last element from a list
+ * @ptr:	the list head to take the element from.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Note that if the list is empty, it returns NULL.
+ */
+#define list_last_entry_or_null(ptr, type, member) ({ \
+	struct list_head *head__ = (ptr); \
+	struct list_head *pos__ = READ_ONCE(head__->prev); \
+	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
+})
+
+/**
  * list_next_entry - get the next element in list
  * @pos:	the type * to cursor
  * @member:	the name of the list_head within the struct.
@@ -564,6 +667,19 @@ static inline void list_splice_tail_init(struct list_head *list,
 	list_entry((pos)->member.next, typeof(*(pos)), member)
 
 /**
+ * list_next_entry_circular - get the next element in list
+ * @pos:	the type * to cursor.
+ * @head:	the list head to take the element from.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Wraparound if pos is the last element (return the first element).
+ * Note, that list is expected to be not empty.
+ */
+#define list_next_entry_circular(pos, head, member) \
+	(list_is_last(&(pos)->member, head) ? \
+	list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member))
+
+/**
  * list_prev_entry - get the prev element in list
  * @pos:	the type * to cursor
  * @member:	the name of the list_head within the struct.
@@ -572,6 +688,19 @@ static inline void list_splice_tail_init(struct list_head *list,
 	list_entry((pos)->member.prev, typeof(*(pos)), member)
 
 /**
+ * list_prev_entry_circular - get the prev element in list
+ * @pos:	the type * to cursor.
+ * @head:	the list head to take the element from.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Wraparound if pos is the first element (return the last element).
+ * Note, that list is expected to be not empty.
+ */
+#define list_prev_entry_circular(pos, head, member) \
+	(list_is_first(&(pos)->member, head) ? \
+	list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member))
+
+/**
  * list_for_each	-	iterate over a list
  * @pos:	the &struct list_head to use as a loop cursor.
  * @head:	the head for your list.
@@ -620,13 +749,28 @@ static inline void list_splice_tail_init(struct list_head *list,
 	     pos = n, n = pos->prev)
 
 /**
+ * list_count_nodes - count nodes in the list
+ * @head:	the head for your list.
+ */
+static inline size_t list_count_nodes(struct list_head *head)
+{
+	struct list_head *pos;
+	size_t count = 0;
+
+	list_for_each(pos, head)
+		count++;
+
+	return count;
+}
+
+/**
  * list_entry_is_head - test if the entry points to the head of the list
  * @pos:	the type * to cursor
  * @head:	the head for your list.
  * @member:	the name of the list_head within the struct.
  */
 #define list_entry_is_head(pos, head, member)				\
-	(&pos->member == (head))
+	list_is_head(&pos->member, (head))
 
 /**
  * list_for_each_entry	-	iterate over list of given type
@@ -979,6 +1123,26 @@ static inline void hlist_move_list(struct hlist_head *old,
 	old->first = NULL;
 }
 
+/**
+ * hlist_splice_init() - move all entries from one list to another
+ * @from: hlist_head from which entries will be moved
+ * @last: last entry on the @from list
+ * @to:   hlist_head to which entries will be moved
+ *
+ * @to can be empty, @from must contain at least @last.
+ */
+static inline void hlist_splice_init(struct hlist_head *from,
+				     struct hlist_node *last,
+				     struct hlist_head *to)
+{
+	if (to->first)
+		to->first->pprev = &last->next;
+	last->next = to->first;
+	to->first = from->first;
+	from->first->pprev = &to->first;
+	from->first = NULL;
+}
+
 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 
 #define hlist_for_each(pos, head) \
@@ -1035,4 +1199,19 @@ static inline void hlist_move_list(struct hlist_head *old,
 	     pos && ({ n = pos->member.next; 1; });			\
 	     pos = hlist_entry_safe(n, typeof(*pos), member))
 
+/**
+ * hlist_count_nodes - count nodes in the hlist
+ * @head:	the head for your hlist.
+ */
+static inline size_t hlist_count_nodes(struct hlist_head *head)
+{
+	struct hlist_node *pos;
+	size_t count = 0;
+
+	hlist_for_each(pos, head)
+		count++;
+
+	return count;
+}
+
 #endif