kmalloc: bugfixes and performance improvements

include/gay/clist.h

@@ -119,13 +119,23 @@ void clist_del(struct clist *node);
 /**
  * @brief Get the next entry in a clist.
  *
- * @param entry The `struct *` embedding a clist to get the sccessor of
+ * @param entry The `struct *` embedding a clist to get the successor of
  * @param member Name of the `struct clist` embedded within the entry
  * @returns The next `struct *` in the list
  */
 #define clist_next_entry(entry, member) \
 	clist_entry((entry)->member.next, typeof(*(entry)), member)
 
+/**
+ * @brief Get the previous entry in a clist.
+ *
+ * @param entry the `struct *` embedding a clist to the the predecessor of
+ * @param emember Name of the `struct clist` embedded within the entry
+ * @returns The previous `struct *` in the list
+ */
+#define clist_prev_entry(entry, member) \
+	clist_entry((entry)->member.prev, typeof(*(entry)), member)
+
 /**
  * @brief Iterate over each entry within a list.
  *
@@ -134,10 +144,46 @@ void clist_del(struct clist *node);
  * @param member Name of the `struct clist` within the embedding structure
  */
 #define clist_foreach_entry(head, cursor, member)				\
-	for ((cursor) = clist_first_entry(head, typeof((*cursor)), member);	\
+	for ((cursor) = clist_first_entry(head, typeof(*(cursor)), member);	\
 	     &(cursor)->member != (head);					\
 	     (cursor) = clist_next_entry(cursor, member))
 
+/**
+ * @brief Continue iterating over each entry within a clist.
+ *
+ * @param head The `struct clist *` that is the head node in the list
+ * @param cursor The `struct *` list entry from which to continue
+ * @param member Name of the `struct clist` within the embedding structure
+ */
+#define clist_foreach_entry_continue(head, cursor, member)			\
+	for ((cursor) = clist_next_entry(cursor, member);			\
+	     &(cursor)->member != (head);					\
+	     (cursor) = clist_next_entry(cursor, member))
+
+/**
+ * @brief Iterate over a clist in reverse order.
+ *
+ * @param head The `struct clist *` that is the head node in the list
+ * @param cursor A `struct *` the list nodes are embedded in to use as a cursor
+ * @param member Name of the `struct clist` within the embedding structure
+ */
+#define clist_foreach_entry_rev(head, cursor, member)				\
+	for ((cursor) = clist_last_entry(head, typeof(*(cursor)), member);	\
+	     &(cursor)->member != (head);					\
+	     (cursor) = clist_prev_entry(cursor, member))
+
+/**
+ * @brief Continue iterating over a clist in reverse order.
+ *
+ * @param head The `struct clist *` that is the head node in the list
+ * @param cursor The `struct *` list entry from which to continue
+ * @param member Name of the `struct clist` within the embedding structure
+ */
+#define clist_foreach_entry_rev_continue(head, cursor, member)			\
+	for ((cursor) = clist_prev_entry(cursor, member);			\
+	     &(cursor)->member != (head);					\
+	     (cursor) = clist_prev_entry(cursor, member))
+
 /**
  * @brief Iterate over each entry within a list, this is safe from element removal.
  *

kernel/mm/kmalloc.c

@@ -19,7 +19,7 @@
  * doesn't have paging:
  * <https://git.bsd.gay/fef/ardix/src/commit/c767d551d3301fc30f9fce30eda8f04e2f9a42ab/kernel/mm.c>
  * As a matter of fact, this allocator is merely an extension of the one from
- * Ardix with the only difference being that the heap can grow upwards.
+ * Ardix with the only difference being that the heap can be extended upwards.
  */
 
 /**
@@ -46,7 +46,7 @@ struct memblk {
 		/** @brief Used as the return value for `kmalloc()` */
 		u8 data[0];
 		/**
-		 * @brief Used to get the copy of the low_size field at the end of
+		 * @brief Used to get the copy of the size at the end of
 		 * the block, right after the last byte of `data`
 		 */
 		usize high_size[0];
@@ -274,7 +274,7 @@ static struct memblk *blk_try_merge(struct memblk *blk)
 		if (blk_get_size(cursor) >= blk_get_size(blk))
 			break;
 	}
-	clist_add_first(&cursor->clink, &blk->clink);
+	clist_add(&cursor->clink, &blk->clink);
 
 	return blk;
 }
@@ -292,13 +292,14 @@ static struct memblk *blk_merge(struct memblk *bottom, struct memblk *top)
 
 static struct memblk *blk_slice(struct memblk *blk, usize slice_size)
 {
+	struct memblk *cursor = clist_prev_entry(blk, clink);
 	clist_del(&blk->clink);
 
 	/*
-	 * If the remaining low_size is less than the minimum allocation unit, we
+	 * If the remaining size is less than the minimum allocation unit, we
 	 * hand out the entire block.  Additionally, we must add an underflow
-	 * check which happens if the slice low_size is less than OVERHEAD smaller
-	 * than the full block low_size.
+	 * check which happens if the slice size is less than OVERHEAD smaller
+	 * than the full block size.
 	 */
 	usize rest_size = blk_get_size(blk) - slice_size - OVERHEAD;
 	if (rest_size < MIN_SIZE || rest_size + OVERHEAD < rest_size) {
@@ -316,8 +317,7 @@ static struct memblk *blk_slice(struct memblk *blk, usize slice_size)
 	blk_set_alloc(blk);
 	blk_clear_border_end(blk);
 
-	struct memblk *cursor;
-	clist_foreach_entry(&blocks, cursor, clink) {
+	clist_foreach_entry_rev_continue(&blocks, cursor, clink) {
 		if (blk_get_size(cursor) <= rest_size)
 			break;
 	}
@@ -348,6 +348,11 @@ static inline struct memblk *blk_next(struct memblk *blk)
 
 static inline usize blk_get_size(struct memblk *blk)
 {
+#	ifdef DEBUG
+		usize index = blk->low_size[0] / sizeof(blk->low_size[0]);
+		if ((blk->low_size[0] & SIZE_MASK) != (blk->high_size[index] & SIZE_MASK))
+			kprintf("Memory corruption in block %p detected!\n", blk);
+#	endif
 	return blk->low_size[0] & SIZE_MASK;
 }
 
@@ -356,7 +361,7 @@ static void blk_set_size(struct memblk *blk, usize size)
 	/* don't affect flags */
 	blk->low_size[0] &= ~SIZE_MASK;
 #       ifdef DEBUG
-		if (size & SIZE_MASK)
+		if (size & ~SIZE_MASK)
 			kprintf("Unaligned size in blk_set_size()\n");
 #       endif
 	blk->low_size[0] |= size & SIZE_MASK;