libpayload: special case large memalign() requests

For memalign() requests the current allocator keeps metadata
about each chunk of aligned memory that copmrises the size
requested. For large allocations relative to the alignment
this can cause significant metadata overhead. Instead, consider
all memalign() requests whose size meets or exceeds 1KiB or
alignment that meets or exceeds 1KiB large requests.
These requests are handled specially to only allocate
the amount of memory required for the size and alignment
constraints by not allocating any metadata as the whole region
would be consumed by the request.

BUG=None
BRANCH=None
TEST=Built and tested various scenarios. Noted the ability to
     free() and properly coalesce the heap as expected.

Change-Id: Ia9cf5529ca859e490617af296cffd2705c2c6fd8
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 4e32fc57626dac6194c9fd0141df680b4a5417e8
Original-Change-Id: Icdf022831b733e3bb84a2d2f3b499f4e25d89128
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/242456
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/8729
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/libpayload/libc/malloc.c

@@ -318,6 +318,8 @@ void *realloc(void *ptr, size_t size)
 
 struct align_region_t
 {
+	/* If alignment is 0 then the region reqpresents a large region which
+	 * has no metadata for tracking subelements. */
 	int alignment;
 	/* start in memory, and size in bytes */
 	void* start;
@@ -336,58 +338,126 @@ struct align_region_t
 	struct align_region_t *next;
 };
 
-static struct align_region_t *allocate_region(int alignment, int num_elements, struct memory_type *type)
+static inline int region_is_large(const struct align_region_t *r)
 {
-	struct align_region_t *new_region;
+	return r->alignment == 0;
-#ifdef CONFIG_LP_DEBUG_MALLOC
-	printf("%s(old align_regions=%p, alignment=%u, num_elements=%u)\n",
-			__func__, type->align_regions, alignment, num_elements);
-#endif
-
-	new_region = malloc(sizeof(struct align_region_t));
-
-	if (!new_region)
-		return NULL;
-	new_region->alignment = alignment;
-	new_region->start = alloc((num_elements+1) * alignment + num_elements, type);
-	if (!new_region->start) {
-		free(new_region);
-		return NULL;
-	}
-	new_region->start_data = (void*)((uintptr_t)(new_region->start + num_elements + alignment - 1) & (~(alignment-1)));
-	new_region->size = num_elements * alignment;
-	new_region->free = num_elements;
-	new_region->next = type->align_regions;
-	memset(new_region->start, 0, num_elements);
-	type->align_regions = new_region;
-	return new_region;
 }
 
+static inline int addr_in_region(const struct align_region_t *r, void *addr)
+{
+	return ((addr >= r->start_data) && (addr < r->start_data + r->size));
+}
+
+/* num_elements == 0 indicates a large aligned region instead of a smaller
+ * region comprised of alignment-sized chunks. */
+static struct align_region_t *allocate_region(int alignment, int num_elements,
+					size_t size, struct memory_type *type)
+{
+	struct align_region_t *r;
+	size_t extra_space;
+
+#ifdef CONFIG_LP_DEBUG_MALLOC
+	printf("%s(old align_regions=%p, alignment=%u, num_elements=%u, size=%zu)\n",
+		__func__, type->align_regions, alignment, num_elements, size);
+#endif
+
+	r = malloc(sizeof(*r));
+
+	if (r == NULL)
+		return NULL;
+
+	memset(r, 0, sizeof(r));
+
+	if (num_elements != 0) {
+		r->alignment = alignment;
+		r->size = num_elements * alignment;
+		r->free = num_elements;
+		/* Allocate enough memory for alignment requirements and
+		 * metadata for each chunk. */
+		extra_space = num_elements;
+	} else {
+		/* Large aligned allocation. Set alignment = 0. */
+		r->alignment = 0;
+		r->size = size;
+		extra_space = 0;
+	}
+
+	r->start = alloc(r->size + alignment + extra_space, type);
+
+	if (r->start == NULL) {
+		free(r);
+		return NULL;
+	}
+
+	r->start_data = (void *)ALIGN_UP((uintptr_t)r->start + extra_space,
+					alignment);
+
+	/* Clear any (if requested) metadata. */
+	memset(r->start, 0, extra_space);
+
+	/* Link the region with the rest. */
+	r->next = type->align_regions;
+	type->align_regions = r;
+
+	return r;
+}
+
+static void try_free_region(struct align_region_t **prev_link)
+{
+	struct align_region_t *r = *prev_link;
+
+	/* All large regions are immediately free-able. Non-large regions
+	 * need to be checked for the fully freed state. */
+	if (!region_is_large(r)) {
+		if (r->free != r->size / r->alignment)
+			return;
+	}
+
+	/* Unlink region from link list. */
+	*prev_link = r->next;
+
+	/* Free the data and metadata. */
+	free(r->start);
+	free(r);
+}
 
 static int free_aligned(void* addr, struct memory_type *type)
 {
-	struct align_region_t *reg = type->align_regions;
+	struct align_region_t **prev_link = &type->align_regions;
-	while (reg != 0)
+
+	while (*prev_link != NULL)
 	{
-		if ((addr >= reg->start_data) && (addr < reg->start_data + reg->size))
+		if (!addr_in_region(*prev_link, addr)) {
-		{
+			prev_link = &((*prev_link)->next);
-			int i = (addr-reg->start_data)/reg->alignment;
+			continue;
-			while (((u8*)reg->start)[i]==2)
+		}
-			{
+
-				((u8*)reg->start)[i++]=0;
+		if (region_is_large(*prev_link)) {
-				reg->free++;
+			try_free_region(prev_link);
-			}
-			((u8*)reg->start)[i]=0;
-			reg->free++;
 			return 1;
 		}
-		reg = reg->next;
+
+		int i = (addr-(*prev_link)->start_data)/(*prev_link)->alignment;
+		u8 *meta = (*prev_link)->start;
+		while (meta[i] == 2)
+		{
+			meta[i++] = 0;
+			(*prev_link)->free++;
+		}
+		meta[i] = 0;
+		(*prev_link)->free++;
+		try_free_region(prev_link);
+		return 1;
 	}
 	return 0;
 }
 
 static void *alloc_aligned(size_t align, size_t size, struct memory_type *type)
 {
+	/* Define a large request to be 1024 bytes for either alignment or
+	 * size of allocation. */
+	const size_t large_request = 1024;
+
 	if (size == 0) return 0;
 	if (type->align_regions == 0) {
 		type->align_regions = malloc(sizeof(struct align_region_t));
@@ -396,6 +466,14 @@ static void *alloc_aligned(size_t align, size_t size, struct memory_type *type)
 		memset(type->align_regions, 0, sizeof(struct align_region_t));
 	}
 	struct align_region_t *reg = type->align_regions;
+
+	if (size >= large_request || align >= large_request) {
+		reg = allocate_region(align, 0, size, type);
+		if (reg == NULL)
+			return NULL;
+		return reg->start_data;
+	}
+
 look_further:
 	while (reg != 0)
 	{
@@ -414,7 +492,7 @@ look_further:
 		printf("  need to allocate a new memalign region\n");
 #endif
 		/* get align regions */
-		reg = allocate_region(align, (size<1024)?(1024/align):(((size-1)/align)+1), type);
+		reg = allocate_region(align, large_request/align, size, type);
 #ifdef CONFIG_LP_DEBUG_MALLOC
 		printf("  ... returned %p\n", reg);
 #endif