coreboot: add memory pool infrastructure

The memory pool infrastructure provides an allocator with
very simple free()ing semantics: only the most recent allocation
can be freed from the pool. However, it can be reset and when
not used any longer providing the entire region for future
allocations.

Change-Id: I5ae9ab35bb769d78bbc2866c5ae3b5ce2cdce5fa
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/9129
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

3 files changed, 129 insertions, 0 deletions

diff --git a/src/include/mem_pool.h b/src/include/mem_pool.h
new file mode 100644
index 0000000000..c57b70761e
--- /dev/null
+++ b/src/include/mem_pool.h
@@ -0,0 +1,73 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2015 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc.
+ */
+
+#ifndef _MEM_POOL_H_
+#define _MEM_POOL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * The memory pool allows one to allocate memory from a fixed size buffer
+ * that also allows freeing semantics for reuse. However, the current
+ * limitation is that the most recent allocation is the only one that
+ * can be freed. If one tries to free any allocation that isn't the
+ * most recently allocated it will result in a leak within the memory pool.
+ *
+ * The memory returned by allocations are at least 8 byte aligned. Note
+ * that this requires the backing buffer to start on at least an 8 byte
+ * alignment.
+ */
+
+struct mem_pool {
+	uint8_t *buf;
+	size_t size;
+	uint8_t *last_alloc;
+	size_t free_offset;
+};
+
+#define MEM_POOL_INIT(buf_, size_)	\
+	{				\
+		.buf = (buf_),		\
+		.size = (size_),	\
+		.last_alloc = NULL,	\
+		.free_offset = 0,	\
+	}
+
+static inline void mem_pool_reset(struct mem_pool *mp)
+{
+	mp->last_alloc = NULL;
+	mp->free_offset = 0;
+}
+
+/* Initialize a memory pool. */
+static inline void mem_pool_init(struct mem_pool *mp, void *buf, size_t sz)
+{
+	mp->buf = buf;
+	mp->size = sz;
+	mem_pool_reset(mp);
+}
+
+/* Allocate requested size from the memory pool. NULL returned on error. */
+void *mem_pool_alloc(struct mem_pool *mp, size_t sz);
+
+/* Free allocation from memory pool. */
+void mem_pool_free(struct mem_pool *mp, void *alloc);
+
+#endif /* _MEM_POOL_H_ */
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index c547c70ae4..88254b9693 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -29,6 +29,7 @@ bootblock-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
 bootblock-$(CONFIG_CONSOLE_CBMEM) += cbmem_console.c
 bootblock-y += memchr.c
 bootblock-y += memcmp.c
+bootblock-y += mem_pool.c
 bootblock-y += region.c
 
 verstage-y += prog_ops.c
@@ -50,6 +51,7 @@ endif
 
 verstage-$(CONFIG_GENERIC_UDELAY) += timer.c
 verstage-$(CONFIG_GENERIC_GPIO_LIB) += gpio.c
+verstage-y += mem_pool.c
 
 romstage-y += prog_ops.c
 romstage-y += memchr.c
@@ -134,6 +136,9 @@ ramstage-$(CONFIG_RELOCATABLE_RAMSTAGE) += cbmem_stage_cache.c
 romstage-$(CONFIG_RELOCATABLE_RAMSTAGE) += cbmem_stage_cache.c
 endif
 
+romstage-y += mem_pool.c
+ramstage-y += mem_pool.c
+
 romstage-y += region.c
 ramstage-y += region.c
 
diff --git a/src/lib/mem_pool.c b/src/lib/mem_pool.c
new file mode 100644
index 0000000000..4bd0668358
--- /dev/null
+++ b/src/lib/mem_pool.c
@@ -0,0 +1,51 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2015 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc.
+ */
+
+#include <mem_pool.h>
+#include <stdlib.h>
+
+void *mem_pool_alloc(struct mem_pool *mp, size_t sz)
+{
+	void *p;
+
+	/* Make all allocations be at least 8 byte aligned. */
+	sz = ALIGN_UP(sz, 8);
+
+	/* Determine if any space available. */
+	if ((mp->size - mp->free_offset) < sz)
+		return NULL;
+
+	p = &mp->buf[mp->free_offset];
+
+	mp->free_offset += sz;
+	mp->last_alloc = p;
+
+	return p;
+}
+
+void mem_pool_free(struct mem_pool *mp, void *p)
+{
+	/* Determine if p was the most recent allocation. */
+	if (p == NULL || mp->last_alloc != p)
+		return;
+
+	mp->free_offset = mp->last_alloc - mp->buf;
+	/* No way to track allocation before this one. */
+	mp->last_alloc = NULL;
+}