image_decompress: add APIs for decompressing images

These APIs are used by platforms that need to decompress images.

image_decompress_init():
  This registers a temporary buffer and a decompressor callback.
  This should be called from platform init code.

image_decompress_prepare():
  This should be called before each compressed image is loaded.  The
  best location to call this will be bl*_plat_handle_pre_image_load().

image_decompress():
  This should be called after each compressed image is loaded.  The
  best location to call this will be bl*_plat_handle_post_image_load().
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

common/image_decompress.c

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch_helpers.h>
+#include <assert.h>
+#include <bl_common.h>
+#include <debug.h>
+#include <image_decompress.h>
+#include <stdint.h>
+
+static uintptr_t decompressor_buf_base;
+static uint32_t decompressor_buf_size;
+static decompressor_t *decompressor;
+static struct image_info saved_image_info;
+
+void image_decompress_init(uintptr_t buf_base, uint32_t buf_size,
+			   decompressor_t *_decompressor)
+{
+	decompressor_buf_base = buf_base;
+	decompressor_buf_size = buf_size;
+	decompressor = _decompressor;
+}
+
+void image_decompress_prepare(struct image_info *info)
+{
+	/*
+	 * If the image is compressed, it should be loaded into the temporary
+	 * buffer instead of its final destination.  We save image_info, then
+	 * override ->image_base and ->image_max_size so that load_image() will
+	 * transfer the compressed data to the temporary buffer.
+	 */
+	saved_image_info = *info;
+	info->image_base = decompressor_buf_base;
+	info->image_max_size = decompressor_buf_size;
+}
+
+int image_decompress(struct image_info *info)
+{
+	uintptr_t compressed_image_base, image_base, work_base;
+	uint32_t compressed_image_size, work_size;
+	int ret;
+
+	/*
+	 * The size of compressed data has been filled by load_image().
+	 * Read it out before restoring image_info.
+	 */
+	compressed_image_size = info->image_size;
+	compressed_image_base = info->image_base;
+	*info = saved_image_info;
+
+	assert(compressed_image_size <= decompressor_buf_size);
+
+	image_base = info->image_base;
+
+	/*
+	 * Use the rest of the temporary buffer as workspace of the
+	 * decompressor since the decompressor may need additional memory.
+	 */
+	work_base = compressed_image_base + compressed_image_size;
+	work_size = decompressor_buf_size - compressed_image_size;
+
+	ret = decompressor(&compressed_image_base, compressed_image_size,
+			   &image_base, info->image_max_size,
+			   work_base, work_size);
+	if (ret) {
+		ERROR("Failed to decompress image (err=%d)\n", ret);
+		return ret;
+	}
+
+	/* image_base is updated to the final pos when decompressor() exits. */
+	info->image_size = image_base - info->image_base;
+
+	flush_dcache_range(info->image_base, info->image_size);
+
+	return 0;
+}

include/common/image_decompress.h

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __IMAGE_DECOMPRESS_H__
+#define __IMAGE_DECOMPRESS_H__
+
+#include <stddef.h>
+#include <stdint.h>
+
+struct image_info;
+
+typedef int (decompressor_t)(uintptr_t *in_buf, size_t in_len,
+			     uintptr_t *out_buf, size_t out_len,
+			     uintptr_t work_buf, size_t work_len);
+
+void image_decompress_init(uintptr_t buf_base, uint32_t buf_size,
+			   decompressor_t *decompressor);
+void image_decompress_prepare(struct image_info *info);
+int image_decompress(struct image_info *info);
+
+#endif /* __IMAGE_DECOMPRESS_H___ */