cbfs: add cbfs_locate_file()

cbfs_locate_file() can be used to locate the data within the
cbfs file. Based on the offset and length of the file it can
then be read into any address without bringing the contents
into another buffer (platforms without memory-mapped access
to entire contents of cbfs at once).

BUG=chrome-os-partner:29922
BRANCH=None
TEST=Built and booted rush into romstage (stage load still works).

Original-Change-Id: I2932f66478c74511ec1c876b09794d9a22a526b3
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/206000
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
(cherry picked from commit 56c958facd379ca0eeebe1b689e3b80d5e692699)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I0c4964132af615a069258c0eb37153bd84fbbfae
Reviewed-on: http://review.coreboot.org/8180
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Furquan Shaikh <furquan@google.com>

2 files changed, 66 insertions, 29 deletions

diff --git a/src/include/cbfs_core.h b/src/include/cbfs_core.h
index e74d618d92..3cef9031ab 100644
--- a/src/include/cbfs_core.h
+++ b/src/include/cbfs_core.h
@@ -217,6 +217,13 @@ struct cbfs_media {
 	int (*close)(struct cbfs_media *media);
 };
 
+/*
+ * Locate file by name and fill in cbfs_file in host byte order. Returns
+ * < 0 on error, else the offset of the file data.
+ */
+ssize_t cbfs_locate_file(struct cbfs_media *media, struct cbfs_file *file,
+				const char *name);
+
 /* returns pointer to a file entry inside CBFS or NULL */
 struct cbfs_file *cbfs_get_file(struct cbfs_media *media, const char *name);
 
diff --git a/src/lib/cbfs_core.c b/src/lib/cbfs_core.c
index 0f97755314..24e5998f71 100644
--- a/src/lib/cbfs_core.c
+++ b/src/lib/cbfs_core.c
@@ -93,25 +93,33 @@ const struct cbfs_header *cbfs_get_header(struct cbfs_media *media)
 	return header;
 }
 
+
+static int init_media(struct cbfs_media **media, struct cbfs_media *backing)
+{
+	if (*media == CBFS_DEFAULT_MEDIA) {
+		*media = backing;
+		if (init_default_cbfs_media(*media) != 0) {
+			ERROR("Failed to initialize default media.\n");
+			return -1;
+		}
+	}
+	return 0;
+}
+
 /* public API starts here*/
-struct cbfs_file *cbfs_get_file(struct cbfs_media *media, const char *name)
+ssize_t cbfs_locate_file(struct cbfs_media *media, struct cbfs_file *file,
+				const char *name)
 {
 	const char *file_name;
 	uint32_t offset, align, romsize, name_len;
 	const struct cbfs_header *header;
-	struct cbfs_file file, *file_ptr;
 	struct cbfs_media default_media;
 
-	if (media == CBFS_DEFAULT_MEDIA) {
-		media = &default_media;
-		if (init_default_cbfs_media(media) != 0) {
-			ERROR("Failed to initialize default media.\n");
-			return NULL;
-		}
-	}
+	if (init_media(&media, &default_media))
+		return -1;
 
 	if (CBFS_HEADER_INVALID_ADDRESS == (header = cbfs_get_header(media)))
-		return NULL;
+		return -1;
 
 	// Logical offset (for source media) of first file.
 	offset = ntohl(header->offset);
@@ -139,9 +147,9 @@ struct cbfs_file *cbfs_get_file(struct cbfs_media *media, const char *name)
 
 	media->open(media);
 	while (offset < romsize &&
-	       media->read(media, &file, offset, sizeof(file)) == sizeof(file)) {
-		if (memcmp(CBFS_FILE_MAGIC, file.magic,
-			   sizeof(file.magic)) != 0) {
+	       media->read(media, file, offset, sizeof(*file)) == sizeof(*file)) {
+		if (memcmp(CBFS_FILE_MAGIC, file->magic,
+			   sizeof(file->magic)) != 0) {
 			uint32_t new_align = align;
 			if (offset % align)
 				new_align += align - (offset % align);
@@ -151,30 +159,25 @@ struct cbfs_file *cbfs_get_file(struct cbfs_media *media, const char *name)
 			offset += new_align;
 			continue;
 		}
-		name_len = ntohl(file.offset) - sizeof(file);
+
+		file->len = ntohl(file->len);
+		file->type= ntohl(file->type);
+		file->offset = ntohl(file->offset);
+
+		name_len = file->offset - sizeof(*file);
 		DEBUG(" - load entry 0x%x file name (%d bytes)...\n", offset,
 		      name_len);
 
 		// load file name (arbitrary length).
 		file_name = (const char *)media->map(
-				media, offset + sizeof(file), name_len);
+				media, offset + sizeof(*file), name_len);
 		if (file_name == CBFS_MEDIA_INVALID_MAP_ADDRESS) {
 			ERROR("ERROR: Failed to get filename: 0x%x.\n", offset);
 		} else if (strcmp(file_name, name) == 0) {
-			int file_offset = ntohl(file.offset),
-			    file_len = ntohl(file.len);
 			DEBUG("Found file (offset=0x%x, len=%d).\n",
-			    offset + file_offset, file_len);
+			    offset + file->offset, file->len);
 			media->unmap(media, file_name);
-			file_ptr = media->map(media, offset,
-					      file_offset + file_len);
-			media->close(media);
-			if (file_ptr == CBFS_MEDIA_INVALID_MAP_ADDRESS) {
-				ERROR("ERROR: Mapping %s failed (insufficient "
-				      "buffer space?).\n", file_name);
-				return NULL;
-			}
-			return file_ptr;
+			return offset + file->offset;
 		} else {
 			DEBUG(" (unmatched file @0x%x: %s)\n", offset,
 			      file_name);
@@ -182,13 +185,40 @@ struct cbfs_file *cbfs_get_file(struct cbfs_media *media, const char *name)
 		}
 
 		// Move to next file.
-		offset += ntohl(file.len) + ntohl(file.offset);
+		offset += file->len + file->offset;
 		if (offset % align)
 			offset += align - (offset % align);
 	}
 	media->close(media);
 	LOG("WARNING: '%s' not found.\n", name);
-	return NULL;
+	return -1;
+}
+
+struct cbfs_file *cbfs_get_file(struct cbfs_media *media, const char *name)
+{
+	struct cbfs_media default_media;
+	struct cbfs_file file, *file_ptr;
+	ssize_t offset;
+
+	if (init_media(&media, &default_media))
+		return NULL;
+
+	offset = cbfs_locate_file(media, &file, name);
+	if (offset < 0)
+		return NULL;
+
+	/* Map both the metadata and the file contents. */
+	media->open(media);
+	offset -= file.offset;
+	file_ptr = media->map(media, offset, file.offset + file.len);
+	media->close(media);
+
+	if (file_ptr == CBFS_MEDIA_INVALID_MAP_ADDRESS) {
+		ERROR("ERROR: Mapping %s failed.\n", name);
+		return NULL;
+	}
+
+	return file_ptr;
 }
 
 void *cbfs_get_file_content(struct cbfs_media *media, const char *name,