cbfs: Add metadata cache

This patch adds a new CBFS "mcache" (metadata cache) -- a memory buffer
that stores the headers of all CBFS files. Similar to the existing FMAP
cache, this cache should reduce the amount of SPI accesses we need to do
every boot: rather than having to re-read all CBFS headers from SPI
flash every time we're looking for a file, we can just walk the same
list in this in-memory copy and finally use it to directly access the
flash at the right position for the file data.

This patch adds the code to support the cache but doesn't enable it on
any platform. The next one will turn it on by default.

Change-Id: I5b1084bfdad1c6ab0ee1b143ed8dd796827f4c65
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38423
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

2 files changed, 22 insertions, 0 deletions

diff --git a/src/commonlib/bsd/include/commonlib/bsd/cb_err.h b/src/commonlib/bsd/include/commonlib/bsd/cb_err.h
index e5aa852617..b61b956524 100644
--- a/src/commonlib/bsd/include/commonlib/bsd/cb_err.h
+++ b/src/commonlib/bsd/include/commonlib/bsd/cb_err.h
@@ -39,6 +39,7 @@ enum cb_err {
 	CB_CBFS_IO		= -400, /**< Underlying I/O error */
 	CB_CBFS_NOT_FOUND	= -401, /**< File not found in directory */
 	CB_CBFS_HASH_MISMATCH	= -402, /**< Master hash validation failed */
+	CB_CBFS_CACHE_FULL	= -403, /**< Metadata cache overflowed */
 };
 
 /* Don't typedef the enum directly, so the size is unambiguous for serialization. */
diff --git a/src/commonlib/bsd/include/commonlib/bsd/cbfs_private.h b/src/commonlib/bsd/include/commonlib/bsd/cbfs_private.h
index aaee62f4c3..64dcf9f5ba 100644
--- a/src/commonlib/bsd/include/commonlib/bsd/cbfs_private.h
+++ b/src/commonlib/bsd/include/commonlib/bsd/cbfs_private.h
@@ -113,4 +113,25 @@ cb_err_t cbfs_copy_fill_metadata(union cbfs_mdata *dst, const union cbfs_mdata *
 cb_err_t cbfs_lookup(cbfs_dev_t dev, const char *name, union cbfs_mdata *mdata_out,
 		     size_t *data_offset_out, struct vb2_hash *metadata_hash);
 
+/* Both base address and size of CBFS mcaches must be aligned to this value! */
+#define CBFS_MCACHE_ALIGNMENT	sizeof(uint32_t)	/* Largest data type used in CBFS */
+
+/* Build an in-memory CBFS metadata cache out of the CBFS on |dev| into a |mcache_size| bytes
+ * memory area at |mcache|. Also verify |metadata_hash| unless it is NULL. If this returns
+ * CB_CBFS_CACHE_FULL, the mcache is still valid and can be used, but lookups may return
+ * CB_CBFS_CACHE_FULL for files that didn't fit to indicate that the caller needs to fall back
+ * to cbfs_lookup(). */
+cb_err_t cbfs_mcache_build(cbfs_dev_t dev, void *mcache, size_t mcache_size,
+			   struct vb2_hash *metadata_hash);
+
+/*
+ * Find a file named |name| in a CBFS metadata cache and copy its metadata into |mdata_out|.
+ * Pass out offset to the file data (on the original CBFS device used for cbfs_mcache_build()).
+ */
+cb_err_t cbfs_mcache_lookup(const void *mcache, size_t mcache_size, const char *name,
+			    union cbfs_mdata *mdata_out, size_t *data_offset_out);
+
+/* Returns the amount of bytes actually used by the CBFS metadata cache in |mcache|. */
+size_t cbfs_mcache_real_size(const void *mcache, size_t mcache_size);
+
 #endif	/* _COMMONLIB_BSD_CBFS_PRIVATE_H_ */