CBFS: Change how the bss is zeroed when loading a stage.

For reasons explained in a previous CL, it might be necessary to "load" a file
from CBFS in place. The loading code in CBFS was, however, zeroing the area of
memory the stage was about to be loaded into. When the CBFS data is located
elsewhere this works fine, but when it isn't you end up clobbering the data
you're trying to load. Also, there's no reason to zero memory we're about to
load something into or have just loaded something into. This change makes it
so that we only zero out the portion of the memory between what was
loaded/decompressed and the final size of the stage in memory.

Change-Id: If34df16bd74b2969583e11ef6a26eb4065842f57
Signed-off-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: http://review.coreboot.org/3579
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/cbfs.c b/src/lib/cbfs.c
index 400b8a5f9d..f48d887d87 100644
--- a/src/lib/cbfs.c
+++ b/src/lib/cbfs.c
@@ -268,8 +268,6 @@ void * cbfs_load_stage(struct cbfs_media *media, const char *name)
 			name,
 			(uint32_t) stage->load, stage->memlen,
 			stage->entry);
-	/* Stages rely the below clearing so that the bss is initialized. */
-	memset((void *) (uint32_t) stage->load, 0, stage->memlen);
 
 	final_size = cbfs_decompress(stage->compression,
 				     ((unsigned char *) stage) +
@@ -279,6 +277,10 @@ void * cbfs_load_stage(struct cbfs_media *media, const char *name)
 	if (!final_size)
 		return (void *) -1;
 
+	/* Stages rely the below clearing so that the bss is initialized. */
+	memset((void *)((uintptr_t)stage->load + final_size), 0,
+	       stage->memlen - final_size);
+
 	DEBUG("stage loaded.\n");
 
 	entry = stage->entry;