[coreboot-gerrit] New patch to review for coreboot: e04ee9d CBFS: Change how the bss is zeroed when loading a stage.

[Gabe Black]

Gabe Black ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/3579

-gerrit

commit e04ee9d8eb326f70ae60f31ea202e2797a584927
Author: Gabe Black 
Date:   Mon Jul 1 04:34:29 2013 -0700

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 
---
 payloads/libpayload/libcbfs/cbfs.c | 16 ++++++++++------
 src/lib/cbfs.c                     |  6 ++++--
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/payloads/libpayload/libcbfs/cbfs.c b/payloads/libpayload/libcbfs/cbfs.c
index 6243473..4dfe30a 100644
--- a/payloads/libpayload/libcbfs/cbfs.c
+++ b/payloads/libpayload/libcbfs/cbfs.c
@@ -136,6 +136,7 @@ void * cbfs_load_stage(struct cbfs_media *media, const char *name)
    /* this is a mess. There is no ntohll. */
    /* for now, assume compatible byte order until we solve this. */
    uint32_t entry;
+	uint32_t final_size;

if (stage == NULL)
    	return (void *) -1;
@@ -144,15 +145,18 @@ void * cbfs_load_stage(struct cbfs_media *media, const char *name)
    		name,
    		(uint32_t) stage->load, stage->memlen,
    		stage->entry);
-	memset((void *) (uint32_t) stage->load, 0, stage->memlen);

-	if (!cbfs_decompress(stage->compression,
-			     ((unsigned char *) stage) +
-			     sizeof(struct cbfs_stage),
-			     (void *) (uint32_t) stage->load,
-			     stage->len))
+	final_size = cbfs_decompress(stage->compression,
+				     ((unsigned char *) stage) +
+				     sizeof(struct cbfs_stage),
+				     (void *) (uint32_t) stage->load,
+				     stage->len);
+	if (!final_size)
    	return (void *) -1;

+	memset((void *)((uintptr_t)stage->load + final_size), 0,
+	       stage->memlen - final_size);
+
    DEBUG("stage loaded.\n");

entry = stage->entry;
diff --git a/src/lib/cbfs.c b/src/lib/cbfs.c
index 400b8a5..f48d887 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;