Fix erasing of unaligned regionsv1.0.1-rc2v1.0.1

The erase (-E) feature is somehow a brute force method, but still, if we
are given a region to erase, we should make sure to restore surrounding
data if the erase block expands beyond the region.

Slight alteration from `master` commit: Guard free() from NULL pointers
to be regression safe even in case of broken libc.

Change-Id: I5fc35310f0b090f218cd1d660e27fb39dd05c3c5
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/31069
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

1 files changed, 68 insertions, 3 deletions

diff --git a/flashrom.c b/flashrom.c
index 1a7dfb10b..51f97214f 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -1690,17 +1690,82 @@ static int erase_block(struct flashctx *const flashctx,
 		       const struct walk_info *const info, const erasefn_t erasefn)
 {
 	const unsigned int erase_len = info->erase_end + 1 - info->erase_start;
+	const bool region_unaligned = info->region_start > info->erase_start ||
+				      info->erase_end > info->region_end;
+	uint8_t *backup_contents = NULL, *erased_contents = NULL;
+	int ret = 2;
+
+	/*
+	 * If the region is not erase-block aligned, merge current flash con-
+	 * tents into a new buffer `backup_contents`.
+	 */
+	if (region_unaligned) {
+		backup_contents = malloc(erase_len);
+		erased_contents = malloc(erase_len);
+		if (!backup_contents || !erased_contents) {
+			msg_cerr("Out of memory!\n");
+			ret = 1;
+			goto _free_ret;
+		}
+		memset(backup_contents, 0xff, erase_len);
+		memset(erased_contents, 0xff, erase_len);
+
+		msg_cdbg("R");
+		/* Merge data preceding the current region. */
+		if (info->region_start > info->erase_start) {
+			const chipoff_t start	= info->erase_start;
+			const chipsize_t len	= info->region_start - info->erase_start;
+			if (flashctx->chip->read(flashctx, backup_contents, start, len)) {
+				msg_cerr("Can't read! Aborting.\n");
+				goto _free_ret;
+			}
+		}
+		/* Merge data following the current region. */
+		if (info->erase_end > info->region_end) {
+			const chipoff_t start     = info->region_end + 1;
+			const chipoff_t rel_start = start - info->erase_start; /* within this erase block */
+			const chipsize_t len      = info->erase_end - info->region_end;
+			if (flashctx->chip->read(flashctx, backup_contents + rel_start, start, len)) {
+				msg_cerr("Can't read! Aborting.\n");
+				goto _free_ret;
+			}
+		}
+	}
 
+	ret = 1;
 	all_skipped = false;
 
 	msg_cdbg("E");
 	if (erasefn(flashctx, info->erase_start, erase_len))
-		return 1;
+		goto _free_ret;
 	if (check_erased_range(flashctx, info->erase_start, erase_len)) {
 		msg_cerr("ERASE FAILED!\n");
-		return 1;
+		goto _free_ret;
 	}
-	return 0;
+
+	if (region_unaligned) {
+		unsigned int starthere = 0, lenhere = 0, writecount = 0;
+		/* get_next_write() sets starthere to a new value after the call. */
+		while ((lenhere = get_next_write(erased_contents + starthere, backup_contents + starthere,
+						 erase_len - starthere, &starthere, flashctx->chip->gran))) {
+			if (!writecount++)
+				msg_cdbg("W");
+			/* Needs the partial write function signature. */
+			if (flashctx->chip->write(flashctx, backup_contents + starthere,
+						  info->erase_start + starthere, lenhere))
+				goto _free_ret;
+			starthere += lenhere;
+		}
+	}
+
+	ret = 0;
+
+_free_ret:
+	if (erased_contents != NULL)
+		free(erased_contents);
+	if (backup_contents != NULL)
+		free(backup_contents);
+	return ret;
 }
 
 /**