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Zero out blocks that may be touched by dm-verity.

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dm-verity may touch some blocks that are not in the care_map due to
block device read-ahead. It will fail if such blocks contain
non-zeroes. As a workaround, we mark them as extended blocks and
zero out explicitly to avoid dm-verity failures.

Bug: 20881595
Change-Id: I54e24e70ad822c0d6d7af43301f74d24505f4461
This commit is contained in:
Tao Bao
2015-07-09 17:37:49 -07:00
parent 2a3a2dc33c
commit 2fd2c9bfd6
4 changed files with 73 additions and 14 deletions
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27
tools/releasetools/blockimgdiff.py
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@@ -83,6 +83,7 @@ class EmptyImage(Image):
blocksize = 4096
care_map = RangeSet()
clobbered_blocks = RangeSet()
extended = RangeSet()
total_blocks = 0
file_map = {}
def ReadRangeSet(self, ranges):
@@ -119,6 +120,7 @@ class DataImage(Image):
self.total_blocks = len(self.data) / self.blocksize
self.care_map = RangeSet(data=(0, self.total_blocks))
self.clobbered_blocks = RangeSet()
self.extended = RangeSet()
zero_blocks = []
nonzero_blocks = []
@@ -411,7 +413,7 @@ class BlockImageDiff(object):
elif self.version >= 3:
# take into account automatic stashing of overlapping blocks
if xf.src_ranges.overlaps(xf.tgt_ranges):
temp_stash_usage = stashed_blocks + xf.src_ranges.size();
temp_stash_usage = stashed_blocks + xf.src_ranges.size()
if temp_stash_usage > max_stashed_blocks:
max_stashed_blocks = temp_stash_usage
@@ -435,7 +437,7 @@ class BlockImageDiff(object):
elif self.version >= 3:
# take into account automatic stashing of overlapping blocks
if xf.src_ranges.overlaps(xf.tgt_ranges):
temp_stash_usage = stashed_blocks + xf.src_ranges.size();
temp_stash_usage = stashed_blocks + xf.src_ranges.size()
if temp_stash_usage > max_stashed_blocks:
max_stashed_blocks = temp_stash_usage
@@ -462,18 +464,17 @@ class BlockImageDiff(object):
# stash space
assert max_stashed_blocks * self.tgt.blocksize < (512 << 20)
# Zero out extended blocks as a workaround for bug 20881595.
if self.tgt.extended:
out.append("zero %s\n" % (self.tgt.extended.to_string_raw(),))
# We erase all the blocks on the partition that a) don't contain useful
# data in the new image and b) will not be touched by dm-verity.
all_tgt = RangeSet(data=(0, self.tgt.total_blocks))
if performs_read:
# if some of the original data is used, then at the end we'll
# erase all the blocks on the partition that don't contain data
# in the new image.
new_dontcare = all_tgt.subtract(self.tgt.care_map)
if new_dontcare:
out.append("erase %s\n" % (new_dontcare.to_string_raw(),))
else:
# if nothing is read (ie, this is a full OTA), then we can start
# by erasing the entire partition.
out.insert(0, "erase %s\n" % (all_tgt.to_string_raw(),))
all_tgt_minus_extended = all_tgt.subtract(self.tgt.extended)
new_dontcare = all_tgt_minus_extended.subtract(self.tgt.care_map)
if new_dontcare:
out.append("erase %s\n" % (new_dontcare.to_string_raw(),))
out.insert(0, "%d\n" % (self.version,)) # format version number
out.insert(1, str(total) + "\n")