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fastbootd: copy AVB footer on boot image to end of block device 

If the flashed boot image is smaller than the block device, the AVB
footer will not be at the end of the partition. Although images are
normally created to match the partition size the GKI boot.img must work
on all devices, and the size of the boot partition will vary.

Copy the AVB footer to the end of the partition before flashing, if it
is not there already.

Bug: 156036850
Change-Id: I11f0c7d32d1b6c74edd4f84f815d175605280cb8
This commit is contained in:
Steve Muckle 2020-05-12 16:21:41 -07:00
parent 18da289fac
commit a9b3443e53
2 changed files with 30 additions and 1 deletions
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1
fastboot/Android.bp
View File

@ -149,6 +149,7 @@ cc_binary {
],
header_libs: [
"avb_headers",
"libsnapshot_headers",
]
}

30
fastboot/device/flashing.cpp
View File

@ -31,6 +31,7 @@
#include <ext4_utils/ext4_utils.h>
#include <fs_mgr_overlayfs.h>
#include <fstab/fstab.h>
#include <libavb/libavb.h>
#include <liblp/builder.h>
#include <liblp/liblp.h>
#include <libsnapshot/snapshot.h>
@ -122,6 +123,27 @@ int FlashBlockDevice(int fd, std::vector<char>& downloaded_data) {
}
}
static void CopyAVBFooter(std::vector<char>* data, const uint64_t block_device_size) {
if (data->size() < AVB_FOOTER_SIZE) {
return;
}
std::string footer;
uint64_t footer_offset = data->size() - AVB_FOOTER_SIZE;
for (int idx = 0; idx < AVB_FOOTER_MAGIC_LEN; idx++) {
footer.push_back(data->at(footer_offset + idx));
}
if (0 != footer.compare(AVB_FOOTER_MAGIC)) {
return;
}
// copy AVB footer from end of data to end of block device
uint64_t original_data_size = data->size();
data->resize(block_device_size, 0);
for (int idx = 0; idx < AVB_FOOTER_SIZE; idx++) {
data->at(block_device_size - 1 - idx) = data->at(original_data_size - 1 - idx);
}
}
int Flash(FastbootDevice* device, const std::string& partition_name) {
PartitionHandle handle;
if (!OpenPartition(device, partition_name, &handle)) {
@ -131,8 +153,14 @@ int Flash(FastbootDevice* device, const std::string& partition_name) {
std::vector<char> data = std::move(device->download_data());
if (data.size() == 0) {
return -EINVAL;
} else if (data.size() > get_block_device_size(handle.fd())) {
}
uint64_t block_device_size = get_block_device_size(handle.fd());
if (data.size() > block_device_size) {
return -EOVERFLOW;
} else if (data.size() < block_device_size &&
(partition_name == "boot" || partition_name == "boot_a" ||
partition_name == "boot_b")) {
CopyAVBFooter(&data, block_device_size);
}
WipeOverlayfsForPartition(device, partition_name);
int result = FlashBlockDevice(handle.fd(), data);