--- /dev/null
+/*
+ * Copyright (C) 2017 Google.
+ *
+ * This file is released under the GPLv2.
+ *
+ * Based on drivers/md/dm-verity-chromeos.c
+ */
+
+#include <linux/device-mapper.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+
+#define DM_MSG_PREFIX "verity-avb"
+
+/* Set via module parameters. */
+static char avb_vbmeta_device[64];
+static char avb_invalidate_on_error[4];
+
+static void invalidate_vbmeta_endio(struct bio *bio)
+{
+ if (bio->bi_error)
+ DMERR("invalidate_vbmeta_endio: error %d", bio->bi_error);
+ complete(bio->bi_private);
+}
+
+static int invalidate_vbmeta_submit(struct bio *bio,
+ struct block_device *bdev,
+ int op, int access_last_sector,
+ struct page *page)
+{
+ DECLARE_COMPLETION_ONSTACK(wait);
+
+ bio->bi_private = &wait;
+ bio->bi_end_io = invalidate_vbmeta_endio;
+ bio->bi_bdev = bdev;
+ bio_set_op_attrs(bio, op, REQ_SYNC | REQ_NOIDLE);
+
+ bio->bi_iter.bi_sector = 0;
+ if (access_last_sector) {
+ sector_t last_sector;
+
+ last_sector = (i_size_read(bdev->bd_inode)>>SECTOR_SHIFT) - 1;
+ bio->bi_iter.bi_sector = last_sector;
+ }
+ if (!bio_add_page(bio, page, PAGE_SIZE, 0)) {
+ DMERR("invalidate_vbmeta_submit: bio_add_page error");
+ return -EIO;
+ }
+
+ submit_bio(bio);
+ /* Wait up to 2 seconds for completion or fail. */
+ if (!wait_for_completion_timeout(&wait, msecs_to_jiffies(2000)))
+ return -EIO;
+ return 0;
+}
+
+static int invalidate_vbmeta(dev_t vbmeta_devt)
+{
+ int ret = 0;
+ struct block_device *bdev;
+ struct bio *bio;
+ struct page *page;
+ fmode_t dev_mode;
+ /* Ensure we do synchronous unblocked I/O. We may also need
+ * sync_bdev() on completion, but it really shouldn't.
+ */
+ int access_last_sector = 0;
+
+ DMINFO("invalidate_vbmeta: acting on device %d:%d",
+ MAJOR(vbmeta_devt), MINOR(vbmeta_devt));
+
+ /* First we open the device for reading. */
+ dev_mode = FMODE_READ | FMODE_EXCL;
+ bdev = blkdev_get_by_dev(vbmeta_devt, dev_mode,
+ invalidate_vbmeta);
+ if (IS_ERR(bdev)) {
+ DMERR("invalidate_kernel: could not open device for reading");
+ dev_mode = 0;
+ ret = -ENOENT;
+ goto failed_to_read;
+ }
+
+ bio = bio_alloc(GFP_NOIO, 1);
+ if (!bio) {
+ ret = -ENOMEM;
+ goto failed_bio_alloc;
+ }
+
+ page = alloc_page(GFP_NOIO);
+ if (!page) {
+ ret = -ENOMEM;
+ goto failed_to_alloc_page;
+ }
+
+ access_last_sector = 0;
+ ret = invalidate_vbmeta_submit(bio, bdev, REQ_OP_READ,
+ access_last_sector, page);
+ if (ret) {
+ DMERR("invalidate_vbmeta: error reading");
+ goto failed_to_submit_read;
+ }
+
+ /* We have a page. Let's make sure it looks right. */
+ if (memcmp("AVB0", page_address(page), 4) == 0) {
+ /* Stamp it. */
+ memcpy(page_address(page), "AVE0", 4);
+ DMINFO("invalidate_vbmeta: found vbmeta partition");
+ } else {
+ /* Could be this is on a AVB footer, check. Also, since the
+ * AVB footer is in the last 64 bytes, adjust for the fact that
+ * we're dealing with 512-byte sectors.
+ */
+ size_t offset = (1<<SECTOR_SHIFT) - 64;
+
+ access_last_sector = 1;
+ ret = invalidate_vbmeta_submit(bio, bdev, REQ_OP_READ,
+ access_last_sector, page);
+ if (ret) {
+ DMERR("invalidate_vbmeta: error reading");
+ goto failed_to_submit_read;
+ }
+ if (memcmp("AVBf", page_address(page) + offset, 4) != 0) {
+ DMERR("invalidate_vbmeta on non-vbmeta partition");
+ ret = -EINVAL;
+ goto invalid_header;
+ }
+ /* Stamp it. */
+ memcpy(page_address(page) + offset, "AVE0", 4);
+ DMINFO("invalidate_vbmeta: found vbmeta footer partition");
+ }
+
+ /* Now rewrite the changed page - the block dev was being
+ * changed on read. Let's reopen here.
+ */
+ blkdev_put(bdev, dev_mode);
+ dev_mode = FMODE_WRITE | FMODE_EXCL;
+ bdev = blkdev_get_by_dev(vbmeta_devt, dev_mode,
+ invalidate_vbmeta);
+ if (IS_ERR(bdev)) {
+ DMERR("invalidate_vbmeta: could not open device for writing");
+ dev_mode = 0;
+ ret = -ENOENT;
+ goto failed_to_write;
+ }
+
+ /* We re-use the same bio to do the write after the read. Need to reset
+ * it to initialize bio->bi_remaining.
+ */
+ bio_reset(bio);
+
+ ret = invalidate_vbmeta_submit(bio, bdev, REQ_OP_WRITE,
+ access_last_sector, page);
+ if (ret) {
+ DMERR("invalidate_vbmeta: error writing");
+ goto failed_to_submit_write;
+ }
+
+ DMERR("invalidate_vbmeta: completed.");
+ ret = 0;
+failed_to_submit_write:
+failed_to_write:
+invalid_header:
+ __free_page(page);
+failed_to_submit_read:
+ /* Technically, we'll leak a page with the pending bio, but
+ * we're about to reboot anyway.
+ */
+failed_to_alloc_page:
+ bio_put(bio);
+failed_bio_alloc:
+ if (dev_mode)
+ blkdev_put(bdev, dev_mode);
+failed_to_read:
+ return ret;
+}
+
+void dm_verity_avb_error_handler(void)
+{
+ dev_t dev;
+
+ DMINFO("AVB error handler called for %s", avb_vbmeta_device);
+
+ if (strcmp(avb_invalidate_on_error, "yes") != 0) {
+ DMINFO("Not configured to invalidate");
+ return;
+ }
+
+ if (avb_vbmeta_device[0] == '\0') {
+ DMERR("avb_vbmeta_device parameter not set");
+ goto fail_no_dev;
+ }
+
+ dev = name_to_dev_t(avb_vbmeta_device);
+ if (!dev) {
+ DMERR("No matching partition for device: %s",
+ avb_vbmeta_device);
+ goto fail_no_dev;
+ }
+
+ invalidate_vbmeta(dev);
+
+fail_no_dev:
+ ;
+}
+
+static int __init dm_verity_avb_init(void)
+{
+ DMINFO("AVB error handler initialized with vbmeta device: %s",
+ avb_vbmeta_device);
+ return 0;
+}
+
+static void __exit dm_verity_avb_exit(void)
+{
+}
+
+module_init(dm_verity_avb_init);
+module_exit(dm_verity_avb_exit);
+
+MODULE_AUTHOR("David Zeuthen <zeuthen@google.com>");
+MODULE_DESCRIPTION("AVB-specific error handler for dm-verity");
+MODULE_LICENSE("GPL");
+
+/* Declare parameter with no module prefix */
+#undef MODULE_PARAM_PREFIX
+#define MODULE_PARAM_PREFIX "androidboot.vbmeta."
+module_param_string(device, avb_vbmeta_device, sizeof(avb_vbmeta_device), 0);
+module_param_string(invalidate_on_error, avb_invalidate_on_error,
+ sizeof(avb_invalidate_on_error), 0);
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