1 files changed, 109 insertions, 0 deletions
diff --git a/libblkid/src/superblocks/erofs.c b/libblkid/src/superblocks/erofs.c
new file mode 100644
index 0000000..14d272e
--- /dev/null
+++ b/libblkid/src/superblocks/erofs.c
@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2020 Gao Xiang
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License
+ *
+ * https://docs.kernel.org/filesystems/erofs.html
+ */
+#include <stddef.h>
+#include <string.h>
+
+#include "superblocks.h"
+#include "crc32c.h"
+
+#define EROFS_SUPER_OFFSET      1024
+#define EROFS_SB_KBOFF		(EROFS_SUPER_OFFSET >> 10)
+#define EROFS_FEATURE_SB_CSUM	(1 << 0)
+
+#define EROFS_SUPER_MAGIC_V1	"\xe2\xe1\xf5\xe0"
+#define EROFS_MAGIC_OFF		0
+
+/* All in little-endian */
+struct erofs_super_block {
+	uint32_t	magic;
+	uint32_t	checksum;
+	uint32_t	feature_compat;
+	uint8_t		blkszbits;
+	uint8_t		reserved;
+
+	uint16_t	root_nid;
+	uint64_t	inos;
+
+	uint64_t	build_time;
+	uint32_t	build_time_nsec;
+	uint32_t	blocks;
+	uint32_t	meta_blkaddr;
+	uint32_t	xattr_blkaddr;
+	uint8_t		uuid[16];
+	uint8_t		volume_name[16];
+	uint32_t	feature_incompat;
+	uint8_t		reserved2[44];
+} __attribute__((packed));
+
+static int erofs_verify_checksum(blkid_probe pr, const struct blkid_idmag *mag,
+		const struct erofs_super_block *sb)
+{
+	uint32_t expected, csum;
+	size_t csummed_size;
+	unsigned char *csummed;
+
+	if (!(le32_to_cpu(sb->feature_compat) & EROFS_FEATURE_SB_CSUM))
+		return 1;
+
+	expected = le32_to_cpu(sb->checksum);
+	csummed_size = (1U << sb->blkszbits) - EROFS_SUPER_OFFSET;
+
+	csummed = blkid_probe_get_sb_buffer(pr, mag, csummed_size);
+	if (!csummed)
+		return 0;
+
+	csum = ul_crc32c_exclude_offset(~0L, csummed, csummed_size,
+			                offsetof(struct erofs_super_block, checksum),
+					sizeof_member(struct erofs_super_block, checksum));
+
+	return blkid_probe_verify_csum(pr, csum, expected);
+}
+
+static int probe_erofs(blkid_probe pr, const struct blkid_idmag *mag)
+{
+	struct erofs_super_block *sb;
+
+	sb = blkid_probe_get_sb(pr, mag, struct erofs_super_block);
+	if (!sb)
+		return errno ? -errno : BLKID_PROBE_NONE;
+
+	/* EROFS is restricted to 4KiB block size */
+	if (sb->blkszbits > 31 || (1U << sb->blkszbits) > 4096)
+		return BLKID_PROBE_NONE;
+
+	if (!erofs_verify_checksum(pr, mag, sb))
+		return BLKID_PROBE_NONE;
+
+	if (sb->volume_name[0])
+		blkid_probe_set_label(pr, (unsigned char *)sb->volume_name,
+				      sizeof(sb->volume_name));
+
+	blkid_probe_set_uuid(pr, sb->uuid);
+	blkid_probe_set_fsblocksize(pr, 1U << sb->blkszbits);
+	blkid_probe_set_block_size(pr, 1U << sb->blkszbits);
+	blkid_probe_set_fssize(pr, (uint64_t) (1U << sb->blkszbits) * le32_to_cpu(sb->blocks));
+
+	return BLKID_PROBE_OK;
+}
+
+const struct blkid_idinfo erofs_idinfo =
+{
+	.name           = "erofs",
+	.usage          = BLKID_USAGE_FILESYSTEM,
+	.probefunc      = probe_erofs,
+	.magics         =
+        {
+		{
+			.magic = EROFS_SUPER_MAGIC_V1,
+			.len = 4,
+			.kboff = EROFS_SB_KBOFF,
+			.sboff = EROFS_MAGIC_OFF,
+		}, { NULL }
+	}
+};