[PATCH-v5] erofs-utils:code for calculating crc checksum of erofs blocks

[Pratik Shinde <pratikshinde320@gmail.com>]

Added code for calculating crc of erofs blocks (4K size).for now it calculates
checksum of first block. but can modified to calculate crc for any no. of blocks

Fill 'feature_compat' field of erofs_super_block so that it
can be used on kernel side. also fixing one typo.

Signed-off-by: Pratik Shinde <pratikshinde320@gmail.com>
---
 include/erofs/internal.h |  1 +
 include/erofs/io.h       |  8 ++++++
 include/erofs_fs.h       |  5 ++--
 lib/io.c                 | 27 ++++++++++++++++++
 mkfs/main.c              | 71 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 110 insertions(+), 2 deletions(-)

diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index 5384946..53335bc 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -55,6 +55,7 @@ struct erofs_sb_info {
 	u32 feature_incompat;
 	u64 build_time;
 	u32 build_time_nsec;
+	u32 feature;
 };
 
 /* global sbi */
diff --git a/include/erofs/io.h b/include/erofs/io.h
index 9775047..e0ca8d9 100644
--- a/include/erofs/io.h
+++ b/include/erofs/io.h
@@ -19,6 +19,7 @@
 int dev_open(const char *devname);
 void dev_close(void);
 int dev_write(const void *buf, u64 offset, size_t len);
+int dev_read(void *buf, u64 offset, size_t len);
 int dev_fillzero(u64 offset, size_t len, bool padding);
 int dev_fsync(void);
 int dev_resize(erofs_blk_t nblocks);
@@ -31,5 +32,12 @@ static inline int blk_write(const void *buf, erofs_blk_t blkaddr,
 			 blknr_to_addr(nblocks));
 }
 
+static inline int blk_read(void *buf, erofs_blk_t start,
+			    u32 nblocks)
+{
+	return dev_read(buf, blknr_to_addr(start),
+			 blknr_to_addr(nblocks));
+}
+
 #endif
 
diff --git a/include/erofs_fs.h b/include/erofs_fs.h
index f29aa25..9eda6c2 100644
--- a/include/erofs_fs.h
+++ b/include/erofs_fs.h
@@ -19,6 +19,7 @@
  */
 #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING	0x00000001
 #define EROFS_ALL_FEATURE_INCOMPAT		EROFS_FEATURE_INCOMPAT_LZ4_0PADDING
+#define EROFS_FEATURE_SB_CHKSUM	0x0001
 
 /* 128-byte erofs on-disk super block */
 struct erofs_super_block {
@@ -39,8 +40,8 @@ struct erofs_super_block {
 	__u8 uuid[16];          /* 128-bit uuid for volume */
 	__u8 volume_name[16];   /* volume name */
 	__le32 feature_incompat;
-
-	__u8 reserved2[44];
+	__le32 chksum_blocks;	/* number of blocks used for checksum */
+	__u8 reserved2[40];
 };
 
 /*
diff --git a/lib/io.c b/lib/io.c
index 7f5f94d..52f9424 100644
--- a/lib/io.c
+++ b/lib/io.c
@@ -207,3 +207,30 @@ int dev_resize(unsigned int blocks)
 	return dev_fillzero(st.st_size, length, true);
 }
 
+int dev_read(void *buf, u64 offset, size_t len)
+{
+	int ret;
+
+	if (cfg.c_dry_run)
+		return 0;
+
+	if (!buf) {
+		erofs_err("buf is NULL");
+		return -EINVAL;
+	}
+	if (offset >= erofs_devsz || len > erofs_devsz ||
+	    offset > erofs_devsz - len) {
+		erofs_err("read posion[%" PRIu64 ", %zd] is too large beyond"
+			  "the end of device(%" PRIu64 ").",
+			  offset, len, erofs_devsz);
+		return -EINVAL;
+	}
+
+	ret = pread64(erofs_devfd, buf, len, (off64_t)offset);
+	if (ret != (int)len) {
+		erofs_err("Failed to read data from device - %s:[%" PRIu64 ", %zd].",
+			  erofs_devname, offset, len);
+		return -errno;
+	}
+	return 0;
+}
diff --git a/mkfs/main.c b/mkfs/main.c
index 91a018f..c7cb923 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -22,6 +22,9 @@
 
 #define EROFS_SUPER_END (EROFS_SUPER_OFFSET + sizeof(struct erofs_super_block))
 
+/* number of blocks for calculating checksum */
+#define EROFS_CKSUM_BLOCKS	1
+
 static void usage(void)
 {
 	fprintf(stderr, "usage: [options] FILE DIRECTORY\n\n");
@@ -85,6 +88,10 @@ static int parse_extended_opts(const char *opts)
 				return -EINVAL;
 			cfg.c_force_inodeversion = FORCE_INODE_EXTENDED;
 		}
+
+		if (MATCH_EXTENTED_OPT("nocrc", token, keylen)) {
+			sbi.feature &= ~EROFS_FEATURE_SB_CHKSUM;
+		}
 	}
 	return 0;
 }
@@ -180,6 +187,9 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
 		.meta_blkaddr  = sbi.meta_blkaddr,
 		.xattr_blkaddr = 0,
 		.feature_incompat = cpu_to_le32(sbi.feature_incompat),
+		.feature_compat = cpu_to_le32(sbi.feature),
+		.checksum = 0,
+		.chksum_blocks = cpu_to_le32(EROFS_CKSUM_BLOCKS)
 	};
 	const unsigned int sb_blksize =
 		round_up(EROFS_SUPER_END, EROFS_BLKSIZ);
@@ -202,6 +212,64 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
 	return 0;
 }
 
+#define CRCPOLY	0x82F63B78
+static inline u32 crc32c(u32 seed, unsigned char const *in, size_t len)
+{
+	int i;
+	u32 crc = seed;
+
+	while (len--) {
+		crc ^= *in++;
+		for (i = 0; i < 8; i++) {
+			crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY : 0);
+		}
+	}
+	return crc;
+}
+
+/* calculate checksum for first n blocks */
+u32 erofs_calc_blk_checksum(erofs_blk_t nblks, u32 *crc)
+{
+	char *buf;
+	int err = 0;
+
+	buf = malloc(nblks * EROFS_BLKSIZ);
+	err = blk_read(buf, 0, nblks);
+	if (err) {
+		return err;
+	}
+	*crc = crc32c(0, (const unsigned char *)buf, nblks * EROFS_BLKSIZ);
+	free(buf);
+	return 0;
+}
+
+void erofs_write_sb_checksum()
+{
+	struct erofs_super_block *sb;
+	char buf[EROFS_BLKSIZ];
+	int ret = 0;
+	u32 crc;
+
+	ret = erofs_calc_blk_checksum(EROFS_CKSUM_BLOCKS, &crc);
+	if (ret) {
+		return;
+	}
+	ret = blk_read(buf, 0, 1);
+	if (ret) {
+		return;
+	}
+
+	sb = (struct erofs_super_block *)((u8 *)buf + EROFS_SUPER_OFFSET);
+	if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) {
+		return;
+	}
+	sb->checksum = cpu_to_le32(crc);
+	ret = blk_write(buf, 0, 1);
+	if (ret) {
+		return;
+	}
+}
+
 int main(int argc, char **argv)
 {
 	int err = 0;
@@ -217,6 +285,7 @@ int main(int argc, char **argv)
 
 	cfg.c_legacy_compress = false;
 	sbi.feature_incompat = EROFS_FEATURE_INCOMPAT_LZ4_0PADDING;
+	sbi.feature = EROFS_FEATURE_SB_CHKSUM;
 
 	err = mkfs_parse_options_cfg(argc, argv);
 	if (err) {
@@ -301,6 +370,8 @@ int main(int argc, char **argv)
 		err = -EIO;
 	else
 		err = dev_resize(nblocks);
+	if (sbi.feature & EROFS_FEATURE_SB_CHKSUM)
+		erofs_write_sb_checksum();
 exit:
 	z_erofs_compress_exit();
 	dev_close();
-- 
2.9.3