[PATCH v10 1/2] erofs-utils: support calculating checksum of superblock
Gao Xiang
gaoxiang25 at huawei.com
Thu Nov 7 15:03:26 AEDT 2019
From: Pratik Shinde <pratikshinde320 at gmail.com>
Added code for calculating crc of superblock.
Note that the first 1024 bytes are not checksummed to allow
for the installation of x86 boot sectors and other oddities.
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 at gmail.com>
Reviewed-by: Chao Yu <yuchao0 at huawei.com>
Cc: Li Guifu <bluce.liguifu at huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
---
changes since v9:
- fix a typo found by checkpatch "checksumed" -> "checksummed";
- update commit message since it's now limited to superblock;
- update function name "erofs_superblock_csum_set" ->
"erofs_mkfs_superblock_csum_set".
(I'd like to apply this version finally if no more comments...)
include/erofs/internal.h | 1 +
include/erofs/io.h | 8 +++++
include/erofs_fs.h | 3 +-
lib/io.c | 27 ++++++++++++++++
mkfs/main.c | 69 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 107 insertions(+), 1 deletion(-)
diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index 25ce7b54442d..9e2bb9ce33b6 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -52,6 +52,7 @@ struct erofs_sb_info {
erofs_blk_t meta_blkaddr;
erofs_blk_t xattr_blkaddr;
+ u32 feature_compat;
u32 feature_incompat;
u64 build_time;
u32 build_time_nsec;
diff --git a/include/erofs/io.h b/include/erofs/io.h
index 97750478b5ab..e0ca8d949130 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 f29aa2516a99..bcc4f0c630ad 100644
--- a/include/erofs_fs.h
+++ b/include/erofs_fs.h
@@ -13,6 +13,8 @@
#define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
#define EROFS_SUPER_OFFSET 1024
+#define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
+
/*
* Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
* be incompatible with this kernel version.
@@ -39,7 +41,6 @@ struct erofs_super_block {
__u8 uuid[16]; /* 128-bit uuid for volume */
__u8 volume_name[16]; /* volume name */
__le32 feature_incompat;
-
__u8 reserved2[44];
};
diff --git a/lib/io.c b/lib/io.c
index 7f5f94dd6b1e..52f9424d201b 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 ab57896e9ca8..9187c43ed671 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -109,6 +109,12 @@ static int parse_extended_opts(const char *opts)
return -EINVAL;
cfg.c_force_inodeversion = FORCE_INODE_EXTENDED;
}
+
+ if (MATCH_EXTENTED_OPT("nosbcrc", token, keylen)) {
+ if (vallen)
+ return -EINVAL;
+ sbi.feature_compat &= ~EROFS_FEATURE_COMPAT_SB_CHKSUM;
+ }
}
return 0;
}
@@ -218,6 +224,8 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
.meta_blkaddr = sbi.meta_blkaddr,
.xattr_blkaddr = sbi.xattr_blkaddr,
.feature_incompat = cpu_to_le32(sbi.feature_incompat),
+ .feature_compat = cpu_to_le32(sbi.feature_compat &
+ ~EROFS_FEATURE_COMPAT_SB_CHKSUM),
};
const unsigned int sb_blksize =
round_up(EROFS_SUPER_END, EROFS_BLKSIZ);
@@ -240,6 +248,63 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh,
return 0;
}
+#define CRC32C_POLY_LE 0x82F63B78
+static inline u32 crc32c(u32 crc, const u8 *in, size_t len)
+{
+ int i;
+
+ while (len--) {
+ crc ^= *in++;
+ for (i = 0; i < 8; i++)
+ crc = (crc >> 1) ^ ((crc & 1) ? CRC32C_POLY_LE : 0);
+ }
+ return crc;
+}
+
+static int erofs_mkfs_superblock_csum_set(void)
+{
+ int ret;
+ u8 buf[EROFS_BLKSIZ];
+ u32 crc;
+ struct erofs_super_block *sb;
+
+ ret = blk_read(buf, 0, 1);
+ if (ret) {
+ erofs_err("failed to read superblock to set checksum: %s",
+ erofs_strerror(ret));
+ return ret;
+ }
+
+ /*
+ * skip the first 1024 bytes, to allow for the installation
+ * of x86 boot sectors and other oddities.
+ */
+ sb = (struct erofs_super_block *)(buf + EROFS_SUPER_OFFSET);
+
+ if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) {
+ erofs_err("internal error: not an erofs valid image");
+ return -EFAULT;
+ }
+
+ /* turn on checksum feature */
+ sb->feature_compat = cpu_to_le32(le32_to_cpu(sb->feature_compat) |
+ EROFS_FEATURE_COMPAT_SB_CHKSUM);
+ crc = crc32c(~0, (u8 *)sb, EROFS_BLKSIZ - EROFS_SUPER_OFFSET);
+
+ /* set up checksum field to erofs_super_block */
+ sb->checksum = cpu_to_le32(crc);
+
+ ret = blk_write(buf, 0, 1);
+ if (ret) {
+ erofs_err("failed to write checksummed superblock: %s",
+ erofs_strerror(ret));
+ return ret;
+ }
+
+ erofs_info("superblock checksum 0x%08x written", crc);
+ return 0;
+}
+
int main(int argc, char **argv)
{
int err = 0;
@@ -255,6 +320,7 @@ int main(int argc, char **argv)
cfg.c_legacy_compress = false;
sbi.feature_incompat = EROFS_FEATURE_INCOMPAT_LZ4_0PADDING;
+ sbi.feature_compat = EROFS_FEATURE_COMPAT_SB_CHKSUM;
err = mkfs_parse_options_cfg(argc, argv);
if (err) {
@@ -337,6 +403,9 @@ int main(int argc, char **argv)
err = -EIO;
else
err = dev_resize(nblocks);
+
+ if (!err && (sbi.feature_compat & EROFS_FEATURE_COMPAT_SB_CHKSUM))
+ err = erofs_mkfs_superblock_csum_set();
exit:
z_erofs_compress_exit();
dev_close();
--
2.17.1
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