Hello Maintainers, After going through the recent mail thread between linux's filesystem folks on erofs channel, I felt erofs needs an interactive debug utility (like xfs_db) which can be used to examine erofs images & can also be used to inject errors OR fuzzing for testing purpose & dumping different erofs meta data structures for debugging. In order to demonstrate above I wrote an experimental patch that simply dumps the superblock of an image after mkfs completes.the full fletch utility will run independently and be able to seek / print / modify any byte of an erofs image, dump structures/lists/directory content of an image.
NOTE:This is an experimental patch just to demonstrate the purpose. The patch lacks a lot of things like coding standard, and new code runs in the context of mkfs itself.kindly ignore it. kindly provide your feedback on this. Signed-off-by: Pratik Shinde <[email protected]> --- include/erofs/io.h | 8 ++++++++ lib/io.c | 27 +++++++++++++++++++++++++++ mkfs/main.c | 36 ++++++++++++++++++++++++++++++++++++ 3 files changed, 71 insertions(+) diff --git a/include/erofs/io.h b/include/erofs/io.h index 4b574bd..e91d6ee 100644 --- a/include/erofs/io.h +++ b/include/erofs/io.h @@ -18,6 +18,7 @@ int dev_open(const char *devname); void dev_close(void); +int dev_read(void *buf, u64 offset, size_t len); int dev_write(const void *buf, u64 offset, size_t len); int dev_fillzero(u64 offset, size_t len, bool padding); int dev_fsync(void); @@ -30,5 +31,12 @@ 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 blkaddr, + u32 nblocks) +{ + return dev_read(buf, blknr_to_addr(blkaddr), + blknr_to_addr(nblocks)); +} + #endif diff --git a/lib/io.c b/lib/io.c index 15c5a35..87d7d6c 100644 --- a/lib/io.c +++ b/lib/io.c @@ -109,6 +109,33 @@ u64 dev_length(void) return erofs_devsz; } +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; +} + int dev_write(const void *buf, u64 offset, size_t len) { int ret; diff --git a/mkfs/main.c b/mkfs/main.c index f127fe1..109486e 100644 --- a/mkfs/main.c +++ b/mkfs/main.c @@ -182,6 +182,41 @@ int erofs_mkfs_update_super_block(struct erofs_buffer_head *bh, return 0; } +void erofs_dump_super(char *img_path) +{ + struct erofs_super_block *sb; + char buf[EROFS_BLKSIZ]; + unsigned int blksz; + int ret = 0; + + if (img_path == NULL) { + erofs_err("image path cannot be null"); + return; + } + ret = blk_read(buf, 0, 1); + if (ret) { + erofs_err("error reading super-block structure"); + return; + } + + sb = (struct erofs_super_block *)((u8 *)buf + EROFS_SUPER_OFFSET); + if (le32_to_cpu(sb->magic) != EROFS_SUPER_MAGIC_V1) { + erofs_err("not a erofs image"); + return; + } + + erofs_dump("magic: 0x%x\n", le32_to_cpu(sb->magic)); + blksz = 1 << sb->blkszbits; + erofs_dump("block size: %d\n", blksz); + erofs_dump("root inode: %d\n", le32_to_cpu(sb->root_nid)); + erofs_dump("inodes: %llu\n", le64_to_cpu(sb->inos)); + erofs_dump("build time: %u\n", le32_to_cpu(sb->build_time)); + erofs_dump("blocks: %u\n", le32_to_cpu(sb->blocks)); + erofs_dump("meta block: %u\n", le32_to_cpu(sb->meta_blkaddr)); + erofs_dump("xattr block: %u\n", le32_to_cpu(sb->xattr_blkaddr)); + erofs_dump("requirements: 0x%x\n", le32_to_cpu(sb->requirements)); +} + int main(int argc, char **argv) { int err = 0; @@ -268,6 +303,7 @@ int main(int argc, char **argv) err = -EIO; exit: z_erofs_compress_exit(); + erofs_dump_super("dummy"); dev_close(); erofs_exit_configure(); -- 2.9.3
