[PATCH] erofs-utils: erofs debug utility.
Pratik Shinde
pratikshinde320 at gmail.com
Thu Aug 22 04:15:48 AEST 2019
Thanks Gao,
Let me know when we can work on debug utility OR atleast list out things we
want to achieve through the utility.
Regarding the superblock checksum calculations, Yes I will dedicate
sometime this week for it. will start exploring it.
--Pratik.
On Wed, Aug 21, 2019 at 10:26 PM Gao Xiang <hsiangkao at aol.com> wrote:
> Hi Pratik,
>
> On Wed, Aug 21, 2019 at 10:08:08PM +0530, Pratik Shinde wrote:
> > 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.
>
> Yes, I think we really need that interactive tools, actually I'm stuggling
> in
> modifing Guifu's erofs-fuse now, we need to add the parsing ability to
> "lib/"
> first.
>
> I mean, first, I will add a "fuse" field to "cfg". If it is false, it will
> generate a image, or it will parse a image...
> And then we need to add parsing logic into "lib/" as well, and use
> "if (cfg.fuse)" to differnate whether it should read or write data.
>
> That is my prelimitary thought.. I will work on this framework in this
> weekend.
> and then we can work together on it. :)
>
> p.s. Pratik, if you have some time, could you take some extra time adding
> the
> super checksum calulation to EROFS? I mean we can add
> EROFS_FEATURE_SB_CHKSUM
> to the compat superblock field ("features"), and do crc32_le on kernel and
> mkfs...
> If you dont have time, I will do it later instead... (since we are using
> EROFS
> on the top of dm-verity, but completing the superblock chksum is also a
> good idea.)
>
> And then we can add block-based verification layer to EROFS, it can be seen
> as a hash tree like dm-verity or just simply CRC32 arrays for user to
> choise.
>
> Thanks,
> Gao Xiang
>
> >
> > 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 <pratikshinde320 at gmail.com>
> > ---
> > 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
> >
>
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