On Fri, Apr 30, 2021 at 04:45:46PM +1200, Campbell Suter wrote:
> In SquashFS, the contents of a directory is stored by
> squashfs_directory_entry structures which contain the file's name, inode
> and position within the filesystem.
>
> The inode number is not stored directly; instead each directory has one
> or more headers which set a base inode number, and files store the
> offset from that to the file's inode number.
>
> In mksquashfs, each inode is allocated a number in the same order as
> they are written to the directory table; thus the offset from the
> header's base inode number to the file's inode number is usually
> positive.
>
> Hardlinks are simply stored with two directory entries referencing the
> same file. This means the second entry will thus have an inode number
> much lower than the surrounding files. Since the header's base inode
> number comes from the first entry that uses the header, this delta will
> usually be negative.
>
> Previously, U-Boot's squashfs_directory_entry.inode_offset field was
> declared as an unsigned value. Thus when a negative value was found, it
> would either resolve to an invalid inode number or to that of an
> unrelated file.
>
> A squashfs image to test this can be created like so:
>
> echo hi > sqfs_test_files/001-root-file
> mkdir sqfs_test_files/002-subdir
> touch sqfs_test_files/002-subdir/003-file
> ln sqfs_test_files/{001-root-file,002-subdir/004-link}
> mksquashfs sqfs_test_files/ test.sqfs -noappend
>
> Note that squashfs sorts the files ASCIIbetacally, so we can use the
> names to control the order they appear in. The ordering is important -
> the first reference to the file must have a lower inode number than the
> directory in which the second reference resides, and the second
> reference cannot be the first file in the directory.
>
> Listing this sample image in U-Boot results in:
>
> => sqfsls virtio 2 002-subdir
> 0 003-file
> Inode not found.
> 0 004-link
>
> Signed-off-by: Campbell Suter <campbell@snapit.group>
> Reviewed-by: Miquel Raynal <miquel.ray...@bootlin.com>Applied to u-boot/master, thanks! -- Tom
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