Re: [Buildroot] [PATCH 05/13] support/scripts: fix and restrict conditions to accept merged dirs

["Yann E. MORIN" <yann.morin.1998@free.fr>]

All,

On 2025-05-14 18:58 +0200, Yann E. MORIN spake thusly:
> Currently, we accept that the merged usr is bqckward, i.e. that the
> /usr/bin, /usr/sbin, and /usr/lib entries be symlinks to, resp., /bin,
> /sbin, and /lib. We also allow either entries to be symlinks to other
> parts of the root. Both are accepted despite the comment at the top of
> the script explaining what should be accepted.
> 
> However, a properly merged usr is the other way around: /bin, /sbin, and
> /lib are the symlinks to resp. /usr/bin, /usr/sbin, and /usr/lib, and
> the latters are actual directories.
[--SNIP--]
> @@ -32,12 +29,21 @@ test_merged() {
>  	local dir2="${3}"
>  	local inode1 inode2
>  
> +	# OK if missing first entry and second entry is an actual directory
> +	test -e "${root}${dir1}" || { test -d "${root}${dir2}" && return; }
> +
>  	inode1="$(stat -c '%i' "${root}${dir1}/." 2>/dev/null)"
>  	inode2="$(stat -c '%i' "${root}${dir2}/." 2>/dev/null)"
>  
> -	test -z "${inode1}" || \
> -		test "${inode1}" = "${inode2}" || \
> -			printf '%s\n' "${dir1}"
> +	# OK if first entry is a symlink, second entry is a directoy, and
> +	# both have the same inode (once dereferenced)
> +	test -L "${root}${dir1}" \
> +	&& test -d "${root}${dir2}" \
> +	&& test "${inode1}" = "${inode2}" \
> +	&& return
> +
> +	# Otherwise, this directory is not merged
> +	printf '%s\n' "${dir1}"

This new test is still quite complex, and is in fact still wrong in
weird cases. For example, with BASE a custom skeleton or rootfs overlay,
if BASE/sbin and BASE/usr/sbin ar absolute symlinks to /usr/sbin, the
test above will accept BASE as being properly merged, while it is in
fact broken.

I'm preparing a v2 which greatly simplifies the test, and makes it cover
more (all, hopefully) cases.

Regards,
Yann E. MORIN.

>  }
>  
>  test_merged "${root}" "/lib" "/usr/lib"
> -- 
> 2.47.0
> 

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