[syslinux] Nested SYSLINUX configurations -- error using CONFIG directive

[Gene Cumm]

On Wed, Mar 30, 2011 at 10:35, Rich Mahn <rich at lat.com> wrote:
> Rich Mahn <rich at lat.com> wrote:
>
>> > From: "Rich Mahn" <rich at lat.com>
>> >
>> > > H. Peter Anvin <hpa at zytor.com> wrote:
>> > > >> There seems to be an error using '..' in the append portion of the
>> > > >> CONFIG directive.
>> > > >
>> > > > This is a known bug in Syslinux 4.03.  It should be fixed in 4.04-pre14,
>> > > > but if it is not, please scream.
>> > > >
>> > > > -hpa
>> > > >
>>
>> Ok.  I have successfully recompile 4.04-pre14.  The problem still exists.  Here's
>> another example:
>> in root:
>> LABEL dir1
>>    config dir1/config.cfg
>>    append dir1
>> LABEL non-existant dir2
>>    config dir2/config.cfg
>>    append dir2
>>
>> in dir1
>> LABEL up
>>    config ../config.cfg
>>    append ..
>>
>> directory structure:  /dir1/dir2 with no /dir2
>>
>> startup syslinux in the root directory.
>> select dir1, menu in dir1 comes up.
>> selet up, menu in root comes up.
>>
>> then select dir2.  menu in /dir1/dir2 comes up
>>
>> somehow the "current working directory" doesn't seem to get
>> changed with ".." or any variant thereof.  But the config
>> file and the other items, such as kernel, initrd, etc come
>> from the correct directory
>
> I was mistaken about the kernel, initrd, etc.  They are not coming from
> the correct directory, but instead they are coming from the directory
> where the CONFIG directive was given.  This simplifies the
> characterization of the error considerably:
>
> The processing of the change to the current directory terminates upon a
> ".." as a component of the path.  For example, if the append portion of
> the CONFIG directive is "A/B/../C/."  it will be processed as if it was
> "A/B".

Since you've already grabbed 4.04-pre14, take a look at
doc/syslinux.txt, lines 231-238.  I extended and partially rewrote
that section based on what I understood as the behavior.  If it's not
clear or you notice behavior contrary to that section, let us know.

Also, there's com32/modules/pwd.c32 which will show you the current
working directory as Syslinux has stored it, com32/modules/ls.c32
which accepts up to 1 parameter (a directory) to produce a directory
listing and com32/rosh/rosh.c32, a read-only shell (still a work in
progress but reasonably usable).

-- 
-Gene