[arch-projects] [mkinitcpio] [RFC] Rewrite parse_cmdline (again)

Rémy Oudompheng remyoudompheng at gmail.com
Thu Apr 14 18:13:29 EDT 2011

On Thu 14 April 2011 at 17:44 -0400, dave reisner wrote:
> On Apr 14, 2011 5:28 PM, "Thomas Bächler" <thomas at archlinux.org> wrote:
> > > I posted what I thought was a valid solution on FS#23467 from stack
> > > overflow that seems to be a lot more sane and _much_ more maintainable.
> > > For those who weren't following the report, I suggested that we use the
> > > same fallback as /etc/fstab, which says to encode spaces with octal
> > > sequences. These can then be decoded using printf's %b flag. It requires
> > > only a simple change to the current parse_cmdline function.
> >
> > I really don't understand what you mean (or how it would help). What you
> > mentioned doesn't solve the initial problem of finding out which spaces
> > separate arguments and which spaces are inside quoted strings.
> >
> It absolutely does because it eliminates spaces within variables, e.g.
> video=foo\040bar root=…
> The whole point is that quotes aren't used. fstab sets precedent here so its
> not some wild and whacky new thing being introduced.

This looks very nice, but how do we get a space-escaped kernel command
line? Is the user expected to encode his command line at boot time?

And do we really have to filter out invalid variable names? Isn't there
some documentation that says the kernel isn't supposed to have absurd
command line parameters (like unescaped >, <, &, |)

Because I think that (minus eval statements), the function would look
better like this :

local w lhs rhs
eval set -- $(cat test)
for w; do
    case "${w}" in
        \#*) break ;; # ignore everything after a # in the commandline
        # The kernel passes those to init on its own
        [0123456Ss]) ;;
        single) ;;
        rw) readwrite="yes" ;;
        ro) readwrite="no" ;;
        # variables don't begin with a digit
        [0-9]*) ;;
        # only export stuff that does work with ash :)
            # replace forbidden characters
            eval "${lhs}='${rhs}'"
            eval "${lhs}=y"


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