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Date: Wed, 30 Nov 2016 00:17:58 +0100
From: =?UTF-8?Q?Przemys=C5=82aw_Pawe=C5=82czyk?= <przemoc@zoho.com>
To: "Shiz" <hi@shiz.me>
Cc: "" <alpine-devel@lists.alpinelinux.org>, 
	"Natanael Copa" <ncopa@alpinelinux.org>
Message-ID: <158b2616a36.b03a19706367.3199754036165045115@zoho.com>
In-Reply-To: <20161117015252.27549-2-hi@shiz.me>
References: <20161117015252.27549-1-hi@shiz.me> <20161117015252.27549-2-hi@shiz.me>
Subject: Re: [alpine-devel] [PATCH 2/3] init: fix quoting issue for kernel
 arguments
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 ---- On Thu, 17 Nov 2016 02:52:51 +0100 Shiz <hi@shiz.me> wrote ---- 
 > The kernel passes arguments from /proc/cmdline as a single string like 
 > foo=bar baz="something with spaces". In the latter case, with the added 
 > single quotes the actual value of ${KOPT_baz} would contain these quotes 
 > as well, which is not the intention. 

Description is a bit wrong.  Kernel provides arguments used during boot
via /proc/cmdline as a single text line.

The problem is that

    set -- $(cat /proc/cmdline)

doesn't do what you think it does (or at least what your patch assumes).
There is even a comment earlier:

    # read the kernel options. we need surve things like:
    #  acpi_osi="!Windows 2006" xen-pciback.hide=(01:00.0)

to hint that it's not an easy matter.
If you'd perform in POSIX sh:

    ./script acpi_osi="!Windows 2006" xen-pciback.hide='(01:00.0)'

Then $1 would be equal to 'acpi_osi=!Windows 2006'
and $2 would be queal to 'xen-pciback.hide=(01:00.0)'
(single-quoting around value of xen-pciback.hide in ./script call was
necessary to avoid interpreting of parenthesis and raising error).
Both without the single-quotes, of course.
(Actually in bash you'd have to change double-quoting in first argument
to single-quoting too, because otherwise ! is interpreted and you get
error.)

But if you do:

    echo 'acpi_osi="!Windows 2006" xen-pciback.hide=(01:00.0)' >cmdline
    ./script $(cat cmdline)

then:

$1 = 'acpi_osi="!Windows'
$2 = '2006"'
$3 = 'xen-pciback.hide=(01:00.0)'
All without the single-quotes, of course.

so it's not what we want.
We don't have information about real argument boundaries.

What we need is to reassemble arguments. Something akin to recreating
"$@" from $*.  It's quite hard to do in POSIX sh. I spend some time
yesterday and I came up with:
https://gist.github.com/przemoc/168ecd5a263e1e498ee6d2ee4278e4ae

It's not perfect, it's not a beauty, but I think it's very good
approximation of what we need and it works (it handles many cases, but
obviously not all of them - doing it in shell is more than cumbersome).
The code (w/o show current arguments part) should be put after
set -- $(cat /proc/cmdline), and then your patch should be reverted
(i.e. single-quoting in eval KOPT_${i} assignment should be restored).

I hoped to provide such patch, but it's already so late, that I won't do
it today and I am merely informing about the problem.
I'm also starting to doubt that ncopa will happily include additional
150 lines in initramfs-init.in, even if they work, so it may be better
to get some kind of half-ACK at least before preparing the patch.

Regards,
Przemek

 > --- 
 >  initramfs-init.in | 2 +- 
 >  1 file changed, 1 insertion(+), 1 deletion(-) 
 >  
 > diff --git a/initramfs-init.in b/initramfs-init.in 
 > index 78bcbe4..9aa1d3f 100755 
 > --- a/initramfs-init.in 
 > +++ b/initramfs-init.in 
 > @@ -279,7 +279,7 @@ for opt; do 
 >   
 >      for i in $myopts; do 
 >          case "$opt" in 
 > -        $i=*)    eval "KOPT_${i}='${opt#*=}'";; 
 > +        $i=*)    eval "KOPT_${i}=${opt#*=}";; 
 >          $i)    eval "KOPT_${i}=yes";; 
 >          no$i)    eval "KOPT_${i}=no";; 
 >          esac 
 > --  
 > 2.10.0 





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