linux-kernel - Re: [PATCH] initramfs: fix 'bad variable name' error in gen_initramfs

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Date:   Wed, 1 Jan 2020 22:03:49 -0800
From:   Justin Capella <justincapella@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        "Jory A . Pratt" <anarchy@...too.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] initramfs: fix 'bad variable name' error in gen_initramfs_list.sh

Ah, I was wondering where the magic cmd_ prefix was coming from. But I
still think that there is an issue there-- initfs vs initRAMfs

On Tue, Dec 31, 2019 at 2:28 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Tue, Dec 31, 2019 at 12:13 AM Justin Capella <justincapella@...il.com> wrote:
> >
> > I was looking at this, and in theory there are other problems that
> > could arise from non-escaped characters, or things with leading
> > hyphens... In general it isn't great to assume ls output will play
> > nicely with the internal field separator / IFS. I think a better
> > solution would be to use something like ${foo@Q} and instead of trying
> > to scrape ls -l, maybe using stat, since it can be asked to print out
> > the device number.
>
> I am not sure if 'stat' is necessarily preferred over 'ls -l'.
>
> Commit a670b0b4aed129dc11b465c1c330bfe9202023e5
> says 'stat' is not standardized.
>
> There is some room for argument
> how far we should care about the portability, though.
>
>
> >
> > But I don't think this patch fixes the problem mentioned at all-- I
> > think the problem is initfs is not a variable name on line 61:
>
> cmd_initramfs is defined at line 46.
>
> Look into scripts/Kbuild.include
> if you want to know how if_changed works.
>
>
> > $(call if_changed,initfs)
> >
> > https://github.com/torvalds/linux/blob/351c8a09b00b5c51c8f58b016fffe51f87e2d820/usr/Makefile#L61
> >
> > The Makefile and script look like more patches would be needed to fix
> > mentioned issue, and I'm kind of wondering what the intent behind
> > lines 31-32 is...
> >
> > ramfs-input := $(if $(filter-out "",$(CONFIG_INITRAMFS_SOURCE)), \
> > $(shell echo $(CONFIG_INITRAMFS_SOURCE)),-d)
> >
> > why filter nothing, why shell echo?
>
> It does filter "", which is different from nothing.
>
> You need to notice GNU Make handles double-quote (")
> as a normal character.
> There is no special meaning as it has in shell.
>
> 'echo' is used just for ripping off the double-quotes.
>
>
> >
> > Quoting and/or proper escaping would be needed in many other places,
> > and I suspect cpio input is always regenerated...
>
> I do not think so.
>
> If the cpio input is regenerated,
> the following log is shown.
>
> GEN     usr/initramfs_data.cpio
>
>
> I do not see it every time.
>
>
> > The use of sed to
> > manually escape things and suggesting using \ instead of using the
> > argument terminator "--"... If weird paths with spaces and stuff are a
> > requirement for the script needs some overhauling
>
> If you find a problem in particular, a patch is welcome.
>
> But, what you stated above comes from your misunderstanding.
>
>
>
>
> > On Mon, Dec 30, 2019 at 5:21 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> > >
> > > Prior to commit 858805b336be ("kbuild: add $(BASH) to run scripts with
> > > bash-extension"), this shell script was almost always run by bash since
> > > bash is usually installed on the system by default.
> > >
> > > Now, this script is run by sh, which might be a symlink to dash. On such
> > > distros, the following code emits an error:
> > >
> > >   local dev=`LC_ALL=C ls -l "${location}"`
> > >
> > > You can reproduce the build error, for example by setting
> > > CONFIG_INITRAMFS_SOURCE="/dev".
> > >
> > >     GEN     usr/initramfs_data.cpio.gz
> > >   ./usr/gen_initramfs_list.sh: 131: local: 1: bad variable name
> > >   make[1]: *** [usr/Makefile:61: usr/initramfs_data.cpio.gz] Error 2
> > >
> > > This is because `LC_ALL=C ls -l "${location}"` contains spaces.
> > > Surrounding it with double-quotes fixes the error.
> > >
> > > Fixes: 858805b336be ("kbuild: add $(BASH) to run scripts with bash-extension")
> > > Reported-by: Jory A. Pratt <anarchy@...too.org>
> > > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > > ---
> > >
> > >  usr/gen_initramfs_list.sh | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/usr/gen_initramfs_list.sh b/usr/gen_initramfs_list.sh
> > > index 0aad760fcd8c..2bbac73e6477 100755
> > > --- a/usr/gen_initramfs_list.sh
> > > +++ b/usr/gen_initramfs_list.sh
> > > @@ -128,7 +128,7 @@ parse() {
> > >                         str="${ftype} ${name} ${location} ${str}"
> > >                         ;;
> > >                 "nod")
> > > -                       local dev=`LC_ALL=C ls -l "${location}"`
> > > +                       local dev="`LC_ALL=C ls -l "${location}"`"
> > >                         local maj=`field 5 ${dev}`
> > >                         local min=`field 6 ${dev}`
> > >                         maj=${maj%,}
> > > --
> > > 2.17.1
> > >
>
>
>
> --
> Best Regards
> Masahiro Yamada