linux-kernel - Re: [PATCH v2 2/3] arm: boot: Use double quotes for image name

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Message-ID: <CAK7LNARzfMDBX9mhCaCV8QxpTic6A3JYOPBManJNh9Jas=-T9A@mail.gmail.com>
Date:   Tue, 7 Nov 2023 16:12:30 +0200
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Simon Glass <sjg@...omium.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        U-Boot Mailing List <u-boot@...ts.denx.de>,
        Tom Rini <trini@...sulko.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] arm: boot: Use double quotes for image name

Hi Simon,


On Tue, Nov 7, 2023 at 3:11 PM Simon Glass <sjg@...omium.org> wrote:
>
> Hi Masahiro,
>
> On Tue, 7 Nov 2023 at 03:13, Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > On Sat, Nov 4, 2023 at 9:42 PM Simon Glass <sjg@...omium.org> wrote:
> > >
> > > The use of single quotes in the image name causes them to appear in
> > > the image description when the uImage is created. Use double quotes, to
> > > avoid this.
> > >
> > > Signed-off-by: Simon Glass <sjg@...omium.org>
> > > ---
> > >
> > > Changes in v2:
> > > - Split double-quote change out into its own patch
> > >
> > >  scripts/Makefile.lib | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > > index 68d0134bdbf9..03e79e319293 100644
> > > --- a/scripts/Makefile.lib
> > > +++ b/scripts/Makefile.lib
> > > @@ -487,7 +487,7 @@ UIMAGE_OPTS-y ?=
> > >  UIMAGE_TYPE ?= kernel
> > >  UIMAGE_LOADADDR ?= arch_must_set_this
> > >  UIMAGE_ENTRYADDR ?= $(UIMAGE_LOADADDR)
> > > -UIMAGE_NAME ?= 'Linux-$(KERNELRELEASE)'
> > > +UIMAGE_NAME ?= "Linux-$(KERNELRELEASE)"
> > >
> > >  quiet_cmd_uimage = UIMAGE  $@
> > >        cmd_uimage = $(BASH) $(MKIMAGE) -A $(UIMAGE_ARCH) -O linux \
> > > --
> > > 2.42.0.869.gea05f2083d-goog
> > >
> >
> >
> > NACK.
> >
> >
> > This is because you are doing *WRONG* in 3/3.
> >
> > Look at your code closely.
> >
> > https://lore.kernel.org/linux-kbuild/20231104194207.3370542-4-sjg@chromium.org/T/#me2fb68151d6f4f330808406f9a711fffee149529
> >
> >
> >
> > In the mainline kernel, the quotation appears
> > only in the definition of UIMAGE_NAME.
> >
> >
> > masahiro@zoe:~/ref/linux(master)$ git grep UIMAGE_NAME
> > scripts/Makefile.lib:UIMAGE_NAME ?= 'Linux-$(KERNELRELEASE)'
> > scripts/Makefile.lib:                   -n $(UIMAGE_NAME) -d $< $@
> >
> >
> > The single quotes are consumed by shell.
> >
> >
> >
> >
> >
> >
> > This is mainline + your patch set.
> >
> > masahiro@zoe:~/ref/linux(simon-v2)$ git grep UIMAGE_NAME
> > scripts/Makefile.lib:UIMAGE_NAME ?= "Linux-$(KERNELRELEASE)"
> > scripts/Makefile.lib:                   -n "$(UIMAGE_NAME)" -d $< $@
> > scripts/Makefile.lib:                   --name "$(UIMAGE_NAME)" \
> >
> >
> > You quoted the definition of UIMAGE_NAME,
> > and also variable references.
> >
> >
> >
> >
> > See how it is expanded.
> >
> >
> > --name "$(UIMAGE_NAME)"
> >
> >
> >  ==>
> >
> >
> > --name ""Linux-$(KERNELRELEASE)""
> >
> >
> >  ==>
> >
> >
> > --name Linux-$(KERNELRELEASE)
> >
> >
> >
> >
> > You added double quotes in a row, just to cancel it.
>
> Yes, I understand that. But without the quotes in -n "$(UIMAGE_NAME)"
> then the name cannot contain spaces. So we do need some sort of
> quoting, right?


Yes.

If you move the quoting to the variable reference,
it is acceptable because there is a good reason to do so.



UIMAGE_NAME ?= Linux-$(KERNELRELEASE)


            ...
             -n '$(UIMAGE_NAME)' -d $< $@


This is the correct change.



>
> It just seems strange to use single quotes in a Makefile variable. I
> found it confusing.


Right. Why don't you remove it, then?


For clarification, there is no concept of quoting in GNU Make.

The single quote character ' and the double quote character " are
just normal characters for Make.

GNU Make handles them just like alphabets and numbers.

GNU Make just replaces $(UIMAGE_NAME)
with 'Linux-$(KERNELRELEASE)' verbatim.


It is the _shell_ that understands the quoting.

Just in case here is the spec for
"2.2.2 Single-Quotes" vs "2.2.3 Double-Quotes"

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html


Shell supports both single-quoting and double-quoting
for good reasons.

There is no good or bad because both of them are meaningful.






>
> I think you are saying you want to keep the single quotes in the var
> declaration and drop the quotes from the cmd_fit rule. I am OK with
> that, but I do think it is unusual not to quote something which might
> have spaces. It may cause confusion for others, as it did for me?
>
> Anyway, I'll send a new version with the quoting reverted.
>


Please move the single quotes as I suggested above.

The reason is because UIMAGE_NAME can be passed-in
by a user and it can contain whitespaces.





> Regards,
> Simon



-- 
Best Regards
Masahiro Yamada