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Date:   Thu, 23 Mar 2023 23:44:15 +0000
From:   Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <linux@weissschuh.net>
To:     Willy Tarreau <w@1wt.eu>
Cc:     Shuah Khan <shuah@kernel.org>, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v2 8/8] tools/nolibc: x86_64: add stackprotector support
Message-ID: <fc50ed30-4152-4806-9eed-09a8b164afe6@t-8ch.de>
References: <20230223-nolibc-stackprotector-v2-0-4c938e098d67@weissschuh.net>
 <20230223-nolibc-stackprotector-v2-8-4c938e098d67@weissschuh.net>
 <ZBy0ZNYcHFlZWN32@1wt.eu>
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In-Reply-To: <ZBy0ZNYcHFlZWN32@1wt.eu>
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Hi Willy,

On Thu, Mar 23, 2023 at 09:19:48PM +0100, Willy Tarreau wrote:
> On Mon, Mar 20, 2023 at 03:41:08PM +0000, Thomas Weißschuh wrote:
> > Enable the new stackprotector support for x86_64.
> (...)
> > diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
> > index 8f069ebdd124..543555f4cbdc 100644
> > --- a/tools/testing/selftests/nolibc/Makefile
> > +++ b/tools/testing/selftests/nolibc/Makefile
> > @@ -80,6 +80,8 @@ CFLAGS_STACKPROTECTOR = -DNOLIBC_STACKPROTECTOR \
> >  			$(call cc-option,-mstack-protector-guard=global) \
> >  			$(call cc-option,-fstack-protector-all)
> >  CFLAGS_i386 = $(CFLAGS_STACKPROTECTOR)
> > +CFLAGS_x86_64 = $(CFLAGS_STACKPROTECTOR)
> > +CFLAGS_x86 = $(CFLAGS_STACKPROTECTOR)
> >  CFLAGS_s390 = -m64
> >  CFLAGS  ?= -Os -fno-ident -fno-asynchronous-unwind-tables \
> >  		$(call cc-option,-fno-stack-protector) \
> 
> This change is making it almost impossible for me to pass external CFLAGS
> without forcefully disabling the automatic detection of stackprot. I need
> to do it for some archs (e.g. "-march=armv5t -mthumb") or even to change
> optimization levels.
> 
> I figured that the simplest way to recover that functionality for me
> consists in using a dedicated variable to assign stack protector per
> supported architecure and concatenating it to the per-arch CFLAGS like
> this:
> 
>   diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
>   index 543555f4cbdc..bbce57420465 100644
>   --- a/tools/testing/selftests/nolibc/Makefile
>   +++ b/tools/testing/selftests/nolibc/Makefile
>   @@ -79,13 +79,13 @@ endif
>    CFLAGS_STACKPROTECTOR = -DNOLIBC_STACKPROTECTOR \
>                           $(call cc-option,-mstack-protector-guard=global) \
>                           $(call cc-option,-fstack-protector-all)
>   -CFLAGS_i386 = $(CFLAGS_STACKPROTECTOR)
>   -CFLAGS_x86_64 = $(CFLAGS_STACKPROTECTOR)
>   -CFLAGS_x86 = $(CFLAGS_STACKPROTECTOR)
>   +CFLAGS_STKP_i386 = $(CFLAGS_STACKPROTECTOR)
>   +CFLAGS_STKP_x86_64 = $(CFLAGS_STACKPROTECTOR)
>   +CFLAGS_STKP_x86 = $(CFLAGS_STACKPROTECTOR)
>    CFLAGS_s390 = -m64
>    CFLAGS  ?= -Os -fno-ident -fno-asynchronous-unwind-tables \
>                   $(call cc-option,-fno-stack-protector) \
>   -               $(CFLAGS_$(ARCH))
>   +               $(CFLAGS_STKP_$(ARCH)) $(CFLAGS_$(ARCH))
>    LDFLAGS := -s
>    
>    help:
> 
> And now with this it works again for me on all archs, with all of them
> showing "SKIPPED" for the -fstackprotector line except i386/x86_64 which
> show "OK".
> 
> Are you OK with this approach ? And if so, do you want to respin it or
> do you want me to retrofit it into your 3 patches that introduce this
> change (it's easy enough so I really don't care) ?

Looks good to me.

If nothing else needs to be changed feel free to fix it up on your side.

Thanks,
Thomas