linux-kernel - Re: [PATCH v2 8/8] tools/nolibc: x86

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Message-ID: <ZB011VbRSD9ojttc@1wt.eu>
Date:   Fri, 24 Mar 2023 06:32:05 +0100
From:   Willy Tarreau <w@....eu>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 8/8] tools/nolibc: x86_64: add stackprotector support

On Thu, Mar 23, 2023 at 11:44:15PM +0000, Thomas Weißschuh wrote:
> 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.

Perfect, will do it then. Thanks!
Willy