linux-kernel - Re: [PATCH] ppc: add "-z notext" flag to disable diagnostic

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Date:   Sat, 14 Aug 2021 21:59:40 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Bill Wendling <morbo@...gle.com>, Daniel Axtens <dja@...ens.net>,
        Fangrui Song <maskray@...gle.com>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linuxppc-dev@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] ppc: add "-z notext" flag to disable diagnostic

Bill Wendling <morbo@...gle.com> writes:
> On Fri, Aug 13, 2021 at 7:13 AM Daniel Axtens <dja@...ens.net> wrote:
>> Bill Wendling <morbo@...gle.com> writes:
...
>> > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
>> > index 6505d66f1193..17a9fbf9b789 100644
>> > --- a/arch/powerpc/Makefile
>> > +++ b/arch/powerpc/Makefile
>> > @@ -122,6 +122,7 @@ endif
>> >
>> >  LDFLAGS_vmlinux-y := -Bstatic
>> >  LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
>> > +LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) += -z notext
...
>
> Unrelated question: Should the "-pie" flag be added with "+= -pie"
> (note the plus sign)?

I noticed that too.

It's been like that since the original relocatable support was added in
2008, commit 549e8152de80 ("powerpc: Make the 64-bit kernel as a
position-independent executable"), which did:

-LDFLAGS_vmlinux	:= -Bstatic
+LDFLAGS_vmlinux-yy := -Bstatic
+LDFLAGS_vmlinux-$(CONFIG_PPC64)$(CONFIG_RELOCATABLE) := -pie
+LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-yy)


There's no mention of those flags in the change log. But the way it's
written suggests the intention was to not pass -Bstatic for relocatable
builds, otherwise it could have been more simply:

+LDFLAGS_vmlinux-$(CONFIG_PPC64)$(CONFIG_RELOCATABLE) := -pie
+LDFLAGS_vmlinux	:= -Bstatic $(LDFLAGS_vmlinux-yy)


So I think it was deliberate to not use +=, but whether that's actually
correct I can't say. Maybe in the past -Bstatic and -pie were
incompatible?

cheers