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Subject: Re: [PATCH v7 0/5] LoongArch: Support toolchain with new relocation
 types
From:   Xi Ruoyao <xry111@xry111.site>
To:     Huacai Chen <chenhuacai@kernel.org>
Cc:     Jinyang He <hejinyang@loongson.cn>,
        WANG Xuerui <kernel@xen0n.name>, loongarch@lists.linux.dev,
        LKML <linux-kernel@vger.kernel.org>,
        Youling Tang <tangyouling@loongson.cn>
Date:   Tue, 06 Sep 2022 12:26:56 +0800
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On Tue, 2022-09-06 at 09:52 +0800, Huacai Chen wrote:
> > =C2=A0 cflags-$(CONFIG_LOONGARCH)=C2=A0=C2=A0=C2=A0=C2=A0 :=3D $(subst =
$(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 -fpic
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 -fpie
> >=20
> > =C2=A0 cflags-$(CONFIG_EFI_GENERIC_STUB) +=3D -I$(srctree)/scripts/dtc/=
libfdt
> >=20
> > (Some explanation: -fpic does not only mean "generate position-
> > independent code", but "generate position-independent code *suitable fo=
r
> > use in a shared library*".=C2=A0 On LoongArch -mdirect-extern-access ca=
nnot
> > work for a shared library so the "-fpic -mdirect-extern-access"
> > combination is rejected deliberately.)
> >=20
> > Not sure how to submit these changes properly...=C2=A0 Do you prefer me=
 to
> > send V8 of this series or a single patch on top of your tree on GitHub?

> Don't need V8, I will squash it into the previous patch myself. But
> can we keep efistub as is?

No, we can't allow -mdirect-extern-access -fpic on LoongArch because
without copy relocation such a combination just does not make sense (i.
e. we cannot find a sensible way to handle such a combination in GCC).=20
So such a combination will cause GCC refuse to run.

Note that -fpic/-fPIC is "position-independent code *suitable for
use in a shared library*", while -fpie/-fPIE is more like just
"position-independent code".  The names of those options are confusing.
(When -fpic was invented first time, people mostly believed "PIC had
been only for shared libraries", so it's named -fpic instead of -shlib
or something.)  IMO in the EFI stub for other ports, -fpie should be
used instead of -fpic as well because the EFI stub is not similar to a
shared library in any means.

--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University