On Fri, 12 Oct 2018 at 12:01, Richard Earnshaw (lists) <
richard.earns...@arm.com> wrote:
> On 11/10/18 14:34, Christophe Lyon wrote:
> > In FDPIC mode, we set -fPIE unless the user provides -fno-PIE, -fpie,
> > -fPIC or -fpic: indeed FDPIC code is PIC, but we want to generate code
> > for executables rather than shared libraries by default.
> >
> > We also make sure to use the --fdpic assembler option, and select the
> > appropriate linker emulation.
> >
> > At link time, we also default to -pie, unless we are generating a
> > shared library or a relocatable file (-r). Note that even for static
> > link, we must specify the dynamic linker because the executable still
> > has to relocate itself at startup.
> >
> > We also force 'now' binding since lazy binding is not supported.
> >
> > We should also apply the same behavior for -Wl,-Ur as for -r, but I
> > couldn't find how to describe that in the specs fragment.
> >
> > 2018-XX-XX Christophe Lyon <christophe.l...@st.com>
> > Mickaël Guêné <mickael.gu...@st.com>
> >
> > gcc/
> > * config.gcc: Handle arm*-*-uclinuxfdpiceabi.
> > * config/arm/bpabi.h (TARGET_FDPIC_ASM_SPEC): New.
> > (SUBTARGET_EXTRA_ASM_SPEC): Use TARGET_FDPIC_ASM_SPEC.
> > * config/arm/linux-eabi.h (FDPIC_CC1_SPEC): New.
> > (CC1_SPEC): Use FDPIC_CC1_SPEC.
> > * config/arm/uclinuxfdpiceabi.h: New file.
> >
> > libsanitizer/
> > * configure.tgt (arm*-*-uclinuxfdpiceabi): Sanitizers are
> > unsupported in this configuration.
>
> The documentation (in patch 1) seems to imply that -mfdpic is available
> in all configurations and has certain effects (such as enabling -fPIE),
> but this patch set suggests that such behaviours are only available when
> the compiler is configured explicitly for an fdpic target.
>
> I think this needs to be resolved. Either -mfdpic works everywhere, or
> the option should only be available when configured for -mfdpic.
>
>
You are right, this is not clear. I tried to follow what other fdpic
targets do,
but it's not consistent either, it seems.
So, at present, -mfdpic alone is in general not sufficient, and the user has
to use -fpic/-fPIC/-fpie/-fPIE as needed. When configured for
arm-uclinuxfdpiceabi,
this is done implicitly (thanks to this patch).
One possibility is to rephrase the doc, and say that -fPIE is only implied
when GCC
is configured for arm-uclinuxfdpiceabi.
Do you mean to also make -mfdpic non-existent/rejected when GCC is not
configured
for arm-uclinuxfdpiceabi? How to achieve that?
R.
>
> >
> > Change-Id: If369e0a10bb916fd72e38f71498d3c640fa85c4c
> >
> > diff --git a/gcc/config.gcc b/gcc/config.gcc
> > index 793fc69..a4f4331 100644
> > --- a/gcc/config.gcc
> > +++ b/gcc/config.gcc
> > @@ -1144,6 +1144,11 @@ arm*-*-linux-* | arm*-*-uclinuxfdpiceabi)
> # ARM GNU/Linux with ELF
> > esac
> > tmake_file="${tmake_file} arm/t-arm arm/t-arm-elf arm/t-bpabi
> arm/t-linux-eabi"
> > tm_file="$tm_file arm/bpabi.h arm/linux-eabi.h arm/aout.h
> arm/arm.h"
> > + case $target in
> > + arm*-*-uclinuxfdpiceabi)
> > + tm_file="$tm_file arm/uclinuxfdpiceabi.h"
> > + ;;
> > + esac
> > # Generation of floating-point instructions requires at least
> ARMv5te.
> > if [ "$with_float" = "hard" -o "$with_float" = "softfp" ] ; then
> > target_cpu_cname="arm10e"
> > diff --git a/gcc/config/arm/bpabi.h b/gcc/config/arm/bpabi.h
> > index 1e3ecfb..5901154 100644
> > --- a/gcc/config/arm/bpabi.h
> > +++ b/gcc/config/arm/bpabi.h
> > @@ -55,6 +55,8 @@
> > #define TARGET_FIX_V4BX_SPEC " %{mcpu=arm8|mcpu=arm810|mcpu=strongarm*"\
> > "|march=armv4|mcpu=fa526|mcpu=fa626:--fix-v4bx}"
> >
> > +#define TARGET_FDPIC_ASM_SPEC ""
> > +
> > #define BE8_LINK_SPEC
> \
> > "%{!r:%{!mbe32:%:be8_linkopt(%{mlittle-endian:little}" \
> > " %{mbig-endian:big}" \
> > @@ -64,7 +66,7 @@
> > /* Tell the assembler to build BPABI binaries. */
> > #undef SUBTARGET_EXTRA_ASM_SPEC
> > #define SUBTARGET_EXTRA_ASM_SPEC \
> > - "%{mabi=apcs-gnu|mabi=atpcs:-meabi=gnu;:-meabi=5}"
> TARGET_FIX_V4BX_SPEC
> > + "%{mabi=apcs-gnu|mabi=atpcs:-meabi=gnu;:-meabi=5}"
> TARGET_FIX_V4BX_SPEC TARGET_FDPIC_ASM_SPEC
> >
> > #ifndef SUBTARGET_EXTRA_LINK_SPEC
> > #define SUBTARGET_EXTRA_LINK_SPEC ""
> > diff --git a/gcc/config/arm/linux-eabi.h b/gcc/config/arm/linux-eabi.h
> > index 8585fde..4cee958 100644
> > --- a/gcc/config/arm/linux-eabi.h
> > +++ b/gcc/config/arm/linux-eabi.h
> > @@ -98,11 +98,14 @@
> > #undef ASAN_CC1_SPEC
> > #define ASAN_CC1_SPEC "%{%:sanitize(address):-funwind-tables}"
> >
> > +#define FDPIC_CC1_SPEC ""
> > +
> > #undef CC1_SPEC
> > #define CC1_SPEC \
> > - LINUX_OR_ANDROID_CC (GNU_USER_TARGET_CC1_SPEC " " ASAN_CC1_SPEC, \
> > + LINUX_OR_ANDROID_CC (GNU_USER_TARGET_CC1_SPEC " " ASAN_CC1_SPEC " "
> \
> > + FDPIC_CC1_SPEC, \
> > GNU_USER_TARGET_CC1_SPEC " " ASAN_CC1_SPEC " " \
> > - ANDROID_CC1_SPEC)
> > + ANDROID_CC1_SPEC "" FDPIC_CC1_SPEC)
> >
> > #define CC1PLUS_SPEC \
> > LINUX_OR_ANDROID_CC ("", ANDROID_CC1PLUS_SPEC)
> > diff --git a/gcc/config/arm/uclinuxfdpiceabi.h
> b/gcc/config/arm/uclinuxfdpiceabi.h
> > new file mode 100644
> > index 0000000..43a17de
> > --- /dev/null
> > +++ b/gcc/config/arm/uclinuxfdpiceabi.h
> > @@ -0,0 +1,53 @@
> > +/* Configuration file for ARM GNU/Linux FDPIC EABI targets.
> > + Copyright (C) 2018 Free Software Foundation, Inc.
> > + Contributed by STMicroelectronics.
> > +
> > + This file is part of GCC.
> > +
> > + GCC is free software; you can redistribute it and/or modify it
> > + under the terms of the GNU General Public License as published
> > + by the Free Software Foundation; either version 3, or (at your
> > + option) any later version.
> > +
> > + GCC is distributed in the hope that it will be useful, but WITHOUT
> > + ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> > + or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
> > + License for more details.
> > +
> > + You should have received a copy of the GNU General Public License
> > + along with GCC; see the file COPYING3. If not see
> > + <http://www.gnu.org/licenses/>. */
> > +
> > +/* On uClibc EABI GNU/Linux, we want to force -mfdpic by default,
> > + which also means we produce PIE code by default. */
> > +#undef FDPIC_CC1_SPEC
> > +#define FDPIC_CC1_SPEC \
> > + "%{!mno-fdpic:-mfdpic %{!no-PIE:%{!fpie:%{!fPIC:%{!fpic: -fPIE}}}}}"
> > +
> > +/* Add --fdpic assembler flag by default. */
> > +#undef TARGET_FDPIC_ASM_SPEC
> > +#define TARGET_FDPIC_ASM_SPEC "%{!mno-fdpic: --fdpic}"
> > +
> > +/* TARGET_BIG_ENDIAN_DEFAULT is set in
> > + config.gcc for big endian configurations. */
> > +#if TARGET_BIG_ENDIAN_DEFAULT
> > +#define TARGET_FDPIC_LINKER_EMULATION "armelfb_linux_fdpiceabi"
> > +#else
> > +#define TARGET_FDPIC_LINKER_EMULATION "armelf_linux_fdpiceabi"
> > +#endif
> > +
> > +/* Unless we generate a shared library or a relocatable object, we
> > + force -pie. */
> > +/* Even with -static, we have to define the dynamic-linker, as we
> > + have some relocations to resolve at load time. */
> > +#undef SUBTARGET_EXTRA_LINK_SPEC
> > +#define SUBTARGET_EXTRA_LINK_SPEC \
> > + "%{!mno-fdpic: -m " TARGET_FDPIC_LINKER_EMULATION \
> > + "%{!shared:%{!r: -pie}} \
> > + %{static:-dynamic-linker " GNU_USER_DYNAMIC_LINKER "}}" \
> > + "%{mno-fdpic: -m " TARGET_LINKER_EMULATION "}" \
> > + "%{!r:%{!mno-fdpic: -z now}}"
> > +
> > +#undef STARTFILE_SPEC
> > +#define STARTFILE_SPEC "%{!mno-fdpic:%{!shared:crtreloc.o%s}} " \
> > + LINUX_OR_ANDROID_LD (GNU_USER_TARGET_STARTFILE_SPEC,
> ANDROID_STARTFILE_SPEC)
> > diff --git a/libsanitizer/configure.tgt b/libsanitizer/configure.tgt
> > index 1dce1e6..dff34cd 100644
> > --- a/libsanitizer/configure.tgt
> > +++ b/libsanitizer/configure.tgt
> > @@ -43,6 +43,9 @@ case "${target}" in
> > ;;
> > s390*-*-linux*)
> > ;;
> > + arm*-*-uclinuxfdpiceabi)
> > + UNSUPPORTED=1
> > + ;;
> > arm*-*-linux*)
> > ;;
> > mips*64*-*-linux*)
> >
>
>
