Re: [Qemu-devel] [PATCH v2] Fix QEMU build on OpenBSD on x86 archs

[Brad Smith]

On 10/12/13 1:44 PM, Stefan Weil wrote:
> ... now with qemu-stable addressed - I had pressed "send" to early.
>
> Stefan
>
>
> Am 10.12.2013 19:42, schrieb Stefan Weil:
> > Am 10.12.2013 08:48, schrieb Brad Smith:
> > > On 10/12/13 2:07 AM, Stefan Weil wrote:
> > > > Am 10.12.2013 02:26, schrieb Brad Smith:
> > > > > This resolves the build issue with building the ROMs on OpenBSD on
> > > > > x86 archs.
> > > > > As of OpenBSD 5.3 the compiler builds PIE binaries by default and
> > > > > thus the
> > > > > whole OS/packages and so forth. The ROMs need to have PIE disabled.
> > > > > This
> > > > > is my initial attempt at trying to get somehting upstream so that QEMU
> > > > > both builds out of the box and to resolve the build issue with the
> > > > > buildbots that has been around for awhile. We have a patch in our ports
> > > > > tree but it is just the flags hardcoded into the Makefile which
> > > > > obviously
> > > > > is not appropriate for upstream.
> > > > >
> > > > >   From the OpenBSD buildbots..
> > > > >     Building optionrom/multiboot.img
> > > > > ld: multiboot.o: relocation R_X86_64_16 can not be used when making
> > > > > a shared object; recompile with -fPIC
> > > > >
> > > > >
> > > > > Signed-off by: Brad Smith <address@hidden>
> > > > > ---
> > > > >
> > > > > Changes in v2:
> > > > >       * Fix '==' is not portable syntax.
> > > > >
> > > > >
> > > > > diff --git a/configure b/configure
> > > > > index 508f6a5..6d84885 100755
> > > > > --- a/configure
> > > > > +++ b/configure
> > > > > @@ -1342,6 +1342,10 @@ EOF
> > > > >      if compile_prog "-fPIE -DPIE" "-pie"; then
> > > > >        QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
> > > > >        LDFLAGS="-pie $LDFLAGS"
> > > > > +    if test "$targetos" = OpenBSD; then
> > > > > +      CC_NOPIE="-fno-pie"
> > > > > +      LD_NOPIE="-nopie"
> > > > > +    fi
> > > > >        pie="yes"
> > > > >        if compile_prog "" "-Wl,-z,relro -Wl,-z,now" ; then
> > > > >          LDFLAGS="-Wl,-z,relro -Wl,-z,now $LDFLAGS"
> > > > > @@ -4307,6 +4311,8 @@ if test "$gcov" = "yes" ; then
> > > > >      echo "CONFIG_GCOV=y" >> $config_host_mak
> > > > >      echo "GCOV=$gcov_tool" >> $config_host_mak
> > > > >    fi
> > > > > +echo "CC_NOPIE=$CC_NOPIE" >> $config_host_mak
> > > > > +echo "LD_NOPIE=$LD_NOPIE" >> $config_host_mak
> > > > >
> > > > >    # use included Linux headers
> > > > >    if test "$linux" = "yes" ; then
> > > > > diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
> > > > > index 57d8bd0..0b35000 100644
> > > > > --- a/pc-bios/optionrom/Makefile
> > > > > +++ b/pc-bios/optionrom/Makefile
> > > > > @@ -12,6 +12,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/optionrom)
> > > > >    CFLAGS := -Wall -Wstrict-prototypes -Werror -fomit-frame-pointer
> > > > > -fno-builtin
> > > > >    CFLAGS += -I$(SRC_PATH)
> > > > >    CFLAGS += $(call cc-option, $(CFLAGS), -fno-stack-protector)
> > > > > +CFLAGS += $(CC_NOPIE)
> > > > Would it be possible to add -fno-pie unconditionally here ...
> > > >
> > > >
> > > > >    QEMU_CFLAGS = $(CFLAGS)
> > > > >
> > > > >    build-all: multiboot.bin linuxboot.bin kvmvapic.bin
> > > > > @@ -20,7 +21,7 @@ build-all: multiboot.bin linuxboot.bin kvmvapic.bin
> > > > >    .SECONDARY:
> > > > >
> > > > >    %.img: %.o
> > > > > -    $(call quiet-command,$(LD) -Ttext 0 -e _start -s -o $@ $<,"
> > > > > Building $(TARGET_DIR)$@")
> > > > > +    $(call quiet-command,$(LD) $(LD_NOPIE) -Ttext 0 -e _start -s -o
> > > > > $@ $<,"  Building $(TARGET_DIR)$@")
> > > >
> > > > ... and use -nopie here? I tried it in my Linux build environment, and
> > > > it seems to work.
> > > >
> > > > Then no changes to file configure are needed.
> > > The linker flag definitely does not exist everywhere so that would
> > > break the build on other OS/toolchain combinations; for example stock
> > > binutils does not have this flag. I would not have bothered going this
> > > route if I didn't see having the flags hard coded as causing a problem.
> >
> > Thank you for your explanation. I cc your patch to qemu-stable because
> > fixing QEMU 1.7 for OpenBSD might be a good idea, too.
> >
> > Reviewed-by: Stefan Weil <address@hidden>
> >
> >
> > If other hosts beside OpenBSD will need thismodification in the future,
> > I suggest modified code like this:
> >
> >      if compile_prog "-fPIE -DPIE" "-pie"; then
> >        QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
> >        LDFLAGS="-pie $LDFLAGS"
> >        # [...]
> >      fi
> >
> >      if compile_prog "-fno-pie" "-nopie"; then
> >        CFLAGS_NOPIE="-fno-pie"
> >        LDFLAGS_NOPIE="-nopie"
> >      fi
> >
> > (separate if blocks in configure and use CFLAGS_NOPIE, LDFLAGS_NOPIE
> > instead of CC_NOPIE, LD_NOPIE, this also needs a modified Makefile).

Well if you want to use CFLAGS_NOPIE and LDFLAGS_NOPIE now I can do so.
The variable names are not set in stone and I was just trying to come up
with an idea of how to do this and see how it goes through review.


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