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

[Stefan Weil <sw@weilnetz.de>]

... 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 <brad@comstyle.com>
>>>> ---
>>>>
>>>> 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 <sw@weilnetz.de>
>
>
> 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).
>
> Regards,
> Stefan
>