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

[Brad Smith <brad@comstyle.com>]

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.

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