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

[Brad Smith <brad@comstyle.com>]

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 <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).

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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