From mboxrd@z Thu Jan  1 00:00:00 1970
From: Laurent Vivier <lvivier@redhat.com>
Date: Mon, 29 Feb 2016 17:53:13 +0000
Subject: Re: [kvm-unit-tests PATCH v2 2/2] powerpc: select endianness
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To: Andrew Jones <drjones@redhat.com>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, thuth@redhat.com, dgibson@redhat.com, agraf@suse.de, pbonzini@redhat.com

On 26/02/2016 19:45, Andrew Jones wrote:
...
>> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
>> > index cc27ac8..b088af6 100644
>> > --- a/powerpc/Makefile.common
>> > +++ b/powerpc/Makefile.common
>> > @@ -11,14 +11,15 @@ all: $(TEST_DIR)/boot_rom.bin test_cases
>> >  
>> >  ##################################################################
>> >  
>> > -CFLAGS += $(arch_CFLAGS)
>> > -CFLAGS += -std=gnu99
>> > -CFLAGS += -ffreestanding
>> > -CFLAGS += -Wextra
>> > -CFLAGS += -O2
>> > -CFLAGS += -I lib -I lib/libfdt
>> > -CFLAGS += -Wa,-mregnames
>> > -CFLAGS += -fpie
>> > +common_CFLAGS = -std=gnu99
>> > +common_CFLAGS += -ffreestanding
>> > +common_CFLAGS += -Wextra
>> > +common_CFLAGS += -O2
>> > +common_CFLAGS += -I lib -I lib/libfdt
>> > +common_CFLAGS += -Wa,-mregnames
>> > +common_CFLAGS += -fpie
>> > +
>> > +CFLAGS += $(arch_CFLAGS) $(common_CFLAGS)
> I'm not sure what we gain by renaming to common_CFLAGS. Doesn't just
> 
> %.elf: CFLAGS += $(arch_CFLAGS)
> 
> work?
> 
>> >  
>> >  asm-offsets = lib/$(ARCH)/asm-offsets.h
>> >  include scripts/asm-offsets.mak
>> > @@ -48,6 +49,7 @@ $(TEST_DIR)/boot_rom.bin: $(TEST_DIR)/boot_rom.elf
>> >  	dd if=/dev/zero of=$@ bs%6 count=1
>> >  	$(OBJCOPY) -O binary $^ >(cat - >>$@)
>> >  
>> > +$(TEST_DIR)/boot_rom.elf: CFLAGS = -mbig-endian $(common_CFLAGS) $(main_CFLAGS)
> And just
> $(TEST_DIR)/boot_rom.elf: CFLAGS += -mbig-endian
> 

We can't do that because boot_rom.elf is also a .elf, so the both rules
apply and we end up with in the case of boot_rom.elf (and --endian=little):

  CFLAGS += -mlittle-endian -mbig-endian

and it doesn't work. We must overwrite CFLAGS in the case of boot_rom.elf.

But boot_rom.S is a one line of assembly language, we don't need the
other flags, in fact...

Laurent