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Date: Wed, 27 Jan 2016 12:17:27 -0500
From: Kevin O'Connor <kevin@koconnor.net>
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Subject: Re: [Qemu-devel] [PATCH v3] Add optionrom compatible with fw_cfg
	DMA version
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To: Marc =?iso-8859-1?Q?Mar=ED?= <markmb@redhat.com>
Cc: "Gabriel L. Somlo" <somlo@cmu.edu>, qemu-devel@nongnu.org, Gerd Hoffmann <kraxel@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Laszlo <lersek@redhat.com>

On Wed, Jan 27, 2016 at 05:57:28PM +0100, Marc Marí wrote:
> On Wed, 27 Jan 2016 16:43:29 +0000
> Stefan Hajnoczi <stefanha@redhat.com> wrote:
> 
> > On Tue, Jan 26, 2016 at 12:26:12PM +0100, Gerd Hoffmann wrote:
> > > On Di, 2016-01-26 at 12:20 +0100, Marc Marí wrote:  
> > > > On Tue, 26 Jan 2016 11:11:54 +0000
> > > > Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > > >   
> > > > > On Mon, Jan 25, 2016 at 02:17:48PM +0100, Marc Marí wrote:  
> > > > > > +linuxboot_dma.img: linuxboot_dma.o
> > > > > > +	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -m
> > > > > > elf_i386 -Ttext 0 -e _start -s -o $@ $<,"  Building
> > > > > > $(TARGET_DIR)$@") + %.img: %.o
> > > > > >  	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -Ttext 0
> > > > > > -e _start -s -o $@ $<,"  Building $(TARGET_DIR)$@")    
> > > > > 
> > > > > Why is -m elf_i386 necessary for linuxboot_dma.img but not for
> > > > > the other *.img files?  
> > > > 
> > > > I cannot give a precise explanation. But if I don't force an
> > > > output type, I get this error:
> > > > 
> > > > Building optionrom/linuxboot_dma.img
> > > > ld: i386 architecture of input file `linuxboot_dma.o' is
> > > > incompatible with i386:x86-64 output  
> > > 
> > > Any chance the linker needs -m32 too?  
> > 
> > I wonder why this isn't a problem for the existing firmware code.  Are
> > we really building x86_64 ELF files for our firmware?
> 
> Yes they are x86_64:
> 
> pc-bios/optionrom/linuxboot.img: ELF 64-bit LSB executable, x86-64,
> version 1 (SYSV), statically linked, stripped
> 
> But as they are written directly in assembly, it does not give any
> problem. Whereas when mixing C and ASM, it does give problems.

Would it hurt anything to add "-m elf_i386" to the generic assembler
rule and then use that for both targets?  (Just to keep the makefile a
little simpler.)

-Kevin