[U-Boot] [PATCH] ARMv7: Fix linker errors across toolchain versions

[Premi, Sanjeev]

> -----Original Message-----
> From: Albert ARIBAUD [mailto:albert.aribaud at free.fr] 
> Sent: Thursday, December 02, 2010 12:30 PM
> To: u-boot at lists.denx.de
> Cc: Premi, Sanjeev; Wolfgang Denk
> Subject: Re: [U-Boot] [PATCH] ARMv7: Fix linker errors across 
> toolchain versions
> 
> Le 01/12/2010 22:39, Albert ARIBAUD a écrit :
> > This one is a conundrum.
> >
> > Using 2010q1, building omap3_evm causes a linker warning
> > "arm-none-linux-gnueabi-ld: u-boot: section .bss vma 
> 0x8003e8f0 overlaps
> > previous sections" while building omap3_beagle does not 
> cause any linker
> > warning.
> >
> > Both boards use the same armv7 u-boot.lds and have a .bss 
> which is way
> > bigger than the .rel.dyn plus .dynsym sections that it does overlay.
> > IOW, they have a similar layout for .rel.dyn, .dynsym and 
> .bss, but one
> > gets the warning and one does not.
> >
> > The one difference a readelf shows is that for beagle, 
> there is only one
> > segment:
> >
> > 00  .text .rodata .hash .data .got.plt .u_boot_cmd .rel.dyn .dynsym
> >
> > While for evm there is
> >
> > 00  .text .rodata .hash .data .got.plt .u_boot_cmd .rel.dyn .bss
> > 01  .dynsym
> >
> > Note that .bss has appeared in segment 00 for evm, whereas 
> it was absent
> > for beagle, and that .dynsym was rejected to a second 
> segment -- why? I
> > don't know.
> >
> > Note: I've tried with putting input sections .rel.dyn and 
> .dynsym into a
> > single output section .rel.dyn: this makes the second 
> segment disappear,
> > but for evm the warning remains and .bss remains in the segment.
> 
> I have a tiny clue.
> 
> Starting with the fact that the linker issue is only for one board, 
> omap3_evm, I looked up the board-specific code. First thing that I 
> noticed was
> 
> 	static u8 omap3_evm_version;
> 
> I changed this to
> 
> 	static u8 omap3_evm_version = 1;
> 
> so that the static was moved out of BSS and the linker warning 
> disappeared (reminder: v2010.12-rc2, omap3_evm, arm-2010q1).
> 
> Now this is not the first static BSS variable we use in 
> U-Boot, and the 
> others did not cause linker warnings (not *all* the others, 
> at least), 
> so the real cause is yet unknown to me. But that's at least a lead we 
> can follow.
> 
> If this BSS variable is used before relocation (I haven't 
> checked this), 
> then anyway it'll have to move; in that case I'll keep an eye on this 
> linker warning and try to sort it out if I get time.

I did explain yesterday that variable is not used in relocation. If you
notice the code snippet I sent yesterday, I had removed every assignment
to the variable. And 2009q1 was still not happy!
> 
> Amicalement,
> -- 
> Albert.
>