[U-Boot] [PATCH 2/2] arm: config: enforce -fno-pic for SPL and normal U-Boot

[Peng Fan]

Hi Tom,

> -----Original Message-----
> From: Tom Rini [mailto:trini at konsulko.com]
> Sent: Tuesday, July 04, 2017 12:17 AM
> To: Peng Fan <peng.fan at nxp.com>; Simon Glass <sjg at chromium.org>; Philipp
> Tomsich <philipp.tomsich at theobroma-systems.com>
> Cc: albert.u.boot at aribaud.net; u-boot at lists.denx.de
> Subject: Re: [U-Boot] [PATCH 2/2] arm: config: enforce -fno-pic for SPL and
> normal U-Boot
> 
> On Mon, Jul 03, 2017 at 09:14:08PM +0800, Peng Fan wrote:
> 
> > If not pass -fno-pic to toolchains, some toolchains may generate .got
> > and .got.plt sections, but when generate binaries, we did not take
> > .got and .got.plt into consideration, then SPL or normal U-Boot boot
> > failure because image corrupted.
> >
> > Need to pass -fno-pic to disable generating .got and .got.plt
> > sections.
> >
> > Signed-off-by: Peng Fan <peng.fan at nxp.com>
> > Cc: Albert Aribaud <albert.u.boot at aribaud.net>
> > Cc: Tom Rini <trini at konsulko.com>
> > ---
> >  arch/arm/config.mk | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/config.mk b/arch/arm/config.mk index
> > 1a77779..66ae403 100644
> > --- a/arch/arm/config.mk
> > +++ b/arch/arm/config.mk
> > @@ -130,9 +130,10 @@ ALL-y += checkarmreloc  # instruction. Relocation
> > is not supported for that case, so disable  # such usage by requiring
> > word relocations.
> >  PLATFORM_CPPFLAGS += $(call cc-option, -mword-relocations)
> > -PLATFORM_CPPFLAGS += $(call cc-option, -fno-pic)  endif
> >
> > +PLATFORM_CPPFLAGS += $(call cc-option, -fno-pic)
> > +
> >  # limit ourselves to the sections we want in the .bin.
> >  ifdef CONFIG_ARM64
> >  OBJCOPYFLAGS += -j .text -j .secure_text -j .secure_data -j .rodata
> > -j .data \
> 
> Something is "up" here and I need you to dig harder and perhaps see if we're
> missing something in the linker scripts?  The very next line of context here is:
>                 -j .u_boot_list -j .rela.dyn -j .got -j .got.plt
> 
> Meaning that we intentionally copy .got / .got.plt into the resulting binary.  And
> I see that we took in 397d7d5a1be1 from you back in 2016 saying that we
> needed this in SPL.  But 5a942a152776 put the got/got.plt sections (for 32bit
> ARM) in intentionally as some relocations do need it.  And in 4b0d506ed3b4
> Philipp seems to have seen the same problem you have, but fixed it with
> adding got/got.plt to the sections list we copy in (the above hunk of context).

If pass -fno-pic to compiler, there will be no .got and .got.plt sections.
The .got and .got.plt is usually used for dynamic link, such as linux "*.so" file.
We need to pass -fno-pic to compiler to remove .got and .got.plt sections.

Thanks,
Peng.

> 
> --
> Tom