Re: c6x linker issue on linux-next-20160808 + some linker table work

[Mark Salter]

On Thu, 2016-08-11 at 17:59 +0200, Luis R. Rodriguez wrote:
> On Thu, Aug 11, 2016 at 07:32:42AM -0400, Mark Salter wrote:
> > 
> > On Thu, 2016-08-11 at 07:56 +0200, Luis R. Rodriguez wrote:
> > > 
> > > On Wed, Aug 10, 2016 at 07:04:09PM -0400, Mark Salter wrote:
> > > > 
> > > > 
> > > > On Wed, 2016-08-10 at 23:30 +0200, Luis R. Rodriguez wrote:
> > > > > 
> > > > > OK thanks I've found a clean solution minimal solution to this as follows. This now
> > > > > builds fine. Is this a fine work around for now ?
> > > > Almost. You also need:
> > > > 
> > > > diff --git a/include/linux/tables.h b/include/linux/tables.h
> > > > index a39ab03..3fa8d4d 100644
> > > > --- a/include/linux/tables.h
> > > > +++ b/include/linux/tables.h
> > > > @@ -325,7 +325,7 @@
> > > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ__attribute__((used,ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ\
> > > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂweak,ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ\
> > > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ__aligned__(LINUX_SECTION_ALIGNMENT(name)),\
> > > > -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂsection(SECTION_TBL(SECTION_RODATA,ÂÂÂÂÂÂÂÂ\
> > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂsection(SECTION_TBL(SECTION_TBL_RO,ÂÂÂÂÂÂÂÂ\
> > > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂname, level))))
> > > > Â
> > > > Â/**
> > > > 
> > > > Otherwise, start and end RO table markers end up in different sections.
> > > I thought that was not needed as weak attributes already force it to go to
> > > .const ? Anyway I've added this as well. Thanks!
> > The section attribute forced both variables into .rodata but the weak
> > attribute prevented accesses from using the SB-relative reloc. The
> > non-weak variable is the one that led to the link error.
> I ask as set_section_tbl_type() was not patched for instance, so firmware/Makefile
> still uses SECTION_RODATA, and it compiles and links fine. Should that also be
> using then SECTION_TBL_RO ? Or do we only need this for the C constructors ?
> 
> Â Luis

Yuck. You need SECTION_TBL_RO and s/.rodata/.const/ in that Makefile.
C6X doesn't support any of the devices with firmware, so I just added:

fw-shipped-y += ti_3410.fw

to firmware/Makefile for testing.

Leaving in .rodata and SECTION_RODATA, I got:

% readelf --syms vmlinux | grep -e _fw_ -e builtin_fwÂ
 8445: e01d4000ÂÂÂÂÂ0 NOTYPEÂÂLOCALÂÂDEFAULTÂÂÂÂ7 _fw_ti_3410_fw_bin
 8446: e01d75c5ÂÂÂÂÂ0 NOTYPEÂÂLOCALÂÂDEFAULTÂÂÂÂ7 _fw_end
 8447: e020a7ccÂÂÂÂÂ0 NOTYPEÂÂLOCALÂÂDEFAULTÂÂÂÂ7 _fw_ti_3410_fw_name
Â11063: e023d688ÂÂÂÂÂ0 OBJECTÂÂGLOBAL DEFAULTÂÂÂ13 builtin_fw__end
Â15867: e023d688ÂÂÂÂÂ0 OBJECTÂÂWEAKÂÂÂDEFAULTÂÂÂ13 builtin_fw

>From the above addresses, the _fw symbols are in .rodata and the builtin_fw symbols
are in .const.

Changing the Makefile to use .rodata and SECTION_TBL_RO, I see:

 8445: e0239688ÂÂÂÂÂ0 NOTYPEÂÂLOCALÂÂDEFAULTÂÂÂ13 _fw_ti_3410_fw_bin
 8446: e023cc4dÂÂÂÂÂ0 NOTYPEÂÂLOCALÂÂDEFAULTÂÂÂ13 _fw_end
 8447: e023cc50ÂÂÂÂÂ0 NOTYPEÂÂLOCALÂÂDEFAULTÂÂÂ13 _fw_ti_3410_fw_name
Â11063: e0239688ÂÂÂÂÂ0 OBJECTÂÂGLOBAL DEFAULTÂÂÂ13 builtin_fw__end
Â15867: e0239688ÂÂÂÂÂ0 OBJECTÂÂWEAKÂÂÂDEFAULTÂÂÂ13 builtin_fw

which has everything in .const as it should be. But still builtin_fw and
builtin_fw__end are at same address which seems wrong.