Re: [PATCH v2] [Gold,MIPS] Detect 64-bit MIPS targets

["Maciej W. Rozycki" <macro at imgtec dot com>]

Hi Aurelien,

> > gold/Changelog:
> > 	* configure.tgt: Add mips*64*el*-*-*|mips*64*le*-*-* and mips*64*-*-*.

 Hmm, `mips*64*le*-*-*' is not a standard machine triplet, e.g.:

$ ./config.sub mips64le-linux
Invalid configuration `mips64le-linux': machine `mips64le' not recognized
$ 

so please drop it.  The little endianness for MIPS machines has been 
selected solely with the `el' suffix, e.g.:

$ ./config.sub mips64el-linux
mips64el-unknown-linux-gnu
$ 

> > diff --git a/gold/configure.tgt b/gold/configure.tgt
> > index f1fd132..e119df0 100644
> > --- a/gold/configure.tgt
> > +++ b/gold/configure.tgt
> > @@ -153,6 +153,13 @@ aarch64*-*)
> >   targ_big_endian=false
> >   targ_extra_big_endian=true
> >   ;;
> > +mips*64*el*-*-*|mips*64*le*-*-*)
> > + targ_obj=mips
> > + targ_machine=EM_MIPS_RS3_LE
> > + targ_size=64
> > + targ_big_endian=false
> > + targ_extra_big_endian=true
> > + ;;
> >  mips*el*-*-*|mips*le*-*-*)
> >   targ_obj=mips
> >   targ_machine=EM_MIPS_RS3_LE
> > @@ -160,6 +167,13 @@ mips*el*-*-*|mips*le*-*-*)
> >   targ_big_endian=false
> >   targ_extra_big_endian=true
> >   ;;
> > +mips*64*-*-*)
> > + targ_obj=mips
> > + targ_machine=EM_MIPS
> > + targ_size=64
> > + targ_big_endian=true
> > + targ_extra_big_endian=false
> > + ;;
> >  mips*-*-*)
> >   targ_obj=mips
> >   targ_machine=EM_MIPS

 The change LGTM otherwise, although I cannot approve it as I have no 
authority for GOLD.

 While at it it looks strange if not wrong to me that EM_MIPS_RS3_LE is 
used by GOLD for the little-endian target given that no other tool uses 
that ELF machine type -- it's been reserved around the time the original 
SVR4 MIPS psABI has been created, but AFAIK never actually used as EI_DATA 
already provides endianness information, so an extra machine type is 
redundant.

 There's a further confusion around this machine type as the original SVR4 
ELF gABI defines:

EM_MIPS          8  MIPS RS3000 Big-Endian
EM_MIPS_RS4_BE  10  MIPS RS4000 Big-Endian

(RS3000/RS4000, sic!) the original SVR4 MIPS psABI has this:

"Processor identification resides in the ELF header e_machine member and 
must have the value 8, defined as the name EM_MIPS."

and we have:

#define EM_MIPS		  8	/* MIPS R3000 (officially, big-endian only) */
#define EM_MIPS_RS3_LE	 10	/* MIPS R3000 little-endian (Oct 4 1999 Draft) Deprecated */

 Do binaries with EM_MIPS_RS3_LE marking actually work at all, e.g. does 
the Linux kernel and `ld.so', or firmware loaders (CFE, etc.) accept them?

  Maciej