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[PATCH] MIPS support for --hash-style=gnu

Neil Schellenberger (neschell) neschell@cisco.com
Thu Nov 5 23:33:00 GMT 2015 
[I apologize in advance for my ignorance of most of the details of MIPS relocations....]

/If/ I understand correctly, there are three relocations involved for MIPS64:
R_MIPS_GOT_DISP, R_MIPS_GOT_PAGE, and R_MIPS_GOT_OFST.  My concern
is that if I shuffle things around in the GOT, wouldn't there be a danger that
(given a big enough move from its original spot in the GOT) a compiler generated
code sequence originally of one instruction and R_MIPS_GOT_DISP might now need
multiple instructions using R_MIPS_GOT_PAGE and R_MIPS_GOT_OFST?

> -----Original Message-----
> From: Rafael Espíndola [mailto:rafael.espindola@gmail.com]
> Sent: Thursday, November 05, 2015 1:46 PM
> To: Neil Schellenberger (neschell) <neschell@cisco.com>
> Cc: binutils@sourceware.org
> Subject: Re: [PATCH] MIPS support for --hash-style=gnu
> 
> Now in plain text:
> 
> I am not sure I follow. In each .o file the text sections have
> relocations to the got entries, not indexes, no?
> 
> Cheers, Rafael
> 
> On 5 November 2015 at 13:27, Neil Schellenberger (neschell)
> <neschell@cisco.com> wrote:
> > I did make a couple of abortive attempts to think of ways to do that,
> > but in the end I failed.  The chief difficulty seems to me (perhaps
> > entirely incorrectly) that any change in the order of the GOT entries
> > would require a related change to all references to them from the
> > .text and/or relocations.  (I was really trying to avoid fiddling with
> > that since I was already in over my head trying to grok BFD,
> > multi-got, mxgot, etc.... ) Is there some provably correct way to go
> > about back-patching the new GOT entry numbers into the .text?
> > (For obvious reasons, I /really/ want to avoid also needing any
> > changes in all possible upstream code generators e.g. gcc, gas,
> > clang etc.)
> >
> > I would be more than happy to hear that I am completely mistaken,
> > though!  I knew next to nothing about any of this before I started
> > and wouldn't pretend to claim to know much more about it now....
> >
> > Regards,
> > Neil
> >
> >> -----Original Message-----
> >> From: Rafael Espíndola [mailto:rafael.espindola@gmail.com]
> >> Sent: Thursday, November 05, 2015 12:14 PM
> >> To: Neil Schellenberger (neschell) <neschell@cisco.com>
> >> Cc: binutils@sourceware.org
> >> Subject: Re: [PATCH] MIPS support for --hash-style=gnu
> >>
> >> Wouldn't it be possible to sort the got entries so that the symbols
> >> end up in the same order as the gnu hash table?
> >>
> >> Cheers,
> >> Rafael
> >>
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