From: Rich Felker <dalias@libc.org>
To: linux-sh@vger.kernel.org
Subject: Re: SH FDPIC ABI spec/binutils and kernel conflict on flag definitions
Date: Mon, 14 Sep 2015 16:09:56 +0000 [thread overview]
Message-ID: <20150914160956.GA1820@brightrain.aerifal.cx> (raw)
In-Reply-To: <20150910033400.GM17773@brightrain.aerifal.cx>
On Thu, Sep 10, 2015 at 04:53:35PM +0100, David Howells wrote:
> Rich Felker <dalias@libc.org> wrote:
>
> > On the other hand, the only existing way to produce a binary that both
> > (1) needs constant displacement, and (2) actually gets constant
> > displacement from the kernel at load time, is to manually edit the ELF
> > headers to flip the bit. So I really doubt any such binaries exist. Do
> > you have a reason to believe they do?
>
> Well, Fujitsu asked for it for FRV - I've no idea whether they have such
> binaries still.
OK, I've solved part of the mystery: on FRV and Blackfin, binutils
matches the kernel behavior and conflicts with the (effectively wrong)
ABI documents. As can be seen at the following locations in the
source, EF_$ARCH_PIC is cleared by default and set when there is a
cross-segment relocation that forces constant displacement:
Blackfin:
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f¿d/elf32-bfin.c;h\x152134ee7b9b445d96818fcab2350ffd11795897;hb=HEAD#l3140
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f¿d/elf32-bfin.c;h\x152134ee7b9b445d96818fcab2350ffd11795897;hb=HEAD#l4978
FRV:
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f¿d/elf32-frv.c;hú12528b3d11ab9ed7a4d5d894f8b9c1a5e783a9;hb=HEAD#l3919
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f¿d/elf32-frv.c;hú12528b3d11ab9ed7a4d5d894f8b9c1a5e783a9;hb=HEAD#l6367
And SH does the opposite:
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f¿d/elf32-sh.c;h{8d7636de5fe4ce169eacbeb876ab7d741df798;hb=HEAD#l5499
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f¿d/elf32-sh.c;h{8d7636de5fe4ce169eacbeb876ab7d741df798;hb=HEAD#l6656
So I think for consistency with other FDPIC targets, and to avoid
changing kernel ABI, binutils should just be fixed to match the
Blackfin and FRV interpretation of EF_$ARCH_PIC on SH as well.
Ideally fixed versions of the ABI documents should also be produced.
Rich
next prev parent reply other threads:[~2015-09-14 16:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-10 3:34 SH FDPIC ABI spec/binutils and kernel conflict on flag definitions Rich Felker
2015-09-10 11:57 ` Nick Clifton
2015-09-10 14:58 ` Rich Felker
2015-09-10 15:45 ` David Howells
2015-09-10 15:50 ` Rich Felker
2015-09-10 15:53 ` David Howells
2015-09-10 16:01 ` Rich Felker
2015-09-10 21:09 ` Rich Felker
2015-09-14 16:09 ` Rich Felker [this message]
2015-12-30 3:55 ` Mike Frysinger
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