[superh-gnu-discuss] SH2A uCLinux toolchain

[PHIL.EDWORTHY at renesas.com]

Hi Andrew,

> From: Andrew Stubbs <ams at codesourcery.com>
> To: PHIL.EDWORTHY at renesas.com
> Cc: "superh-gnu-discuss at codesourcery.com" <superh-gnu-discuss at codesourcery.com>
> Date: 16/05/2011 17:09
> Subject: Re: [superh-gnu-discuss] SH2A uCLinux toolchain
> Sent by: ams at codesourcery.com
>
> On 16/05/11 16:32, PHIL.EDWORTHY at renesas.com wrote:
> > The toolchain is only provided with fdpic libraries, but this is only
> > useful for userspace code afaik. The kernel already forces -mno-fdpic,
> > so should I use this option with U-Boot as well?
> >
> > The problem is that both the kernel, when building a zImage, and U-Boot,
> > link against libgcc. This leads to "attempt to mix FDPIC and non-FDPIC
> > objects" errors.
>
> The problem is that libgcc (a behind-the-scenes library containing
> essential helper functions for compiled code) is compiled for FDPIC.
> This is necessary for user-space, as you say.
>
> The kernel and u-boot are special cases in that they are bare-metal
> applications that are typically built with a (normally unsuitable)
> Linux/uClinux user-space toolchain. This means they should provide a
> complete set of libgcc-compatible replacement routines that work in a
> bare-metal context.
>
> The kernel does, in fact, provide sufficient routines to build a normal
> kernel, but apparently is missing (at least) one used by the compressed
> kernel. I'm not familiar with U-boot, but presumably it should be doing
> the same. You can probably copy many of the routines from the kernel
> sources. The rest can be obtained from the compiler sources, or by
> building a reconfigured compiler.
>
> Note that this problem is not SH-specific, but true on all platforms.
> That said, the FDPIC user-space *is* more incompatible with bare-metal
> than in most cases.
>
> > So my question is, how can I use this toolchain for uCLinux development?
>
> The toolchain can be used for user-space uClinux development, but the
> kernel and u-boot must either be built with a bare-metal toolchain, or
> else have patches applied to work with the Linux toolchain (as the
> kernel mostly does).
>
> Sorry, but the our Renesas contract does not specify any bare-metal
> configurations. If you think that should be changed, I believe you
> should talk to Paul Mundt or Hisao Munakata on your side. Paul might
> also have a technical solution for u-boot already.

Ok, that's a nice and clear summary, thanks. I'll talk to Paul about uboot.
Phil
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