[Qemu-devel] RFC: ARM prologue linkage fix

[Qemu-devel] RFC: ARM prologue linkage fix

[Blue Swirl]

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Hi,

I made a patch which allows sparc-linux-user target to be linked on an
ARM host. Is this OK? Sparc32 helloworld program runs successfully,
otherwise untested.

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Re: [Qemu-devel] RFC: ARM prologue linkage fix

[Paul Brook]

On Tuesday 08 July 2008, Blue Swirl wrote:
> Hi,
>
> I made a patch which allows sparc-linux-user target to be linked on an
> ARM host. Is this OK? Sparc32 helloworld program runs successfully,
> otherwise untested.

In principle it looks ok, however:

I think it deserves a comment in exec.c saying why we do this - the prologue 
is reached via a direct jump, so must be placed close to the code segment.

Also, calling something .bss.code_gen, than placing it is .data is just asking 
for trouble :-) I suggest calling the section ".gen_code".

We probably want the same thing on sparc and ppc hosts. I guess they can be 
added as required though.

Paul

Re: [Qemu-devel] RFC: ARM prologue linkage fix

[Blue Swirl]

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On 7/8/08, Paul Brook <paul@codesourcery.com> wrote:
> On Tuesday 08 July 2008, Blue Swirl wrote:
>  > Hi,
>  >
>  > I made a patch which allows sparc-linux-user target to be linked on an
>  > ARM host. Is this OK? Sparc32 helloworld program runs successfully,
>  > otherwise untested.
>
>
> In principle it looks ok, however:
>
>  I think it deserves a comment in exec.c saying why we do this - the prologue
>  is reached via a direct jump, so must be placed close to the code segment.
>
>  Also, calling something .bss.code_gen, than placing it is .data is just asking
>  for trouble :-) I suggest calling the section ".gen_code".

Is this version OK then? Should I commit it?

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Re: [Qemu-devel] RFC: ARM prologue linkage fix

[Paul Brook]

> >  > I made a patch which allows sparc-linux-user target to be linked on an
> >  > ARM host. Is this OK? Sparc32 helloworld program runs successfully,
> >  > otherwise untested.
>
> Is this version OK then? Should I commit it?

Your comment is somewhat ambiguous (all targets use a direct jump, ARM just 
has tighter restrictions on when that is possible). I suggest:

/* The prologue must be reachable with a direct jump. ARM has a limited
  branch range (possibly also PPC and SPARC?) so place it in a section
  close to code segment. */

Ok with that change.

Paul