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Date: Thu, 13 Jan 2011 01:28:05 +0200
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From: Pavel Zholkover <paulzhol@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] plan9 go output faults on 9vx but ok on cpu
Topicbox-Message-UUID: 953dc038-ead6-11e9-9d60-3106f5b1d025

> main9.s sets _tos on entry. =A0why not just use _tos as
> the c glue code does?
>
> - erik
>
>

I'm already setting _tos on entry:
http://code.google.com/p/go/source/browse/src/pkg/runtime/plan9/386/rt0.s
TEXT _rt0_386_plan9(SB),7, $0
	MOVL	AX, _tos(SB)
=09
	// move arguments down to make room for
	// m and g at top of stack, right before Tos.
...

the hard coded addresses are here:
http://code.google.com/p/go/source/browse/src/pkg/runtime/mkasmh.sh
case "$GOOS" in
...
        plan9)
                echo '#define   get_tls(r)'
                echo '#define   g(r)    0xdfffefc0'
                echo '#define   m(r)    0xdfffefc4'

which are easy enough to modify and here:
http://code.google.com/p/go/source/browse/src/cmd/8l/pass.c
^patch(void)
...
                        if(HEADTYPE =3D=3D 2) {     // Plan 9
                                if(p->from.type =3D=3D D_INDIR+D_GS
                                && p->to.type >=3D D_AX && p->to.type <=3D =
D_DI) {
                                        p->as =3D AMOVL;
                                        p->from.type =3D D_ADDR+D_STATIC;
                                        p->from.offset +=3D 0xdfffefc0;
                                }
                        }

^dostkoff(void)
...
                        case 2: // Plan 9
                                p->as =3D AMOVL;
                                p->from.type =3D D_ADDR+D_STATIC;
                                p->from.offset =3D 0xdfffefc0;
                                p->to.type =3D D_CX;
                                break;


I am not that familiar with the linker, but maybe calling Sym*
lookup("_tos") and adding some code to to add instructions for
calculating the offset would work.

It was just easier for me to start working on a kvm vm...