[9fans] Go Plan 9

[paulzhol@gmail.com (Pavel Zholkover)]

Thanks for the detailed explanation, I've added your patch to if that
is alright with you https://bitbucket.org/paulzhol/golang-plan9-
runtime-patches/

Pavel

On Mon, Apr 4, 2011 at 1:30 AM, Anthony Martin <ality at pbrane.org> wrote:
> Pavel Zholkover <paulzhol at gmail.com> once said:
>> I'm not sure I understand the reason 9vx will fail to reserve 768mb
>> with brk() while my Plan 9 install on kvm+qemu with 128mb or ram works
>> fine, as long as it is not written to.
>
> The reason is because 9vx gives user processes a virtual
> address space of only 256mb. ?The brk works but the
> first time we fault one of those pages past USTKTOP the
> program suicides.
>
> The first fault happens at src/pkg/runtime/mcache.c:21
> in the runtime?MCache_Alloc function.
>
> To show you what I mean, here's a formatted stack trace:
>
> term% cat y.go
> package main
>
> func main() {
> ? ? ? ?println("Hello, world.")
> }
>
> term% ./8.out
> 8.out 174: suicide: sys: trap: page fault pc=0x000021df
>
> term% db 8.out 174
> 386 binary
> page fault
> /go/src/pkg/runtime/mcache.c:21 runtime.MCache_Alloc+39/ ? ? ? ?MOVL ? ?0(AX),AX
> $c
> runtime.MCache_Alloc(sizeclass=0x1, c=0x30424000, size=0x8, zeroed=0x1)
> ? ? ? ?/go/src/pkg/runtime/mcache.c:13 called from runtime.mallocgc+db
> ? ? ? ?/go/src/pkg/runtime/malloc.goc:62
> runtime.mallocgc(size=0x8, zeroed=0x1, flag=0x0, dogc=0x0)
> ? ? ? ?/go/src/pkg/runtime/malloc.goc:40 called from runtime.malloc+41
> ? ? ? ?/go/src/pkg/runtime/malloc.goc:115
> runtime.malloc(size=0x1)
> ? ? ? ?/go/src/pkg/runtime/malloc.goc:113 called from runtime.mallocinit+e9
> ? ? ? ?/go/src/pkg/runtime/malloc.goc:319
> runtime.mallocinit()
> ? ? ? ?/go/src/pkg/runtime/malloc.goc:237 called from runtime.schedinit+39
> ? ? ? ?/go/src/pkg/runtime/proc.c:122
> runtime.schedinit()
> ? ? ? ?/go/src/pkg/runtime/proc.c:113 called from _rt0_386+b3
> ? ? ? ?/go/src/pkg/runtime/386/asm.s:78
> _rt0_386()
> ? ? ? ?/go/src/pkg/runtime/386/asm.s:12 called from 1
>
>
> Cheers,
> ?Anthony
>
>