runtime: handle page sizes other than 4096 properly

[davecheney]

This is a placeholder issue to ensure that platforms that don't use 4096 page sizes are
properly handled.

The specific use case is ppc64 which can have page sizes other than 4k, see
https://code.google.com/p/gofrontend/source/detail?r=986b937904fd9768c40948ece0bc233b441abb98

[davecheney]

Comment 1:

I just caught this problem in action on a ppc64le box with a 64k page size
open("/home/ubuntu/go/src/cmd/go/bootstrap.go", O_RDONLY|O_CLOEXEC) = 3
mmap(0xc208400000, 1048576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xc208400000
mmap(0xc207fb0000, 65536, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xc207fb0000
mmap(0xc000001000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x3fff87440000
munmap(0x3fff87440000, 4096)            = 0
mincore(0xc000001000, 4096, 0x516685)   = -1 EINVAL (Invalid argument)
write(2, "runtime: address space conflict:"..., 37runtime: address space conflict: map()
= 37
write(2, "0xc000001000", 120xc000001000)            = 12
write(2, ") = ", 4) = )                     = 4
write(2, "0x0", 30x0)                      = 3
write(2, "\n", 1
)                       = 1
$ getconf PAGESIZE
65536
This little tweak (as discussed offline) 
diff -r b6784924c5eb src/pkg/runtime/arch_power64le.h
--- a/src/pkg/runtime/arch_power64le.h  Wed Aug 13 18:32:54 2014 -0400
+++ b/src/pkg/runtime/arch_power64le.h  Thu Aug 14 09:56:15 2014 +0000
@@ -7,7 +7,7 @@
        BigEndian = 0,
        CacheLineSize = 64,
        RuntimeGogoBytes = 84,
-       PhysPageSize = 4096,
+       PhysPageSize = 65536,
        PCQuantum = 4,
        Int64Align = 8
 };
passed ./make.bash

[gopherbot]

Comment 2:

CL https://golang.org/cl/123520043 mentions this issue.

[davecheney]

Comment 3:

This issue was closed by revision f9fdc88.

Status changed to Fixed.